Latest open access articles published in International Journal of Computational Methods and Experimental Measurements at https://www.acadlore.com/journals/IJCMEM https://www.acadlore.com/journals/IJCMEM Acadlore en Creative Commons Attribution(CC - BY) IJCMEM support@acadlore.com https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140105 Reliable predictions of high temperature events are of great significance to enhance urban resilience in arid regions, especially for cities such as Baghdad which lie at the southern end of the jet stream with summer temperatures frequently exceeding 50 °C. However, linear models such as the autoregressive integrated moving average (ARIMA) are limited; they have difficulties in modeling nonlinear patterns. Deep learning techniques (e.g., long short-term memory (LSTM) networks) pose yet another difficulty as they are sensitive to overfitting and they demand large amounts of data to be trained on. In this paper, introduce a hybrid ARIMA-LSTM based on residual decomposition is proposed. This method takes the best of statistical and deep learning methods. The time series of temperature is decomposed into two parts: the linear part which is modeled by ARIMA and the residual nonlinear part which is modeled by LSTM. Based on the daily temperature information during 2000–2023, this hybrid model outperformed the ARIMA and LSTM models individually. For example, it obtained a mean absolute error (MAE) of 1.56 °C, root mean square error (RMSE) of 2.11 °C and $R^2$ of 0.92. Note that the model remained highly accurate during extreme heat events over 45 °C (producing an MAE of 2.01 °C). These findings point to the model’s potential for early warning and climate adaptation, particularly in dry urban districts confronted with escalating heat stress. 03-24-2026 <![CDATA[ <p>Reliable predictions of high temperature events are of great significance to enhance urban resilience in arid regions, especially for cities such as Baghdad which lie at the southern end of the jet stream with summer temperatures frequently exceeding 50 °C. However, linear models such as the autoregressive integrated moving average (ARIMA) are limited; they have difficulties in modeling nonlinear patterns. Deep learning techniques (e.g., long short-term memory (LSTM) networks) pose yet another difficulty as they are sensitive to overfitting and they demand large amounts of data to be trained on. In this paper, introduce a hybrid ARIMA-LSTM based on residual decomposition is proposed. This method takes the best of statistical and deep learning methods. The time series of temperature is decomposed into two parts: the linear part which is modeled by ARIMA and the residual nonlinear part which is modeled by LSTM. Based on the daily temperature information during 2000–2023, this hybrid model outperformed the ARIMA and LSTM models individually. For example, it obtained a mean absolute error (MAE) of 1.56 °C, root mean square error (RMSE) of 2.11 °C and $R^2$ of 0.92. Note that the model remained highly accurate during extreme heat events over 45 °C (producing an MAE of 2.01 °C). These findings point to the model’s potential for early warning and climate adaptation, particularly in dry urban districts confronted with escalating heat stress.</p> ]]> Improving Extreme Heatwave Prediction in Baghdad Using a Novel Hybrid ARIMA-LSTM Framework with Residual Decomposition adwea naji atewi baneen khalid imran huda abdulrazzaq mohammad noora jamal ali doi: 10.56578/ijcmem140105 International Journal of Computational Methods and Experimental Measurements 03-24-2026 International Journal of Computational Methods and Experimental Measurements 03-24-2026 2026 14 1 Article 81 10.56578/ijcmem140105 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140105 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140104 This study examines the effects of viscous dissipation, Joule heating, and coupled heat transfer on dissipative ternary nanofluid flow over a permeable surface. The ternary nanofluid is composed of Al$_2$O$_3$, SiO$_2$, and TiO$_2$ nanoparticles dispersed in water as the base fluid. By introducing suitable similarity transformations, the governing partial differential equations are reduced to a coupled system of ordinary differential equations. The thermal field is analyzed for both prescribed surface temperature (PST) and prescribed heat flux (PHF) conditions, while a temperature-dependent heat source/sink term is incorporated to maintain energy balance within the fluid domain. The resulting energy equation is treated analytically with the aid of Kummer’s function and Laguerre polynomial techniques. The effects of the main controlling parameters, including the inverse Darcy number, magnetic parameter, viscosity-ratio parameter, and radiation parameter, are discussed with the support of graphical results. It is found that an increase in the magnetic parameter reduces the velocity by about 12% and raises the temperature by nearly 18%. These findings provide useful guidance for the design and thermal optimization of engineering systems involving complex nanofluids in porous media, including polymer extrusion and automotive cooling applications. 03-23-2026 <![CDATA[ <p>This study examines the effects of viscous dissipation, Joule heating, and coupled heat transfer on dissipative ternary nanofluid flow over a permeable surface. The ternary nanofluid is composed of Al$_2$O$_3$, SiO$_2$, and TiO$_2$ nanoparticles dispersed in water as the base fluid. By introducing suitable similarity transformations, the governing partial differential equations are reduced to a coupled system of ordinary differential equations. The thermal field is analyzed for both prescribed surface temperature (PST) and prescribed heat flux (PHF) conditions, while a temperature-dependent heat source/sink term is incorporated to maintain energy balance within the fluid domain. The resulting energy equation is treated analytically with the aid of Kummer’s function and Laguerre polynomial techniques. The effects of the main controlling parameters, including the inverse Darcy number, magnetic parameter, viscosity-ratio parameter, and radiation parameter, are discussed with the support of graphical results. It is found that an increase in the magnetic parameter reduces the velocity by about 12% and raises the temperature by nearly 18%. These findings provide useful guidance for the design and thermal optimization of engineering systems involving complex nanofluids in porous media, including polymer extrusion and automotive cooling applications.</p> ]]> Joule Heating and Viscosity-Ratio Effects on Dissipative Ternary Nanofluid Flow over a Permeable Surface sudha mahanthesh sachhin kenchappa nagegowda ulavathi shettar mahabaleshwar laura milena pérez giulio lorenzini doi: 10.56578/ijcmem140104 International Journal of Computational Methods and Experimental Measurements 03-23-2026 International Journal of Computational Methods and Experimental Measurements 03-23-2026 2026 14 1 Article 57 10.56578/ijcmem140104 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140104 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140103 Energy-efficient path planning for multi-Unmanned Aerial Vehicle (UAV) data-collection missions requires balancing trajectory efficiency, energy consumption, and workload distribution among UAVs. This study presents a controlled computational evaluation of three routing paradigms: random assignment, Greedy nearest-neighbor routing, and Greedy + K-means clustering. The evaluation is conducted using a mission-level energy model that incorporates propulsion energy and mission-phase components, including take-off, hovering, sensing, communication, and landing. Simulation experiments were performed using fleets of 1–10 UAVs serving 100 Points-of-Interest (PoIs) under two spatial deployment scenarios: a structured grid layout and a spatially heterogeneous random layout. Each configuration was executed over 20 independent episodes to ensure statistical robustness. The results demonstrate that routing structure significantly influences geometric mission efficiency. In the propulsion-dominated regime (U $\geq$ 5 under random PoI layouts), Greedy + K-means clustering reduces mission travel distance by approximately 11.6–24.5% compared with Greedy routing, corresponding to an energy reduction of approximately 4.6–10.5%. In contrast, under the phase-dominated regime, where fixed mission-phase energy dominates the total energy budget, performance differences between routing strategies remain below 5%. Statistical analysis further confirms large practical differences in geometric performance across algorithms ($\eta^2$ $>$ 0.86). These findings indicate that routing strategy selection should depend on mission scale and spatial characteristics rather than assuming universal optimality. Greedy routing performs effectively in small or spatially structured deployments, whereas Greedy + K-means clustering provides greater robustness and scalability in larger or spatially heterogeneous missions. 03-12-2026 <![CDATA[ <p>Energy-efficient path planning for multi-Unmanned Aerial Vehicle (UAV) data-collection missions requires balancing trajectory efficiency, energy consumption, and workload distribution among UAVs. This study presents a controlled computational evaluation of three routing paradigms: random assignment, Greedy nearest-neighbor routing, and Greedy + K-means clustering. The evaluation is conducted using a mission-level energy model that incorporates propulsion energy and mission-phase components, including take-off, hovering, sensing, communication, and landing. Simulation experiments were performed using fleets of 1–10 UAVs serving 100 Points-of-Interest (PoIs) under two spatial deployment scenarios: a structured grid layout and a spatially heterogeneous random layout. Each configuration was executed over 20 independent episodes to ensure statistical robustness. The results demonstrate that routing structure significantly influences geometric mission efficiency. In the propulsion-dominated regime (U $\geq$ 5 under random PoI layouts), Greedy + K-means clustering reduces mission travel distance by approximately 11.6–24.5% compared with Greedy routing, corresponding to an energy reduction of approximately 4.6–10.5%. In contrast, under the phase-dominated regime, where fixed mission-phase energy dominates the total energy budget, performance differences between routing strategies remain below 5%. Statistical analysis further confirms large practical differences in geometric performance across algorithms ($\eta^2$ $>$ 0.86). These findings indicate that routing strategy selection should depend on mission scale and spatial characteristics rather than assuming universal optimality. Greedy routing performs effectively in small or spatially structured deployments, whereas Greedy + K-means clustering provides greater robustness and scalability in larger or spatially heterogeneous missions.</p> ]]> Energy-Efficient Multi-Unmanned Aerial Vehicle Path Planning: A Comparative Study of Random, Greedy, and Clustering Strategies muhammad anif selo sulistyo i wayan mustika doi: 10.56578/ijcmem140103 International Journal of Computational Methods and Experimental Measurements 03-12-2026 International Journal of Computational Methods and Experimental Measurements 03-12-2026 2026 14 1 Article 38 10.56578/ijcmem140103 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140103 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140102 Logic-based machine learning models such as the Tsetlin Machine (TM) have recently gained attention for their energy efficiency and inherent interpretability. However, existing TM-based architectures remain limited in their ability to perform hierarchical feature learning, adapt dynamically to task complexity, and process temporal data efficiently. This paper proposes the Adaptive Logic Learning Architecture (ALLA), a novel hierarchical and energy-aware logic learning framework that addresses these limitations through adaptive clause networks (ACNs), multi-layer logical composition, and TLUs. ALLA enables dynamic clause growth and pruning, supports hierarchical abstraction, and integrates temporal reasoning within a unified propositional logic framework. Experimental results across image classification and sequential recognition tasks show that ALLA improves accuracy over conventional TM models while maintaining substantially lower energy consumption than deep neural network baselines. Hardware synthesis results further confirm the suitability of ALLA for low-power and edge-intelligent systems. 03-05-2026 <![CDATA[ Logic-based machine learning models such as the Tsetlin Machine (TM) have recently gained attention for their energy efficiency and inherent interpretability. However, existing TM-based architectures remain limited in their ability to perform hierarchical feature learning, adapt dynamically to task complexity, and process temporal data efficiently. This paper proposes the Adaptive Logic Learning Architecture (ALLA), a novel hierarchical and energy-aware logic learning framework that addresses these limitations through adaptive clause networks (ACNs), multi-layer logical composition, and TLUs. ALLA enables dynamic clause growth and pruning, supports hierarchical abstraction, and integrates temporal reasoning within a unified propositional logic framework. Experimental results across image classification and sequential recognition tasks show that ALLA improves accuracy over conventional TM models while maintaining substantially lower energy consumption than deep neural network baselines. Hardware synthesis results further confirm the suitability of ALLA for low-power and edge-intelligent systems. ]]> Adaptive Logic Learning Architecture: A Hierarchical Framework for Energy-Efficient and Interpretable AI Systems ibrahim haddadi doi: 10.56578/ijcmem140102 International Journal of Computational Methods and Experimental Measurements 03-05-2026 International Journal of Computational Methods and Experimental Measurements 03-05-2026 2026 14 1 Article 17 10.56578/ijcmem140102 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140102 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140101 Cooking-related fires and combustible-gas leaks remain recurring domestic hazards, while lights and ventilation fans are often left running in empty rooms. This paper presents the design and experimental validation of a low-cost retrofit IoT node that integrates occupancy-aware actuation with early smoke and gas monitoring under a safety-first policy. An Arduino UNO executes time-critical sensing and relay control, and an ESP8266 provides Wi-Fi connectivity and a lightweight smartphone interface. Occupancy is inferred using a passive infrared (PIR) sensor to gate a lamp and fan, while an MQ-2 module monitors smoke and combustible gases. The control logic is implemented as an event-driven state machine that prioritises safety events, enforces minimum on and off timing to suppress relay chattering, and stabilises the gas channel using clean-air baseline normalisation (R/R0) with hysteresis. Bench verification confirmed I/O mapping and electrical isolation via an opto-isolated relay stage, and repeated switching did not reveal relay instability under the prototype loads. Scenario trials in a two-zone mock-up demonstrated reliable manual overrides, motion-triggered actuation without oscillation, and consistent alert generation during staged smoke exposures. The results support feasibility for incremental residential retrofits and identify deployment priorities, including sensor drift management, power integrity, and installation practice. 03-05-2026 <![CDATA[ Cooking-related fires and combustible-gas leaks remain recurring domestic hazards, while lights and ventilation fans are often left running in empty rooms. This paper presents the design and experimental validation of a low-cost retrofit IoT node that integrates occupancy-aware actuation with early smoke and gas monitoring under a safety-first policy. An Arduino UNO executes time-critical sensing and relay control, and an ESP8266 provides Wi-Fi connectivity and a lightweight smartphone interface. Occupancy is inferred using a passive infrared (PIR) sensor to gate a lamp and fan, while an MQ-2 module monitors smoke and combustible gases. The control logic is implemented as an event-driven state machine that prioritises safety events, enforces minimum on and off timing to suppress relay chattering, and stabilises the gas channel using clean-air baseline normalisation (R/R0) with hysteresis. Bench verification confirmed I/O mapping and electrical isolation via an opto-isolated relay stage, and repeated switching did not reveal relay instability under the prototype loads. Scenario trials in a two-zone mock-up demonstrated reliable manual overrides, motion-triggered actuation without oscillation, and consistent alert generation during staged smoke exposures. The results support feasibility for incremental residential retrofits and identify deployment priorities, including sensor drift management, power integrity, and installation practice. ]]> Low-Cost IoT Smart-Home Node for Motion and Gas Leakage Monitoring with Arduino and ESP8266 jamil abedalrahim jamil alsayaydeh irianto aqeel al-hilali haslinah binti mohd nasir hatem t m duhair safarudin gazali herawan doi: 10.56578/ijcmem140101 International Journal of Computational Methods and Experimental Measurements 03-05-2026 International Journal of Computational Methods and Experimental Measurements 03-05-2026 2026 14 1 Article 1 10.56578/ijcmem140101 https://www.acadlore.com/article/IJCMEM/2026_14_1/ijcmem140101 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130420 The efficiency of the multi-effect distillation (MED) system is highly influenced by its operational parameters during operation. Similarly, the efficiency of the compact MED is significantly affected by its operating conditions. One of the operating parameters of MED is the pressure applied to each component. In this study, a compact MED experimental test was conducted using sub-atmospheric pressure in a freshwater tank. The freshwater tanks are designed to hold the freshwater produced by the compact MED. The installation of the freshwater tank is designed to connect to a vacuum pump to create sub-atmospheric conditions inside the freshwater tank. The highest experimental results show that under a freshwater tank pressure of 70 kPa, 368.5 mL of freshwater can be produced from 500 mL of seawater tested in a boiler at a pressure of 151.3 kPa. Based on these experimental results, sub-atmospheric pressure inside the freshwater tank can influence the output of the compact MED freshwater. 12-30-2025 <![CDATA[ The efficiency of the multi-effect distillation (MED) system is highly influenced by its operational parameters during operation. Similarly, the efficiency of the compact MED is significantly affected by its operating conditions. One of the operating parameters of MED is the pressure applied to each component. In this study, a compact MED experimental test was conducted using sub-atmospheric pressure in a freshwater tank. The freshwater tanks are designed to hold the freshwater produced by the compact MED. The installation of the freshwater tank is designed to connect to a vacuum pump to create sub-atmospheric conditions inside the freshwater tank. The highest experimental results show that under a freshwater tank pressure of 70 kPa, 368.5 mL of freshwater can be produced from 500 mL of seawater tested in a boiler at a pressure of 151.3 kPa. Based on these experimental results, sub-atmospheric pressure inside the freshwater tank can influence the output of the compact MED freshwater. ]]> Sub-Atmospheric Assisted Freshwater Tank in a Compact Multi-Effect Distillation System: Experimental Performance and Thermodynamic Evaluation engkos koswara uyung gatot s. dinata harun sujadi slamet riyadi dwi prasetyo doi: 10.56578/ijcmem130420 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 1048 10.56578/ijcmem130420 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130420 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130419 External dynamic circumstances, especially vertical vibrations brought on by uneven road surfaces and engine activity, have a major impact on a vehicle’s radiator performance. To increase cooling effectiveness and improve thermal management in automobiles, it is essential to comprehend how these vibrations affect heat transmission. This paper proposes using methods to enhance vibration-enhanced heat transfer and increase volumetric flows on a finned-tube car radiator. The radiator’s thermal performance is improved through heat dissipation. The experiment was conducted at volumetric flows (0.5, 0.75, 1, and 1.25 liters per minute (LPM)) and frequencies (0, 5, 10, and 15 Hz). In terms of enhancing vibration-enhanced thermal performance, this study varies from other experimental investigations, particularly with regard to the frequency range employed and volumetric flow. We investigated the impact of vibration coinciding with volumetric flow and pellet behavior under operating settings more similar to those in which cooling systems function. This topic has not been fully explored before and does not constitute redundancy; instead, it solves limits by experimentally examining how vibration and realistic operating circumstances work together to improve thermal performance. The highest increase in Nusselt number enhancement was 23.4% observed on the water side, while the highest enhancement was 12.99% observed on the air side. Increased vibration led to increased heat flow, reaching its maximum 773.85 W/m2 at frequency 15 Hz and volumetric flow 1.25 LPM. The vibrational disturbance further enhanced heat exchange between adjacent surfaces. 12-30-2025 <![CDATA[ <p>External dynamic circumstances, especially vertical vibrations brought on by uneven road surfaces and engine activity, have a major impact on a vehicle’s radiator performance. To increase cooling effectiveness and improve thermal management in automobiles, it is essential to comprehend how these vibrations affect heat transmission. This paper proposes using methods to enhance vibration-enhanced heat transfer and increase volumetric flows on a finned-tube car radiator. The radiator’s thermal performance is improved through heat dissipation. The experiment was conducted at volumetric flows (0.5, 0.75, 1, and 1.25 liters per minute (LPM)) and frequencies (0, 5, 10, and 15 Hz). In terms of enhancing vibration-enhanced thermal performance, this study varies from other experimental investigations, particularly with regard to the frequency range employed and volumetric flow. We investigated the impact of vibration coinciding with volumetric flow and pellet behavior under operating settings more similar to those in which cooling systems function. This topic has not been fully explored before and does not constitute redundancy; instead, it solves limits by experimentally examining how vibration and realistic operating circumstances work together to improve thermal performance. The highest increase in Nusselt number enhancement was 23.4% observed on the water side, while the highest enhancement was 12.99% observed on the air side. Increased vibration led to increased heat flow, reaching its maximum 773.85 W/m² at frequency 15 Hz and volumetric flow 1.25 LPM. The vibrational disturbance further enhanced heat exchange between adjacent surfaces.</p> ]]> Experimental Study of Effect Vertical Vibration on Heat Transfer of Vehicle Radiator noor mandeel agag yasir hassan ali qais abid yousif doi: 10.56578//ijcmem130419 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 1032 10.56578//ijcmem130419 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130419 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130418 Liquid level control plays a crucial role in process industries, where accurate and stable regulation is required to ensure operational safety and process efficiency. In practice, nonlinear tank dynamics and wide operating ranges often degrade the performance of conventional proportional-integral-derivative (PID)-based control strategies, leading to excessive overshoot, oscillations, and prolonged settling times. Although various advanced control techniques have been proposed, many of them rely on complex tuning procedures or heuristic design, which limits their practical applicability. This paper proposes a mass-balance-based liquid level control strategy that directly exploits the physical relationship between inflow, outflow, and liquid level. The proposed method introduces a mode-switching mechanism that distinguishes between transient and steady-state operating conditions. During transient operation, the control valve is driven to its saturation limits to accelerate level correction, while steady-state regulation is achieved by balancing inflow and outflow to maintain mass equilibrium. Unlike conventional PID controllers, the proposed approach does not require parameter tuning, system identification, or optimization procedures. Simulation studies are conducted on nonlinear tank systems to evaluate the effectiveness of the proposed strategy. The results demonstrate that the proposed method achieves fast setpoint tracking with zero overshoot and reduced settling time compared with conventional proportional (P), proportional-integral (PI), and PID, and cascade control schemes. Quantitative performance comparisons further confirm the robustness and practical advantages of the proposed control strategy for nonlinear liquid level control applications. 12-30-2025 <![CDATA[ Liquid level control plays a crucial role in process industries, where accurate and stable regulation is required to ensure operational safety and process efficiency. In practice, nonlinear tank dynamics and wide operating ranges often degrade the performance of conventional proportional-integral-derivative (PID)-based control strategies, leading to excessive overshoot, oscillations, and prolonged settling times. Although various advanced control techniques have been proposed, many of them rely on complex tuning procedures or heuristic design, which limits their practical applicability. This paper proposes a mass-balance-based liquid level control strategy that directly exploits the physical relationship between inflow, outflow, and liquid level. The proposed method introduces a mode-switching mechanism that distinguishes between transient and steady-state operating conditions. During transient operation, the control valve is driven to its saturation limits to accelerate level correction, while steady-state regulation is achieved by balancing inflow and outflow to maintain mass equilibrium. Unlike conventional PID controllers, the proposed approach does not require parameter tuning, system identification, or optimization procedures. Simulation studies are conducted on nonlinear tank systems to evaluate the effectiveness of the proposed strategy. The results demonstrate that the proposed method achieves fast setpoint tracking with zero overshoot and reduced settling time compared with conventional proportional (P), proportional-integral (PI), and PID, and cascade control schemes. Quantitative performance comparisons further confirm the robustness and practical advantages of the proposed control strategy for nonlinear liquid level control applications. ]]> Enhancing Liquid Level Control Performance Using Mass Balance Techniques in Linear and Nonlinear Tanks natinan kuttanan wongsakorn wongsaroj thaksin sangsuwan natee thong-un doi: 10.56578/ijcmem130418 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 1020 10.56578/ijcmem130418 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130418 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130417 This study investigates whole-body vibration (WBV) exposure in commuters on Iraqi roads. Measurement of vertical, lateral and longitudinal acceleration was obtained on urban arterials, rural two-lane roads and intercity highways using a low-cost measurement setup that incorporates an MPU6050 accelerometer and ESP32 microcontroller. Data was analyzed in accordance with ISO 2631-1, i.e. frequency-weighted root mean square (RMS) acceleration, vibration dose values (VDV) or power spectral density analysis. The results show that vertical vibration (z-axis) predominates in WBV, with maximum energy occurring within the 3–6 Hz frequency range, which is known to correspond to the most responsive frequency range of the human body. The International Roughness Index (IRI), a measure of pavement texture, was highly associated with RMS (r = 0.66), with speed having an additional enhancing influence. Cars and SUVs on intercity highways stayed in “comfort” or “light comfort” zones, whereas heavy trucks on rural roads often encountered “uncomfortable” levels, with VDV up to 16.9 m/s$^{1.75}$. These results reveal a growing need for pavement rehabilitation of the Iraqi arterial and rural road networks, better enforcement of axle-load limits and the adoption of WBV monitoring in sensor-based management of road infrastructure. The research outcomes can serve as a useful reference for enhancing transport and occupational health protection policy making in Iraq. 12-30-2025 <![CDATA[ <p>This study investigates whole-body vibration (WBV) exposure in commuters on Iraqi roads. Measurement of vertical, lateral and longitudinal acceleration was obtained on urban arterials, rural two-lane roads and intercity highways using a low-cost measurement setup that incorporates an MPU6050 accelerometer and ESP32 microcontroller. Data was analyzed in accordance with ISO 2631-1, i.e. frequency-weighted root mean square (RMS) acceleration, vibration dose values (VDV) or power spectral density analysis. The results show that vertical vibration (z-axis) predominates in WBV, with maximum energy occurring within the 3–6 Hz frequency range, which is known to correspond to the most responsive frequency range of the human body. The International Roughness Index (IRI), a measure of pavement texture, was highly associated with RMS (r = 0.66), with speed having an additional enhancing influence. Cars and SUVs on intercity highways stayed in “comfort” or “light comfort” zones, whereas heavy trucks on rural roads often encountered “uncomfortable” levels, with VDV up to 16.9 m/s$^{1.75}$. These results reveal a growing need for pavement rehabilitation of the Iraqi arterial and rural road networks, better enforcement of axle-load limits and the adoption of WBV monitoring in sensor-based management of road infrastructure. The research outcomes can serve as a useful reference for enhancing transport and occupational health protection policy making in Iraq.</p> ]]> Whole-Body Vibration in Vehicles on Iraqi Roads ammar adil hussein haider fawzi mahmood doi: 10.56578/ijcmem130417 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 1006 10.56578/ijcmem130417 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130417 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130416 A ramjet nozzle was designed for supersonic operating conditions and evaluated numerically using Ansys Fluent 16.1 over a range of chamber-to-ambient pressure ratios. The nozzle geometry was generated to achieve smooth, shock-free expansion under supersonic outflow conditions using the characteristic curve method at a specific nozzle chamber pressure and temperature using Matrix Laboratory (MATLAB) and then validated by comparing the numerical predictions with available experimental data. The results show that a pressure ratio of 57 provides the highest thrust coefficient (TC), while lower ratios lead to over-expanded flow and higher ratios to under-expansion with increased shock losses. Contours of pressure, temperature, and Mach number confirm the expected supersonic flow structure and demonstrate that the nozzle achieves optimum performance under the identified conditions. 12-30-2025 <![CDATA[ A ramjet nozzle was designed for supersonic operating conditions and evaluated numerically using Ansys Fluent 16.1 over a range of chamber-to-ambient pressure ratios. The nozzle geometry was generated to achieve smooth, shock-free expansion under supersonic outflow conditions using the characteristic curve method at a specific nozzle chamber pressure and temperature using Matrix Laboratory (MATLAB) and then validated by comparing the numerical predictions with available experimental data. The results show that a pressure ratio of 57 provides the highest thrust coefficient (TC), while lower ratios lead to over-expanded flow and higher ratios to under-expansion with increased shock losses. Contours of pressure, temperature, and Mach number confirm the expected supersonic flow structure and demonstrate that the nozzle achieves optimum performance under the identified conditions. ]]> Numerical Modeling of Supersonic Flow Through a Ramjet Nozzle Using Ansys Fluent mustafa abdulsalam mustafa atheer raheem abdullah mohammed mousa al-azzawi doi: 10.56578/ijcmem130416 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 993 10.56578/ijcmem130416 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130416 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130415 The increasing adoption of electric vehicles with fast-charging capability has intensified thermal challenges in power cables, potentially leading to localized overheating and reduced system reliability and service life. To address this issue, an integrated framework combining experimental measurement and data-driven analysis was developed to identify and predict thermal behaviour in critical electrical components of electric vehicles. A laboratory-scale electric vehicle powertrain was constructed to replicate representative operating conditions. Infrared thermography was employed together with synchronized electrical measurements to capture the coupled electrical–thermal response of the system. The powertrain was tested under variable mechanical loads ranging from 0% to over 80% and under constant-current operation at 15 A for 30 minutes. Passive thermal management using phase change materials, specifically beeswax and paraffin, was evaluated to assess its effectiveness in mitigating temperature rise. In addition, a lightweight artificial neural network (ANN) model was developed to predict the temperatures of thermally critical components. Thermographic results showed that thermal stress was spatially concentrated at specific interfaces. At maximum load, the temperatures of the power cable downstream of the main switch, the motor cable, and the connector reached 41.2 ℃, 39.7 ℃, and 47 ℃, respectively. Analysis of battery charging behaviour revealed a strong correlation between battery temperature and charging current, with a correlation coefficient of 0.95. When phase change materials were applied, the battery temperature rise was reduced to approximately 35.2–35.5 ℃, compared with 36.7 ℃ in the absence of phase change materials, and voltage stability was improved. The ANN demonstrated high predictive accuracy, with R² values of 0.978 for main switch temperature, 0.969 for connector temperature, and 0.962 for motor cable temperature, corresponding to prediction errors within ±2.5 ℃ across all load conditions. These findings indicate that an integrated experimental and predictive diagnostic approach can effectively support thermal management and early risk identification in high-current electric vehicle power cable systems. 12-30-2025 <![CDATA[ <p>The increasing adoption of electric vehicles with fast-charging capability has intensified thermal challenges in power cables, potentially leading to localized overheating and reduced system reliability and service life. To address this issue, an integrated framework combining experimental measurement and data-driven analysis was developed to identify and predict thermal behaviour in critical electrical components of electric vehicles. A laboratory-scale electric vehicle powertrain was constructed to replicate representative operating conditions. Infrared thermography was employed together with synchronized electrical measurements to capture the coupled electrical–thermal response of the system. The powertrain was tested under variable mechanical loads ranging from 0% to over 80% and under constant-current operation at 15 A for 30 minutes. Passive thermal management using phase change materials, specifically beeswax and paraffin, was evaluated to assess its effectiveness in mitigating temperature rise. In addition, a lightweight artificial neural network (ANN) model was developed to predict the temperatures of thermally critical components. Thermographic results showed that thermal stress was spatially concentrated at specific interfaces. At maximum load, the temperatures of the power cable downstream of the main switch, the motor cable, and the connector reached 41.2 ℃, 39.7 ℃, and 47 ℃, respectively. Analysis of battery charging behaviour revealed a strong correlation between battery temperature and charging current, with a correlation coefficient of 0.95. When phase change materials were applied, the battery temperature rise was reduced to approximately 35.2–35.5 ℃, compared with 36.7 ℃ in the absence of phase change materials, and voltage stability was improved. The ANN demonstrated high predictive accuracy, with R² values of 0.978 for main switch temperature, 0.969 for connector temperature, and 0.962 for motor cable temperature, corresponding to prediction errors within ±2.5 ℃ across all load conditions. These findings indicate that an integrated experimental and predictive diagnostic approach can effectively support thermal management and early risk identification in high-current electric vehicle power cable systems.</p> ]]> A Data-Driven and Experimental Approach to Thermal Risk Assessment in High-Current Electric Vehicle Power Cable Systems safarudin gazali herawan azqy nur farenzy saputra sharon yemima bangkit pramesta yulianto doi: 10.56578/ijcmem130415 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 971 10.56578/ijcmem130415 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130415 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130414 Mobile ad hoc networks (MANETs) are inherently susceptible to malicious packet-dropping attacks, including black holes, gray holes and selective forwarding attacks that greatly decrease the reliability and performance of MANETs. Current solutions for detecting malicious attacks have large false-positive rates because they often confuse an intended malicious drop with an unintended loss caused by limited resources, traffic congestion and/or the impairment of wireless channels. In addition, current solutions can be vulnerable to acknowledgment (ACK) forgery attacks and consume considerable amounts of energy in continuously monitoring packets. The authors present a comprehensive four-phase framework that synergistically combines route qualification based on available resources, password-based mutual authentication using chaotic map Diffie Hellman password authenticated key exchange (CMDH-PAKE), authenticated digested ACKs based on counters and selectively activating promiscuous monitors to accurately detect and mitigate malicious packet-dropping attacks in MANETs at low power. The authors’ solution identifies and excludes honest-but-constrained nodes during route discovery by estimating buffer congestion using exponentially weighted moving average (EWMA) and modeling energy feasibility, thus reducing false positives by up to 73%. Binding keys between cryptographic sessions reduces the potential for ACK forgery and impersonation attacks, and aggregated window-based ACKs reduce energy use by 85%, relative to per-packet ACKs. Selectively activating monitors on demand using only cryptographic evidence of anomalies minimizes the energy used while still maintaining a high level of detection accuracy (above 96%). Simulation results using Network Simulator 3 (NS-3) indicate that the authors’ solution has a higher packet delivery ratio (94.2%), shorter end-to-end delay (127 ms), and much lower false-positive rate (3.1%) than other approaches; in addition, the authors’ solution uses about 42% less energy than always-on monitoring approaches. 12-30-2025 <![CDATA[ <p>Mobile ad hoc networks (MANETs) are inherently susceptible to malicious packet-dropping attacks, including black holes, gray holes and selective forwarding attacks that greatly decrease the reliability and performance of MANETs. Current solutions for detecting malicious attacks have large false-positive rates because they often confuse an intended malicious drop with an unintended loss caused by limited resources, traffic congestion and/or the impairment of wireless channels. In addition, current solutions can be vulnerable to acknowledgment (ACK) forgery attacks and consume considerable amounts of energy in continuously monitoring packets. The authors present a comprehensive four-phase framework that synergistically combines route qualification based on available resources, password-based mutual authentication using chaotic map Diffie Hellman password authenticated key exchange (CMDH-PAKE), authenticated digested ACKs based on counters and selectively activating promiscuous monitors to accurately detect and mitigate malicious packet-dropping attacks in MANETs at low power. The authors’ solution identifies and excludes honest-but-constrained nodes during route discovery by estimating buffer congestion using exponentially weighted moving average (EWMA) and modeling energy feasibility, thus reducing false positives by up to 73%. Binding keys between cryptographic sessions reduces the potential for ACK forgery and impersonation attacks, and aggregated window-based ACKs reduce energy use by 85%, relative to per-packet ACKs. Selectively activating monitors on demand using only cryptographic evidence of anomalies minimizes the energy used while still maintaining a high level of detection accuracy (above 96%). Simulation results using Network Simulator 3 (NS-3) indicate that the authors’ solution has a higher packet delivery ratio (94.2%), shorter end-to-end delay (127 ms), and much lower false-positive rate (3.1%) than other approaches; in addition, the authors’ solution uses about 42% less energy than always-on monitoring approaches.</p> ]]> A Multi-Phase Framework for Detection and Mitigation of Intentional Packet Dropping Attacks in Mobile Ad Hoc Networks polu srinivasa reddy arshad ahmad khan mohammad doi: 10.56578/ijcmem130414 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 954 10.56578/ijcmem130414 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130414 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130413 Electricity theft is a major contributor to non-technical losses (NTL) in distribution networks, causing substantial revenue losses and degrading grid reliability. Conventional approaches such as periodic inspections and smart-meter-only monitoring often fail to detect sophisticated theft behaviors, including meter tampering and illegal line tapping. This paper presents a low-cost IoT-cloud dual-meter system for real-time electricity theft detection and response. The proposed design measures energy at two points: (i) the incoming supply line and (ii) the consumer-side meter output. An embedded controller acquires both streams and uploads the readings to a cloud platform, where a discrepancy-based detection module continuously compares delivered and metered energy within a configurable tolerance to account for normal losses and sensor uncertainty. When persistent abnormal discrepancies are identified, the system issues immediate alerts to utility operators and can optionally trigger a local relay to disconnect the load. A prototype implementation was evaluated under controlled scenarios that emulate normal operation and theft conditions. The system achieved approximately 95% detection accuracy, maintained false alarms below 5%, and detected small theft levels down to about 10 W in the test setup. The bill of materials indicates an estimated unit cost of approximately USD 30–50, supporting scalable deployment in cost-sensitive environments. 12-30-2025 <![CDATA[ <p>Electricity theft is a major contributor to non-technical losses (NTL) in distribution networks, causing substantial revenue losses and degrading grid reliability. Conventional approaches such as periodic inspections and smart-meter-only monitoring often fail to detect sophisticated theft behaviors, including meter tampering and illegal line tapping. This paper presents a low-cost IoT-cloud dual-meter system for real-time electricity theft detection and response. The proposed design measures energy at two points: (i) the incoming supply line and (ii) the consumer-side meter output. An embedded controller acquires both streams and uploads the readings to a cloud platform, where a discrepancy-based detection module continuously compares delivered and metered energy within a configurable tolerance to account for normal losses and sensor uncertainty. When persistent abnormal discrepancies are identified, the system issues immediate alerts to utility operators and can optionally trigger a local relay to disconnect the load. A prototype implementation was evaluated under controlled scenarios that emulate normal operation and theft conditions. The system achieved approximately 95% detection accuracy, maintained false alarms below 5%, and detected small theft levels down to about 10 W in the test setup. The bill of materials indicates an estimated unit cost of approximately USD 30–50, supporting scalable deployment in cost-sensitive environments.</p> ]]> Low-Cost IoT-Cloud Dual-Meter System for Real-Time Electricity Theft Detection jamil abedalrahim jamil alsayaydeh mohd faizal yusof ahmed hussein ahmed rostam affendi bin hamzah safarudin gazali herawan doi: 10.56578/ijcmem130413 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 928 10.56578/ijcmem130413 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130413 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130412 Increasing energy requirements in hot regions highlight the need for sustainable thermal management technologies. A promising passive cooling solution is Earth-Air Heat Exchanger (EAHE) that use the relatively stable temperature of the subsurface soil to pre-cool air supplied to indoor spaces. This study investigates the thermal and hydraulic performance of an EAHE coupled to a greenhouse in severe summer conditions in Nasiriyah city, southern Iraq, experimentally. The system was designed to evaluate its effectiveness in moderating ambient temperature extremes and reducing mechanical cooling energy requirements. Experimental results during July–October showed that the EAHE outlet air temperature stayed between 31 and 38°C despite ambient temperature exceeding 50°C, indicating a stable thermal response of the buried exchanger. The greenhouse air temperature was maintained at 34–40°C during peak daytime hours and decreased to about 29–33°C during the remaining operating periods, confirming improved internal thermal conditions. The thermal effectiveness ($\varepsilon$) ranged from 0.68 to 0.75, and the average temperature drop ($\Delta{T}$) was above 13°C throughout the test period. Furthermore, pressure drop and fan power increased with airflow velocity, consistent with a turbulent flow regime. The EAHE delivered 2011–2942 W of cooling with 42–144 W of fan power; an indicative baseline from a comparable 50 Hz mini-split (8500–11000 Btu/h) shows a rated electrical input of ~880–1070 W, highlighting the low electrical demand of the EAHE fan (catalog-based context, not a side-by-side test). In summary, the EAHE–greenhouse system demonstrates a viable, energy-efficient pilot-scale option for passive cooling in hot climates, with potential for agricultural applications subject to site-specific sizing and installation constraints. 12-30-2025 <![CDATA[ <p>Increasing energy requirements in hot regions highlight the need for sustainable thermal management technologies. A promising passive cooling solution is Earth-Air Heat Exchanger (EAHE) that use the relatively stable temperature of the subsurface soil to pre-cool air supplied to indoor spaces. This study investigates the thermal and hydraulic performance of an EAHE coupled to a greenhouse in severe summer conditions in Nasiriyah city, southern Iraq, experimentally. The system was designed to evaluate its effectiveness in moderating ambient temperature extremes and reducing mechanical cooling energy requirements. Experimental results during July–October showed that the EAHE outlet air temperature stayed between 31 and 38°C despite ambient temperature exceeding 50°C, indicating a stable thermal response of the buried exchanger. The greenhouse air temperature was maintained at 34–40°C during peak daytime hours and decreased to about 29–33°C during the remaining operating periods, confirming improved internal thermal conditions. The thermal effectiveness ($\varepsilon$) ranged from 0.68 to 0.75, and the average temperature drop ($\Delta{T}$) was above 13°C throughout the test period. Furthermore, pressure drop and fan power increased with airflow velocity, consistent with a turbulent flow regime. The EAHE delivered 2011–2942 W of cooling with 42–144 W of fan power; an indicative baseline from a comparable 50 Hz mini-split (8500–11000 Btu/h) shows a rated electrical input of ~880–1070 W, highlighting the low electrical demand of the EAHE fan (catalog-based context, not a side-by-side test). In summary, the EAHE–greenhouse system demonstrates a viable, energy-efficient pilot-scale option for passive cooling in hot climates, with potential for agricultural applications subject to site-specific sizing and installation constraints.</p> ]]> Experimental Testing of Earth to Air Heat Exchanger for Air Conditioning of Greenhouse in Hot Climate Regions hussein l. thamer mushtaq i. hasan doi: 10.56578/ijcmem130412 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 908 10.56578/ijcmem130412 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130412 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130411 This paper experimentally and analytically investigated the effect of pipe wall roughness on hydraulic loss generation in turbulent flow. The study used straight circular pipes with same geometrical dimensions (length = 5 m and internal diameter = 4 cm). Four different metals used such as cast iron, galvanized steel, stainless steel, and copper. Experiments were performed at a flow Reynolds number ($Re$) ranging from approximately 3.4 × 10$^4$ to 5.1 × 10$^4$. The volumetric flow rates were in a range of 80–120 L/min with pressure drop and head loss measured by using a calibrated laboratory setup. The analytical prediction of the head‐loss was conducted using Darcy-Weisbach equation with Colebrook-White friction factor correlations. From the literature data, roughness heights were used to predict the head loss. Experimental and theoretical results can be directly compared, providing an evaluation of model predictiveness accuracy. The frictional head losses depended on the pipe roughness; and it increased from cooper (2.4–2.8 m) to cast iron (3.8–5.2 m), with intermediate values for galvanized and stainless steel, respectively. The friction coefficient ratio measured for the cast iron of 0.031 and copper of 0.018, and this is to indicate different surface roughness. Observed and predicted head losses were in agreement, with errors up to 6–7% relative deviation for smooth-lined pipes, and higher than 8% for roughed ones. The results emphasized the importance of relative roughness in turbulent flow and substantiate the validity of established friction-loss relationships for better engineering design. Model selection and friction loss prediction principles can be practically exploited to aid energy-efficient pipe network design, as well as encourage the recognition of predictive uncertainty. Overall, the study bridges experimental validation and analytical modeling, offering benchmarks for accurate hydraulic analysis under realistic operating conditions. 12-30-2025 <![CDATA[ <p>This paper experimentally and analytically investigated the effect of pipe wall roughness on hydraulic loss generation in turbulent flow. The study used straight circular pipes with same geometrical dimensions (length = 5 m and internal diameter = 4 cm). Four different metals used such as cast iron, galvanized steel, stainless steel, and copper. Experiments were performed at a flow Reynolds number ($Re$) ranging from approximately 3.4 × 10$^4$ to 5.1 × 10$^4$. The volumetric flow rates were in a range of 80–120 L/min with pressure drop and head loss measured by using a calibrated laboratory setup. The analytical prediction of the head‐loss was conducted using Darcy-Weisbach equation with Colebrook-White friction factor correlations. From the literature data, roughness heights were used to predict the head loss. Experimental and theoretical results can be directly compared, providing an evaluation of model predictiveness accuracy. The frictional head losses depended on the pipe roughness; and it increased from cooper (2.4–2.8 m) to cast iron (3.8–5.2 m), with intermediate values for galvanized and stainless steel, respectively. The friction coefficient ratio measured for the cast iron of 0.031 and copper of 0.018, and this is to indicate different surface roughness. Observed and predicted head losses were in agreement, with errors up to 6–7% relative deviation for smooth-lined pipes, and higher than 8% for roughed ones. The results emphasized the importance of relative roughness in turbulent flow and substantiate the validity of established friction-loss relationships for better engineering design. Model selection and friction loss prediction principles can be practically exploited to aid energy-efficient pipe network design, as well as encourage the recognition of predictive uncertainty. Overall, the study bridges experimental validation and analytical modeling, offering benchmarks for accurate hydraulic analysis under realistic operating conditions.</p> ]]> Experimental and Theoretical Analysis of the Effect of Pipe Material on Major Head Losses in Pipes intesar k. atiyah nadya husain muslim nihad a. al-bughaebi audai hussein al-abbas doi: 10.56578/ijcmem130411 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 896 10.56578/ijcmem130411 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130411 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130410 The increasing global energy crisis and concerns about environmental impacts are driving the development of efficient and low-cost renewable energy systems. Solar water heaters (SWH) are an alternative, specifically in tropical countries such as Indonesia, which receive solar radiation intensity of 4–6 kWh/m$^2$/day. Therefore, this study aimed to model the thermal performance of trickle-flow SWH using a lightweight composite material called polymethyl methacrylate (PMMA) as cover and galvalume for the heat absorber plate, which has previously been validated through experiments. The simulation model was developed using a transient lumped-parameter energy balance method and was implemented in Python with minute-by-minute interpolated meteorological data. Model validation was conducted by comparing simulated and experimental inlet and outlet temperatures. It reproduced the main temperature trends and peak values observed in the experiments. Statistical evaluation further indicated a high level of accuracy, with root-mean-square error (RMSE) values of up to 0.81℃ and a coefficient of determination ($R^2$) of 0.986 for outlet temperature. Additional parametric analyses showed the effects of flow rate and tank volume on thermal efficiency. These effects were visualized using efficiency contour plots, while confidence bands were applied to present simulation uncertainty. In general, the results confirmed the feasibility of using lightweight materials in solar collectors and showed the capability of numerical-statistical models for performance prediction as well as design optimization. These findings supported the development of efficient and low-cost SWH systems for tropical regions. 12-30-2025 <![CDATA[ The increasing global energy crisis and concerns about environmental impacts are driving the development of efficient and low-cost renewable energy systems. Solar water heaters (SWH) are an alternative, specifically in tropical countries such as Indonesia, which receive solar radiation intensity of 4–6 kWh/m$^2$/day. Therefore, this study aimed to model the thermal performance of trickle-flow SWH using a lightweight composite material called polymethyl methacrylate (PMMA) as cover and galvalume for the heat absorber plate, which has previously been validated through experiments. The simulation model was developed using a transient lumped-parameter energy balance method and was implemented in Python with minute-by-minute interpolated meteorological data. Model validation was conducted by comparing simulated and experimental inlet and outlet temperatures. It reproduced the main temperature trends and peak values observed in the experiments. Statistical evaluation further indicated a high level of accuracy, with root-mean-square error (RMSE) values of up to 0.81℃ and a coefficient of determination ($R^2$) of 0.986 for outlet temperature. Additional parametric analyses showed the effects of flow rate and tank volume on thermal efficiency. These effects were visualized using efficiency contour plots, while confidence bands were applied to present simulation uncertainty. In general, the results confirmed the feasibility of using lightweight materials in solar collectors and showed the capability of numerical-statistical models for performance prediction as well as design optimization. These findings supported the development of efficient and low-cost SWH systems for tropical regions. ]]> Validated Numerical Model of a Lightweight Trickle-Flow Solar Water Heater for Tropical Applications nugroho agung pambudi dony marly martiawan siregar desita kamila ulfa danny rizki sofyan permana putra doi: 10.56578/ijcmem130410 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 882 10.56578/ijcmem130410 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130410 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130409 The Internet of Things (IoT) consists of a large interconnected system of devices that automatically gather, analyze, and transfer data. Securing the integrity and privacy of these devices is a significant challenge due to their distributed and heterogeneous nature. To address this issue, this paper presents a hybrid security framework that is designed in two phases: Node Topology Measures-based Vulnerable Node Detection (NTMVND) and Adoption-based Differential Evolution (ADE) with Elicited Genetic Algorithm (ADE2GA). The NTMVND component detects vulnerable nodes using important topological measures such as node degree, betweenness, clustering coefficient, and centrality to remove potential risks in the communication network. The ADE2GA component produces optimal and secure paths for data transmission by leveraging the adaptive exploration characteristics of Differential Evolution (DE) and the exploitative learning capabilities of the Genetic Algorithm (GA). The simulation results in Network Simulator-2 shows that the ADE2GA model performs best, resulting in 39% reduction in the end-to-end delay and 26% savings in energy consumption, while producing a 41% increase in throughput and a 10% increase in packet delivery ratio compared to standard Particle Swarm Optimization (PSO) and Differential Evolution with Genetic Algorithm (DEGA) models. The results substantiate the proposed framework's capability for promoting improved integrity, privacy, and efficiency in IoT settings. 12-30-2025 <![CDATA[ <p>The Internet of Things (IoT) consists of a large interconnected system of devices that automatically gather, analyze, and transfer data. Securing the integrity and privacy of these devices is a significant challenge due to their distributed and heterogeneous nature. To address this issue, this paper presents a hybrid security framework that is designed in two phases: Node Topology Measures-based Vulnerable Node Detection (NTMVND) and Adoption-based Differential Evolution (ADE) with Elicited Genetic Algorithm (ADE2GA). The NTMVND component detects vulnerable nodes using important topological measures such as node degree, betweenness, clustering coefficient, and centrality to remove potential risks in the communication network. The ADE2GA component produces optimal and secure paths for data transmission by leveraging the adaptive exploration characteristics of Differential Evolution (DE) and the exploitative learning capabilities of the Genetic Algorithm (GA). The simulation results in Network Simulator-2 shows that the ADE2GA model performs best, resulting in 39% reduction in the end-to-end delay and 26% savings in energy consumption, while producing a 41% increase in throughput and a 10% increase in packet delivery ratio compared to standard Particle Swarm Optimization (PSO) and Differential Evolution with Genetic Algorithm (DEGA) models. The results substantiate the proposed framework's capability for promoting improved integrity, privacy, and efficiency in IoT settings.</p> ]]> Hybrid Framework for Privacy and Integrity in the IoT Environment Using the Network Topology Measures and Deep Learning Techniques h. c. pavithra j. rajeshwari k. s. rekha m. narender bhat geetalaxmi jairam r. sunitha doi: 10.56578/ijcmem130409 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 868 10.56578/ijcmem130409 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130409 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130408 This article presents a mathematical analysis of 3D Williamson nanofluid flow over a stretching Riga plate in a Darcy-Forchheimer porous medium. The model incorporates thermal radiation, heat generation/absorption, and the Buongiorno nanofluid framework with Cattaneo-Christov double flux. Similarity transformations reduce the governing PDEs to ODEs, solved using Mathematica's NDSolve. Graphs and tables illustrate the effects of key parameters on velocity, temperature, concentration, skin friction, Nusselt number, and Sherwood number. The x-direction velocity increases with the modified Hartmann number ($Ha$ = 0.5–2.0), enhancing skin friction by 20–30%. Higher thermophoresis ($Nt$ = 0.1–0.5) elevates temperature and concentration by 15–20% and 10–14%, respectively. Brownian motion ($Nb$ = 0.1–0.5) boosts mass transfer, increasing Sherwood number by 7–9%. Increasing heat and mass relaxation parameters ($\gamma_1$, $\gamma_2$ = 0.1–0.5) accelerates Nusselt and Sherwood numbers by 5–10%. Results correlate well with prior studies, providing a basis for magnetohydrodynamic (MHD) cooling systems, polymer processing, and biomedical simulations involving non-Newtonian fluids. 12-30-2025 <![CDATA[ <p>This article presents a mathematical analysis of 3D Williamson nanofluid flow over a stretching Riga plate in a Darcy-Forchheimer porous medium. The model incorporates thermal radiation, heat generation/absorption, and the Buongiorno nanofluid framework with Cattaneo-Christov double flux. Similarity transformations reduce the governing PDEs to ODEs, solved using Mathematica's NDSolve. Graphs and tables illustrate the effects of key parameters on velocity, temperature, concentration, skin friction, Nusselt number, and Sherwood number. The x-direction velocity increases with the modified Hartmann number ($Ha$ = 0.5–2.0), enhancing skin friction by 20–30%. Higher thermophoresis ($Nt$ = 0.1–0.5) elevates temperature and concentration by 15–20% and 10–14%, respectively. Brownian motion ($Nb$ = 0.1–0.5) boosts mass transfer, increasing Sherwood number by 7–9%. Increasing heat and mass relaxation parameters ($\gamma_1$, $\gamma_2$ = 0.1–0.5) accelerates Nusselt and Sherwood numbers by 5–10%. Results correlate well with prior studies, providing a basis for magnetohydrodynamic (MHD) cooling systems, polymer processing, and biomedical simulations involving non-Newtonian fluids.</p> ]]> Modeling and Analysis of 3D Magnetized Radiative Williamson Nanofluid Flow Past a Riga Plate with Forchheimer-Darcy Porous Medium and Cattaneo-Christov Double Diffusion prathi vijaya kumar shaik mohammed ibrahim kanithi jyothsna buddharaju soujanya giulio lorenzini doi: 10.56578/ijcmem130408 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 845 10.56578/ijcmem130408 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130408 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130407 This work provides a comprehensive evaluation of the effect of shot peening (SP) time on the mechanical, electrochemical, and surface properties of AA6061-T6 aluminum alloy tested in an alkaline chloride medium (pH = 9). The specimens were subjectively peened for varying durations from 0 to 12 min. The subsequent effects on tensile strength, fatigue life, corrosion resistance, surface roughness, and microhardness were studied. The results showed that a SP time of 9 min increased the tensile strength and hardness through strain hardening, dislocation accumulation, and establishment of compressive residual stress. The formation of a strong passive layer and delayed crack initiation also help make the material more resistant to corrosion and fatigue. However, peening for more than 9 min resulted in rough and localized damage and slightly reduced the mechanical performance. The results show that a 9-minute SP duration is the ideal method to strengthen the surface and maintain a strong structure, which makes AA6061-T6 parts last longer under harsh conditions. 12-30-2025 <![CDATA[ <p>This work provides a comprehensive evaluation of the effect of shot peening (SP) time on the mechanical, electrochemical, and surface properties of AA6061-T6 aluminum alloy tested in an alkaline chloride medium (pH = 9). The specimens were subjectively peened for varying durations from 0 to 12 min. The subsequent effects on tensile strength, fatigue life, corrosion resistance, surface roughness, and microhardness were studied. The results showed that a SP time of 9 min increased the tensile strength and hardness through strain hardening, dislocation accumulation, and establishment of compressive residual stress. The formation of a strong passive layer and delayed crack initiation also help make the material more resistant to corrosion and fatigue. However, peening for more than 9 min resulted in rough and localized damage and slightly reduced the mechanical performance. The results show that a 9-minute SP duration is the ideal method to strengthen the surface and maintain a strong structure, which makes AA6061-T6 parts last longer under harsh conditions.</p> ]]> Comprehensive Study on the Influence of Shot Peening Duration on the Mechanical Behavior of Aluminum Alloy AA6061-T6 Exposed to Alkaline Environment khadir mouaid khudhair mohammed abdulraoof abdulrazzaq ali mohammed flayyih doi: 10.56578/ijcmem130407 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 831 10.56578/ijcmem130407 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130407 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130406 Functional plate is one of the most typical materials used for strengthening of reinforced concrete (RC) structures. This article focuses on using functional plates internally to improve the flexural response of RC beams. For this purpose, experimental and numerical investigations on the flexural behavior and ductility of steel-plated RC beams were conducted. Nine RC beams were cast and cured for 28 days. The steel plates were located at the tension side of the RC beams to investigate their effect on the flexural performance of the tested beams. To achieve the research objective, three configurations of the shape of steel plates were proposed, flat, curved, and rounded. The results demonstrate that using embedded steel plates is effective and significantly enhanced the flexural performance of concrete beams. The strengthening delayed the first cracking appearance and increasing of ultimate load up to 45% compared to the reference beam. Further, there was an improvement in ductility and stiffness behaviours by 202% and 46%, respectively, particularly for beams with constrained flat steel plates, which exhibited the highest performance gain. The experimental and finite element (FE) results showed a good agreement in terms of cracking behavior and with approximately 6% maximum ultimate load difference. 12-30-2025 <![CDATA[ <p>Functional plate is one of the most typical materials used for strengthening of reinforced concrete (RC) structures. This article focuses on using functional plates internally to improve the flexural response of RC beams. For this purpose, experimental and numerical investigations on the flexural behavior and ductility of steel-plated RC beams were conducted. Nine RC beams were cast and cured for 28 days. The steel plates were located at the tension side of the RC beams to investigate their effect on the flexural performance of the tested beams. To achieve the research objective, three configurations of the shape of steel plates were proposed, flat, curved, and rounded. The results demonstrate that using embedded steel plates is effective and significantly enhanced the flexural performance of concrete beams. The strengthening delayed the first cracking appearance and increasing of ultimate load up to 45% compared to the reference beam. Further, there was an improvement in ductility and stiffness behaviours by 202% and 46%, respectively, particularly for beams with constrained flat steel plates, which exhibited the highest performance gain. The experimental and finite element (FE) results showed a good agreement in terms of cracking behavior and with approximately 6% maximum ultimate load difference.</p> ]]> Experimental and Numerical Evaluation on the Flexural Behavior of Concrete Beams with Embedded Functional Plates majid muttashar douaa najah doi: 10.56578/ijcmem130406 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 815 10.56578/ijcmem130406 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130406 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130405 This study investigates how cognitive ergonomics-based interface design can enhance user experience and reduce cognitive workload in digital da’wah applications, using the MASJIDA mobile application as a case study. While existing digital da’wah platforms primarily emphasize functional features and content dissemination, limited attention has been given to systematic evaluations of usability and cognitive load. To address this gap, this study integrates cognitive ergonomics principles into the design and evaluation of MASJIDA, a mobile application developed to support mosque management and congregational engagement. A pre-test and post-test experimental design was employed involving mosque administrators and congregants. System usability was measured using the System Usability Scale (SUS), while cognitive workload was assessed using the NASA Task Load Index (NASA-TLX). The results demonstrate a substantial improvement in usability, with SUS scores increasing from 55.1 to 79.3 for congregants and from 55.5 to 85.4 for mosque administrators. In parallel, NASA-TLX results reveal a significant reduction in mental demand, effort, and frustration, indicating lower cognitive workload after implementation. These findings confirm that applying cognitive ergonomics principles contributes not only to improved usability but also to more cognitively efficient user interactions. This study provides empirical evidence and analytical insights for the development of user-centered digital religious applications that balance functional effectiveness with cognitive accessibility. 12-30-2025 <![CDATA[ This study investigates how cognitive ergonomics-based interface design can enhance user experience and reduce cognitive workload in digital da’wah applications, using the MASJIDA mobile application as a case study. While existing digital da’wah platforms primarily emphasize functional features and content dissemination, limited attention has been given to systematic evaluations of usability and cognitive load. To address this gap, this study integrates cognitive ergonomics principles into the design and evaluation of MASJIDA, a mobile application developed to support mosque management and congregational engagement. A pre-test and post-test experimental design was employed involving mosque administrators and congregants. System usability was measured using the System Usability Scale (SUS), while cognitive workload was assessed using the NASA Task Load Index (NASA-TLX). The results demonstrate a substantial improvement in usability, with SUS scores increasing from 55.1 to 79.3 for congregants and from 55.5 to 85.4 for mosque administrators. In parallel, NASA-TLX results reveal a significant reduction in mental demand, effort, and frustration, indicating lower cognitive workload after implementation. These findings confirm that applying cognitive ergonomics principles contributes not only to improved usability but also to more cognitively efficient user interactions. This study provides empirical evidence and analytical insights for the development of user-centered digital religious applications that balance functional effectiveness with cognitive accessibility. ]]> Optimizing Da’wah Through the MASJIDA Application: A Cognitive Ergonomics Approach to Enhance User Experience ririt dwiputri permatasari m. ansyar bora luki hernando vitri aprilla handayani taufiq rahman larisang m. ropianto tommy saputra fitri mehdini addieningrum dukhroni ali alhamidi haidil fauzan nur shilah muhamad andrian yudhistira shafira putri rheyna fani rahma yanti anisa fitrianti doi: 10.56578/ijcmem130405 International Journal of Computational Methods and Experimental Measurements 12-30-2025 International Journal of Computational Methods and Experimental Measurements 12-30-2025 2025 13 4 Article 802 10.56578/ijcmem130405 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130405 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130404 Modern image processing systems deployed on embedded and heterogeneous platforms face increasing pressure to deliver high performance under strict energy and real-time constraints. The rapid growth in image resolution and frame rates has significantly amplified computational demand, making uniform full-precision processing increasingly inefficient. This paper presents a significance-driven adaptive approximate computing framework that reduces energy consumption by tailoring computational precision and resource allocation to the spatial importance of image content. We introduce a statistical importance metric that captures local structural variability using low-complexity deviation-based analysis on luminance information. The metric serves as a lightweight proxy for identifying regions that are more sensitive to approximation errors, enabling differentiated processing without the overhead of semantic or perceptual saliency models. Based on this importance classification, the proposed framework dynamically orchestrates heterogeneous CPU–GPU resources, applies variable kernel sizes, and exploits dynamic voltage and frequency scaling (DVFS) to reclaim timing slack for additional energy savings. The framework is validated through two complementary case studies: (i) a heterogeneous software implementation for adaptive convolution filtering on an Odroid XU-4 embedded platform, and (ii) a hardware-level approximate circuit allocation approach using configurable-precision arithmetic units. Experimental results demonstrate energy reductions of up to 60\% compared to uniform-precision baselines, while maintaining acceptable visual quality. Image quality is evaluated using both PSNR and the perceptually motivated SSIM metric, confirming that the proposed approach preserves structural fidelity despite aggressive approximation. 12-22-2025 <![CDATA[ Modern image processing systems deployed on embedded and heterogeneous platforms face increasing pressure to deliver high performance under strict energy and real-time constraints. The rapid growth in image resolution and frame rates has significantly amplified computational demand, making uniform full-precision processing increasingly inefficient. This paper presents a significance-driven adaptive approximate computing framework that reduces energy consumption by tailoring computational precision and resource allocation to the spatial importance of image content. We introduce a statistical importance metric that captures local structural variability using low-complexity deviation-based analysis on luminance information. The metric serves as a lightweight proxy for identifying regions that are more sensitive to approximation errors, enabling differentiated processing without the overhead of semantic or perceptual saliency models. Based on this importance classification, the proposed framework dynamically orchestrates heterogeneous CPU–GPU resources, applies variable kernel sizes, and exploits dynamic voltage and frequency scaling (DVFS) to reclaim timing slack for additional energy savings. The framework is validated through two complementary case studies: (i) a heterogeneous software implementation for adaptive convolution filtering on an Odroid XU-4 embedded platform, and (ii) a hardware-level approximate circuit allocation approach using configurable-precision arithmetic units. Experimental results demonstrate energy reductions of up to 60\% compared to uniform-precision baselines, while maintaining acceptable visual quality. Image quality is evaluated using both PSNR and the perceptually motivated SSIM metric, confirming that the proposed approach preserves structural fidelity despite aggressive approximation. ]]> Adaptive Quality-Energy Trade-Offs in Image Processing Through Statistical Priority Classification and Variable-Approximate Computing ibrahim haddadi doi: 10.56578/ijcmem130404 International Journal of Computational Methods and Experimental Measurements 12-22-2025 International Journal of Computational Methods and Experimental Measurements 12-22-2025 2025 13 4 Article 785 10.56578/ijcmem130404 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130404 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130403 Despite their influence on the stability of underground excavations, mineralized veinlets, particularly those composed of pyrite and chalcopyrite, are often underestimated in traditional geomechanical models. The lack of experimental data on their tensile behavior under direct stress represents a critical gap in rock mass characterization. This study experimentally evaluated the direct tensile strength of pyrite and chalcopyrite veinlets from the El Teniente mine, in order to enhance the accuracy of geotechnical models for complex geological contexts. Following the Organization for Economic Cooperation and Development (OECD) 203 (2019) guidelines, a fully randomized experimental design was employed to conduct direct tensile testing of 19 veinlet samples. The results showed that chalcopyrite veinlets exhibited greater internal cohesion with significantly higher tensile strength, reaching up to 3.17 MPa, compared to pyrite veinlets of lower values. Furthermore, chalcopyrite veinlets demonstrated a more homogeneous and cohesive failure behavior compared to pyrite, which displayed greater surface roughness and interfacial failure. This study highlights the importance of incorporating veinlet mineralogy into geotechnical models to improve underground design and safety. 12-04-2025 <![CDATA[ Despite their influence on the stability of underground excavations, mineralized veinlets, particularly those composed of pyrite and chalcopyrite, are often underestimated in traditional geomechanical models. The lack of experimental data on their tensile behavior under direct stress represents a critical gap in rock mass characterization. This study experimentally evaluated the direct tensile strength of pyrite and chalcopyrite veinlets from the El Teniente mine, in order to enhance the accuracy of geotechnical models for complex geological contexts. Following the Organization for Economic Cooperation and Development (OECD) 203 (2019) guidelines, a fully randomized experimental design was employed to conduct direct tensile testing of 19 veinlet samples. The results showed that chalcopyrite veinlets exhibited greater internal cohesion with significantly higher tensile strength, reaching up to 3.17 MPa, compared to pyrite veinlets of lower values. Furthermore, chalcopyrite veinlets demonstrated a more homogeneous and cohesive failure behavior compared to pyrite, which displayed greater surface roughness and interfacial failure. This study highlights the importance of incorporating veinlet mineralogy into geotechnical models to improve underground design and safety. ]]> Experimental Model of Direct Tensile Strength of Pyrite and Chalcopyrite Veins: Implications for Rock Mass Stability ccatamayo barrios johnny-henrry victor felix flores-moreno josé agustín esparta-sanchez amilcar tacuri-gamboa jaime palomino-claudio luis alfredo vargas-moreno humberto pehovaz-alvarez enrique guadalupe-gomez jesus alberto torres-guerra doi: 10.56578/ijcmem130403 International Journal of Computational Methods and Experimental Measurements 12-04-2025 International Journal of Computational Methods and Experimental Measurements 12-04-2025 2025 13 4 Article 772 10.56578/ijcmem130403 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130403 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130402 Perovskite solar cells (PSCs) continue to advance toward higher efficiencies, yet the geometrical design of functional layers remains a critical bottleneck for device optimization and manufacturability. This work establishes a hybrid physics-data framework that integrates three-dimensional finite-element modeling with machine-learningbased surrogate prediction to accelerate PSC thickness optimization. A full 3D COMSOL Multiphysics model was developed to resolve charge-transport behavior, spatial electric fields, and recombination profiles within TiO2/MAPbI3/Spiro-OMeTAD architectures. Systematic variations in electron transport layer (ETL), perovskite absorber, and hole transport layer (HTL) thicknesses reveal that device power conversion efficiency (PCE) is governed by a trade-off between optical absorption, interface recombination, and resistive losses. A multi-layer perceptron regressor was trained using simulation data and achieved strong predictive fidelity (R2 ≈ 0.98) with a mean absolute error below 0.3%. The resulting surrogate model rapidly identifies optimal structural configurations without requiring additional high-cost simulations, demonstrating a reduction of design time by more than an order of magnitude. The proposed workflow provides a transferable route toward digital-twin-driven photovoltaic design and offers practical guidance for high-performance PSC engineering with reduced material consumption and enhanced computational efficiency. 11-23-2025 <![CDATA[ <p>Perovskite solar cells (PSCs) continue to advance toward higher efficiencies, yet the geometrical design of functional layers remains a critical bottleneck for device optimization and manufacturability. This work establishes a hybrid physics-data framework that integrates three-dimensional finite-element modeling with machine-learningbased surrogate prediction to accelerate PSC thickness optimization. A full 3D COMSOL Multiphysics model was developed to resolve charge-transport behavior, spatial electric fields, and recombination profiles within TiO₂/MAPbI₃/Spiro-OMeTAD architectures. Systematic variations in electron transport layer (ETL), perovskite absorber, and hole transport layer (HTL) thicknesses reveal that device power conversion efficiency (PCE) is governed by a trade-off between optical absorption, interface recombination, and resistive losses. A multi-layer perceptron regressor was trained using simulation data and achieved strong predictive fidelity (R2 ≈ 0.98) with a mean absolute error below 0.3%. The resulting surrogate model rapidly identifies optimal structural configurations without requiring additional high-cost simulations, demonstrating a reduction of design time by more than an order of magnitude. The proposed workflow provides a transferable route toward digital-twin-driven photovoltaic design and offers practical guidance for high-performance PSC engineering with reduced material consumption and enhanced computational efficiency.</p> ]]> Three-Dimensional Multiphysics Simulation Coupled with Machine-Learning Surrogate Modeling for Thickness Optimization in Perovskite Solar Cells mariam abdallah doi: 10.56578/ijcmem130402 International Journal of Computational Methods and Experimental Measurements 11-23-2025 International Journal of Computational Methods and Experimental Measurements 11-23-2025 2025 13 4 Article 758 10.56578/ijcmem130402 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130402 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130401 Convection heat transfer enhancement techniques play a vital role in many industrial thermal processing applications, including food thermal processing, and the pharmaceutical, and chemical manufacturing industries. These techniques contribute to reducing the size and cost of heat exchangers, conserving energy, improving product quality, and enhancing both energy efficiency and thermal performance. Among passive solutions, corrugated wall tubes are widely adopted in heat exchangers for such applications. This study applies the inverse heat conduction problem (IHCP) method combined with infrared thermography data to estimate the local temperature and convective heat transfer coefficient distributions for forced convection in a transversally corrugated wall tube with high viscosity fluid flow under laminar conditions. The IHCP is solved within the corrugated wall domain using measured external wall temperatures as input. Thermal performance was evaluated over a Reynolds number range of 290–1200. The findings showed that at Re $<$ 350, irregular local temperature and convective heat transfer distributions led to reduced thermal efficiency, unreliable sterilization, and increased microbial risk, whereas for 650 $<$ Re $<$ 1200, thermal efficiency improved significantly. These findings support the development of more efficient heat exchanger designs, offering significant benefits to industries requiring precise thermal management. 11-20-2025 <![CDATA[ Convection heat transfer enhancement techniques play a vital role in many industrial thermal processing applications, including food thermal processing, and the pharmaceutical, and chemical manufacturing industries. These techniques contribute to reducing the size and cost of heat exchangers, conserving energy, improving product quality, and enhancing both energy efficiency and thermal performance. Among passive solutions, corrugated wall tubes are widely adopted in heat exchangers for such applications. This study applies the inverse heat conduction problem (IHCP) method combined with infrared thermography data to estimate the local temperature and convective heat transfer coefficient distributions for forced convection in a transversally corrugated wall tube with high viscosity fluid flow under laminar conditions. The IHCP is solved within the corrugated wall domain using measured external wall temperatures as input. Thermal performance was evaluated over a Reynolds number range of 290–1200. The findings showed that at Re $<$ 350, irregular local temperature and convective heat transfer distributions led to reduced thermal efficiency, unreliable sterilization, and increased microbial risk, whereas for 650 $<$ Re $<$ 1200, thermal efficiency improved significantly. These findings support the development of more efficient heat exchanger designs, offering significant benefits to industries requiring precise thermal management. ]]> Experimental Estimation of the Local Convective Heat Transfer in a Corrugated Tube under the Laminar Flow Regime surafel kifle teklemariam fabio bozzoli luca cattani doi: 10.56578/ijcmem130401 International Journal of Computational Methods and Experimental Measurements 11-20-2025 International Journal of Computational Methods and Experimental Measurements 11-20-2025 2025 13 4 Article 749 10.56578/ijcmem130401 https://www.acadlore.com/article/IJCMEM/2025_13_4/ijcmem130401 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130320 Electromyography (EMG)-based hand gesture classification is a developing core technology for designing intuitive and responsive human-computer interaction, notably for prosthetic control. EMG signals, which reflect muscle activity during contraction, offer a non-invasive and effective method for capturing user gestures. However, because of their natural variability, noise, and temporal richness pose significant hurdles to precise gesture recognition. In this paper, we investigate the use of causal convolutional layers, which are suitable for sequential data, to improve hand gesture recognition from raw EMG signals. We propose a deep neural network which bases on temporal convolutions and integrates residual connections and contextual attention in an end to end hand gesture recognition system. Furthermore, we apply multiple data augmentation techniques to mitigate intra-subject variability and enhance model generalization. Our approach is evaluated on the benchmark NinaProDB1 dataset. The proposed model show impressive classification performance with an average accuracy of 95.31% and where the majority of the gestures from various subjects were accurately recognized. These results demonstrate the effectiveness of causal convolutions and attention mechanisms for robust EMG-based gesture recognition. 10-29-2025 <![CDATA[ <p>Electromyography (EMG)-based hand gesture classification is a developing core technology for designing intuitive and responsive human-computer interaction, notably for prosthetic control. EMG signals, which reflect muscle activity during contraction, offer a non-invasive and effective method for capturing user gestures. However, because of their natural variability, noise, and temporal richness pose significant hurdles to precise gesture recognition. In this paper, we investigate the use of causal convolutional layers, which are suitable for sequential data, to improve hand gesture recognition from raw EMG signals. We propose a deep neural network which bases on temporal convolutions and integrates residual connections and contextual attention in an end to end hand gesture recognition system. Furthermore, we apply multiple data augmentation techniques to mitigate intra-subject variability and enhance model generalization. Our approach is evaluated on the benchmark NinaProDB1 dataset. The proposed model show impressive classification performance with an average accuracy of 95.31% and where the majority of the gestures from various subjects were accurately recognized. These results demonstrate the effectiveness of causal convolutions and attention mechanisms for robust EMG-based gesture recognition.</p> ]]> A Residual Temporal Convolutional with Attention Neural Network for Electromyogram-Based Hand Gesture Recognition rachid namane elhocine boutellaa sif eddine salem yassine babaci doi: 10.56578/ijcmem130320 International Journal of Computational Methods and Experimental Measurements 10-29-2025 International Journal of Computational Methods and Experimental Measurements 10-29-2025 2025 13 3 Article 739 10.56578/ijcmem130320 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130320 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130319 One of the most attractive technologies to reach the final goal of net zero emissions by 2050 lies in the use of green hydrogen that can be supplied to fuel cells for producing electricity and heat. Nowadays, airports are responsible for 13% of the European Union’s transport sector greenhouse gas emissions. In this paper, an innovative containerized modular trigeneration system, named “Hydro-Gen”, has been proposed to cover electric, thermal and cooling demands of a small-medium scale airport via fuel cells fuelled by green hydrogen. A dynamic simulation model of the “Hydro-Gen” system has been developed by means of the TRNSYS platform. The proposed system has been simulated under two operating scenarios with reference to a 1-year period while coupled with the selected airport demand profiles. The simulation results have been analyzed from energy and economic points of view and compared with a traditional energy generation scenario (where the central power grid only is used). The results underlined that the proposed system significantly reduces primary energy consumption under both scenarios up to a maximum 100.9%, while the economic performance are strongly dependent on the unit cost of hydrogen. 10-28-2025 <![CDATA[ <p>One of the most attractive technologies to reach the final goal of net zero emissions by 2050 lies in the use of green hydrogen that can be supplied to fuel cells for producing electricity and heat. Nowadays, airports are responsible for 13% of the European Union’s transport sector greenhouse gas emissions. In this paper, an innovative containerized modular trigeneration system, named “Hydro-Gen”, has been proposed to cover electric, thermal and cooling demands of a small-medium scale airport via fuel cells fuelled by green hydrogen. A dynamic simulation model of the “Hydro-Gen” system has been developed by means of the TRNSYS platform. The proposed system has been simulated under two operating scenarios with reference to a 1-year period while coupled with the selected airport demand profiles. The simulation results have been analyzed from energy and economic points of view and compared with a traditional energy generation scenario (where the central power grid only is used). The results underlined that the proposed system significantly reduces primary energy consumption under both scenarios up to a maximum 100.9%, while the economic performance are strongly dependent on the unit cost of hydrogen.</p> ]]> “Hydro-Gen” Trigeneration System for a Small-Medium Scale Airport: Energy and Economic Performance Assessment via Dynamic Simulations Under Electric-Load Control Strategy emiliano lustrissimi bonifacio bianco sebastiano caravaggi luigi maffei sergio sibilio antonio rosato doi: 10.56578/ijcmem130319 International Journal of Computational Methods and Experimental Measurements 10-28-2025 International Journal of Computational Methods and Experimental Measurements 10-28-2025 2025 13 3 Article 726 10.56578/ijcmem130319 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130319 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130318 This research numerically investigates entropy generation in a laminar forced convective flow of Al$_2$O$_3$-water nanofluid within a 2D axisymmetric pipe under uniform heat flux. The study employed aluminum oxide nanoparticles with a consistent diameter of 30nm, dispersed in water at volumetric concentrations of 1% to 4%. For Reynolds numbers (Re) ranging from 200 to 900, the analysis focused on the interplay between the Nusselt number, thermal-hydraulic performance, and entropy generation as functions of both flow velocity and nanoparticle concentration. Results show that elevating the Re and volume fraction not only increases the Nusselt number but also reduces the total entropy generation by 22.25%. A corresponding rise in pressure drop was also observed with these increases. Consequently, the application of Al$_2$O$_3$-water nanofluid proves to be thermodynamically advantageous, enhancing heat transfer characteristics while simultaneously suppressing entropy generation. 10-27-2025 <![CDATA[ <p>This research numerically investigates entropy generation in a laminar forced convective flow of Al$_2$O$_3$-water nanofluid within a 2D axisymmetric pipe under uniform heat flux. The study employed aluminum oxide nanoparticles with a consistent diameter of 30nm, dispersed in water at volumetric concentrations of 1% to 4%. For Reynolds numbers (Re) ranging from 200 to 900, the analysis focused on the interplay between the Nusselt number, thermal-hydraulic performance, and entropy generation as functions of both flow velocity and nanoparticle concentration. Results show that elevating the Re and volume fraction not only increases the Nusselt number but also reduces the total entropy generation by 22.25%. A corresponding rise in pressure drop was also observed with these increases. Consequently, the application of Al$_2$O$_3$-water nanofluid proves to be thermodynamically advantageous, enhancing heat transfer characteristics while simultaneously suppressing entropy generation.</p> ]]> Study of the Thermal Performance and Entropy Generated by Laminar Flow of a Nanofluid in Pipes zohra souad benguerraiche rachid bessaïh doi: 10.56578/ijcmem130318 International Journal of Computational Methods and Experimental Measurements 10-27-2025 International Journal of Computational Methods and Experimental Measurements 10-27-2025 2025 13 3 Article 709 10.56578/ijcmem130318 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130318 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130317 Heating elements in a circular cross section are mostly utilized as the foundation of heat exchangers because of their simplicity and low production cost. Streamlined circular heaters may separate and create significant wakes, which can result in high-pressure drops. So, they have a much lower hydraulic area and thus need less pumping power. In the context of this research, the main objective is to experimentally investigate the hydrothermal parameters in a water tank heat exchanger heated by new heating fluid supply method. Several heat fluxes were studied during the experiment, and several parameters were considered, such as surface temperature, pumping power, heat flux, Reynolds number, and the averageNusselt. The correlations between those parameters have been developed and analyzed. The values of the Nusselt number change at any change in the Reynolds number, the power of tubular heaters, or the place of the heated cylinder inside the tank. A quasi-linear relationship between pumping power and pressure drop shows that for all heated cylinders in the Re range of 154.34 ≤ ReD ≤ 212.51, the range of mean pumping power was 0.54 × 10−4 ≤ Wp ≤ 4.9 × 10−4. 10-27-2025 <![CDATA[ <p>Heating elements in a circular cross section are mostly utilized as the foundation of heat exchangers because of their simplicity and low production cost. Streamlined circular heaters may separate and create significant wakes, which can result in high-pressure drops. So, they have a much lower hydraulic area and thus need less pumping power. In the context of this research, the main objective is to experimentally investigate the hydrothermal parameters in a water tank heat exchanger heated by new heating fluid supply method. Several heat fluxes were studied during the experiment, and several parameters were considered, such as surface temperature, pumping power, heat flux, Reynolds number, and the averageNusselt. The correlations between those parameters have been developed and analyzed. The values of the Nusselt number change at any change in the Reynolds number, the power of tubular heaters, or the place of the heated cylinder inside the tank. A quasi-linear relationship between pumping power and pressure drop shows that for all heated cylinders in the Re range of 154.34 ≤ ReD ≤ 212.51, the range of mean pumping power was 0.54 × 10⁻⁴ ≤ Wp ≤ 4.9 × 10⁻⁴.</p> ]]> Hydrothermal Analysis of Forced Convection Heat Transfer in an Innovative Tank Heat Exchanger ibrahim a. mahmood tamadher alnasser louay a. mahdi abdulrazzak akroot hasanain a. abdul wahhab doi: 10.56578/ijcmem130317 International Journal of Computational Methods and Experimental Measurements 10-27-2025 International Journal of Computational Methods and Experimental Measurements 10-27-2025 2025 13 3 Article 697 10.56578/ijcmem130317 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130317 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130316 Accurate prediction of Standard Penetration Test (SPT) blow counts from Cone Penetration Test (CPT) data is critical for reliable geotechnical characterization, particularly when SPT data are scarce or difficult to obtain. This study presents a data-driven framework that employs an Artificial Neural Network (ANN) to estimate the corrected SPT blow number ($N_{60}$) using key CPT parameters. The database was compiled from two construction sites in Nasiriyah, Iraq, comprising cone tip resistance ($q_c$), sleeve friction ($fs$), and effective overburden pressure ($\sigma_{vo}^{\prime}$) as input variables. Multiple ANN architectures were trained and validated, and optimal performance was achieved using one hidden layer with eight neurons, yielding a coefficient of determination ($R^2$) of 0.9967, and two hidden layers with six and sixteen neurons, achieving $R^2$ = 0.9976. Relative importance analysis indicated that cone tip resistance contributed 44% to the model’s predictive strength, followed by sleeve friction and effective overburden pressure, each accounting for approximately 26%. Sensitivity analysis confirmed that $N_{60}$ increases with higher input parameters, consistent with soil behavior principles. The ANN model demonstrated high accuracy and generalization capability across both sandy and clayey soils. Design charts derived from the trained model enable practical estimation of $SPT-N$ from CPT results, providing geotechnical engineers with a rapid and reliable tool for site characterization and preliminary design. 10-24-2025 <![CDATA[ <p>Accurate prediction of Standard Penetration Test (SPT) blow counts from Cone Penetration Test (CPT) data is critical for reliable geotechnical characterization, particularly when SPT data are scarce or difficult to obtain. This study presents a data-driven framework that employs an Artificial Neural Network (ANN) to estimate the corrected SPT blow number ($N_{60}$) using key CPT parameters. The database was compiled from two construction sites in Nasiriyah, Iraq, comprising cone tip resistance ($q_c$), sleeve friction ($fs$), and effective overburden pressure ($\sigma_{vo}^{\prime}$) as input variables. Multiple ANN architectures were trained and validated, and optimal performance was achieved using one hidden layer with eight neurons, yielding a coefficient of determination ($R^2$) of 0.9967, and two hidden layers with six and sixteen neurons, achieving $R^2$ = 0.9976. Relative importance analysis indicated that cone tip resistance contributed 44% to the model’s predictive strength, followed by sleeve friction and effective overburden pressure, each accounting for approximately 26%. Sensitivity analysis confirmed that $N_{60}$ increases with higher input parameters, consistent with soil behavior principles. The ANN model demonstrated high accuracy and generalization capability across both sandy and clayey soils. Design charts derived from the trained model enable practical estimation of $SPT-N$ from CPT results, providing geotechnical engineers with a rapid and reliable tool for site characterization and preliminary design.</p> ]]> Development of an Artificial Neural Network Model for Predicting Standard Penetration Test N-Values from Cone Penetration Test Data taisir mohsin ressol shakir doi: 10.56578/ijcmem130316 International Journal of Computational Methods and Experimental Measurements 10-24-2025 International Journal of Computational Methods and Experimental Measurements 10-24-2025 2025 13 3 Article 680 10.56578/ijcmem130316 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130316 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130315 Extreme precipitation events driven by climate change significantly accelerate sediment delivery into alluvial rivers, resulting in substantial morphological alteration and downstream channel instability. This study investigates bed evolution within the downstream segment of the Palu River in Central Sulawesi, Indonesia, by applying a two-dimensional hydrodynamic and sediment transport model in HEC-RAS 2D. Three discharge scenarios representing dry, wet, and extreme rainfall conditions were simulated using river geometry derived from high-resolution DEM and bathymetric measurements. Model performance was calibrated against observed water levels, achieving optimal agreement at a Manning’s roughness coefficient of 0.0295 with a Root Mean Square Error of 0.15. The results demonstrate pronounced spatial variability in riverbed response. Under extreme rainfall, degradation is dominant in the upstream bend zone with maximum erosion depth reaching 0.40 m, while deposition intensifies near the river mouth, producing aggradation up to 0.75 m. Although the spatial patterns remained consistent across all simulated scenarios, the magnitude of morphological change during extreme rainfall reached approximately twice that observed under wet-season discharge. These findings highlight the critical role of extreme flow events in shaping alluvial river morphology and provide essential quantitative benchmarks for river management strategies targeting flood mitigation and navigation safety. 10-24-2025 <![CDATA[ Extreme precipitation events driven by climate change significantly accelerate sediment delivery into alluvial rivers, resulting in substantial morphological alteration and downstream channel instability. This study investigates bed evolution within the downstream segment of the Palu River in Central Sulawesi, Indonesia, by applying a two-dimensional hydrodynamic and sediment transport model in HEC-RAS 2D. Three discharge scenarios representing dry, wet, and extreme rainfall conditions were simulated using river geometry derived from high-resolution DEM and bathymetric measurements. Model performance was calibrated against observed water levels, achieving optimal agreement at a Manning’s roughness coefficient of 0.0295 with a Root Mean Square Error of 0.15. The results demonstrate pronounced spatial variability in riverbed response. Under extreme rainfall, degradation is dominant in the upstream bend zone with maximum erosion depth reaching 0.40 m, while deposition intensifies near the river mouth, producing aggradation up to 0.75 m. Although the spatial patterns remained consistent across all simulated scenarios, the magnitude of morphological change during extreme rainfall reached approximately twice that observed under wet-season discharge. These findings highlight the critical role of extreme flow events in shaping alluvial river morphology and provide essential quantitative benchmarks for river management strategies targeting flood mitigation and navigation safety. ]]> Modeling Bed Morphology Evolution in an Alluvial River under Extreme Rainfall Using a 2D Hydrodynamic–Sediment Transport Approach i gede tunas puji harsanto yassir arafat doi: 10.56578/ijcmem130315 International Journal of Computational Methods and Experimental Measurements 10-24-2025 International Journal of Computational Methods and Experimental Measurements 10-24-2025 2025 13 3 Article 667 10.56578/ijcmem130315 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130315 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130314 Axial micro-hydro turbines' performance is sensitive to design and operational parameters. This study investigates the performance of micro-hydro turbines through advanced computational fluid dynamics simulations utilizing ANSYS FLUENT. A three-dimensional, steady-state RANS approach with the SST $k-\omega$ turbulence model was employed to simulate fluid flow interactions in turbines of 3, 4, and 5 blades, multiple rotational speeds of 100 and 1000 RPM, and flow rates. The research uniquely investigates a design that integrates internal flow control features by incorporating secondary guide blades and axial flow straighteners, which effectively reduce vortex formation and energy dissipation. Results show that increasing blade count significantly boosts mechanical power output and hydraulic head across flow conditions. Turbines operating at higher rotational speeds demonstrate markedly enhanced power generation, indicating the importance of mechanical design for durability under elevated stress. Comparative analyses between water and oil as working fluids reveal interesting fluid-dependent performance trends, with oil exhibiting superior energy transfer at higher RPMs. Validation against empirical data confirms the computational procedure's accuracy, with RMSE below 4%. The best performance was observed with the 5-blade turbine, reaching 95%, 92%, and 95% at rotational speeds of 100, 500, and 1000 RPM, respectively, at 60,700 Reynolds number. This configuration consistently outperformed others, demonstrating superior energy conversion. The addition of axial flow straighteners slightly improved efficiency by minimizing turbulence and vortex losses, confirming that structural enhancements combined with high rotational speeds are key to achieving maximum turbine performance. 10-22-2025 <![CDATA[ <p>Axial micro-hydro turbines' performance is sensitive to design and operational parameters. This study investigates the performance of micro-hydro turbines through advanced computational fluid dynamics simulations utilizing ANSYS FLUENT. A three-dimensional, steady-state RANS approach with the SST $k-\omega$ turbulence model was employed to simulate fluid flow interactions in turbines of 3, 4, and 5 blades, multiple rotational speeds of 100 and 1000 RPM, and flow rates. The research uniquely investigates a design that integrates internal flow control features by incorporating secondary guide blades and axial flow straighteners, which effectively reduce vortex formation and energy dissipation. Results show that increasing blade count significantly boosts mechanical power output and hydraulic head across flow conditions. Turbines operating at higher rotational speeds demonstrate markedly enhanced power generation, indicating the importance of mechanical design for durability under elevated stress. Comparative analyses between water and oil as working fluids reveal interesting fluid-dependent performance trends, with oil exhibiting superior energy transfer at higher RPMs. Validation against empirical data confirms the computational procedure's accuracy, with RMSE below 4%. The best performance was observed with the 5-blade turbine, reaching 95%, 92%, and 95% at rotational speeds of 100, 500, and 1000 RPM, respectively, at 60,700 Reynolds number. This configuration consistently outperformed others, demonstrating superior energy conversion. The addition of axial flow straighteners slightly improved efficiency by minimizing turbulence and vortex losses, confirming that structural enhancements combined with high rotational speeds are key to achieving maximum turbine performance.</p> ]]> Numerical Investigation of the Design and Operational Parameters Effects on the Performance of an Axial Micro-Turbine for Hydropower Generation mays subhi sadeq muna s. kassim doi: 10.56578/ijcmem130314 International Journal of Computational Methods and Experimental Measurements 10-22-2025 International Journal of Computational Methods and Experimental Measurements 10-22-2025 2025 13 3 Article 651 10.56578/ijcmem130314 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130314 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130313 To achieve the European energy and climate goals by 2050, meaningful refurbishment actions are necessary for the existing stock sector, including historic buildings. A relatively new trend in contemporary design emphasizes reusing existing structures instead of constructing new ones, revisiting and reinterpreting practices that have been experimented with in the past. The pertinent question today is how to reconcile the requirements for building protection with the implementation of energy efficiency measures. In this contest stands Villa Manganelli, a creation of the renowned architect Ernesto Basile, showcasing Italian Art Nouveau in Catania from the early twentieth century. Currently, Villa Manganelli needs to be re-functionalized to enable its reuse. A master plan has been developed that encompasses both the functional changes needed to accommodate new activities and energy-efficient measures aimed at reducing the building's energy demands, all while preserving the architectural appeal of this remarkable structure. Due to the lack of data regarding the thermo-physical features of the building envelopes, the first phase of this study consists in an experimental set of measurements carried out to characterize the thermal properties of the building masonry and the indoor thermal conditions. A second phase entails the dynamic numerical simulation of the investigated building through the Design Builder software and its calibration and validation through the comparison with the experimental data. Finally, based on the developed analysis, a first hypothesis of not invasive energy efficient measures for re-functionalization of this building is presented. 10-21-2025 <![CDATA[ To achieve the European energy and climate goals by 2050, meaningful refurbishment actions are necessary for the existing stock sector, including historic buildings. A relatively new trend in contemporary design emphasizes reusing existing structures instead of constructing new ones, revisiting and reinterpreting practices that have been experimented with in the past. The pertinent question today is how to reconcile the requirements for building protection with the implementation of energy efficiency measures. In this contest stands Villa Manganelli, a creation of the renowned architect Ernesto Basile, showcasing Italian Art Nouveau in Catania from the early twentieth century. Currently, Villa Manganelli needs to be re-functionalized to enable its reuse. A master plan has been developed that encompasses both the functional changes needed to accommodate new activities and energy-efficient measures aimed at reducing the building's energy demands, all while preserving the architectural appeal of this remarkable structure. Due to the lack of data regarding the thermo-physical features of the building envelopes, the first phase of this study consists in an experimental set of measurements carried out to characterize the thermal properties of the building masonry and the indoor thermal conditions. A second phase entails the dynamic numerical simulation of the investigated building through the Design Builder software and its calibration and validation through the comparison with the experimental data. Finally, based on the developed analysis, a first hypothesis of not invasive energy efficient measures for re-functionalization of this building is presented. ]]> Renovation of a Historic Building Respecting the Preservation of Cultural Heritage Improving the Energy Efficiency antonio gagliano aneli stefano sapienza vincenzo doi: 10.56578/ijcmem130313 International Journal of Computational Methods and Experimental Measurements 10-21-2025 International Journal of Computational Methods and Experimental Measurements 10-21-2025 2025 13 3 Article 641 10.56578/ijcmem130313 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130313 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130312 This paper presents simulation and experimental validation of a Nonlinear Compensation-based Neuro-Fuzzy (NCNF) controller designed to balance the rotary inverted pendulum (RIP). Traditional linear controllers, such as Proportional-Integral-Derivative (PID) and state-feedback with pole placement, usually achieve satisfactory results in simulations on linearized models. However, their performance decreases in hardware implementation because of disturbances and unmodeled nonlinear effects such as Coulomb friction and mechanical backlash. To overcome these challenges, a feedforward compensation function was developed to cancel these undesired effects, which is combined with an Adaptive Neuro-Fuzzy Inference System (ANFIS) controller that updates PID gains to improve the rotary arm tracking for a square-wave reference and stabilize the pendulum at the upright position. The proposed NCNF controller is validated through hardware-in-the-loop (HIL) experiments and compared with a baseline state-feedback controller. Results show that the arm angle ($\theta$) overshoot decreased from 40.6% to 0.8% (lower step) and from 17.2% to 2.5% (upper), total steady-state $\theta$-error from 5.75° to 0.296°, and the fitness index dropped from 41.12 to 25.23. The nonlinear compensation reduced the gap between simulation and real-time performance, while the ANFIS further improved the defined control metrics. Overall, the NCNF controller achieves more stable and precise tracking than the state-feedback control. 10-21-2025 <![CDATA[ <p>This paper presents simulation and experimental validation of a Nonlinear Compensation-based Neuro-Fuzzy (NCNF) controller designed to balance the rotary inverted pendulum (RIP). Traditional linear controllers, such as Proportional-Integral-Derivative (PID) and state-feedback with pole placement, usually achieve satisfactory results in simulations on linearized models. However, their performance decreases in hardware implementation because of disturbances and unmodeled nonlinear effects such as Coulomb friction and mechanical backlash. To overcome these challenges, a feedforward compensation function was developed to cancel these undesired effects, which is combined with an Adaptive Neuro-Fuzzy Inference System (ANFIS) controller that updates PID gains to improve the rotary arm tracking for a square-wave reference and stabilize the pendulum at the upright position. The proposed NCNF controller is validated through hardware-in-the-loop (HIL) experiments and compared with a baseline state-feedback controller. Results show that the arm angle ($\theta$) overshoot decreased from 40.6% to 0.8% (lower step) and from 17.2% to 2.5% (upper), total steady-state $\theta$-error from 5.75° to 0.296°, and the fitness index dropped from 41.12 to 25.23. The nonlinear compensation reduced the gap between simulation and real-time performance, while the ANFIS further improved the defined control metrics. Overall, the NCNF controller achieves more stable and precise tracking than the state-feedback control.</p> ]]> Real-Time Neuro-Fuzzy Control with Nonlinear Compensation for a Rotary Inverted Pendulum: Experimental Validation and Comparison with State-Feedback mohamed bensaadallah noureddine ghoggali lamir saidi doi: 10.56578/ijcmem130312 International Journal of Computational Methods and Experimental Measurements 10-21-2025 International Journal of Computational Methods and Experimental Measurements 10-21-2025 2025 13 3 Article 622 10.56578/ijcmem130312 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130312 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130311 Biomass-derived syngas is a promising alternative to fossil fuels for various applications, including internal combustion engines for electricity generation and direct combustion for thermal energy. However, numerical modeling of syngas burners is still scarcely addressed in literature compared to more common fuels, posing challenges for the design of high-efficiency combustors with low pollutant emissions. This study presents a two-dimensional computational fluid dynamics (CFD) simulation of a syngas burner, validated against experimental data. The syngas adopted in the combustion tests is produced using a small-scale gasifier prototype fueled by wood pellets. At first, the syngas is premixed with air, then it moves in a cylindrical burner where the key parameters are monitored, including syngas and air volume flow rates, temperature, and syngas composition. Additionally, an emission analyzer is used to measure O$_2$, CO, NO, and NO$_2$, concentrations in the exhaust gases. Given the axial symmetry of the problem, a two-dimensional model is developed to save the computational effort. The simulation results are compared to the experimental measurements including burner temperature and emissions. Despite the simplicity and the reduced effort compared to high-fidelity simulations, the 2D model proves to be able to properly predict both temperature inside the burner and emissions at the exhaust. Therefore, it turns out to be a valuable tool to guide the design of syngas burners. 10-19-2025 <![CDATA[ Biomass-derived syngas is a promising alternative to fossil fuels for various applications, including internal combustion engines for electricity generation and direct combustion for thermal energy. However, numerical modeling of syngas burners is still scarcely addressed in literature compared to more common fuels, posing challenges for the design of high-efficiency combustors with low pollutant emissions. This study presents a two-dimensional computational fluid dynamics (CFD) simulation of a syngas burner, validated against experimental data. The syngas adopted in the combustion tests is produced using a small-scale gasifier prototype fueled by wood pellets. At first, the syngas is premixed with air, then it moves in a cylindrical burner where the key parameters are monitored, including syngas and air volume flow rates, temperature, and syngas composition. Additionally, an emission analyzer is used to measure O$_2$, CO, NO, and NO$_2$, concentrations in the exhaust gases. Given the axial symmetry of the problem, a two-dimensional model is developed to save the computational effort. The simulation results are compared to the experimental measurements including burner temperature and emissions. Despite the simplicity and the reduced effort compared to high-fidelity simulations, the 2D model proves to be able to properly predict both temperature inside the burner and emissions at the exhaust. Therefore, it turns out to be a valuable tool to guide the design of syngas burners. ]]> 2D-CFD Simulation of a Syngas Burner with Experimental Validation gabriele trupia marco puglia fabio berni stefano fontanesi simone pedrazzi paolo tartarini doi: 10.56578/ijcmem130311 International Journal of Computational Methods and Experimental Measurements 10-19-2025 International Journal of Computational Methods and Experimental Measurements 10-19-2025 2025 13 3 Article 612 10.56578/ijcmem130311 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130311 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130310 Rapid motorization and insufficient traffic management continue to intensify congestion in major Iraqi cities such as Baghdad, Basra, and Mosul, highlighting the need for intelligent mobility solutions. Traditional shortest-path algorithms, including Dijkstra and Bellman–Ford, remain limited by static edge weights and cannot respond to evolving traffic states. To address this limitation, this study develops a hybrid computational-intelligence framework that integrates a temporal-attention-enhanced recurrent neural network (RNN) for sequential travel-time prediction, an adaptive neuro-fuzzy inference system (ANFIS) for interpretable decision support, and a genetic algorithm (GA) for dynamic route optimization. A synthetic dataset reflecting diverse congestion patterns and diurnal fluctuations across major Iraqi road networks was constructed for evaluation. Experimental results show that the proposed model reduces mean absolute error by up to 32% in travel-time prediction and shortens route travel time by 15% compared with conventional shortest-path algorithms. These findings demonstrate the advantages of coupling predictive modeling with evolutionary optimization for improving urban mobility performance. The proposed framework offers a scalable basis for future intelligent transportation systems in developing urban environments. 10-17-2025 <![CDATA[ <p>Rapid motorization and insufficient traffic management continue to intensify congestion in major Iraqi cities such as Baghdad, Basra, and Mosul, highlighting the need for intelligent mobility solutions. Traditional shortest-path algorithms, including Dijkstra and Bellman–Ford, remain limited by static edge weights and cannot respond to evolving traffic states. To address this limitation, this study develops a hybrid computational-intelligence framework that integrates a temporal-attention-enhanced recurrent neural network (RNN) for sequential travel-time prediction, an adaptive neuro-fuzzy inference system (ANFIS) for interpretable decision support, and a genetic algorithm (GA) for dynamic route optimization. A synthetic dataset reflecting diverse congestion patterns and diurnal fluctuations across major Iraqi road networks was constructed for evaluation. Experimental results show that the proposed model reduces mean absolute error by up to 32% in travel-time prediction and shortens route travel time by 15% compared with conventional shortest-path algorithms. These findings demonstrate the advantages of coupling predictive modeling with evolutionary optimization for improving urban mobility performance. The proposed framework offers a scalable basis for future intelligent transportation systems in developing urban environments.</p> ]]> Hybrid Computational-Intelligence Framework for Dynamic Travel-Time Prediction and Route Optimization in Traqi Urban Transportation Networks mohanad r. aljanabi ahmed r. kadhim mohammed ridha hammoodi keivan borna doi: 10.56578/ijcmem130310 International Journal of Computational Methods and Experimental Measurements 10-17-2025 International Journal of Computational Methods and Experimental Measurements 10-17-2025 2025 13 3 Article 597 10.56578/ijcmem130310 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130310 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130309 Heat pumps are widely recognized as the most cost-effective solution for decarbonizing the building sector. Their ability to provide both heating and cooling with a single system is especially relevant in today’s context of rising temperatures due to global warming. This work describes a new experimental setup and presents initial results on the performance of an air-to-water heat pump operating with the low-GWP refrigerant R454B in a pilot Zero Energy Building. The system has been equipped with research-grade instrumentation to monitor key parameters in both the refrigerant and hydraulic loops. This paper presents the monitoring system and a thermodynamic model of the building based on RC analogy, which will be compared to the experimental data. These experimental results and the thermodynamic model will serve as the basis for training an AI tool dedicated to the optimal energy management of complex renewable energy systems, from single buildings to energy communities. 10-17-2025 <![CDATA[ Heat pumps are widely recognized as the most cost-effective solution for decarbonizing the building sector. Their ability to provide both heating and cooling with a single system is especially relevant in today’s context of rising temperatures due to global warming. This work describes a new experimental setup and presents initial results on the performance of an air-to-water heat pump operating with the low-GWP refrigerant R454B in a pilot Zero Energy Building. The system has been equipped with research-grade instrumentation to monitor key parameters in both the refrigerant and hydraulic loops. This paper presents the monitoring system and a thermodynamic model of the building based on RC analogy, which will be compared to the experimental data. These experimental results and the thermodynamic model will serve as the basis for training an AI tool dedicated to the optimal energy management of complex renewable energy systems, from single buildings to energy communities. ]]> Experimental Monitoring of an Air-to-Water Heat Pump Working with Low-GWP Refrigerant in a Zero Energy Building as Basis for AI Optimization davide menegazzo lorenzo belussi alice bellazzi ludovico danza francesco salamone giulia lombardo laura vallese sergio bobbo laura fedele doi: 10.56578/ijcmem130309 International Journal of Computational Methods and Experimental Measurements 10-17-2025 International Journal of Computational Methods and Experimental Measurements 10-17-2025 2025 13 3 Article 588 10.56578/ijcmem130309 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130309 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130308 Small object detection in complex scenes remains a challenging task due to background clutter, scale variation, and weak feature representation. Conventional deep learning–based detectors are prone to false positives and missed detections when dealing with dense or low-contrast objects. To address these limitations, this paper proposes an Adaptive Multi-Scale Gated Convolution and Context-Aware Attention Network (AGCAN) designed to enhance small object detection accuracy under complex visual conditions. The model introduces an improved Multi-Scale Gated Convolution Module (MGCM) to replace standard U-Net convolutional blocks, enabling comprehensive extraction of fine-grained object features across multiple scales. A Multi-Information Fusion Enhancement Module (MFEM) is incorporated at skip connections by integrating improved dilated convolution and hybrid residual window attention to minimize information loss and optimize cross-layer feature fusion. Furthermore, the Distance-IoU (DIoU) loss replaces the conventional Smooth L1 loss to accelerate model convergence and improve localization precision. Contextual cues are adaptively integrated into region-of-interest classification to strengthen small-object discrimination. Experimental evaluations on the DIOR and NWPU VHR-10 datasets demonstrate that the proposed network achieves superior performance compared with state-of-the-art methods, effectively reducing false detections and improving robustness in complex environments. 10-17-2025 <![CDATA[ Small object detection in complex scenes remains a challenging task due to background clutter, scale variation, and weak feature representation. Conventional deep learning–based detectors are prone to false positives and missed detections when dealing with dense or low-contrast objects. To address these limitations, this paper proposes an Adaptive Multi-Scale Gated Convolution and Context-Aware Attention Network (AGCAN) designed to enhance small object detection accuracy under complex visual conditions. The model introduces an improved Multi-Scale Gated Convolution Module (MGCM) to replace standard U-Net convolutional blocks, enabling comprehensive extraction of fine-grained object features across multiple scales. A Multi-Information Fusion Enhancement Module (MFEM) is incorporated at skip connections by integrating improved dilated convolution and hybrid residual window attention to minimize information loss and optimize cross-layer feature fusion. Furthermore, the Distance-IoU (DIoU) loss replaces the conventional Smooth L1 loss to accelerate model convergence and improve localization precision. Contextual cues are adaptively integrated into region-of-interest classification to strengthen small-object discrimination. Experimental evaluations on the DIOR and NWPU VHR-10 datasets demonstrate that the proposed network achieves superior performance compared with state-of-the-art methods, effectively reducing false detections and improving robustness in complex environments. ]]> Adaptive Multi-Scale Gated Convolution and Context-Aware Attention Network for Accurate Small Object Detection jia chi wang min po jung shoulin yin hang li doi: 10.56578/ijcmem130308 International Journal of Computational Methods and Experimental Measurements 10-17-2025 International Journal of Computational Methods and Experimental Measurements 10-17-2025 2025 13 3 Article 576 10.56578/ijcmem130308 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130308 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130307 Accurate fruit recognition in natural orchard environments remains a major challenge due to heavy occlusion, illumination variation, and dense clustering. Conventional object detectors, even those incorporating attention mechanisms such as YOLOv7 with attribute attention, often fail to preserve fine spatial details and lose robustness under complex visual conditions. To overcome these limitations, this study proposes DeepHarvestNet, a YOLOv8-based hybrid network that jointly learns depth and visual representations for precise apple detection and localization. The architecture integrates three key modules: (1) Efficient Bidirectional Cross-Attention (EBCA) for handling overlapping fruits and contextual dependencies; (2) Focal Modulation (FM) for enhancing visible apple regions under partial occlusion; and (3) KernelWarehouse Convolution (KWConv) for extracting scale-aware features across varying fruit sizes. In addition, a transformer-based AdaBins depth estimation module enables pixel-wise depth inference, effectively separating foreground fruits from the background to support accurate 3D positioning. Experimental results on a drone-captured orchard dataset demonstrate that DeepHarvestNet achieves a precision of 0.94, recall of 0.95, and F1-score of 0.95—surpassing the enhanced YOLOv7 baseline. The integration of depth cues significantly improves detection reliability and facilitates depth-aware decision-making, underscoring the potential of DeepHarvestNet as a foundation for intelligent and autonomous harvesting systems in precision agriculture. 10-14-2025 <![CDATA[ <p>Accurate fruit recognition in natural orchard environments remains a major challenge due to heavy occlusion, illumination variation, and dense clustering.<span> </span>Conventional object detectors, even those incorporating attention mechanisms such as YOLOv7 with attribute attention, often fail to preserve fine spatial details and lose robustness<span> </span>under<span> </span>complex<span> </span>visual<span> </span>conditions.<span> </span>To<span> </span>overcome<span> </span>these<span> </span>limitations,<span> </span>this<span> </span>study<span> </span>proposes<span> </span>DeepHarvestNet,<span> </span>a YOLOv8-based hybrid network that jointly learns depth and visual representations for precise apple detection and localization.<span> </span>The<span> </span>architecture<span> </span>integrates<span> </span>three<span> </span>key<span> </span>modules:<span> </span>(1)<span> </span>Efficient<span> </span>Bidirectional<span> </span>Cross-Attention<span> </span>(EBCA)<span> </span>for handling overlapping fruits and contextual dependencies; (2) Focal Modulation (FM) for enhancing visible apple <span>regions under partial occlusion; and (3) KernelWarehouse Convolution (KWConv) for extracting scale-aware features </span>across varying fruit sizes.<span> </span>In addition, a transformer-based AdaBins depth estimation module enables pixel-wise depth inference, effectively separating foreground fruits from the background to support accurate 3D positioning. Experimental<span> </span>results<span> </span>on<span> </span>a<span> </span>drone-captured<span> </span>orchard<span> </span>dataset<span> </span>demonstrate<span> </span>that<span> </span>DeepHarvestNet<span> </span>achieves<span> </span>a<span> </span>precision<span> </span>of 0.94,<span> </span>recall<span> </span>of<span> </span>0.95,<span> </span>and<span> </span>F1-score<span> </span>of<span> </span>0.95—surpassing<span> </span>the<span> </span>enhanced<span> </span>YOLOv7<span> </span>baseline.<span> </span>The<span> </span>integration<span> </span>of<span> </span>depth<span> </span>cues significantly<span> </span>improves<span> </span>detection<span> </span>reliability<span> </span>and<span> </span>facilitates<span> </span>depth-aware<span> </span>decision-making,<span> </span>underscoring<span> </span>the<span> </span>potential of DeepHarvestNet as a foundation for intelligent and autonomous harvesting systems in precision agriculture.</p> ]]> DeepHarvestNet: Depth-Visual Fusion Network for Robust Apple Detection in Complex Orchard Environments archana uriti naga jyothi pothabathula doi: 10.56578/ijcmem130307 International Journal of Computational Methods and Experimental Measurements 10-14-2025 International Journal of Computational Methods and Experimental Measurements 10-14-2025 2025 13 3 Article 554 10.56578/ijcmem130307 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130307 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130306 Phenol is a persistent and toxic pollutant in industrial wastewater, demanding efficient and sustainable removal technologies. Conventional treatment methods often suffer from high operational costs, incomplete degradation, and secondary contamination. In this study, ZnO–Fe$_2$O$_3$ nanocomposites were synthesized using pulsed laser ablation in liquid (PLAL)-a clean, surfactant-free, and environmentally benign route—to develop eco-friendly adsorbents for phenol removal. The structural, morphological, and optical characteristics of the as-prepared nanoparticles were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, and zeta potential analysis. The 50:50 ZnO–Fe$_2$O$_3$ composite demonstrated moderate colloidal stability (-28.54 mV), nanoscale crystallinity, and a heterogeneous surface morphology conducive to adsorption. Batch adsorption experiments at an initial phenol concentration of 100 mg/L revealed a maximum removal efficiency of 68.44% under 600 laser pulses after 50 minutes of contact time. The consistent optical band gap values (2.48-2.50 eV) across all samples indicated structural and electronic stability. The enhanced adsorption efficiency was attributed to synergistic interfacial interactions between ZnO and Fe$_2$O$_3$ within the nanocomposite matrix. Although the present work is limited to batch-scale trials under fixed conditions, future studies will investigate the effects of pH, adsorption kinetics, isotherm behavior, and material reusability. Overall, the findings highlight the potential of PLAL-fabricated ZnO–Fe$_2$O$_3$ nanocomposites as sustainable adsorbents for aqueous phenol remediation. 10-14-2025 <![CDATA[ <p>Phenol is a persistent and toxic pollutant in industrial wastewater, demanding efficient and sustainable removal technologies. Conventional treatment methods often suffer from high operational costs, incomplete degradation, and secondary contamination. In this study, ZnO–Fe$_2$O$_3$ nanocomposites were synthesized using pulsed laser ablation in liquid (PLAL)-a clean, surfactant-free, and environmentally benign route—to develop eco-friendly adsorbents for phenol removal. The structural, morphological, and optical characteristics of the as-prepared nanoparticles were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, and zeta potential analysis. The 50:50 ZnO–Fe$_2$O$_3$ composite demonstrated moderate colloidal stability (-28.54 mV), nanoscale crystallinity, and a heterogeneous surface morphology conducive to adsorption. Batch adsorption experiments at an initial phenol concentration of 100 mg/L revealed a maximum removal efficiency of 68.44% under 600 laser pulses after 50 minutes of contact time. The consistent optical band gap values (2.48-2.50 eV) across all samples indicated structural and electronic stability. The enhanced adsorption efficiency was attributed to synergistic interfacial interactions between ZnO and Fe$_2$O$_3$ within the nanocomposite matrix. Although the present work is limited to batch-scale trials under fixed conditions, future studies will investigate the effects of pH, adsorption kinetics, isotherm behavior, and material reusability. Overall, the findings highlight the potential of PLAL-fabricated ZnO–Fe$_2$O$_3$ nanocomposites as sustainable adsorbents for aqueous phenol remediation.</p> ]]> Pulsed Laser Ablation-Derived ZnO-Fe₂O₃ Nanocomposites as Green Adsorbents for Phenol Removal from Aqueous Media mohammed jabbar hammadi mazin h. hasan doi: 10.56578/ijcmem130306 International Journal of Computational Methods and Experimental Measurements 10-14-2025 International Journal of Computational Methods and Experimental Measurements 10-14-2025 2025 13 3 Article 532 10.56578/ijcmem130306 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130306 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130305 Real-time face detection in crowded scenes remains challenging due to small-scale facial regions, heavy occlusion, and complex illumination, which often degrade detection accuracy and computational efficiency. This study presents an enhanced detection framework that integrates Slicing-Aided Hyper Inference (SAHI) with the YOLOv11 architecture to improve small-face recognition under diverse visual conditions. While YOLOv11 provides a high-speed single-stage detection backbone, it tends to lose fine spatial information through downsampling, limiting its sensitivity to tiny faces. SAHI addresses this limitation by partitioning high-resolution images into overlapping slices, enabling localized inference that preserves structural detail and strengthens feature representation for small targets. The proposed YOLOv11–SAHI system was trained and evaluated on the WIDER Face dataset across Easy, Medium, and Hard difficulty levels. Experimental results demonstrate that the integrated framework achieves Average Precision (AP) scores of 96.33%, 95.87%, and 90.81% for the respective subsets—outperforming YOLOv7, YOLOv5, and other lightweight detectors, and closely approaching RetinaFace accuracy. Detailed error analysis reveals that the combined model substantially enhances small-face detection in dense crowds but remains sensitive to severe occlusion, motion blur, and extreme pose variations. Overall, YOLOv11 coupled with SAHI offers a robust and computationally efficient solution for real-time face detection in complex environments, establishing a foundation for future work on pose-invariant feature learning and adaptive slicing optimization. 10-13-2025 <![CDATA[ <p>Real-time face detection in crowded scenes remains challenging due to small-scale facial regions, heavy occlusion, and complex illumination, which often degrade detection accuracy and computational efficiency. This study presents an enhanced detection framework that integrates Slicing-Aided Hyper Inference (SAHI) with the YOLOv11 architecture to improve small-face recognition under diverse visual conditions. While YOLOv11 provides a high-speed single-stage detection backbone, it tends to lose fine spatial information through downsampling, limiting its sensitivity to tiny faces. SAHI addresses this limitation by partitioning high-resolution images into overlapping slices, enabling localized inference that preserves structural detail and strengthens feature representation for small targets. The proposed YOLOv11–SAHI system was trained and evaluated on the WIDER Face dataset across Easy, Medium, and Hard difficulty levels. Experimental results demonstrate that the integrated framework achieves Average Precision (AP) scores of 96.33%, 95.87%, and 90.81% for the respective subsets—outperforming YOLOv7, YOLOv5, and other lightweight detectors, and closely approaching RetinaFace accuracy. Detailed error analysis reveals that the combined model substantially enhances small-face detection in dense crowds but remains sensitive to severe occlusion, motion blur, and extreme pose variations. Overall, YOLOv11 coupled with SAHI offers a robust and computationally efficient solution for real-time face detection in complex environments, establishing a foundation for future work on pose-invariant feature learning and adaptive slicing optimization.</p> ]]> Enhancing Real-Time Face Detection Performance Through YOLOv11 and Slicing-Aided Hyper Inference muhammad fachrurrozi muhammad naufal rachmatullah akhiar wista arum fiber monado doi: 10.56578/ijcmem130305 International Journal of Computational Methods and Experimental Measurements 10-13-2025 International Journal of Computational Methods and Experimental Measurements 10-13-2025 2025 13 3 Article 520 10.56578/ijcmem130305 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130305 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130304 Sediment deposition in Iraqi water channels represents a persistent constraint on agricultural irrigation and industrial water supply systems. Existing predictive models often neglect the unique hydraulic and sedimentological conditions of arid-region channels, limiting their applicability. This study integrates controlled laboratory experiments with statistical modeling to establish an empirical equation that quantifies sediment deposition mass (D) as a function of flow velocity (V), sediment concentration (C), and channel slope (S). A series of 54 experiments were conducted in a recirculating flume under precisely monitored conditions, including triplicate trials to ensure statistical robustness. The resulting power-law model, D=0.024·V-1.32·C0.89·S-0.75, exhibited strong predictive capability with R2=0.93, identifying flow velocity as the dominant governing parameter (56% influence). Optimal channel slopes between 5° and 7° were found to minimize deposition. Field validation within the Al-Diwaniyah irrigation network confirmed the model’s reliability, achieving 89% agreement between predicted and observed deposition values. These findings provide a practical and region-specific framework for improving channel design and maintenance strategies in arid environments. Future extensions will incorporate computational fluid dynamics (CFD) simulations and IoT-based monitoring to support adaptive sediment management. 10-13-2025 <![CDATA[ <p>Sediment deposition in Iraqi water channels represents a persistent constraint on agricultural irrigation and industrial water supply systems. Existing predictive models often neglect the unique hydraulic and sedimentological conditions of arid-region channels, limiting their applicability. This study integrates controlled laboratory experiments with statistical modeling to establish an empirical equation that quantifies sediment deposition mass <em>(D) </em>as a function of flow velocity <em>(V)</em>, sediment concentration<em> (C)</em>, and channel slope <em>(S)</em>. A series of 54 experiments were conducted in a recirculating flume under precisely monitored conditions, including triplicate trials to ensure statistical robustness. The resulting power-law model, D=0.024·V-1.32·C0.89·S-0.75, exhibited strong predictive capability with <em>R²</em>=0.93, identifying flow velocity as the dominant governing parameter (56% influence). Optimal channel slopes between 5<span style="color: rgb(0, 0, 0); font-family: Times New Roman, sans-serif">° </span>and 7<span style="color: rgb(0, 0, 0); font-family: Times New Roman, sans-serif">°</span> were found to minimize deposition. Field validation within the Al-Diwaniyah irrigation network confirmed the model’s reliability, achieving 89% agreement between predicted and observed deposition values. These findings provide a practical and region-specific framework for improving channel design and maintenance strategies in arid environments. Future extensions will incorporate computational fluid dynamics (CFD) simulations and IoT-based monitoring to support adaptive sediment management.</p><p></p> ]]> Empirical Modeling of Sediment Deposition in Iraqi Water Channels Through Laboratory Experiments and Field Validation atheer zaki al-qaisi israa hussein ali zena hussein ali fatima al-zahraa k. al-saeedy mustafa a. al yousif doi: 10.56578/ijcmem130304 International Journal of Computational Methods and Experimental Measurements 10-13-2025 International Journal of Computational Methods and Experimental Measurements 10-13-2025 2025 13 3 Article 507 10.56578/ijcmem130304 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130304 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130303 The integration of heterogeneous medical data remains a major challenge for clinical decision support systems (CDSS). Most existing deep learning (DL) approaches rely primarily on imaging modalities, overlooking the complementary diagnostic value of electronic health records (EHR) and physiological signals such as electrocardiograms (ECG). This study introduces MIMIC-EYE, a secure and explainable multi-modal framework that fuses ECG, chest X-ray (CXR), and MIMIC-III EHR data to enhance diagnostic performance and interpretability. The framework employs a rigorous preprocessing pipeline combining min–max scaling, multiple imputation by chained equations (MICE), Hidden Markov Models (HMMs), Deep Kalman Filters (DKF), and denoising autoencoders to extract robust latent representations. Multi-modal features are fused through concatenation and optimized using a Hybrid Slime Mould–Moth Flame (HSMMF) strategy for feature selection. The predictive module integrates ensemble DL architectures with attention mechanisms and skip connections to capture complex inter-modal dependencies. Model explainability is achieved through Local Interpretable Model-agnostic Explanations (LIME) and Shapley Additive Explanations (SHAP), enabling transparent clinical reasoning. Experimental results demonstrate superior performance, achieving 98.41% accuracy, 98.99% precision, and 98.0% sensitivity—outperforming state-of-the-art baselines. The proposed MIMIC-EYE framework establishes a secure, interpretable, and generalizable foundation for trustworthy AI-driven decision support in critical care environments. 10-11-2025 <![CDATA[ <p>The integration of heterogeneous medical data remains a major challenge for clinical decision support systems (CDSS). Most existing deep learning (DL) approaches rely primarily on imaging modalities, overlooking the complementary diagnostic value of electronic health records (EHR) and physiological signals such as electrocardiograms (ECG). This study introduces MIMIC-EYE, a secure and explainable multi-modal framework that fuses ECG, chest X-ray (CXR), and MIMIC-III EHR data to enhance diagnostic performance and interpretability. The framework employs a rigorous preprocessing pipeline combining min–max scaling, multiple imputation by chained equations (MICE), Hidden Markov Models (HMMs), Deep Kalman Filters (DKF), and denoising autoencoders to extract robust latent representations. Multi-modal features are fused through concatenation and optimized using a Hybrid Slime Mould–Moth Flame (HSMMF) strategy for feature selection. The predictive module integrates ensemble DL architectures with attention mechanisms and skip connections to capture complex inter-modal dependencies. Model explainability is achieved through Local Interpretable Model-agnostic Explanations (LIME) and Shapley Additive Explanations (SHAP), enabling transparent clinical reasoning. Experimental results demonstrate superior performance, achieving 98.41% accuracy, 98.99% precision, and 98.0% sensitivity—outperforming state-of-the-art baselines. The proposed MIMIC-EYE framework establishes a secure, interpretable, and generalizable foundation for trustworthy AI-driven decision support in critical care environments.</p> ]]> MIMIC-EYE: A Secure and Explainable Multi-Modal Deep Learning Framework for Clinical Decision Support santosh kumar shaik sagar imambi doi: 10.56578/ijcmem130303 International Journal of Computational Methods and Experimental Measurements 10-11-2025 International Journal of Computational Methods and Experimental Measurements 10-11-2025 2025 13 3 Article 484 10.56578/ijcmem130303 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130303 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130302 Drones have a problem with command transmission under Ultra-Reliable Low Latency Communication (URLLC) requirements. This paper discusses minimizing Packet Error Rate (PER) in an Unmanned Aerial Vehicle (UAV) relay system that transmits commands under Ultra-Reliable Low Latency Communication requirements. The problem is solved through joint optimization of block-length allocation and UAV placement. To tackle these challenges, the optimization problem was split into two sub-problems to analyze the convexity and monotonicity of each. An iterative optimization algorithm for PER minimization was then formulated, combining the Alternating Direction Method of the Multipliers algorithm (ADMM) with the bisection search method through a perturbation-based iterative approach. Simulation results confirm that the proposed algorithm achieves up to 16.42% improvement in computation time and up to 57.14% in convergence speed compared to the algorithm using the bisection method alone for both problems, and it gives the same performance as that of the exhaustive search method. 10-09-2025 <![CDATA[ <p>Drones have a problem with command transmission under Ultra-Reliable Low Latency Communication (URLLC) requirements. This paper discusses minimizing Packet Error Rate (PER) in an Unmanned Aerial Vehicle (UAV) relay system that transmits commands under Ultra-Reliable Low Latency Communication requirements. The problem is solved through joint optimization of block-length allocation and UAV placement. To tackle these challenges, the optimization problem was split into two sub-problems to analyze the convexity and monotonicity of each. An iterative optimization algorithm for PER minimization was then formulated, combining the Alternating Direction Method of the Multipliers algorithm (ADMM) with the bisection search method through a perturbation-based iterative approach. Simulation results confirm that the proposed algorithm achieves up to 16.42% improvement in computation time and up to 57.14% in convergence speed compared to the algorithm using the bisection method alone for both problems, and it gives the same performance as that of the exhaustive search method.</p> ]]> Optimization of Joint Blocklength and UAV Placement for UAV-Based Relay Ultra-Reliable Low Latency Communication System mohammed j. mohammed aymen d. salman doi: 10.56578/ijcmem130302 International Journal of Computational Methods and Experimental Measurements 10-09-2025 International Journal of Computational Methods and Experimental Measurements 10-09-2025 2025 13 3 Article 474 10.56578/ijcmem130302 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130302 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130301 Predictable routing schemes in Wireless Sensor Networks (WSNs) often suffer from limited scalability, poor energy efficiency, and inadequate adaptability to dynamic network conditions. These limitations reduce the reliability of data transmission and shorten the network’s operational duration. To overcome these challenges, this study develops an adaptive routing framework driven by diverse machine learning (ML) techniques—including supervised learning, reinforcement learning, and regression models—to intelligently select energy-efficient, congestion-aware, and secure routing paths. By continuously learning from network feedback on topology changes, node energy levels, and traffic load, the routing algorithm dynamically optimizes path selection. Simulation experiments demonstrate that the proposed approach significantly outperforms traditional protocols in Packet Delivery Ratio, Energy Consumption, End-to-End Delay, Throughput, and Network Lifetime. Furthermore, the integration of anomaly detection mechanisms using behavioral analysis enhances security by identifying and isolating malicious nodes in real time. The results confirm the effectiveness and scalability of ML-driven routing for next-generation Internet of Things (IoT) and WSN infrastructures. Future work will explore real-world deployments and extended security features. 10-09-2025 <![CDATA[ Predictable routing schemes in Wireless Sensor Networks (WSNs) often suffer from limited scalability, poor energy efficiency, and inadequate adaptability to dynamic network conditions. These limitations reduce the reliability of data transmission and shorten the network’s operational duration. To overcome these challenges, this study develops an adaptive routing framework driven by diverse machine learning (ML) techniques—including supervised learning, reinforcement learning, and regression models—to intelligently select energy-efficient, congestion-aware, and secure routing paths. By continuously learning from network feedback on topology changes, node energy levels, and traffic load, the routing algorithm dynamically optimizes path selection. Simulation experiments demonstrate that the proposed approach significantly outperforms traditional protocols in Packet Delivery Ratio, Energy Consumption, End-to-End Delay, Throughput, and Network Lifetime. Furthermore, the integration of anomaly detection mechanisms using behavioral analysis enhances security by identifying and isolating malicious nodes in real time. The results confirm the effectiveness and scalability of ML-driven routing for next-generation Internet of Things (IoT) and WSN infrastructures. Future work will explore real-world deployments and extended security features. ]]> Adaptive Machine Learning-Driven Routing Framework for Secure and Energy-Efficient Wireless Sensor Networks orchu aruna ravindranath tagore mamilla sameerunnisa shaik doi: 10.56578/ijcmem130301 International Journal of Computational Methods and Experimental Measurements 10-09-2025 International Journal of Computational Methods and Experimental Measurements 10-09-2025 2025 13 3 Article 464 10.56578/ijcmem130301 https://www.acadlore.com/article/IJCMEM/2025_13_3/ijcmem130301 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130220 Additive manufacturing (AM), also known as 3D printing, is a process of creating physical objects directly from digital 3D models by adding material layer by layer. Unlike conventional manufacturing methods—such as subtractive machining or injection molding—which remove material or shape it within molds, AM builds parts incrementally, typically using heat, lasers, or electron beams to bond each layer. Among the seven standardized AM processes, Fused Deposition Modeling (FDM) is the most widely used. FDM works by heating and extruding thermoplastic filaments to form successive layers of a part. While AM offers unique advantages such as complex geometries, lightweight structures, and customization, it also introduces specific design constraints that differ from traditional manufacturing. This paper reviews key design challenges associated with AM, with a focus on FDM, and evaluates current methodologies developed to address these issues. A new design methodology is proposed to optimize part design according to specific machine and material constraints, leveraging the advantages of AM while minimizing its limitations. This approach ensures that designs are not only manufacturable but also meet performance requirements and are optimized for the given specifications. A case study applying this methodology to the FDM process highlights its effectiveness and suggests pathways for further improvements. The findings offer insights into how the new approach can contribute to future research and development in AM design optimization. 06-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Additive manufacturing (AM), also known as 3D printing, is a process of creating physical objects directly from digital 3D models by adding material layer by layer. Unlike conventional manufacturing methods—such as subtractive machining or injection molding—which remove material or shape it within molds, AM builds parts incrementally, typically using heat, lasers, or electron beams to bond each layer. Among the seven standardized AM processes, Fused Deposition Modeling (FDM) is the most widely used. FDM works by heating and extruding thermoplastic filaments to form successive layers of a part. While AM offers unique advantages such as complex geometries, lightweight structures, and customization, it also introduces specific design constraints that differ from traditional manufacturing. This paper reviews key design challenges associated with AM, with a focus on FDM, and evaluates current methodologies developed to address these issues. A new design methodology is proposed to optimize part design according to specific machine and material constraints, leveraging the advantages of AM while minimizing its limitations. This approach ensures that designs are not only manufacturable but also meet performance requirements and are optimized for the given specifications. A case study applying this methodology to the FDM process highlights its effectiveness and suggests pathways for further improvements. The findings offer insights into how the new approach can contribute to future research and development in AM design optimization.</span></p> ]]> A Design Methodology for Additive Manufacturing–Fused Deposition Modeling Case Study houcine salem hamid abouchadi khalid el bikri doi: 10.18280/ijcmem.130220 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 449 10.18280/ijcmem.130220 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130220 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130219 In real-life conditions, rubber components in truck tires are exposed to fluctuating loads, often leading to failure from the formation and growth of cracks-an issue especially common in retreaded tires. Tire retreading is one of the first methods of recycling tires by extending their life cycle, but the lack of knowledge and extensive research on quality tire retreading is putting the lives of road users at stake. The main objective of this research work is to study the spliced pre-cured treaded liners (PTLs) by its mechanical properties, and their endurance life cycle under variable stresses. Two types of PTL rubber compounds were studied: Compound 1, designed for steering axle tires, and Compound 2, designed for driving axle tires. These positions on a truck typically bear the highest loads, requiring materials with strong mechanical properties. The study evaluated these compounds using three tests: hardness, tensile strength, and endurance. The hardness test measured the resistance of the rubber to indentation using the Shore A scale, a standard method for rubber materials. Compound 1 (for steering tires) showed a Shore A hardness value of 62, while Compound 2 (for driving tires) had a value of 66. Both values fall within the industry standard range of 50–70 for tire rubber, indicating that the splicing process did not negatively affect the curing or hardness of the PTL materials. The tensile test demonstrated that the spliced joints maintained strong performance, with only a minor reduction in maximum load and elongation compared to unsliced material. The endurance test further confirmed the durability of the spliced PTL under simulated real-world conditions. Overall, the results show that the splicing and use of pre-cured treaded liners-incorporating recycled tread waste-can maintain the necessary mechanical properties for demanding truck tire applications, while also supporting more sustainable and efficient production practices. 06-29-2025 <![CDATA[ <p>In real-life conditions, rubber components in truck tires are exposed to fluctuating loads, often leading to failure from the formation and growth of cracks-an issue especially common in retreaded tires. Tire retreading is one of the first methods of recycling tires by extending their life cycle, but the lack of knowledge and extensive research on quality tire retreading is putting the lives of road users at stake. The main objective of this research work is to study the spliced pre-cured treaded liners (PTLs) by its mechanical properties, and their endurance life cycle under variable stresses. Two types of PTL rubber compounds were studied: Compound 1, designed for steering axle tires, and Compound 2, designed for driving axle tires. These positions on a truck typically bear the highest loads, requiring materials with strong mechanical properties. The study evaluated these compounds using three tests: hardness, tensile strength, and endurance. The hardness test measured the resistance of the rubber to indentation using the Shore A scale, a standard method for rubber materials. Compound 1 (for steering tires) showed a Shore A hardness value of 62, while Compound 2 (for driving tires) had a value of 66. Both values fall within the industry standard range of 50–70 for tire rubber, indicating that the splicing process did not negatively affect the curing or hardness of the PTL materials. The tensile test demonstrated that the spliced joints maintained strong performance, with only a minor reduction in maximum load and elongation compared to unsliced material. The endurance test further confirmed the durability of the spliced PTL under simulated real-world conditions. Overall, the results show that the splicing and use of pre-cured treaded liners-incorporating recycled tread waste-can maintain the necessary mechanical properties for demanding truck tire applications, while also supporting more sustainable and efficient production practices.</p> ]]> Analyzing the Mechanical Properties of Integrated Tread Liner Scraps for Enhanced Efficiency and Sustainability ahmed zarzoor nabeel almuramady maher khudhair thar albarody husam al-jothery doi: 10.18280/ijcmem.130219 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 441 10.18280/ijcmem.130219 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130219 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130218 This article proposes an optimization framework for bus elimination in power system networks using the Kron Reduction Method (KRM), aimed at reducing system complexity while maintaining computational accuracy. Using the IEEE 14-bus system as a testbed, we evaluate seven sequential reduction scenarios, reducing the network from 14 to 7 buses. To improve the quality of reduction, the study integrates Kron’s Loss Equation (KLE) with electrical centrality measures to prioritize passive bus elimination based on loss sensitivity and network topology. The results demonstrate that indiscriminate bus removal can cause substantial deviations in voltage profiles and power loss estimations, whereas the proposed loss-aware approach achieves improved accuracy and stability in reduced models. Visualizations of Y-bus matrix transformations and voltage deviation metrics illustrate the trade-offs between model simplification and fidelity. The proposed methodology supports real-time system modelling and is scalable for larger grid applications. Future extensions include automated reduction strategies leveraging machine learning and applications in dynamic grid optimization. 06-29-2025 <![CDATA[ <p><span style="font-family: Times, serif">This article proposes an optimization framework for bus elimination in power system networks using the Kron Reduction Method (KRM), aimed at reducing system complexity while maintaining computational accuracy. Using the IEEE 14-bus system as a testbed, we evaluate seven sequential reduction scenarios, reducing the network from 14 to 7 buses. To improve the quality of reduction, the study integrates Kron’s Loss Equation (KLE) with electrical centrality measures to prioritize passive bus elimination based on loss sensitivity and network topology. The results demonstrate that indiscriminate bus removal can cause substantial deviations in voltage profiles and power loss estimations, whereas the proposed loss-aware approach achieves improved accuracy and stability in reduced models. Visualizations of </span><em><span style="font-family: Times, serif">Y</span>_{<span style="font-family: Times, serif">-bus</span>}</em><span style="font-family: Times, serif"> matrix transformations and voltage deviation metrics illustrate the trade-offs between model simplification and fidelity. The proposed methodology supports real-time system modelling and is scalable for larger grid applications. Future extensions include automated reduction strategies leveraging machine learning and applications in dynamic grid optimization.</span></p> ]]> Optimizing Bus Elimination with Kron Reduction Method: An Experimental Evaluation on the IEEE 14-Bus System arief goeritno jangkung raharjo muhammad ary murti kharisma bani adam doi: 10.18280/ijcmem.130218 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 427 10.18280/ijcmem.130218 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130218 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130217 This work analyzes how inlet tube velocities (2, 4, and 6 m/s) impact the water-ethylene glycol mixture’s flow behavior within the inlet tube in the engine oil heat exchanger cooling system in terms of temperature distribution, oil viscosity, pressure difference, and flow velocity distribution. From simulation findings, oil's viscosity reduced from 0.021 Pa.s at 2 m/s flow velocity to 0.015 Pa.s at 6 m/s flow velocity, suggesting a direct relationship between the thermal and flow rate. Pressure drop rises with the inlet velocity increase, from 2 to 6 m/s, with values of 0.45 and 0.92 Pa. In the tube-end bending investigation, influences on the velocity profile for emulsion were observed. Depending on the velocity gradient in curved tubes at 2 and 1.2 m/s was the maximum velocity at the sharply curved wall, 2.3 m/s, and at the inner wall, 1.7 m/s. The gradient at 4 m/s was 1.6 m/s, whereas at 6 m/s the gradient was 3.0 m/s. Heat transfer coefficient increases with velocity, ranging from 500 W/m²·K at 2 m/s to 950 at 6 m/s. This shows remarkable enhancement in convective heat transfer resulting from increased turbulence. There is also significant fluctuation in the velocity inside the tubes, and while it increases, the velocity towards uniform flow distribution will improve heat transfer within the tubes. This change inside the tubes reduces uneven heat distribution and helps increase the flow rate, especially when temperature differences grow and the main fluid experiences strong heat transfer. Heat transfer rate rises from 15 kW at 2 m/s velocity to 35 kW at 6 m/s velocity, and efficiency increases to 70% due to increasing inlet velocity. 06-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">This work analyzes how inlet tube velocities (2, 4, and 6 m/s) impact the water-ethylene glycol mixture’s flow behavior within the inlet tube in the engine oil heat exchanger cooling system in terms of temperature distribution, oil viscosity, pressure difference, and flow velocity distribution. From simulation findings, oil's viscosity reduced from 0.021 Pa.s at 2 m/s flow velocity to 0.015 Pa.s at 6 m/s flow velocity, suggesting a direct relationship between the thermal and flow rate. Pressure drop rises with the inlet velocity increase, from 2 to 6 m/s, with values of 0.45 and 0.92 Pa. In the tube-end bending investigation, influences on the velocity profile for emulsion were observed. Depending on the velocity gradient in curved tubes at 2 and 1.2 m/s was the maximum velocity at the sharply curved wall, 2.3 m/s, and at the inner wall, 1.7 m/s. The gradient at 4 m/s was 1.6 m/s, whereas at 6 m/s the gradient was 3.0 m/s. Heat transfer coefficient increases with velocity, ranging from 500 W/m²·K at 2 m/s to 950 at 6 m/s. This shows remarkable enhancement in convective heat transfer resulting from increased turbulence. There is also significant fluctuation in the velocity inside the tubes, and while it increases, the velocity towards uniform flow distribution will improve heat transfer within the tubes. This change inside the tubes reduces uneven heat distribution and helps increase the flow rate, especially when temperature differences grow and the main fluid experiences strong heat transfer. Heat transfer rate rises from 15 kW at 2 m/s velocity to 35 kW at 6 m/s velocity, and efficiency increases to 70% due to increasing inlet velocity.</span></p> ]]> Parametric Study of Heat Transfer in Shell and Tube Heat Exchanger: Cooling of Engine Oil with Water and Ethylene Glycol Mixtures ayad k. hassan hashim s. mohaisen karar saeed mohammed muhammad asmail eleiwi hasan shakir majdi doi: 10.18280/ijcmem.130217 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 405 10.18280/ijcmem.130217 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130217 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130216 Neck injuries remain a critical concern in vehicle safety, particularly during dynamic movements and terrain-induced impacts. Traditional test dummies and wearable devices often fail to capture real-time biomechanical neck responses under such conditions. This study introduces a smart mannequin system designed to measure axial forces and cervical moments in realistic vehicle environments. The system integrates S-type load cells and HX711 amplifiers with a Raspberry Pi 4 for real-time processing, enhanced by Kalman filtering for signal clarity. Calibration was conducted using reference weights from 5 N to 40 N in 5 N increments, with each step validated against a force gauge. The mannequin was tested across various terrains, including straight tracks, inclines, sinusoidal roads, and uneven surfaces, representing realistic military and civilian vehicle conditions. Results showed minimal calibration deviation (2–4 N), with peak force measurements reaching 30.63 N and moment readings up to 1.25 Nm. Higher speeds reduced axial loading on stable tracks, while irregular terrain increased neck strain. The system consistently captured neck loading dynamics, offering a safe, repeatable alternative to human-based testing. Its practical application spans ergonomic vehicle design, occupant safety analysis, and fatigue detection in transport environments. 06-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Neck injuries remain a critical concern in vehicle safety, particularly during dynamic movements and terrain-induced impacts. Traditional test dummies and wearable devices often fail to capture real-time biomechanical neck responses under such conditions. This study introduces a smart mannequin system designed to measure axial forces and cervical moments in realistic vehicle environments. The system integrates S-type load cells and HX711 amplifiers with a Raspberry Pi 4 for real-time processing, enhanced by Kalman filtering for signal clarity. Calibration was conducted using reference weights from 5 N to 40 N in 5 N increments, with each step validated against a force gauge. The mannequin was tested across various terrains, including straight tracks, inclines, sinusoidal roads, and uneven surfaces, representing realistic military and civilian vehicle conditions. Results showed minimal calibration deviation (2–4 N), with peak force measurements reaching 30.63 N and moment readings up to 1.25 Nm. Higher speeds reduced axial loading on stable tracks, while irregular terrain increased neck strain. The system consistently captured neck loading dynamics, offering a safe, repeatable alternative to human-based testing. Its practical application spans ergonomic vehicle design, occupant safety analysis, and fatigue detection in transport environments.</span></p> ]]> Experimental Analysis of Neck Biomechanics Under Dynamic Vehicle Conditions Using a Load Cell-Based Measurement Framework waskito jumali asni dawam giva andriana mutiara muhammad rizqy alfarisi doi: 10.18280/ijcmem.130216 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 391 10.18280/ijcmem.130216 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130216 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130215 In this work, we introduce a hybrid method that combines Long Short-Term Memory (LSTM) neural networks with Taylor Series Expansion (TSE) to solve high-dimensional Fredholm Integral Equations of the second kind (SFIEs). Specifically, we focus on systems with up to 10000 dimensions, which are common in fields like fluid dynamics, electromagnetics, and quantum mechanics. Traditional methods for solving these equations, such as discretization, collocation, and iterative solvers, face significant challenges in high-dimensional spaces due to their computational cost and slow convergence. LSTM networks approximate the solution functions, and Taylor Series Expansion refines the approximation, ensuring higher accuracy and computational efficiency. Numerical experiments demonstrate that the hybrid method significantly outperforms traditional approaches in both accuracy and stability. This method provides a promising approach to solving complex high-dimensional integral equations efficiently in scientific and engineering applications. 06-29-2025 <![CDATA[ <p>In this work, we introduce a hybrid method that combines Long Short-Term Memory (LSTM) neural networks with Taylor Series Expansion (TSE) to solve high-dimensional Fredholm Integral Equations of the second kind (SFIEs). Specifically, we focus on systems with up to 10000 dimensions, which are common in fields like fluid dynamics, electromagnetics, and quantum mechanics. Traditional methods for solving these equations, such as discretization, collocation, and iterative solvers, face significant challenges in high-dimensional spaces due to their computational cost and slow convergence. LSTM networks approximate the solution functions, and Taylor Series Expansion refines the approximation, ensuring higher accuracy and computational efficiency. Numerical experiments demonstrate that the hybrid method significantly outperforms traditional approaches in both accuracy and stability. This method provides a promising approach to solving complex high-dimensional integral equations efficiently in scientific and engineering applications.</p> ]]> A Hybrid LSTM-TSE Approach for Solving High-Dimensional System of Fredholm Integral Equations of the Second Kind rania khallout maroua grid salem tegani adel chala doi: 10.18280/ijcmem.130215 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 381 10.18280/ijcmem.130215 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130215 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130214 To solve the Traveling Salesman Problem (TSP), this research compares three swarm-based optimization algorithms: Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO), and Elephant Herding Optimization (EHO). Finding the shortest path to visit each city once and return to the starting point is the goal of the traditional combinatorial optimization problem, TSP. Exact techniques such as Branch and Bound (BB) and Dynamic Programming (DP) can effectively handle smaller TSP cases, but they become unfeasible as the number of cities increases. The solutions offered by metaheuristic algorithms are more scalable. The algorithms' performance is assessed in this study based on execution time, scalability, and solution quality for a range of city sizes (5 to 150). Results reveal that EHO surpasses the others in achieving lower optimal costs. 06-29-2025 <![CDATA[ <p>To solve the Traveling Salesman Problem (TSP), this research compares three swarm-based optimization algorithms: Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO), and Elephant Herding Optimization (EHO). Finding the shortest path to visit each city once and return to the starting point is the goal of the traditional combinatorial optimization problem, TSP. Exact techniques such as Branch and Bound (BB) and Dynamic Programming (DP) can effectively handle smaller TSP cases, but they become unfeasible as the number of cities increases. The solutions offered by metaheuristic algorithms are more scalable. The algorithms' performance is assessed in this study based on execution time, scalability, and solution quality for a range of city sizes (5 to 150). Results reveal that EHO surpasses the others in achieving lower optimal costs.</p> ]]> Charting New Routes: Comparing Swarm-Based Approaches to the Traveling Salesman Problem ali hassan ahmed wadi shahla uthman umar doi: 10.18280/ijcmem.130214 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 371 10.18280/ijcmem.130214 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130214 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130213 Aluminium alloys are widely used in various industries due to their excellent strength-to-weight ratio, corrosion resistance, and formability. However, their wear resistance and ductility can be limiting factors in certain applications. This study investigates the effects of reduction ratio and extrusion temperature on the wear rate and ductility of Al 6063 extrudates. A systematic experimental approach was employed, involving the extrusion of aluminium samples at varying reduction ratios (20%, 40%, and 60%) and temperatures (400℃, 450℃, and 500℃). Quadratic models were developed to predict extruded wear rate and ductility, revealing reduction ratio and temperature as significant factors (p 06-29-2025 <![CDATA[ <p>Aluminium alloys are widely used in various industries due to their excellent strength-to-weight ratio, corrosion resistance, and formability. However, their wear resistance and ductility can be limiting factors in certain applications. This study investigates the effects of reduction ratio and extrusion temperature on the wear rate and ductility of Al 6063 extrudates. A systematic experimental approach was employed, involving the extrusion of aluminium samples at varying reduction ratios (20%, 40%, and 60%) and temperatures (400℃, 450℃, and 500℃). Quadratic models were developed to predict extruded wear rate and ductility, revealing reduction ratio and temperature as significant factors (p<0.05). The results showed that increased reduction percentage led to decreased wear rate, while enhanced grain sizes were achieved with increased reduction ratio and temperature. This research provides valuable insights for optimizing extrusion parameters to improve the wear resistance and ductility of formed Al 6063, which can be applied in various industries, such as aerospace, automotive, and construction, where high-performance aluminium alloys are critical.</p> ]]> Temperature and Reduction Ratio Effects on Wear Rate and Ductility of Direct Extruded Aluminium 6063: A Numerical and Experimental Investigation temitayo mufutau azeez humbulani simon phuluwa doi: 10.18280/ijcmem.130213 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 361 10.18280/ijcmem.130213 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130213 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130212 This research addresses the challenge of optimizing the dynamic performance of functionally graded porous plates, which are widely used in aerospace, automotive, and structural applications, where internal porosities can significantly impact their stability and functionality. This study mainly uses an effective layer wise model to examine how the internal porosities affect the mechanical stability and natural frequencies of FGP plates. According to the ratio of porosity distribution, porosity locations, and three typical thicknesses, the vibration behaviors of functionally graded plates are analyzed. The effective material properties are modeled employing a power law. The primary objective of this study is to understand how these factors impact the vibrational behavior of FGM plates and to provide validated results that can serve as a reliable reference for future research. The model's validity and efficiency were established through a rigorous comparison with existing literature. The investigation findings highlight the significant influence of porosity distribution on the mechanical behavior of functionally graded plates. The highest frequency obtained was 259.81 Hz for a plate thickness of 20 mm and a porosity ratio of 0.3 when the porous layer was located in the middle, resulting in an 11.9% increase in the frequency compared to other porosity distributions. These results hold potential as a valuable reference point for future research endeavors in this domain. 06-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">This research addresses the challenge of optimizing the dynamic performance of functionally graded porous plates, which are widely used in aerospace, automotive, and structural applications, where internal porosities can significantly impact their stability and functionality. This study mainly uses an effective layer wise model to examine how the internal porosities affect the mechanical stability and natural frequencies of FGP plates. According to the ratio of porosity distribution, porosity locations, and three typical thicknesses, the vibration behaviors of functionally graded plates are analyzed. The effective material properties are modeled employing a power law. The primary objective of this study is to understand how these factors impact the vibrational behavior of FGM plates and to provide validated results that can serve as a reliable reference for future research. The model's validity and efficiency were established through a rigorous comparison with existing literature. The investigation findings highlight the significant influence of porosity distribution on the mechanical behavior of functionally graded plates. The highest frequency obtained was 259.81 Hz for a plate thickness of 20 mm and a porosity ratio of 0.3 when the porous layer was located in the middle, resulting in an 11.9% increase in the frequency compared to other porosity distributions. These results hold potential as a valuable reference point for future research endeavors in this domain.</span></p> ]]> Free Vibration Analysis on Functionally Graded Material Plates with Diverse Porosity Layers muthanna i. fayyadh arz y. qwam alden doi: 10.18280/ijcmem.130212 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 351 10.18280/ijcmem.130212 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130212 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130211 This study introduces Chebyshev Metaheuristic Solver Approach (CMSA), a new computational approach, to get approximate solutions with high-accuracy to a vast range of linear and non-linear differential equations (DEs). The main idea is changing the differential problem into a continuous optimization task. First the approximate solution was written as a truncated series of Chebyshev polynomials, where they are chosen due to their numerical stability and optimal approximation properties. The undetermined coefficients of this series turn into the decision variables in an optimization task. The objective function is derived from the residual of the differential equation, integrated with penalty terms to achieve initial or boundary conditions enforcement. Then the Flower Pollination Algorithm (FPA), a nature-inspired metaheuristic algorithm, is used to find the optimal polynomial coefficients via the minimization of this objective function. This hybrid approach symbiotically integrates the spectral method’s exponential convergence properties with the metaheuristic’s powerful global search capabilities. The demonstration of the efficiency and robustness of the approach is done through rigorous computational tests on benchmark problems, involving integro-differential and non-linear boundary value problems. A comparison of the computed results with known exact solutions, validates this optimization-driven spectral technique, showing excellent accordance. The approach is simple to implement and displays outstanding potential for tackling complex DE systems where traditional methods maybe stick. 06-29-2025 <![CDATA[ <p>This study introduces Chebyshev Metaheuristic Solver Approach (CMSA), a new computational approach, to get approximate solutions with high-accuracy to a vast range of linear and non-linear differential equations (DEs). The main idea is changing the differential problem into a continuous optimization task. First the approximate solution was written as a truncated series of Chebyshev polynomials, where they are chosen due to their numerical stability and optimal approximation properties. The undetermined coefficients of this series turn into the decision variables in an optimization task. The objective function is derived from the residual of the differential equation, integrated with penalty terms to achieve initial or boundary conditions enforcement. Then the Flower Pollination Algorithm (FPA), a nature-inspired metaheuristic algorithm, is used to find the optimal polynomial coefficients via the minimization of this objective function. This hybrid approach symbiotically integrates the spectral method’s exponential convergence properties with the metaheuristic’s powerful global search capabilities. The demonstration of the efficiency and robustness of the approach is done through rigorous computational tests on benchmark problems, involving integro-differential and non-linear boundary value problems. A comparison of the computed results with known exact solutions, validates this optimization-driven spectral technique, showing excellent accordance. The approach is simple to implement and displays outstanding potential for tackling complex DE systems where traditional methods maybe stick.</p> ]]> Spectral Approximations Optimized by Flower Pollination Algorithm for Solving Differential Equations ghedjemis fatiha khelil naceur doi: 10.18280/ijcmem.130211 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 343 10.18280/ijcmem.130211 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130211 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130210 The objective of this paper is to examine the design effect of the gas flow field on fuel cell performance. A polymer electrolyte membrane (PEM) fuel cell with 10 W power output operating at 3 A and 4.5 V has been simulated. The study investigates seven configurations of fuel cell assemblies featuring a Z-shaped flow field and explores the effects of various flow fields and flow channel designs. Single Z-type serpentine flow fields with a channel width of 1 mm were modeled to create interconnected pathways. CFD COMSOL Multiphysics 6.1 was used to analyze a three-dimensional, steady-state, isothermal fuel cell model with an active area of 9.84 cm². The study focused on pressure loss, reactions and product distributions, and current density within the fuel cell. Results showed that Model E2 achieved the lowest anode pressure drop at 7 Pa, while Model A1 exhibited the highest pressure drop at 180 Pa, indicating Model E2's superior pressure management. Cathode pressure analysis revealed that Models A1 and A2 generated the highest pressures. Polarization curve analysis determined that Model A2 delivered the highest current density but at elevated pressures up to 1200 Pa. Among the tested configurations, Model E2 emerged as the optimal design, offering excellent performance with minimal pressure drop and enhanced current density. It enabled uniform reactant gas dispersion, leading to a consistent and reliable current distribution across the electrode surface. Moreover, the Model E2 design promoted improved lateral species transfer and uniform species distribution within the gas diffusion layer, contributing to its superior performance. 06-29-2025 <![CDATA[ <p>The objective of this paper is to examine the design effect of the gas flow field on fuel cell performance. A polymer electrolyte membrane (PEM) fuel cell with 10 W power output operating at 3 A and 4.5 V has been simulated. The study investigates seven configurations of fuel cell assemblies featuring a Z-shaped flow field and explores the effects of various flow fields and flow channel designs. Single Z-type serpentine flow fields with a channel width of 1 mm were modeled to create interconnected pathways. CFD COMSOL Multiphysics 6.1 was used to analyze a three-dimensional, steady-state, isothermal fuel cell model with an active area of 9.84 cm². The study focused on pressure loss, reactions and product distributions, and current density within the fuel cell. Results showed that Model E2 achieved the lowest anode pressure drop at 7 Pa, while Model A1 exhibited the highest pressure drop at 180 Pa, indicating Model E2's superior pressure management. Cathode pressure analysis revealed that Models A1 and A2 generated the highest pressures. Polarization curve analysis determined that Model A2 delivered the highest current density but at elevated pressures up to 1200 Pa. Among the tested configurations, Model E2 emerged as the optimal design, offering excellent performance with minimal pressure drop and enhanced current density. It enabled uniform reactant gas dispersion, leading to a consistent and reliable current distribution across the electrode surface. Moreover, the Model E2 design promoted improved lateral species transfer and uniform species distribution within the gas diffusion layer, contributing to its superior performance.</p> ]]> Optimizing Proton Exchange Membrane Fuel Cell Performance Through Flow Field Design Analysis ahmed s. salman omid jahanian mustafa a. almaliki tabark j. alwan doi: 10.18280/ijcmem.130210 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 331 10.18280/ijcmem.130210 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130210 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130209 Multiple-input-multiple-output (MIMO) techniques and effective precoding algorithms are required due to the inherent difficulties of Millimeter-Wave (mmWave) propagation. The challenges include the significant route loss due to high-frequency usage. Further, the sparse channel matrix yields improper channel estimation (CE), resulting in erroneous reception, which limits the implementation of mmWave technology. Therefore, beam formation is required to direct the power in the direction of the user by exploiting the spatial multiplexing of MIMO. The above-stated limitations, along with hardware constraints of using a lesser number of radio frequency (RF) chains, can be mitigated through effective precoding at the transmitter. The efficient utilization of mmWave bandwidth by users is crucial for a spectrally efficient system, as it helps conserve this scarce resource. Hence, this study has examined the spectral efficiency (SE) of mmWave MIMO systems for various precoding strategies, including minimum mean-square estimation (MMSE) precoding, fully digital and hybrid zero-forcing (ZF) precoding, and analog beamforming. The performance in terms of achievable SE has been studied considering variability in the user base and the number of transmit and receive antennas. Simulation results have been presented, showing that the MMSE precoder outperforms the ZF precoder. Furthermore, the dominant fully digital MMSE precoder approaches the SE of single-user MIMO as the number of users increases, compared to the fully digital ZF precoder. 06-29-2025 <![CDATA[ <p>Multiple-input-multiple-output (MIMO) techniques and effective precoding algorithms are required due to the inherent difficulties of Millimeter-Wave (mmWave) propagation. The challenges include the significant route loss due to high-frequency usage. Further, the sparse channel matrix yields improper channel estimation (CE), resulting in erroneous reception, which limits the implementation of mmWave technology. Therefore, beam formation is required to direct the power in the direction of the user by exploiting the spatial multiplexing of MIMO. The above-stated limitations, along with hardware constraints of using a lesser number of radio frequency (RF) chains, can be mitigated through effective precoding at the transmitter. The efficient utilization of mmWave bandwidth by users is crucial for a spectrally efficient system, as it helps conserve this scarce resource. Hence, this study has examined the spectral efficiency (SE) of mmWave MIMO systems for various precoding strategies, including minimum mean-square estimation (MMSE) precoding, fully digital and hybrid zero-forcing (ZF) precoding, and analog beamforming. The performance in terms of achievable SE has been studied considering variability in the user base and the number of transmit and receive antennas. Simulation results have been presented, showing that the MMSE precoder outperforms the ZF precoder. Furthermore, the dominant fully digital MMSE precoder approaches the SE of single-user MIMO as the number of users increases, compared to the fully digital ZF precoder.</p> ]]> Spectral Efficiency of Millimeter Wave Multiple-Input-Multiple-Output System for Different Precoding Techniques lokesh bhardwaj doi: 10.18280/ijcmem.130209 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 323 10.18280/ijcmem.130209 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130209 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130208 Traffic congestion is a major issue faced by Batam, a city that continues to grow rapidly as an economic and logistics hub. This study adopts the Design Science Research Methodology (DSRM) to develop an intelligent navigation system based on artificial intelligence (AI) aimed at optimizing urban traffic management in Batam. The system integrates real-time traffic data, machine learning algorithms, and reinforcement learning to predict traffic flow and optimize route selection. Using the DSRM framework, the system was designed, implemented, and evaluated iteratively to ensure its effectiveness in addressing the city's unique traffic challenges. The results of the study indicate that the implementation of the AI-based navigation system successfully reduced the average travel time by 22.8%, distributed traffic loads more evenly, and improved travel efficiency. Furthermore, the system demonstrated a route prediction accuracy of 91.3%, higher than conventional GPS systems. Performance evaluation also showed high responsiveness, with an average latency of only 423 milliseconds. This study concludes that the AI-based navigation system, developed through the DSRM framework, can be an effective solution to address traffic congestion in rapidly developing cities like Batam and can be applied to other cities with similar characteristics. 06-29-2025 <![CDATA[ <p>Traffic congestion is a major issue faced by Batam, a city that continues to grow rapidly as an economic and logistics hub. This study adopts the Design Science Research Methodology (DSRM) to develop an intelligent navigation system based on artificial intelligence (AI) aimed at optimizing urban traffic management in Batam. The system integrates real-time traffic data, machine learning algorithms, and reinforcement learning to predict traffic flow and optimize route selection. Using the DSRM framework, the system was designed, implemented, and evaluated iteratively to ensure its effectiveness in addressing the city's unique traffic challenges. The results of the study indicate that the implementation of the AI-based navigation system successfully reduced the average travel time by 22.8%, distributed traffic loads more evenly, and improved travel efficiency. Furthermore, the system demonstrated a route prediction accuracy of 91.3%, higher than conventional GPS systems. Performance evaluation also showed high responsiveness, with an average latency of only 423 milliseconds. This study concludes that the AI-based navigation system, developed through the DSRM framework, can be an effective solution to address traffic congestion in rapidly developing cities like Batam and can be applied to other cities with similar characteristics.</p> ]]> Artificial Intelligence-Based Intelligent Navigation System for Alleviating Traffic Congestion: A Case Study in Batam City, Indonesia luki hernando ririt dwiputri permatasari sri dwi ana melia m. ansyar bora alhamidi aulia agung dermawan doi: 10.18280/ijcmem.130208 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 309 10.18280/ijcmem.130208 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130208 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130207 A bridge is a construction that enables traffic to cross a barrier while keeping in touch with roads or railroads. Throughout history, bridges have played a crucial role in human civilisation and remain an essential component of any transportation network. The main purpose of this study is to evaluate the seismic resistance of bridge structure under effect of earthquake action by adopting force-displacement yielding points and performance points methods. The results of force-displacement yielding point and performance points revealed that the transversal yielding points were greater than the longitudinal yielding points and performance points, this indicates that the seismic action on the transversal bents has little effect and that no damage will be done to the bents if they are subjected to this action alone but in longitudinal direction the force-displacement yielding point and performance points were lower, indicating that the seismic resistance performance of bridge bents is small with low elasticity and stiffness and high plasticity. Meaning that bridge bents capacity cannot resist the demand. Therefore, Therefore, this study suggested to improve the structural performance and seismic resistance of bridge bents by increasing the diameter of bridge piers by 1.6m, 1.8m, and 2m. After thickening the piers structure, the results of yielding points and performance points values were increased with increasing the piers diameter. And the seismic displacement decreased with increasing the piers diameter. Indicating that the elastic limit of bridge bents will increase and the bridge piers will resist the earthquake action according to increase in the stiffness and bearing capacity of bridge bents. 06-29-2025 <![CDATA[ <p>A bridge is a construction that enables traffic to cross a barrier while keeping in touch with roads or railroads. Throughout history, bridges have played a crucial role in human civilisation and remain an essential component of any transportation network. The main purpose of this study is to evaluate the seismic resistance of bridge structure under effect of earthquake action by adopting force-displacement yielding points and performance points methods. The results of force-displacement yielding point and performance points revealed that the transversal yielding points were greater than the longitudinal yielding points and performance points, this indicates that the seismic action on the transversal bents has little effect and that no damage will be done to the bents if they are subjected to this action alone but in longitudinal direction the force-displacement yielding point and performance points were lower, indicating that the seismic resistance performance of bridge bents is small with low elasticity and stiffness and high plasticity. Meaning that bridge bents capacity cannot resist the demand. Therefore, Therefore, this study suggested to improve the structural performance and seismic resistance of bridge bents by increasing the diameter of bridge piers by 1.6m, 1.8m, and 2m. After thickening the piers structure, the results of yielding points and performance points values were increased with increasing the piers diameter. And the seismic displacement decreased with increasing the piers diameter. Indicating that the elastic limit of bridge bents will increase and the bridge piers will resist the earthquake action according to increase in the stiffness and bearing capacity of bridge bents.</p> ]]> Seismic Resistance Evaluation of Precast Prestressed Concrete Simply Supported I-Girder Bridge by Adopting Non-Linear Static Analysis of Pushover Method afyaa saad neamaha ali fadhil naser doi: 10.18280/ijcmem.130207 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 281 10.18280/ijcmem.130207 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130207 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130206 Time series count data such as daily cases of Covid-19 requires adequate modelling and forecasting. Traditional time series models do not have limitations in modelling time series count data, also known as unbounded N-valued data. This study involved in-depth analyses of various models in fitting time unbounded N-valued data. Models such as the Zero-Inflated Poisson, zero-inflated Binomial, and ARIMA popularly used to fit time series count were compared with the integer-valued generalized autoregressive conditional heteroscedasticity (INGARCH) models. The investigation involved two critical aspects: simulation and real-life data analysis. First, we simulated the time series count data, modelled and compared the performance of the competing models. The simulation outcomes consistently favoured the Negative Binomial INGARCH models highlighting their suitability for count data modelling. Subsequently, we examined life data on Covid-19 data in Nigeria. The life data also yielded strong support for the NB INGARCH model. This study recommends further exploration of the NB INGARCH model, as it exhibits substantial promise in effectively modelling over-dispersed zero-inflated data. The current study contributes valuable insights into selecting appropriate models for time series count data, addressing the intricate challenges posed by this specialized data type. Also, the overall outcome of the study helps in national planning, and resource allocation for the people needing health intervention. 06-29-2025 <![CDATA[ <p>Time series count data such as daily cases of Covid-19 requires adequate modelling and forecasting. Traditional time series models do not have limitations in modelling time series count data, also known as unbounded N-valued data. This study involved in-depth analyses of various models in fitting time unbounded N-valued data. Models such as the Zero-Inflated Poisson, zero-inflated Binomial, and ARIMA popularly used to fit time series count were compared with the integer-valued generalized autoregressive conditional heteroscedasticity (INGARCH) models. The investigation involved two critical aspects: simulation and real-life data analysis. First, we simulated the time series count data, modelled and compared the performance of the competing models. The simulation outcomes consistently favoured the Negative Binomial INGARCH models highlighting their suitability for count data modelling. Subsequently, we examined life data on Covid-19 data in Nigeria. The life data also yielded strong support for the NB INGARCH model. This study recommends further exploration of the NB INGARCH model, as it exhibits substantial promise in effectively modelling over-dispersed zero-inflated data. The current study contributes valuable insights into selecting appropriate models for time series count data, addressing the intricate challenges posed by this specialized data type. Also, the overall outcome of the study helps in national planning, and resource allocation for the people needing health intervention.</p> ]]> Modelling Zero-Inflated Time Series Count Data Using Covid-19 Data olumide s. adesina lawrence. o. obokoh doi: 10.18280/ijcmem.130206 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 273 10.18280/ijcmem.130206 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130206 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130205 Adequate indoor lighting is essential for ensuring visual comfort, energy efficiency, and compliance with architectural standards. This study presents a novel smartphone-based platform for real-time illuminance estimation and visual mapping, that leverages a lightweight machine learning model. The application utilizes the smartphone’s built-in camera to capture images of the scenes and performs illuminance prediction for each patch of the image using a trained regression model, offering a cost-effective alternative to physical lux meter grid. The mobile application generates a color-coded heat maps that visualize the spatial distribution of illuminance and do the assessment of its compliance with an established lighting norm. The advantages of the proposed system include its affordability, portability, and prediction accuracy enabled by the machine learning model trained on image intensity features. Experimental tests in a controlled indoor setting demonstrate high prediction accuracy and low computational requirements, confirming the platform’s suitability for use in real-word applications. The tool enables effective and precise analysis of light and is hence usable in architectural diagnostics, energy audits, and spatial design optimization. In addition, the user-friendly interface benefits both professional and non-professional users, facilitating real-time adjustment and optimization of indoor lighting. 06-29-2025 <![CDATA[ <p>Adequate indoor lighting is essential for ensuring visual comfort, energy efficiency, and compliance with architectural standards. This study presents a novel smartphone-based platform for real-time illuminance estimation and visual mapping, that leverages a lightweight machine learning model. The application utilizes the smartphone’s built-in camera to capture images of the scenes and performs illuminance prediction for each patch of the image using a trained regression model, offering a cost-effective alternative to physical lux meter grid. The mobile application generates a color-coded heat maps that visualize the spatial distribution of illuminance and do the assessment of its compliance with an established lighting norm. The advantages of the proposed system include its affordability, portability, and prediction accuracy enabled by the machine learning model trained on image intensity features. Experimental tests in a controlled indoor setting demonstrate high prediction accuracy and low computational requirements, confirming the platform’s suitability for use in real-word applications. The tool enables effective and precise analysis of light and is hence usable in architectural diagnostics, energy audits, and spatial design optimization. In addition, the user-friendly interface benefits both professional and non-professional users, facilitating real-time adjustment and optimization of indoor lighting.</p> ]]> A Machine Learning-Based Tool for Indoor Lighting Compliance and Energy Optimization abderraouf seniguer abdelhamid iratni mustapha aouache hadja yakoubi haithem mekhermeche doi: 10.18280/ijcmem.130205 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 259 10.18280/ijcmem.130205 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130205 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130204 Wireless propagation is a crucial technology in modern advancements, requiring highly accurate prediction. Path loss propagation is influenced by various parameters that must be accounted for to predict the signal route over the entire distance and refine breakpoint models with precise interference calculations. The breakpoint distance is defined as the point separating two distinct trends of path loss, each following a different path loss exponent. This paper reviews the Fresnel, Perera, and True breakpoints in a dual-slope model reference at 2 GHz, using a fixed exponent of n₁ = 2 before the breakpoint and n₂ = 4 after. It then proposes a distance-adaptive exponent model that considers a steady path by incorporating a flexible exponent based on environmental factors, mitigating the abrupt change in path loss exponent at breakpoints observed in the dual-slope model, which leads to discontinuities. The comparison results under similar conditions demonstrate that both models perform similarly over short distances of up to 100 meters, while the dual-slope model is more suitable for distances of up to 1 km. However, due to its stability and consistency, the distance-adaptive exponent model is more appropriate for longer distances. Validation using RMSE, followed by comparative analysis, confirms that our model offers higher stability in interference scenarios. These findings will assist researchers and wireless designers in predicting and selecting the most accurate and effective propagation model. 06-29-2025 <![CDATA[ <p>Wireless propagation is a crucial technology in modern advancements, requiring highly accurate prediction. Path loss propagation is influenced by various parameters that must be accounted for to predict the signal route over the entire distance and refine breakpoint models with precise interference calculations. The breakpoint distance is defined as the point separating two distinct trends of path loss, each following a different path loss exponent. This paper reviews the Fresnel, Perera, and True breakpoints in a dual-slope model reference at 2 GHz, using a fixed exponent of n₁ = 2 before the breakpoint and n₂ = 4 after. It then proposes a distance-adaptive exponent model that considers a steady path by incorporating a flexible exponent based on environmental factors, mitigating the abrupt change in path loss exponent at breakpoints observed in the dual-slope model, which leads to discontinuities. The comparison results under similar conditions demonstrate that both models perform similarly over short distances of up to 100 meters, while the dual-slope model is more suitable for distances of up to 1 km. However, due to its stability and consistency, the distance-adaptive exponent model is more appropriate for longer distances. Validation using RMSE, followed by comparative analysis, confirms that our model offers higher stability in interference scenarios. These findings will assist researchers and wireless designers in predicting and selecting the most accurate and effective propagation model.</p> ]]> Refining the Dual-Slope Path Loss Model with a Distance-Adaptive Exponent and Multi-Breakpoint Calibration imadeldin elsayed elmutasim doi: 10.18280/ijcmem.130204 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 251 10.18280/ijcmem.130204 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130204 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130203 Fiber-plastic composites are increasingly used in the aerospace, automotive, and wind energy industries, often exposed to multi-axial mechanical loads and high climatic stresses. The objective of this study is to investigate the fatigue behavior of these composites as a function of multi-axial mechanical stress by a novel developed degradation model based on continuum-damage-mechanical approaches. The model's simulation performance has been examined and demonstrated it is applicable in engineering practice. CFRC composites exhibit 74.5 MPa of tensile strength, but GF(MLG)/EP glass fiber reinforced composites demonstrate a considerable lack in both stiffness and regular deformation until ultimate failure. The failure of textile-reinforced plastic composites occurred in three stages of degradation. The tensile strength of biaxial NCF glass-reinforced polyester material was increased by 13 percent as well as the fatigue endurance by 20 percent as compared to the woven roving reinforced composites. The damage onset was 25-35% of the beginning stage. The structure then stabilized to 10-15% and then failed. In GF-MLG/EP, a pattern of stiffness change according to a direction was observed, where transverse cracks reduced the stiffness to 75% of its initial value after 10,000 cycles. Fatigue damage is more resistant in biaxial NCF composites than in woven fabric composites. 06-29-2025 <![CDATA[ <p>Fiber-plastic composites are increasingly used in the aerospace, automotive, and wind energy industries, often exposed to multi-axial mechanical loads and high climatic stresses. The objective of this study is to investigate the fatigue behavior of these composites as a function of multi-axial mechanical stress by a novel developed degradation model based on continuum-damage-mechanical approaches. The model's simulation performance has been examined and demonstrated it is applicable in engineering practice. CFRC composites exhibit 74.5 MPa of tensile strength, but GF(MLG)/EP glass fiber reinforced composites demonstrate a considerable lack in both stiffness and regular deformation until ultimate failure. The failure of textile-reinforced plastic composites occurred in three stages of degradation. The tensile strength of biaxial NCF glass-reinforced polyester material was increased by 13 percent as well as the fatigue endurance by 20 percent as compared to the woven roving reinforced composites. The damage onset was 25-35% of the beginning stage. The structure then stabilized to 10-15% and then failed. In GF-MLG/EP, a pattern of stiffness change according to a direction was observed, where transverse cracks reduced the stiffness to 75% of its initial value after 10,000 cycles. Fatigue damage is more resistant in biaxial NCF composites than in woven fabric composites.</p> ]]> Development and Evaluation of Physically Based Fatigue Damage Model in Textile-Reinforced Plastics auday s. hadi mohammed m. azzawi atheer r. abdullah doi: 10.18280/ijcmem.130203 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 239 10.18280/ijcmem.130203 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130203 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130202 Each employee has a number of workloads in the form of tasks and responsibilities that must be completed within a certain period of time. There are several aspects that are assessed in performance evaluations, such as the number of working hours per week, the number of projects handled, the number of overtime hours to complete work, the number of sick days, the number of team members, the number of hours to develop self-skills, job promotion offers, etc. All of these aspects certainly impact performance scores, employee satisfaction scores, and the ability to survive. Excessive workload will have a negative impact on physical and mental health, performance, and employee satisfaction levels. This study aims to analyze the results of employee performance evaluations based on workload factors using machine learning approaches such as linear regression and random forest. The computational results will be used to compare the effectiveness of machine learning models and analyze the accuracy of the assessment results. The significance of this study lies in its potential to enhance employee performance management systems by providing accurate, data-driven insights for decision-making processes such as promotions, compensation, and workforce planning. Practical and fair employee performance assessments will enable decision-makers to make informed choices regarding job promotions, salary increases, annual bonuses, and employee career development. 06-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Each employee has a number of workloads in the form of tasks and responsibilities that must be completed within a certain period of time. There are several aspects that are assessed in performance evaluations, such as the number of working hours per week, the number of projects handled, the number of overtime hours to complete work, the number of sick days, the number of team members, the number of hours to develop self-skills, job promotion offers, etc. All of these aspects certainly impact performance scores, employee satisfaction scores, and the ability to survive. Excessive workload will have a negative impact on physical and mental health, performance, and employee satisfaction levels. This study aims to analyze the results of employee performance evaluations based on workload factors using machine learning approaches such as linear regression and random forest. The computational results will be used to compare the effectiveness of machine learning models and analyze the accuracy of the assessment results. The significance of this study lies in its potential to enhance employee performance management systems by providing accurate, data-driven insights for decision-making processes such as promotions, compensation, and workforce planning. Practical and fair employee performance assessments will enable decision-makers to make informed choices regarding job promotions, salary increases, annual bonuses, and employee career development.</span></p> ]]> Computational Modeling Using Linear Regression and Random Forest to Analyze the Impact of Workload on Employee Performance Evaluations safitri jaya aries yulianto edi purwanto doi: 10.18280/ijcmem.130202 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 227 10.18280/ijcmem.130202 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130202 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130201 In today's digitalized production environments, AI-supported systems not only transform production processes, but also complicate the nature of decisions taken in these processes. Especially in smart production scenarios where edge and cloud computing infrastructures are used together, decision processes must be managed with both low-latency local data and large-volume centralized analyses. This bidirectional data flow brings about multi-criteria decision problems that cannot be easily solved with classical algorithms due to the presence of incomplete, uncertain and unstable information. This study proposes a new decision support model for such multi-criteria and uncertain decision problems that arise in computer-aided production environments. Unlike classical data analytics methods, our model is designed based on the T-Spherical Hesitant Fuzzy Rough Set (T-SHFR) theory. While T-SHFR evaluates decision alternatives in the triangle of truth, falsehood and uncertainty, it can also systematically process incomplete or contradictory data with hesitant membership and rough set logic. In this respect, the model goes beyond the artificial intelligence applications frequently found in the literature and offers a structure where uncertainty is directly modeled. In the study, this method was integrated with edge and cloud computing architectures and the multi-criteria performance of Edge-only, Cloud-only and Hybrid approaches was evaluated; scenario-based analyses were conducted on basic parameters such as production efficiency, downtime, cost and resource usage. The findings show that the T-SHFR-based model significantly increases decision quality especially in hybrid architectures and offers higher stability and flexibility in stuations where classical methods are difficult. Thus, the proposed approach offers a holistic framework that strengthens decision making under uncertainty in computer-driven production systems. 06-29-2025 <![CDATA[ <p>In today's digitalized production environments, AI-supported systems not only transform production processes, but also complicate the nature of decisions taken in these processes. Especially in smart production scenarios where edge and cloud computing infrastructures are used together, decision processes must be managed with both low-latency local data and large-volume centralized analyses. This bidirectional data flow brings about multi-criteria decision problems that cannot be easily solved with classical algorithms due to the presence of incomplete, uncertain and unstable information. This study proposes a new decision support model for such multi-criteria and uncertain decision problems that arise in computer-aided production environments. Unlike classical data analytics methods, our model is designed based on the T-Spherical Hesitant Fuzzy Rough Set (T-SHFR) theory. While T-SHFR evaluates decision alternatives in the triangle of truth, falsehood and uncertainty, it can also systematically process incomplete or contradictory data with hesitant membership and rough set logic. In this respect, the model goes beyond the artificial intelligence applications frequently found in the literature and offers a structure where uncertainty is directly modeled. In the study, this method was integrated with edge and cloud computing architectures and the multi-criteria performance of Edge-only, Cloud-only and Hybrid approaches was evaluated; scenario-based analyses were conducted on basic parameters such as production efficiency, downtime, cost and resource usage. The findings show that the T-SHFR-based model significantly increases decision quality especially in hybrid architectures and offers higher stability and flexibility in stuations where classical methods are difficult. Thus, the proposed approach offers a holistic framework that strengthens decision making under uncertainty in computer-driven production systems.</p> ]]> Enhancing Decision Quality in Smart Manufacturing: Uncertainty-Aware Evaluation of Edge–Cloud Architectures with T-Spherical Hesitant Fuzzy Rough Sets safiye turgay enes emre başar mücahit çalışan mehmet furkan geçkil mahmut baydaş željko stević doi: 10.18280/ijcmem.130201 International Journal of Computational Methods and Experimental Measurements 06-29-2025 International Journal of Computational Methods and Experimental Measurements 06-29-2025 2025 13 2 Article 211 10.18280/ijcmem.130201 https://www.acadlore.com/article/IJCMEM/2025_13_2/ijcmem.130201 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130120 This study presents a machine learning framework for predicting gold prices by integrating diverse financial indicators, including the NASDAQ-100 index (^NDX), Bitcoin (BTC-USD), and gold futures (GC=F). Using daily high prices from February 2020 to May 2024, the approach incorporates robust preprocessing techniques such as the Box-Cox transformation and Principal Component Analysis (PCA) to address skewness, kurtosis, and multicollinearity, to reduce dimensionality while retaining 96.37% of the variance. A Genetic Algorithm-optimized Multi-Layer Perceptron (MLP) regression model achieved high predictive accuracy with an R² score of 0.98, an RMSE of 23.48 USD, and an MAE of 17.38 USD. Permutation importance analysis highlighted PC1 and PC2 as the most significant predictors, collectively capturing over 96% of the dataset's variance. The results emphasize the effectiveness of integrating stock indices, cryptocurrencies, and traditional financial variables for gold price prediction. This research offers practical applications for investors and policymakers by offering insights into market trends, enhancing decision-making, and bridging traditional and emerging markets in financial forecasting. 03-30-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">This study presents a machine learning framework for predicting gold prices by integrating diverse financial indicators, including the NASDAQ-100 index (^NDX), Bitcoin (BTC-USD), and gold futures (GC=F). Using daily high prices from February 2020 to May 2024, the approach incorporates robust preprocessing techniques such as the Box-Cox transformation and Principal Component Analysis (PCA) to address skewness, kurtosis, and multicollinearity, to reduce dimensionality while retaining 96.37% of the variance. A Genetic Algorithm-optimized Multi-Layer Perceptron (MLP) regression model achieved high predictive accuracy with an R² score of 0.98, an RMSE of 23.48 USD, and an MAE of 17.38 USD. Permutation importance analysis highlighted PC1 and PC2 as the most significant predictors, collectively capturing over 96% of the dataset's variance. The results emphasize the effectiveness of integrating stock indices, cryptocurrencies, and traditional financial variables for gold price prediction. This research offers practical applications for investors and policymakers by offering insights into market trends, enhancing decision-making, and bridging traditional and emerging markets in financial forecasting.</span></p> ]]> A Machine Learning Approach to Gold Price Prediction Using Financial Indicators sabahudin vrtagic bachar mourched doi: 10.18280/ijcmem.130120 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 199 10.18280/ijcmem.130120 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130120 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130119 SolidWorks used an optimization approach from the authors to strengthen the structural quality of edge weld designs. The current standard approaches for edge weld analysis evaluation remain insufficiently developed which causes limitations to the functionality of SolidWorks simulation software. A modern weldment analysis procedure stands as the selected research method to predict outcomes across various conditions through weld parameter definition. The SolidWorks simulation model provides an advanced method to construct 3D frame structures with edge-welding through precise weld specifications and effective boundary definition. Standard welding processes together with analytical methods affect outcome precision because weld measurements showed differences from projected values. The design process will split weld component inspections into two separate outcomes which will distinguish between passable dimensions and those that need additional evaluation. The scientific research confirms that all structures require weld modifications whenever external forces surpass either 2000 N or 3000 N during analysis. Results show that maximum stability requires either robust welds or reduced safety procedures or better welding electrodes according to the research data. Engineers leverage this simulated platform as it helps evaluate welded structure loading patterns to improve their live design work. Virtual data processing together with actual application parameters allows engineers to build precise weld designs producing better responses predictions for modern welded frameworks in operational environments. 03-30-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">SolidWorks used an optimization approach from the authors to strengthen the structural quality of edge weld designs. The current standard approaches for edge weld analysis evaluation remain insufficiently developed which causes limitations to the functionality of SolidWorks simulation software. A modern weldment analysis procedure stands as the selected research method to predict outcomes across various conditions through weld parameter definition. The SolidWorks simulation model provides an advanced method to construct 3D frame structures with edge-welding through precise weld specifications and effective boundary definition. Standard welding processes together with analytical methods affect outcome precision because weld measurements showed differences from projected values. The design process will split weld component inspections into two separate outcomes which will distinguish between passable dimensions and those that need additional evaluation. The scientific research confirms that all structures require weld modifications whenever external forces surpass either 2000 N or 3000 N during analysis. Results show that maximum stability requires either robust welds or reduced safety procedures or better welding electrodes according to the research data. Engineers leverage this simulated platform as it helps evaluate welded structure loading patterns to improve their live design work. Virtual data processing together with actual application parameters allows engineers to build precise weld designs producing better responses predictions for modern welded frameworks in operational environments.</span></p> ]]> Optimizing Aspect Welds Size for Structural Integrity and Performance: A Simulation Approach Using SolidWorks hayder mohammed mnati ahmed hashim kareem hasan shakir majdi laith jaafer habeeb abdulghafor mohammed hashim doi: 10.18280/ijcmem.130119 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 177 10.18280/ijcmem.130119 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130119 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130118 This study focused on the effects of welding speed and power intensity on distortion and corrosion resistance for alloy steel T-joint weldments. The research was theoretical but also included practical experiments to identify thermodynamic characteristics. The study focuses on the alterations in microstructure and the ability of the weld metal to resist corrosion. Three interconnected modeling operations included structural and thermal evaluations in calculating the microstructure and the deformation of the weld joint. The heat effect zone (HAZ) width in welding speed is 5mm/sec, about 47 mm in the Y direction and 60 mm in the X direction. For 6 mm/sec welding speed, the HAZ was 25 mm in the Y direction and 29 mm in the X direction, and finally, the HAZ width for weldment with 7.5 mm/sec welding speed was 21 mm in the Y direction and 26 mm in the X direction. The highest deformation with 1.08 mm was calculated when welding with lower welding speed and the highest source power. While 0.57 mm deformation was recorded when welding with the highest welding speed and lowest source power intensity. Samples of the weld metal were tested to monitor their weightlessness and corrosion level. The results showed that the size of the HAZ increased with increasing intensities of power. Results reveal that the distortion of weld joint varies inversely with welding velocity and directly relates to power intensity. A microstructural analysis shows that the weld metal has acicular interlocking, polygonal ferrite, and side plates. Acicular ferrite amount influenced weld metal corrosion resistance decreased as power intensities increased. The microstructure of the HAZ is significantly influenced by the intensity of the welding power, which in turn affects the microhardness of the HAZ. 03-30-2025 <![CDATA[ <p>This study focused on the effects of welding speed and power intensity on distortion and corrosion resistance for alloy steel T-joint weldments. The research was theoretical but also included practical experiments to identify thermodynamic characteristics. The study focuses on the alterations in microstructure and the ability of the weld metal to resist corrosion. Three interconnected modeling operations included structural and thermal evaluations in calculating the microstructure and the deformation of the weld joint. The heat effect zone (HAZ) width in welding speed is 5mm/sec, about 47 mm in the Y direction and 60 mm in the X direction. For 6 mm/sec welding speed, the HAZ was 25 mm in the Y direction and 29 mm in the X direction, and finally, the HAZ width for weldment with 7.5 mm/sec welding speed was 21 mm in the Y direction and 26 mm in the X direction. The highest deformation with 1.08 mm was calculated when welding with lower welding speed and the highest source power. While 0.57 mm deformation was recorded when welding with the highest welding speed and lowest source power intensity. Samples of the weld metal were tested to monitor their weightlessness and corrosion level. The results showed that the size of the HAZ increased with increasing intensities of power. Results reveal that the distortion of weld joint varies inversely with welding velocity and directly relates to power intensity. A microstructural analysis shows that the weld metal has acicular interlocking, polygonal ferrite, and side plates. Acicular ferrite amount influenced weld metal corrosion resistance decreased as power intensities increased. The microstructure of the HAZ is significantly influenced by the intensity of the welding power, which in turn affects the microhardness of the HAZ.</p> ]]> Investigation of Source Power Intensity and Speed Effect on Joint Welding ouf a. shams samir a. amin haneen m. jaber mustafa a.s. mustafa doi: 10.18280/ijcmem.130118 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 165 10.18280/ijcmem.130118 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130118 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130117 Currently, weapons storage is conducted manually, employing multiple layers of security systems that are time-consuming. This system exhibits numerous vulnerabilities that jeopardize security in the oversight of weapons storage facilities. This research seeks to develop a weapon storage security system utilizing a soldier identity-based identifier and to document its usage through a web-based interface. This system incorporates the MFRC 522 RFID sensor for identification, integrated with a drop-bolt lock, Arduino Uno Ethernet shield, DC buzzer, relay module, DC jack module, and an emergency module, all connected to a web-based interface. The system undergoes testing through multiple scenarios to evaluate response time and robustness. The test results indicate that this system operates efficiently and enhances response time during the laying off and taking off weapons, as well as data recording in real-time. The system identifies the key owner and exhibits a response time of 10 seconds, whereas the web interface records a response time of under 18.2 seconds during heavy usage. 03-30-2025 <![CDATA[ <p>Currently, weapons storage is conducted manually, employing multiple layers of security systems that are time-consuming. This system exhibits numerous vulnerabilities that jeopardize security in the oversight of weapons storage facilities. This research seeks to develop a weapon storage security system utilizing a soldier identity-based identifier and to document its usage through a web-based interface. This system incorporates the MFRC 522 RFID sensor for identification, integrated with a drop-bolt lock, Arduino Uno Ethernet shield, DC buzzer, relay module, DC jack module, and an emergency module, all connected to a web-based interface. The system undergoes testing through multiple scenarios to evaluate response time and robustness. The test results indicate that this system operates efficiently and enhances response time during the laying off and taking off weapons, as well as data recording in real-time. The system identifies the key owner and exhibits a response time of 10 seconds, whereas the web interface records a response time of under 18.2 seconds during heavy usage.</p> ]]> Development of a Web-Based Weapon Rack Security System Utilizing RFID Technology and Real-Time Data Logging muhammad rizqy alfarisi patrick telnoni pramuko aji giva andriana mutiara periyadi doi: 10.18280/ijcmem.130117 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 157 10.18280/ijcmem.130117 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130117 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130116 Globally, heart disease is one of the main causes of death. Clinical data analysis is a huge problem when it comes to accurately predicting cardiovascular disease. This work presents a prediction model that makes use of numerous proven classification algorithms and different combinations of information. The goal of this work is to help in the detection of heart disease by employing a hybrid classification system depending on the Binary Harris hawks algorithm (BHHO) and the Logistic regression approach. Also, the Boruta algorithm with random forest is used and compared with the proposed PCA-BHHO algorithm. In this work, the data is first preprocessed, and missing values are filled with mean values. Then, data is scaled using standard scaler, and the proposed hybrid PCA and BHHO are applied to select the best features. RF and logistic regression are employed to classify the patients as heart disease patients or not. For comparison, Boruta is used for feature selection and RF for classification and compared the results with the proposed PCA-BHHO algorithm. Two datasets are utilized to test the proposed model: Statlog and the Cleveland heart disease datasets. The proposed PCA-BHHO algorithm attained an accuracy of 92.59% and 89.33% on the Statlog and the Cleveland datasets, respectively. At the same time, the Boruta-RF algorithm attained an accuracy of 90.14% and 87.64% on the Statlog and Cleveland datasets, respectively. 03-30-2025 <![CDATA[ <p>Globally, heart disease is one of the main causes of death. Clinical data analysis is a huge problem when it comes to accurately predicting cardiovascular disease. This work presents a prediction model that makes use of numerous proven classification algorithms and different combinations of information. The goal of this work is to help in the detection of heart disease by employing a hybrid classification system depending on the Binary Harris hawks algorithm (BHHO) and the Logistic regression approach. Also, the Boruta algorithm with random forest is used and compared with the proposed PCA-BHHO algorithm. In this work, the data is first preprocessed, and missing values are filled with mean values. Then, data is scaled using standard scaler, and the proposed hybrid PCA and BHHO are applied to select the best features. RF and logistic regression are employed to classify the patients as heart disease patients or not. For comparison, Boruta is used for feature selection and RF for classification and compared the results with the proposed PCA-BHHO algorithm. Two datasets are utilized to test the proposed model: Statlog and the Cleveland heart disease datasets. The proposed PCA-BHHO algorithm attained an accuracy of 92.59% and 89.33% on the Statlog and the Cleveland datasets, respectively. At the same time, the Boruta-RF algorithm attained an accuracy of 90.14% and 87.64% on the Statlog and Cleveland datasets, respectively.</p> ]]> Optimization Based Approach for Heart Disease Classification samah j. saba elaf a. abd al-kareem muna r. hameed doi: 10.18280/ijcmem.130116 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 149 10.18280/ijcmem.130116 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130116 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130115 Facial expression recognition (FER) remains a challenging task due to variations in facial features, occlusions, and imbalanced datasets, which often lead to misclassification of similar emotions. To address these challenges, this study proposes a hybrid Deep Autoencoder and AdaBoost model, leveraging deep feature extraction and ensemble learning to enhance classification robustness. The experimental evaluation on three benchmark datasets—MMAFEDB, AffectNet, and JAFFE—demonstrates outstanding performance, with the model achieving an AUC and Accuracy of 99.9% and 99.8% on large-scale datasets, while maintaining a strong performance of 94.9% AUC and 91.1% accuracy on smaller datasets. The confusion matrix analysis confirms the model's ability to accurately classify distinct emotions, with minor misclassifications occurring in expressions with overlapping features. These findings highlight the effectiveness of the proposed approach in improving FER accuracy, offering significant benefits for real-world applications such as human-computer interaction, emotion-aware systems, and psychological analysis, while also suggesting future enhancements through domain adaptation and refined feature extraction techniques. 03-30-2025 <![CDATA[ <p>Facial expression recognition (FER) remains a challenging task due to variations in facial features, occlusions, and imbalanced datasets, which often lead to misclassification of similar emotions. To address these challenges, this study proposes a hybrid Deep Autoencoder and AdaBoost model, leveraging deep feature extraction and ensemble learning to enhance classification robustness. The experimental evaluation on three benchmark datasets—MMAFEDB, AffectNet, and JAFFE—demonstrates outstanding performance, with the model achieving an AUC and Accuracy of 99.9% and 99.8% on large-scale datasets, while maintaining a strong performance of 94.9% AUC and 91.1% accuracy on smaller datasets. The confusion matrix analysis confirms the model's ability to accurately classify distinct emotions, with minor misclassifications occurring in expressions with overlapping features. These findings highlight the effectiveness of the proposed approach in improving FER accuracy, offering significant benefits for real-world applications such as human-computer interaction, emotion-aware systems, and psychological analysis, while also suggesting future enhancements through domain adaptation and refined feature extraction techniques. </p> ]]> Hybrid Deep Autoencoder and AdaBoost for Robust Facial Expression Recognition muhamad fatchan pulung n. andono affandy affandy ahmad zainul fanani doi: 10.18280/ijcmem.130115 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 141 10.18280/ijcmem.130115 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130115 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130114 This paper focuses on the study of the use of fused deposition modeling (FDM) in enhancing the process parameters of formed components. Three variables (fill density, layer height, and printing speed) are considered to have a significant and significant effect on the tensile strength of acrylonitrile butadiene styrene specimens. The methodology of this study is based on experiments using the Taguchi strategy. On the other hand, previous studies have mainly focused on analyzing individual process parameters and their effect on the mechanical properties of FDM-manufactured parts. The results of this study, using Taguchi techniques and analysis of variance, show that the largest and most significant effect on the tensile strength of FDM structures was the fill density among the three process parameters. ANOVA results for the average tensile strength with a confidence interval of 66.595%, while ANOVA results for the Young Modulus at a confidence interval of 36.236% and the ANOVA findings for the fractured strength at a confidence interval of 50.228%. A higher F-value indicates that adjusting a process parameter has a greater impact on performance characteristics. In addition, there is a limited effect of the other process variable with a smaller effect, but it was still effective. Finally, valuable insights could be drawn from the results about the correlation between process parameters and mechanical properties of components. The study confirms encouraging results using FDM technology for researchers and future studies in terms of enhancing the structural integrity of the produced components. 03-30-2025 <![CDATA[ <p>This paper focuses on the study of the use of fused deposition modeling (FDM) in enhancing the process parameters of formed components. Three variables (fill density, layer height, and printing speed) are considered to have a significant and significant effect on the tensile strength of acrylonitrile butadiene styrene specimens. The methodology of this study is based on experiments using the Taguchi strategy. On the other hand, previous studies have mainly focused on analyzing individual process parameters and their effect on the mechanical properties of FDM-manufactured parts. The results of this study, using Taguchi techniques and analysis of variance, show that the largest and most significant effect on the tensile strength of FDM structures was the fill density among the three process parameters. ANOVA results for the average tensile strength with a confidence interval of 66.595%, while ANOVA results for the Young Modulus at a confidence interval of 36.236% and the ANOVA findings for the fractured strength at a confidence interval of 50.228%. A higher F-value indicates that adjusting a process parameter has a greater impact on performance characteristics. In addition, there is a limited effect of the other process variable with a smaller effect, but it was still effective. Finally, valuable insights could be drawn from the results about the correlation between process parameters and mechanical properties of components. The study confirms encouraging results using FDM technology for researchers and future studies in terms of enhancing the structural integrity of the produced components.</p> ]]> Characterizing and Optimizing the Parameters of Additive Manufacturing by Fused Deposition Modeling Methods to Enhance the Product Mechanical Qualities jamal j. dawood hind b. ali rana anaee farag m. mohammed doi: 10.18280/ijcmem.130114 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 133 10.18280/ijcmem.130114 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130114 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130113 This study develops a data-driven strategy for stunting prevention using the K-Means clustering method, validated through the Elbow Method and Cluster Profiling. The high prevalence of stunting in the research area highlights the need for precise health condition mapping to prioritize effective interventions. Data collected from toddlers in the region were grouped into three distinct clusters, each representing varying levels of risk and requiring tailored prevention strategies. These interventions include contextualized preventive education, optimized based on the specific characteristics and needs of each cluster. The results demonstrate that this method accurately maps health conditions, facilitates targeted interventions, and enhances resource allocation. Additionally, the clustering approach serves as a foundation for creating impactful and relevant health counseling materials to strengthen community education. The study’s main contribution lies in providing a data-driven framework that supports evidence-based public health policy and localized stunting prevention strategies, ensuring adaptability to the unique needs of the research area. 03-30-2025 <![CDATA[ <p>This study develops a data-driven strategy for stunting prevention using the K-Means clustering method, validated through the Elbow Method and Cluster Profiling. The high prevalence of stunting in the research area highlights the need for precise health condition mapping to prioritize effective interventions. Data collected from toddlers in the region were grouped into three distinct clusters, each representing varying levels of risk and requiring tailored prevention strategies. These interventions include contextualized preventive education, optimized based on the specific characteristics and needs of each cluster. The results demonstrate that this method accurately maps health conditions, facilitates targeted interventions, and enhances resource allocation. Additionally, the clustering approach serves as a foundation for creating impactful and relevant health counseling materials to strengthen community education. The study’s main contribution lies in providing a data-driven framework that supports evidence-based public health policy and localized stunting prevention strategies, ensuring adaptability to the unique needs of the research area.</p> ]]> Stunting Incidence Segmentation: A Cluster Analysis Approach and Targeted Intervention Strategies sri mulyati delvindra faiz noorhadi hanuga fathur chaerulisma novi setiani doi: 10.18280/ijcmem.130113 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 125 10.18280/ijcmem.130113 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130113 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130112 Mobile Ad Hoc Networks (MANETs) plays an important role in various fields; however, this network unavoidably encounters difficulties at the network layer primarily owing to misbehavior or malicious nodes. Among the issues plaguing MANETs, the deliberate and accidental dropping of packets by intermediate nodes emerges as a noteworthy problem requiring attention. The work proposes a novel routing protocol that aims to mitigate the packet dropping problem in a thorough yet efficient manner by selecting only neighbors with proven stability and integrity during route discovery. The protocol devises a neighbor node election tactic reliant on residual status of energy and buffer so that it can compute stable route and avoid those neighbors in route which are having constrained energy and buffer. Additionally, it deploys counter-based authenticated acknowledgments and promiscuous monitoring to enable integrity in route and counter malicious packet drooping. Simulation results show the protocol's efficacy, consistently outperforming existing algorithms in packet delivery and energy efficiency. In conclusion, this work systematically addresses the complexities introduced packet dropping nodes in infrastructure-less networks. 03-30-2025 <![CDATA[ <p>Mobile Ad Hoc Networks (MANETs) plays an important role in various fields; however, this network unavoidably encounters difficulties at the network layer primarily owing to misbehavior or malicious nodes. Among the issues plaguing MANETs, the deliberate and accidental dropping of packets by intermediate nodes emerges as a noteworthy problem requiring attention. The work proposes a novel routing protocol that aims to mitigate the packet dropping problem in a thorough yet efficient manner by selecting only neighbors with proven stability and integrity during route discovery. The protocol devises a neighbor node election tactic reliant on residual status of energy and buffer so that it can compute stable route and avoid those neighbors in route which are having constrained energy and buffer. Additionally, it deploys counter-based authenticated acknowledgments and promiscuous monitoring to enable integrity in route and counter malicious packet drooping. Simulation results show the protocol's efficacy, consistently outperforming existing algorithms in packet delivery and energy efficiency. In conclusion, this work systematically addresses the complexities introduced packet dropping nodes in infrastructure-less networks.</p> ]]> Comprehensive Approach to Addressing Misbehaving and Unintentional Packet Drops Nodes in MANETs to Improve the Network Performance polu srinivasa reddy arshad ahmad khan mohammad doi: 10.18280/ijcmem.130112 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 115 10.18280/ijcmem.130112 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130112 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130111 The effects of adding silicon to shape memory alloy (SMA) (Nitinol) were investigated in the current investigation. Most people think that silicon-based SMAs could be a cheaper alternative to NiTi SMA because they have good shape memory properties, good damping capacity, and other useful properties. The alloys were mechanically tested for Vickers microhardness, compression force, shape memory effect (strain recovery), density, and porosity to estimate the Si effect. Powder metallurgy was used to make the alloys. The base alloy (Nitinol) was prepared after sintering treatment at a temperature of 850°C for a period of 6hr. In addition, alloys were prepared from them to find out the effect of adding silicon. These alloys included the base alloy to which silicon was added in proportions of 0%, 3%, 6%, and 9% wt. of Si as their weight ratios. The results showed that increasing the percentage of silicon resulted in improved mechanical properties while 9.0 wt.% Si showed better shape memory properties. 03-30-2025 <![CDATA[ <p>The effects of adding silicon to shape memory alloy (SMA) (Nitinol) were investigated in the current investigation. Most people think that silicon-based SMAs could be a cheaper alternative to NiTi SMA because they have good shape memory properties, good damping capacity, and other useful properties. The alloys were mechanically tested for Vickers microhardness, compression force, shape memory effect (strain recovery), density, and porosity to estimate the Si effect. Powder metallurgy was used to make the alloys. The base alloy (Nitinol) was prepared after sintering treatment at a temperature of 850°C for a period of 6hr. In addition, alloys were prepared from them to find out the effect of adding silicon. These alloys included the base alloy to which silicon was added in proportions of 0%, 3%, 6%, and 9% wt. of Si as their weight ratios. The results showed that increasing the percentage of silicon resulted in improved mechanical properties while 9.0 wt.% Si showed better shape memory properties.</p> ]]> Effect of Silicon Addition on the Characteristics of Nitinol Shape Memory Alloy abdullah d. assi salman h. omran moaz h. ali hussain ali hussain ahmed a. shandookh doi: 10.18280/ijcmem.130111 International Journal of Computational Methods and Experimental Measurements 03-30-2025 International Journal of Computational Methods and Experimental Measurements 03-30-2025 2025 13 1 Article 107 10.18280/ijcmem.130111 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130111 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130110 Optimized energy generation and smart distribution in a sustainable manner requires accurate prediction of its consumption. However, the prediction of energy demands of households remains a tedious task due to variations in patterns of energy usage. Mathematical models and artificial intelligence (AI), such as smart energy-efficient designs, strategic planning for smart grids, and Internet of Things (IoT)-enabled smart homes, have recently been considered as solutions to these issues. A major issue encountered in energy consumption prediction systems is their restricted prediction horizons, as well as their dependence on one-step predictions. This study, therefore, suggests an innovative model for the prediction of energy demand that uses a long short-term memory (LSTM) and fractional differential equations (FDLE)-based model. The proposed LSTM-FDLE model was trained to predict the collective active power generated by household devices. LSTM’s memory and sequential learning capabilities were also explored in the proposed model for comprehending the complex temporal dependencies and trends in energy consumption data. The performance of the proposed model was evaluated on real-world household energy usage data and found to achieve good prediction accuracy; the performance of the model was also better than that of some conventional one-step prediction models. Therefore, better energy generation planning, and optimal distribution systems can be achieved by the longer forecasting period provided by the proposed “LSTM” model. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Optimized energy generation and smart distribution in a sustainable manner requires accurate prediction of its consumption. However, the prediction of energy demands of households remains a tedious task due to variations in patterns of energy usage. Mathematical models and artificial intelligence (AI), such as smart energy-efficient designs, strategic planning for smart grids, and Internet of Things (IoT)-enabled smart homes, have recently been considered as solutions to these issues. A major issue encountered in energy consumption prediction systems is their restricted prediction horizons, as well as their dependence on one-step predictions. This study, therefore, suggests an innovative model for the prediction of energy demand that uses a long short-term memory (LSTM) and fractional differential equations (FDLE)-based model. The proposed LSTM-FDLE model was trained to predict the collective active power generated by household devices. LSTM’s memory and sequential learning capabilities were also explored in the proposed model for comprehending the complex temporal dependencies and trends in energy consumption data. The performance of the proposed model was evaluated on real-world household energy usage data and found to achieve good prediction accuracy; the performance of the model was also better than that of some conventional one-step prediction models. Therefore, better energy generation planning, and optimal distribution systems can be achieved by the longer forecasting period provided by the proposed “LSTM” model.</span></p> ]]> A Novel Energy Consumption Prediction Model Combining Long Short-Term Memory (LSTM) and Fractional Differential Equations (FDLE) ahlam alghanmi doi: 10.18280/ijcmem.130110 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 97 10.18280/ijcmem.130110 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130110 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130109 Shielded metal arc welding achieves copper to stainless steel joints using Cu-based and Fe-based electrodes. ANSYS and SOLIDWORKS models predicted the welding heat distribution and HAZ dimension for both welding electrodes. According to the heat distribution results, deformation and stress distribution for both models were calculated. ANSYS software was used to calculate the HAZ and fusion zone width for both sides and both electrodes; the results showed 1.9 mm on the stainless-steel side, 6.24 mm on the copper side for ECuSi, and 6.7 mm for the stainless-steel side, 7 mm for the copper side in E308 sample. The stress models illustrated higher stress on the stainless steel side for both the welding sample and in fixtures for both sides. The estimated deformation results were 0.40 and 0.48 mm for ECuSi and E308, respectively. Weld zone in Cu-based filled joint consists of uniform structure with Cu solid solution phase. Immiscible Cu and Fe mixture causes weld segregation in Fe base electrode joint. Weld zones containing a combination of phases in the Fe-based filled joints exhibit greater microhardness than the Cu-based joints. Cu-based joint achieves highest tensile value, reaching up to 80% copper tensile strength. Heat treatment causes reduction in dislocation density and increases grain size, resulting heat-affected zone (HAZ) softening on both joints copper side. This softening makes HAZ susceptible to fracture during tensile testing. Every joints fractures in ductile manner and plastic deformation is concentrated on softened copper side. Welding joint filled with Cu displays the most plastic deformation due to the significant displacement of both the welding zone and Cu base metal. This deformation primarily produced by weld high plasticity, which helps reduce stress concentration. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Shielded metal arc welding achieves copper to stainless steel joints using Cu-based and Fe-based electrodes. ANSYS and SOLIDWORKS models predicted the welding heat distribution and HAZ dimension for both welding electrodes. According to the heat distribution results, deformation and stress distribution for both models were calculated. ANSYS software was used to calculate the HAZ and fusion zone width for both sides and both electrodes; the results showed 1.9 mm on the stainless-steel side, 6.24 mm on the copper side for ECuSi, and 6.7 mm for the stainless-steel side, 7 mm for the copper side in E308 sample. The stress models illustrated higher stress on the stainless steel side for both the welding sample and in fixtures for both sides. The estimated deformation results were 0.40 and 0.48 mm for ECuSi and E308, respectively. Weld zone in Cu-based filled joint consists of uniform structure with Cu solid solution phase. Immiscible Cu and Fe mixture causes weld segregation in Fe base electrode joint. Weld zones containing a combination of phases in the Fe-based filled joints exhibit greater microhardness than the Cu-based joints. Cu-based joint achieves highest tensile value, reaching up to 80% copper tensile strength. Heat treatment causes reduction in dislocation density and increases grain size, resulting heat-affected zone (HAZ) softening on both joints copper side. This softening makes HAZ susceptible to fracture during tensile testing. Every joints fractures in ductile manner and plastic deformation is concentrated on softened copper side. Welding joint filled with Cu displays the most plastic deformation due to the significant displacement of both the welding zone and Cu base metal. This deformation primarily produced by weld high plasticity, which helps reduce stress concentration.</span></p> ]]> Electrodes Type Effects on Welding of Copper to 304 Stainless Steel and Analysis of Heat Distribution, Microstructures, and Mechanical Properties mohammed m. alkhafaji mohammed s. mohammed samir a. amin laith j. habeeb hasan s. majdi doi: 10.18280/ijcmem.130109 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 85 10.18280/ijcmem.130109 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130109 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130108 Manufacturing processes must use natural language processing (NLP) to provide a user-friendly interface for human-machine interaction. Natural language processing (NLP) presents numerous challenges in the manufacturing environments characterized by Industry 4.0, including language barriers, processing bottlenecks in real-time, and data security challenges. The research develops the Cognitive Language Real-Time Processing Optimization (CLR-TPO) method to address these problems with real-time processing limitations in Industry 4.0 human-machine interactions. The goal is to leverage parallel processing architectures and edge computing to increase communication speed. Using state-of-the-art edge computing and parallel processing architectures, CLR-TPO enhances real-time capabilities to ensure rapid and responsive machine-human interactions. Its adaptive learning abilities enable it to gain more language knowledge and adjust to different languages swiftly. Cognitive computing has the potential to fundamentally change several industrial fields, including intelligent process optimization, supply chain management, quality control, and predictive maintenance. This study explores many applications of CLR-TPO, with an emphasis on how it improves operational efficiency and manufacturing processes. The experimental results show that the proposed CLR-TPO model increases the performance rate of 98.6%, Adaptability Analysis of 97.6%, latency analysis of 14.3%, scalability ratio of 98.9%, and accuracy ratio of 96.7% compared to other existing models. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Manufacturing processes must use natural language processing (NLP) to provide a user-friendly interface for human-machine interaction. Natural language processing (NLP) presents numerous challenges in the manufacturing environments characterized by Industry 4.0, including language barriers, processing bottlenecks in real-time, and data security challenges. The research develops the Cognitive Language Real-Time Processing Optimization (CLR-TPO) method to address these problems with real-time processing limitations in Industry 4.0 human-machine interactions. The goal is to leverage parallel processing architectures and edge computing to increase communication speed. Using state-of-the-art edge computing and parallel processing architectures, CLR-TPO enhances real-time capabilities to ensure rapid and responsive machine-human interactions. Its adaptive learning abilities enable it to gain more language knowledge and adjust to different languages swiftly. Cognitive computing has the potential to fundamentally change several industrial fields, including intelligent process optimization, supply chain management, quality control, and predictive maintenance. This study explores many applications of CLR-TPO, with an emphasis on how it improves operational efficiency and manufacturing processes. The experimental results show that the proposed CLR-TPO model increases the performance rate of 98.6%, Adaptability Analysis of 97.6%, latency analysis of 14.3%, scalability ratio of 98.9%, and accuracy ratio of 96.7% compared to other existing models.</span></p> ]]> Cognitive Computing in Manufacturing: Transformative Applications of Natural Language Processing for Human-Machine Interaction in Industry 4.0 n. sudhakar yadav rajanikanth aluvalu uma maheswari viswanadhula mallellu sai prashanth pradeep kumar nagalapura shankar murthy doi: 10.18280/ijcmem.130108 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 73 10.18280/ijcmem.130108 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130108 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130107 This research explores integrating a Darrieus Vertical Axis Wind Turbine (VAWT) system to enhance speedboat energy efficiency. With the rising need for sustainable marine energy solutions, harnessing wind power through VAWT technology can reduce fuel consumption and environmental impact. The study focuses on the aerodynamic design, turbine placement, and energy output estimation under varying maritime wind conditions. Vertical-axis turbines efficiently operate without needing wind alignment, making them suitable for marine use. A VAWT was mounted on a 12-meter, four-engine speedboat, powering essential systems like spotlights and navigation. Simulations and field tests assessed power generation, stability, and drag impact. At a speed of 14 knots (7.2 m/s), the turbine produced 11.39 watts, outperforming laboratory results due to uniform wind distribution across the blades. Laboratory experiments confirmed these findings, showing an electrical output of 8.2 watts, sufficient for battery charging. Increasing the wind sweep area could further boost power while maintaining stability. The Darrieus VAWT model demonstrated effective energy harnessing at lower speeds and fuel consumption reduction, highlighting its potential for sustainable maritime applications. Future work will focus on improving material durability and developing automated wind angle adjustments for optimal performance. <![CDATA[ <p><span style="font-family: Times New Roman, serif">This research explores integrating a Darrieus Vertical Axis Wind Turbine (VAWT) system to enhance speedboat energy efficiency. With the rising need for sustainable marine energy solutions, harnessing wind power through VAWT technology can reduce fuel consumption and environmental impact. The study focuses on the aerodynamic design, turbine placement, and energy output estimation under varying maritime wind conditions. Vertical-axis turbines efficiently operate without needing wind alignment, making them suitable for marine use. A VAWT was mounted on a 12-meter, four-engine speedboat, powering essential systems like spotlights and navigation. Simulations and field tests assessed power generation, stability, and drag impact. At a speed of 14 knots (7.2 m/s), the turbine produced 11.39 watts, outperforming laboratory results due to uniform wind distribution across the blades. Laboratory experiments confirmed these findings, showing an electrical output of 8.2 watts, sufficient for battery charging. Increasing the wind sweep area could further boost power while maintaining stability. The Darrieus VAWT model demonstrated effective energy harnessing at lower speeds and fuel consumption reduction, highlighting its potential for sustainable maritime applications. Future work will focus on improving material durability and developing automated wind angle adjustments for optimal performance.</span></p> ]]> Design and Analysis of Darrieus Vertical Axis Wind Turbines as an Energy Source for Speedboat Navigation and Lighting System witono hardi rudi hartono bambang tjiroso mohamad jamil doi: 10.18280/ijcmem.130107 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 61 10.18280/ijcmem.130107 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130107 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130106 This study investigates the mechanical properties of maraging steel MS1 produced through two distinct manufacturing processes: Which include Direct Metal Laser Sintering (DMLS) and Computer Numerical Control (CNC) machining. The goal is to investigate the influence of these methods on mechanical performance and the microstructural integrity of the produced components. The strength, ductility, and fracture behavior of the specimens were evaluated under tensile testing. Results also showed that the DMLS specimen had significantly superior mechanical properties compared to the CNC machined specimen with an ultimate tensile strength of 1145.8 MPa compared to 542.45 MPa. The results indicated that the DMLS specimen withstood higher stress levels, while remaining at lower strain than that of the CNC machined specimen. Which means that the strength and coherence of the structural particles in the DMLS specimen stems from a strong degree of bonding between deposited particles of structured material. Based on fractographic analysis, the DMLS sample showed a more homogenous microstructure due to which metal atom distribution was more coherent and the CNC sample had signs of internal defects due to machining. SOLIDWORKS simulations conducted to validate the results proved to be very close to the experimental results, essentially verifying the reliability of the results. The study concludes that DMLS provides large benefits over conventional CNC machining for the production of high-performance maraging steel components and points to the feasibility of additive manufacturing in advanced engineering applications. Further, we suggest, that future research may include the following investigations to further optimize the mechanical properties of 3D printed maraging steel, including the investigation of additional processing parameters and post-processing treatments. <![CDATA[ <p><span style="font-family: Times New Roman, serif">This study investigates the mechanical properties of maraging steel MS1 produced through two distinct manufacturing processes: Which include Direct Metal Laser Sintering (DMLS) and Computer Numerical Control (CNC) machining. The goal is to investigate the influence of these methods on mechanical performance and the microstructural integrity of the produced components. The strength, ductility, and fracture behavior of the specimens were evaluated under tensile testing. Results also showed that the DMLS specimen had significantly superior mechanical properties compared to the CNC machined specimen with an ultimate tensile strength of 1145.8 MPa compared to 542.45 MPa. The results indicated that the DMLS specimen withstood higher stress levels, while remaining at lower strain than that of the CNC machined specimen. Which means that the strength and coherence of the structural particles in the DMLS specimen stems from a strong degree of bonding between deposited particles of structured material. Based on fractographic analysis, the DMLS sample showed a more homogenous microstructure due to which metal atom distribution was more coherent and the CNC sample had signs of internal defects due to machining. SOLIDWORKS simulations conducted to validate the results proved to be very close to the experimental results, essentially verifying the reliability of the results. The study concludes that DMLS provides large benefits over conventional CNC machining for the production of high-performance maraging steel components and points to the feasibility of additive manufacturing in advanced engineering applications. Further, we suggest, that future research may include the following investigations to further optimize the mechanical properties of 3D printed maraging steel, including the investigation of additional processing parameters and post-processing treatments.</span></p> ]]> Comparative Investigation of Mechanical Characteristics and Microstructure in Maraging Steel Fabricated via DMLS and CNC Techniques hasan al dabbas ibrahim m. aladwan abhishek agarwal masengo ilunga omar badran ibrahim i. ikhries doi: 10.18280/ijcmem.130106 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 53 10.18280/ijcmem.130106 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130106 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130105 The natural fibers are too weak and must be chemically treated to strengthen them. In this article, synthetic and natural fibers were used as reinforcement in epoxy resins with different weight ratios of 2%, 4%, 6%, and 8%. Different epoxy/fiber composites were used to prepare the epoxy/fiber composites. Tensile testing was used to evaluate the mechanical specifications and conditions of composite materials. The results of the study showed the importance of determining the weight ratios of the fibers added to the epoxy resin and the type of distribution. It has been concluded that the addition of fibers to the epoxy matrix improves the tensile behavior and that increasing its amount leads to an increase in the tensile strength in addition to the effect of an increase in its length. The fibers incompletely immersed in the epoxy matrix reduce the tensile behavior. Results showed that using polypropylene with a length of 6 mm will improve the tensile strength from 33.65 MPa to 64.37 MPa, while the other naturally strengthened fibers can enhance the tensile strength in different ratios, such as jute fiber and woven jute fibers. Finally, if the distribution of the fibers in the stress concentration zones is too low, there will be a reduction in the tensile behavior. The results concluded that it would be possible to use both synthetic and natural fibers as secondary fillers for the preparation of composite materials. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The natural fibers are too weak and must be chemically treated to strengthen them. In this article, synthetic and natural fibers were used as reinforcement in epoxy resins with different weight ratios of 2%, 4%, 6%, and 8%. Different epoxy/fiber composites were used to prepare the epoxy/fiber composites. Tensile testing was used to evaluate the mechanical specifications and conditions of composite materials. The results of the study showed the importance of determining the weight ratios of the fibers added to the epoxy resin and the type of distribution. It has been concluded that the addition of fibers to the epoxy matrix improves the tensile behavior and that increasing its amount leads to an increase in the tensile strength in addition to the effect of an increase in its length. The fibers incompletely immersed in the epoxy matrix reduce the tensile behavior. Results showed that using polypropylene with a length of 6 mm will improve the tensile strength from 33.65 MPa to 64.37 MPa, while the other naturally strengthened fibers can enhance the tensile strength in different ratios, such as jute fiber and woven jute fibers. Finally, if the distribution of the fibers in the stress concentration zones is too low, there will be a reduction in the tensile behavior. The results concluded that it would be possible to use both synthetic and natural fibers as secondary fillers for the preparation of composite materials.</span></p> ]]> Improving Tensile Properties of Epoxy Composite by Adding Synthetic and Reinforcement by Natural Fibers younis khalid khdir doi: 10.18280/ijcmem.130105 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 45 10.18280/ijcmem.130105 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130105 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130104 Sidewalks play a crucial role in enhancing the comfort, safety, and accessibility of pedestrians. However, their design often neglects ergonomic principles, particularly in Makassar City. This study aims to determine ergonomic sidewalk heights using a local anthropometric approach based on knee-to-floor dimensions (LL) and allowance factors. Data were collected from 16 road segments in Makassar through observation, surveys, and statistical analysis. The results revealed that the existing sidewalk heights varied between 16–34 cm, with the highest interval at 28–30 cm (34%). While 96% comply with national standards (10–30 cm), they do not fully address user comfort. By applying allowance factors, the ergonomic sidewalk heights were determined as 11.93 cm (low allowance), 23.85 cm (medium allowance), and 35.78 cm (high allowance). These findings provide essential guidelines for adaptive sidewalk design, improving pedestrian comfort, accessibility, and safety, and are relevant for developing more inclusive urban infrastructure. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Sidewalks play a crucial role in enhancing the comfort, safety, and accessibility of pedestrians. However, their design often neglects ergonomic principles, particularly in Makassar City. This study aims to determine ergonomic sidewalk heights using a local anthropometric approach based on knee-to-floor dimensions (LL) and allowance factors. Data were collected from 16 road segments in Makassar through observation, surveys, and statistical analysis. The results revealed that the existing sidewalk heights varied between 16–34 cm, with the highest interval at 28–30 cm (34%). While 96% comply with national standards (10–30 cm), they do not fully address user comfort. By applying allowance factors, the ergonomic sidewalk heights were determined as 11.93 cm (low allowance), 23.85 cm (medium allowance), and 35.78 cm (high allowance). These findings provide essential guidelines for adaptive sidewalk design, improving pedestrian comfort, accessibility, and safety, and are relevant for developing more inclusive urban infrastructure.</span></p> ]]> Study of Flexibility Factors in Determining the Design of Ergonomic Urban Pedestrian Sidewalk Facilities ahmad hanafie andi haslindah m. ansyar bora ramadhan yusuf larisang sanusi abdul hamid doi: 10.18280/ijcmem.130104 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 35 10.18280/ijcmem.130104 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130104 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130103 With the continuous advancement of global information technology, the semiconductor industry has become a cornerstone of the world economy. The complexity and high interdependence of the semiconductor supply chain make its management and optimization a challenging task, particularly in achieving collaborative decision-making across different tiers of suppliers. Traditional research in supply chain management has largely focused on optimizing single-tier suppliers or partial segments of the supply chain, lacking a comprehensive analysis and optimization of multi-tier supplier collaboration. To address this challenge, this study proposes an optimization model based on a three-tier management and collaborative decision-making framework within the semiconductor supply chain. The model captures the intricate collaborative relationships among upstream raw material suppliers, midstream manufacturers, and downstream distributors, aiming to enhance the overall efficiency and responsiveness of the supply chain through coordinated multi-tier decision-making. Existing studies on semiconductor supply chains predominantly emphasize static or localized optimization, often neglecting the dynamic nature of supply chains and lacking systematic research on information sharing and coordination mechanisms. Moreover, these approaches frequently suffer from excessive simplification, inadequate adaptability to dynamic changes, and poor real-world applicability. To overcome these limitations, this paper develops and solves a collaborative optimization model covering three key supply chain tiers and introduces a dynamic framework for adjusting decisions across all tiers of suppliers. The results demonstrate that the proposed model significantly improves overall supply chain coordination, reduces the impact of uncertainties, and enhances both economic performance and market competitiveness. <![CDATA[ <p><span style="font-family: Times New Roman, serif">With the continuous advancement of global information technology, the semiconductor industry has become a cornerstone of the world economy. The complexity and high interdependence of the semiconductor supply chain make its management and optimization a challenging task, particularly in achieving collaborative decision-making across different tiers of suppliers. Traditional research in supply chain management has largely focused on optimizing single-tier suppliers or partial segments of the supply chain, lacking a comprehensive analysis and optimization of multi-tier supplier collaboration. To address this challenge, this study proposes an optimization model based on a three-tier management and collaborative decision-making framework within the semiconductor supply chain. The model captures the intricate collaborative relationships among upstream raw material suppliers, midstream manufacturers, and downstream distributors, aiming to enhance the overall efficiency and responsiveness of the supply chain through coordinated multi-tier decision-making. Existing studies on semiconductor supply chains predominantly emphasize static or localized optimization, often neglecting the dynamic nature of supply chains and lacking systematic research on information sharing and coordination mechanisms. Moreover, these approaches frequently suffer from excessive simplification, inadequate adaptability to dynamic changes, and poor real-world applicability. To overcome these limitations, this paper develops and solves a collaborative optimization model covering three key supply chain tiers and introduces a dynamic framework for adjusting decisions across all tiers of suppliers. The results demonstrate that the proposed model significantly improves overall supply chain coordination, reduces the impact of uncertainties, and enhances both economic performance and market competitiveness.</span></p> ]]> Development of a Multi-Tier Collaborative Optimization Model for Semiconductor Supply Chain Management boqing li doi: 10.18280/ijcmem.130103 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 22 10.18280/ijcmem.130103 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130103 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130102 Atherosclerosis is a major risk factor for cardiovascular diseases, and its diagnosis is crucial at an early stage. carotid ultrasonography is the current primary diagnostic method for atherosclerosis. However, carotid ultrasonography has problems in the early detection and evaluation of the mechanical properties of the arterial wall. To address these issues, waveform analysis focusing on pulse wave propagation has garnered attention. Despite its potential, few studies have performed pulse wave separation in an environment where pulse waves interfere with each other, as in vivo, and evaluated the reflected waveforms using three-dimensional fluid–structure interaction (FSI) analysis. In this study, pulse wave propagation was reproduced to investigate the relationship between local changes in the mechanical properties of the arterial wall and the reflected waveforms. Using a three-dimensional cylindrical model, coupled FSI analysis was performed with commercial codes by Altair. The results showed that an increase in Young’s modulus amplified the reflected wave amplitudes and elongated the wavelengths. The results also showed trends similar to the theoretical reflection coefficients, particularly for larger changes in Young’s modulus, which closely aligned with the theoretical values. These findings indicate that evaluating reflected waves can lead to estimating the local mechanical properties of the arterial walls. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Atherosclerosis is a major risk factor for cardiovascular diseases, and its diagnosis is crucial at an early stage. carotid ultrasonography is the current primary diagnostic method for atherosclerosis. However, carotid ultrasonography has problems in the early detection and evaluation of the mechanical properties of the arterial wall. To address these issues, waveform analysis focusing on pulse wave propagation has garnered attention. Despite its potential, few studies have performed pulse wave separation in an environment where pulse waves interfere with each other, as in vivo, and evaluated the reflected waveforms using three-dimensional fluid–structure interaction (FSI) analysis. In this study, pulse wave propagation was reproduced to investigate the relationship between local changes in the mechanical properties of the arterial wall and the reflected waveforms. Using a three-dimensional cylindrical model, coupled FSI analysis was performed with commercial codes by Altair. The results showed that an increase in Young’s modulus amplified the reflected wave amplitudes and elongated the wavelengths. The results also showed trends similar to the theoretical reflection coefficients, particularly for larger changes in Young’s modulus, which closely aligned with the theoretical values. These findings indicate that evaluating reflected waves can lead to estimating the local mechanical properties of the arterial walls.</span></p> ]]> Effects of the Local Changes in the Mechanical Properties of the Blood Vessel Wall on Pulse Waveforms: A Fluid–Structure Interaction Analysis yuto sato tomohiro fukui doi: 10.18280/ijcmem.130102 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 15 10.18280/ijcmem.130102 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130102 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130101 This study presents a numerical investigation of a steady, two-dimensional, incompressible turbulent flow with forced convection along a small channel with corrugated walls in a trapezoidal shape. The objective of this study is to evaluate the effect of corrugation geometry on the heat transfer rate and pressure drop through the channel. The constructal design method was applied to the geometry domain with two constraints: the total area of the channel and the area of the trapezoidal corrugation upstream of the channel. Two degrees of freedom are considered: the ratio of the smaller base to the larger base of the upstream trapezoidal corrugation (LA2/LA1) and the ratio of the trapezoid’s height to its larger base (H1/LA1). All cases were simulated for convective flows with Reynolds and Prandtl numbers of ReD = 22,000 and Pr = 0.71, respectively. The time-averaged mass, momentum, and energy conservation equations are solved using the Finite Volume Method with the RANS (Reynolds-Averaged Navier-Stokes) turbulence model and the k-ω SST (Shear Stress Transport) turbulence closure model. The results indicate that a specific H1/LA1 ratio improves the heat transfer rate by 26.2% compared to the worst case for the same LA2/LA1 ratio. Furthermore, larger insertions of trapezoidal corrugations at the bottom of the channel enhance the thermal performance of the heat exchanger, while the insertion of corrugations at the upper part of the channel has a negligible effect on heat transfer performance. From a fluid dynamic perspective, smaller insertions in the fluid flow direction led to lower pressure losses. <![CDATA[ <p><span style="font-family: Times New Roman, serif">This study presents a numerical investigation of a steady, two-dimensional, incompressible turbulent flow with forced convection along a small channel with corrugated walls in a trapezoidal shape. The objective of this study is to evaluate the effect of corrugation geometry on the heat transfer rate and pressure drop through the channel. The constructal design method was applied to the geometry domain with two constraints: the total area of the channel and the area of the trapezoidal corrugation upstream of the channel. Two degrees of freedom are considered: the ratio of the smaller base to the larger base of the upstream trapezoidal corrugation (</span><em><span style="font-family: Times New Roman, serif">LA</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif">/LA</span>_{<span style="font-family: Times New Roman, serif">1</span>}</em><span style="font-family: Times New Roman, serif">) and the ratio of the trapezoid’s height to its larger base (</span><em><span style="font-family: Times New Roman, serif">H</span>_{<span style="font-family: Times New Roman, serif">1</span>}<span style="font-family: Times New Roman, serif">/LA</span>_{<span style="font-family: Times New Roman, serif">1</span>}</em><span style="font-family: Times New Roman, serif">). All cases were simulated for convective flows with Reynolds and Prandtl numbers of </span><em><span style="font-family: Times New Roman, serif">Re</span>_{<span style="font-family: Times New Roman, serif">D</span>}</em><span style="font-family: Times New Roman, serif"> = 22,000 and </span><em><span style="font-family: Times New Roman, serif">Pr</span></em><span style="font-family: Times New Roman, serif"> = 0.71, respectively. The time-averaged mass, momentum, and energy conservation equations are solved using the Finite Volume Method with the RANS (Reynolds-Averaged Navier-Stokes) turbulence model and the </span><em><span style="font-family: Times New Roman, serif">k</span></em><span style="font-family: Times New Roman, serif">-</span><em><span style="font-family: Times New Roman, serif">ω</span></em><span style="font-family: Times New Roman, serif"> SST (Shear Stress Transport) turbulence closure model. The results indicate that a specific </span><em><span style="font-family: Times New Roman, serif">H</span>_{<span style="font-family: Times New Roman, serif">1</span>}<span style="font-family: Times New Roman, serif">/LA</span>_{<span style="font-family: Times New Roman, serif">1</span>}</em><span style="font-family: Times New Roman, serif"> ratio improves the heat transfer rate by 26.2% compared to the worst case for the same </span><em><span style="font-family: Times New Roman, serif">LA</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif">/LA</span>_{<span style="font-family: Times New Roman, serif">1</span>}</em><span style="font-family: Times New Roman, serif"> ratio. Furthermore, larger insertions of trapezoidal corrugations at the bottom of the channel enhance the thermal performance of the heat exchanger, while the insertion of corrugations at the upper part of the channel has a negligible effect on heat transfer performance. From a fluid dynamic perspective, smaller insertions in the fluid flow direction led to lower pressure losses.</span></p> ]]> Geometrical Analysis of Heat Transfer in a Corrugated Channels Heat Exchanger under Forced Convection and Turbulent Flow youssef bandeira el halal giulio lorenzini giovani dambros telli rafael adriano alves camargo gonçalves liércio andré isoldi luiz alberto oliveira rocha elizaldo domingues dos santos doi: 10.18280/ijcmem.130101 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2025 13 1 Article 1 10.18280/ijcmem.130101 https://www.acadlore.com/article/IJCMEM/2025_13_1/ijcmem.130101 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120414 A new technique for refining grains and creating surface composite materials was created using friction stir processing (FSP), which shows promise for improving the properties of metals. This technology can effectively overcome the limitations of methods that depend on melting. The work employed stir casting to produce in-situ composites, including an Al3Ni reinforcing phase, Al alloy A356, and 15% weight percent pure Ni powder. The development of several phases of Al3Ni, AlNi, and Al3Ni2, which are dispersed throughout the matrix of A356 alloy, was verified by XRD analytical examination. The objective was to determine how FSP impacted the stir-cast A356/Al3Ni in-situ composite's mechanical properties and microstructure. Porosity was successfully reduced, the α-Al dendrites were refined, the main Si phase and Al3Ni were broken and fragmented, and the grain structure was improved by the FSP method. There was a consistent and equal distribution of in-situ Al3Ni in the stir zone (SZ). There were no hazardous phases present when the particle and matrix came into contact. The application of FSP improved the tensile strength of the A356 alloy by 38.35% and the in-situ composite A356/Al3Ni by 69.17%. It was found that the improvement in hardness was 14.47% for A356 alloy after FSP and 13.81% for in-situ composite A356/Al3Ni compared to in-situ composite without FSP. <![CDATA[ <p><span style="font-family: Times New Roman, serif">A new technique for refining grains and creating surface composite materials was created using friction stir processing (FSP), which shows promise for improving the properties of metals. This technology can effectively overcome the limitations of methods that depend on melting. The work employed stir casting to produce in-situ composites, including an Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni reinforcing phase, Al alloy A356, and 15% weight percent pure Ni powder. The development of several phases of Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni, AlNi, and Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif">, which are dispersed throughout the matrix of A356 alloy, was verified by XRD analytical examination. The objective was to determine how FSP impacted the stir-cast A356/Al3Ni in-situ composite's mechanical properties and microstructure. Porosity was successfully reduced, the α-Al dendrites were refined, the main Si phase and Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni were broken and fragmented, and the grain structure was improved by the FSP method. There was a consistent and equal distribution of in-situ Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni in the stir zone (SZ). There were no hazardous phases present when the particle and matrix came into contact. The application of FSP improved the tensile strength of the A356 alloy by 38.35% and the in-situ composite A356/Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni by 69.17%. It was found that the improvement in hardness was 14.47% for A356 alloy after FSP and 13.81% for in-situ composite A356/Al</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">Ni compared to in-situ composite without FSP.</span></p> ]]> Effect of Friction Stir Processing on Microstructure and Mechanical Properties of In-Situ Composite A356/Al3Ni Fabricated by Stir Casting noor alhuda baheer muna khethier abbass israa abd al-kadir aziz doi: 10.18280/ijcmem.120414 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2024 12 4 Article 453 10.18280/ijcmem.120414 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120414 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120413 The advancement of technology within the manufacturing sector continually accelerates, frequently resulting in heightened consumer demand driven by enhancements in product quality, including consistency and quality control. This study endeavors to enhance the production process by leveraging reverse engineering alongside Indonesian anthropometry methods. The findings demonstrate that the resultant products can effectively meet customer requirements, exhibiting durability and resilience against wear and tear. By integrating reverse engineering techniques and Indonesian anthropometry methods into the production process, manufacturers can achieve greater precision and tailor products to better suit consumer needs. This approach not only enhances product quality but also contributes to increased customer satisfaction and loyalty. Furthermore, it underscores the importance of incorporating innovative methodologies to keep pace with the evolving demands of the market and to ensure continued success within the manufacturing industry. As technology continues to advance, embracing methodologies like reverse engineering and anthropometry will be crucial for manufacturers seeking to remain competitive and deliver products that surpass consumer expectations in terms of durability, performance, and overall quality. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The advancement of technology within the manufacturing sector continually accelerates, frequently resulting in heightened consumer demand driven by enhancements in product quality, including consistency and quality control. This study endeavors to enhance the production process by leveraging reverse engineering alongside Indonesian anthropometry methods. The findings demonstrate that the resultant products can effectively meet customer requirements, exhibiting durability and resilience against wear and tear. By integrating reverse engineering techniques and Indonesian anthropometry methods into the production process, manufacturers can achieve greater precision and tailor products to better suit consumer needs. This approach not only enhances product quality but also contributes to increased customer satisfaction and loyalty. Furthermore, it underscores the importance of incorporating innovative methodologies to keep pace with the evolving demands of the market and to ensure continued success within the manufacturing industry. As technology continues to advance, embracing methodologies like reverse engineering and anthropometry will be crucial for manufacturers seeking to remain competitive and deliver products that surpass consumer expectations in terms of durability, performance, and overall quality.</span></p> ]]> Experimental Study of Adaptive Jig Development to Facilitate Metal Welding Learning m. ansyar bora meylia vivi putri aulia agung dermawan ririt dwiputri permatasari larisang harry robertson panggabean doi: 10.18280/ijcmem.120413 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 441 10.18280/ijcmem.120413 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120413 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120412 Traffic congestion is a significant challenge in Lagos State, Nigeria. Existing methods rely on limited data sources and simplistic models that fail to capture the complexities of traffic dynamics in a congested urban environment. This study focused on traffic intensity detection in Lagos State using a Bayesian estimation model. Data was obtained from the Kaggle website which involved observing the number of vehicles intersecting junctions at various times of the day for a week. The model captured both spatial and temporal variations, providing real-time estimations of traffic congestion levels across different road segments. Comparative analysis with existing traffic estimation methods showed superior performance in terms of accuracy and reliability. The Gaussian Naive Bayes model achieved a high accuracy of 96% and balanced f1-score of 96%, precision of 0.96, and recall of approximately 0.96. On the other hand, the multinomial Naive Bayes model achieved an accuracy of 69% with a lower f1-score of 69%, precision of 0.67, and recall of 0.69. The model's capacity to provide accurate real-time site traffic facts can significantly contribute to effective traffic control and concrete making plans initiatives. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Traffic congestion is a significant challenge in Lagos State, Nigeria. Existing methods rely on limited data sources and simplistic models that fail to capture the complexities of traffic dynamics in a congested urban environment. This study focused on traffic intensity detection in Lagos State using a Bayesian estimation model. Data was obtained from the Kaggle website which involved observing the number of vehicles intersecting junctions at various times of the day for a week. The model captured both spatial and temporal variations, providing real-time estimations of traffic congestion levels across different road segments. Comparative analysis with existing traffic estimation methods showed superior performance in terms of accuracy and reliability. The Gaussian Naive Bayes model achieved a high accuracy of 96% and balanced f1-score of 96%, precision of 0.96, and recall of approximately 0.96. On the other hand, the multinomial Naive Bayes model achieved an accuracy of 69% with a lower f1-score of 69%, precision of 0.67, and recall of 0.69. The model's capacity to provide accurate real-time site traffic facts can significantly contribute to effective traffic control and concrete making plans initiatives.</span></p> ]]> Traffic Intensity Detection in Lagos State Using Bayesian Estimation Model aaron a. izang seun o. arowosegbe oluwabukola f. ajayi aderonke adegbenjo onome b. ohwo afolarin i. amusa wumi s. ajayi alfred a. udosen doi: 10.18280/ijcmem.120412 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 429 10.18280/ijcmem.120412 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120412 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120411 Hand gesture recognition is a technology that enables computers to interpret and understand hand movements and gestures made by users. It has various applications across various domains, including human-computer interaction, gaming, virtual reality, sign language interpretation, and robotics. Hand recognition faces challenges such as lighting conditions, occlusions, and variations in hand shape and size. Creating reliable and precise recognition systems frequently necessitates tackling these issues. Neural Architecture Search (NAS) is a technique employed in deep learning and artificial intelligence to automate the creation and optimization of neural network topologies. The objective of NAS is to identify neural network designs that are optimally aligned with certain objectives, including image classification, natural language processing, or reinforcement learning while reducing the necessity for manual design and adjustment. YOLONAS model's integration of YOLO's speed and efficiency with NAS-driven optimization results in improved accuracy and performance in gesture recognition tasks, making it a compelling choice for real-time applications requiring accurate and efficient gesture analysis. In this research, we implement YOLO with NAS technology and training with the Oxford Hand Dataset. Performance metrics are employed for monitoring and quantifying important data, such as the number of Giga Floating Point Operations Per Second (GFLOPS), the mean average precision (mAP), and the time taken for detection. The results of our study indicate that the utilization of YOLONAS with a training time of 100 epochs produces a more reliable output when compared to other approaches. 12-26-2024 <![CDATA[ <p><span style="font-family: Times, serif">Hand gesture recognition is a technology that enables computers to interpret and understand hand movements and gestures made by users. It has various applications across various domains, including human-computer interaction, gaming, virtual reality, sign language interpretation, and robotics. Hand recognition faces challenges such as lighting conditions, occlusions, and variations in hand shape and size. </span><span style="font-family: Times New Roman, serif">Creating reliable and precise recognition systems frequently necessitates tackling these issues. Neural Architecture Search (NAS) is a technique employed in deep learning and artificial intelligence to automate the creation and optimization of neural network topologies. The objective of NAS is to identify neural network designs that are optimally aligned with certain objectives, including image classification, natural language processing, or reinforcement learning while reducing the necessity for manual design and adjustment. </span><span style="font-family: Times, serif">YOLONAS model's integration of YOLO's speed and efficiency with NAS-driven optimization results in improved accuracy and performance in gesture recognition tasks, making it a compelling choice for real-time applications requiring accurate and efficient gesture analysis. In this research, we implement YOLO with NAS technology and training with the Oxford Hand Dataset. Performance metrics are employed for monitoring and quantifying important data, such as the number of Giga Floating Point Operations Per Second (GFLOPS), the mean average precision (mAP), and the time taken for detection. The results of our study indicate that the utilization of YOLONAS with a training time of 100 epochs produces a more reliable output when compared to other approaches.</span></p> ]]> Accurate Hand Recognition with Neural Architecture Search Technology christine dewi yesicca nataliani theophilus wellem hanna prillysca chernovita ramos somya henoch juli christanto lanyta setyani gunawan rio arya andika raynaldo doi: 10.18280/ijcmem.120411 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 421 10.18280/ijcmem.120411 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120411 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120410 Sarcasm detection is challenging in sentiment analysis, especially for morphologically complex languages like Telugu. Sarcastic statements often use positive words to convey negative sentiments, complicating automated interpretation. Existing sarcasm detection systems predominantly cater to English, leaving a gap for low-resource languages such as Hindi, Telugu, Tamil, Arabic, and others. This study fills this gap by creating and annotating a Telugu conversational dataset, which includes both standard and sarcastic responses. We employed two deep learning models—Self Attention-based Recurrent Neural Network (SA-RNN) and Gated Recurrent Unit (GRU)—to analyze this dataset. Results showed that the SA-RNN model outperformed the GRU, achieving 96% accuracy compared to 94%. The models utilized GloVe word embeddings and specific linguistic features, such as interjections and punctuation marks, to improve sarcasm detection. This research advances the field of sarcasm detection for low-resource languages, particularly Telugu. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Sarcasm detection is challenging in sentiment analysis, especially for morphologically complex languages like Telugu. Sarcastic statements often use positive words to convey negative sentiments, complicating automated interpretation. Existing sarcasm detection systems predominantly cater to English, leaving a gap for low-resource languages such as Hindi, Telugu, Tamil, Arabic, and others. This study fills this gap by creating and annotating a Telugu conversational dataset, which includes both standard and sarcastic responses. We employed two deep learning models—Self Attention-based Recurrent Neural Network (SA-RNN) and Gated Recurrent Unit (GRU)—to analyze this dataset. Results showed that the SA-RNN model outperformed the GRU, achieving 96% accuracy compared to 94%. The models utilized GloVe word embeddings and specific linguistic features, such as interjections and punctuation marks, to improve sarcasm detection. This research advances the field of sarcasm detection for low-resource languages, particularly Telugu.</span></p> ]]> Enhanced Sarcasm Detection in Telugu Dialogue Systems Using Self Attention-Based RNN and Gated Recurrent Unit Models bhargavi vemala m. humera khanam doi: 10.18280/ijcmem.120410 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 411 10.18280/ijcmem.120410 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120410 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120409 In order to minimize trial-and-error costs and avoid any faults throughout the production process, sheet metal forming is commonly used in the automotive industry to fabricate body pieces. This study examines how several punch models affect thinning and wrinkling during the deep drawing of aluminum 1050, a 2.50 mm thick material, under 150 KN of pressure. The Forming Limit Diagram (FLD) was used in the simulations to study material deformation and determine safe and essential places on the blank. According to the findings, die pressure-induced material stretching caused the material to significantly rise in major-minor strain, major-minor stress, thinning, and wrinkling by the fifth step. Additionally, for punch 1 material, the safe area grew from 9.20% to 49.36%; punch 2 increased from 9.08% to 46.85%. The non-linear FLD graph analysis verified that both materials stayed in the safe zone the entire time. These results demonstrate how well deep drawing simulations work to improve punch design and aluminum component performance in the automobile industry. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">In order to minimize trial-and-error costs and avoid any faults throughout the production process, sheet metal forming is commonly used in the automotive industry to fabricate body pieces. This study examines how several punch models affect thinning and wrinkling during the deep drawing of aluminum 1050, a 2.50 mm thick material, under 150 KN of pressure. The Forming Limit Diagram (FLD) was used in the simulations to study material deformation and determine safe and essential places on the blank. According to the findings, die pressure-induced material stretching caused the material to significantly rise in major-minor strain, major-minor stress, thinning, and wrinkling by the fifth step. Additionally, for punch 1 material, the safe area grew from 9.20% to 49.36%; punch 2 increased from 9.08% to 46.85%. The non-linear FLD graph analysis verified that both materials stayed in the safe zone the entire time. These results demonstrate how well deep drawing simulations work to improve punch design and aluminum component performance in the automobile industry.</span></p> ]]> Investigating Thinning and Wrinkling in Deep Drawing Processes: A Comparative Analysis of Two Punch Designs on 2.5 mm Aluminum Sheets agus dwi anggono masyrukan masyrukan agus hariyanto farid royani farid firmansyah ahmad avivudin crismansyah doi: 10.18280/ijcmem.120409 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 403 10.18280/ijcmem.120409 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120409 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120408 This work analyzes and studies the characteristics of three enclosures on a university Campus, which present similar challenges in terms of noise pollution. To carry out an empirical and objective assessment on their acoustic performance, current regulations, and standards, are being used. Theoretical calculations are considered to calculate reverberation time parameters. In order to calculate reverberation time by using the Sabine formula, it is necessary to measure the classrooms, together with the specification of the surface occupied by each of the materials that make up the walls in the rooms under study, resulting in a T60 of between 3.6 s to 6.2 s for classrooms 11 and 12, and between 4.1 s to 7.1 s for classroom 15. To obtain the parameters that define the acoustic capacities of reverberation of the rooms, the guidelines for both measurement and calculation conditions specified in the regulations are followed. Graphical representation and mathematical calculation software are used to achieve the desired results, obtaining a T60 of between 1.8 s to 2.2 s for classroom 11, 2.0 s to 3.0 s for classroom 12, and 1.7 s to 2.7 s for classroom 15. Once the acoustic conditions of the reverberation of the room are defined, it is concluded that none of the rooms has the proper characteristics to carry out the best teaching activities in them, since they exceed the recommended 0.7 s of reverberation time, since they hinder the understanding of speech and the clarity of the word. As a conclusion, the study has served as an analysis of a challenging task in the Miguelete Campus of the Universidad Nacional de San Martin, always based on parameters commonly used in the world of acoustic pollution, both scientifically and legislatively. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">This work analyzes and studies the characteristics of three enclosures on a university Campus, which present similar challenges in terms of noise pollution. To carry out an empirical and objective assessment on their acoustic performance, current regulations, and standards, are being used. Theoretical calculations are considered to calculate reverberation time parameters. In order to calculate reverberation time by using the Sabine formula, it is necessary to measure the classrooms, together with the specification of the surface occupied by each of the materials that make up the walls in the rooms under study, resulting in a T60 of between 3.6 s to 6.2 s for classrooms 11 and 12, and between 4.1 s to 7.1 s for classroom 15. To obtain the parameters that define the acoustic capacities of reverberation of the rooms, the guidelines for both measurement and calculation conditions specified in the regulations are followed. Graphical representation and mathematical calculation software are used to achieve the desired results, obtaining a T60 of between 1.8 s to 2.2 s for classroom 11, 2.0 s to 3.0 s for classroom 12, and 1.7 s to 2.7 s for classroom 15. Once the acoustic conditions of the reverberation of the room are defined, it is concluded that none of the rooms has the proper characteristics to carry out the best teaching activities in them, since they exceed the recommended 0.7 s of reverberation time, since they hinder the understanding of speech and the clarity of the word. As a conclusion, the study has served as an analysis of a challenging task in the Miguelete Campus of the Universidad Nacional de San Martin, always based on parameters commonly used in the world of acoustic pollution, both scientifically and legislatively.</span></p> ]]> Noise Pollution Challenges in University Classrooms: An Empirical Analysis of Acoustic Performance Standards albert giménez arnal javier guevara pedro facundo iriso maría claudia abeledo doi: 10.18280/ijcmem.120408 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 395 10.18280/ijcmem.120408 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120408 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120407 The analyzing of friction stir welding is applied to AA6061 with AA5083 using design of experiment (DOE) in Minitab to get optimization of the tensile strength. The analyzing was achieved by varying the main parameters as rotational speed by the values 700, 1050, and 1400 R.P.M, linear velocity of 40, 60, and 80 mm/min and pin depth of 3.5, 3.6, and 3.7 mm less than thickness material weld. A total of 11 runs were included corresponding to the designated experimental design. Analysis of variance (ANOVA) software was used to procedure for full factorial design with 1 replicate and 3 center points analysis. The results clarified that the rotational speed parameter is more significant to be controlled rather than the linear velocity and pin depth of tool. Decreasing rotational speed and increasing linear velocity and pin depth led to higher tensile strength. The profiles welded at 700 RPM, 80 mm/min and 3.7 mm had achieved the optimum case to get the value of maximum tensile strength. It is concluded that the rotational speed was the key parameter that manipulate the tensile strength in friction stir welding applied to AA6061 with AA508. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The analyzing of friction stir welding is applied to AA6061 with AA5083 using design of experiment (DOE) in Minitab to get optimization of the tensile strength. The analyzing was achieved by varying the main parameters as </span><span>rotational speed </span>by the values 700, 1050, and 1400 R.P.M, <span>linear velocity </span>of 40, 60, and 80 mm/min and pin depth of 3.5, 3.6, and 3.7 mm less than thickness material weld. A total of 11 runs were included corresponding to the designated experimental design. Analysis of variance (ANOVA) software was used to procedure for full factorial design with 1 replicate and 3 center points analysis. The results clarified that the rotational speed parameter is more significant to be controlled rather than the linear velocity and pin depth of tool. Decreasing rotational speed and increasing linear velocity and pin depth led to higher tensile strength. The profiles welded at 700 RPM, 80 mm/min and 3.7<span style="font-family: Times New Roman, serif"> mm had achieved the optimum case to get the value of maximum tensile strength. It is concluded that the rotational speed was the key parameter that manipulate the tensile strength in friction stir welding applied to AA6061 with AA508.</span></p> ]]> Analysis of Tensile Strength of Friction Stir Welding for Aluminum Alloys AA6061 with AA5083 Using Design of Experiment Approach mohammed h. rady wazir h. khalafe rand j. jadoau sandip a. kale shazarel shamsudin doi: 10.18280/ijcmem.120407 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 389 10.18280/ijcmem.120407 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120407 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120406 The misleading reviews posted on shopping websites and other media platforms sway the opinions and decisions of different customers. On the other hand, dishonest reviewers will make an effort to mimic the writing style of legitimate reviews. There is no guarantee that these text-feature-based approaches will work anytime soon. In addition, the likelihood of an imbalanced category distribution in practice limits detection performance. This paper proposes a fraudulent review detection system that uses ensemble feature selection and multidimensional feature creation to overcome these limitations. Our idea builds three-dimensional characteristics, which include text, reviewer behaviour, and misleading scores. Furthermore, a data resampling approach combines Random Sampling and oversampling techniques to mitigate the effects of an imbalanced distribution of categories. In addition, we combine the outcomes of several feature selection methods that focus on information gain, XGBoost feature importance, and the Chi-square test. On various text datasets, the proposed technique demonstrates exemplary performance in fraudulent review identification according to the experimental findings using feature selection methods, resampling methods, classification, etc. Our technique outperforms existing sophisticated methods when faced with low-quality text or an imbalanced dataset. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The misleading reviews posted on shopping websites and other media platforms sway the opinions and decisions of different customers. On the other hand, dishonest reviewers will make an effort to mimic the writing style of legitimate reviews. There is no guarantee that these text-feature-based approaches will work anytime soon. In addition, the likelihood of an imbalanced category distribution in practice limits detection performance. This paper proposes a fraudulent review detection system that uses ensemble feature selection and multidimensional feature creation to overcome these limitations. Our idea builds three-dimensional characteristics, which include text, reviewer behaviour, and misleading scores. Furthermore, a data resampling approach combines Random Sampling and oversampling techniques to mitigate the effects of an imbalanced distribution of categories. In addition, we combine the outcomes of several feature selection methods that focus on information gain, XGBoost feature importance, and the Chi-square test. On various text datasets, the proposed technique demonstrates exemplary performance in fraudulent review identification according to the experimental findings using feature selection methods, resampling methods, classification, etc. Our technique outperforms existing sophisticated methods when faced with low-quality text or an imbalanced dataset.</span></p> ]]> Identification of Misleading Reviews from Textual Content Using Feature Structure with Machine Learning Model md sirajul huque v. kiran kumar doi: 10.18280/ijcmem.120406 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 379 10.18280/ijcmem.120406 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120406 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120405 Epilepsy seizures are complex neurological phenomena marked by recurrent and unpredictable seizures that can greatly affect an individual’s quality of life. It affects millions of people worldwide. The exact and timely detection of epileptic seizures is crucial in the management and treatment of epilepsy. Many methods have been put forth recently for the diagnosis of epileptic seizures using magnetic resonance imaging (MRI) and electroencephalography (EEG). This work focuses on using deep learning and machine learning techniques, such as Support Vector Machines (SVMs), Recurrent Neural Networks (RNNs), and Convolutional Neural Networks (CNNs), to automatically identify epileptic seizures. These techniques have shown promising results in a variety of fields, including time series data processing and medical image analysis. In this work, we present a unique method for detecting epileptic seizures using electroencephalogram (EEG) data by comparing the outcomes of three deep learning architectures: SVM, CNN, and RNN-LSTM (Long-short term memory). The experimental results demonstrate that the SVM, CNN and RNN-LSTM models exhibit promising performance in detecting epileptic seizures from EEG data. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Epilepsy seizures are complex neurological phenomena marked by recurrent and unpredictable seizures that can greatly affect an individual’s quality of life. It affects millions of people worldwide. The exact and timely detection of epileptic seizures is crucial in the management and treatment of epilepsy. Many methods have been put forth recently for the diagnosis of epileptic seizures using magnetic resonance imaging (MRI) and electroencephalography (EEG). This work focuses on using deep learning and machine learning techniques, such as Support Vector Machines (SVMs), Recurrent Neural Networks (RNNs), and Convolutional Neural Networks (CNNs), to automatically identify epileptic seizures. These techniques have shown promising results in a variety of fields, including time series data processing and medical image analysis. In this work, we present a unique method for detecting epileptic seizures using electroencephalogram (EEG) data by comparing the outcomes of three deep learning architectures: SVM, CNN, and RNN-LSTM (Long-short term memory). The experimental results demonstrate that the SVM, CNN and RNN-LSTM models exhibit promising performance in detecting epileptic seizures from EEG data.</span></p> ]]> Optimizing Seizure Detection: A Comparative Study of SVM, CNN, and RNN-LSTM sakshi kumari vijay khare parul arora doi: 10.18280/ijcmem.120405 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 369 10.18280/ijcmem.120405 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120405 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120404 Heating, Ventilation and Air-Conditioning (HVAC) systems are responsible of 50-60% of energy demand of the building sector. The scientific literature highlights that HVAC units are frequently operated under faulty conditions that can significantly affect their performance. In this paper, the performance of a typical single-duct dual-fan constant air volume Air-Handling Unit (AHU) is investigated through a number of experiments performed during Italian cooling and heating seasons under both fault free and faulty scenarios. The AHU operation is analysed while artificially introducing seven typical faults: return air damper kept always closed; fresh air damper kept always closed; fresh air damper kept always open; exhaust air damper kept always closed; supply air filter clogged at 50%; fresh air filter clogged at 50%; return air filter clogged at 50%. The faulty and fault free tests are compared to assess the environmental and economic performance impacts. The experimental data highlighted that the most adverse fault is that one corresponding to the exhaust air dumper kept always closed; in particular, it increases both the daily global equivalent CO2 emissions and the daily operating costs up to 110% in comparison with the fault free conditions. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Heating, Ventilation and Air-Conditioning (HVAC) systems are responsible of 50-60% of energy demand of the building sector. The scientific literature highlights that HVAC units are frequently operated under faulty conditions that can significantly affect their performance. In this paper, the performance of a typical single-duct dual-fan constant air volume Air-Handling Unit (AHU) is investigated through a number of experiments performed during Italian cooling and heating seasons under both fault free and faulty scenarios. The AHU operation is analysed while artificially introducing seven typical faults: return air damper kept always closed; fresh air damper kept always closed; fresh air damper kept always open; exhaust air damper kept always closed; supply air filter clogged at 50%; fresh air filter clogged at 50%; return air filter clogged at 50%. The faulty and fault free tests are compared to assess the environmental and economic performance impacts. The experimental data highlighted that the most adverse fault is that one corresponding to the exhaust air dumper kept always closed; in particular, it increases both the daily global equivalent CO</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif"> emissions and the daily operating costs up to 110% in comparison with the fault free conditions.</span></p> ]]> Experimental Assessment of Environmental and Economic Impacts of Dampers’ and Filters’ Faults in a Typical Air-Handling Unit in Southern Italy antonio rosato rita mercuri francesco romanucci mohammad el youssef doi: 10.18280/ijcmem.120404 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 361 10.18280/ijcmem.120404 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120404 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120403 Diesel fuel is composed of various molecules of hydrocarbons, so the properties vary from country to country. The sulfur content in Iraqi Diesel ranges from 1% to 2.5%. This abundance of sulfur contributes to a high level of emissions, including sulfur oxides, nitrogen oxides, volatile organic compounds, particulates, and carbon monoxide. To reduce emissions and improve engine performance, a diesel water mixture has been proposed as a fuel for diesel engines. This study examined the performance of a diesel engine under different operating conditions when Diesel was mixed with 10%, 20%, and 30% volume proportions of water, named W10, W20, and W30, respectively. The use of W10 and W20 caused a brake-specific fuel consumption reduction of 2.32% and 4.89%, respectively, compared to conventional Diesel, while using W30 caused an increase in brake-specific fuel consumption of about 5.75%. The brake thermal efficiency improved by 3.6% and 4.63% when using W10 and W20, respectively. While its value decreased when working with W30 by about 2.48% compared to Diesel. Working with W10 and W20 reduced engine emissions of carbon monoxide by an average of 9% and 27%, hydrocarbons by 7.8% and 20%, nitrogen oxides by 8.9% and 20.8%, and particulate matter by 4.92% and 13.1%. Operating with W10 and W20 reduced both particulate matter and nitrogen oxide emissions. The results reveal that water mixing with Iraqi Diesel is an effective means of reducing diesel engine emissions. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Diesel fuel is composed of various molecules of hydrocarbons, so the properties vary from country to country. The sulfur content in Iraqi Diesel ranges from 1% to 2.5%. This abundance of sulfur contributes to a high level of emissions, including sulfur oxides, nitrogen oxides, volatile organic compounds, particulates, and carbon monoxide. To reduce emissions and improve engine performance, a diesel water mixture has been proposed as a fuel for diesel engines. This study examined the performance of a diesel engine under different operating conditions when Diesel was mixed with 10%, 20%, and 30% volume proportions of water, named W10, W20, and W30, respectively. The use of W10 and W20 caused a brake-specific fuel consumption reduction of 2.32% and 4.89%, respectively, compared to conventional Diesel, while using W30 caused an increase in brake-specific fuel consumption of about 5.75%. The brake thermal efficiency improved by 3.6% and 4.63% when using W10 and W20, respectively. While its value decreased when working with W30 by about 2.48% compared to Diesel. Working with W10 and W20 reduced engine emissions of carbon monoxide by an average of 9% and 27%, hydrocarbons by 7.8% and 20%, nitrogen oxides by 8.9% and 20.8%, and particulate matter by 4.92% and 13.1%. Operating with W10 and W20 reduced both particulate matter and nitrogen oxide emissions. The results reveal that water mixing with Iraqi Diesel is an effective means of reducing diesel engine emissions.</span></p> ]]> Performance Improvement and Emissions Reduction with Environmentally Friendly Water-Diesel Emulsion Fuel louay a. mahdi hasanain a. abdul wahhab sanaa a. hafad mohammed a. fayad miqdam t. chaichan doi: 10.18280/ijcmem.120403 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 351 10.18280/ijcmem.120403 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120403 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120402 The chemical response and the collective buoyancy effects of thermal and mass diffusion in magnetohydrodynamic (MHD) convection are analyzed on an infinite vertical surface with porous material that emits gas as it rises. This study investigates how the governing equations perform under a broad range of stringent conditions, incorporating subjective considerations such as determining which factor dominates—suction velocity or Hall current strength. Ancillary currents were also considered to provide a comprehensive analysis. The governing equations for liquid flow were solved using the perturbation technique, yielding results in terms of temperature, concentration, and velocity fields. Dimensionless profiles of temperature, velocity, and concentration are graphically presented for various parameter values. It is observed that an increase in the Dufour number leads to higher primary and secondary velocities, as well as increased temperature. Conversely, primary and secondary velocities decrease with an increase in the chemical reaction number and magnetic field strength. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The chemical response and the collective buoyancy effects of thermal and mass diffusion in</span><span style="font-family: Times, serif"> </span><span style="font-family: Times New Roman, serif">magnetohydrodynamic (MHD) convection are analyzed on an infinite vertical surface with porous material that emits gas as it rises. This study investigates how the governing equations perform under a broad range of stringent conditions, incorporating subjective considerations such as determining which factor dominates—suction velocity or Hall current strength. Ancillary currents were also considered to provide a comprehensive analysis. The governing equations for liquid flow were solved using the perturbation technique, yielding results in terms of temperature, concentration, and velocity fields. Dimensionless profiles of temperature, velocity, and concentration are graphically presented for various parameter values. It is observed that an increase in the Dufour number leads to higher primary and secondary velocities, as well as increased temperature. Conversely, primary and secondary velocities decrease with an increase in the chemical reaction number and magnetic field strength.</span></p> ]]> Analyzing Energy and Mass Transport in MHD Convective Flow with Variable Suction and Hall Effects on a Vertical Porous Surface aruna ganjikunta obulesu mopuri charankumar ganteda vijayalakshmi arumugam s. vijayakumar varma vuyyuru lalitha giulio lorenzini doi: 10.18280/ijcmem.120402 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 341 10.18280/ijcmem.120402 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120402 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120401 Images play a pivotal role in documenting real-life events. With the rapid evolution of digital technology, there has been a significant increase in both the creation and dissemination of photographs. The accessibility of picture editing software has simplified the process of altering images, thereby reducing the time, costs, and expertise needed to create and manage visually manipulated content. Unfortunately, digitally altered photographs have become a primary medium for disseminating misinformation, which affects individuals and society at large. Consequently, the need for effective methods to detect and identify forgeries is more pressing than ever. One prevalent form of picture fraud, image splicing, has been thoroughly examined. In this study, we present a Depth-Wise Convolutional Neural Network (DWCNN) model specifically designed to accurately detect spliced forged images. By converting input RGB images to the HSV color space, known for its ability to withstand color and lighting variations, our model achieves high accuracy in identifying manipulated images. Furthermore, our proposed model is lightweight, based on the MobileNet architecture with seven bottleneck blocks, making it suitable for a wide range of scenarios with constrained resources. To evaluate the model's performance, we tested it on the CASIA v1.0 and CASIA v2.0 datasets. Our model accurately identified forgeries with 99.23% accuracy on the CASIA v1.0 dataset and achieved a remarkable accuracy of 99.37% on the CASIA v2.0 dataset. 12-26-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Images play a pivotal role in documenting real-life events. With the rapid evolution of digital technology, there has been a significant increase in both the creation and dissemination of photographs. The accessibility of picture editing software has simplified the process of altering images, thereby reducing the time, costs, and expertise needed to create and manage visually manipulated content. Unfortunately, digitally altered photographs have become a primary medium for disseminating misinformation, which affects individuals and society at large. Consequently, the need for effective methods to detect and identify forgeries is more pressing than ever. One prevalent form of picture fraud, image splicing, has been thoroughly examined. In this study, we present a Depth-Wise Convolutional Neural Network (DWCNN) model specifically designed to accurately detect spliced forged images. By converting input RGB images to the HSV color space, known for its ability to withstand color and lighting variations, our model achieves high accuracy in identifying manipulated images. Furthermore, our proposed model is lightweight, based on the MobileNet architecture with seven bottleneck blocks, making it suitable for a wide range of scenarios with constrained resources. To evaluate the model's performance, we tested it on the CASIA v1.0 and CASIA v2.0 datasets. Our model accurately identified forgeries with 99.23% accuracy on the CASIA v1.0 dataset and achieved a remarkable accuracy of 99.37% on the CASIA v2.0 dataset.</span></p> ]]> Image Splicing Detection Using Depth-Wise Convolution Neural Network mohammed s. khazaal mohamed elleuch monji kherallah faiza charfi doi: 10.18280/ijcmem.120401 International Journal of Computational Methods and Experimental Measurements 12-26-2024 International Journal of Computational Methods and Experimental Measurements 12-26-2024 2024 12 4 Article 333 10.18280/ijcmem.120401 https://www.acadlore.com/article/IJCMEM/2024_12_4/ijcmem.120401 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120312 Establishing model parameters is fast becoming more complex especially with generalized linear mixed models (GLMMs); which comprises of generalized linear models and classical linear mixed models. Evaluating generalized linear mixed models (GLMMs) parameters with maximum likelihood techniques involves some levels of complexity, to proffer solutions to this challenge, techniques involving approximation of integrals were considered in this paper. Some approximation methods for parameter estimation were considered to establish the most effective and adaptive model using a good number of model performance metrics/criteria. Penalized quasi-likelihood, adaptive gauss-Hermite quadrature, and Laplace approximation estimation techniques were considered to fit the real clinical data set with binary outcomes. Real-life data analysis showed some better fitness and superiority of an adaptive gauss-Hermit quadrature technique over some other existing estimation techniques using a set of model performance metrics. Data users at various levels of analysis may now consider adaptive gauss-Hermite quadrature technique over other estimation techniques in fitting GLMMs with binary responses. Coefficients of the model with good performance metrics were also considered in establishing effects of clinical follow-up on medical diagnoses of individual patients. 09-29-2025 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Establishing model parameters is fast becoming more complex especially with generalized linear mixed models (GLMMs); which comprises of generalized linear models and classical linear mixed models. Evaluating generalized linear mixed models (GLMMs) parameters with maximum likelihood techniques involves some levels of complexity, to proffer solutions to this challenge, techniques involving approximation of integrals were considered in this paper. Some approximation methods for parameter estimation were considered to establish the most effective and adaptive model using a good number of model performance metrics/criteria. Penalized quasi-likelihood, adaptive gauss-Hermite quadrature, and Laplace approximation estimation techniques were considered to fit the real clinical data set with binary outcomes. Real-life data analysis showed some better fitness and superiority of an adaptive gauss-Hermit quadrature technique over some other existing estimation techniques using a set of model performance metrics. Data users at various levels of analysis may now consider adaptive gauss-Hermite quadrature technique over other estimation techniques in fitting GLMMs with binary responses. Coefficients of the model with good performance metrics were also considered in establishing effects of clinical follow-up on medical diagnoses of individual patients.</span></p> ]]> Estimation Techniques for Generalized Linear Mixed Models with Binary Outcomes: Application in Medicine julus r. oluwadare olumide s. adesina adedayo f. adedotun oluwole a. odetunmibi doi: 10.18280/ijcmem.120312 International Journal of Computational Methods and Experimental Measurements 09-29-2025 International Journal of Computational Methods and Experimental Measurements 09-29-2025 2024 12 3 Article 323 10.18280/ijcmem.120312 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120312 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120311 This study aims to investigate the mechanical and morphological properties of hybrid composites fabricated from a Date Palm Mesh Fiber (DPMF) and glass wool reinforced with unsaturated polyester. The development of eco-friendly and efficient thermal insulation materials is crucial for reducing energy consumption and addressing environmental concerns. The hybrid composites were manufactured using the Bulk Molding Compound technique, and various factors such as fiber composition weight percentage, particle size, and quantities of DPMF and glass wool fibers were evaluated. Tensile, impact, and flexural bending tests were conducted to assess the mechanical properties of the composites. Design-Expert 12 software and analysis of variance ANOVA were employed to analyze the effects of fiber ratio, matrix ratio, and fiber size on the mechanical properties. The experimental results showed that the fiber content, DPMF content, and DPMF particle size in the matrix significantly influenced the mechanical properties of the hybrid composites. Increasing the fiber content and DPMF particle sizes improved the interfacial bonding between DPMF and the polymer matrix, enhancing the matrix's tensile strength and flexural strength of the composites. However, high amounts of DPMF resulted in poor energy absorption abilities of the composites under impact load. The fractography analysis using FESEM confirmed the mechanical test results by revealing a rough fracture surface in the composites reinforced with DPMF, indicating stronger bonding between the fibers and the unsaturated polyester matrix. This study highlights the potential of hybrid composites as eco-friendly and efficient thermal insulation materials and provides insights into the influence of various parameters on their mechanical properties. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman">This study aims to investigate the mechanical and morphological properties of hybrid composites fabricated from a Date Palm Mesh Fiber (DPMF) and glass wool reinforced with unsaturated polyester. The development of eco-friendly and efficient thermal insulation materials is crucial for reducing energy consumption and addressing environmental concerns. The hybrid composites were manufactured using the Bulk Molding Compound technique, and various factors such as fiber composition weight percentage, particle size, and quantities of DPMF and glass wool fibers were evaluated. Tensile, impact, and flexural bending tests were conducted to assess the mechanical properties of the composites. Design-Expert 12 software and analysis of variance ANOVA were employed to analyze the effects of fiber ratio, matrix ratio, and fiber size on the mechanical properties. The experimental results showed that the fiber content, DPMF content, and DPMF particle size in the matrix significantly influenced the mechanical properties of the hybrid composites. Increasing the fiber content and DPMF particle sizes improved the interfacial bonding between DPMF and the polymer matrix, enhancing the matrix's tensile strength and flexural strength of the composites. However, high amounts of DPMF resulted in poor energy absorption abilities of the composites under impact load. The fractography analysis using FESEM confirmed the mechanical test results by revealing a rough fracture surface in the composites reinforced with DPMF, indicating stronger bonding between the fibers and the unsaturated polyester matrix. This study highlights the potential of hybrid composites as eco-friendly and efficient thermal insulation materials and provides insights into the influence of various parameters on their mechanical properties.</span></p> ]]> Characterization of the Mechanical and Morphological Properties of Hybrid Composites from Date Palm Fiber/Glass Wool Reinforced by Unsaturated Polyester mustafa ali altemmey mohammed w. muhieldeen lih jiun yu cik suhana hassan hussein alaa jaber doi: 10.18280/ijcmem.120311 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 309 10.18280/ijcmem.120311 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120311 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120310 The WBM’s viscosity, gel strength and ability to filter and control the filtration rate are central to the stabilization of the well bore as well as the transportation of the cuttings to the surface. WBM is comprehensively inexpensive and eco-friendly; it does not hinder the biodegradation process as compared to other chemicals that may be used in the drilling involving rig activities. It cans thermally change, regulate formation pressure, and support cuttings. WBM is also can be used in all types of formations and is not complicated in terms of its handling as well as disposing as compared to other drilling fluids. However, WBM has some limitations as it is influenced by shale hydration, formation water salinity and thermally less stable at high temperature formations. Hindered by formation solids, fluid loss to the formation and formation damage are other issues that must be dealt with efficiently during the drilling process using WBM. WBM is used in most practices of drilling especially in offshore drilling areas, environment sensitive areas, and areas that have certain restrictions on the types of fluids to be used in drilling. Effectiveness and flexibility in relation to various platforms and various rigs make it a prime candidate for the most orthodox as well as the most innovative operations. Some of the regular water based muds that are often in use are Spud mud, Low solid polymer mud KCl, PHPA polymer mud KCl, Glycol polymer mud, Salt Saturated mud and Drill – in mud. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman">The WBM’s viscosity, gel strength and ability to filter and control the filtration rate are central to the stabilization of the well bore as well as the transportation of the cuttings to the surface. WBM is comprehensively inexpensive and eco-friendly; it does not hinder the biodegradation process as compared to other chemicals that may be used in the drilling involving rig activities. It cans thermally change, regulate formation pressure, and support cuttings. WBM is also can be used in all types of formations and is not complicated in terms of its handling as well as disposing as compared to other drilling fluids. However, WBM has some limitations as it is influenced by shale hydration, formation water salinity and thermally less stable at high temperature formations. Hindered by formation solids, fluid loss to the formation and formation damage are other issues that must be dealt with efficiently during the drilling process using WBM. WBM is used in most practices of drilling especially in offshore drilling areas, environment sensitive areas, and areas that have certain restrictions on the types of fluids to be used in drilling. Effectiveness and flexibility in relation to various platforms and various rigs make it a prime candidate for the most orthodox as well as the most innovative operations. Some of the regular water based muds that are often in use are Spud mud, Low solid polymer mud KCl, PHPA polymer mud KCl, Glycol polymer mud, Salt Saturated mud and Drill – in mud.</span></p> ]]> Comprehensive Analysis of Water Based Emulsion Drilling Fluids in GHARRAF Oil Field in Southern Iraq: Properties, Specifications, and Practical Applications mustafa m. mansour iqbal khalaf erabee alaa m. lafta doi: 10.18280/ijcmem.120310 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 297 10.18280/ijcmem.120310 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120310 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120309 Nowadays, digital evidence plays a vital role in criminal investigations and arraignments. Digital criminal Investigators can also use this as an opportunity if the vast amount of data is a current trial. Assess constructive and constructive data and advice from the defendant proof behind the crime in terms of issues. Identifying criminal or criminal activity is a big deal because it connects certain data sets. It set an innovative law framework to quickly and accurately solve problems within the law's boundary. In this regard, the machine learning approach Naive Bayes classification for digital criminology data sets is to identify criminals. The Naive Baye classification process is used for digital criminology data application. To approximate square estimate for data sets of digital criminology subgroups. Also, support the Hadoop Big Data System Understanding Map with Reduce programming with the Naive Bayes classifier. The experiment result was a huge accumulated failure in the data quality. Based on these data, the estimation parameter of the statistical model is reached. The least-square estimate estimates the parameters that deal with the statistical model in the experimental result. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman">Nowadays, digital evidence plays a vital role in criminal investigations and arraignments. Digital criminal Investigators can also use this as an opportunity if the vast amount of data is a current trial. Assess constructive and constructive data and advice from the defendant proof behind the crime in terms of issues. Identifying criminal or criminal activity is a big deal because it connects certain data sets. It set an innovative law framework to quickly and accurately solve problems within the law's boundary. In this regard, the machine learning approach Naive Bayes classification for digital criminology data sets is to identify criminals. The Naive Baye classification process is used for digital criminology data application. To approximate square estimate for data sets of digital criminology subgroups. Also, support the Hadoop Big Data System Understanding Map with Reduce programming with the Naive Bayes classifier. The experiment result was a huge accumulated failure in the data quality. Based on these data, the estimation parameter of the statistical model is reached. The least-square estimate estimates the parameters that deal with the statistical model in the experimental result.</span></p> ]]> Crime Data Analysis Using Naive Bayes Classification and Least Square Estimation with MapReduce dileep kumar kadali r.n.v. jagan mohan m. chandra naik yugandhar bokka doi: 10.18280/ijcmem.120309 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 289 10.18280/ijcmem.120309 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120309 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120308 Loop unrolling is a well-known code-transforming method that can enhance program efficiency during runtime. The fundamental advantage of unrolling a loop is that it frequently reduces the execution time of the unrolled loop when compared to the original loop. Choosing a large unroll factor might initially save execution time by reducing loop overhead and improving parallelism, but excessive unrolling can result in increased cache misses, register pressure, and memory inefficiencies, eventually slowing down the program. Therefore, identifying the optimal unroll factor is of essential importance. This paper introduces three ensemble-learning techniques—XGBoost, Random Forest (RF), and Bagging—for predicting the efficient unroll factor for specific programs. A dataset comprises various programs derived from many benchmarks, which are Polybench, Shootout, and other programs. More than 220 examples, drawn from 20 benchmark programs with different loop iterations, used to train three ensemble-learning methods. The unroll factor with the biggest reduction in program execution time is chosen to be added to the dataset, and ultimately it will be a candidate for the unseen programs. Our empirical results reveal that the XGBoost and RF methods outperform the Bagging algorithm, with a final accuracy of 99.56% in detecting the optimal unroll factor. 09-29-2024 <![CDATA[ <p><span style="font-family: Times">Loop unrolling is a well-known code-transforming method that can enhance program efficiency during runtime. The fundamental advantage of unrolling a loop is that it frequently reduces the execution time of the unrolled loop when compared to the original loop. Choosing a large unroll factor might initially save execution time by reducing loop overhead and improving parallelism, but excessive unrolling can result in increased cache misses, register pressure, and memory inefficiencies, eventually slowing down the program. Therefore, identifying the optimal unroll factor is of essential importance. This paper introduces three ensemble-learning techniques—XGBoost, Random Forest (RF), and Bagging—for predicting the efficient unroll factor for specific programs. A dataset comprises various programs derived from many benchmarks, which are Polybench, Shootout, and other programs. More than 220 examples, drawn from 20 benchmark programs with different loop iterations, used to train three ensemble-learning methods. The unroll factor with the biggest reduction in program execution time is chosen to be added to the dataset, and ultimately it will be a candidate for the unseen programs. Our empirical results reveal that the XGBoost and RF methods outperform the Bagging algorithm, with a final accuracy of 99.56% in detecting the optimal unroll factor.</span></p> ]]> Optimizing Program Efficiency by Predicting Loop Unroll Factors Using Ensemble Learning esraa h. alwan ali kadhum m. al-qurabat doi: 10.18280/ijcmem.120308 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 281 10.18280/ijcmem.120308 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120308 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120307 Sound classification is considered as one of the most important areas of classification domain, but the least developed compared to speech and voice recognition. In this study, we focus on the works that deal with sound classification by making a comparative study based on feature extraction and classification methods as well as the targeted sound corpus. Next, we present an overview of sound classification systems that utilize deep learning techniques, aiming to compare them with traditional learning methods. Based on our previous studies and conclusions, and considering that the challenge in choosing classification methods lies in balancing accuracy and computational cost, we conducted experiments using SVMs (support vector machines) with different kernels and MFCCs (Mel frequency Cepstral coefficients). Tests are carried out for the classification of some indoor abnormal sounds, then the number of classes is increased to cover a wider variety of sounds in order to observe and study the system's behavior. Finally, the results obtained in this work are promising and motivate us to explore deeper tests which are mentioned in the discussion and conclusion section. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman">Sound classification is considered as one of the most important areas of classification domain, but the least developed compared to speech and voice recognition. In this study, we focus on the works that deal with sound classification by making a comparative study based on feature extraction and classification methods as well as the targeted sound corpus. Next, we present an overview of sound classification systems that utilize deep learning techniques, aiming to compare them with traditional learning methods. Based on our previous studies and conclusions, and considering that the challenge in choosing classification methods lies in balancing accuracy and computational cost, we conducted experiments using SVMs (support vector machines) with different kernels and MFCCs (Mel frequency Cepstral coefficients). Tests are carried out for the classification of some indoor abnormal sounds, then the number of classes is increased to cover a wider variety of sounds in order to observe and study the system's behavior. Finally, the results obtained in this work are promising and motivate us to explore deeper tests which are mentioned in the discussion and conclusion section.</span></p> ]]> Indoor Sound Classification with Support Vector Machines: State of the Art and Experimentation leila abdoune mohamed fezari ahmed dib doi: 10.18280/ijcmem.120307 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 269 10.18280/ijcmem.120307 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120307 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120306 This study aims to identify the most suitable deep learning model for early detection of dental caries in a new database of dental diseases. The study compares the performance of residual and dense networks using standard performance metrics. Dental caries is categorized into four classes based on dental practitioner recommendations. A novel database consisting of 1064 intraoral digital RGB images from 194 patients was collected in collaboration with Bharati Vidyapeeth’s Dental College, Pune. These images were cropped to obtain a total of 987 single-tooth images, which were divided into 888 training, 45 testing, and 54 validation images. In Phase I experimentation, ResNet50V2, ResNet101V2, ResNet152, DenseNet169, and DenseNet201 were utilized. Phase II focused on ResNet50V2, DenseNet169, and DenseNet201, while Phase III concentrated on DenseNet169 and DenseNet201. For Phase I experimentation, the overall accuracy of dental caries classification ranged from 0.55 to 0.84, with DenseNet exhibiting superior performance. In Phase II, the overall accuracy varied from 0.72 to 0.78, with DenseNet achieving the highest accuracy of 0.78. Similarly, in Phase III, DenseNet201 surpassed other models with an overall accuracy of 0.93. The DenseNet201 algorithm shows promise for detecting and classifying dental caries in digital RGB images. This finding is significant for the future development of automated mobile applications based on dental photographs, which could assist dental practitioners during examinations. Additionally, it could enhance patient understanding of dental caries severity, thereby promoting dental health awareness. 09-29-2024 <![CDATA[ <p>This study aims to identify the most suitable deep learning model for early detection of dental caries in a new database of dental diseases. The study compares the performance of residual and dense networks using standard performance metrics. Dental caries is categorized into four classes based on dental practitioner recommendations. A novel database consisting of 1064 intraoral digital RGB images from 194 patients was collected in collaboration with Bharati Vidyapeeth’s Dental College, Pune. These images were cropped to obtain a total of 987 single-tooth images, which were divided into 888 training, 45 testing, and 54 validation images. In Phase I experimentation, ResNet50V2, ResNet101V2, ResNet152, DenseNet169, and DenseNet201 were utilized. Phase II focused on ResNet50V2, DenseNet169, and DenseNet201, while Phase III concentrated on DenseNet169 and DenseNet201. For Phase I experimentation, the overall accuracy of dental caries classification ranged from 0.55 to 0.84, with DenseNet exhibiting superior performance. In Phase II, the overall accuracy varied from 0.72 to 0.78, with DenseNet achieving the highest accuracy of 0.78. Similarly, in Phase III, DenseNet201 surpassed other models with an overall accuracy of 0.93. The DenseNet201 algorithm shows promise for detecting and classifying dental caries in digital RGB images. This finding is significant for the future development of automated mobile applications based on dental photographs, which could assist dental practitioners during examinations. Additionally, it could enhance patient understanding of dental caries severity, thereby promoting dental health awareness.</p> ]]> Identifying Suitable Deep Learning Approaches for Dental Caries Detection Using Smartphone Imaging leena rohan mehta megha s. borse meenal tepan janhavi shah doi: 10.18280/ijcmem.120306 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 251 10.18280/ijcmem.120306 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120306 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120305 The present study will attempt to investigate the energy dissipation in a stair-shaped stilling basin, developed as an improved model of the USBR Type III basin. For this purpose, an initial step of planning and modeling of the flume was undertaken, followed by experimental setup and data collection on the water level, critical depth, velocity, and discharge. In each of these two models, experiments were conducted for 10 variations in discharge. The energy dissipation ratio for the stair-shaped model reached 81.59%, as opposed to 78.99% for the USBR Type III. That means that the efficiency in the stair-shaped model is 2.6% higher. The velocity varied between 19.17 and 29.80 m/s for the USBR Type III model and between 17.42 and 28.14 m/s for the stair-shaped model. The maximum water level in USBR Type III was 'this', while in the stair-shaped model, it is +22.95, thus showing better energy dissipation. The stair-shaped model, also closely lies with the hydraulic jump state according to Elevatorski's formula and shows a value of 7% skewness. Further recommendations on topographic and geological conditions are warranted for the application of a stair-shaped basin. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The present study will attempt to investigate the energy dissipation in a stair-shaped stilling basin, developed as an improved model of the USBR Type III basin. For this purpose, an initial step of planning and modeling of the flume was undertaken, followed by experimental setup and data collection on the water level, critical depth, velocity, and discharge. In each of these two models, experiments were conducted for 10 variations in discharge. The energy dissipation ratio for the stair-shaped model reached 81.59%, as opposed to 78.99% for the USBR Type III. That means that the efficiency in the stair-shaped model is 2.6% higher. The velocity varied between 19.17 and 29.80 m/s for the USBR Type III model and between 17.42 and 28.14 m/s for the stair-shaped model. The maximum water level in USBR Type III was 'this', while in the stair-shaped model, it is +22.95, thus showing better energy dissipation. The stair-shaped model, also closely lies with the hydraulic jump state according to Elevatorski's formula and shows a value of 7% skewness. Further recommendations on topographic and geological conditions are warranted for the application of a stair-shaped basin.</span></p> ]]> Experimental Study of Energy Dissipation and Efficiency in a Stair-Shaped Modification of USBR Type III Stilling Basin gilang idfi umboro lasminto anak agung gde kartika doi: 10.18280/ijcmem.120305 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 237 10.18280/ijcmem.120305 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120305 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120304 This work continues the assessment of the application of carbon nanotubes (CNTs) mixed with zirconia (ZrO2). The study examined the compressive, bending, and bond strengths of samples containing and lacking carbon nanotubes. Zirconia carbon nanotubes (ZrO2) in the concentrations of 0.00 %, 0.01 %, 0.02 %, 0.03 %, 0.04 %, and 0.05 % were the subjects of six mixtures whose resistance was measured. The results were analyzed using the finite element method with the ANSYS 15.0 program. ANSYS 15.0 software is used to analyze compressive and bending loads as well as the conventional zirconia model. Showcase the advantages of moderately utilizing carbon nanotubes. Zirconia's mechanical properties can be improved more effectively by mineral/chemical mixtures or fibers without the issues related to carbon nanotube dispersion. Provide evidence of the advantages of moderately utilizing carbon nanotubes. Without the issues related to carbon nanotube dispersion or the health hazards of handling Nanomaterials, zirconia's mechanical properties can be improved more effectively by mineral/chemical mixtures or fibers. The maximum and ideal load for the load was found to be 163.5 MPa, which was approved in all tests after the six models were finished with their designs in the ANSYS program. This was based on the von mises stress value and the maximum shear stress value less than the yield strength of the basic material used. After making numerous attempts, this load was selected by increasing the load by a specific percentage until it reached the ideal load, at which point the original model was able to support the load without experiencing any problems. The results of the ANSYS program were compared and examined, and they showed that the models' resistance to deformations, displacements, stresses, and various strains greatly increased when carbon nanotubes were added. By adding more carbon nanotubes, those models will be more resilient to the strains and deformations caused by compressive loads. The deformation rate decreased by 60%, which was a very noticeable decrease, especially in the sixth model where the carbon percentage was 5%. 09-29-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">This work continues the assessment of the application of carbon nanotubes (CNTs) mixed with zirconia (ZrO</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif">). The study examined the compressive, bending, and bond strengths of samples containing and lacking carbon nanotubes. Zirconia carbon nanotubes (ZrO</span>_{<span style="font-family: Times New Roman, serif">2</span>}<span style="font-family: Times New Roman, serif">) in the concentrations of 0.00 %, 0.01 %, 0.02 %, 0.03 %, 0.04 %, and 0.05 % were the subjects of six mixtures whose resistance was measured. The results were analyzed using the finite element method with the ANSYS 15.0 program. ANSYS 15.0 software is used to analyze compressive and bending loads as well as the conventional zirconia model. Showcase the advantages of moderately utilizing carbon nanotubes. Zirconia's mechanical properties can be improved more effectively by mineral/chemical mixtures or fibers without the issues related to carbon nanotube dispersion. Provide evidence of the advantages of moderately utilizing carbon nanotubes. Without the issues related to carbon nanotube dispersion or the health hazards of handling Nanomaterials, zirconia's mechanical properties can be improved more effectively by mineral/chemical mixtures or fibers. The maximum and ideal load for the load was found to be 163.5 MPa, which was approved in all tests after the six models were finished with their designs in the ANSYS program. This was based on the von mises stress value and the maximum shear stress value less than the yield strength of the basic material used. After making numerous attempts, this load was selected by increasing the load by a specific percentage until it reached the ideal load, at which point the original model was able to support the load without experiencing any problems. The results of the ANSYS program were compared and examined, and they showed that the models' resistance to deformations, displacements, stresses, and various strains greatly increased when carbon nanotubes were added. By adding more carbon nanotubes, those models will be more resilient to the strains and deformations caused by compressive loads. The deformation rate decreased by 60%, which was a very noticeable decrease, especially in the sixth model where the carbon percentage was 5%.</span></p> ]]> Finite Element Analysis of the Effect of Carbon Nanotube Content on the Compressive Properties of Zirconia Nanocomposites iman zaidan alshih yahya hasan mahmood kaedhi emad toma karash waleed mohammed najm doi: 10.18280/ijcmem.120304 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 227 10.18280/ijcmem.120304 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120304 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120303 The amount of information produced about any item or user has reached a very staggering level. Not only the volume of data, the velocity of data has reached an unprecedented magnitude. For any information retrieval or information processing system to work efficiently, it should be able to process massive amounts of data in real-time. Modern systems face a lot of challenges in managing data with high volume and velocity, especially when these systems are required to generate accurate predictions in a timely fashion. The most efficient way to ensure that modern information retrieval systems can adapt to the current volume and velocity of data is to implement them over a parallel and distributed environment. In this paper, we put forward a method for enhancing the scalability and performance of recommender systems in big data environments. By using the Euclidean distance to calculate the cosine similarity we introduce a technique which is efficient in parallelizing the algorithm for distributed environments. Thereby improving the computational efficiency and scalability of the recommender system. This enables such systems to manage large datasets with high accuracy and speed. With the help of parallel processing, our method can assist modern information retrieval systems keep up with the pace of ever-growing demands of data velocity and volume, ensuring real-time performance and robust scalability. 09-29-2024 <![CDATA[ <p>The amount of information produced about any item or user has reached a very staggering level. Not only the volume of data, the velocity of data has reached an unprecedented magnitude. For any information retrieval or information processing system to work efficiently, it should be able to process massive amounts of data in real-time. Modern systems face a lot of challenges in managing data with high volume and velocity, especially when these systems are required to generate accurate predictions in a timely fashion. The most efficient way to ensure that modern information retrieval systems can adapt to the current volume and velocity of data is to implement them over a parallel and distributed environment. In this paper, we put forward a method for enhancing the scalability and performance of recommender systems in big data environments. By using the Euclidean distance to calculate the cosine similarity we introduce a technique which is efficient in parallelizing the algorithm for distributed environments. Thereby improving the computational efficiency and scalability of the recommender system. This enables such systems to manage large datasets with high accuracy and speed. With the help of parallel processing, our method can assist modern information retrieval systems keep up with the pace of ever-growing demands of data velocity and volume, ensuring real-time performance and robust scalability.</p> ]]> Parallel Memory-Based Collaborative Filtering for Distributed Big Data Environments pallavi shree somaraju suvvari doi: 10.18280/ijcmem.120303 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 217 10.18280/ijcmem.120303 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120303 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120302 The present work is focused on the simulation of Casson (non-Newtonian) nanofluid flow over an inclined stretching sheet. The study considers the influence of an imposed magnetic field, heat source/sink, thermal radiation and chemical reaction under the multi slip effects. The study includes the application of wall suction/injection and Navier's first-order slip to analyse the velocity, temperature, and concentration at the wall. The governing equations have been transformed into nonlinear ordinary differential equations (ODEs) with similarity transformations. By employing the homotopy analysis method (HAM), we have successfully derived the numerical solution for the nonlinear ordinary differential equations (ODEs) and their corresponding boundary conditions. The impact of various parameters on the velocity, temperature, and concentration field has also been demonstrated. Multiple slip flow is utilised in various practical domains like micro-electro-mechanical systems, nano-electro-mechanical systems, micro-organism flow, and rarefied gas flow, among others. 09-29-2024 <![CDATA[ <p>The present work is focused on the simulation of Casson (non-Newtonian) nanofluid flow over an inclined stretching sheet. The study considers the influence of an imposed magnetic field, heat source/sink, thermal radiation and chemical reaction under the multi slip effects. The study includes the application of wall suction/injection and Navier's first-order slip to analyse the velocity, temperature, and concentration at the wall. The governing equations have been transformed into nonlinear ordinary differential equations (ODEs) with similarity transformations. By employing the homotopy analysis method (HAM), we have successfully derived the numerical solution for the nonlinear ordinary differential equations (ODEs) and their corresponding boundary conditions. The impact of various parameters on the velocity, temperature, and concentration field has also been demonstrated. Multiple slip flow is utilised in various practical domains like micro-electro-mechanical systems, nano-electro-mechanical systems, micro-organism flow, and rarefied gas flow, among others.</p> ]]> Radiative Chemically MHD Non-Newtonian Nanofluid Flow over an Inclined Stretching Sheet with Heat Source and Multi-Slip Effects pennelli saila kumari shaik mohammed ibrahim prathi vijaya kumar giulio lorenzini doi: 10.18280/ijcmem.120302 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 203 10.18280/ijcmem.120302 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120302 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120301 Welded joints in rail steel structures are typically assessed for fatigue using two different stress range approaches: nominal stress range and hot-spot stress range when using SN methods. The nominal stress range is a traditionally simplified method that provides a conservative estimation but lacks accuracy in considering stress concentrations. On the other hand, the hot-spot stress range method is a more advanced and refined approach that offers a more precise evaluation of stress concentration, making it suitable for complex geometries. The BS7608-2015 British standard, Guide to Fatigue Design and Assessment of Steel Products, incorporated the hot-spot method for evaluating weld joints, especially when using numerical methods such as Finite Element Analysis (FEA). The weld classes are now categorically defined for both nominal and hot-spot approaches in new introductions, whereas earlier, it was based on the nominal stress approach only. Choosing the appropriate stress method depends on various factors, including the weld joint geometry, stress orientations, loading conditions, the desired level of accuracy, and primarily the available SN curve data for predicting fatigue damage. The work presented in this paper explores the hot-spot stress approach for determining stress in weld fatigue assessment for Rail Track Maintenance Equipment. The identified welds were assessed for variation in hot-spot stress on different mesh types, weld modeling techniques, and their effect on the fatigue damage factor using IIW and BS7608 guidelines. The joints under study were F2 and D class with nominal and hot-spot stress assessment, respectively, as per BS7608. These are more common weld joints in structural evaluations of rail equipment. The hot-spot approach for stress variation was studied on smaller models first. Subsequently, the approach was applied to assess the weld fatigue in rail equipment, and the results were compared with those obtained using the nominal stress approach. 09-29-2024 <![CDATA[ <p>Welded joints in rail steel structures are typically assessed for fatigue using two different stress range approaches: nominal stress range and hot-spot stress range when using SN methods. The nominal stress range is a traditionally simplified method that provides a conservative estimation but lacks accuracy in considering stress concentrations. On the other hand, the hot-spot stress range method is a more advanced and refined approach that offers a more precise evaluation of stress concentration, making it suitable for complex geometries. The BS7608-2015 British standard, Guide to Fatigue Design and Assessment of Steel Products, incorporated the hot-spot method for evaluating weld joints, especially when using numerical methods such as Finite Element Analysis (FEA). The weld classes are now categorically defined for both nominal and hot-spot approaches in new introductions, whereas earlier, it was based on the nominal stress approach only. Choosing the appropriate stress method depends on various factors, including the weld joint geometry, stress orientations, loading conditions, the desired level of accuracy, and primarily the available SN curve data for predicting fatigue damage. The work presented in this paper explores the hot-spot stress approach for determining stress in weld fatigue assessment for Rail Track Maintenance Equipment. The identified welds were assessed for variation in hot-spot stress on different mesh types, weld modeling techniques, and their effect on the fatigue damage factor using IIW and BS7608 guidelines. The joints under study were F2 and D class with nominal and hot-spot stress assessment, respectively, as per BS7608. These are more common weld joints in structural evaluations of rail equipment. The hot-spot approach for stress variation was studied on smaller models first. Subsequently, the approach was applied to assess the weld fatigue in rail equipment, and the results were compared with those obtained using the nominal stress approach.</p> ]]> FEA Stress Determination for Weld Fatigue Using Hot-Spot Stress Method: Benchmarking and Rail Application dipak patil doi: 10.18280/ijcmem.120301 International Journal of Computational Methods and Experimental Measurements 09-29-2024 International Journal of Computational Methods and Experimental Measurements 09-29-2024 2024 12 3 Article 191 10.18280/ijcmem.120301 https://www.acadlore.com/article/IJCMEM/2024_12_3/ijcmem.120301 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120208 This paper proposes enhancing the K-means clustering method by incorporating the Crow Search Algorithm (CSA) and Calinski-Harabasz (CH) index to address the issue of determining the optimal number of clusters and attribute selection. The proposed approach, called Crow Search Algorithm K-mean clustering (CSAK_means), aims to explore the search space more effectively to find the best solutions. The efficiency of the CSAK_means algorithm is evaluated using a comparative experimental study for five datasets from the UCI repositories: Wine, Bodega, Cmc, Zoo, and Abalone. The results confirm that the proposed method outperforms the default algorithms in terms of average feature selection performance and silhouette value. 06-29-2024 <![CDATA[ <p>This paper proposes enhancing the K-means clustering method by incorporating the Crow Search Algorithm (CSA) and Calinski-Harabasz (CH) index to address the issue of determining the optimal number of clusters and attribute selection. The proposed approach, called Crow Search Algorithm K-mean clustering (CSAK_means), aims to explore the search space more effectively to find the best solutions. The efficiency of the CSAK_means algorithm is evaluated using a comparative experimental study for five datasets from the UCI repositories: Wine, Bodega, Cmc, Zoo, and Abalone. The results confirm that the proposed method outperforms the default algorithms in terms of average feature selection performance and silhouette value.</p> ]]> Enhanced Unsupervised Feature Selection Method Using Crow Search Algorithm and Calinski-Harabasz fatima m. hasan talal f. hussein hanadi d. saleem omar s. qasim doi: 10.18280/ijcmem.120208 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 185 10.18280/ijcmem.120208 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120208 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120207 In this paper, two distinct strategies were used to enhance problem-solving abilities. The first strategy involved developing a conjugate gradient algorithm in which several new parameters were derived and proposed. The second strategy included hybridizing the dwarf mongoose optimization (DMO) algorithm in two ways, the first using the community by taking advantage of the developed conjugate gradient algorithm that was extracted from the first strategy and obtaining the hybrid algorithm (CG-DMO) that gives better results than the results of the original algorithm. The second method is to combine the sand cat swarm optimization algorithm (SCSO) and the dwarf mongoose optimization algorithm (DMO), and a hybrid algorithm (SCSO-DMO) is obtained. The dwarf mongoose optimization (DMO) algorithm uses three mongoose social groups: the alpha group, the scout group, and the babysitter group to replicate their foraging behavior. The Alpha group underwent hybridization, using the attack method of sand cats, known for their keen hearing of low-frequency sounds and their adeptness at detecting prey by digging. This hybrid approach led to the development of an equation for identifying candidate food sites within the alpha group. The proposed algorithms (CG-DMO) and (SCSO-DMO) underwent extensive testing on standard test functions, resulting in superior results compared to the original algorithm. 06-29-2024 <![CDATA[ <p>In this paper, two distinct strategies were used to enhance problem-solving abilities. The first strategy involved developing a conjugate gradient algorithm in which several new parameters were derived and proposed. The second strategy included hybridizing the dwarf mongoose optimization (DMO) algorithm in two ways, the first using the community by taking advantage of the developed conjugate gradient algorithm that was extracted from the first strategy and obtaining the hybrid algorithm (CG-DMO) that gives better results than the results of the original algorithm. The second method is to combine the sand cat swarm optimization algorithm (SCSO) and the dwarf mongoose optimization algorithm (DMO), and a hybrid algorithm (SCSO-DMO) is obtained. The dwarf mongoose optimization (DMO) algorithm uses three mongoose social groups: the alpha group, the scout group, and the babysitter group to replicate their foraging behavior. The Alpha group underwent hybridization, using the attack method of sand cats, known for their keen hearing of low-frequency sounds and their adeptness at detecting prey by digging. This hybrid approach led to the development of an equation for identifying candidate food sites within the alpha group. The proposed algorithms (CG-DMO) and (SCSO-DMO) underwent extensive testing on standard test functions, resulting in superior results compared to the original algorithm.</p> ]]> <a id="_Hlk167283207"></a>Hybridize the Dwarf Mongoose Optimization (DMO) Algorithm to Obtain the Optimal Solution for Solve Optimization Problems omar d. shalal ban a. mitras doi: 10.18280/ijcmem.120207 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 175 10.18280/ijcmem.120207 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120207 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120206 In the gas and industry, erosion that is brought on by particles in pipe bends is a severe issue that can lead to failure or equipment malfunction. The computational fluid dynamics (CFD) approach is primarily utilized in the presented study in order to investigate the erosion distributions as well as particle trajectories in pipe bends under various influencing conditions. Throughout upstream petroleum production activities, crude oil as well as eroded sand from formation zones is frequently transported together via pipes up to flow stations and between flow stations and pipe. The rotator fin is propelled by flow momentum in the stream-lines which are particle-laden flow pipe walls, particularly at the elbows, causing erosive damages, which could result in costly and disastrous system failure. Thus, calculating the erosion rate while the system is operating is essential to predict failures and preventing them. Of all fittings used in the piping systems, the elbows are the most prone to experience erosions brought on by oil-carried rotator fins that veer off course and strike the walls as they pass through the bent portions of elbows. The numerical simulation-based erosion prediction model was used in order to calculate relative erosion severity so as to lessen erosive damage caused through the solid rotator fin. Physical features such as particle tracking, flow turbulence, and erosion simulation were merged in this work to create the potentials needed to fully represent the present issue. The computational simulation related to crude oil flow offers comprehensive insights, but it also allows for the avoidance of significant expenses and laborious attempts associated with conventional experiments. The new analysis provides invaluable physical information that may be utilized to assess oil recovery and employ the model as an alternate particle-laden flow management tool. Additionally, it might pinpoint limiting processes and elements; develop a computer-aided tool to optimize and design future pipe systems for increasing their lifetime by enhancing their erosion resistance, which would undoubtedly save a significant amount of cost and time. 06-29-2024 <![CDATA[ <p>In the gas and industry, erosion that is brought on by particles in pipe bends is a severe issue that can lead to failure or equipment malfunction. The computational fluid dynamics (CFD) approach is primarily utilized in the presented study in order to investigate the erosion distributions as well as particle trajectories in pipe bends under various influencing conditions. Throughout upstream petroleum production activities, crude oil as well as eroded sand from formation zones is frequently transported together via pipes up to flow stations and between flow stations and pipe. The rotator fin is propelled by flow momentum in the stream-lines which are particle-laden flow pipe walls, particularly at the elbows, causing erosive damages, which could result in costly and disastrous system failure. Thus, calculating the erosion rate while the system is operating is essential to predict failures and preventing them. Of all fittings used in the piping systems, the elbows are the most prone to experience erosions brought on by oil-carried rotator fins that veer off course and strike the walls as they pass through the bent portions of elbows. The numerical simulation-based erosion prediction model was used in order to calculate relative erosion severity so as to lessen erosive damage caused through the solid rotator fin. Physical features such as particle tracking, flow turbulence, and erosion simulation were merged in this work to create the potentials needed to fully represent the present issue. The computational simulation related to crude oil flow offers comprehensive insights, but it also allows for the avoidance of significant expenses and laborious attempts associated with conventional experiments. The new analysis provides invaluable physical information that may be utilized to assess oil recovery and employ the model as an alternate particle-laden flow management tool. Additionally, it might pinpoint limiting processes and elements; develop a computer-aided tool to optimize and design future pipe systems for increasing their lifetime by enhancing their erosion resistance, which would undoubtedly save a significant amount of cost and time.</p> ]]> Modification Design and Process of Pipeline to Reduce Erosion Rate and Deposited haider sami salman mustafa m. mansour alaa m. lafta ahmed j. shkarah doi: 10.18280/ijcmem.120206 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 165 10.18280/ijcmem.120206 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120206 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120205 With the expansion of IoT platforms for smart livestock farming applications and their application to agriculture, farmers are becoming more interested. This research paper presents innovative IoT solutions for the economic propagation of animals using Raspberry Pi boards. This research has two main objectives (1) design and build a cooling system that continuously controls the temperature between 8-20 degrees Celsius and controls the oxygen content in the water between 4-8 mg/L. This control uses IOT technology to control the sending and receiving of data with the Raspberry Pi board. (2) The experimental cultivation of Chinese mitten crab in a traditional cold pond was compared to that of a new type of culture pond. The design and creation of the Chinese mitten crab culture pond and the use of IOT technology to control data transmission with Raspberry Pi boards together with temperature and oxygen sensor devices. Culture ponds have been found to cause eddy water and cause sewage and suspensions to be collected in the center of the pond and removed for their intended purpose. The design of the cooling system showed that the temperature and oxygen in the culture pond can be controlled according to its purpose. Similarly, the use of IOT technology to control the operation of temperature and oxygen sensor devices can be controlled with Raspberry Pi boards, which are ready to send and receive data via a Web server in RaspPi, and alarms can be displayed on computers and LINE applications with satisfactory results. Evaluation and experimental cultivation of Chinese mitten crab in a traditional cold pond compared to a new type of culture pond designed and created. Eighty male and 80 female Chinese mitten crabs that were one week old in a culture pond with a 1- to 6-week cycle of traditional culture had an average survival rate of 79.17%, and those in the new type of pond culture had an average survival rate of 89.58%. The evaluation also revealed that male crabs have a higher survival rate than female crabs and have a satisfactory, reliable, and objective growth rate. 06-29-2024 <![CDATA[ <p>With the expansion of IoT platforms for smart livestock farming applications and their application to agriculture, farmers are becoming more interested. This research paper presents innovative IoT solutions for the economic propagation of animals using Raspberry Pi boards. This research has two main objectives (1) design and build a cooling system that continuously controls the temperature between 8-20 degrees Celsius and controls the oxygen content in the water between 4-8 mg/L. This control uses IOT technology to control the sending and receiving of data with the Raspberry Pi board. (2) The experimental cultivation of Chinese mitten crab in a traditional cold pond was compared to that of a new type of culture pond. The design and creation of the Chinese mitten crab culture pond and the use of IOT technology to control data transmission with Raspberry Pi boards together with temperature and oxygen sensor devices. Culture ponds have been found to cause eddy water and cause sewage and suspensions to be collected in the center of the pond and removed for their intended purpose. The design of the cooling system showed that the temperature and oxygen in the culture pond can be controlled according to its purpose. Similarly, the use of IOT technology to control the operation of temperature and oxygen sensor devices can be controlled with Raspberry Pi boards, which are ready to send and receive data via a Web server in RaspPi, and alarms can be displayed on computers and LINE applications with satisfactory results. Evaluation and experimental cultivation of Chinese mitten crab in a traditional cold pond compared to a new type of culture pond designed and created. Eighty male and 80 female Chinese mitten crabs that were one week old in a culture pond with a 1- to 6-week cycle of traditional culture had an average survival rate of 79.17%, and those in the new type of pond culture had an average survival rate of 89.58%. The evaluation also revealed that male crabs have a higher survival rate than female crabs and have a satisfactory, reliable, and objective growth rate.</p> ]]> Innovation IoT Solutions for Economic Animal Propagation Using Raspberry Pi Boards soawanee prachayagringkai nuttee thungsuk teerawut savangboon akharakit chaithanakulwat doi: 10.18280/ijcmem.120205 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 155 10.18280/ijcmem.120205 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120205 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120204 All of the applications that are used in industrial processes require solutions that have a particular chemical strength of the fluids or chemicals that are being under consideration for analysis. When a full-strength solution is combined with water in the proportions that are needed, it is possible to produce the particular concentrations that are wanted. The regulation of the concentration of hydrogen peroxide which produced in an electrolysis process has been investigated over the course of this article. An examination of the impact that various controllers, such as P, PI, PID, and fuzzy logic controllers, have on the process model is presented in this work with the help of MATLAB/SIMULINK as a simulation program. Using fuzzy logic controllers showed that the rising time dropped to 0.3 seconds and the settling time to 0.4 seconds, with no overshoot or undershoot. 06-29-2024 <![CDATA[ <p>All of the applications that are used in industrial processes require solutions that have a particular chemical strength of the fluids or chemicals that are being under consideration for analysis. When a full-strength solution is combined with water in the proportions that are needed, it is possible to produce the particular concentrations that are wanted. The regulation of the concentration of hydrogen peroxide which produced in an electrolysis process has been investigated over the course of this article. An examination of the impact that various controllers, such as P, PI, PID, and fuzzy logic controllers, have on the process model is presented in this work with the help of MATLAB/SIMULINK as a simulation program. Using fuzzy logic controllers showed that the rising time dropped to 0.3 seconds and the settling time to 0.4 seconds, with no overshoot or undershoot.</p> ]]> Enhanced Concentration Control in Electrochemical Reactors Using Fuzzy Logic with Conventional PID and PI Controllers maha n. ismael fatin h. yahya doi: 10.18280/ijcmem.120204 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 147 10.18280/ijcmem.120204 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120204 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120203 This paper explores the field of FPGA implementation and emulation of memristor devices, providing insights into the advancements, challenges, and future directions. The paper discusses various techniques used for FPGA-based memristor emulation, emphasizing the importance of accurate memristor modeling and performance evaluation. It identifies challenges in the field, including improving accuracy, scalability, real-time adaptation, standardization, integration with design tools, and exploring novel applications. Additionally, the results of the study show that FPGAs are one of the viable solutions for emulating memristors. The study concludes that FPGA based memristor emulation holds a promise for studying memristor-based circuits and systems, with potential applications in neuromorphic computing, machine learning accelerators, and analog/mixed-signal circuit design. 06-29-2024 <![CDATA[ <p>This paper explores the field of FPGA implementation and emulation of memristor devices, providing insights into the advancements, challenges, and future directions. The paper discusses various techniques used for FPGA-based memristor emulation, emphasizing the importance of accurate memristor modeling and performance evaluation. It identifies challenges in the field, including improving accuracy, scalability, real-time adaptation, standardization, integration with design tools, and exploring novel applications. Additionally, the results of the study show that FPGAs are one of the viable solutions for emulating memristors. The study concludes that FPGA based memristor emulation holds a promise for studying memristor-based circuits and systems, with potential applications in neuromorphic computing, machine learning accelerators, and analog/mixed-signal circuit design.</p> ]]> Exploring FPGA Implementation and Emulation of Memristor Devices zeyad aklah amean al-safi hussein t. hassan doi: 10.18280/ijcmem.120203 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 135 10.18280/ijcmem.120203 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120203 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120202 In this research Python machine learning module sklearn has been utilized to solve the Markov model. Markov modelling of the COVID-19 dynamics with air quality index (AQI), $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, and $\mathrm{O}_3$, respectively. Data of the Chhattisgarh state of India has been analyzed in two phases. In phase-1 the time duration is from March 15, 2020, to May 01, 2020, and for phase-2 it is from Jun 01, 2020, to Jul 15, 2020. It has been noticed that initially change in AQI from 103 to 84.83 changed disease dynamics, and the first cases of COVID-19 reported. In the next two fortnights March 15,2020 , and April 01,2020 , the dynamics are the same, later the AQI change from 84.83 to 63.83 , but no change reported disease dynamics from April 15, 2020, to Jul 15, 2020. In phase 1, a cyclic trend has been observed for changes concerning $\mathrm{PM}_{-2.5}$. The trends for $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, and $\mathrm{O}_3$, respectively are same, but for $\mathrm{O}_3$ it is different. COVID-19 reports a negative correlation with AQI, $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$. Moreover, a positive correlation with $\mathrm{O}_3$. This proves that the lockdown and ban on transport activities improved AQI, $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, but not $\mathrm{O}_3$. 06-29-2024 <![CDATA[ <p>In this research Python machine learning module sklearn has been utilized to solve the Markov model. Markov modelling of the COVID-19 dynamics with air quality index (AQI), $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, and $\mathrm{O}_3$, respectively. Data of the Chhattisgarh state of India has been analyzed in two phases. In phase-1 the time duration is from March 15, 2020, to May 01, 2020, and for phase-2 it is from Jun 01, 2020, to Jul 15, 2020. It has been noticed that initially change in AQI from 103 to 84.83 changed disease dynamics, and the first cases of COVID-19 reported. In the next two fortnights March 15,2020 , and April 01,2020 , the dynamics are the same, later the AQI change from 84.83 to 63.83 , but no change reported disease dynamics from April 15, 2020, to Jul 15, 2020. In phase 1, a cyclic trend has been observed for changes concerning $\mathrm{PM}_{-2.5}$. The trends for $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, and $\mathrm{O}_3$, respectively are same, but for $\mathrm{O}_3$ it is different. COVID-19 reports a negative correlation with AQI, $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$. Moreover, a positive correlation with $\mathrm{O}_3$. This proves that the lockdown and ban on transport activities improved AQI, $\mathrm{PM}_{-2.5}$, $\mathrm{NO}_2$, $\mathrm{PM}_{-10}$, but not $\mathrm{O}_3$.</p> ]]> Machine Learning for Markov Modeling of COVID-19 Dynamics Concerning Air Quality Index, $\mathrm{PM}_{-2.5}, \mathrm{NO}_2, \mathrm{PM}_{-10}$, and $\mathrm{O}_3$ izaz ullah khan mehran ullah seema tripathi motiram sahu anwar zeb faiza anil kumar doi: 10.18280/ijcmem.120202 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 121 10.18280/ijcmem.120202 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120202 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120201 Face detection and recognition (FRD) technology is a very useful tool that involves taking pictures of people's faces and assessing their biological characteristics to compare and match facial data recorded in databases. Owing to its numerous advantages, including noncontact functionality, time and attendance tracking, medical applications and enhanced security and surveillance, this technology is finding increased application in a variety of contexts. Considering that the face images captured by these devices are influenced by many factors, such as light, posture, and backdrop environment, the recognition rate of current face recognition models remains inadequate. This paper presents a model that combines the You Only Live Once (YOLO) v3 algorithm for face detection with VGG16 networks for efficient face recognition. The model is specifically made to handle scenarios in which people share facial traits and to recognize people in various settings with accuracy. This paper uses two different public datasets to train and test the proposed model, WIDER FACE dataset for YOLO v3 and the Labelled Faces in the Wild (LFW) dataset for the VGG 16 networks, the improved network model performed better in identification and is more robust. Furthermore, the YOLO v3 network scored a little lesser accuracy of 95.9% in face detection, while the VGG 16 network achieved an amazing 96.2% accuracy in face recognition. 06-29-2024 <![CDATA[ <p>Face detection and recognition (FRD) technology is a very useful tool that involves taking pictures of people's faces and assessing their biological characteristics to compare and match facial data recorded in databases. Owing to its numerous advantages, including noncontact functionality, time and attendance tracking, medical applications and enhanced security and surveillance, this technology is finding increased application in a variety of contexts. Considering that the face images captured by these devices are influenced by many factors, such as light, posture, and backdrop environment, the recognition rate of current face recognition models remains inadequate. This paper presents a model that combines the You Only Live Once (YOLO) v3 algorithm for face detection with VGG16 networks for efficient face recognition. The model is specifically made to handle scenarios in which people share facial traits and to recognize people in various settings with accuracy. This paper uses two different public datasets to train and test the proposed model, WIDER FACE dataset for YOLO v3 and the Labelled Faces in the Wild (LFW) dataset for the VGG 16 networks, the improved network model performed better in identification and is more robust. Furthermore, the YOLO v3 network scored a little lesser accuracy of 95.9% in face detection, while the VGG 16 network achieved an amazing 96.2% accuracy in face recognition.</p> ]]> An Effective Face Detection and Recognition Model Based on Improved YOLO v3 and VGG 16 Networks nashwan saleh ali alaa fares alsafo hiba dhiya ali mustafa sabah taha doi: 10.18280/ijcmem.120201 International Journal of Computational Methods and Experimental Measurements 06-29-2024 International Journal of Computational Methods and Experimental Measurements 06-29-2024 2024 12 2 Article 107 10.18280/ijcmem.120201 https://www.acadlore.com/article/IJCMEM/2024_12_2/ijcmem.120201 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120111 In military defence and wildlife conservation operations, detecting camouflage in images poses a significant challenge. This research investigates the efficacy of deep learning techniques, including Convolutional Neural Networks (CNN), Artificial Neural Networks (ANN), and Long Short-Term Memory (LSTM), in addressing this challenge. The study meticulously evaluates each model's performance using metrics such as average accuracy, validation accuracy, and loss measures across well-known benchmark datasets comprising camouflaged and non-camouflaged images. Notably, the CNN + ANN Pipeline model emerges as the most effective, achieving a remarkable average accuracy of 91.37%. This model, together with the standalone CNN, outperforms the ANN and LSTM models in terms of camouflage detection. The discoveries advance the state-of-the-art in image analysis while also having practical implications for real-world applications. In military settings, good camouflage detection can improve situational awareness and danger detection capabilities. Similarly, automated camouflage detection helps monitor and protect endangered species by detecting hidden creatures or potential threats. Overall, this study highlights the ability of deep learning techniques to greatly improve visual analytic tasks across a variety of domains. 03-30-2024 <![CDATA[ <p>In military defence and wildlife conservation operations, detecting camouflage in images poses a significant challenge. This research investigates the efficacy of deep learning techniques, including Convolutional Neural Networks (CNN), Artificial Neural Networks (ANN), and Long Short-Term Memory (LSTM), in addressing this challenge. The study meticulously evaluates each model's performance using metrics such as average accuracy, validation accuracy, and loss measures across well-known benchmark datasets comprising camouflaged and non-camouflaged images. Notably, the CNN + ANN Pipeline model emerges as the most effective, achieving a remarkable average accuracy of 91.37%. This model, together with the standalone CNN, outperforms the ANN and LSTM models in terms of camouflage detection. The discoveries advance the state-of-the-art in image analysis while also having practical implications for real-world applications. In military settings, good camouflage detection can improve situational awareness and danger detection capabilities. Similarly, automated camouflage detection helps monitor and protect endangered species by detecting hidden creatures or potential threats. Overall, this study highlights the ability of deep learning techniques to greatly improve visual analytic tasks across a variety of domains.</p> ]]> Revealing Hidden Patterns: A Deep Learning Approach to Camouflage Detection rita kamble pothuraju rajarajeswari doi: 10.18280/ijcmem.120111 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 97 10.18280/ijcmem.120111 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120111 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120110 Breast tumors have become one of the most frequent illnesses among women, with 287,850 new cases projected to be discovered in 2022. Of those, 43,250 women passed away from this malignancy. The mortality rate for cancer might be decreased through early detection. Despite this, employing mammography photographs to manually identify this kind of cancer is a challenging process that always demands an expert. In the literature, a number of AI-based (Artificial Intelligence) strategies have been proposed. However, they still deal with issues including irrelevant feature extraction, inadequate training models, and similarities between cancerous and non-cancerous areas. In order to identify breast cancer, this research suggested an SMO-MAFNet-Hybrid Alexnet model. The images in this study were first preprocessed to get rid of noise. After that, the multi-attention fusion network (MAFNet) is used to extract features. The Spider Monkey Optimization (SMO) method is utilized in this work to optimize the learning rate in MAFNet. Following feature extraction, classification is done using the AlexNet model. In this work, hybrid optimization, namely Ant Colony Optimization-Reptile Search Algorithm (ACO-RSA), is applied to fine-tune the hyperparameters in AlexNet classification. The suggested method was tested using the CBIS-DDSM (Curated breast imaging subset of Digital Database for Screening Mammography) dataset and demonstrated an accuracy of 98%, outperforming previous models. 03-30-2024 <![CDATA[ <p>Breast tumors have become one of the most frequent illnesses among women, with 287,850 new cases projected to be discovered in 2022. Of those, 43,250 women passed away from this malignancy. The mortality rate for cancer might be decreased through early detection. Despite this, employing mammography photographs to manually identify this kind of cancer is a challenging process that always demands an expert. In the literature, a number of AI-based (Artificial Intelligence) strategies have been proposed. However, they still deal with issues including irrelevant feature extraction, inadequate training models, and similarities between cancerous and non-cancerous areas. In order to identify breast cancer, this research suggested an SMO-MAFNet-Hybrid Alexnet model. The images in this study were first preprocessed to get rid of noise. After that, the multi-attention fusion network (MAFNet) is used to extract features. The Spider Monkey Optimization (SMO) method is utilized in this work to optimize the learning rate in MAFNet. Following feature extraction, classification is done using the AlexNet model. In this work, hybrid optimization, namely Ant Colony Optimization-Reptile Search Algorithm (ACO-RSA), is applied to fine-tune the hyperparameters in AlexNet classification. The suggested method was tested using the CBIS-DDSM (Curated breast imaging subset of Digital Database for Screening Mammography) dataset and demonstrated an accuracy of 98%, outperforming previous models.</p> ]]> Detection of Breast Cancer in Mammogram Images Using Multi Attention Feature Extraction with Hybrid RSA Based AlexNet naga jagadesh bommagani manjunatha basavannappa challageri nunsavatu v naik hanumantha rao jalla syed ziaur rahman anandhi rajamani jayadharmarajan doi: 0.18280/ijcmem.120110 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 83 0.18280/ijcmem.120110 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120110 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120109 A problem of heat transfer by conduction, convection, and radiation has been studied for both steady and unsteady states. A numerical technique based on the finite difference method was adopted to solve the mathematical boundary value problem, which was created under some conditions with different values of physical parameters. The solution started with an unsteady state, reaching a steady state after many iterations. The effect of various parameters has been discussed for different temperatures of the parallel walls, and the governing equations have been established, which appear to be of the parabolic type. They were treated numerically using the Alternating Direction Implicit Method, which is considered good in stability with acceptable accuracy. Both cases for the steady and unsteady state, which usually arise in the discussion of fluid flow or heat transfer problems, are treated in this paper as one case dissimilar to the previous works, and this is the main goal of the present article. 03-30-2024 <![CDATA[ <p>A problem of heat transfer by conduction, convection, and radiation has been studied for both steady and unsteady states. A numerical technique based on the finite difference method was adopted to solve the mathematical boundary value problem, which was created under some conditions with different values of physical parameters. The solution started with an unsteady state, reaching a steady state after many iterations. The effect of various parameters has been discussed for different temperatures of the parallel walls, and the governing equations have been established, which appear to be of the parabolic type. They were treated numerically using the Alternating Direction Implicit Method, which is considered good in stability with acceptable accuracy. Both cases for the steady and unsteady state, which usually arise in the discussion of fluid flow or heat transfer problems, are treated in this paper as one case dissimilar to the previous works, and this is the main goal of the present article.</p> ]]> Numerical Solution for Both Steady and Unsteady State of Fluid Flow Between Two Heated Parallel Walls ahmed muhammmed juma’a doi: 10.18280/ijcmem.120109 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 77 10.18280/ijcmem.120109 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120109 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120108 The aim of the attempt is to build a mechanism for objective evaluation of the autonomous nervous system (ANS) for disease diagnosis at an early stage. With the experience of data collection from various control subjects, BARC has identified eight different pulse morphologies. A Peripheral Pulse Analyser (PPA) measures peripheral blood flow. Blood flow was measured in control subjects (100) and patients (100). The morphology of a person's pulse changes throughout time. Pulse morphologies vary according to age, disease, and other parameters. More than 8500 signals from 200 humans were tested. Various pattern-matching and classification techniques are given in this research to detect the existence of specific pulse shapes in obtained PPA signals. Peaks of PPA blood flow patterns are detected, and features are extracted from the sample pattern. Various machine learning (ML) algorithms are used to identify various pulse shapes depending on the parameters of extracted features. We observed that in one PPA signal of the duration of 300 seconds, 3 to 4 defined pulse morphologies out of 8 are available. Every pulse morphology is different from the others. After training, the system was able to detect pulse shapes to assess the ANS of the subject with more than 94% to 97% accuracy. The proposed system will assist the doctor in making a decision quickly based on a few processed parameters rather than assessing several individual parameters at a crucial time. The output of the system is the assessment report of ANS. This is an attempt to replace traditional Ayurvedic pulse examination methos for disease detection. 03-30-2024 <![CDATA[ <p>The aim of the attempt is to build a mechanism for objective evaluation of the autonomous nervous system (ANS) for disease diagnosis at an early stage. With the experience of data collection from various control subjects, BARC has identified eight different pulse morphologies. A Peripheral Pulse Analyser (PPA) measures peripheral blood flow. Blood flow was measured in control subjects (100) and patients (100). The morphology of a person's pulse changes throughout time. Pulse morphologies vary according to age, disease, and other parameters. More than 8500 signals from 200 humans were tested. Various pattern-matching and classification techniques are given in this research to detect the existence of specific pulse shapes in obtained PPA signals. Peaks of PPA blood flow patterns are detected, and features are extracted from the sample pattern. Various machine learning (ML) algorithms are used to identify various pulse shapes depending on the parameters of extracted features. We observed that in one PPA signal of the duration of 300 seconds, 3 to 4 defined pulse morphologies out of 8 are available. Every pulse morphology is different from the others. After training, the system was able to detect pulse shapes to assess the ANS of the subject with more than 94% to 97% accuracy. The proposed system will assist the doctor in making a decision quickly based on a few processed parameters rather than assessing several individual parameters at a crucial time. The output of the system is the assessment report of ANS. This is an attempt to replace traditional Ayurvedic pulse examination methos for disease detection.</p> ]]> Machine Learning Approach Combined with Statistical Features in the Classification of Peripheral Pulse Morphology manjusha deshmukh sujata bhairnallykar sheetal bukkawar ragini sharma sarita kale doi: 10.18280/ijcmem.120108 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 69 10.18280/ijcmem.120108 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120108 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120107 When wireless nodes communicate without the use of infrastructure, the network is subject to security breaches. Mobile Adhoc Network (MANET) is one of the most vulnerable wireless networks in terms of security breaches. The most common types of security breaches are intruders and attackers, whose tasks are to reduce the internal performance of the network. Many research studies are focused on detecting and preventing these two security threads. This article focuses on intruder and black hole attackers and their communication. Several techniques were proposed for thwart the intruders and attackers in the Mobile Adhoc Network communication by using the modern technologies which are an additional load to the nodes operation and these techniques could not be able to predict the attacker before it was done. To achieve this goal, this article proposed the Watch Dog approach involves routing protocol to monitoring the forwarding time of all nodes in the transmission. Delays in forwarded time nodes could indicate an intruder, while discarding the forwarded node could indicate a black hole attacker. The proposed Watch Dog routing algorithm with classification technique was implemented with a network simulator with Adhoc On Demand Vector protocol named as WD-AODV, and the simulation results were compared to a modern techniques of Fuzzy Logic based AODV (FL-AODV), Machine Learning-based AODV (ML-AODV) and Artificial Intelligence based AODV (AI-AODV) routing protocol. The compared results of attack rates, attack detection time, Packet delivery ratio and End to End delay showed that the Watch Dog-based attacker and intruder detection methods perform better by more than 59%, with excellent performance factors of 69%. 03-30-2024 <![CDATA[ <p>When wireless nodes communicate without the use of infrastructure, the network is subject to security breaches. Mobile Adhoc Network (MANET) is one of the most vulnerable wireless networks in terms of security breaches. The most common types of security breaches are intruders and attackers, whose tasks are to reduce the internal performance of the network. Many research studies are focused on detecting and preventing these two security threads. This article focuses on intruder and black hole attackers and their communication. Several techniques were proposed for thwart the intruders and attackers in the Mobile Adhoc Network communication by using the modern technologies which are an additional load to the nodes operation and these techniques could not be able to predict the attacker before it was done. To achieve this goal, this article proposed the Watch Dog approach involves routing protocol to monitoring the forwarding time of all nodes in the transmission. Delays in forwarded time nodes could indicate an intruder, while discarding the forwarded node could indicate a black hole attacker. The proposed Watch Dog routing algorithm with classification technique was implemented with a network simulator with Adhoc On Demand Vector protocol named as WD-AODV, and the simulation results were compared to a modern techniques of Fuzzy Logic based AODV (FL-AODV), Machine Learning-based AODV (ML-AODV) and Artificial Intelligence based AODV (AI-AODV) routing protocol. The compared results of attack rates, attack detection time, Packet delivery ratio and End to End delay showed that the Watch Dog-based attacker and intruder detection methods perform better by more than 59%, with excellent performance factors of 69%.</p> ]]> Enhancing MANET Security: A Watch Dog Routing Algorithm Approach for Intruder and Black Hole Attack Detection s. hemalatha s vijayakumar arunkumar gurunathan anbarasi masilamani g durga prasad kiruthiga balasubramaniyan chitra devi d lakshmana phaneendra maguluri doi: 10.18280/ijcmem.120107 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 61 10.18280/ijcmem.120107 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120107 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120106 The impact of technological developments has now led to a transformation in the preparation of financial statements. By applying machine learning, auditors can easily increase anomalies detection. The purpose of this study is to determine the effect of optimism, innovativeness, perceived usefulness, and perceived ease of use on auditors’ intention to use machine learning. Data were collected using an online questionnaire and analyzed using the Structural Equation Modeling-Partial Least Square (SEM-PLS). The sample in this study used a nonprobability sampling and has a sample size of 100 respondents from auditors who work in a Public Accounting Firm in DKI Jakarta and Tangerang areas. The results of testing this study using SmartPLS 4 are optimism has a significant effect on perceived usefulness and perceived ease of use, while innovativeness only has a significant effect on perceived ease of use. In addition, perceived ease of use has a significant effect on perceived usefulness. This study implies that auditors' perception of the usefulness can influence the intention to use machine learning. However, perceived ease of use does not affect the intention to use machine learning. Therefore, we suggest that audit firms could establish training programs to enhance digital skills for auditor. 03-30-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The impact of technological developments has now led to a transformation in the preparation of financial statements. By applying machine learning, auditors can easily increase anomalies detection. The purpose of this study is to determine the effect of optimism, innovativeness, perceived usefulness, and perceived ease of use on auditors’ intention to use machine learning. Data were collected using an online questionnaire and analyzed using the Structural Equation Modeling-Partial Least Square (SEM-PLS). The sample in this study used a nonprobability sampling and has a sample size of 100 respondents from auditors who work in a Public Accounting Firm in DKI Jakarta and Tangerang areas. The results of testing this study using SmartPLS 4 are optimism has a significant effect on perceived usefulness and perceived ease of use, while innovativeness only has a significant effect on perceived ease of use. In addition, perceived ease of use has a significant effect on perceived usefulness. This study implies that auditors' perception of the usefulness can influence the intention to use machine learning. However, perceived ease of use does not affect the intention to use machine learning. Therefore, we suggest that audit firms could establish training programs to enhance digital skills for auditor.</span></p> ]]> Embracing AI in Auditing: An Examination of Auditor Readiness Through the TRAM Framework bambang leo handoko dinda sabrina indrawati salsabila rafifa putri zulkarnaen doi: 10.18280/ijcmem.120106 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 53 10.18280/ijcmem.120106 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120106 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120105 The focal objective of optimizing drilling processes is to mitigate challenges tied to the operation. However, the triumph of mineral drilling relies on the availability of pertinent data to ensure effectiveness. For efficient and successful drilling, an optimization approach necessitates access to pertinent data, especially concerning the physicochemical properties of the rock and operational parameters of the machine. In this study, our focus is on optimizing specific energy, a critical metric for assessing mining drilling efficiency. This measure evaluates the energy used during drilling per unit volume of rock extracted. Considering the complexity of factors involved, treating the selection of the operational mode governing specific energy as a form of multi-criteria decision-making is justifiable. This method involves an in-depth analysis of the problem's underlying structure. Experimental measures were used to validate the proposed optimization approach. The paper delves into evaluating the differences in rankings derived from the TOPSIS and VIKOR methods. A ranking similarity coefficient is employed to compare the rankings against experimental values. Ultimately, the available choices are prioritized, and the most suitable operating mode for the drilling machine is determined. The study's comparative analysis using TOPSIS and VIKOR methodologies leads to the discovery of the best operational modes for drilling machines, highlighting the subtle differences in how well the two methods work. By using a ranking similarity coefficient, this study not only shows what each method's rankings mean in real life compared to experimental values, but it also gives a plan for improving the efficiency of drilling machines by carefully adjusting their parameters. Such insights contribute significantly to the field of drilling optimization, showcasing a methodical approach to energy conservation and operational efficiency. 03-30-2024 <![CDATA[ <p>The focal objective of optimizing drilling processes is to mitigate challenges tied to the operation. However, the triumph of mineral drilling relies on the availability of pertinent data to ensure effectiveness. For efficient and successful drilling, an optimization approach necessitates access to pertinent data, especially concerning the physicochemical properties of the rock and operational parameters of the machine. In this study, our focus is on optimizing specific energy, a critical metric for assessing mining drilling efficiency. This measure evaluates the energy used during drilling per unit volume of rock extracted. Considering the complexity of factors involved, treating the selection of the operational mode governing specific energy as a form of multi-criteria decision-making is justifiable. This method involves an in-depth analysis of the problem's underlying structure. Experimental measures were used to validate the proposed optimization approach. The paper delves into evaluating the differences in rankings derived from the TOPSIS and VIKOR methods. A ranking similarity coefficient is employed to compare the rankings against experimental values. Ultimately, the available choices are prioritized, and the most suitable operating mode for the drilling machine is determined. The study's comparative analysis using TOPSIS and VIKOR methodologies leads to the discovery of the best operational modes for drilling machines, highlighting the subtle differences in how well the two methods work. By using a ranking similarity coefficient, this study not only shows what each method's rankings mean in real life compared to experimental values, but it also gives a plan for improving the efficiency of drilling machines by carefully adjusting their parameters. Such insights contribute significantly to the field of drilling optimization, showcasing a methodical approach to energy conservation and operational efficiency.</p> ]]> Enhancing Sustainability Through Drilling Machine Efficiency: A Comparative Analysis of TOPSIS and VIKOR Methods for Energy Optimization hafidha ramdani zoubir aoulmi messaoud louafi moussa attia mohammed mebarkia doi: 10.18280/ijcmem.120105 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 45 10.18280/ijcmem.120105 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120105 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120104 Rice, a global staple crop, plays a crucial role in feeding approximately half of the global population. Nevertheless, the persistent spread of diseases poses a significant threat to rice production. Therefore, accurately identifying rice diseases is of paramount practical importance. The proposed approach introduces an innovative hybrid architecture for image classification, harnessing the strengths of both Vision Transformers (ViT) and Convolutional Neural Networks (CNNs). This research investigates five primary diseases affecting rice crops: Blast, Brown Spot, Tungro, False smut, and Bacterial Sheath Blight. Approximately 8000 images of these specific rice leaf diseases were employed for training purposes in the study. What distinguishes this method is its unique integration of a CNN block within the transformer layers, deviating from the traditional ViT architecture. Vision Transformers (ViTs), recognized for their exceptional performance in image classification, excel in providing global insights through attention-based mechanisms. Nevertheless, their model complexity can obscure the decision-making process, and ambiguous attention maps can lead to erroneous correlations among image patches. The incorporation of CNNs in this approach serves to address these challenges by effectively capturing local patterns. This synergistic combination enhances the model's robustness to variations in input data, such as changes in scale, perspective, or context. With the utilization of the proposed hybrid ViT-CNN model architecture, the model achieves remarkable results, boasting 100 percent accuracy and top-5 accuracy, along with a precision of 93.84 percent. Through this hybrid model, we have obtained satisfactory outcomes, surpassing the performance of the latest transformer models in the realm of rice leaf disease identification. 03-30-2024 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Rice, a global staple crop, plays a crucial role in feeding approximately half of the global population. Nevertheless, the persistent spread of diseases poses a significant threat to rice production. Therefore, accurately identifying rice diseases is of paramount practical importance. The proposed approach introduces an innovative hybrid architecture for image classification, harnessing the strengths of both Vision Transformers (ViT) and Convolutional Neural Networks (CNNs). This research investigates five primary diseases affecting rice crops: Blast, Brown Spot, Tungro, False smut, and Bacterial Sheath Blight. Approximately 8000 images of these specific rice leaf diseases were employed for training purposes in the study. What distinguishes this method is its unique integration of a CNN block within the transformer layers, deviating from the traditional ViT architecture. Vision Transformers (ViTs), recognized for their exceptional performance in image classification, excel in providing global insights through attention-based mechanisms. Nevertheless, their model complexity can obscure the decision-making process, and ambiguous attention maps can lead to erroneous correlations among image patches. The incorporation of CNNs in this approach serves to address these challenges by effectively capturing local patterns. This synergistic combination enhances the model's robustness to variations in input data, such as changes in scale, perspective, or context. With the utilization of the proposed hybrid ViT-CNN model architecture, the model achieves remarkable results, boasting 100 percent accuracy and top-5 accuracy, along with a precision of 93.84 percent. Through this hybrid model, we have obtained satisfactory outcomes, surpassing the performance of the latest transformer models in the realm of rice leaf disease identification.</span></p> ]]> A Hybrid ViT-CNN Model Premeditated for Rice Leaf Disease Identification tharani pavithra p. baranidharan b. doi: 10.18280/ijcmem.120104 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 35 10.18280/ijcmem.120104 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120104 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120103 Selective laser sintering (SLS) is a typical procedure in powder-based 3D printing technology that produces items with great accuracy and precision. The powders used in SLS are granular and discontinuous, making them difficult to simulate using traditional computational techniques that rely on continuous methods, such as the finite element method (FEM) or finite difference (FD). This paper presents a system for accurately depicting the physical interactions of particles affected by a moving laser source using the discrete element method (DEM), performed numerically in Python. This DEM framework was used on polyamide 12 powder with various laser powers (2W, 4W, 5W) and scanning speeds (0.5m/s, 1m/s). The results and comparison with previous literature confirm that the DEM framework accurately depicts the temperature distribution in the laser-scanned powder bed. The effect of laser power and scan speed on fused surface size is explored and corroborated using previous studies, confirming the DEM's dependability and applicability for modelling powder-based additive manufacturing processes. 03-30-2024 <![CDATA[ <p>Selective laser sintering (SLS) is a typical procedure in powder-based 3D printing technology that produces items with great accuracy and precision. The powders used in SLS are granular and discontinuous, making them difficult to simulate using traditional computational techniques that rely on continuous methods, such as the finite element method (FEM) or finite difference (FD). This paper presents a system for accurately depicting the physical interactions of particles affected by a moving laser source using the discrete element method (DEM), performed numerically in Python. This DEM framework was used on polyamide 12 powder with various laser powers (2W, 4W, 5W) and scanning speeds (0.5m/s, 1m/s). The results and comparison with previous literature confirm that the DEM framework accurately depicts the temperature distribution in the laser-scanned powder bed. The effect of laser power and scan speed on fused surface size is explored and corroborated using previous studies, confirming the DEM's dependability and applicability for modelling powder-based additive manufacturing processes.</p> ]]> Modeling the Physics of Selective Laser Sintering Using the Discrete Element Method reda lakraimi hamid abouchadi mourad taha janan doi: 10.18280/ijcmem.120103 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 21 10.18280/ijcmem.120103 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120103 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120102 Applying solar radiation as a renewable energy source using photovoltaic panels has problems, such as work efficiency decreasing when the photovoltaic cell temperature is above the working temperature, thus requiring a cooling method. This research examines the cooling effect of photovoltaic panels using water spray with various types and diameters to reduce the temperature and performance of photovoltaic panels, which was carried out experimentally with solar radiation at 08:00-15:00 local time. The research results show that the water spray cooling system can reduce the temperature of the photovoltaic panel from 61.96 to 36.51℃ and increase efficiency from 10.98 to 14.47% with variations in the full cone nozzle with a hole diameter of 2 mm. Full cone nozzles can provide the best cooling performance compared to hollow cone nozzles and flat fan nozzles due to the more even distribution of water spray on the surface of the photovoltaic panel. Using different nozzle diameters also influences cooling. Based on the research results, the water spray cooling system effectively increases the work efficiency of photovoltaic panels with a 2 mm total cone nozzle variation, producing the highest efficiency. 03-30-2024 <![CDATA[ <p>Applying solar radiation as a renewable energy source using photovoltaic panels has problems, such as work efficiency decreasing when the photovoltaic cell temperature is above the working temperature, thus requiring a cooling method. This research examines the cooling effect of photovoltaic panels using water spray with various types and diameters to reduce the temperature and performance of photovoltaic panels, which was carried out experimentally with solar radiation at 08:00-15:00 local time. The research results show that the water spray cooling system can reduce the temperature of the photovoltaic panel from 61.96 to 36.51℃ and increase efficiency from 10.98 to 14.47% with variations in the full cone nozzle with a hole diameter of 2 mm. Full cone nozzles can provide the best cooling performance compared to hollow cone nozzles and flat fan nozzles due to the more even distribution of water spray on the surface of the photovoltaic panel. Using different nozzle diameters also influences cooling. Based on the research results, the water spray cooling system effectively increases the work efficiency of photovoltaic panels with a 2 mm total cone nozzle variation, producing the highest efficiency.</p> ]]> Optimization of Photovoltaic Performance Using a Water Spray Cooling System with Different Nozzle Types santiko wibowo zainal arifin rendy adhi rachmanto dwi aries himawanto singgih dwi prasetyo doi: 10.18280/ijcmem.120102 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 9 10.18280/ijcmem.120102 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120102 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120101 This research aims to model tourist visit data to West Nusa Tenggara Province (NTB) using a hybrid model, combining the dynamic neural network method as the core model with the wavelet method and fuzzy inference as tools to optimize the model. The model developed in this research is referred to as the Fuzzy Wavelet Dynamic Neural Networks (FW-DNN) Model. The FW-DNN model is a feed-forward dynamic neural network model that utilizes the Wavelet B-spline function as its activation function and TSK (Takagi-Sugeno-Kang) fuzzy inference as the method for information aggregation. The modeling results on both in-sample and out-sample data show that the proposed FW-DNN model is capable of representing the patterns in tourist visit data to NTB quite effectively. Similar results were also observed in the patterns of data for both domestic and international tourist visit numbers. Based on the root of mean square error (RMSE) indicator, the performance of the developed FW-DNN model for aggregated tourist visit data is 95185.09 for in-sample data and 22615.54 for out-sample data. Partial performance analysis of the FW-DNN model for international tourist visit data shows a value of 39848.94 for in-sample data and 5223.86 for out-sample data. Similarly, the FW-DNN model's performance for domestic tourist visit data is 39848.94 for in-sample data and 5223.86 for out-sample data. Practically, the results of this research can be input for the NTB Provincial government in determining tourism management and/or development policies, especially related to the provision of supporting facilities and infrastructure, or the private sector in an effort to optimize the carrying capacity and/or services for tourists visiting NTB. 03-30-2024 <![CDATA[ <p>This research aims to model tourist visit data to West Nusa Tenggara Province (NTB) using a hybrid model, combining the dynamic neural network method as the core model with the wavelet method and fuzzy inference as tools to optimize the model. The model developed in this research is referred to as the Fuzzy Wavelet Dynamic Neural Networks (FW-DNN) Model. The FW-DNN model is a feed-forward dynamic neural network model that utilizes the Wavelet B-spline function as its activation function and TSK (Takagi-Sugeno-Kang) fuzzy inference as the method for information aggregation. The modeling results on both in-sample and out-sample data show that the proposed FW-DNN model is capable of representing the patterns in tourist visit data to NTB quite effectively. Similar results were also observed in the patterns of data for both domestic and international tourist visit numbers. Based on the root of mean square error (RMSE) indicator, the performance of the developed FW-DNN model for aggregated tourist visit data is 95185.09 for in-sample data and 22615.54 for out-sample data. Partial performance analysis of the FW-DNN model for international tourist visit data shows a value of 39848.94 for in-sample data and 5223.86 for out-sample data. Similarly, the FW-DNN model's performance for domestic tourist visit data is 39848.94 for in-sample data and 5223.86 for out-sample data. Practically, the results of this research can be input for the NTB Provincial government in determining tourism management and/or development policies, especially related to the provision of supporting facilities and infrastructure, or the private sector in an effort to optimize the carrying capacity and/or services for tourists visiting NTB.</p> ]]> Fuzzy Wavelet Dynamic Neural Network Model for Modeling the Number of Tourist Visits to West Nusatenggara Province syamsul bahri lailia awalushaumi nuzla af’idatur robbaniyyah doi: 10.18280/ijcmem.120101 International Journal of Computational Methods and Experimental Measurements 03-30-2024 International Journal of Computational Methods and Experimental Measurements 03-30-2024 2024 12 1 Article 1 10.18280/ijcmem.120101 https://www.acadlore.com/article/IJCMEM/2024_12_1/ijcmem.120101 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110407 Heat and mass transfer in ternary nanofluid flows over diverse geometries is particularly significant for thermal management in electronic devices, precipitation, and filtration. Chemical reactions are vital processes that occur in a variety of natural and industrial systems. With this initiation, this research explores the impacts of chemical reaction and heat source/sink over MHD ternary nano fluid flow. In addition to this model, we assessed joule heating, viscous dissipation, and activation energy for the study. The ODEs are obtained by using appropriate similarities and the altered non-linear governing equations are solved numerically utilizing RKF-45 and shooting technique. The influence of vital variables on common profiles (flow velocity, thermal gradient, and mass transmission rate) is explored and deliberated graphically in three distinct scenarios. When compared to the other scenarios, the mass transfer for the case of fluid flow across a plate lowers as the activation energy parameter goes up. 12-29-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Heat and mass transfer in ternary nanofluid flows over diverse geometries is particularly significant for thermal management in electronic devices, precipitation, and filtration. Chemical reactions are vital processes that occur in a variety of natural and industrial systems. With this initiation, this research explores the impacts of chemical reaction and heat source/sink over MHD ternary nano fluid flow. In addition to this model, we assessed joule heating, viscous dissipation, and activation energy for the study. The ODEs are obtained by using appropriate similarities and the altered non-linear governing equations are solved numerically utilizing RKF-45 and shooting technique. The influence of vital variables on common profiles (flow velocity, thermal gradient, and mass transmission rate) is explored and deliberated graphically in three distinct scenarios. When compared to the other scenarios, the mass transfer for the case of fluid flow across a plate lowers as the activation energy parameter goes up.</span></p> ]]> Combined Impact of Joule Heating, Activation Energy, and Viscous Dissipation on Ternary Nanofluid Flow over Three Different Geometries kandavkovi mallikarjuna nihaal ulavathi shettar mahabaleshwar sang woo joo giulio lorenzini doi: 10.18280/ijcmem.110407 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 251 10.18280/ijcmem.110407 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110407 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110406 The quenching of a pre-mixed counter flame was studied experimentally, as described in this paper. Experimental research has been done on flames spreading in methane/air mixes in counter burners with various burner diameters. It has been determined how the counter burner diameter changes, the methane/air mixing ratio affects the flame burning velocity, and the quenching diameter. In this study, the quenching diameter was examined in relation to altering burner diameter (9, 12, 16, 19, and 23 mm) using a digital image processing technique. In counter flame, significant results were attained. The geometry of the burner edges and the air and fuel velocity have an impact on the quenching diameter in the counter flow. The top and bottom flame disc quenching diameters are nearly equal for both lean and rich combinations and grow with the burner diameter. The values of the quenching distance were smaller than the quenching diameter at the wide range of the equivalence ratio (0.46 12-29-2023 <![CDATA[ <p>The quenching of a pre-mixed counter flame was studied experimentally, as described in this paper. Experimental research has been done on flames spreading in methane/air mixes in counter burners with various burner diameters. It has been determined how the counter burner diameter changes, the methane/air mixing ratio affects the flame burning velocity, and the quenching diameter. In this study, the quenching diameter was examined in relation to altering burner diameter (9, 12, 16, 19, and 23 mm) using a digital image processing technique. In counter flame, significant results were attained. The geometry of the burner edges and the air and fuel velocity have an impact on the quenching diameter in the counter flow. The top and bottom flame disc quenching diameters are nearly equal for both lean and rich combinations and grow with the burner diameter. The values of the quenching distance were smaller than the quenching diameter at the wide range of the equivalence ratio (0.46 < φ < 1.57) for mixtures, and this behavior was likely caused by the dead space.</p> ]]> Influence of Burner Diameter on Premixed Flame Shape and Quenching lateef talab obaid hasanain a. abdul wahhab miqdam t. chaichan mohammed a. fayad gazy f. al-sumaily doi: 10.18280/ijcmem.110406 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 245 10.18280/ijcmem.110406 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110406 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110405 In vapor compression refrigeration systems, refrigerants are among the most significant parameters additional to the compressor, condenser, throttling device, and the evaporator. Non-condensable gases during refrigerant manufacturing affect chest freezer performance. The temperature of the refrigerant in the condenser and evaporator is influenced by the quality of the refrigerant and its concentration. To study this effect this work is carried out on a chest freezer working with R-134a, which has a capacity of 145 liters. A high percentage of non-condensable gases in samples 3 and 6 increases the temperature of the refrigerant condenser, increases the electricity consumption, and decreases the temperature of the refrigerant flow in the evaporator. This blocks the circulation of refrigerant throughout the system and for a long time the compressor may be damaged. Samples 2,4,5 which contain low non-condensable gases work similarly to standard sample 1 with a low effect on power and refrigerant circulation, so cooling capacity is not affected. 12-29-2023 <![CDATA[ <p>In vapor compression refrigeration systems, refrigerants are among the most significant parameters additional to the compressor, condenser, throttling device, and the evaporator. Non-condensable gases during refrigerant manufacturing affect chest freezer performance. The temperature of the refrigerant in the condenser and evaporator is influenced by the quality of the refrigerant and its concentration. To study this effect this work is carried out on a chest freezer working with R-134a, which has a capacity of 145 liters. A high percentage of non-condensable gases in samples 3 and 6 increases the temperature of the refrigerant condenser, increases the electricity consumption, and decreases the temperature of the refrigerant flow in the evaporator. This blocks the circulation of refrigerant throughout the system and for a long time the compressor may be damaged. Samples 2,4,5 which contain low non-condensable gases work similarly to standard sample 1 with a low effect on power and refrigerant circulation, so cooling capacity is not affected.</p> ]]> Chest Freezer Performance with Non-Condensable Gases louay a. mahdi hayder m. ali muna k. al-naame ali oodaaabd waleed k. alani salman h. omran hasanain a. abdul wahhab doi: 10.18280/ijcmem.110405 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 239 10.18280/ijcmem.110405 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110405 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110404 Many studies have indicated that only a non-uniform magnetic field can interact with flame, and a small laminar diffusion flame is more affected than a premixed or partially premixed flame. Additionally, the mechanism for magnet–flame interaction is due to the magnetic para-magnetism of oxygen in the air, which is diffused into the flame. However, the combustion characteristics of the flame subject to the influence of magnetic field are not fully understood yet. This paper describes a numerical study of influence of magnetic field on premixed flame on the counter burner. Laminar premixed flames for different LPG gas flow rates propagating in counter burner of a different magnetic field intensities 1000 to 5000 gauss have been numerically investigated. An influence of the changing a distance between magnetic poles and magnetic force on the flame behavior, combustion velocity and flame temperature has been analyzed. The simulation was carried out using ANSYS Fluent software version 17.0, with premixed flame-let model and the dynamics of premixed flame through counter vertical burner under influencing of magnetic field. CFD results were appeared in the area of counter flame. Flame disc diameter in the counter burner is decreased gradually with increase magnetic field intensity and it affects positively on the combustion velocity of fuel/ air mixtures, and this behavior due to probably caused by effect magnetic force on oxygen zone. While, the results CFD results were shown decrease in the combustion velocity with increasing the distance between magnetic poles. The results have been demonstrated by an increase in the distance between magnetic poles on the combustion for LPG mixtures with air at 150, 180 to 220 mm leads to a significant decrease in both flame temperature with 3.7% and 4.7%. So, there was slight effect on the flame temperature in the middle of the anti-flame disc with effect magnetic field. 12-29-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Many studies have indicated that only a non-uniform magnetic field can interact with flame, and a small laminar diffusion flame is more affected than a premixed or partially premixed flame. Additionally, the mechanism for magnet–flame interaction is due to the magnetic para-magnetism of oxygen in the air, which is diffused into the flame. However, the combustion characteristics of the flame subject to the influence of magnetic field are not fully understood yet. This paper describes a numerical study of influence of magnetic field on premixed flame on the counter burner. Laminar premixed flames for different LPG gas flow rates propagating in counter burner of a different magnetic field intensities 1000 to 5000 gauss have been numerically investigated. An influence of the changing a distance between magnetic poles and magnetic force on the flame behavior, combustion velocity and flame temperature has been analyzed. The simulation was carried out using ANSYS Fluent software version 17.0, with premixed flame-let model and the dynamics of premixed flame through counter vertical burner under influencing of magnetic field. CFD results were appeared in the area of counter flame. Flame disc diameter in the counter burner is decreased gradually with increase magnetic field intensity and it affects positively on the combustion velocity of fuel/ air mixtures, and this behavior due to probably caused by effect magnetic force on oxygen zone. While, the results CFD results were shown decrease in the combustion velocity with increasing the distance between magnetic poles. The results have been demonstrated by an increase in the distance between magnetic poles on the combustion for LPG mixtures with air at 150, 180 to 220 mm leads to a significant decrease in both flame temperature with 3.7% and 4.7%. So, there was slight effect on the flame temperature in the middle of the anti-flame disc with effect magnetic field.</span></p> ]]> CFD Simulation of Premixed Flame in Counter Burner under the Influence of a Magnetic Field ayad muter khlaf mehdi a. ehyaei hasanain a. abdul wahhab doi: 10.18280/ijcmem.110404 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 233 10.18280/ijcmem.110404 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110404 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110403 India is widely recognized for its wealthy heritage, subculture and myriad Indian cuisines. Indian Cuisines are famous around the globe for their taste and flavors. Indian Cuisines detection using computer vision-based methods has been limited till now because of the absence of a standard dataset needed to inspect the deep learning-based object detection models for detecting Indian Food Cuisine using electronic devices. Measuring food quantities in each item are very challenging tasks for a person. In this study the dataset IndianFoodNet has been introduced, containing more than 5500 high-quality images and 5000+ annotations spreading across thirty classes of Indian food items. A comparative study of various state-of-the-art object detection models- YOLO5, YOLO7 and YOLO8 has been provided in the study. Further, the model performance has been inspected and evaluated (As in training summary of YOLO at 5 epochs YOLO8 precision is 0.775 higher than precision of YOLO7 and YOLO5.Recall value of YOLO7 is least in comparison with YOLO5 having value 0.671 and YOLO8 having recall value 0.719) by qualitatively analyzing the prognostic made on the images of the dataset which are segregate for testing. 12-29-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">India is widely recognized for its wealthy heritage, subculture and myriad Indian cuisines. Indian Cuisines are famous around the globe for their taste and flavors. Indian Cuisines detection using computer vision-based methods has been limited till now because of the absence of a standard dataset needed to inspect the deep learning-based object detection models for detecting Indian Food Cuisine using electronic devices. Measuring food quantities in each item are very challenging tasks for a person. In this study the dataset IndianFoodNet has been introduced, containing more than 5500 high-quality images and 5000+ annotations spreading across thirty classes of Indian food items. A comparative study of various state-of-the-art object detection models- YOLO5, YOLO7 and YOLO8 has been provided in the study. Further, the model performance has been inspected and evaluated (As in training summary of YOLO at 5 epochs YOLO8 precision is 0.775 higher than precision of YOLO7 and YOLO5.Recall value of YOLO7 is least in comparison with YOLO5 having value 0.671 and YOLO8 having recall value 0.719) by qualitatively analyzing the prognostic made on the images of the dataset which are segregate for testing.</span></p> ]]> IndianFoodNet: Detecting Indian Food Items Using Deep Learning ritu agarwal tanupriya choudhury neelu j. ahuja tanmay sarkar doi: 10.18280/ijcmem.110403 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 221 10.18280/ijcmem.110403 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110403 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110402 The main duty of engineers is to guarantee that structures are both erect and adhere to codes, which proves their outstanding functionality and economic viability. In today's elastic materials, the von Mises stress values have to be verified when examining fatigue or failure. In the domains of heavy lifting, robotics, mechanical and offshore engineering, oil and gas engineering, and civil engineering, the Von Mises criteria are among the most often used benchmarks for assessing productivity conditions. In this study, seven I-beams models will be built, the first model without holes and the other six models with holes in various shapes (square, triangular, circular, hexagonal, and rectangular). The ANSYS program will be used to solve it using the finite element method. For the upper surface of these models, equal loads will be applied. The findings demonstrate that the shear stress values for the seven models were less than the shear stress values of the metal, which came to (370MPa), in line with the theory of maximum shear stress. With a value of (62.7MPa), the second-best model was the best. One of the most important conclusions when comparing the values of von Mess stresses with the von Mess theory of stress is that the third model (with rectangular openings) performed better than the other models when compared to the first model because its value was the same in both models (370MPa). The seventh model (hexagonal holes) had the lowest maximum value of stress intensity at 261MPa, per the results. being aware that this model weighs (70Kg) less than the first. 12-29-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The main duty of engineers is to guarantee that structures are both erect and adhere to codes, which proves their outstanding functionality and economic viability. In today's elastic materials, the von Mises stress values have to be verified when examining fatigue or failure. In the domains of heavy lifting, robotics, mechanical and offshore engineering, oil and gas engineering, and civil engineering, the Von Mises criteria are among the most often used benchmarks for assessing productivity conditions. In this study, seven I-beams models will be built, the first model without holes and the other six models with holes in various shapes (square, triangular, circular, hexagonal, and rectangular). The ANSYS program will be used to solve it using the finite element method. For the upper surface of these models, equal loads will be applied. The findings demonstrate that the shear stress values for the seven models were less than the shear stress values of the metal, which came to (370MPa), in line with the theory of maximum shear stress. With a value of (62.7MPa), the second-best model was the best. One of the most important conclusions when comparing the values of von Mess stresses with the von Mess theory of stress is that the third model (with rectangular openings) performed better than the other models when compared to the first model because its value was the same in both models (370MPa). The seventh model (hexagonal holes) had the lowest maximum value of stress intensity at 261MPa, per the results. being aware that this model weighs (70Kg) less than the first.</span></p> ]]> Stress Distribution in Cantilever Beams with Different Hole Shapes: A Numerical Analysis hussein mohammed ali majid khaleel najem emad toma karash jamal nayief sultan doi: 10.18280/ijcmem.110402 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 205 10.18280/ijcmem.110402 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110402 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110401 In recent years, machine learning, especially deep neural networks, has made substantial progress, consistently surpassing conventional time-series forecasting methods across various domains. This paper introduces a novel hybrid approach that combines the Lorenz system and the echo state network (ESN) to tackle and reduce the "butterfly effect" in chaos forecasting. The core contribution lies in harnessing the Lorenz system's unique properties, where initially converging trajectories gradually diverge, to train the ESN—a neural network celebrated for its non-linear computational capabilities, echo state property, and input forgetting capability. The primary aim is to establish a more robust and precise framework for predicting chaotic systems, given their sensitivity to initial conditions. This research endeavors to provide a versatile tool with wide-ranging applications, particularly in areas like stock price prediction, where accurately forecasting chaotic behavior holds paramount importance. The Lorenz system initiates with nearly identical initial states, differing by a mere 10-3 in the x-coordinate at t=0. Initially, these trajectories seem to overlap, but after t=1000, they significantly diverge. In this proposed approach, data from t=0 to t=1000 serves as the training input for the ESN. Once the training phase concludes, the ESN's formidable non-linear computational capabilities, echo state property, and input forgetting capability render it exceptionally well-suited for stepwise predictions and tasks sensitive to initial conditions. The simulation results demonstrate that over the subsequent 360 prediction steps conducted by the ESN, the "butterfly effect" stemming from the slightly varying initial states provided to the Lorenz System is effectively minimized. Notably, the simulation results underscore the superior performance of our hybrid approach, revealing a minimal root mean square error (RMSE) of less than 1.0. In contrast, a prior study introduced the MrESN (Multiple Reservoir Echo State Network) approach, which is a specific type of Echo State Network (ESN) used for forecasting multivariate chaotic time series. It employs multiple internal reservoirs within the network architecture to handle the complex dynamics of chaotic data but achieved lower accuracy with a larger RMSE of 43.70. Another preceding algorithm, BFA-DRESN, aimed at enhancing forecasting accuracy but yielded an RMSE value of 18.83. This research advances ESN-based predictability, offering a promising solution for addressing the challenges posed by chaos. 12-29-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">In recent years, machine learning, especially deep neural networks, has made substantial progress, consistently surpassing conventional time-series forecasting methods across various domains. This paper introduces a novel hybrid approach that combines the Lorenz system and the echo state network (ESN) to tackle and reduce the "butterfly effect" in chaos forecasting. The core contribution lies in harnessing the Lorenz system's unique properties, where initially converging trajectories gradually diverge, to train the ESN—a neural network celebrated for its non-linear computational capabilities, echo state property, and input forgetting capability. The primary aim is to establish a more robust and precise framework for predicting chaotic systems, given their sensitivity to initial conditions. This research endeavors to provide a versatile tool with wide-ranging applications, particularly in areas like stock price prediction, where accurately forecasting chaotic behavior holds paramount importance. The Lorenz system initiates with nearly identical initial states, differing by a mere 10</span>^{<span style="font-family: Times New Roman, serif">-3</span>}<span style="font-family: Times New Roman, serif"> in the x-coordinate at t=0. Initially, these trajectories seem to overlap, but after t=1000, they significantly diverge. In this proposed approach, data from t=0 to t=1000 serves as the training input for the ESN. Once the training phase concludes, the ESN's formidable non-linear computational capabilities, echo state property, and input forgetting capability render it exceptionally well-suited for stepwise predictions and tasks sensitive to initial conditions. The simulation results demonstrate that over the subsequent 360 prediction steps conducted by the ESN, the "butterfly effect" stemming from the slightly varying initial states provided to the Lorenz System is effectively minimized. Notably, the simulation results underscore the superior performance of our hybrid approach, revealing a minimal root mean square error (RMSE) of less than 1.0. In contrast, a prior study introduced the MrESN (Multiple Reservoir Echo State Network) approach, which is a specific type of Echo State Network (ESN) used for forecasting multivariate chaotic time series. It employs multiple internal reservoirs within the network architecture to handle the complex dynamics of chaotic data but achieved lower accuracy with a larger RMSE of 43.70. Another preceding algorithm, BFA-DRESN, aimed at enhancing forecasting accuracy but yielded an RMSE value of 18.83. This research advances ESN-based predictability, offering a promising solution for addressing the challenges posed by chaos.</span></p> ]]> Minimizing Chaos in Echo State Networks: A Hybrid Approach Using the Lorenz System soukaina seddik hayat routaib anass elhaddadi doi: 10.18280/ijcmem.110401 International Journal of Computational Methods and Experimental Measurements 12-29-2023 International Journal of Computational Methods and Experimental Measurements 12-29-2023 2023 11 4 Article 193 10.18280/ijcmem.110401 https://www.acadlore.com/article/IJCMEM/2023_11_4/ijcmem.110401 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110308 The integration of diesel and biodiesel, particularly biodiesel derived from water hyacinth, as a combined fuel source has recently emerged as a promising area of study, with a particular focus on the effects of nanoparticle additives. Notably, the reduction of emissions achieved by introducing iron oxide nanoparticles (Fe3O4) to biodiesel has been substantiated. However, the potential impact of blending nanoparticles with the diesel and biodiesel mix on the performance characteristics of a diesel engine has yet to be sufficiently explored. This research undertook performance and emission assessments employing diverse fuel samples in a single-cylinder diesel engine. The thermal brake efficiency metrics for the 50 ppm and 100 ppm iron oxide nanoparticle blends surpassed those of the D80B20 and D60B40 biofuel blends, exhibiting increases of 3.5% and 4.85% for D80B20N50 and D80B20N100, and 6.2% and 7.4% for D80B20N50 and D80B20N100, respectively, in comparison to neat diesel. The carbon monoxide emission levels of the biofuel blends with iron oxide were less than that of neat diesel, with the most significant reduction detected in the D60B40N100 blend. Furthermore, the nitrogen oxide emissions for all nanoparticle blends were lower than those for neat diesel, attributable to a shortened ignition delay and minimized fuel usage during combustion, subsequently leading to a reduction in nitrogen oxide emissions. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The integration of diesel and biodiesel, particularly biodiesel derived from water hyacinth, as a combined fuel source has recently emerged as a promising area of study, with a particular focus on the effects of nanoparticle additives. Notably, the reduction of emissions achieved by introducing iron oxide nanoparticles (Fe</span>_{<span style="font-family: Times New Roman, serif">3</span>}<span style="font-family: Times New Roman, serif">O</span>_{<span style="font-family: Times New Roman, serif">4</span>}<span style="font-family: Times New Roman, serif">) to biodiesel has been substantiated. However, the potential impact of blending nanoparticles with the diesel and biodiesel mix on the performance characteristics of a diesel engine has yet to be sufficiently explored. This research undertook performance and emission assessments employing diverse fuel samples in a single-cylinder diesel engine. The thermal brake efficiency metrics for the 50 ppm and 100 ppm iron oxide nanoparticle blends surpassed those of the D80B20 and D60B40 biofuel blends, exhibiting increases of 3.5% and 4.85% for D80B20N50 and D80B20N100, and 6.2% and 7.4% for D80B20N50 and D80B20N100, respectively, in comparison to neat diesel. The carbon monoxide emission levels of the biofuel blends with iron oxide were less than that of neat diesel, with the most significant reduction detected in the D60B40N100 blend. Furthermore, the nitrogen oxide emissions for all nanoparticle blends were lower than those for neat diesel, attributable to a shortened ignition delay and minimized fuel usage during combustion, subsequently leading to a reduction in nitrogen oxide emissions.</span></p> ]]> Impact of Iron Oxide Nanoparticles Additives in Water Hyacinth/Diesel Biofuel Mixture on CI Engine Performance and Emissions ahmed fadhil alaa dhari jawad al-bayati hasanain a. abdul wahhab doi: 10.18280/ijcmem.110308 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 187 10.18280/ijcmem.110308 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110308 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110307 This study explores the performance of the Photovoltaic/Thermal system using nanofluid with a novel collector design. Experiments were carried out on the University of Technology- Iraq campus. An experiment was carried out using two photovoltaic modules, one connected to 120 protrusions arranged eight columns by 15 rows (for comparison) and the other not. Nanofluid was used to cool solar panels with flow rates of 1.5 and 3.5 l/min. The nanofluid contains nano-Al2O3 at 1%, 2%, and 3% concentrations in water. As the flow rate of water used as a cooling fluid increased, the surface temperature of the cell decreased. The cell temperature is reduced by 22.3% when Al2O3/water is added at a volumetric concentration of 3%. An increase in the electrical and thermal efficiency of PV/T systems was also recorded by 12% and 18.4%, respectively, at a concentration of 3%. 09-25-2023 <![CDATA[ <p>This study explores the performance of the Photovoltaic/Thermal system using nanofluid with a novel collector design. Experiments were carried out on the University of Technology- Iraq campus. An experiment was carried out using two photovoltaic modules, one connected to 120 protrusions arranged eight columns by 15 rows (for comparison) and the other not. Nanofluid was used to cool solar panels with flow rates of 1.5 and 3.5 l/min. The nanofluid contains nano-Al2O3 at 1%, 2%, and 3% concentrations in water. As the flow rate of water used as a cooling fluid increased, the surface temperature of the cell decreased. The cell temperature is reduced by 22.3% when Al2O3/water is added at a volumetric concentration of 3%. An increase in the electrical and thermal efficiency of PV/T systems was also recorded by 12% and 18.4%, respectively, at a concentration of 3%. </p> ]]> Enhancement of PV/T Solar Collector Efficiency Using Alumina Nanoparticles Additives basam a. shallal engin gedik hasanain a. abdul wahhab louay abd al-azez mahdi miqdam t. chaichan doi: 10.18280/ijcmem.110307 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 181 10.18280/ijcmem.110307 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110307 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110306 Passive design solutions play a pivotal role in fostering sustainable practices within traditional architecture, as they empower historical urban designs to harmoniously engage with their surroundings and weather conditions, particularly in hot regions such as the United Arab Emirates. This research followed a qualitative approach to propose modifications for the thermal conditions and comfort in the modern contemporary urban districts based on the positive strategies from old traditional ones in a Hot-Arid Climate - Ajman-United Arab Emirates (UAE) as a case study using ENVI-met software-microscale three-dimensional software model for simulating complex urban environments. Moreover, this study made an evaluation and comparison of the outdoor air temperature and thermal comfort between the traditional and modern urban districts to highlight the passive design solutions that increase the thermal effectiveness in the traditional urban fabrics, as some of these passive design solutions can be used to modify the thermal conditions in the modern ones. Additionally, the research output revealed that the traditional urban design has valuable, sustainable strategies, as there was a decrease in the maximum reading for the air temperature for the traditional Ajman heritage district compared to the modern district on the 21st of August - as a reference day- and that improved the thermal comfort in the outdoor open spaces too. In conclusion, the study results confirmed that the thermal conditions in the existing modern districts could be improved using passive design solutions such as shading devices and greenery. Finally, this research is expected to be a phase amongst different phases that can benefit urban designers and architects to adopt strategies from traditional and vernacular urban projects and merge them with contemporary modern urban design. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">Passive design solutions play a pivotal role in fostering sustainable practices within traditional architecture, as they empower historical urban designs to harmoniously engage with their surroundings and weather conditions, particularly in hot regions such as the United Arab Emirates. This research followed a qualitative approach to propose modifications for the thermal conditions and comfort in the modern contemporary urban districts based on the positive strategies from old traditional ones in a Hot-Arid Climate - Ajman-United Arab Emirates (UAE) as a case study using ENVI-met software-microscale three-dimensional software model for simulating complex urban environments. Moreover, this study made an evaluation and comparison of the outdoor air temperature and thermal comfort between the traditional and modern urban districts to highlight the passive design solutions that increase the thermal effectiveness in the traditional urban fabrics, as some of these passive design solutions can be used to modify the thermal conditions in the modern ones. Additionally, the research output revealed that the traditional urban design has valuable, sustainable strategies, as there was a decrease in the maximum reading for the air temperature for the traditional Ajman heritage district compared to the modern district on the 21</span>^{<span style="font-family: Times New Roman, serif">st</span>}<span style="font-family: Times New Roman, serif"> of August - as a reference day- and that improved the thermal comfort in the outdoor open spaces too. In conclusion, the study results confirmed that the thermal conditions in the existing modern districts could be improved using passive design solutions such as shading devices and greenery. Finally, this research is expected to be a phase amongst different phases that can benefit urban designers and architects to adopt strategies from traditional and vernacular urban projects and merge them with contemporary modern urban design.</span></p> ]]> Comparative Analysis of Thermal Conditions and Comfort Between Modern and Traditional Districts in Hot-Arid Climate: Case Study in Ajman-UAE muna salameh basim touqan doi: 10.18280/ijcmem.110306 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 169 10.18280/ijcmem.110306 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110306 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110305 Using an entropy generation analysis, heat exchangers can be designed with optimal efficiency. This study delves into the irreversibility of forced convection heat transfer and friction flow around a horizontal cylinder, revealing that pressure drops induce entropy generation that varies in accordance with Reynolds numbers. The investigation encompasses four groups of ReD, covering ranges of 0.4DDDDD, the irreversibility distribution ratio (∅), the optimal Reynolds number (ReD,opt), and the Bejan number (Be), particularly where entropy generation has a minimal effect. Additionally, it seeks to determine the relationship between the duty parameter and ReD,opt across all ReD ranges. The findings highlight the optimum design point for forced convection around a horizontal cylinder. At this point, the entropy generation number reaches its minimum value when Ns=1 and the ratio ReD/ReD,opt=1, marking the optimal point for irreversibility or entropy generation. At this juncture, the irreversibility distribution ratio ∅ equals 0.5, and the optimal Bejan number stands at 0.667. 09-25-2023 <![CDATA[ <p><span style="font-family: Times, serif">Using an entropy generation analysis, heat exchangers can be designed with optimal efficiency. This study delves into the irreversibility of forced convection heat transfer and friction flow around a horizontal cylinder, revealing that pressure drops induce entropy generation that varies in accordance with Reynolds numbers. The investigation encompasses four groups of Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">, covering ranges of 0.4<Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif"><4, 4<Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif"><40, 40<Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif"><4000, and 4000<Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif"><40000. The study aims to elucidate the relationship between the entropy generation number (Ns), Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">, the irreversibility distribution ratio (</span><span style="font-family: Cambria Math, serif">∅</span><span style="font-family: Times, serif">), the optimal Reynolds number (Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">,opt), and the Bejan number (Be), particularly where entropy generation has a minimal effect. Additionally, it seeks to determine the relationship between the duty parameter and Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">,opt across all Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif"> ranges. The findings highlight the optimum design point for forced convection around a horizontal cylinder. At this point, the entropy generation number reaches its minimum value when Ns=1 and the ratio Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">/Re</span>_{<span style="font-family: Times, serif">D</span>}<span style="font-family: Times, serif">,opt=1, marking the optimal point for irreversibility or entropy generation. At this juncture, the irreversibility distribution ratio </span><span style="font-family: Cambria Math, serif">∅</span><span style="font-family: Times, serif"> equals 0.5, and the optimal Bejan number stands at 0.667.</span></p> ]]> Theoretical Entropy Generation Analysis for Forced Convection Flow Around a Horizontal Cylinder louay a. mahdi muna k. j. al-naamee ahmed q. salam salman h. omran hind a. al-salihi marwa k. abood hasanain a. abdul wahhab doi: 10.18280/ijcmem.110305 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 163 10.18280/ijcmem.110305 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110305 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110304 The continual pursuit of fuel efficiency, cost-effectiveness, and desirable physical and mechanical properties of materials has steered researchers towards the latest generation of aluminum matrix composites for automotive and aerospace applications. In this context, the present study investigates the microhardness behavior of Al6061/TiC composites produced by friction stir processing. The morphological characteristics of the produced surface composites were analyzed using optical microscopy and Scanning Electron Microscopy (SEM). SEM micrographs confirmed the presence of TiC particles and their uniform distribution within the aluminum matrix. The mechanical properties of the composites were explored using a microhardness tester, revealing a distinctive feature of the Al6061/TiC composites - a 35% increase in microhardness value compared to the base Al6061 alloy. This improvement in microhardness can be attributed to enhanced interfacial bonding, obstructions in dislocation movement, and grain refinement, all contributing to Hall-Petch strengthening. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The continual pursuit of fuel efficiency, cost-effectiveness, and desirable physical and mechanical properties of materials has steered researchers towards the latest generation of aluminum matrix composites for automotive and aerospace applications. In this context, the present study investigates the microhardness behavior of Al6061/TiC composites produced by friction stir processing. The morphological characteristics of the produced surface composites were analyzed using optical microscopy and Scanning Electron Microscopy (SEM). SEM micrographs confirmed the presence of TiC particles and their uniform distribution within the aluminum matrix. The mechanical properties of the composites were explored using a microhardness tester, revealing a distinctive feature of the Al6061/TiC composites - a 35% increase in microhardness value compared to the base Al6061 alloy. This improvement in microhardness can be attributed to enhanced interfacial bonding, obstructions in dislocation movement, and grain refinement, all contributing to Hall-Petch strengthening.</span></p> ]]> Investigating the Microhardness Behavior of Al6061/TiC Surface Composites Produced by Friction Stir Processing mohammad azad alam haji hamdan ya nur alya qistina mohammad azeem mazli mustapha mohammad yusuf faisal masood rehan khan tauseef ahmad doi: 10.18280/ijcmem.110304 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 157 10.18280/ijcmem.110304 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110304 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110303 The study aimed to determine the levels of heavy metals in some selected plant samples near the Wadafiea Dumpsite in Khartoum North, Sudan, and compare the variations between dry and rainy seasons. Except for Sudanese sorghum, Conocarpus lancifolius, and Leptadenia arborea, zinc contents in all plant samples during the dry season were higher than WHO/FAO guideline value (5mg/kg). In the rainy season, Cd concentrations were generally lower than in the dry season due to rainfall dilution. According to the findings, an open landfill of solid waste could have a severe impact on the quality of plants in the research area and surrounding farms, perhaps causing future concerns for human health and the environment due to pollution. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">The study aimed to determine the levels of heavy metals in some selected plant samples near the Wadafiea Dumpsite in Khartoum North, Sudan, and compare the variations between dry and rainy seasons. Except for </span><em><span style="font-family: Times New Roman, serif">Sudanese sorghum</span></em><span style="font-family: Times New Roman, serif">, </span><em><span style="font-family: Times New Roman, serif">Conocarpus lancifolius</span></em><span style="font-family: Times New Roman, serif">, and </span><em><span style="font-family: Times New Roman, serif">Leptadenia arborea</span></em><span style="font-family: Times New Roman, serif">, zinc contents in all plant samples during the dry season were higher than WHO/FAO</span><span style="color: black"> </span><span style="font-family: Times, serif">guideline value </span><span style="font-family: Times New Roman, serif">(5mg/kg). In the rainy season, Cd concentrations were generally lower than in the dry season due to rainfall dilution. According to the findings, an open landfill of solid waste could have a severe impact on the quality of plants in the research area and surrounding farms, perhaps causing future concerns for human health and the environment due to pollution.</span></p> ]]> Detection of Heavy Metals Concentrations in Agriculture Plants Near Landfills: Case Study in Wadafiea, Sudan omer a. e. abbass abdelelah m. elhassan abdelgadir e. abdelgadir doi: 10.18280/ijcmem.110303 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 149 10.18280/ijcmem.110303 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110303 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110302 CVBEM is a numerical method of solving boundary value problems that satisfy Laplace's Equation in two dimensions. Three key parameters that impact the computational error and functionality of CVBEM are the basis function, the positions of the modeling nodes, and the coefficient determination methodology. To demonstrate the importance of these parameters, a case study of 2D ideal fluid flow into a 90-degree bend and over a semicircular hump was conducted comparing models using original CVBEM, complex log, complex pole, and digamma function variants basis functions, using two different NPAs, NPA1 and NPA2, and using collocation and least squares methods to determine coefficients. Results indicate that the combination of the original CVBEM basis function, NPA2, and least squares results in an approximation with the least computational error. Moreover, least squares appear to enable stability in both NPAs regarding reduction of computational error due to taking advantage of all boundary data and more stable condition number growth. By exploring the interaction of the three main CVBEM parameters, this paper clarifies the unique impact they have on the modelling process and explicitly identifies a fourth parameter, collocation point placement, as being impactful on computational error. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">CVBEM is a numerical method of solving boundary value problems that satisfy Laplace's Equation in two dimensions. Three key parameters that impact the computational error and functionality of CVBEM are the basis function, the positions of the modeling nodes, and the coefficient determination methodology. To demonstrate the importance of these parameters, a case study of 2D ideal fluid flow into a 90-degree bend and over a semicircular hump was conducted comparing models using original CVBEM, complex log, complex pole, and digamma function variants basis functions, using two different NPAs, NPA1 and NPA2, and using collocation and least squares methods to determine coefficients. Results indicate that the combination of the original CVBEM basis function, NPA2, and least squares results in an approximation with the least computational error. Moreover, least squares appear to enable stability in both NPAs regarding reduction of computational error due to taking advantage of all boundary data and more stable condition number growth.</span><span> </span>By exploring the interaction of the three main CVBEM parameters, this paper clarifies the unique impact they have on the modelling process and explicitly identifies a fourth parameter, collocation point placement, as being impactful on computational error.</p> ]]> Comparison of Current Complex Variable Boundary Element Method (CVBEM) Capabilities in Basis Functions, Node Positioning Algorithms (NPAs), and Coefficient Determination Methods saleem a. ali theodore v. hromadka doi: 10.18280/ijcmem.110302 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 143 10.18280/ijcmem.110302 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110302 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110301 In the context of environmental monitoring studies, the complex dynamics of environmental systems, constrained by the distribution, intensity and interaction of multiple sources, limits the ability to detect pollution phenomena and to identify their sources. The deployment of multidisciplinary, multilevel and multi-factorial strategies supports the identification of the links between the pollutants’ sources and targets. Our new biomonitoring strategy, based on the integration of remote (satellite) and proximal (drone) sensing monitoring data with field data (bio/chemical analyses) and focused on the use of cyanobacteria as bioindicators of pollution, was implemented and was validated through its application on a test-bed area, i.e., Lake Avernus (Campania Region, Southern Italy). A long-term analysis of multispectral remote sensing observations centred on the Lake Avernus area highlighted the periodicity and seasonality of cyanobacterial bloom events over the time interval 2019-2021. However, a sudden change of characteristics, observable through remotely sensed data, was evidenced during the first and major lockdown related to the COVID-19 pandemics, in year 2020. This sudden change depended on the drastic modification of human habits and a reduction in pollutant emissions, as widely reported by the scientific literature. During the same lockdown period, the opportunity to collect samples in the field allowed to identify an unusual progression of Microcystis' bloom, whose dynamics is triggered by the existing anthropogenic sources and the evolution of environmental parameters, that can stimulate the blooming events. This work shows and demonstrates how pollution attribution can be achieved using remote sensing of cyanobacteria, which are excellent bioindicators due to their sensitivity to multiple stressors and rapid response to habitat changes throughout the event. 09-25-2023 <![CDATA[ <p><span style="font-family: Times New Roman, serif">In the context of environmental monitoring studies, the complex dynamics of environmental systems, constrained by the distribution, intensity and interaction of multiple sources, limits the ability to detect pollution phenomena and to identify their sources. The deployment of multidisciplinary, multilevel and multi-factorial strategies supports the identification of the links between the pollutants’ sources and targets. Our new biomonitoring strategy, based on the integration of remote (satellite) and proximal (drone) sensing monitoring data with field data (bio/chemical analyses) and focused on the use of cyanobacteria as bioindicators of pollution, was implemented and was validated through its application on a test-bed area, i.e., Lake Avernus (Campania Region, Southern Italy). A long-term analysis of multispectral remote sensing observations centred on the Lake Avernus area highlighted the periodicity and seasonality of cyanobacterial bloom events over the time interval 2019-2021. However, a sudden change of characteristics, observable through remotely sensed data, was evidenced during the first and major lockdown related to the COVID-19 pandemics, in year 2020. This sudden change depended on the drastic modification of human habits and a reduction in pollutant emissions, as widely reported by the scientific literature. During the same lockdown period, the opportunity to collect samples in the field allowed to identify an unusual progression of </span><em><span style="font-family: Times New Roman, serif">Microcystis'</span></em><span style="font-family: Times New Roman, serif"> bloom, whose dynamics is triggered by the existing anthropogenic sources and the evolution of environmental parameters, that can stimulate the blooming events. This work shows and demonstrates how pollution attribution can be achieved using remote sensing of cyanobacteria, which are excellent bioindicators due to their sensitivity to multiple stressors and rapid response to habitat changes throughout the event.</span></p> ]]> Cyanobacterial Biomonitoring in Lake Avernus During the COVID-19 Pandemic: Integrating Remote Sensing and Field Data for Pollution Source Detection massimiliano lega gabriele medio theodore endreny marco casazza germana esposito valeria costantino roberta teta doi: 10.18280/ijcmem.110301 International Journal of Computational Methods and Experimental Measurements 09-25-2023 International Journal of Computational Methods and Experimental Measurements 09-25-2023 2023 11 3 Article 135 10.18280/ijcmem.110301 https://www.acadlore.com/article/IJCMEM/2023_11_3/ijcmem.110301 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110207 Reliability analysis aims to assess the dependability and performance of a system over time, considering factors such as device failures, communication issues, and data integrity. By integrating taxonomy and reliability analysis, researchers can systematically analyze and enhance the reliability of IoT systems by addressing specific components and categories identified in the taxonomy. IoT based on its reliable applications is classified among various categories such as smart home devices, smart watches, electric vehicles with IoT capabilities, industrial, healthcare, agriculture, soil monitoring sensors, smart city infrastructure, environmental monitoring devices, and smart energy management devices. The need for a consistent taxonomy was one of the problems recognized and examined in this paper even though IoT management technology is developing. To examine the reliability analysis of IoT systems, we created a brand-new taxonomy for IoT gadgets that places a strong focus on administration. We have released a completely new IoT reliability RBD model analysis at different gateways and Round-Trip Time is to be analyzed. It features an aircraft for dependability. Our goal is to help administrators of networks, as well as designers, put processes in place that will analyze and enhance the reliability of IoT systems. To implement techniques to increase the IoT system's reliability, we may utilize the management capabilities to keep an eye on the devices. ChatGPT can act as the conversational interface for ISABELA. By integrating ChatGPT with ISABELA's functionality, users can have natural language conversations with ISABELA, making the interaction more intuitive and user-friendly. A use case study of ISABELA has enhanced the position of the CHATGPT system in the IoT system which increase the efficiency and reliability of IoT designs and networks. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Reliability analysis aims to assess the dependability and performance of a system over time, considering factors such as device failures, communication issues, and data integrity. By integrating taxonomy and reliability analysis, researchers can systematically analyze and enhance the reliability of IoT systems by addressing specific components and categories identified in the taxonomy. IoT based on its reliable applications is classified among various categories such as smart home devices, smart watches, electric vehicles with IoT capabilities, industrial, healthcare, agriculture, soil monitoring sensors, smart city infrastructure, environmental monitoring devices, and smart energy management devices. The need for a consistent taxonomy was one of the problems recognized and examined in this paper even though IoT management technology is developing. To examine the reliability analysis of IoT systems, we created a brand-new taxonomy for IoT gadgets that places a strong focus on administration. We have released a completely new IoT reliability RBD model analysis at different gateways and Round-Trip Time is to be analyzed. It features an aircraft for dependability. Our goal is to help administrators of networks, as well as designers, put processes in place that will analyze and enhance the reliability of IoT systems. To implement techniques to increase the IoT system's reliability, we may utilize the management capabilities to keep an eye on the devices. ChatGPT can act as the conversational interface for ISABELA. By integrating ChatGPT with ISABELA's functionality, users can have natural language conversations with ISABELA, making the interaction more intuitive and user-friendly. A use case study of ISABELA has enhanced the position of the CHATGPT system in the IoT system which increase the efficiency and reliability of IoT designs and networks.</span></p> ]]> Parametric Evaluation Techniques for Reliability of Internet of Things (IoT) khushwant singh yudhvir singh dheerdhwaj barak mohit yadav ercan özen doi: 10.18280/ijcmem.110207 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 123 10.18280/ijcmem.110207 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110207 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110206 In recent times, the construction industry has been recognized as a critical sector in achieving the Sustainable Development Goals. However, construction activities and infrastructure have both beneficial and non-beneficial impacts, making infrastructure design the focus of current research in finding the best way to meet society's demands for sustainability. Although methods for economic, environmental, and social life cycle assessments of infrastructures are well-known, the challenge lies in combining these dimensions into a comprehensive indicator that aids decision-making. This study uses three decision-making techniques, namely TOPSIS, COPRAS, and VIKOR, to evaluate five different design alternatives for a concrete bridge exposed to a coastal environment. To enhance the consistency of the multi-criteria decision-making process, a DEMATEL-based approach is applied. The study's results demonstrate unanimously that concrete containing even small amounts of silica fume performs better over its life cycle than other solutions typically considered to increase durability, such as reducing the water/cement ratio or increasing concrete cover. <![CDATA[ <p><span style="font-family: Times New Roman, serif">In recent times, the construction industry has been recognized as a critical sector in achieving the Sustainable Development Goals. However, construction activities and infrastructure have both beneficial and non-beneficial impacts, making infrastructure design the focus of current research in finding the best way to meet society's demands for sustainability. Although methods for economic, environmental, and social life cycle assessments of infrastructures are well-known, the challenge lies in combining these dimensions into a comprehensive indicator that aids decision-making. This study uses three decision-making techniques, namely TOPSIS, COPRAS, and VIKOR, to evaluate five different design alternatives for a concrete bridge exposed to a coastal environment. To enhance the consistency of the multi-criteria decision-making process, a DEMATEL-based approach is applied. The study's results demonstrate unanimously that concrete containing even small amounts of silica fume performs better over its life cycle than other solutions typically considered to increase durability, such as reducing the water/cement ratio or increasing concrete cover.</span></p> ]]> Dematel-Based Completion Technique Applied for the Sustainability Assessment of Bridges Near Shore ignacio j. navarro josé v. marti víctor yepes doi: 10.18280/ijcmem.110206 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 115 10.18280/ijcmem.110206 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110206 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110205 The construction site is a complex and dynamic place. Workers are susceptible to certain risks due to the variability of their worksites, the tasks they perform, and the equipment they use. These aspects make the architecture, engineering, construction, and operation industry (AECO) have high accident rates. These typical processes are added to the growing use of new technologies in the workplace (e.g., drones, robots) that must coexist with human workers, not altering their routines and preserving a safe environment. A key aspect of occupational risk prevention (ORP) is worker training. Traditional training methods are not satisfactory. Given these deficiencies, virtual reality has shown advantages and benefits for training, allowing the development of immersive training experiences that promise to generate more meaningful learning for students. The construction sector needs to reactivate their construction sites after periods of confinement due to the direct implications on the progress of projects and, indeed, the industry's productivity (with the repercussions on costs, time and legal aspects). In this respect, training workers in covid protection measures and designing and analysing changing construction site scenarios to reduce the spread of viruses is crucial to ensure workers' health. This research shows the application and agile development of a training experience for social distancing at construction sites to prevent COVID-19 transmission, based on virtual reality and building information modelling and using serious games as a teaching strategy. Analyses are shown to exemplify the application and potential of the tools. <![CDATA[ <p><span style="font-family: Times, serif">The construction site is a complex and dynamic place. Workers are susceptible to certain risks due to the variability of their worksites, the tasks they perform, and the equipment they use. These aspects make the architecture, engineering, construction, and operation industry (AECO) have high accident rates. These typical processes are added to the growing use of new technologies in the workplace (e.g., drones, robots) that must coexist with human workers, not altering their routines and preserving a safe environment. A key aspect of occupational risk prevention (ORP) is worker training. Traditional training methods are not satisfactory. Given these deficiencies, virtual reality has shown advantages and benefits for training, allowing the development of immersive training experiences that promise to generate more meaningful learning for students. The construction sector needs to reactivate their construction sites after periods of confinement due to the direct implications on the progress of projects and, indeed, the industry's productivity (with the repercussions on costs, time and legal aspects). In this respect, training workers in covid protection measures and designing and analysing changing construction site scenarios to reduce the spread of viruses is crucial to ensure workers' health. This research shows the application and agile development of a training experience for social distancing at construction sites to prevent COVID-19 transmission, based on virtual reality and building information modelling and using serious games as a teaching strategy. Analyses are shown to exemplify the application and potential of the tools.</span></p> ]]> Virtual Reality for the Creation of Stories and Scenarios for Construction Safety: Social Distancing in the COVID-19 Pandemic Context felipe muñoz-la rivera javier mora-serrano eugenio oñate doi: 10.18280/ijcmem.110205 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 105 10.18280/ijcmem.110205 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110205 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110204 In this paper, we will present a numerical framework to simulate the weapon operation for air-to-air missiles (AAM) on the super manoeuvrable fighter aircraft (Flanker C). We focus on creating a flexible and robust framework to insert into any flight simulator for training pilots to operate the air-to-air missile system. In general, the framework contains four main parts: (1) virtual target; (2) avionics systems; (3) head-up display system; (4) missile flight dynamics. The results of both semi-active radar and infrared homing missiles show the flexibility and robustness of the proposed framework in simulating the weapon operation. <![CDATA[ <p><span style="font-family: Times New Roman, serif">In this paper, we will present a numerical framework to simulate the weapon operation for air-to-air missiles (AAM) on the super manoeuvrable fighter aircraft (Flanker C). We focus on creating a flexible and robust framework to insert into any flight simulator for training pilots to operate the air-to-air missile system. In general, the framework contains four main parts: (1) virtual target; (2) avionics systems; (3) head-up display system; (4) missile flight dynamics. The results of both semi-active radar and infrared homing missiles show the flexibility and robustness of the proposed framework in simulating the weapon operation.</span></p> ]]> The Mathematical Framework for Simulating an Air-To-Air Missile Operation on Fighter Aircraft son tung dang hai anh nguyen hai duong nguyen tran thi minh kieu doi: 10.18280/ijcmem.110204 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 97 10.18280/ijcmem.110204 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110204 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110203 A correct prediction of building cooling load is essential in building energy consumption in a hot and humid urban area. To this extent, the current study emphasizes a meticulous review of different convective heat transfer coefficient correlations including those developed considering neighbourhood microclimate effect, and the existing ones used in building energy simulation programs such as EnergyPlus, Environmental Systems Performance - Research (ESP-r), Integrated Environmental Solutions Ltd (IES), IDA, and TAS. Furthermore, rigorous quantitative assessment of associated convective thermal load from the windward, leeward, and roof surfaces under the case of microclimatic conditions is performed. The data used in the current assessment are computational fluid dynamics results, as a reference, from previously published data and actual weather data from the hot and humid climate. It is observed that very few convective heat transfer coefficient correlations show closer predicted thermal load (deviation less than 30%) with computational fluid dynamics results, and others exhibit a varying degree of prediction ability with over-predictions in general for the windward, leeward and roof surfaces. Current analysis suggests that further attention is required to increase the prediction ability of convective heat transfer coefficient correlations by developing a convective heat transfer coefficient model considering computational fluid dynamics analysis of the whole district, validating and modifying or redefining existing convective heat transfer coefficient correlations based on real field measurement data considering flow field around the building, and incorporation of urban morphology, vegetation, urban heat island, and urban pollution level in convective heat transfer coefficient correlations development. <![CDATA[ <p><span style="font-family: Times, serif">A correct prediction of building cooling load is essential in building energy consumption in a hot and humid urban area. To this extent, the current study emphasizes a meticulous review of different convective heat transfer coefficient correlations including those developed considering neighbourhood microclimate effect, and the existing ones used in building energy simulation programs such as EnergyPlus, Environmental Systems Performance - Research (ESP-r), Integrated Environmental Solutions Ltd (IES), IDA, and TAS. Furthermore, rigorous quantitative assessment of associated convective thermal load from the windward, leeward, and roof surfaces under the case of microclimatic conditions is performed. The data used in the current assessment are computational fluid dynamics results, as a reference, from previously published data and actual weather data from the hot and humid climate. It is observed that very few convective heat transfer coefficient correlations show closer predicted thermal load (deviation less than 30%) with computational fluid dynamics results, and others exhibit a varying degree of prediction ability with over-predictions in general for the windward, leeward and roof surfaces. Current analysis suggests that further attention is required to increase the prediction ability of convective heat transfer coefficient correlations by developing a convective heat transfer coefficient model considering computational fluid dynamics analysis of the whole district, validating and modifying or redefining existing convective heat transfer coefficient correlations based on real field measurement data considering flow field around the building, and incorporation of urban morphology, vegetation, urban heat island, and urban pollution level in convective heat transfer coefficient correlations development.</span></p> ]]> A Review on Prediction Uncertainty in Exterior Heat Transfer Coefficient-Based Building Thermal Load: A Case of Microclimate sambhaji t kadam ibrahim hassan liangzhu (leon) wang mohammad azizur rahman doi: 10.18280/ijcmem.110203 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 79 10.18280/ijcmem.110203 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110203 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110202 Gears are among the most widespread mechanical component. Thanks to new technologies, new production methods and new materials on the market, the use of this component is constantly increasing. This fact outlines the need to understand properly the functioning of such component into different load cases. Nowadays the trend of miniaturization is growing in the mechanical sector and gears that have reduced its size are already used in several fields. This fact brings the necessity to correct analyze and study material properties and the fatigue behavior of this mechanical component. Failures resulting from cyclic stress, thus due to fatigue, must be correctly analyzed. This important aspect reduces the life of a generic component by causing unexpected breaks. For this purpose, in the present manuscript, a combined approach of theoretical calculation and experimental analysis is presented, the aim was to investigate the fatigue comportment of a gear made by 39NiCrMo3 with a fine module equal to 2. Single Tooth Bending Fatigue (STBF) tests were realized with the support of a universal tensile testing machine. New grips have been developed for performing fatigue tests on the tensile test machine and, moreover, dimensions of the new grippers were chosen in order to exploit the Wildhaber W5 property. The fatigue limit was approximated thanks to two different statistic approaches, the classic and the shortest stair-case method proposed by Dixon. Both analyses allow to compute the fatigue limit by performing tests at different loads. The step load used in this research was set at . The Dixon approach allows to use few tests with respect to the classic method, reducing time and material needed for the analyses. Furthermore, by using the standard ISO 6336 it is possible to translate the applied forces into stress values. Afterward, results of the combined theoretical/experimental analyses were related to the one proposed by the ISO standard of the same steel constituent. <![CDATA[ <p><span style="font-family: Times, serif">Gears are among the most widespread mechanical component. Thanks to new technologies, new production methods and new materials on the market, the use of this component is constantly increasing. This fact outlines the need to understand properly the functioning of such component into different load cases. Nowadays the trend of miniaturization is growing in the mechanical sector and gears that have reduced its size are already used in several fields. This fact brings the necessity to correct analyze and study material properties and the fatigue behavior of this mechanical component. Failures resulting from cyclic stress, thus due to fatigue, must be correctly analyzed. This important aspect reduces the life of a generic component by causing unexpected breaks. For this purpose, in the present manuscript, a combined approach of theoretical calculation and experimental analysis is presented, the aim was to investigate the fatigue comportment of a gear made by 39NiCrMo3 with a fine module </span><span> </span>equal to 2. Single Tooth Bending Fatigue (STBF) tests were realized with the support of a universal tensile testing machine. New grips have been developed for performing fatigue tests on the tensile test machine and, moreover, dimensions of the new grippers were chosen in order to exploit the Wildhaber W5 property. The fatigue limit was approximated thanks to two different statistic approaches, the classic and the shortest stair-case method proposed by Dixon. Both analyses allow to compute the fatigue limit by performing tests at different loads. The step load used in this research was set at <span style="font-family: Times, serif">. The Dixon approach allows to use few tests with respect to the classic method, reducing time and material needed for the analyses. Furthermore, by using the standard ISO 6336 it is possible to translate the applied forces into stress values. Afterward, results of the combined theoretical/experimental analyses were related to the one proposed by the ISO standard of the same steel constituent.</span></p> ]]> Investigation of the Fatigue Strength Behaviour of a Fine 2 mm Module Gear franco concli lorenzo fraccaroli doi: 10.18280/ijcmem.110202 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 73 10.18280/ijcmem.110202 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110202 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110201 Aeration refers to the air entrapment in a second fluid. In mechanical transmissions (as gearboxes and turbines) it affects the reliability of the system by reducing its performance and leading to early failure of the components. Air bubbles decrease the effectiveness of the lubricant by directly impacting on its heat transfer capabilities. The analysis of aeration in gearboxes is traditionally based on experiments, which require niche equipment for its evaluation. The last decade has been characterized by huge improvements in the field of numerical calculus and computer technology. These led to the implementation of sophisticated virtual models capable of reproducing complex multiphase operating conditions. In the present work, Computational Fluid Dynamics (CFD) was exploited to study the effect of a new solver (implemented in the OpenFOAM® framework) that considers aeration. The solver was used for the simulation of a real gearbox in which aeration was observed. The results were analysed qualitatively in terms of amount of increase of the lubricant mixture volume, and quantitatively in terms of power dissipation estimation. The promising outcomes of this analysis suggests that this tool can be possibly exploited to have a deeper insight in the aeration phenomenon. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Aeration refers to the air entrapment in a second fluid. In mechanical transmissions (as gearboxes and turbines) it affects the reliability of the system by reducing its performance and leading to early failure of the components. Air bubbles decrease the effectiveness of the lubricant by directly impacting on its heat transfer capabilities. The analysis of aeration in gearboxes is traditionally based on experiments, which require niche equipment for its evaluation. The last decade has been characterized by huge improvements in the field of numerical calculus and computer technology. These led to the implementation of sophisticated virtual models capable of reproducing complex multiphase operating conditions. In the present work, Computational Fluid Dynamics (CFD) was exploited to study the effect of a new solver (implemented in the OpenFOAM® framework) that considers aeration. The solver was used for the simulation of a real gearbox in which aeration was observed. The results were analysed qualitatively in terms of amount of increase of the lubricant mixture volume, and quantitatively in terms of power dissipation estimation. The promising outcomes of this analysis suggests that this tool can be possibly exploited to have a deeper insight in the aeration phenomenon.</span></p> ]]> Implementation of a Numerical Model for the Prediction of Aeration in Mechanical Systems marco nicola mastrone franco concli doi: 10.18280/ijcmem.110201 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 2 Article 65 10.18280/ijcmem.110201 https://www.acadlore.com/article/IJCMEM/2023_11_2/ijcmem.110201 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110107 The construction industry is considered one of the most dangerous industries globally. The construction site is a complex environment where diverse teams of people interact with large machinery. In addition, the lack of safety culture on the job site and deficiencies in safety training increase these problems. Within the construction works, geotechnical drilling worksites involve high-powered machinery, and workers are exposed to different risks when using them. Despite these risks, safety training courses on these topics are not specialized. Most of the training courses are generic in occupational hazards, failing to address in detail the work dynamics and risks associated with geotechnical work, where heavy machinery is a fundamental factor. There is a lack of adequate learning content specific to drilling works, meaning the heavy machinery, how to use it and how to prevent accidents due to these drilling tasks are poorly understood. This research investigates the risks associated with geotechnical drilling work and explores the potential of virtual reality (VR) to simulate immersive work environments, focusing on interaction with drilling machinery. A geotechnical drilling machine modelled 3D and integrated into a realistic VR environment. The machinery motions and the different tasks of the work team were modelled. The simulation allows a worker to interact in a working environment, identify risks and prevent accidents, and, moreover, be trained in best practices for machinery usage, according to previous real-world experiences from senior workers. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The construction industry is considered one of the most dangerous industries globally. The construction site is a complex environment where diverse teams of people interact with large machinery. In addition, the lack of safety culture on the job site and deficiencies in safety training increase these problems. Within the construction works, geotechnical drilling worksites involve high-powered machinery, and workers are exposed to different risks when using them. Despite these risks, safety training courses on these topics are not specialized. Most of the training courses are generic in occupational hazards, failing to address in detail the work dynamics and risks associated with geotechnical work, where heavy machinery is a fundamental factor. There is a lack of adequate learning content specific to drilling works, meaning the heavy machinery, how to use it and how to prevent accidents due to these drilling tasks are poorly understood. This research investigates the risks associated with geotechnical drilling work and explores the potential of virtual reality (VR) to simulate immersive work environments, focusing on interaction with drilling machinery. A geotechnical drilling machine modelled 3D and integrated into a realistic VR environment. The machinery motions and the different tasks of the work team were modelled. The simulation allows a worker to interact in a working environment, identify risks and prevent accidents, and, moreover, be trained in best practices for machinery usage, according to previous real-world experiences from senior workers.</span></p> ]]> Virtual Reality Training for Occupational Risk Prevention: Application Case in Geotechnical Drilling Works a. fernández muñoz-la rivera j. mora-serrano doi: 10.18280/ijcmem.110107 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 55 10.18280/ijcmem.110107 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110107 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110106 Cultural heritage sites are exposed to a variety of risks, for instance, by robbery, vandalism, harming, terrorism, and cyber attacks, which might damage people and cultural heritage place.For this motive, it is necessary to plan appropriate countermeasures to prevent the above risks and to protect them using intrusion detection, access control, video surveillance, communication systems, cybersecurity devices and solutions, security personnel, and procedures properly mixed to attain an integrated system or solution.In this paper, a new security risk assessment method for cultural heritage sites (SRACHS) is presented, showing as a case study, without any loss of its wide pertinence, its application to a museum. Further, a proper genetic algorithms (GAs)-based methodology to optimize risk reduction countermeasures is presented.The proposed security risk assessment methodology allows for obtaining the correct amount of security defences (intrusion detection system, access control, video surveillance, communication devices, security personnel, etc.) that a desired cultural heritage place necessitates and the associated characteristics which depend on the probable targets that can be attacked.It also avoids of overestimating the risks as in the situation of planning unnecessary protective countermeasures that sometimes cannot be needed, thus reducing the connected extra expenses, as properly demonstrated by the GAs-based methodology to optimize risk reduction countermeasures proposed in this paper. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Cultural heritage sites are exposed to a variety of risks, for instance, by robbery, vandalism, harming, terrorism, and cyber attacks, which might damage people and cultural heritage place.</span></p><p><span style="font-family: Times New Roman, serif">For this motive, it is necessary to plan appropriate countermeasures to prevent the above risks and to protect them using intrusion detection, access control, video surveillance, communication systems, cybersecurity devices and solutions, security personnel, and procedures properly mixed to attain an integrated system or solution.</span></p><p><span style="font-family: Times New Roman, serif">In this paper, a new security risk assessment method for cultural heritage sites (SRACHS) is presented, showing as a case study, without any loss of its wide pertinence, its application to a museum. Further, a proper genetic algorithms (GAs)-based methodology to optimize risk reduction countermeasures is presented.</span></p><p><span style="font-family: Times New Roman, serif">The proposed security risk assessment methodology allows for obtaining the correct amount of security defences (intrusion detection system, access control, video surveillance, communication devices, security personnel, etc.) that a desired cultural heritage place necessitates and the associated characteristics which depend on the probable targets that can be attacked.</span></p><p><span style="font-family: Times New Roman, serif">It also avoids of overestimating the risks as in the situation of planning unnecessary protective countermeasures that sometimes cannot be needed, thus reducing the connected extra expenses, as properly demonstrated by the GAs-based methodology to optimize risk reduction countermeasures proposed in this paper.</span></p> ]]> New Security Risk Assessment and Genetic Algorithms Based Methods to Optimize Risk Reduction Countermeasures for Cultural Heritage Sites fabio garzia doi: 10.18280/ijcmem.110106 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 45 10.18280/ijcmem.110106 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110106 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110105 The Predicted Mean Vote (PMV) model for thermal comfort determination is unsuitable for use as a generalized index in tropical climates where the weather is hot and humid throughout the year. The current study is aimed to address the discrepancy in the thermal comfort models to estimate the thermal sensation in a tropical climate. Then, a case study was performed on a single-story office building in Malaysia, which has a typical tropical climate, to develop a new modified adaptive Predictive Mean Vote (maPMV) that suits the tropical climate. Experimental measurements were conducted with two groups of occupants. The adoptive mean vote showed that the participants were likely to feel comfortable when the indoor temperature was between 24°C and 26°C. The PMV model overestimated the thermal sensation in the room. Accordingly, a maPMV model was developed to mitigate the inaccuracy of the existing PMV model. The coefficients of the developed model were determined based on the adaptive approach using actual thermal sensation data obtained from a questionnaire survey of the occupants. The overall thermal comfort estimation could be improved using the developed model to reduce the cooling load and the building’s energy consumption in tropical areas. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The Predicted Mean Vote (PMV) model for thermal comfort determination is unsuitable for use as a generalized index in tropical climates where the weather is hot and humid throughout the year. The current study is aimed to address the discrepancy in the thermal comfort models to estimate the thermal sensation in a tropical climate. Then, a case study was performed on a single-story office building in Malaysia, which has a typical tropical climate, to develop a new modified adaptive Predictive Mean Vote (maPMV) that suits the tropical climate. Experimental measurements were conducted with two groups of occupants. The adoptive mean vote showed that the participants were likely to feel comfortable when the indoor temperature was between 24°C and 26°C. The PMV model overestimated the thermal sensation in the room. Accordingly, a maPMV model was developed to mitigate the inaccuracy of the existing PMV model. The coefficients of the developed model were determined based on the adaptive approach using actual thermal sensation data obtained from a questionnaire survey of the occupants. The overall thermal comfort estimation could be improved using the developed model to reduce the cooling load and the building’s energy consumption in tropical areas.</span></p> ]]> Experimental Assessment and Development of Thermal Comfort Model for Implication in Tropical Climate hussain h. al-kayiem mohammed n. mohammed koh kelly tri w. b. riyadi marwan effendy doi: 10.18280/ijcmem.110105 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 35 10.18280/ijcmem.110105 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110105 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110104 The capability of antivibration (AV) gloves to reduce the vibration’s transmissibility is not always proven, especially with percussive tools. Additionally, laboratory test results are sometimes dissimilar from the real field’s one. The present paper investigates the properties of three different types of gloves air bubbles, gel, neoprene - specifically designed for vibration reduction, and of an ordinary working leather glove, during their use with a light (3 kg) electric hammer, in a real field, while chiseling a limestone block.Outcomes reveal that AV gloves could provide benefits in reducing vibration when used with that type of tool, even though the protection is different to the one determined in laboratory test according to the ISO 10819 Standard.The statistical analysis does not reveal differences for the triaxial transmissibility in the AV gloves in the range (6.3-1250 Hz), showing an average overall reduction of 26%, calculated with the corrected method specified by the ISO 10819:2013 Standard. The leather glove provides a reduction of around 8%. Similarly, statistical differences are not found with reference to transmissibility through the three main axes for the same type of glove, both in air and neoprene gloves. On the contrary, gel and leather gloves differ in transmissibility along the axes, showing a better reduction on the x- and z-axes, respectively. The transmissibility estimated with the direct method shows an average decrement of around 10% when compared to that resulting from the corrected one. The air glove provides the best triaxial transmissibility reduction at middle frequencies (25-200 Hz), while at high frequencies (200-1250 Hz), the best reduction is provided by the neoprene glove. At the peak percussion frequency of 63 Hz, measured on this tool, all the AV gloves provide some vibration attenuation - an average of 27% - with no statistical differences, while leather gloves show a little transmissibility increment (1.02).Although the accelerometers used for the study are positioned as closely as possible, there are still differences between the acceleration measured on the bare-hand adaptor and the one directly on the handle, highlighting the importance of the corrected method application for better evaluating the gloves’ transmissibility. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The capability of antivibration (AV) gloves to reduce the vibration’s transmissibility is not always proven, especially with percussive tools. Additionally, laboratory test results are sometimes dissimilar from the real field’s one. The present paper investigates the properties of three different types of gloves air bubbles, gel, neoprene - specifically designed for vibration reduction, and of an ordinary working leather glove, during their use with a light (3 kg) electric hammer, in a real field, while chiseling a limestone block.</span></p><p><span style="font-family: Times New Roman, serif">Outcomes reveal that AV gloves could provide benefits in reducing vibration when used with that type of tool, even though the protection is different to the one determined in laboratory test according to the ISO 10819 Standard.</span></p><p><span style="font-family: Times New Roman, serif">The statistical analysis does not reveal differences for the triaxial transmissibility in the AV gloves in the range (6.3-1250 Hz), showing an average overall reduction of 26%, calculated with the corrected method specified by the ISO 10819:2013 Standard. The leather glove provides a reduction of around 8%. Similarly, statistical differences are not found with reference to transmissibility through the three main axes for the same type of glove, both in air and neoprene gloves. On the contrary, gel and leather gloves differ in transmissibility along the axes, showing a better reduction on the x- and z-axes, respectively. The transmissibility estimated with the direct method shows an average decrement of around 10% when compared to that resulting from the corrected one. The air glove provides the best triaxial transmissibility reduction at middle frequencies (25-200 Hz), while at high frequencies (200-1250 Hz), the best reduction is provided by the neoprene glove. At the peak percussion frequency of 63 Hz, measured on this tool, all the AV gloves provide some vibration attenuation - an average of 27% - with no statistical differences, while leather gloves show a little transmissibility increment (1.02).</span></p><p><span style="font-family: Times New Roman, serif">Although the accelerometers used for the study are positioned as closely as possible, there are still differences between the acceleration measured on the bare-hand adaptor and the one directly on the handle, highlighting the importance of the corrected method application for better evaluating the gloves’ transmissibility.</span></p> ]]> Effectiveness of Antivibration Gloves When Used with a Light Electric Hammer. Differences Among Different Methods of Measurements andrea antonucci gianluca coltrinari dario lippiello doi: 10.18280/ijcmem.110104 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 27 10.18280/ijcmem.110104 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110104 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110103 The present study pursues to determine the optimal operation range of a specific screen-based eye-tracker, the Tobii X2-30, regarding the variation of precision and accuracy in measures. Furthermore, a connection setup to operate a collaborative robot (cobot) Omron TM5-700 by means of this eye-tracker will be presented. The possibility to operate a collaborative robot by gaze can be used as a third arm, which allows human beings to do more sophisticated activities, as well as making the manipulation of dangerous or perilous substance easier and safer. When developing new technological tools, we have mainly two options. The first one consists on a specifically designed hardware. While in this option, the engineer has full control over the device and can fit it to the specific requirements; in general, it will be a time consuming and expensive development. A second drawback is the limited possibility of researchers from other countries to construct an exactly equal device and replicate the experiments. The second option consists on adopting an existing commercial hardware, which probably has not been designed for the specific application in mind. The main advantage is the easy adaptation of this solution by other researchers, who only need to purchase the same commercial device and follow the recommendations. However, the main drawback of this approach is that the developers must test the device and check that it can be used for the new application. The goal of this paper is to test a commercial device and provide usability recommendations for a new application such is the movement of a robotic arm using eye-tracking. This paper includes the results from three experiments, which assess the final conclusion on the best performance positioning of the user regarding the Tobii X2-30 eye-tracker, in x, y, and z coordinates. When it comes to its implementation with the cobot, the outcome of a practical demo and experimental setup is also presented. This last one consists of accuracy measurements, where the control of the position of the cobot is defined by means of gaze, which defines a set of points in (x,y) plane. Later on, the robot picks up an ink-pen and draws a graph in a piece of paper. This drawing involves connecting these pre-defined dots by straights lines. To this end, a set of figures (parallelogram, pentagon, etc.) have been acquired and compared with the desired printed images on the PC screen. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The present study pursues to determine the optimal operation range of a specific screen-based eye-tracker, the Tobii X2-30, regarding the variation of precision and accuracy in measures. Furthermore, a connection setup to operate a collaborative robot (cobot) Omron TM5-700 by means of this eye-tracker will be presented. The possibility to operate a collaborative robot by gaze can be used as a third arm, which allows human beings to do more sophisticated activities, as well as making the manipulation of dangerous or perilous substance easier and safer. When developing new technological tools, we have mainly two options. The first one consists on a specifically designed hardware. While in this option, the engineer has full control over the device and can fit it to the specific requirements; in general, it will be a time consuming and expensive development. A second drawback is the limited possibility of researchers from other countries to construct an exactly equal device and replicate the experiments. The second option consists on adopting an existing commercial hardware, which probably has not been designed for the specific application in mind. The main advantage is the easy adaptation of this solution by other researchers, who only need to purchase the same commercial device and follow the recommendations. However, the main drawback of this approach is that the developers must test the device and check that it can be used for the new application. The goal of this paper is to test a commercial device and provide usability recommendations for a new application such is the movement of a robotic arm using eye-tracking. This paper includes the results from three experiments, which assess the final conclusion on the best performance positioning of the user regarding the Tobii X2-30 eye-tracker, in </span><em><span style="font-family: Times New Roman, serif">x, y</span></em><span style="font-family: Times New Roman, serif">, and </span><em><span style="font-family: Times New Roman, serif">z </span></em><span style="font-family: Times New Roman, serif">coordinates. When it comes to its implementation with the cobot, the outcome of a practical demo and experimental setup is also presented. This last one consists of accuracy measurements, where the control of the position of the cobot is defined by means of gaze, which defines a set of points in (</span><em><span style="font-family: Times New Roman, serif">x</span></em><span style="font-family: Times New Roman, serif">,y) plane. Later on, the robot picks up an ink-pen and draws a graph in a piece of paper. This drawing involves connecting these pre-defined dots by straights lines. To this end, a set of figures (parallelogram, pentagon, etc.) have been acquired and compared with the desired printed images on the PC screen.</span></p> ]]> Eye-Tracking Calibration to Control a Cobot anna faura-pujol marcos faundez-zanuy aleix moral-viñals josep lópez-xarbau doi: 10.18280/ijcmem.110103 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 17 10.18280/ijcmem.110103 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110103 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110102 The sound produced when jets issued from a circular nozzle collide with a downstream ring coaxial with the jet is called a ring tone. The ring tone is investigated through experiments and direct sound computations. The inner diameters of the circular nozzle exit and the ring are both 30 mm. In the experiments, the frequency spectra of the ring tone are measured for various impingement lengths of 20–40 mm and jet velocities of 5–15 m/s. Measured data exhibit typical properties of self-sustained oscillations such as linear rise in peak frequency as the rise of the jet speed, multiple series of peaks, and mode jumps. In the computations, points discretely representing volumetric vortical regions are divided into locally connected groups of points that are separated from each other. This clustering enables the extraction of volumetric vortical regions in three-dimensional flow fields based on attributes defined on each point and tracking vortex structures selectively. By identifying strong vortex structures, the onset of self-sustained feedback oscillations in the ring tone is clarified from the view point of the throttling mechanism originally proposed for the hole tone, i.e., the coupling between the mass flow through the ring, vortex impingement, and global pressure fluctuation. <![CDATA[ <p><span style="font-family: Times New Roman, serif">The sound produced when jets issued from a circular nozzle collide with a downstream ring coaxial with the jet is called a ring tone. The ring tone is investigated through experiments and direct sound computations. The inner diameters of the circular nozzle exit and the ring are both 30 mm. In the experiments, the frequency spectra of the ring tone are measured for various impingement lengths of 20–40 mm and jet velocities of 5–15 m/s. Measured data exhibit typical properties of self-sustained oscillations such as linear rise in peak frequency as the rise of the jet speed, multiple series of peaks, and mode jumps. In the computations, points discretely representing volumetric vortical regions are divided into locally connected groups of points that are separated from each other. This clustering enables the extraction of volumetric vortical regions in three-dimensional flow fields based on attributes defined on each point and tracking vortex structures selectively. By identifying strong vortex structures, the onset of self-sustained feedback oscillations in the ring tone is clarified from the view point of the throttling mechanism originally proposed for the hole tone, i.e., the coupling between the mass flow through the ring, vortex impingement, and global pressure fluctuation.</span></p> ]]> Computational and Experimental Study on the Mechanism of Ring Tone kazuo matsuura koh mukai mikael andersen langthjem doi: 10.18280/ijcmem.110102 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 9 10.18280/ijcmem.110102 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110102 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110101 Additive manufacturing is a disruptive technology that, besides reducing material, resource, and tool consumption, allows us to produce products with complex geometries and design freedom. However, the investments required for its adoption are considerable, and companies still wonder if and when the introduction of additive manufacturing is convenient from an economic viewpoint. The aim of this paper is to estimate unit product costs in additive manufacturing environments and compare them with those resulting from traditional manufacturing. For a more complete evaluation, the geometric possibilities offered by additive manufacturing are taken into consideration too in the analyses. In particular, three different manufacturing environments are selected for the cost comparison: (1) traditional manufacturing, (2) additive manufacturing, and (3) additive manufacturing while utilizing the design optimization via finite element simulations. Cost models for the three environments are developed and applied to three components produced in different sectors and batches: an automotive gear, a bottle blowing mould, and a hip prosthesis. The results show that, from an economic viewpoint, additive manufacturing can be a competitive solution, but only as far as the product volume is limited and the geometry is simple. When these conditions are not met, additive manufacturing becomes an extremely slow and expensive solution, making traditional techniques more suitable and convenient, especially with numerous batches. <![CDATA[ <p><span style="font-family: Times New Roman, serif">Additive manufacturing is a disruptive technology that, besides reducing material, resource, and tool consumption, allows us to produce products with complex geometries and design freedom. However, the investments required for its adoption are considerable, and companies still wonder if and when the introduction of additive manufacturing is convenient from an economic viewpoint. The aim of this paper is to estimate unit product costs in additive manufacturing environments and compare them with those resulting from traditional manufacturing. For a more complete evaluation, the geometric possibilities offered by additive manufacturing are taken into consideration too in the analyses. In particular, three different manufacturing environments are selected for the cost comparison: (1) traditional manufacturing, (2) additive manufacturing, and (3) additive manufacturing while utilizing the design optimization via finite element simulations. Cost models for the three environments are developed and applied to three components produced in different sectors and batches: an automotive gear, a bottle blowing mould, and a hip prosthesis. The results show that, from an economic viewpoint, additive manufacturing can be a competitive solution, but only as far as the product volume is limited and the geometry is simple. When these conditions are not met, additive manufacturing becomes an extremely slow and expensive solution, making traditional techniques more suitable and convenient, especially with numerous batches.</span></p> ]]> Design for Additive Manufacturing: Cost Evaluations franco concli margherita molinaro doi: 10.18280/ijcmem.110101 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2023 11 1 Article 1 10.18280/ijcmem.110101 https://www.acadlore.com/article/IJCMEM/2023_11_1/ijcmem.110101 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-352-364 Particle size distribution is one of the most important physical properties of a particulate sample. Traditional particle-sizing methods to estimate a geometrical particle size distribution employ a sieve analysis (or gradation test), which entails filtering the particles through a series of sieves and measuring the weight remaining on each sieve to estimate the number-weighted particle size distribution. However, these two quantities have the same value only if particles are perfectly spherical and round. On the other hand, a particle sizer such as the Malvern particle size analyzer, which uses laser diagnostics to measure the particle sizes, can be a hefty investment. Alternatively, imaging techniques can be applied to estimate the size of these particles by scaling a reference dimension to the pixel size, which in turn is used to estimate the size of the visible particles. The focus of this work is to present a simple methodology using a DSLR camera and an illuminated LED panel to generate enough contrast. Using the camera and lens properties, the scale, or size, of any image can be obtained based on the mounting distance of the camera with respect to the target. An analysis tool was developed in MATLAB where the images are processed automatically based on the prescribed camera and lens properties embedded within the same image file and requiring the user to only input the mounting distance of the camera. So far, results show a positive agreement when comparing to measurements using ImageJ imaging tools and a sieve analysis. Future tests will analyze different particle sizes and types, as well as using a Malvern particle size analyzer to corroborate the results. <![CDATA[ <p>Particle size distribution is one of the most important physical properties of a particulate sample. Traditional particle-sizing methods to estimate a geometrical particle size distribution employ a sieve analysis (or gradation test), which entails filtering the particles through a series of sieves and measuring the weight remaining on each sieve to estimate the number-weighted particle size distribution. However, these two quantities have the same value only if particles are perfectly spherical and round. On the other hand, a particle sizer such as the Malvern particle size analyzer, which uses laser diagnostics to measure the particle sizes, can be a hefty investment. Alternatively, imaging techniques can be applied to estimate the size of these particles by scaling a reference dimension to the pixel size, which in turn is used to estimate the size of the visible particles. The focus of this work is to present a simple methodology using a DSLR camera and an illuminated LED panel to generate enough contrast. Using the camera and lens properties, the scale, or size, of any image can be obtained based on the mounting distance of the camera with respect to the target. An analysis tool was developed in MATLAB where the images are processed automatically based on the prescribed camera and lens properties embedded within the same image file and requiring the user to only input the mounting distance of the camera. So far, results show a positive agreement when comparing to measurements using ImageJ imaging tools and a sieve analysis. Future tests will analyze different particle sizes and types, as well as using a Malvern particle size analyzer to corroborate the results.</p> ]]> A Simple and Fast Matlab-Based Particle Size Distribution Analysis Tool jesus d. ortega irma r. vazquez peter vorobieff clifford k. ho doi: 10.2495/CMEM-V9-N4-352-364 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 352 10.2495/CMEM-V9-N4-352-364 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-352-364 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-339-351 Biofillers, lignocellulosic and cellulosic fillers have the potential to significantly improve the mechanical properties of polypropylene (PP) and reduce its carbon footprint by reducing the amount of petroleum-derived polymer used. In addition, the realization of fire retardancy of biofiller-filled PP composites is an important key topic to enhance their applications; ammonium polyphosphate (APP) is an effective fire retardant (FR). In this study, to ensure the reliability of biofiller- and FR-filled PP composites, the creep properties were investigated in terms of the filler and FR content and filler type. In particular, the influence of APP addition into polymer composites on the creep properties has not been studied thoroughly. Two biofillers, wood flour (WF) and cellulose filler (CeF), with similar particle sizes and aspect ratios were used in this study. The creep test was conducted at a temperature of 80℃ in an accelerated test. Furthermore, the creep strain curves were modelled by the Burgers model of the viscoelastic constitutive equation to analyse the creep deformation behaviour. The incorporation of biofillers into the PP matrix significantly decreased the creep strain and improved the creep-rupture life with increasing filler content. Moreover, the creep-rupture life was longer for WF-filled PP composites than for CeF-filled PP composites. On the other hand, we found that incorporation of FR increased the creep rate at steady state and decreased the creep-rupture life of biofiller-filled PP composites, although the instantaneous creep strain decreased. <![CDATA[ <p>Biofillers, lignocellulosic and cellulosic fillers have the potential to significantly improve the mechanical properties of polypropylene (PP) and reduce its carbon footprint by reducing the amount of petroleum-derived polymer used. In addition, the realization of fire retardancy of biofiller-filled PP composites is an important key topic to enhance their applications; ammonium polyphosphate (APP) is an effective fire retardant (FR). In this study, to ensure the reliability of biofiller- and FR-filled PP composites, the creep properties were investigated in terms of the filler and FR content and filler type. In particular, the influence of APP addition into polymer composites on the creep properties has not been studied thoroughly. Two biofillers, wood flour (WF) and cellulose filler (CeF), with similar particle sizes and aspect ratios were used in this study. The creep test was conducted at a temperature of 80℃ in an accelerated test. Furthermore, the creep strain curves were modelled by the Burgers model of the viscoelastic constitutive equation to analyse the creep deformation behaviour. The incorporation of biofillers into the PP matrix significantly decreased the creep strain and improved the creep-rupture life with increasing filler content. Moreover, the creep-rupture life was longer for WF-filled PP composites than for CeF-filled PP composites. On the other hand, we found that incorporation of FR increased the creep rate at steady state and decreased the creep-rupture life of biofiller-filled PP composites, although the instantaneous creep strain decreased.</p> ]]> Creep Properties of Biofiller- and Fire Retardant-Filled Polypropylene Composites koki matsumoto kenichi takemura hitoshi takagi tatsuya tanaka masahiro sasada doi: 10.2495/CMEM-V9-N4-339-351 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 339 10.2495/CMEM-V9-N4-339-351 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-339-351 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-327-338 Understanding the effects of blast generated by an accidental or a terroristic explosion nearby a critical structure is a main concern for the French Institute for Nuclear Safety (IRSN) and the French-German Research Institute of Saint Louis (ISL). Full-scale reactive phenomena are however seldomly compatible with long-term studies due to cost and regulation issues. Reduced scaled experimental work consequently represents an attractive alternative. Using small plastic explosive charges, blast effects in free-field or around various obstacles based on reference structures can be repeatedly examined, in order to provide the data necessary to develop simplified and numerical models. Following previous work on this topic by IRSN using a blast table and 42 g Hexomax® charges placed on its surface, ISL modified one existing blast pad to reproduce the same configuration at a double scale (333 g charges of Hexomax®). This study was conducted using a reference hemicylindrical obstacle, commonly encountered on industrial sites and also representative of certain transport containers. Numerous pressure sensors installed within the table or the pad thickness and on the surface of the hemicylinders provided the overpressure evolution for different values of the charge to obstacle distance. Explosive charges were ignited at distances up to 3.5 m/kg1/3 from the obstacle at ISL scale to extend the applicability domain of the model described in our previous document (Trélat et al. [18]) at a larger scale. The objective of this work is to assess not only blast effects on a potential target but also its capability to modify the blast propagation in its downstream space. <![CDATA[ <p>Understanding the effects of blast generated by an accidental or a terroristic explosion nearby a critical structure is a main concern for the French Institute for Nuclear Safety (IRSN) and the French-German Research Institute of Saint Louis (ISL). Full-scale reactive phenomena are however seldomly compatible with long-term studies due to cost and regulation issues. Reduced scaled experimental work consequently represents an attractive alternative. Using small plastic explosive charges, blast effects in free-field or around various obstacles based on reference structures can be repeatedly examined, in order to provide the data necessary to develop simplified and numerical models. Following previous work on this topic by IRSN using a blast table and 42 g Hexomax® charges placed on its surface, ISL modified one existing blast pad to reproduce the same configuration at a double scale (333 g charges of Hexomax®). This study was conducted using a reference hemicylindrical obstacle, commonly encountered on industrial sites and also representative of certain transport containers. Numerous pressure sensors installed within the table or the pad thickness and on the surface of the hemicylinders provided the overpressure evolution for different values of the charge to obstacle distance. Explosive charges were ignited at distances up to 3.5 m/kg1/3 from the obstacle at ISL scale to extend the applicability domain of the model described in our previous document (Trélat et al. [18]) at a larger scale. The objective of this work is to assess not only blast effects on a potential target but also its capability to modify the blast propagation in its downstream space.</p> ]]> Towards a Model to Predict Blast Propagation Around a Hemicylindrical Barrier s. trélat m. o. sturtzer d. eckenfels doi: 10.2495/CMEM-V9-N4-327-338 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 327 10.2495/CMEM-V9-N4-327-338 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-327-338 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-309-326 Survey of heritage structures, reliability assessment and subsequent design of appropriate interventions are disciplines where intensive multidisciplinary cooperation between architects, civil engineers and heritage preservation specialists is necessary. Surveys including visual inspections, measurements and tests provide vital information for reliability assessment. Non-destructive or minor-destructive tests are generally preferred in surveys of heritage structures. However, reliability assessments providing key information for decisions on structural interventions may require more detailed insights that may only be obtained by destructive tests. This is why incomplete information from a survey overly restricted to protect heritage values may lead to imprecise reliability assessment and to suboptimal decisions on structural interventions. As a consequence, such interventions may then lead to a loss of heritage value that might have been avoided. To provide guidance for practical applications, the submitted contribution presents an analysis of segments of heritage value that may be associated with buildings or bridges. Basis of the method was recently included into the Czech standard on assessment of existing structures. Sensitivity of each segment to the invasiveness of various methods of structural surveys is then discussed, considering also the potential need for input of reliability assessment. The presented framework is applied in the case study of a historic steel bridge located in the UNESCO site – historic centre of Prague. The contribution demonstrates that the segmentation of a heritage value by heritage preservation specialists and architects often helps to identify an optimal strategy for structural survey that provides sufficient information for detailed reliability assessment of the heritage structure. The case study presents a benchmark to be further developed and refined for its effective operational use in practice in the future. <![CDATA[ <p>Survey of heritage structures, reliability assessment and subsequent design of appropriate interventions are disciplines where intensive multidisciplinary cooperation between architects, civil engineers and heritage preservation specialists is necessary. Surveys including visual inspections, measurements and tests provide vital information for reliability assessment. Non-destructive or minor-destructive tests are generally preferred in surveys of heritage structures. However, reliability assessments providing key information for decisions on structural interventions may require more detailed insights that may only be obtained by destructive tests. This is why incomplete information from a survey overly restricted to protect heritage values may lead to imprecise reliability assessment and to suboptimal decisions on structural interventions. As a consequence, such interventions may then lead to a loss of heritage value that might have been avoided. To provide guidance for practical applications, the submitted contribution presents an analysis of segments of heritage value that may be associated with buildings or bridges. Basis of the method was recently included into the Czech standard on assessment of existing structures. Sensitivity of each segment to the invasiveness of various methods of structural surveys is then discussed, considering also the potential need for input of reliability assessment. The presented framework is applied in the case study of a historic steel bridge located in the UNESCO site – historic centre of Prague. The contribution demonstrates that the segmentation of a heritage value by heritage preservation specialists and architects often helps to identify an optimal strategy for structural survey that provides sufficient information for detailed reliability assessment of the heritage structure. The case study presents a benchmark to be further developed and refined for its effective operational use in practice in the future.</p> ]]> Heritage Value Assessment Method – Application to Historic Steel Bridge in Prague sophie eberhardt martin pospisil pavel ryjacek miroslav sykora doi: 10.2495/CMEM-V9-N4-309-326 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 309 10.2495/CMEM-V9-N4-309-326 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-309-326 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-296-308 Masonry walls are one of the most widely used constructive elements in buildings. They offer a cost-effective option and can satisfy many buildings requirements. However, their brittle composition leads them to generate high-speed debris under blast loads. Many casualties arise due to this kind of fragments. Strengthening of masonry walls is of much importance to increase safety inside the buildings. For this purpose, it is desirable to carry out field tests to assess the improvement of reinforcement measures, but the cost and complexity of these experiments can be very high. Therefore, numerical modelling is a good alternative to evaluate the behaviour of brick masonry walls under blast loads. Uncertainties in numerical modelling may be significant due to the composite nature of the reinforced masonry construction and the number of variables describing the constituent materials. In this work, a finite element simulation of a blast-loaded brick masonry wall validated with corresponding field tests is presented. A total of 24 brickwork masonry walls panels at full scale were tested in six different trials with explosives charges. In the configuration of each test, there was one unreinforced wall and three walls with different protective solutions. This paper focuses on the study of unreinforced walls. A 3D pure Lagrangian approach using LS-DYNA was developed with appropriate blast parameters derived from CONWEP, material models and suitable boundary conditions. Results of numerical modelling are compared in terms of wall displacement with the field data obtained in the trials. Study results show good agreement between the field test and the numerical modelling, demonstrating that the model is consistent and reliable. <![CDATA[ <p>Masonry walls are one of the most widely used constructive elements in buildings. They offer a cost-effective option and can satisfy many buildings requirements. However, their brittle composition leads them to generate high-speed debris under blast loads. Many casualties arise due to this kind of fragments. Strengthening of masonry walls is of much importance to increase safety inside the buildings. For this purpose, it is desirable to carry out field tests to assess the improvement of reinforcement measures, but the cost and complexity of these experiments can be very high. Therefore, numerical modelling is a good alternative to evaluate the behaviour of brick masonry walls under blast loads. Uncertainties in numerical modelling may be significant due to the composite nature of the reinforced masonry construction and the number of variables describing the constituent materials. In this work, a finite element simulation of a blast-loaded brick masonry wall validated with corresponding field tests is presented. A total of 24 brickwork masonry walls panels at full scale were tested in six different trials with explosives charges. In the configuration of each test, there was one unreinforced wall and three walls with different protective solutions. This paper focuses on the study of unreinforced walls. A 3D pure Lagrangian approach using LS-DYNA was developed with appropriate blast parameters derived from CONWEP, material models and suitable boundary conditions. Results of numerical modelling are compared in terms of wall displacement with the field data obtained in the trials. Study results show good agreement between the field test and the numerical modelling, demonstrating that the model is consistent and reliable.</p> ]]> Numerical and Experimental Study of Unreinforced Brick Masonry Walls Subjected to Blast Loads maría chiquito simon k. clubley santiago martinez-almajan anastasio p. santos ricardo castedo lina m. lopez doi: 10.2495/CMEM-V9-N4-296-308 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 296 10.2495/CMEM-V9-N4-296-308 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-296-308 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-283-295 Osteosynthesis is a surgical technique for the treatment of skeletal fractures through the implant of mechanical devices, such as plates and screws, in order to stabilize and fix the injured skeletal segment. It is preferred to the conservative treatment when the fracture requires immediate surgical correction or when, blocking the joints, degenerative changes could occur. Bone screws have different shapes and sizes depending on the intended use. In this study, six types of cortical bone screws were tested to determine the torque transmitted to the bone during the insertion. One Ti6Al4V tapered (Ø 6 mm) and five AISI 316L stainless steel – two straight (Ø 4 and 6 mm) and three tapered (Ø 4, 5, and 6 mm) – screws were used during the tests. Screws have been screwed into Sawbones (Sawbones® Pacific Research Laboratories, Inc., Vashon, USA) solid foam-type cylinders (external diameter 30 mm and thickness 3.5 mm) simulating the cortical bone diaphysis. Each of the 26 screws tested was inserted in a Sawbone cylinder five times, in five previously drawn equally spaced points, without any pilot holes. The experiment design was based on the ASTM standard for medical bone screws; two experi- enced orthopedic surgeons performed the insertions and removals of the screws using a hand-drill at 1 rev/s, aided by a metronome, and the torque was measured with a torsiometer throughout the tests. The mean and maximum torque resulted to be higher for larger diameter screws. Considering the same diameter, tapered screws showed a higher torque required for the extraction, which indicates stronger retention. However, in some cases, the Sawbones cylinder was fractured during the insertion of screws with a 6 mm diameter. Therefore, the use of medium-size tapered screws might be the most advisable compromise. <![CDATA[ <p>Osteosynthesis is a surgical technique for the treatment of skeletal fractures through the implant of mechanical devices, such as plates and screws, in order to stabilize and fix the injured skeletal segment. It is preferred to the conservative treatment when the fracture requires immediate surgical correction or when, blocking the joints, degenerative changes could occur. Bone screws have different shapes and sizes depending on the intended use. In this study, six types of cortical bone screws were tested to determine the torque transmitted to the bone during the insertion. One Ti6Al4V tapered (Ø 6 mm) and five AISI 316L stainless steel – two straight (Ø 4 and 6 mm) and three tapered (Ø 4, 5, and 6 mm) – screws were used during the tests. Screws have been screwed into Sawbones (Sawbones® Pacific Research Laboratories, Inc., Vashon, USA) solid foam-type cylinders (external diameter 30 mm and thickness 3.5 mm) simulating the cortical bone diaphysis. Each of the 26 screws tested was inserted in a Sawbone cylinder five times, in five previously drawn equally spaced points, without any pilot holes. The experiment design was based on the ASTM standard for medical bone screws; two experi- enced orthopedic surgeons performed the insertions and removals of the screws using a hand-drill at 1 rev/s, aided by a metronome, and the torque was measured with a torsiometer throughout the tests. The mean and maximum torque resulted to be higher for larger diameter screws. Considering the same diameter, tapered screws showed a higher torque required for the extraction, which indicates stronger retention. However, in some cases, the Sawbones cylinder was fractured during the insertion of screws with a 6 mm diameter. Therefore, the use of medium-size tapered screws might be the most advisable compromise.</p> ]]> Cortical Bone Screws Constructive Characteristics – A Comparative Study andrea t. lugas domenico c. aloj daniele santoro vittoria civilini simone borrelli cristina bignardi doi: 10.2495/CMEM-V9-N4-283-295 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 4 Article 283 10.2495/CMEM-V9-N4-283-295 https://www.acadlore.com/article/IJCMEM/2021_9_4/CMEM-V9-N4-283-295 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-261-275 An Eulerian–Lagrangian model is developed to investigate the solid particle migration in low Reynolds number shear flows between two parallel plates. A continuous kernel function with a predefined thickness is applied in the implemented numerical model to smooth the discontinuity at the interface between primary and secondary phases. At each time step, the solid particle’s rotation and displacement are calculated to directly capture the interaction between the solid particle and primary liquid phase without simplification. Solution verification is performed using the global deviation grid convergence index approach. The observed order of accuracy for the primary phase solver approaches 2, consistent with the formal order of accuracy of the applied discretization scheme. The obtained velocity profiles from the implemented numerical approach show a good agreement with the analytical solution, confirming the single-phase flow solver’s reliability. The obtained numerical results from the applied Eulerian–Lagrangian multiphase model are also compared with experimental data from a linear shear flow apparatus with suspended buoyant particles, and good agreement was found. <![CDATA[ <p>An Eulerian–Lagrangian model is developed to investigate the solid particle migration in low Reynolds number shear flows between two parallel plates. A continuous kernel function with a predefined thickness is applied in the implemented numerical model to smooth the discontinuity at the interface between primary and secondary phases. At each time step, the solid particle’s rotation and displacement are calculated to directly capture the interaction between the solid particle and primary liquid phase without simplification. Solution verification is performed using the global deviation grid convergence index approach. The observed order of accuracy for the primary phase solver approaches 2, consistent with the formal order of accuracy of the applied discretization scheme. The obtained velocity profiles from the implemented numerical approach show a good agreement with the analytical solution, confirming the single-phase flow solver’s reliability. The obtained numerical results from the applied Eulerian–Lagrangian multiphase model are also compared with experimental data from a linear shear flow apparatus with suspended buoyant particles, and good agreement was found.</p> ]]> Spherical Particle Migration Evaluation in Low Reynolds Number Couette Flow Using Smooth Profile Method mahyar pourghasemi nima fathi peter vorobieff goodarz ahmadi seyed sobhan aleyasin luís eça doi: 10.2495/CMEM-V9-N3-261-275 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 261 10.2495/CMEM-V9-N3-261-275 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-261-275 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-249-260 The correct prediction of ductile fracture of mechanical components requires the knowledge of physical quantities that are in the plastic field. This region is characterized by non-linearities, and the classical yield criteria cannot be applied since they work only in the elastic field. It has been observed that parameters such as stress triaxiality and plastic strain play a determinant role in failure mechanisms. Thanks to simulation software, it is possible to implement the virtual models capable of calculating these parameters numerically by solving partial differential equations. These parameters can then be used to describe the fracture locus of a material that, in turn, allows to predict failure of a component. In this work, the Rice and Tracey damage model was calibrated for an aluminum alloy and validated on a punch test exploiting Finite Element Analysis. Good agreement between experimental observations and numerical results was obtained, demonstrating the capability of the considered model to predict failure on a real test case. <![CDATA[ <p>The correct prediction of ductile fracture of mechanical components requires the knowledge of physical quantities that are in the plastic field. This region is characterized by non-linearities, and the classical yield criteria cannot be applied since they work only in the elastic field. It has been observed that parameters such as stress triaxiality and plastic strain play a determinant role in failure mechanisms. Thanks to simulation software, it is possible to implement the virtual models capable of calculating these parameters numerically by solving partial differential equations. These parameters can then be used to describe the fracture locus of a material that, in turn, allows to predict failure of a component. In this work, the Rice and Tracey damage model was calibrated for an aluminum alloy and validated on a punch test exploiting Finite Element Analysis. Good agreement between experimental observations and numerical results was obtained, demonstrating the capability of the considered model to predict failure on a real test case.</p> ]]> Ductile Damage Model of an Alluminum Alloy: Experimental and Numerical Validation on a Punch Test marco nicola mastrone lorenzo fraccaroli franco concli doi: 10.2495/CMEM-V9-N3-249-260 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 249 10.2495/CMEM-V9-N3-249-260 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-249-260 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-239-248 The increasing resource consumption, waste generation, and carbon footprint in the construction sector has drawn the attention of builders and researchers to alternative sustainable construction techniques and materials, such as rammed earth (RE). The mechanical behavior of RE is often enhanced through the use of diverse additives; although cement is probably the most common one, lime stabilization provides some important advantages, representing a more efficient and environmentally friendly solution with a long tradition in the improvement of the mechanical and hydraulic behavior of earthen materials. However, there are still several aspects regarding the effect of lime stabilization in RE mechanical properties that have not been thoroughly evaluated. In this regard, the present study analyze two of the main parameters concerning lime-stabilized rammed earth (LSRE), which are essential to ensure the correct use of this technique: the optimum lime content and the curing time. Several RE specimens with different lime contents, from 0 to 18% by weight, were manufactured and subjected to unconfined compression tests in order to obtain and compare their uniaxial compressive strength (UCS) and elastic modulus. An optimum lime content equal to 12% was obtained. Then, more LSRE samples with 12% lime were manufactured and tested at increasing curing times during 100 days to evaluate the development of their strength and stiffness. The results showed a logarithmic growth of both the UCS and the elastic modulus, with the majority of the strength (over 80%) developed during the first 30 days. In addition, non-destructive ultrasonic pulse velocity tests were carried out on the samples, proving to be a useful tool for predicting the mechanical properties of the material without damaging the specimens. <![CDATA[ <p>The increasing resource consumption, waste generation, and carbon footprint in the construction sector has drawn the attention of builders and researchers to alternative sustainable construction techniques and materials, such as rammed earth (RE). The mechanical behavior of RE is often enhanced through the use of diverse additives; although cement is probably the most common one, lime stabilization provides some important advantages, representing a more efficient and environmentally friendly solution with a long tradition in the improvement of the mechanical and hydraulic behavior of earthen materials. However, there are still several aspects regarding the effect of lime stabilization in RE mechanical properties that have not been thoroughly evaluated. In this regard, the present study analyze two of the main parameters concerning lime-stabilized rammed earth (LSRE), which are essential to ensure the correct use of this technique: the optimum lime content and the curing time. Several RE specimens with different lime contents, from 0 to 18% by weight, were manufactured and subjected to unconfined compression tests in order to obtain and compare their uniaxial compressive strength (UCS) and elastic modulus. An optimum lime content equal to 12% was obtained. Then, more LSRE samples with 12% lime were manufactured and tested at increasing curing times during 100 days to evaluate the development of their strength and stiffness. The results showed a logarithmic growth of both the UCS and the elastic modulus, with the majority of the strength (over 80%) developed during the first 30 days. In addition, non-destructive ultrasonic pulse velocity tests were carried out on the samples, proving to be a useful tool for predicting the mechanical properties of the material without damaging the specimens.</p> ]]> Experimental Evaluation of the Optimum Lime Content and Strength Development of Lime-Stabilized Rammed Earth fernando ávila esther puertas rafael gallego doi: 10.2495/CMEM-V9-N3-239-248 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 239 10.2495/CMEM-V9-N3-239-248 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-239-248 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-226-238 The study of the biomechanics of the human spine is not yet developed extensively. Recent developments in this field have heightened the need for observing the spine from a comprehensive perspective to understand the complex biomechanical patterns, which underlie the kinematic and dynamic responses of this multiple-joint column. Within this frame of exigence, a joint study embracing experimental tests and multibody modelling was designed. This study provides novel insights to the segmental contribution profiles in flexion and extension, analysing different forms of sagittal-plane angles. Moreover, the validation of the multibody model contributes to defining the key aspects for a consistent spine modelling as well as it introduces the basis for simulating pathological conditions and post-orthopaedic surgical outcomes. <![CDATA[ <p>The study of the biomechanics of the human spine is not yet developed extensively. Recent developments in this field have heightened the need for observing the spine from a comprehensive perspective to understand the complex biomechanical patterns, which underlie the kinematic and dynamic responses of this multiple-joint column. Within this frame of exigence, a joint study embracing experimental tests and multibody modelling was designed. This study provides novel insights to the segmental contribution profiles in flexion and extension, analysing different forms of sagittal-plane angles. Moreover, the validation of the multibody model contributes to defining the key aspects for a consistent spine modelling as well as it introduces the basis for simulating pathological conditions and post-orthopaedic surgical outcomes.</p> ]]> Phantom-Based Lumbar Spine Experimental Investigation and Validation of a Multibody Model simone borrelli andrea formaggio vittoria civilini andrea t. lugas doi: 10.2495/CMEM-V9-N3-226-238 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 226 10.2495/CMEM-V9-N3-226-238 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-226-238 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-213-225 The validation of the operationality of models is considered a crucial step in the model development process. Recent developments in Digital Twinning (DT) enable the online availability of operational data from the physical asset required for operational validation. The benefits of DT in situations where operational validation has formed a basis for model adaptation has also been demonstrated. However, these benefits within DT have not been fully utilized due to the lack of an approach for benchmarking the required quantity, quality and diversity of validation data and performance metrics for online model validation and adaptation. Therefore, there is a need for a framework for benchmarking validation data and metrics requirements during model validation in different domains. An approach for bench-marking the required quantity, quality and variability of validation data and performance metric(s) for online model adaptation within DT is proposed. The approach is focused on addressing the problem of parameter(s) uncertainty of a predictive model within its uncertainty boundary. It involves generating virtual test models, a primary and another reference model for the performance evaluation of one compared to the another with the benchmarked validating data and metrics within DT. This process is repeated until the dataset and/or metric(s) are promising enough to validate primary model against the reference model. The proposed approach is demonstrated using BEASY – a simulator designed to pre- dict protection provided by a cathodic protection system to an asset. In this case, a marine structure is the focus of the study, where the protection potentials to prevent corrosion are predicted over the life of the structure. The algorithm(s) for the approach are provided within a Scientific Software (MATLAB) and integrated to the simulator-based cathodic-protection model. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The validation of the operationality of models is considered a crucial step in the model development process. Recent developments in Digital Twinning (DT) enable the online availability of operational data from the physical asset required for operational validation. The benefits of DT in situations where operational validation has formed a basis for model adaptation has also been demonstrated. However, these benefits within DT have not been fully utilized due to the lack of an approach for benchmarking the required quantity, quality and diversity of validation data and performance metrics for online model validation and adaptation. Therefore, there is a need for a framework for benchmarking validation data and metrics requirements during model validation in different domains. An approach for bench-marking the required quantity, quality and variability of validation data and performance metric(s) for online model adaptation within DT is proposed. The approach is focused on addressing the problem of parameter(s) uncertainty of a predictive model within its uncertainty boundary. It involves generating virtual test models, a primary and another reference model for the performance evaluation of one compared to the another with the benchmarked validating data and metrics within DT. This process is repeated until the dataset and/or metric(s) are promising enough to validate primary model against the reference model. The proposed approach is demonstrated using BEASY – a simulator designed to pre- dict protection provided by a cathodic protection system to an asset. In this case, a marine structure is the focus of the study, where the protection potentials to prevent corrosion are predicted over the life of the structure. The algorithm(s) for the approach are provided within a Scientific Software (MATLAB) and integrated to the simulator-based cathodic-protection model.</span></p> ]]> An Approach for Adaptive Model Performance Validation Within Digital Twinning madhu sudan sapkota edward apeh mark hadfield roya haratian robert adey john baynham doi: 10.2495/CMEM-V9-N3-213-225 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 213 10.2495/CMEM-V9-N3-213-225 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-213-225 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-201-212 This work deals with the response of eight reinforced concrete (RC) slabs, made at full-scale, some of them with the addition of externally bonded fibre reinforced polymer (FRP). The reinforcements were placed in all cases on the face opposite to the explosive detonation. Three scaled distances have been used from 0.83 m/kg1/3, in one test with no extra reinforcement; four tests were made with a scaled distance of 0.42 m/kg1/3: one without extra reinforcement, two with carbon fibre reinforcement (CFRP) and one with the E-glass fibre reinforcement (GFRP); finally, 0.21 m/kg1/3, in three trials, one without extra reinforcement, one with carbon fibre reinforcement and one with the E-GFRP. The first slab, used for calibration of the numerical models, was instrumented with pressure and acceleration sensors. For the validation of the other seven slabs, the damage surfaces on both sides of the slabs are used. In terms of numerical simulation performed with LS-DYNA, several models covering different solutions such as smooth particle hydrodynamics (SPH) or load blast enhanced have been performed for the description of the explosive, as well as the use of CSCM material models for concrete to analyse the best available solutions. The steel was modelled with the piecewise linear plasticity material, while the material laminated composite fabric was used for the FRP. Reinforcement with CFRP resulted in a generally reduced damage area on both surfaces. All models show a good correlation, including non- spherical charges made with SPH models, with the test results when comparing them with respect to acceleration and surface damage. SPH models work well for the high and medium scaled distance, but not so good for the shorter scaled distance. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This work deals with the response of eight reinforced concrete (RC) slabs, made at full-scale, some of them with the addition of externally bonded fibre reinforced polymer (FRP). The reinforcements were placed in all cases on the face opposite to the explosive detonation. Three scaled distances have been used from 0.83 m/kg1/3, in one test with no extra reinforcement; four tests were made with a scaled distance of 0.42 m/kg1/3: one without extra reinforcement, two with carbon fibre reinforcement (CFRP) and one with the E-glass fibre reinforcement (GFRP); finally, 0.21 m/kg1/3, in three trials, one without extra reinforcement, one with carbon fibre reinforcement and one with the E-GFRP. The first slab, used for calibration of the numerical models, was instrumented with pressure and acceleration sensors. For the validation of the other seven slabs, the damage surfaces on both sides of the slabs are used. In terms of numerical simulation performed with LS-DYNA, several models covering different solutions such as smooth particle hydrodynamics (SPH) or load blast enhanced have been performed for the description of the explosive, as well as the use of CSCM material models for concrete to analyse the best available solutions. The steel was modelled with the piecewise linear plasticity material, while the material laminated composite fabric was used for the FRP. Reinforcement with CFRP resulted in a generally reduced damage area on both surfaces. All models show a good correlation, including non- spherical charges made with SPH models, with the test results when comparing them with respect to acceleration and surface damage. SPH models work well for the high and medium scaled distance, but not so good for the shorter scaled distance.</span></p> ]]> Field Test and Numerical Modelling of RC Slabs at Different Scaled Distances with Two Types of External Reinforcement santiago martínez-almajano ricardo castedo lina mª lópez anastasio p. santos maría chiquito alejandro alañón carlos reifarth doi: 10.2495/CMEM-V9-N3-201-212 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 201 10.2495/CMEM-V9-N3-201-212 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-201-212 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-189-200 This paper outlines the prediction of a macroscopic viscoelastic response of plain weave textile composites made either from basalt or carbon fiber tows impregnated by polymeric matrix. Owing to a natural orthotropic response at the level of yarns, the calibration of a simple meso-scale constitutive model from virtual laboratory tests is precluded and a fully coupled analysis is needed instead. One option is solving the problem in the framework of FE analysis when both the micro- and meso-scale problems are solved with the help of the finite element method. This requires formulation of a suitable computational model most often represented by a statistically equivalent periodic unit cell on both scales. However, such an approach may prove computationally expensive particularly at stages of initial design where a large parametric study is often needed to test various material and geometrical configurations. A suitable method of attack then arises from the application of computationally efficient classical micromechanical models such as the Mori-Tanaka (MT) method. This approach is examined in the present study. While the present work is mostly computational, it requires an extensive experimental program to tune the generalized Leonov constitutive model describing the behavior of the matrix phase. Additionally, a series of virtual laboratory tests is carried out at the level of yarns to improve the predictive capability of the MT method. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper outlines the prediction of a macroscopic viscoelastic response of plain weave textile composites made either from basalt or carbon fiber tows impregnated by polymeric matrix. Owing to a natural orthotropic response at the level of yarns, the calibration of a simple meso-scale constitutive model from virtual laboratory tests is precluded and a fully coupled analysis is needed instead. One option is solving the problem in the framework of FE analysis when both the micro- and meso-scale problems are solved with the help of the finite element method. This requires formulation of a suitable computational model most often represented by a statistically equivalent periodic unit cell on both scales. However, such an approach may prove computationally expensive particularly at stages of initial design where a large parametric study is often needed to test various material and geometrical configurations. A suitable method of attack then arises from the application of computationally efficient classical micromechanical models such as the Mori-Tanaka (MT) method. This approach is examined in the present study. While the present work is mostly computational, it requires an extensive experimental program to tune the generalized Leonov constitutive model describing the behavior of the matrix phase. Additionally, a series of virtual laboratory tests is carried out at the level of yarns to improve the predictive capability of the MT method.</span></p> ]]> Multiscale Viscoelastic Analysis of Plain Weave Textile Composites m. šejnoha j. vorel s. valentová g. marseglia doi: 10.2495/CMEM-V9-N3-189-200 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 3 Article 189 10.2495/CMEM-V9-N3-189-200 https://www.acadlore.com/article/IJCMEM/2021_9_3/CMEM-V9-N3-189-200 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-93-107 The establishment of the Sustainable Development Goals in 2015 claims for a deep paradigm shift in the way infrastructure structures are conceived. The evaluation of the impacts derived from the con- struction, the service and the end-of-life stages of an infrastructure is consequently in the spotlight of the research community. Being the construction sector as one of the main stressors of the environment, great attention has been recently paid to the structural design from the economic and the environmental point of view. However, sustainability requires to consider the social dimension as well. The evaluation of the social impacts of products is still at a very early stage of development, so the inclusion of social aspects in the design of structures is often overlooked. In this study, a comparison of life cycle assess- ment results is conducted on seven different design alternatives for a bridge in a coastal environment. Two approaches are followed: the first approach considers the economic and the environmental aspects of each design and the second approach includes the several social impacts specifically developed for the assessment of infrastructures. These social impacts account for four stakeholders, namely workers, consumers, local community and society. Results show that the inclusion of social aspects shall lead to different preferred options when compared with conventional, two-dimensional approaches. Here, the design with silica fume added concrete performs 11% better from a sustainability point of view when compared with the best solution resulting from a conventional assessment. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The establishment of the Sustainable Development Goals in 2015 claims for a deep paradigm shift in the way infrastructure structures are conceived. The evaluation of the impacts derived from the con- struction, the service and the end-of-life stages of an infrastructure is consequently in the spotlight of the research community. Being the construction sector as one of the main stressors of the environment, great attention has been recently paid to the structural design from the economic and the environmental point of view. However, sustainability requires to consider the social dimension as well. The evaluation of the social impacts of products is still at a very early stage of development, so the inclusion of social aspects in the design of structures is often overlooked. In this study, a comparison of life cycle assess- ment results is conducted on seven different design alternatives for a bridge in a coastal environment. Two approaches are followed: the first approach considers the economic and the environmental aspects of each design and the second approach includes the several social impacts specifically developed for the assessment of infrastructures. These social impacts account for four stakeholders, namely workers, consumers, local community and society. Results show that the inclusion of social aspects shall lead to different preferred options when compared with conventional, two-dimensional approaches. Here, the design with silica fume added concrete performs 11% better from a sustainability point of view when compared with the best solution resulting from a conventional assessment.</span></p> ]]> Sustainability Life Cycle Design of Bridges in Aggressive Environments Considering Social Impacts ignacio j. navarro víctor yepes josé v. martí doi: 10.2495/CMEM-V9-N2-93-107 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 93 10.2495/CMEM-V9-N2-93-107 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-93-107 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-165-179 A general approach that utilizes both spectral and extremal statistical methods are utilized to investigate the time series of flow-induced response behavior of a flexible horizontal cylinder subject to both random waves and constant current conditions. The cylinder model was 29 m long and had a slenderness ratio of approximately 760. The random waves were generated using a JONSWAP wave amplitude spectrum. In addition, for some tests, the cylinder was towed at two different speeds to simulate the combined loading of random waves and constant current conditions. The data were initially analyzed using standard spectral analyses to interpret the cylinder’s flow-induced response behavior and relate the findings to traditional deterministic parameters. Further analyses were performed using a generalized extreme value (GEV) distribution procedure that involved dividing the time series into blocks and fitting the block maxima of the extreme values in the measured response time series data. The Anderson–Darling (AD) test criterion and quantile plots were then used to assess whether the GEV distribution provides a satisfactory fit to the data capturing the statistical characteristics in the flexible cylinder’s flow-induced response behavior, which was stochastic in nature. For the data set analyzed, the extremal GEV methodology presented was observed to provide excellent results for the random wave cases and moderately good-to-good results for the combined random wave and constant current cases. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A general approach that utilizes both spectral and extremal statistical methods are utilized to investigate the time series of flow-induced response behavior of a flexible horizontal cylinder subject to both random waves and constant current conditions. The cylinder model was 29 m long and had a slenderness ratio of approximately 760. The random waves were generated using a JONSWAP wave amplitude spectrum. In addition, for some tests, the cylinder was towed at two different speeds to simulate the combined loading of random waves and constant current conditions. The data were initially analyzed using standard spectral analyses to interpret the cylinder’s flow-induced response behavior and relate the findings to traditional deterministic parameters. Further analyses were performed using a generalized extreme value (GEV) distribution procedure that involved dividing the time series into blocks and fitting the block maxima of the extreme values in the measured response time series data. The Anderson–Darling (AD) test criterion and quantile plots were then used to assess whether the GEV distribution provides a satisfactory fit to the data capturing the statistical characteristics in the flexible cylinder’s flow-induced response behavior, which was stochastic in nature. For the data set analyzed, the extremal GEV methodology presented was observed to provide excellent results for the random wave cases and moderately good-to-good results for the combined random wave and constant current cases.</span></p> ]]> Spectral and Statistical Analysis of Flow-Induced Vibrations jiangnan lu j. m. niedzwecki doi: 10.2495/CMEM-V9-N2-165-179 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 165 10.2495/CMEM-V9-N2-165-179 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-165-179 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-153-164 With the rapid development of hypersonic vehicles in recent years, high-temperature seal technology has become more and more essential. Recently, a rope-sealed structure with braided ceramic fibres has been designed for hypersonic vehicles. The ceramic fibres in the structure have the characteristics of high temperature strength, so that they make the sealed structure suitable for working under a high temperature. Meanwhile, when subjected to an external force, braided fibres can produce a buffer force at the ceramic interface, so that it can maintain the good performance of the whole sealed structure. But up to now, only a few researches have been conducted on this kind of structures. In this paper, a simplified thermal–mechanical seepage coupling model is proposed to simulate the complicated physical process for this kind of structures. Meanwhile, a new numerical method called element differential method (EDM) is used to calculate the coupling problem because it has great advantages in solving multi-physics coupling problems. What is more, some experiments are used to obtain the leakages when the sealed structure is under service. And finally, by referring the experimental results, the authors establish a series of material parameter relationships for the sealed structure and also verify the reasonability of the proposed multi-physics coupling model. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">With the rapid development of hypersonic vehicles in recent years, high-temperature seal technology has become more and more essential. Recently, a rope-sealed structure with braided ceramic fibres has been designed for hypersonic vehicles. The ceramic fibres in the structure have the characteristics of high temperature strength, so that they make the sealed structure suitable for working under a high temperature. Meanwhile, when subjected to an external force, braided fibres can produce a buffer force at the ceramic interface, so that it can maintain the good performance of the whole sealed structure. But up to now, only a few researches have been conducted on this kind of structures. In this paper, a simplified thermal–mechanical seepage coupling model is proposed to simulate the complicated physical process for this kind of structures. Meanwhile, a new numerical method called element differential method (EDM) is used to calculate the coupling problem because it has great advantages in solving multi-physics coupling problems. What is more, some experiments are used to obtain the leakages when the sealed structure is under service. And finally, by referring the experimental results, the authors establish a series of material parameter relationships for the sealed structure and also verify the reasonability of the proposed multi-physics coupling model.</span></p> ]]> Multi-Physics Coupling Analysis of Rope-Sealed Structures with Braided Ceramic Fibres by Element Differential Method yongtong zheng xiaowei gao sheng liu yanjing man kai yang doi: 10.2495/CMEM-V9-N2-153-164 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 153 10.2495/CMEM-V9-N2-153-164 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-153-164 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-141-152 As classically proposed in the technical literature, the boundary element modeling of cracks is best carried out by resorting to a hypersingular fundamental solution – in the frame of the so-called dual formulation – since with the singular fundamental solution alone, the ensuing topological issues would not be adequately tackled. A more natural approach might rely on the direct representation of the crack tip singularity, as already proposed in the frame of the hybrid boundary element method, with implementation of generalized Westergaard stress functions. On the other hand, recent mathematical assessments indicate that the conventional boundary element formulation – based on Kelvin’s fundamental solution – is, in fact, able to precisely represent high stress gradients and deal with extremely convoluted topologies provided only that the numerical integrations be properly resolved. We propose in this paper that inde- pendent of the configuration, a cracked structure is geometrically represented as it would appear in real-world laboratory experiments, with crack openings in the range of micrometers. (The nanometer range is actually mathematically feasible, but not realistic in terms of continuum mechanics.) Owing to the newly developed numerical integration scheme, machine precision evaluation of all quantities may be achieved and stress results consistently evaluated at interior points arbitrarily close to crack tips. Importantly, no artificial topological issues are introduced, linear algebra conditioning is kept well under control, and arbitrarily high convergence of results is always attainable. The present develop- ments apply to two-dimensional problems. Some numerical illustrations show that highly accurate results are obtained for cracks represented with just a few quadratic, generally curved, boundary ele- ments – and a few Gauss–Legendre integration points per element – and that the numerical evaluation of the J-integral turns out to be straightforward and actually the most reliable means of obtaining stress intensity factors. Higher-order boundary elements lead to still better results. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">As classically proposed in the technical literature, the boundary element modeling of cracks is best carried out by resorting to a hypersingular fundamental solution – in the frame of the so-called dual formulation – since with the singular fundamental solution alone, the ensuing topological issues would not be adequately tackled. A more natural approach might rely on the direct representation of the crack tip singularity, as already proposed in the frame of the hybrid boundary element method, with implementation of generalized Westergaard stress functions. On the other hand, recent mathematical assessments indicate that the conventional boundary element formulation – based on Kelvin’s fundamental solution – is, in fact, able to precisely represent high stress gradients and deal with extremely convoluted topologies provided only that the numerical integrations be properly resolved. We propose in this paper that inde- pendent of the configuration, a cracked structure is geometrically represented as it would appear in real-world laboratory experiments, with crack openings in the range of micrometers. (The nanometer range is actually mathematically feasible, but not realistic in terms of continuum mechanics.) Owing to the newly developed numerical integration scheme, machine precision evaluation of all quantities may be achieved and stress results consistently evaluated at interior points arbitrarily close to crack tips. Importantly, no artificial topological issues are introduced, linear algebra conditioning is kept well under control, and arbitrarily high convergence of results is always attainable. The present develop- ments apply to two-dimensional problems. Some numerical illustrations show that highly accurate results are obtained for cracks represented with just a few quadratic, generally curved, boundary ele- ments – and a few Gauss–Legendre integration points per element – and that the numerical evaluation of the J-integral turns out to be straightforward and actually the most reliable means of obtaining stress intensity factors. Higher-order boundary elements lead to still better results.</span></p> ]]> Machine-Precise Evaluation of Stress Intensity Factors with the Consistent Boundary Element Method ney augusto dumont osmar alexandre do amaral neto doi: 10.2495/CMEM-V9-N2-141-152 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 141 10.2495/CMEM-V9-N2-141-152 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-141-152 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-126-140 The paper deals with the optimization of a single-storey timber building structure designed from timber portal frames connected with steel purlins, rails and façade columns. While the portal frames are made of the glued laminated timber with rectangular cross-sections, purlins, rails and façade columns are made of commercially available steel I-profiles. The portal frames are supported by square concrete pad foundations. The building structure is optimized by a mixed-integer non-linear programming (MINLP). The optimization model is developed. The objective function defines the material costs of the structure. The objective function is subjected to structural analysis and design constraints defined according to Eurocode standards. The Modified Outer-Approximation/Equality-Relaxation algorithm (OA/ER) and the linked multi-level strategy are applied. The optimization determines the minimum material costs of the structure, the optimal number of glulam frames and steel members and all standard/discrete cross- sections. A numerical example at the end of the paper shows the efficiency of the proposed optimization approach. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The paper deals with the optimization of a single-storey timber building structure designed from timber portal frames connected with steel purlins, rails and façade columns. While the portal frames are made of the glued laminated timber with rectangular cross-sections, purlins, rails and façade columns are made of commercially available steel I-profiles. The portal frames are supported by square concrete pad foundations. The building structure is optimized by a mixed-integer non-linear programming (MINLP). The optimization model is developed. The objective function defines the material costs of the structure. The objective function is subjected to structural analysis and design constraints defined according to Eurocode standards. The Modified Outer-Approximation/Equality-Relaxation algorithm (OA/ER) and the linked multi-level strategy are applied. The optimization determines the minimum material costs of the structure, the optimal number of glulam frames and steel members and all standard/discrete cross- sections. A numerical example at the end of the paper shows the efficiency of the proposed optimization approach.</span></p> ]]> Optimization of a Single-Storey Timber Building Structure stojan kravanja tomaž žula doi: 10.2495/CMEM-V9-N2-126-140 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 126 10.2495/CMEM-V9-N2-126-140 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-126-140 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-117-125 Gearboxes are widely used in several applications ranging from the automotive to the industrial and robotic sectors. A planetary gearbox is a special kinematic gear arrangement that, taking advantage of a planet carrier, ensures high reduction ratios together with a very small design. Therefore, they are widely employed for transmissions which require a high power density. There are several fields of applications including, but not limited to, mechatronic, automation and wind power generation. To improve the design of new solutions, for performing monitoring activities on actual gearboxes and for the definition of maintenance schedules, the availability of physical models able to accurately describe the behavior of the system, both in healthy and damaged conditions, would represent a great support. Experimental and numerical studies of the behavior of gearboxes are already available in the literature. Nevertheless, while the experimental approaches are valid only for the specific configuration tested, the numerical techniques show limitations related to the computational effort required. This paper presents an innovative approach for the characterization of the behavior of two different geared transmissions. It is based on a hybrid approach that combines finite elements (FE) with analytical formulations. In detail, the solver computes separately the macro deformation of the bodies (numerical solution based on a coarse grid) and the contacts (solved analytically avoiding the need of mesh refinements). The computational effort is reduced significantly without affecting the accuracy of the results significantly. This approach was used to investigate and understand the vibro-dynamical behavior of a back-to-back test rig (typically used for the characterization of the surface fatigue strength of gears) and of an indus- trial planetary gearbox. The results obtained for the healthy – not damaged – gearboxes were compared with experimental measurements for both configurations in order to validate the hybrid approach. Once the models were validated, the same methodology was eventually used to study the effects of typical gear failures and in specifically surface fatigue (pitting), on the vibrational response. The capability to reproduce the effect of damages with the model of a gearbox represents the first indispensable step of a Structural Health Monitoring strategy. State-of-art and challenges are analyzed and discussed in the paper. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Gearboxes are widely used in several applications ranging from the automotive to the industrial and robotic sectors. A planetary gearbox is a special kinematic gear arrangement that, taking advantage of a planet carrier, ensures high reduction ratios together with a very small design. Therefore, they are widely employed for transmissions which require a high power density. There are several fields of applications including, but not limited to, mechatronic, automation and wind power generation. To improve the design of new solutions, for performing monitoring activities on actual gearboxes and for the definition of maintenance schedules, the availability of physical models able to accurately describe the behavior of the system, both in healthy and damaged conditions, would represent a great support. Experimental and numerical studies of the behavior of gearboxes are already available in the literature. Nevertheless, while the experimental approaches are valid only for the specific configuration tested, the numerical techniques show limitations related to the computational effort required. This paper presents an innovative approach for the characterization of the behavior of two different geared transmissions. It is based on a hybrid approach that combines finite elements (FE) with analytical formulations. In detail, the solver computes separately the macro deformation of the bodies (numerical solution based on a coarse grid) and the contacts (solved analytically avoiding the need of mesh refinements). The computational effort is reduced significantly without affecting the accuracy of the results significantly. This approach was used to investigate and understand the vibro-dynamical behavior of a back-to-back test rig (typically used for the characterization of the surface fatigue strength of gears) and of an indus- trial planetary gearbox. The results obtained for the healthy – not damaged – gearboxes were compared with experimental measurements for both configurations in order to validate the hybrid approach. Once the models were validated, the same methodology was eventually used to study the effects of typical gear failures and in specifically surface fatigue (pitting), on the vibrational response. The capability to reproduce the effect of damages with the model of a gearbox represents the first indispensable step of a Structural Health Monitoring strategy. State-of-art and challenges are analyzed and discussed in the paper.</span></p> ]]> Dynamic Modeling of Gears: An Innovative Hybrid FEM–Analytical Approach franco concli concli gorla doi: 10.2495/CMEM-V9-N2-117-125 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 117 10.2495/CMEM-V9-N2-117-125 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-117-125 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-108-116 This study presents a shape optimization approach for sound barrier using the isogeometric boundary element method based on subdivision surfaces. The geometry model is constructed through the subdivision scheme, and different control polygons/meshes describing the same curve/surface are used for geometry representation, boundary element analysis and optimization. The gradient-based optimization is implemented to minimize the sound pressure in the reference region. By subdivision coarsening treatment, the secondary processing improves the direct optimization results in reducing the oscillation of the optimized structure. The influence of different subdivision schemes on the obtained optimized configurations is studied in detail, which shows the potential of the secondary reverse processing for engineering prototype design. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This study presents a shape optimization approach for sound barrier using the isogeometric boundary element method based on subdivision surfaces. The geometry model is constructed through the subdivision scheme, and different control polygons/meshes describing the same curve/surface are used for geometry representation, boundary element analysis and optimization. The gradient-based optimization is implemented to minimize the sound pressure in the reference region. By subdivision coarsening treatment, the secondary processing improves the direct optimization results in reducing the oscillation of the optimized structure. The influence of different subdivision schemes on the obtained optimized configurations is studied in detail, which shows the potential of the secondary reverse processing for engineering prototype design.</span></p> ]]> Shape Optimization of Acoustic Barriers Based on Subdivision Surfaces BEM chuang lu leilei chen haibo chen doi: 10.2495/CMEM-V9-N2-108-116 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 2 Article 108 10.2495/CMEM-V9-N2-108-116 https://www.acadlore.com/article/IJCMEM/2021_9_2/CMEM-V9-N2-108-116 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-74-82 A special topology optimization problem is considered whose objective functional consists of tangential derivative of the potential on the boundary for two-dimensional Helmholtz equation. In order to derive the adjoint problem, the functional of the conventional topology optimizations required a boundary integral of the potential and its flux. For the present objective functional having the tangential derivative, integration by parts is applied to the part having the tangential derivative of the variation of the potential to generate a tractable adjoint problem. The derived adjoint problem is used in the variation of the objective function, and the topological derivative is derived in the conventional expression. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A special topology optimization problem is considered whose objective functional consists of tangential derivative of the potential on the boundary for two-dimensional Helmholtz equation. In order to derive the adjoint problem, the functional of the conventional topology optimizations required a boundary integral of the potential and its flux. For the present objective functional having the tangential derivative, integration by parts is applied to the part having the tangential derivative of the variation of the potential to generate a tractable adjoint problem. The derived adjoint problem is used in the variation of the objective function, and the topological derivative is derived in the conventional expression.</span></p> ]]> A New Adjoint Problem for Two-Dimensional Helmholtz Equation to Calculate Topological Derivatives of the Objective Functional Having Tangential Derivative Quantities peijun tang toshiro matsumoto hiroshi isakari toru takahashi doi: 10.2495/CMEM-V9-N1-74-82 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 74 10.2495/CMEM-V9-N1-74-82 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-74-82 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-63-73 In this study, a localized collocation method called generalized finite difference method (GFDM) is developed to solve the anomalous diffusion problems on surfaces. The expressions of the surface Laplace operator, surface gradient operator and surface divergence operator in tangent space are given explicitly, which is different from the definition of differential operators in the Euclidean space. Based on the moving least square theorem and Taylor series, GFDM shares similar properties with standard FDM and avoids mesh dependence, enabling numerical approximations of the surface operators on complex 3D surfaces. Simultaneously, a standard finite difference scheme is adopted to discretize the time fractional derivatives. By using GFDM, we succeed in solving both constant- and variable- order time fractional diffusion models on surfaces. Numerical examples show that the present meshless scheme has good accuracy and efficiency for various fractional diffusion models. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In this study, a localized collocation method called generalized finite difference method (GFDM) is developed to solve the anomalous diffusion problems on surfaces. The expressions of the surface Laplace operator, surface gradient operator and surface divergence operator in tangent space are given explicitly, which is different from the definition of differential operators in the Euclidean space. Based on the moving least square theorem and Taylor series, GFDM shares similar properties with standard FDM and avoids mesh dependence, enabling numerical approximations of the surface operators on complex 3D surfaces. Simultaneously, a standard finite difference scheme is adopted to discretize the time fractional derivatives. By using GFDM, we succeed in solving both constant- and variable- order time fractional diffusion models on surfaces. Numerical examples show that the present meshless scheme has good accuracy and efficiency for various fractional diffusion models.</span></p> ]]> Generalized Finite Difference Method for Anomalous Diffusion on Surfaces zhuochao tang zhuojia fu doi: 10.2495/CMEM-V9-N1-63-73 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 63 10.2495/CMEM-V9-N1-63-73 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-63-73 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-51-62 This study aims at evaluating the corrosion rate at the first stage of stress corrosion cracking by a numerical simulation. The stress corrosion cracking starts with a pitting corrosion which appears from a damaged portion of passive film induced by plastic deformation. From micromechanical standpoint, the stress and strain are concentrated around the grain boundaries due to the heterogeneity of microstructures; therefore, the plastic slip occurs mainly around the grain boundaries and generates a fresh surface without passive film. This produces a microcell and affects the macroscopic polarization curve. We obtained this polarization curve of stainless steel from the open-circuit tensile tests associated with the microscopic electrostatic simulations. Moreover, this paper shows the two-dimensional formulation for coupling analysis of elastic stress and electrolytic potential. Both fields are solved by the boundary element method with the discontinuous quadratic element. The strain-dependent polarization curve is used as a nonlinear boundary condition of the potential problem. First, the elastic problem is solved to obtain the surface strain which governs the polarization curve on the surface. Next, the potential problem is solved to obtain the current density on the surface which determines the corrosion rate. Since each node has two corrosion rates in different directions coming from the neighbouring elements, we average these two rates and directions, so as to conserve the volumetric reduction rate unchanged. After moving the nodes as a result of corrosion during the time step, we return to the stress analysis and iterate this procedure during the interested period of time. We demonstrate a corrosion pit growth from a small hemi-elliptic surface defect and show the availability of the proposed method. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This study aims at evaluating the corrosion rate at the first stage of stress corrosion cracking by a numerical simulation. The stress corrosion cracking starts with a pitting corrosion which appears from a damaged portion of passive film induced by plastic deformation. From micromechanical standpoint, the stress and strain are concentrated around the grain boundaries due to the heterogeneity of microstructures; therefore, the plastic slip occurs mainly around the grain boundaries and generates a fresh surface without passive film. This produces a microcell and affects the macroscopic polarization curve. We obtained this polarization curve of stainless steel from the open-circuit tensile tests associated with the microscopic electrostatic simulations. Moreover, this paper shows the two-dimensional formulation for coupling analysis of elastic stress and electrolytic potential. Both fields are solved by the boundary element method with the discontinuous quadratic element. The strain-dependent polarization curve is used as a nonlinear boundary condition of the potential problem. First, the elastic problem is solved to obtain the surface strain which governs the polarization curve on the surface. Next, the potential problem is solved to obtain the current density on the surface which determines the corrosion rate. Since each node has two corrosion rates in different directions coming from the neighbouring elements, we average these two rates and directions, so as to conserve the volumetric reduction rate unchanged. After moving the nodes as a result of corrosion during the time step, we return to the stress analysis and iterate this procedure during the interested period of time. We demonstrate a corrosion pit growth from a small hemi-elliptic surface defect and show the availability of the proposed method.</span></p> ]]> Pitting Corrosion Analysis of Stainless Steel by Boundary Element Method with Strain-Dependent Polarization Curve osamu kuwazuru aruto kawakami yuma miura eduardo divo alain kassab doi: 10.2495/CMEM-V9-N1-51-62 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 51 10.2495/CMEM-V9-N1-51-62 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-51-62 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-38-50 The paper presents a problem of gravitational–capillarity wave propagation in the frame of boundary integral equations. The wave propagation is considered in rigid compound shells of revolution. The liquid is supposed to be an ideal and incompressible one, and its flow is irrotational. The boundary value problem is formulated for Laplace’s equation to obtain the velocity potential. Non-penetration boundary conditions are used at the shell’s wetted surface, as well as kinematic and dynamic boundary conditions are given on the free liquid surface. Effects of surface tension are included in the Bernoulli’s equation as additional pressure that is proportional to the free surface mean curvature. It allows us to consider coupled effects of both gravitational and capillarity waves. The problem is reduced to a system of singular integral equations. For their numerical simulation, the boundary element method is in use. The singular integral equations in implementation of a discrete model are transformed to linear algebraic ones, and eigenvalue problems are solved for different capillarity length numbers. Benchmark numerical investigations are presented including different kinds of compound rigid shells. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The paper presents a problem of gravitational–capillarity wave propagation in the frame of boundary integral equations. The wave propagation is considered in rigid compound shells of revolution. The liquid is supposed to be an ideal and incompressible one, and its flow is irrotational. The boundary value problem is formulated for Laplace’s equation to obtain the velocity potential. Non-penetration boundary conditions are used at the shell’s wetted surface, as well as kinematic and dynamic boundary conditions are given on the free liquid surface. Effects of surface tension are included in the Bernoulli’s equation as additional pressure that is proportional to the free surface mean curvature. It allows us to consider coupled effects of both gravitational and capillarity waves. The problem is reduced to a system of singular integral equations. For their numerical simulation, the boundary element method is in use. The singular integral equations in implementation of a discrete model are transformed to linear algebraic ones, and eigenvalue problems are solved for different capillarity length numbers. Benchmark numerical investigations are presented including different kinds of compound rigid shells.</span></p> ]]> BEM Analysis of Gravitational–Capillarity Waves on Free Surfaces of Compound Shells of Revolution vasyl i. gnitko artem o. karaiev maria l. myronenko elena a. strelnikova doi: 10.2495/CMEM-V9-N1-38-50 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 38 10.2495/CMEM-V9-N1-38-50 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-38-50 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-28-37 In wave–structure interaction problems, energy balance relations are often derived and used to check the accuracy of the computational results obtained using numerical methods. These energy identities are also used to get qualitative information about various physical quantities of interest. It is well known that for rigid structures, the energy identity is Kr2+Kt2= 1, where Kr and Kt are the reflection and transmission coefficients, respectively. Even if we take flexible barriers, then also the aforementioned energy identity will hold. Now, for wave past a thick porous structure, often a major portion of the incoming wave energy is dissipated due to the structural porosity. So, the aforementioned energy identity will be modified into Kr2+Kt2+KD= 1, where KD takes into account the amount of dissipative wave energy. These energy identities are available in the literature for thin porous barriers. But derivation of the energy identity is complicated for thick porous structures due to complex momentum equation and boundary conditions. In the present paper, an appropriate energy identity will be derived for water waves past a thick rectangular porous structure. In this regard, Green’s second identity is used in multi-domain regions with the arguments velocity potential and its complex conjugate. With the help of complex function theory, the final form of the same is written in a compact form. Now, to compute each quantity associated with the energy identity, the associated boundary value problem is converted into a system of Fredholm integral equations. Finally, using the boundary element method, the components present in the energy identity are obtained and checked for validation. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In wave–structure interaction problems, energy balance relations are often derived and used to check the accuracy of the computational results obtained using numerical methods. These energy identities are also used to get qualitative information about various physical quantities of interest. It is well known that for rigid structures, the energy identity is K</span>_r²<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">+K</span>_t²<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">= 1, where K</span>_r<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif"> and K</span>_t<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif"> are the reflection and transmission coefficients, respectively. Even if we take flexible barriers, then also the aforementioned energy identity will hold. Now, for wave past a thick porous structure, often a major portion of the incoming wave energy is dissipated due to the structural porosity. So, the aforementioned energy identity will be modified into K</span>_r²<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">+K</span>_t²<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">+K</span>_D<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">= 1, where K</span>_D<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif"> takes into account the amount of dissipative wave energy. These energy identities are available in the literature for thin porous barriers. But derivation of the energy identity is complicated for thick porous structures due to complex momentum equation and boundary conditions. In the present paper, an appropriate energy identity will be derived for water waves past a thick rectangular porous structure. In this regard, Green’s second identity is used in multi-domain regions with the arguments velocity potential and its complex conjugate. With the help of complex function theory, the final form of the same is written in a compact form. Now, to compute each quantity associated with the energy identity, the associated boundary value problem is converted into a system of Fredholm integral equations. Finally, using the boundary element method, the components present in the energy identity are obtained and checked for validation.</span></p> ]]> Energy Balance Relations for Flow Through Thick Porous Structures santanu koley kottala panduranga doi: 10.2495/CMEM-V9-N1-28-37 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 28 10.2495/CMEM-V9-N1-28-37 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-28-37 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-14-27 In Japan, rail fastenings are required to be checked for their performance by the static loading test. The test is generally performed in the laboratory under the biaxial static loading conditions. The values of the loads and loading angles are determined by using the FEM model of the track. The author has developed the FEM model of a general slab track to determine the loads and loading angles for the laboratory test of rail fastenings. However, the conventional FEM model cannot be applied to the floating slab track. Therefore, in this study, the author has developed a FEM model of the floating slab track and proposes the determination method of load conditions based on a FEM analysis. Results showed that the determination method based on the FEM model can evaluate the performance of rail fastenings of the floating slab track with a higher accuracy than before. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In Japan, rail fastenings are required to be checked for their performance by the static loading test. The test is generally performed in the laboratory under the biaxial static loading conditions. The values of the loads and loading angles are determined by using the FEM model of the track. The author has developed the FEM model of a general slab track to determine the loads and loading angles for the laboratory test of rail fastenings. However, the conventional FEM model cannot be applied to the floating slab track. Therefore, in this study, the author has developed a FEM model of the floating slab track and proposes the determination method of load conditions based on a FEM analysis. Results showed that the determination method based on the FEM model can evaluate the performance of rail fastenings of the floating slab track with a higher accuracy than before.</span></p> ]]> Determination of Load Test Conditions for Rail Fastenings of a Floating Slab Track shingo tamagawa doi: 10.2495/CMEM-V9-N1-14-27 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 14 10.2495/CMEM-V9-N1-14-27 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-14-27 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-1-13 Anthropogenic activities, especially vehicular traffic, produce load of pollutants that accumulate on impervious surfaces. In highways, exhaust, automobile parts wear and lubricating parts along with heavy metals and other pollutants accumulated on the pavement surface during dry periods are the sources of pollution. Rainfall-runoff process promotes surface wash-off, contributing to stormwater pollutants’ load. The cumulative load in runoff is normally expressed as an exponential model with a peak concentration at the beginning of the rainfall event known as the first flush, where most part of the load is washed off at the beginning of the event reaching an early peak. This consideration motivates often the use of a first flush storage tank (FFT) to treat stormwater discharge from highways that is then discharged into water courses without any other treatment. It is considered that the FFT would retain the most polluted part of the runoff; however, a weak first flush is observed in some rainfall events, especially for low flow rates. Also, the vehicular traffic occurring during the rainfall event serves as a continuous source. Therefore, the objective of this research is to compare the efficiency on particle removal of an FFT with other methods of stormwater treatment, in this case an infiltration–exfiltration system (IES) consisting of a gravel swale with porous asphalt surface, through hydrological modelling of six rainfall events measured on a highway in Cincinnati (USA). The results showed a compatible removal rate for both the FFT and IES for the six analysed events, consisting of three mass-limit events and three flow-limit events. Particle transport modelling could represent well the behaviour of the events and can be used as a tool to choose between systems, where after setting the particle removal efficiency, other factors can be considered, like cost and system area consumption. This research can be followed up with continuous rainfall simulations and using computational fluid dynamics (CFD) to model IES particle removal. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Anthropogenic activities, especially vehicular traffic, produce load of pollutants that accumulate on impervious surfaces. In highways, exhaust, automobile parts wear and lubricating parts along with heavy metals and other pollutants accumulated on the pavement surface during dry periods are the sources of pollution. Rainfall-runoff process promotes surface wash-off, contributing to stormwater pollutants’ load. The cumulative load in runoff is normally expressed as an exponential model with a peak concentration at the beginning of the rainfall event known as the first flush, where most part of the load is washed off at the beginning of the event reaching an early peak. This consideration motivates often the use of a first flush storage tank (FFT) to treat stormwater discharge from highways that is then discharged into water courses without any other treatment. It is considered that the FFT would retain the most polluted part of the runoff; however, a weak first flush is observed in some rainfall events, especially for low flow rates. Also, the vehicular traffic occurring during the rainfall event serves as a continuous source. Therefore, the objective of this research is to compare the efficiency on particle removal of an FFT with other methods of stormwater treatment, in this case an infiltration–exfiltration system (IES) consisting of a gravel swale with porous asphalt surface, through hydrological modelling of six rainfall events measured on a highway in Cincinnati (USA). The results showed a compatible removal rate for both the FFT and IES for the six analysed events, consisting of three mass-limit events and three flow-limit events. Particle transport modelling could represent well the behaviour of the events and can be used as a tool to choose between systems, where after setting the particle removal efficiency, other factors can be considered, like cost and system area consumption. This research can be followed up with continuous rainfall simulations and using computational fluid dynamics (CFD) to model IES particle removal.</span></p> ]]> Modelling of Particulate Matter Fate on Urban Highway Stormwater Control Systems mariana marchioni anita raimondi umberto sanfilippo john sansalone stefano mambretti gianfranco becciu doi: 10.2495/CMEM-V9-N1-1-13 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2021 9 1 Article 1 10.2495/CMEM-V9-N1-1-13 https://www.acadlore.com/article/IJCMEM/2021_9_1/CMEM-V9-N1-1-13 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-387-404 The current development of renewable energies has originated a number of new structural typologies that are the physical support of the energy production systems. Photovoltaic energy is a very mature source and it is obtained using rows of panels implemented in a longitudinal grillage. Many studies have been carried out in the past with an aim to improve the capacity to obtain electrical power, but another important issue is the need to guarantee the performance of these industrial facilities under the phenomena induced by the turbulent wind flow, taking into account the fact that they are usually built in wide open spaces. This paper describes an extensive research carried out on two configurations of solar trackers by experimental and computational methods. The former was composed of a number of tests of reduced models of segments of the solar trackers, which were carried out in an aerodynamic wind tunnel. The latter consisted of a series of structural analyses worked out through a finite element model of the full panel subjected to aerodynamic and aeroelastic loads. Several angles of attack of the wind flow and a wide range of wind speeds were included in the study. This approach allowed to clearly evaluate the structural and dynamic performance of both the configurations of solar trackers under the most important wind-induced phenomena such as vortex shedding, torsional divergence, and flutter. The paper relates the phases of the study and informs about the more relevant numerical results obtained in the experiments and the computer analysis. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The current development of renewable energies has originated a number of new structural typologies that are the physical support of the energy production systems. Photovoltaic energy is a very mature source and it is obtained using rows of panels implemented in a longitudinal grillage. Many studies have been carried out in the past with an aim to improve the capacity to obtain electrical power, but another important issue is the need to guarantee the performance of these industrial facilities under the phenomena induced by the turbulent wind flow, taking into account the fact that they are usually built in wide open spaces. This paper describes an extensive research carried out on two configurations of solar trackers by experimental and computational methods. The former was composed of a number of tests of reduced models of segments of the solar trackers, which were carried out in an aerodynamic wind tunnel. The latter consisted of a series of structural analyses worked out through a finite element model of the full panel subjected to aerodynamic and aeroelastic loads. Several angles of attack of the wind flow and a wide range of wind speeds were included in the study. This approach allowed to clearly evaluate the structural and dynamic performance of both the configurations of solar trackers under the most important wind-induced phenomena such as vortex shedding, torsional divergence, and flutter. The paper relates the phases of the study and informs about the more relevant numerical results obtained in the experiments and the computer analysis.</span></p> ]]> Experimental and Computational Studies on the Performance of Solar Trackers under Vortex Shedding, Torsional Divergence, and Flutter j. quintela j. a. jurado c. rapela a. j. álvarez m. roca s. hernández m. cid montoya j. m. lópez a. j. ruiz i. moreno s. jiménez doi: 10.2495/CMEM-V8-N4-387-404 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 387 10.2495/CMEM-V8-N4-387-404 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-387-404 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-367-386 Karst conduit network modelling is particularly difficult because the location of the conduits within an aquifer is often unknown. To address this, many mathematical models of karst aquifers use stochastically simulated conduit networks to try to extract certain geometrical and hydraulic connectivity properties that may prevail within the aquifer. Such idealized representations of a karst aquifer do not adequately represent the positive feedback mechanism that exists between the distribution of hydraulic head and the growth of the solution conduits that determine the geometry and the interconnectedness of the resulting conduit network. In this paper, Poisson surface reconstruction is presented as a simple method for constructing a realistic model of a karst aquifer by simulating the positive feedback mechanism between dissolution and flow. Direct application of the Poisson technique to a tropical karst limestone aquifer of the island of Barbados highlights how the complete conduit geometry and the feedback mechanism of a real aquifer system may be interpolated. The result suggests that applying surface reconstruction to a good calibrated point cloud sampling taken from an aquifer itself is an efficient methodology for generating realistic karstic networks. Additionally, Poisson surface reconstruction replicates an aquifer without directly solving complex hydrogeological and speleological equations and oversimplifying the hydrogeological and geological complexities of a karst environment in the way that hypothesized conduit network models do. As a result, it is believed that this conceptual model provides a utility for characterizing a karst aquifer in terms of the well-established theoretical foundations of the surface reconstruction problem even when the input data is sparse. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Karst conduit network modelling is particularly difficult because the location of the conduits within an aquifer is often unknown. To address this, many mathematical models of karst aquifers use stochastically simulated conduit networks to try to extract certain geometrical and hydraulic connectivity properties that may prevail within the aquifer. Such idealized representations of a karst aquifer do not adequately represent the positive feedback mechanism that exists between the distribution of hydraulic head and the growth of the solution conduits that determine the geometry and the interconnectedness of the resulting conduit network. In this paper, Poisson surface reconstruction is presented as a simple method for constructing a realistic model of a karst aquifer by simulating the positive feedback mechanism between dissolution and flow. Direct application of the Poisson technique to a tropical karst limestone aquifer of the island of Barbados highlights how the complete conduit geometry and the feedback mechanism of a real aquifer system may be interpolated. The result suggests that applying surface reconstruction to a good calibrated point cloud sampling taken from an aquifer itself is an efficient methodology for generating realistic karstic networks. Additionally, Poisson surface reconstruction replicates an aquifer without directly solving complex hydrogeological and speleological equations and oversimplifying the hydrogeological and geological complexities of a karst environment in the way that hypothesized conduit network models do. As a result, it is believed that this conceptual model provides a utility for characterizing a karst aquifer in terms of the well-established theoretical foundations of the surface reconstruction problem even when the input data is sparse.</span></p> ]]> Modelling the Positive Feedback Mechanism of a Karst Aquifer Using Surface Reconstruction kyffin k. bradshaw tane s. ray doi: 10.2495/CMEM-V8-N4-367-386 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 367 10.2495/CMEM-V8-N4-367-386 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-367-386 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-355-366 Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyse and solve problems that involve fluid flows. Today, CFD plays a decisive role in the cycling industry, which affects not only bicycle manufacturers, but also, above all, bicycle component suppliers. In fact, aerodynamic research takes place not only in the cyclist’s best riding position, but also in the design of the components and frames that make up a racing bike. The frame design is essential both for its ability to oppose the aerodynamic resistance and to adapt the cyclist to the best geometry. Among the multiple outlets of the method, the simulation of external aerodynamic flows shows a fundamental importance for the understanding of the role played by the design of the bicycle. Once a numerical analysis was set correctly, it was then possible to predict with good reliability the fluid dynamic behaviour of an entire structure without the need to use experimental approaches every time. The main aim of this study consists of the validation of a numerical model through experiments conducted on a scale model of a latest generation cycling frame in an open chamber wind tunnel by means of the Particle Image Velocimetry (PIV) technique. In particular, the scale model used was investigated in two specific regions. The experimental data were compared to numerical results obtained employing turbulence model, and the validated numerical tool was subsequently applied to estimate the drag coefficient of two different types of handlebars (aerodynamic and standard versions). The standard cylindrical handlebar folds were replaced by products made of composite and with the most innovative and modern shapes, able to significantly reduce the aerodynamic resistance values. Indeed, in the design phase, the measurement of the drag coefficient is a fundamental procedure. As expected, the presence of aerodynamic profiles generated a low drag coefficient, one of the most important aerodynamic conditions. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyse and solve problems that involve fluid flows. Today, CFD plays a decisive role in the cycling industry, which affects not only bicycle manufacturers, but also, above all, bicycle component suppliers. In fact, aerodynamic research takes place not only in the cyclist’s best riding position, but also in the design of the components and frames that make up a racing bike. The frame design is essential both for its ability to oppose the aerodynamic resistance and to adapt the cyclist to the best geometry. Among the multiple outlets of the method, the simulation of external aerodynamic flows shows a fundamental importance for the understanding of the role played by the design of the bicycle. Once a numerical analysis was set correctly, it was then possible to predict with good reliability the fluid dynamic behaviour of an entire structure without the need to use experimental approaches every time. The main aim of this study consists of the validation of a numerical model through experiments conducted on a scale model of a latest generation cycling frame in an open chamber wind tunnel by means of the Particle Image Velocimetry (PIV) technique. In particular, the scale model used was investigated in two specific regions. The experimental data were compared to numerical results obtained employing turbulence model, and the validated numerical tool was subsequently applied to estimate the drag coefficient of two different types of handlebars (aerodynamic and standard versions). The standard cylindrical handlebar folds were replaced by products made of composite and with the most innovative and modern shapes, able to significantly reduce the aerodynamic resistance values. Indeed, in the design phase, the measurement of the drag coefficient is a fundamental procedure. As expected, the presence of aerodynamic profiles generated a low drag coefficient, one of the most important aerodynamic conditions.</span></p> ]]> Numerical and Experimental Analysis of Turbulent Fluid Flow around Latest Generation Cycling Frame m. castellini m. barbanera m. scungio f. arpino doi: 10.2495/CMEM-V8-N4-355-366 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 355 10.2495/CMEM-V8-N4-355-366 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-355-366 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-341-354 In this paper, we present the hydrodynamic mechanisms which occur between a low-hypersonic shock wave and a millimetric water droplet. To do so, two numerical models, based respectively on the Volume of Fluid (VOF) and Diffuse Interfaces (DI) approaches, are developed. The goal is to compare the results obtained with the models in order to evaluate which is the most accurate to describe the evolution of the physical phenomena. The studied Mach number and initial droplet diameter are 4.25 and 1.135 mm, respectively. Each model allows the compressible Euler equations to be solved in a 2D-axi-symmetric configuration. The evolution of both air and liquid phases is modelled by a stiffened gas equation of state. For qualitative validation, the numerical results are compared to experimental data recently presented in the literature. In this work, the authors used a shock tube test facility and a shadowgraph visualization technique to observe the phenomenology over a long time. Their investigation shows that the droplet deformation, detached bow shock and recompression waves are well captured by the two models until a Rayleigh dimensionless time of 1.5. Beyond this critical time, and up to 3, some differences appear between the two numerical approaches, especially on the droplet deformation. Globally, the droplet deformation is better described with the VOF model, while the DI model appears to be more accurate when it comes to the evaluation of the position of the bow shock. In the discussion section, some ideas are proposed to improve the models. <![CDATA[ <p>In this paper, we present the hydrodynamic mechanisms which occur between a low-hypersonic shock wave and a millimetric water droplet. To do so, two numerical models, based respectively on the Volume of Fluid (VOF) and Diffuse Interfaces (DI) approaches, are developed. The goal is to compare the results obtained with the models in order to evaluate which is the most accurate to describe the evolution of the physical phenomena. The studied Mach number and initial droplet diameter are 4.25 and 1.135 mm, respectively. Each model allows the compressible Euler equations to be solved in a 2D-axi-symmetric configuration. The evolution of both air and liquid phases is modelled by a stiffened gas equation of state. For qualitative validation, the numerical results are compared to experimental data recently presented in the literature. In this work, the authors used a shock tube test facility and a shadowgraph visualization technique to observe the phenomenology over a long time. Their investigation shows that the droplet deformation, detached bow shock and recompression waves are well captured by the two models until a Rayleigh dimensionless time of 1.5. Beyond this critical time, and up to 3, some differences appear between the two numerical approaches, especially on the droplet deformation. Globally, the droplet deformation is better described with the VOF model, while the DI model appears to be more accurate when it comes to the evaluation of the position of the bow shock. In the discussion section, some ideas are proposed to improve the models.</p> ]]> Numerical Investigation of the Interactions between a Low-Hypersonic Shock Wave and A Water Droplet: VOF and DI Methods Comparison gwenc’hlan tymen david hebert jean-luc rullier thibault bridel-bertomeu isabelle bertron simon peluchon emilien lescoute florent virot doi: 10.2495/CMEM-V8-N4-341-354 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 341 10.2495/CMEM-V8-N4-341-354 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-341-354 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-326-340 Most of the water pipe infrastructure is outdated; therefore, frequent maintenance and repair works are required. To speed up the rehabilitation work and to have a more sustainable and efficient approach, trenchless methodologies have been developed in the last decades. One of the most cost-effective trenchless methods is the so-called Cured in Place Pipeline (CIPP) method, in which a resin-impregnated liner is pulled or inverted inside the host pipe and, when cured, it restores the old pipe structural and mechanical integrity. The aim of this study is to analyse the effects of the presence of a CIPP liner in a deteriorated pipe during unsteady flow for compressible fluids. In particular, the paper deals with a new formulation to compute the celerity of the wave which produces the overpressures, when the pipe wall is composed of both the host (old) pipe and the new liner, whose thickness depends on the required mechanical characteristics. The problem is strictly dependent on the mechanical properties of the liner. In order to obtain the new formula for celerity, the linear elastic problem for multi-layered pipes has been solved. The theoretical results have been validated by performing numerical simulation analysis using a Boundary Element model, with the software BEASY™. The resulting circumferential strain is integrated in the continuity equation, deriving the new formula to compute the wave celerity. The values of the celerity are dependent on the thickness and on the elastic properties of the liner. The behaviour of several combinations of thickness of the liner and Young’s modulus values has been studied and the results have been critically shown in the paper. <![CDATA[ <p>Most of the water pipe infrastructure is outdated; therefore, frequent maintenance and repair works are required. To speed up the rehabilitation work and to have a more sustainable and efficient approach, trenchless methodologies have been developed in the last decades. One of the most cost-effective trenchless methods is the so-called Cured in Place Pipeline (CIPP) method, in which a resin-impregnated liner is pulled or inverted inside the host pipe and, when cured, it restores the old pipe structural and mechanical integrity. The aim of this study is to analyse the effects of the presence of a CIPP liner in a deteriorated pipe during unsteady flow for compressible fluids. In particular, the paper deals with a new formulation to compute the celerity of the wave which produces the overpressures, when the pipe wall is composed of both the host (old) pipe and the new liner, whose thickness depends on the required mechanical characteristics. The problem is strictly dependent on the mechanical properties of the liner. In order to obtain the new formula for celerity, the linear elastic problem for multi-layered pipes has been solved. The theoretical results have been validated by performing numerical simulation analysis using a Boundary Element model, with the software BEASY™. The resulting circumferential strain is integrated in the continuity equation, deriving the new formula to compute the wave celerity. The values of the celerity are dependent on the thickness and on the elastic properties of the liner. The behaviour of several combinations of thickness of the liner and Young’s modulus values has been studied and the results have been critically shown in the paper.</p> ]]> Wave Celerity in Hydraulic Transients Computation for Cipp-Rehabilitated Pipes f. evangelista s. hernandez s. mambretti d. parola doi: 10.2495/CMEM-V8-N4-326-340 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 326 10.2495/CMEM-V8-N4-326-340 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-326-340 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-316-325 Motivated by the fact that Chile is one of the most seismically active countries in the world (located over the ‘Pacific Ring of Fire’), we define a methodology for estimating the cost of housing reconstruction by modelling the occurrence of natural disasters as a Markov chain. Specifically, the states of the chain correspond to the different possible conditions of the housing infrastructure and the transition probabilities represent the possibility of change from one condition to another once the disaster has occurred. We prove that for the case of the 2010 Chilean earthquake, the matrix representing the process admits a stationary state vector. Using this vector, which we interpreted as the portion of time that the chain spends in each state in the long term, we define a cost function associated with total reconstruction. If this cost function is continuous, then this methodology allows policymakers to make decisions when facing the trade-off between current partial reconstruction and future total reconstruction. <![CDATA[ <p>Motivated by the fact that Chile is one of the most seismically active countries in the world (located over the ‘Pacific Ring of Fire’), we define a methodology for estimating the cost of housing reconstruction by modelling the occurrence of natural disasters as a Markov chain. Specifically, the states of the chain correspond to the different possible conditions of the housing infrastructure and the transition probabilities represent the possibility of change from one condition to another once the disaster has occurred. We prove that for the case of the 2010 Chilean earthquake, the matrix representing the process admits a stationary state vector. Using this vector, which we interpreted as the portion of time that the chain spends in each state in the long term, we define a cost function associated with total reconstruction. If this cost function is continuous, then this methodology allows policymakers to make decisions when facing the trade-off between current partial reconstruction and future total reconstruction.</p> ]]> A Markov Chain Approach to Model Reconstruction valeria scapini eduardo zuñiga doi: 10.2495/CMEM-V8-N4-316-325 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 316 10.2495/CMEM-V8-N4-316-325 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-316-325 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-289-315 In this paper, we introduce a new node positioning algorithm (NPA) for determining suitable locations of the computational nodes that are a typical feature of mesh reduction numerical methods for partial differential equations – specifically, the Complex Variable Boundary Element Method (CVBEM). The novelty of the introduced NPA is a ‘position refinement’ procedure, which facilitates the relocation of nodes that are already being used in the current CVBEM model when such relocation reduces the maximum error of the associated CVBEM model. The results of the new NPA (referred to as NPA2) are compared to the results obtained using the recent NPA described in [1] (referred to as NPA1). We compare NPA1 and NPA2 by modeling two example Dirichlet boundary value problems that have been selected due to having regions of extreme curvature in the analytic flow regime that are difficult to model computationally. Consequently, these problems serve as good benchmark problems for testing the efficacy of the current and future NPAs. Our empirical findings suggest that the use of NPA2 can reduce the maximum error of the associated CVBEM model by several orders of magnitude compared to the corresponding result obtained using NPA1. <![CDATA[ <p>In this paper, we introduce a new node positioning algorithm (NPA) for determining suitable locations of the computational nodes that are a typical feature of mesh reduction numerical methods for partial differential equations – specifically, the Complex Variable Boundary Element Method (CVBEM). The novelty of the introduced NPA is a ‘position refinement’ procedure, which facilitates the relocation of nodes that are already being used in the current CVBEM model when such relocation reduces the maximum error of the associated CVBEM model. The results of the new NPA (referred to as NPA2) are compared to the results obtained using the recent NPA described in [1] (referred to as NPA1). We compare NPA1 and NPA2 by modeling two example Dirichlet boundary value problems that have been selected due to having regions of extreme curvature in the analytic flow regime that are difficult to model computationally. Consequently, these problems serve as good benchmark problems for testing the efficacy of the current and future NPAs. Our empirical findings suggest that the use of NPA2 can reduce the maximum error of the associated CVBEM model by several orders of magnitude compared to the corresponding result obtained using NPA1.</p> ]]> Comparison of Two Algorithms for Locating Computational Nodes in the Complex Variable Boundary Element Method (CVBEM) bryce d. wilkins theodore v. hromadka ii jackson mcinvale doi: 10.2495/CMEM-V8-N4-289-315 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 4 Article 289 10.2495/CMEM-V8-N4-289-315 https://www.acadlore.com/article/IJCMEM/2020_8_4/CMEM-V8-N4-289-315 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-270-280 As part of an optimized maintenance strategy, track monitoring should provide information to predict track faults at an early stage. This is possible by continuously measuring the axle box accelerations and using artificial intelligence, which can detect short wave defects on the railway track with high accuracy. Such short wave defects include rail breaks, cracks, and local irregularities (mud spots). These types of faults can reduce the track quality in a short period of time.Different track irregularities were simulated in a track-vehicle scale model to generate acceleration data for typical track defects. The main focus of the current research is on recognition of local irregularities in the track-vehicle scale model. To implement the artificial intelligence, a Recurrent Neural Network is used to show the procedure and the results of recognition of track defects. The architecture and components of the neural network used are described in detail in this article. At the end of the article, a table summarizing the results of the different models trained for detecting the local irregularities in the track-vehicle scale model is presented. <![CDATA[ <p>As part of an optimized maintenance strategy, track monitoring should provide information to predict track faults at an early stage. This is possible by continuously measuring the axle box accelerations and using artificial intelligence, which can detect short wave defects on the railway track with high accuracy. Such short wave defects include rail breaks, cracks, and local irregularities (mud spots). These types of faults can reduce the track quality in a short period of time.</p><p style="text-align: justify">Different track irregularities were simulated in a track-vehicle scale model to generate acceleration data for typical track defects. The main focus of the current research is on recognition of local irregularities in the track-vehicle scale model. To implement the artificial intelligence, a Recurrent Neural Network is used to show the procedure and the results of recognition of track defects. The architecture and components of the neural network used are described in detail in this article. At the end of the article, a table summarizing the results of the different models trained for detecting the local irregularities in the track-vehicle scale model is presented.</p> ]]> Recognition of Track Defects through Measured Acceleration Using A Recurrent Neural Network sebastian bahamon-blanco sebastian rapp yi zhang jing liu ullrich martin doi: 10.2495/CMEM-V8-N3-270-280 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 270 10.2495/CMEM-V8-N3-270-280 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-270-280 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-252-269 This article introduces an innovative technique that integrates a genetic algorithm (GA)-based digital image correlation with laser speckle photography for the estimation of surface displacements in struc- tures. The images (before and after deformation) are digitized using a digital camera, and the grayscale intensity matrices are read and processed by an image processing algorithm. The two matrices of the images are then inputted into GA-based optimizer that utilizes an advanced cross-correlation fitness function to approximate the surface displacements. Furthermore, the surface strains are computed from the displacements using radial basis function differentiation and interpolation. The computed displacements are compared with simulated results obtained by the boundary element method. Close agreement between the two results proves the validity of the developed noncontact technique for accurately estimating surface displacements and strains. These experimentally estimated displacements can further be used in an inverse technique to detect and characterize subsurface cavities in structures. <![CDATA[ <p>This article introduces an innovative technique that integrates a genetic algorithm (GA)-based digital image correlation with laser speckle photography for the estimation of surface displacements in struc- tures. The images (before and after deformation) are digitized using a digital camera, and the grayscale intensity matrices are read and processed by an image processing algorithm. The two matrices of the images are then inputted into GA-based optimizer that utilizes an advanced cross-correlation fitness function to approximate the surface displacements. Furthermore, the surface strains are computed from the displacements using radial basis function differentiation and interpolation. The computed displacements are compared with simulated results obtained by the boundary element method. Close agreement between the two results proves the validity of the developed noncontact technique for accurately estimating surface displacements and strains. These experimentally estimated displacements can further be used in an inverse technique to detect and characterize subsurface cavities in structures.</p> ]]> Ga-Based Laser Speckle Pattern Digital Image Correlation Method for Surface Strain Measurements arka das eduardo divo faisal moslehy alain kassab doi: 10.2495/CMEM-V8-N3-252-269 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 252 10.2495/CMEM-V8-N3-252-269 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-252-269 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-243-251 Cor-Ten is a weathering steel exploited in the last decade for several applications such as bridges, artworks, building facades, etc. Besides a good strength, it naturally oxides creating a protective layer. This oxide, unlike rust, has the same specific volume of the pure metal. This characteristic allows over- coming the need of protecting treatments like galvanization, etc.While its properties promote its exploitation in civil applications, there are also some examples of application where safety is a fundamental requirement. In the northern part of Italy, Cor-Ten is used for safety barriers (guard rails) along the highways. It is, therefore, fundamental to know the ductile behavior of this material, for which few data are available in literature.Quasi-static experimental tensile tests have been performed on eight samples having different shapes. Numerical simulations carried out with an open-source code (Code_Aster) reproduced the experimental setup. In this way, it was possible to calculate the stress state and the plastic strain at failure needed for the calibration of the ductile damage model. The material model is based on classical incremental plastic response with isotropic hardening and phenomenological concept of damage. <![CDATA[ <p>Cor-Ten is a weathering steel exploited in the last decade for several applications such as bridges, artworks, building facades, etc. Besides a good strength, it naturally oxides creating a protective layer. This oxide, unlike rust, has the same specific volume of the pure metal. This characteristic allows over- coming the need of protecting treatments like galvanization, etc.</p><p style="text-align: justify">While its properties promote its exploitation in civil applications, there are also some examples of application where safety is a fundamental requirement. In the northern part of Italy, Cor-Ten is used for safety barriers (guard rails) along the highways. It is, therefore, fundamental to know the ductile behavior of this material, for which few data are available in literature.</p><p style="text-align: justify">Quasi-static experimental tensile tests have been performed on eight samples having different shapes. Numerical simulations carried out with an open-source code (Code_Aster) reproduced the experimental setup. In this way, it was possible to calculate the stress state and the plastic strain at failure needed for the calibration of the ductile damage model. The material model is based on classical incremental plastic response with isotropic hardening and phenomenological concept of damage.</p> ]]> Fracture Locus of a Cor-Ten Weathering Steel: Experimental–Numerical Calibration f. concli l. maccioni doi: 10.2495/CMEM-V8-N3-243-251 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 243 10.2495/CMEM-V8-N3-243-251 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-243-251 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-233-242 Fibre-reinforced polymer (FRP) as a protective hardening system has now become more commonly used in enhancing the capacity of reinforced concrete (RC) elements against blast loadings. Wrapping RC columns with FRP, depending on the wrapping configuration, will result in additional axial, moment and shear capacity. The FRP also prevents debris from being blown off and serves as a catcher system which minimises the possible cause of injuries/casualties in the event of blast. While analytical models built into popular finite element modelling (FEM) software are widely used to simulate and analyse the effects of a blast load to a structural element, little work has been carried out to validate the results of such analysis through experimental means. This paper examines the effect of blast loadings onto RC columns wrapped with FRP. The behaviour of the FRP-wrapped RC columns subjected to blast loading is simulated using finite element analysis. Results from the finite element simulation are compared to the corresponding wrapping configuration from actual experimental results. The comparison validates the reliability of using finite element analysis in predicting the response of FRP-wrapped RC columns subjected to blast loading. <![CDATA[ <p>Fibre-reinforced polymer (FRP) as a protective hardening system has now become more commonly used in enhancing the capacity of reinforced concrete (RC) elements against blast loadings. Wrapping RC columns with FRP, depending on the wrapping configuration, will result in additional axial, moment and shear capacity. The FRP also prevents debris from being blown off and serves as a catcher system which minimises the possible cause of injuries/casualties in the event of blast. While analytical models built into popular finite element modelling (FEM) software are widely used to simulate and analyse the effects of a blast load to a structural element, little work has been carried out to validate the results of such analysis through experimental means. This paper examines the effect of blast loadings onto RC columns wrapped with FRP. The behaviour of the FRP-wrapped RC columns subjected to blast loading is simulated using finite element analysis. Results from the finite element simulation are compared to the corresponding wrapping configuration from actual experimental results. The comparison validates the reliability of using finite element analysis in predicting the response of FRP-wrapped RC columns subjected to blast loading.</p> ]]> A Comparison of Finite Element Simulation and Experimental Results from Reinforced Concrete Columns Wrapped with Fibre-Reinforced Polymer Subjected to Blast Loading jeslin quek liu chunlin john vincent musngi pavithra buddika malalasekara doi: 10.2495/CMEM-V8-N3-233-242 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 233 10.2495/CMEM-V8-N3-233-242 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-233-242 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-220-232 In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability.The so-called ‘thermal limit’, i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past.The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses.The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution.Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios. <![CDATA[ <p>In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability.</p><p style="text-align: justify">The so-called ‘thermal limit’, i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past.</p><p style="text-align: justify">The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses.</p><p style="text-align: justify">The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution.</p><p style="text-align: justify">Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios.</p> ]]> Development of a Computational Fluid Dynamics Simulation Tool for Lubrication Studies on Cycloidal Gear Sets f. concli l. maccioni c. gorla doi: 10.2495/CMEM-V8-N3-220-232 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 220 10.2495/CMEM-V8-N3-220-232 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-220-232 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-208-219 The central idea of this paper is that computer mathematics is not identical to ideal mathematics because computer numbers only have finite precision. All functions, especially the positive definite transcendental functions, are truncated and the expansion coefficients have finite precision and all branching operations require time to complete. Of all the known methods used to obtain numerical solutions to integral and partial differential equations, the global continuously differential radial basis functions (RBFs) that are implemented on computers closely resemble many aspects of ideal mathematics. The global RBFs have the attributes required to obtain very accurate numerical results for a variety of partial differential and integral equations with smooth solutions. Without the need for extremely fine discretization, the global RBFs have their spline properties and exponential convergence rates. The resulting system of full equations can be executed very rapidly on graphical processing units and field-programmable gate arrays because, with full systems, there is no branching and full systems solvers are very highly vectorized, optimizing the usage of very fast processors. <![CDATA[ <p>The central idea of this paper is that computer mathematics is not identical to ideal mathematics because computer numbers only have finite precision. All functions, especially the positive definite transcendental functions, are truncated and the expansion coefficients have finite precision and all branching operations require time to complete. Of all the known methods used to obtain numerical solutions to integral and partial differential equations, the global continuously differential radial basis functions (RBFs) that are implemented on computers closely resemble many aspects of ideal mathematics. The global RBFs have the attributes required to obtain very accurate numerical results for a variety of partial differential and integral equations with smooth solutions. Without the need for extremely fine discretization, the global RBFs have their spline properties and exponential convergence rates. The resulting system of full equations can be executed very rapidly on graphical processing units and field-programmable gate arrays because, with full systems, there is no branching and full systems solvers are very highly vectorized, optimizing the usage of very fast processors.</p> ]]> Fully and Sparsely Supported Radial Basis Functions e. j. kansa p. holoborodko doi: 10.2495/CMEM-V8-N3-208-219 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 208 10.2495/CMEM-V8-N3-208-219 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-208-219 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-195-207 The present study is focused on the application of phase-field modelling techniques to fracture simula­tion in laminated glass samples under bending. A damage model using a phase-field formulation of fracture is introduced and applied to three-layer laminated glass samples. The identification of material parameters of polymer foils and glass is also provided, based on a combined experimental and numeri­cal analysis. Specifically, the results of small scale testing and the calibration of the constitutive models of polymer interlayers are discussed in connection to ethylen-vinyl acetate and polyvinyl butyral foils. The statistical data obtained by the evaluation of tensile strength of glass samples are used for the formulation of the tensile stress criterion. Therefore, a generalisation of the energetic formulation of phase-field models towards the stress-based criterion is employed here to simulate the fracture behav­iour of laminated glass. The experimentally measured data are compared with the numerically derived response using the extreme values of tensile strength obtained. Then, the fracture response is analysed for one sample to support the proposed computational model and material parameters. <![CDATA[ <p>The present study is focused on the application of phase-field modelling techniques to fracture simula­tion in laminated glass samples under bending. A damage model using a phase-field formulation of fracture is introduced and applied to three-layer laminated glass samples. The identification of material parameters of polymer foils and glass is also provided, based on a combined experimental and numeri­cal analysis. Specifically, the results of small scale testing and the calibration of the constitutive models of polymer interlayers are discussed in connection to ethylen-vinyl acetate and polyvinyl butyral foils. The statistical data obtained by the evaluation of tensile strength of glass samples are used for the formulation of the tensile stress criterion. Therefore, a generalisation of the energetic formulation of phase-field models towards the stress-based criterion is employed here to simulate the fracture behav­iour of laminated glass. The experimentally measured data are compared with the numerically derived response using the extreme values of tensile strength obtained. Then, the fracture response is analysed for one sample to support the proposed computational model and material parameters.</p> ]]> On Pre- and Post-Fracture Behaviour of Laminated Glass Under Bending alena zemanova jaroslav schmidt michal sejnoha doi: 10.2495/CMEM-V8-N3-195-207 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 3 Article 195 10.2495/CMEM-V8-N3-195-207 https://www.acadlore.com/article/IJCMEM/2020_8_3/CMEM-V8-N3-195-207 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-99-110 Mechanical and fire loading play together with geometric and material properties of glued laminated timber beams a decisive role in theoretical investigation into the time-dependent fire resistance of these elements. This is a multidisciplinary problem including heat conduction, water evaporation, internal gas pressure evolution, pyrolysis, volume change, etc. If properly calibrated, such complex models should allow us to forecast the evolution and shape of the charred or zero strength layer. It is doubtless that the calibration and validation steps require experiments. In particular, the results of large-scale fire experiment are discussed in this contribution focusing on the influence of fire intensity and duration on the temperature and the charred layer evolution. The influence of fire on stiffness and strength will also be addressed through the results of Pilodyn measurements of wood elastic modulus and three-point bending tests of original and fire-exposed beams. <![CDATA[ <p>Mechanical and fire loading play together with geometric and material properties of glued laminated timber beams a decisive role in theoretical investigation into the time-dependent fire resistance of these elements. This is a multidisciplinary problem including heat conduction, water evaporation, internal gas pressure evolution, pyrolysis, volume change, etc. If properly calibrated, such complex models should allow us to forecast the evolution and shape of the charred or zero strength layer. It is doubtless that the calibration and validation steps require experiments. In particular, the results of large-scale fire experiment are discussed in this contribution focusing on the influence of fire intensity and duration on the temperature and the charred layer evolution. The influence of fire on stiffness and strength will also be addressed through the results of Pilodyn measurements of wood elastic modulus and three-point bending tests of original and fire-exposed beams.</p> ]]> Experimental Investigation of Fire Resistance of Glt Beams l. kucíková t. janda m. šejnoha j. sykora doi: 10.2495/CMEM-V8-N2-99-110 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 99 10.2495/CMEM-V8-N2-99-110 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-99-110 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-175-185 Differential pressure measurements are commonly applied in industrial conditions, due to the fact that measurements that apply them are simple and offer relatively high accuracy. In gas installations, the liquid is often condensed in the form of a droplet present in the gas. When the liquid is transported along with gas, this leads to a significant increase in the differential pressure and incorrect indications of measuring equipment. In addition, the presence of the liquid phase in the flow leads to interference and pressure pulsations. This article reports the results of a study concerned with finding a solution that can offer a way to correct the over-reading of the measured gas flow rate depending on the mass fraction of the liquid in it. The standard orifice was subjected to an experimental study, and then on the basis of this analysis, an algorithm for a computer over-reading model was developed. The experiment involved the measurement of airflow with a small amount of dispersed water in the form of droplets. The results were compared with other correction methods familiar from the literature. <![CDATA[ <p>Differential pressure measurements are commonly applied in industrial conditions, due to the fact that measurements that apply them are simple and offer relatively high accuracy. In gas installations, the liquid is often condensed in the form of a droplet present in the gas. When the liquid is transported along with gas, this leads to a significant increase in the differential pressure and incorrect indications of measuring equipment. In addition, the presence of the liquid phase in the flow leads to interference and pressure pulsations. This article reports the results of a study concerned with finding a solution that can offer a way to correct the over-reading of the measured gas flow rate depending on the mass fraction of the liquid in it. The standard orifice was subjected to an experimental study, and then on the basis of this analysis, an algorithm for a computer over-reading model was developed. The experiment involved the measurement of airflow with a small amount of dispersed water in the form of droplets. The results were compared with other correction methods familiar from the literature.</p> ]]> Correction of Wet Gas Flow Measurements Applying Standard Orifice barbara tomaszewska-wach mariusz rzasa doi: 10.2495/CMEM-V8-N2-175-185 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 175 10.2495/CMEM-V8-N2-175-185 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-175-185 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-162-174 In Europe many buildings and machinery in industrial sites are recognised as cultural heritage. These structures, often made from various types of irons or historic steels, have been for decades or centuries exposed to aggressive atmospheric environments and suffered from corrosion attack. The contribution discusses corrosion rates, the effects of corrosion on structural reliability, and the efficiency of surface treatments. The model for corrosion rates of historic metals cannot be based on the degradation model for mild steels even though specific features of historic alloys such as increased content of carbon and different chemical composition would be taken into account. Realistic estimates of corrosion rates need additionally account for different micro-structure with inputs and different surface properties of historic alloys. This is why the presented model is based on a limited experimental data, considering the corrosivity of environment. The model assumes no corrosion during first seven years of service life and the same type of regression function for the progress period as is provided in ISO 9224 for mild steels and other metals. The effects of repeated applications of paintings are discussed. Four principal strategies to the corrosion protection of industrial heritage structures include ‘leave as it is’, apply temporary protection to reduce degradation progress, apply long term protection, or undertake a complex restoration with replacement of damaged elements. Numerical example indicates that corrosion is normally insignificant for load-bearing iron structures, but may lead to severe problems for thin secondary structural and non-structural members such as railing or decorative elements. The proposed model estimates degradation progress in a mid-term perspective and supports decisions on maintenance of industrial heritage structures. <![CDATA[ <p>In Europe many buildings and machinery in industrial sites are recognised as cultural heritage. These structures, often made from various types of irons or historic steels, have been for decades or centuries exposed to aggressive atmospheric environments and suffered from corrosion attack. The contribution discusses corrosion rates, the effects of corrosion on structural reliability, and the efficiency of surface treatments. The model for corrosion rates of historic metals cannot be based on the degradation model for mild steels even though specific features of historic alloys such as increased content of carbon and different chemical composition would be taken into account. Realistic estimates of corrosion rates need additionally account for different micro-structure with inputs and different surface properties of historic alloys. This is why the presented model is based on a limited experimental data, considering the corrosivity of environment. The model assumes no corrosion during first seven years of service life and the same type of regression function for the progress period as is provided in ISO 9224 for mild steels and other metals. The effects of repeated applications of paintings are discussed. Four principal strategies to the corrosion protection of industrial heritage structures include ‘leave as it is’, apply temporary protection to reduce degradation progress, apply long term protection, or undertake a complex restoration with replacement of damaged elements. Numerical example indicates that corrosion is normally insignificant for load-bearing iron structures, but may lead to severe problems for thin secondary structural and non-structural members such as railing or decorative elements. The proposed model estimates degradation progress in a mid-term perspective and supports decisions on maintenance of industrial heritage structures.</p> ]]> Corrosion of Historic Grey Cast Irons: Indicative Rates, Significance, and Protection miroslav sykora katerina kreislova petr pokorny doi: 10.2495/CMEM-V8-N2-162-174 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 162 10.2495/CMEM-V8-N2-162-174 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-162-174 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-148-161 On the basis of the fundamental system, which includes equations of continuity, momentum, and substance transfer with a linearized equation of state, methods of experimental and numerical study are developed for visualizing the flow perturbation fields generated by uniform horizontal movement of a vertical plate in a stratified medium. The stratified flows were visualized in the laboratory tank by the high-sensitive and high-resolution Schlieren instrument IAB-458 at the stand ‘Laboratory Mobile Tank’ of the Unique Research Facility ‘HPC IPMech RAS’ and numerically calculated within the frame of the open source CFD utility OpenFOAM using computing resources of cluster systems and supercomputers. Both the computation results and the laboratory visualization data show that a vertical plate uniformly moving in a stratified fluid generates flow patterns which contain complex systems of internal waves, including upstream, attached and short ones, and thin interfaces, such as ligaments, formed due to the combined influence of the stratification and dissipation effects. Increase in the velocity of the plate movement leads to an essential restructuring of the wake flow past the plate, where typical vortex elements, such as vortex dipoles and ‘vortex bubbles’, are formed in the divergence zones of the phase surfaces of internal waves. All the flow structural components evolve and actively interact with each other and with the free stream. The observation and calculation results are in a good qualitative and quantitative agreement with each other. <![CDATA[ <p>On the basis of the fundamental system, which includes equations of continuity, momentum, and substance transfer with a linearized equation of state, methods of experimental and numerical study are developed for visualizing the flow perturbation fields generated by uniform horizontal movement of a vertical plate in a stratified medium. The stratified flows were visualized in the laboratory tank by the high-sensitive and high-resolution Schlieren instrument IAB-458 at the stand ‘Laboratory Mobile Tank’ of the Unique Research Facility ‘HPC IPMech RAS’ and numerically calculated within the frame of the open source CFD utility OpenFOAM using computing resources of cluster systems and supercomputers. Both the computation results and the laboratory visualization data show that a vertical plate uniformly moving in a stratified fluid generates flow patterns which contain complex systems of internal waves, including upstream, attached and short ones, and thin interfaces, such as ligaments, formed due to the combined influence of the stratification and dissipation effects. Increase in the velocity of the plate movement leads to an essential restructuring of the wake flow past the plate, where typical vortex elements, such as vortex dipoles and ‘vortex bubbles’, are formed in the divergence zones of the phase surfaces of internal waves. All the flow structural components evolve and actively interact with each other and with the free stream. The observation and calculation results are in a good qualitative and quantitative agreement with each other.</p> ]]> Visualization of Stratified Flows Around a Vertical Plate: Laborato Ry Experiment and Numerical Simulation yuli chashechkin yaroslav zagumennyi doi: 10.2495/CMEM-V8-N2-148-161 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 148 10.2495/CMEM-V8-N2-148-161 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-148-161 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-135-147 In recent times, air pollution in Peru is attracting the attention of the population and the government as well, who finally makes the policies that help us to preserve good air quality. In this research, we used the chemical-meteorological model Weather Research and Forecasting coupled with Chemical (WRF-Chem v3.8) to predict pollution scenarios. We studied and analyzed three 2017 months of summer (January, February and March) and three months of winter (July, August and September) to evaluate and forecast two pollutants concentration, sulfur dioxide (SO2) and nitrogen dioxide (NO2) over the city of Lima. We also considered the meteorological variables such as the wind speed and its direction, average temperature, relative humidity and atmospheric pressure. Besides, we used fixed industrial sources inventory as emission data and the Global Forecast System (GFS) as border data for the meteorological components. Within the WRF-Chem model, we implemented the Grell-Freitas parameterization of convection to represent the clouds; we used RRTMG for the shortwave/longwave radiation scheme, and the Monin-Obukhov for the processes in the surface layer, among others. On the other hand, for the gas phase chemistry, we used the RADM2 scheme, for the aerosol module we utilized the MADE-SORGAM, and finally, we employed the Fast-j photolysis scheme. We finally compared the results with the data provided by the ten monitoring stations that belong to the National Service of Meteorology and Hydrology (SENAMHI) which are located in strategic zones in Lima. Lastly, we showed that the variables studied are within the environmental quality standard authorized by the Ministry of the Environment, and we also demonstrated that the simulations given by the model are, in general, overlapping the values measured experimentally in all of the monitoring stations evaluated. <![CDATA[ <p>In recent times, air pollution in Peru is attracting the attention of the population and the government as well, who finally makes the policies that help us to preserve good air quality. In this research, we used the chemical-meteorological model Weather Research and Forecasting coupled with Chemical (WRF-Chem v3.8) to predict pollution scenarios. We studied and analyzed three 2017 months of summer (January, February and March) and three months of winter (July, August and September) to evaluate and forecast two pollutants concentration, sulfur dioxide (SO<em>2</em>) and nitrogen dioxide (NO<em>2</em>) over the city of Lima. We also considered the meteorological variables such as the wind speed and its direction, average temperature, relative humidity and atmospheric pressure. Besides, we used fixed industrial sources inventory as emission data and the Global Forecast System (GFS) as border data for the meteorological components. Within the WRF-Chem model, we implemented the Grell-Freitas parameterization of convection to represent the clouds; we used RRTMG for the shortwave/longwave radiation scheme, and the Monin-Obukhov for the processes in the surface layer, among others. On the other hand, for the gas phase chemistry, we used the RADM2 scheme, for the aerosol module we utilized the MADE-SORGAM, and finally, we employed the Fast-j photolysis scheme. We finally compared the results with the data provided by the ten monitoring stations that belong to the National Service of Meteorology and Hydrology (SENAMHI) which are located in strategic zones in Lima. Lastly, we showed that the variables studied are within the environmental quality standard authorized by the Ministry of the Environment, and we also demonstrated that the simulations given by the model are, in general, overlapping the values measured experimentally in all of the monitoring stations evaluated.</p> ]]> SO2 And NO2 Simulation and Validation in Metropolitan Lima Using WRF-Chem Model ana luna hector navarro aldo moya doi: 10.2495/CMEM-V8-N2-135-147 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 135 10.2495/CMEM-V8-N2-135-147 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-135-147 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-123-134 In multiphase fluid flow, the formation of dispersed patterns, where one of the phases is completely dispersed in the other (continuous medium) is common, for example, in crude oil extraction, during the transport of water/oil mixture. In this work, experimental and numerical studies were carried out for the flow of an oil/water mixture in a horizontal pipe, the dispersed liquid being a paraffin (oil with density 843 kg m−3 and viscosity 0.025 Pa s) and the continuous medium a water solution doped with NaCl (1000 μS. cm−1). The tests were made for oil concentrations of 0.01, 0.13 and 0.22 v/v and velocities between 0.9 and 2.6 ms−1 of the mixture. Experimental work was performed in a pilot rig equipped with an electrical impedance tomography (EIT) system. Information on pressure drop, EIT maps, volumetric concentrations in the vertical diameter of the pipe and flow images were obtained. Simulations were performed in 2-dimensional geometry using the Eulerian–Eulerian approach and the k-ε model for turbulence modelling. The model was implemented in a computational fluid dynamics platform with the programme COMSOL Multiphysics version 5.3. The simulations were carried out using the Schiller–Neumann correlation for the drag coefficient and two equations for the viscosity calculation: Guth and Simba (1936) and Pal (2000). For the validation of the simulations, the pressure drop was the main control parameter. The simulations predicted the fully dispersed flow patterns and the pressure drop calculated when using the Pal (2000) equation for the viscosity calculation showed the best fit. The results of the images of the flows obtained by the photographs and simulations were in good agreement. <![CDATA[ <p>In multiphase fluid flow, the formation of dispersed patterns, where one of the phases is completely dispersed in the other (continuous medium) is common, for example, in crude oil extraction, during the transport of water/oil mixture. In this work, experimental and numerical studies were carried out for the flow of an oil/water mixture in a horizontal pipe, the dispersed liquid being a paraffin (oil with density 843 kg m<span style="font-family: 微软雅黑, sans-serif">−</span>3 and viscosity 0.025 Pa s) and the continuous medium a water solution doped with NaCl (1000 μS. cm<span style="font-family: 微软雅黑, sans-serif">−</span>1). The tests were made for oil concentrations of 0.01, 0.13 and 0.22 v/v and velocities between 0.9 and 2.6 ms<span style="font-family: 微软雅黑, sans-serif">−</span>1 of the mixture. Experimental work was performed in a pilot rig equipped with an electrical impedance tomography (EIT) system. Information on pressure drop, EIT maps, volumetric concentrations in the vertical diameter of the pipe and flow images were obtained. Simulations were performed in 2-dimensional geometry using the Eulerian–Eulerian approach and the <em>k</em>-ε model for turbulence modelling. The model was implemented in a computational fluid dynamics platform with the programme COMSOL Multiphysics version 5.3. The simulations were carried out using the Schiller–Neumann correlation for the drag coefficient and two equations for the viscosity calculation: Guth and Simba (1936) and Pal (2000). For the validation of the simulations, the pressure drop was the main control parameter. The simulations predicted the fully dispersed flow patterns and the pressure drop calculated when using the Pal (2000) equation for the viscosity calculation showed the best fit. The results of the images of the flows obtained by the photographs and simulations were in good agreement.</p> ]]> Oil/Water Flow in a Horizontal Pipe—Dispersed Flow Regime d.s. santos f.a.p. garcia m.g. rasteiro doi: 10.2495/CMEM-V8-N2-123-134 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 123 10.2495/CMEM-V8-N2-123-134 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-123-134 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-111-122 The approach to obtain a specific user-defined/as-desired or conformal/epitaxial microstructure in additive manufacturing (AM) is a challenging and expensive iterative process. Modeling and validation of solidification microstructure and residual stresses can be leveraged to reduce iteration cost in obtaining as-desired microstructure, minimize residual stress and prevent hot cracking. In the present study, computational fluid dynamics analysis is used to predict melt pool characteristics, and phase-field modeling is employed to simulate solidification with corresponding microstructure evolution in the as-deposited state for laser powder bed fusion (LPBF) process. Different features of LPBF microstructure such as segregation of secondary elements, dendrite sizes, dendritic orientation and dendritic morphology are predicted. The methods are further extended to predict orientation change as a function of number of layers. A constitutive materials model coupled to solidification is used to predict the stress in as-built part as well as the effect of stress on microstructural features. The model encompasses the effect of thermo-mechanical and shrinkage stresses and considers creep flow due to the presence of liquid phases in the mushy region. A phase-field-based methodology is proposed that can solve for hot cracking starting from the intrinsic defects such as porosity in LPBF process. Depending on the residual stress, crack propagation can be predicted from the unified model. The model was incorporated in a finite element code and used to predict crack growth phenomena such as values of critical stress, crack path, etc. Phase-field models of crack growth reduce the computational complications associated with singularitiesand allow finite element predictions of crack propagation without remeshing. This work intends to develop a unified phase-field framework that can sequentially predict solidification microstructure, residual stresses and structural cracking. <![CDATA[ <p>The approach to obtain a specific user-defined/as-desired or conformal/epitaxial microstructure in additive manufacturing (AM) is a challenging and expensive iterative process. Modeling and validation of solidification microstructure and residual stresses can be leveraged to reduce iteration cost in obtaining as-desired microstructure, minimize residual stress and prevent hot cracking. In the present study, computational fluid dynamics analysis is used to predict melt pool characteristics, and phase-field modeling is employed to simulate solidification with corresponding microstructure evolution in the as-deposited state for laser powder bed fusion (LPBF) process. Different features of LPBF microstructure such as segregation of secondary elements, dendrite sizes, dendritic orientation and dendritic morphology are predicted. The methods are further extended to predict orientation change as a function of number of layers. A constitutive materials model coupled to solidification is used to predict the stress in as-built part as well as the effect of stress on microstructural features. The model encompasses the effect of thermo-mechanical and shrinkage stresses and considers creep flow due to the presence of liquid phases in the mushy region. A phase-field-based methodology is proposed that can solve for hot cracking starting from the intrinsic defects such as porosity in LPBF process. Depending on the residual stress, crack propagation can be predicted from the unified model. The model was incorporated in a finite element code and used to predict crack growth phenomena such as values of critical stress, crack path, etc. Phase-field models of crack growth reduce the computational complications associated with singularitiesand allow finite element predictions of crack propagation without remeshing. This work intends to develop a unified phase-field framework that can sequentially predict solidification microstructure, residual stresses and structural cracking.</p> ]]> Development of Unified Framewo Rk For Microstructure, Residual Stress, and Crack Propensity Prediction Using Phase-field Simulations alexander staroselsky ranadip acharya brice cassenti doi: 10.2495/CMEM-V8-N2-111-122 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 2 Article 111 10.2495/CMEM-V8-N2-111-122 https://www.acadlore.com/article/IJCMEM/2020_8_2/CMEM-V8-N2-111-122 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-70-90 A piece of software that acts as a Graphical User Interface (GUI) for the setup of computational fluid dynamics (CFD) models that are solved by means of the open source code OpenFOAM, is presented. The software is extensively described, with emphasis in the generation of block structured meshes using hexahedral elements. This computer program has been developed aiming at being applied in wind engineering problems of interest in civil engineering, such as the computation of force coefficients, flutter derivatives and vortex-induced vibrations. It has been devised to deal efficiently withrectangular cylinders and streamlined box decks. This software demands limited intervention from the user, and its core routines can be embedded in automated design processes such as parametric or optimal design problems in wind engineering. Two application examples have been considered: static and forced oscillation simulations of both, a side ratio 2:1 rectangular cylinder and a streamlined box deck. It has been found that this software is an efficient tool for the setup of URANS simulations in OpenFOAM, while the numerical results obtained for the studied aerodynamic and aeroelastic phenomena show good agreement with wind tunnel data, and their level of accuracy is equivalent to other CFD-based simulations. <![CDATA[ <p>A piece of software that acts as a Graphical User Interface (GUI) for the setup of computational fluid dynamics (CFD) models that are solved by means of the open source code OpenFOAM, is presented. The software is extensively described, with emphasis in the generation of block structured meshes using hexahedral elements. This computer program has been developed aiming at being applied in wind engineering problems of interest in civil engineering, such as the computation of force coefficients, flutter derivatives and vortex-induced vibrations. It has been devised to deal efficiently withrectangular cylinders and streamlined box decks. This software demands limited intervention from the user, and its core routines can be embedded in automated design processes such as parametric or optimal design problems in wind engineering. Two application examples have been considered: static and forced oscillation simulations of both, a side ratio 2:1 rectangular cylinder and a streamlined box deck. It has been found that this software is an efficient tool for the setup of URANS simulations in OpenFOAM, while the numerical results obtained for the studied aerodynamic and aeroelastic phenomena show good agreement with wind tunnel data, and their level of accuracy is equivalent to other CFD-based simulations.</p> ]]> Semi-automated Setupof Cfd Simulations of Rectangular Cylinders snd Streamlined Box Decks félix nieto antonio j. álvarez santiago hernández antía troche doi: 10.2495/CMEM-V8-N1-70-90 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 70 10.2495/CMEM-V8-N1-70-90 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-70-90 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-61-69 Mud pumps, like those used in the field of oil well drilling, are typically of the reciprocating type and are designed to circulate drilling fluid under high pressure down the drill string and back up the annulus. Automatic valves must be applied to the fluid end in order to grant the desired pumping effect. From the engineering point of view, the design of the valve geometry must ensure that the phenomenon of cavitation does not occur and that, during the pumping action, the stiffness of the reaction coil spring is able to avoid reaching the condition of end stroke of the valve. Cavitation consists in the development of vapour cavities in the liquid phase. Inside the cavities, the pressure is relatively low. When subjected to higher pressure, the voids implode and generate an intense shock waves that promote the wear for the components (i.e. valve, valve seat, etc.). A deep understanding of the fluid behaviour is crucial for an effective design. Transient CFD simulations of the valve opening have been performed using a non-Newtonian fluid model able to describe the drilling muds. After a deep literature review, the Herschel-Bulkley model was selected as the most suitable for emulating the drilling mud. With the abovementioned approach, the reaction spring and design the valve seat to avoid premature wear phenomena were properly designed. The simulations have been also done considering a Newtonian fluid behaviour, in order to better understand the importance of considering the non-Newton behaviour for an effective design. <![CDATA[ <p>Mud pumps, like those used in the field of oil well drilling, are typically of the reciprocating type and are designed to circulate drilling fluid under high pressure down the drill string and back up the annulus. Automatic valves must be applied to the fluid end in order to grant the desired pumping effect. From the engineering point of view, the design of the valve geometry must ensure that the phenomenon of cavitation does not occur and that, during the pumping action, the stiffness of the reaction coil spring is able to avoid reaching the condition of end stroke of the valve. Cavitation consists in the development of vapour cavities in the liquid phase. Inside the cavities, the pressure is relatively low. When subjected to higher pressure, the voids implode and generate an intense shock waves that promote the wear for the components (i.e. valve, valve seat, etc.). A deep understanding of the fluid behaviour is crucial for an effective design. Transient CFD simulations of the valve opening have been performed using a non-Newtonian fluid model able to describe the drilling muds. After a deep literature review, the Herschel-Bulkley model was selected as the most suitable for emulating the drilling mud. With the abovementioned approach, the reaction spring and design the valve seat to avoid premature wear phenomena were properly designed. The simulations have been also done considering a Newtonian fluid behaviour, in order to better understand the importance of considering the non-Newton behaviour for an effective design.</p> ]]> Non-Newtonian Cfd Modelling of A Valve For Mud Pumps f. concli c. gorla doi: 10.2495/CMEM-V8-N1-61-69 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 61 10.2495/CMEM-V8-N1-61-69 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-61-69 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-47-60 In the case of computational models of lyophilization in a vial, the intensity of drying is to a large extent controlled by the pressure conditions above the drying surface, as the drying driving force is the pressure difference between the saturation vapour pressure at the sublimation interface and the vapour partial pressure above the drying substance. In majority of studies, the effect of the vial and the rubber stopper geometry on the pressure conditions inside the vial is either neglected or taken into account by an estimated additional vapour pressure increase inside the vial. As the pressure conditions depend on the flow of sublimated solvent inside the vial-stopper conduit geometry, but are experimentally difficult to determine, a dedicated CFD analysis of flow conditions inside the vial-stopper channel was performed. The influence of imposing of the no-slip and slip conditions on the solid surfaces on the pressure drop in the system was studied and the effect of the increased partial pressure of the solvent on the sublimation rate was evaluated for the starting phase of the lyophilization by implementing the Stefan’s one sided diffusion model. The computational results show, that the effect of the additional flow resistance due to the vial conduit and the stopper is most significant at lowest system temperatures, with as much as 30% increase in vapour pressure inside the vial. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In the case of computational models of lyophilization in a vial, the intensity of drying is to a large extent controlled by the pressure conditions above the drying surface, as the drying driving force is the pressure difference between the saturation vapour pressure at the sublimation interface and the vapour partial pressure above the drying substance. In majority of studies, the effect of the vial and the rubber stopper geometry on the pressure conditions inside the vial is either neglected or taken into account by an estimated additional vapour pressure increase inside the vial. As the pressure conditions depend on the flow of sublimated solvent inside the vial-stopper conduit geometry, but are experimentally difficult to determine, a dedicated CFD analysis of flow conditions inside the vial-stopper channel was performed. The influence of imposing of the no-slip and slip conditions on the solid surfaces on the pressure drop in the system was studied and the effect of the increased partial pressure of the solvent on the sublimation rate was evaluated for the starting phase of the lyophilization by implementing the Stefan’s one sided diffusion model. The computational results show, that the effect of the additional flow resistance due to the vial conduit and the stopper is most significant at lowest system temperatures, with as much as 30% increase in vapour pressure inside the vial.</span></p> ]]> CFD Based Determination of Sublimation Mass Flux for Lyophilization inside a Vial matej zadravec žiga časar jure ravnik matjaž hriberšek doi: 10.2495/CMEM-V8-N1-47-60 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 47 10.2495/CMEM-V8-N1-47-60 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-47-60 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-36-46 This article concerns a reduced order model of unconstrained glass plate exposed to low-velocity impact. First, three-parametric model consisting of two masses connected with elastic spring is introduced, its calibration procedure is described, and the simulation of its response to force impulses with different duration is shown. Then a five-parametric variant of the reduced order model is presented, calibrated and tested. Combined with the Hertzian theory of non-adhesive contact, the model allows us to determine the time evolution of contact force for arbitrary mass, stiffness and initial velocity of the impactor. The simulated results are compared to experimentally obtained data and observations about the model properties and accuracy are made. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This article concerns a reduced order model of unconstrained glass plate exposed to low-velocity impact. First, three-parametric model consisting of two masses connected with elastic spring is introduced, its calibration procedure is described, and the simulation of its response to force impulses with different duration is shown. Then a five-parametric variant of the reduced order model is presented, calibrated and tested. Combined with the Hertzian theory of non-adhesive contact, the model allows us to determine the time evolution of contact force for arbitrary mass, stiffness and initial velocity of the impactor. The simulated results are compared to experimentally obtained data and observations about the model properties and accuracy are made.</span></p> ]]> Reduced Order Model of Glass Plate Loaded by Low-Velocity Impact tomáš janda alena zemanová petr hála petr konrád jaroslav schmidt doi: 10.2495/CMEM-V8-N1-36-46 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 36 10.2495/CMEM-V8-N1-36-46 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-36-46 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-27-35 Falling particle curtains are important in many engineering applications, including receivers for concentrating solar power facilities. During the formation of such a curtain, we observe a multiphase analog of Rayleigh–Taylor instability (RTI). It was originally described in 2011 for a situation when air sparsely seeded with glycol droplets was placed above a volume of unseeded air, producing an unstably stratified average density distribution that was characterized by an effective Atwood number 0.03. In that case, the evolution of the instability was indistinguishable from single-phase RTI with the same Atwood number, as the presence of the droplets largely acted as an additional contribution to the mean density of the gaseous medium. Here, we present experiments where the volume (and mass) fraction of the seeding particles in gas is considerably higher, and the gravity-driven flow is dominated by the particle movement. In this case, the evolution of the observed instability appears significantly different. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Falling particle curtains are important in many engineering applications, including receivers for concentrating solar power facilities. During the formation of such a curtain, we observe a multiphase analog of Rayleigh–Taylor instability (RTI). It was originally described in 2011 for a situation when air sparsely seeded with glycol droplets was placed above a volume of unseeded air, producing an unstably stratified average density distribution that was characterized by an effective Atwood number 0.03. In that case, the evolution of the instability was indistinguishable from single-phase RTI with the same Atwood number, as the presence of the droplets largely acted as an additional contribution to the mean density of the gaseous medium. Here, we present experiments where the volume (and mass) fraction of the seeding particles in gas is considerably higher, and the gravity-driven flow is dominated by the particle movement. In this case, the evolution of the observed instability appears significantly different.</span></p> ]]> Formation of a Falling Particle Curtain peter vorobieff patrick wayne sumanth reddy lingampally gregory vigil josh ludwigsen daniel freelong c. randall truman gustaaf jacobs doi: 10.2495/CMEM-V8-N1-27-35 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 27 10.2495/CMEM-V8-N1-27-35 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-27-35 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-13-26 A new defouling erosion model for Lagrangian particle tracking is used to predict defouling of amorphous, heterogeneous coatings such as those typically found in aircraft compressors. The main problem description, the mathematical formulation and the underpinning experiment of the model are presented in a previous communication by the authors. In this work, the Ansys CFX implementation of the model is described and an experiment is presented for the validation of the model. Air flows laden with a number of dry-ice particles are observed in an optically accessible stream channel containing a flat plate target. The defouling process of these particles is recorded with HSCs and the main parameters, such as indentation size in fouling layers, are processed and compared to corresponding numerical results. The model parameters considered are particle impact velocity and angle as well as particle and fouling material. Typical coatings which are relevant to commercial aircraft defouling processes are investi- gated. The target plate angle and the air velocity are varied and dry-ice particles of random size and shape are injected into the flow. The experiment is set up in a wind-tunnel test-rig and all recordings are made using two HSCs, a digital camera and Prandtl probe measurement. Experimental and numerical defouling results show good overall agreement for steep target angles but significant deviations for low target angles. Potential improvement to the defouling erosion model is discussed based on these results. The model as presented is used in large-scale compressor defouling simulations in the development process of on-wing aircraft maintenance systems. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A new defouling erosion model for Lagrangian particle tracking is used to predict defouling of amorphous, heterogeneous coatings such as those typically found in aircraft compressors. The main problem description, the mathematical formulation and the underpinning experiment of the model are presented in a previous communication by the authors. In this work, the Ansys CFX implementation of the model is described and an experiment is presented for the validation of the model. Air flows laden with a number of dry-ice particles are observed in an optically accessible stream channel containing a flat plate target. The defouling process of these particles is recorded with HSCs and the main parameters, such as indentation size in fouling layers, are processed and compared to corresponding numerical results. The model parameters considered are particle impact velocity and angle as well as particle and fouling material. Typical coatings which are relevant to commercial aircraft defouling processes are investi- gated. The target plate angle and the air velocity are varied and dry-ice particles of random size and shape are injected into the flow. The experiment is set up in a wind-tunnel test-rig and all recordings are made using two HSCs, a digital camera and Prandtl probe measurement. Experimental and numerical defouling results show good overall agreement for steep target angles but significant deviations for low target angles. Potential improvement to the defouling erosion model is discussed based on these results. The model as presented is used in large-scale compressor defouling simulations in the development process of on-wing aircraft maintenance systems.</span></p> ]]> A Validation Study for a New Erosion Model to Predict Erosive Airfoil Defouling arthur rudek david muckenhaupt thomas zitzmann gerald russ barry duignan doi: 10.2495/CMEM-V8-N1-13-26 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 13 10.2495/CMEM-V8-N1-13-26 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-13-26 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-1-12 Experimental studies using an X-ray tomography system were performed on a 4-inch horizontal section of the multiphase flow loop at NEL for gas–water and gas–oil–water flows. Values of liquid holdup and water liquid ratio are reported alongside analysis of the phase linear fraction through the cross-section of the pipe. The X-ray system revealed areas of gas entrainment and separation of oil and water which are not evident from high-speed video footage. The flow pattern of the tests was stratified-wavy, and computational fluid dynamics (CFD) analysis was performed using the volume of fluid (VOF) method. The prediction of liquid holdup and gas distribution through the pipe height as determined by CFD, correlated well with that determined by X-ray tomography. however, the results suggest that a transient VOF with a high-order mesh resolution is required to account for gas entrainment. This study shows that an X-ray system can be utilised to provide quantifiable validation data which are of value to multiphase models in CFD and provide insight that is not apparent during high-speed video analysis. The data generated from this system will be of considerable value to multiphase flow specialists and instrumentation developers. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Experimental studies using an X-ray tomography system were performed on a 4-inch horizontal section of the multiphase flow loop at NEL for gas–water and gas–oil–water flows. Values of liquid holdup and water liquid ratio are reported alongside analysis of the phase linear fraction through the cross-section of the pipe. The X-ray system revealed areas of gas entrainment and separation of oil and water which are not evident from high-speed video footage. The flow pattern of the tests was stratified-wavy, and computational fluid dynamics (CFD) analysis was performed using the volume of fluid (VOF) method. The prediction of liquid holdup and gas distribution through the pipe height as determined by CFD, correlated well with that determined by X-ray tomography. however, the results suggest that a transient VOF with a high-order mesh resolution is required to account for gas entrainment. This study shows that an X-ray system can be utilised to provide quantifiable validation data which are of value to multiphase models in CFD and provide insight that is not apparent during high-speed video analysis. The data generated from this system will be of considerable value to multiphase flow specialists and instrumentation developers.</span></p> ]]> X-Ray Tomography Reconstruction of Multiphase Flows and the Verification of CFD sandy black marc laing doi: 10.2495/CMEM-V8-N1-1-12 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2020 8 1 Article 1 10.2495/CMEM-V8-N1-1-12 https://www.acadlore.com/article/IJCMEM/2020_8_1/CMEM-V8-N1-1-12 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-376-384 The anammox process, used to remove nitrogen from wastewaters is conside red a promising approach due to its advantages over traditional processes. The current study emphasizes on the cost effective nitrogen removal from the sidestream effluent of anaerobic digester with partial nitration (PN) and anaerobic ammonium oxidation (anammox) process for the municipal wastewater treatment plant. The main objective of this study was to model a cost effective strategy for setting up a lab-scale sequencing batch reactor (SBR) by using activated sludge model (ASM) process equations with applying novel control strategies (NCS) for improving nitrogen-removal efficiency (NRE). An average rate of removal 80% was obtained during the period of its operation. NCS (intermittent aeration, alteration in the cycle length, etc) were introduced to optimize the operating cost. The overall system contributes to lower- ing in the greenhouse gas emissions by minimizing the use of energy (60–65%) and hence supporting the WHO mission of achieving sustainable development goals. Results further indicate the future possibility of escalating the lab-scale to full-scale applications. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The anammox process, used to remove nitrogen from wastewaters is conside red a promising approach due to its advantages over traditional processes. The current study emphasizes on the cost effective nitrogen removal from the sidestream effluent of anaerobic digester with partial nitration (PN) and anaerobic ammonium oxidation (anammox) process for the municipal wastewater treatment plant. The main objective of this study was to model a cost effective strategy for setting up a lab-scale sequencing batch reactor (SBR) by using activated sludge model (ASM) process equations with applying novel control strategies (NCS) for improving nitrogen-removal efficiency (NRE). An average rate of removal 80% was obtained during the period of its operation. NCS (intermittent aeration, alteration in the cycle length, etc) were introduced to optimize the operating cost. The overall system contributes to lower- ing in the greenhouse gas emissions by minimizing the use of energy (60–65%) and hence supporting the WHO mission of achieving sustainable development goals. Results further indicate the future possibility of escalating the lab-scale to full-scale applications.</span></p> ]]> Cost Effective Nitrogen Removal – Novel Control Strategies alam nawaz amarpreet singh arora choa mun yun hwanchul cho moonyong lee doi: 10.2495/CMEM-V7-N4-376-384 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 376 10.2495/CMEM-V7-N4-376-384 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-376-384 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-363-375 A computational model for analysis of rate-dependent interface damage which leads to interface crack initiation and propagation in multi-domain structures exposed to shear type cyclic loading is presented. Modelling of interface damage, accounting generally for various stress vs. separation relations of common cohesive zone models in this type of models, is restricted here to one with an exponential relation. The model also includes viscosity and internal parameters for the interface damage to observe a fatigue- like behaviour where a crack appears for smaller magnitudes of periodical loadings in comparison to pure uploading.The computational approach, physically based on evolution of stored and dissipated energies, behind the model results in a kind of variational formulation. Moreover, solving the problem for variables characterising the elastic state of the structure, the multi-domain symmetric Galerkin boundary element method is advantageously used. Finally, the variational character of the solution requires implementation of (sequential) quadratic programing solvers into the computer code which is fully implemented in MATLAB.The presented numerical results for a rather academic structure demonstrate the properties of the described model and enable to extend its applicability to more general problems of engineering practice. <![CDATA[ <p>A computational model for analysis of rate-dependent interface damage which leads to interface crack initiation and propagation in multi-domain structures exposed to shear type cyclic loading is presented. Modelling of interface damage, accounting generally for various stress vs. separation relations of common cohesive zone models in this type of models, is restricted here to one with an exponential relation. The model also includes viscosity and internal parameters for the interface damage to observe a fatigue- like behaviour where a crack appears for smaller magnitudes of periodical loadings in comparison to pure uploading.</p><p style="text-align: justify">The computational approach, physically based on evolution of stored and dissipated energies, behind the model results in a kind of variational formulation. Moreover, solving the problem for variables characterising the elastic state of the structure, the multi-domain symmetric Galerkin boundary element method is advantageously used. Finally, the variational character of the solution requires implementation of (sequential) quadratic programing solvers into the computer code which is fully implemented in MATLAB.</p><p style="text-align: justify">The presented numerical results for a rather academic structure demonstrate the properties of the described model and enable to extend its applicability to more general problems of engineering practice.</p> ]]> A Boundary Element Approach for an Interface Visco-Damage Model Exposed to Cyclic Shear Load roman vodička katarína krajníková doi: 10.2495/CMEM-V7-N4-363-375 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 363 10.2495/CMEM-V7-N4-363-375 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-363-375 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-350-362 The application of 3D motion capture systems to shaking table testing provides a unique tool for recording relative displacements of a large number of measurement points of the tested structure. The analysis of 3D relative displacements during dynamic tests allows us to evaluate the structure deformations and to monitor the cracks formation and evolution. The present paper focuses on the processing and analysis of 3D motion capture data to extract accurate displacements between markers positioned on a full-scale model of a masonry cross vault representing a vault of the mosque of Dey, Algiers, tested at the ENEA Casaccia Research Centre. The management and processing of the data acquired through 67 markers located on the vault are described, showing the potentialities of the methodology. Moreover, the possible formulation of damage indices based on the structure deformations and cracks aperture detected from markers relative displacements (MRDs) was explored. In particular, cracks could be counted and classified as a function of the detected apertures, following damage thresholds indicated in the Italian regulations. Moreover, the failure mechanism could be easily visualized and analysed by monitoring the cumulative MRDs. In addition, in-plane and out-of-plane deformations of walls could be monitored during each seismic test, providing accurate information on the torsional and bending effects. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The application of 3D motion capture systems to shaking table testing provides a unique tool for recording relative displacements of a large number of measurement points of the tested structure. The analysis of 3D relative displacements during dynamic tests allows us to evaluate the structure deformations and to monitor the cracks formation and evolution. The present paper focuses on the processing and analysis of 3D motion capture data to extract accurate displacements between markers positioned on a full-scale model of a masonry cross vault representing a vault of the mosque of Dey, Algiers, tested at the ENEA Casaccia Research Centre. The management and processing of the data acquired through 67 markers located on the vault are described, showing the potentialities of the methodology. Moreover, the possible formulation of damage indices based on the structure deformations and cracks aperture detected from markers relative displacements (MRDs) was explored. In particular, cracks could be counted and classified as a function of the detected apertures, following damage thresholds indicated in the Italian regulations. Moreover, the failure mechanism could be easily visualized and analysed by monitoring the cumulative MRDs. In addition, in-plane and out-of-plane deformations of walls could be monitored during each seismic test, providing accurate information on the torsional and bending effects. </span></p> ]]> Relative Displacements of 3D Optical Markers for Deformations and Crack Monitoring of a Masonry Structure Under Shaking Table Tests ivan roselli gerardo de canio michela rossi chiara calderini sergio lagomarsino doi: 10.2495/CMEM-V7-N4-350-362 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 350 10.2495/CMEM-V7-N4-350-362 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-350-362 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-340-349 To reduce wear in tribosystems, the formation of a protective tribofilm is beneficial. by applying additives to the lubricating oil or grease, an anti-wear boundary layer can be achieved. For simulating the induced stresses on the bearings surface, the formed tribofilm should be regarded. In this study, cylindrical roller thrust bearings were investigated regarding a tribofilm formed by oil containing zinc dialkyldithiophosphate (ZDDP) additives. Due to the test conditions, a smooth film with low roughness forms on the surface. The film consists of glassy Fe/Zn polyphosphates with a height of up to 150 nm and a width of approximately 1 µm. based on the roughness, the surface was modelled with regularly distributed dimples to be used for a finite element model for the contact between a roller and a bearing washer regarding contact stress and tangential forces due to slip. The dimples in the contact between roller and washer lead to an inhomogeneous pressure distribution near the surface. During the contact, the surface pads of the roller partly slide over the surface pads of the washer in dependence of the contact position. of particular interest is the deformation in running direction. If the asperities of the roller press against the washers asperities, a significant deformation at the dimples and in the volume underneath occurs. As expected, the strains occur in the regions with high deformation gradients. During rolling, the deformations lead to areas that are stretched and compressed. The maximum strains are located between the dimples and shift in rolling direction from pad to pad. It has to be assumed, that the formation of cracks starts between the dimples at the surface and develop along the stretched areas whereas the cracking in the compressed areas is suppressed or at least impeded. The simulative results were compared to literature proving that the values determined by simulation are in well agreement. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">To reduce wear in tribosystems, the formation of a protective tribofilm is beneficial. by applying additives to the lubricating oil or grease, an anti-wear boundary layer can be achieved. For simulating the induced stresses on the bearings surface, the formed tribofilm should be regarded. In this study, cylindrical roller thrust bearings were investigated regarding a tribofilm formed by oil containing zinc dialkyldithiophosphate (ZDDP) additives. Due to the test conditions, a smooth film with low roughness forms on the surface. The film consists of glassy Fe/Zn polyphosphates with a height of up to 150 nm and a width of approximately 1 µm. based on the roughness, the surface was modelled with regularly distributed dimples to be used for a finite element model for the contact between a roller and a bearing washer regarding contact stress and tangential forces due to slip. The dimples in the contact between roller and washer lead to an inhomogeneous pressure distribution near the surface. During the contact, the surface pads of the roller partly slide over the surface pads of the washer in dependence of the contact position. of particular interest is the deformation in running direction. If the asperities of the roller press against the washers asperities, a significant deformation at the dimples and in the volume underneath occurs. As expected, the strains occur in the regions with high deformation gradients. During rolling, the deformations lead to areas that are stretched and compressed. The maximum strains are located between the dimples and shift in rolling direction from pad to pad. It has to be assumed, that the formation of cracks starts between the dimples at the surface and develop along the stretched areas whereas the cracking in the compressed areas is suppressed or at least impeded. The simulative results were compared to literature proving that the values determined by simulation are in well agreement. </span></p> ]]> Computational Investigation of Crack Inducing Forces on Bearing Surfaces Regarding the Tribofilm Structure florian pape martin petzold gerhard poll doi: 10.2495/CMEM-V7-N4-340-349 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 340 10.2495/CMEM-V7-N4-340-349 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-340-349 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-327-339 With the development of new materials, it is now known that there is no such thing as a fatigue endur- ance limit, i.e. materials do not have infinite life when the stress level is such that there is no fracture up to 10 million (1E7) cycles. The problem of testing materials above this number of cycles is that most testing equipment operates well below 150 Hz, making testing up to 1 billion (1E9) cycles or above is an impracticality. The recent developments of ultrasonic testing machines where frequencies can go as high as 20 kHz or above enabled tests to be extended to these ranges in just a few days. This is known as very high cycle fatigue (VHCF). On the other hand, critical components used in engineering applications are usually subjected to multi-axial loads, as is the case of the fuselage and wings of aircrafts which are subjected to biaxial states of stress. In this paper, VHCF cruciform test specimens purposely designed to develop orthogonal biaxial stresses with different biaxiality ratios will be analysed. The specimens are composed from Aluminium 6082-T651, a medium strength alloy used in many highly stressed engineering applications, including trusses, cranes, bridges and transportation. The specimens work as tuning forks with determined mode shapes at 20±0.5 kHz, where maximum principal stresses are developed at the centre of the specimen. Finite element analysis (FEA) is used to assess the dynamic behaviour of the specimens. The framework on how to design and manufacture cruciform specimens with different biaxiality ratios will be explained in a clear way so it can be used by other engineers in the field. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">With the development of new materials, it is now known that there is no such thing as a fatigue endur- ance limit, i.e. materials do not have infinite life when the stress level is such that there is no fracture up to 10 million (1E7) cycles. The problem of testing materials above this number of cycles is that most testing equipment operates well below 150 Hz, making testing up to 1 billion (1E9) cycles or above is an impracticality. The recent developments of ultrasonic testing machines where frequencies can go as high as 20 kHz or above enabled tests to be extended to these ranges in just a few days. This is known as very high cycle fatigue (VHCF). On the other hand, critical components used in engineering applications are usually subjected to multi-axial loads, as is the case of the fuselage and wings of aircrafts which are subjected to biaxial states of stress. In this paper, VHCF cruciform test specimens purposely designed to develop orthogonal biaxial stresses with different biaxiality ratios will be analysed. The specimens are composed from Aluminium 6082-T651, a medium strength alloy used in many highly stressed engineering applications, including trusses, cranes, bridges and transportation. The specimens work as tuning forks with determined mode shapes at 20±0.5 kHz, where maximum principal stresses are developed at the centre of the specimen. Finite element analysis (FEA) is used to assess the dynamic behaviour of the specimens. The framework on how to design and manufacture cruciform specimens with different biaxiality ratios will be explained in a clear way so it can be used by other engineers in the field.</span></p> ]]> Numerical Analysis of VHCF Cruciform Test Specimens with Non-Unitary Biaxiality Ratios diogo montalvão attila blaskovics pedro costa luís reis manuel freitas doi: 10.2495/CMEM-V7-N4-327-339 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 327 10.2495/CMEM-V7-N4-327-339 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-327-339 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-316-326 Dredge pumps are a complex engineering topic in comparison to water pumps. Mixtures of seawater with several types of soils do not behave as a homogenous fluid, and numerical simulations of these machines can be very challenging. Typical numerical approaches to simulations of dredge pumps are single-phase equivalent slurry and multi-phase liquid–solid, where the specification of the particle flow field can be Eulerian or lagrangian. The single-phase slurry approach is not sufficient to describe the effects of particle size and concentration of the solid phase on pump performance; for this reason, this paper examines a multi-phase CFD model applied to a dredge pump. The solid phase is modelled with an Eulerian approach, in order to reduce the computational effort required by a lagrangian method, mainly used for low solid-phase concentrations. The primary purpose of the presented model, developed using commercial software aNSYS CFX, is to predict head losses in a dredge pump working with several particle sizes, from 0.1 to 5 mm, and different volume concentrations of the solid phase, from 20% to 30%. For numerical solid-phase calibration, the effect of the particle size on pump performance is associated with non-Newtonian rheology of the simulated Eulerian phase. The numerical model is validated via experimental tests on the dredge pump using seawater. The calibration of the particle size effect is obtained from scientific literature data about dredge pump losses in different conditions. The model presented could be a useful tool for the analysis of existing dredge pumps or for the design of new machines. <![CDATA[ <p>Dredge pumps are a complex engineering topic in comparison to water pumps. Mixtures of seawater with several types of soils do not behave as a homogenous fluid, and numerical simulations of these machines can be very challenging. Typical numerical approaches to simulations of dredge pumps are single-phase equivalent slurry and multi-phase liquid–solid, where the specification of the particle flow field can be Eulerian or lagrangian. The single-phase slurry approach is not sufficient to describe the effects of particle size and concentration of the solid phase on pump performance; for this reason, this paper examines a multi-phase CFD model applied to a dredge pump. The solid phase is modelled with an Eulerian approach, in order to reduce the computational effort required by a lagrangian method, mainly used for low solid-phase concentrations. The primary purpose of the presented model, developed using commercial software aNSYS CFX, is to predict head losses in a dredge pump working with several particle sizes, from 0.1 to 5 mm, and different volume concentrations of the solid phase, from 20% to 30%. For numerical solid-phase calibration, the effect of the particle size on pump performance is associated with non-Newtonian rheology of the simulated Eulerian phase. The numerical model is validated via experimental tests on the dredge pump using seawater. The calibration of the particle size effect is obtained from scientific literature data about dredge pump losses in different conditions. The model presented could be a useful tool for the analysis of existing dredge pumps or for the design of new machines.</p> ]]> Eulerian Multi-Phase CFD Model for Predicting the Performance of a Centrifugal Dredge Pump nicolò beccati cristian ferrari marco parma massimo semprini doi: 10.2495/CMEM-V7-N4-316-326 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 316 10.2495/CMEM-V7-N4-316-326 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-316-326 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-305-315 A numerical investigation is carried out to evaluate the influence of the gap between the bluff body and the bed on the wake characteristics generated in shallow flows. A sharp-edge bluff body with a fixed gap from the bed is employed in the study, and the results are compared with the no gap case. A sharp-edged bluff body was chosen to minimize the effect of reynolds number and ensure fixed flow separation points. The transient three-dimensional Navier–Stokes equations are numerically solved using a finite volume approach with the detached eddy simulation turbulence model. The flow field in this study involves two different fluids, i.e. water and the air above it. The volume of fluid method is used for tracking the free surface separating the water and air. The fluid structures that are generated in the wake are identified using the λ2-criterion. The results reveal that the gap flow will develop a new structure near the bed, which enhances the upwash flow immediately after the submerged jet is about to turn upwards due to the weak hydraulic jump. This structure plays an important role in recovering the free surface to its original shape at a shorter downstream distance from the bluff body than when there is no gap. <![CDATA[ <p>A numerical investigation is carried out to evaluate the influence of the gap between the bluff body and the bed on the wake characteristics generated in shallow flows. A sharp-edge bluff body with a fixed gap from the bed is employed in the study, and the results are compared with the no gap case. A sharp-edged bluff body was chosen to minimize the effect of reynolds number and ensure fixed flow separation points. The transient three-dimensional Navier–Stokes equations are numerically solved using a finite volume approach with the detached eddy simulation turbulence model. The flow field in this study involves two different fluids, i.e. water and the air above it. The volume of fluid method is used for tracking the free surface separating the water and air. The fluid structures that are generated in the wake are identified using the λ2-criterion. The results reveal that the gap flow will develop a new structure near the bed, which enhances the upwash flow immediately after the submerged jet is about to turn upwards due to the weak hydraulic jump. This structure plays an important role in recovering the free surface to its original shape at a shorter downstream distance from the bluff body than when there is no gap.</p> ]]> Effect of Gap on the Flow Characteristics in the Wake of a Bluff Body Near a Wall g. nasif r. balachandar r.m. barron doi: 10.2495/CMEM-V7-N4-305-315 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 4 Article 305 10.2495/CMEM-V7-N4-305-315 https://www.acadlore.com/article/IJCMEM/2019_7_4/CMEM-V7-N4-305-315 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-285-296 An analytical model using finite element approximation was applied to determine the amount of heat dissipated in a three-body graphite calorimeter used in the field of dosimetry. The temperature drifts and the heat dissipation of the calorimeter bodies via conduction and radiative transfer during electrical heating were considered to enhance heat insulation for the accurate measurement of absorbed dose. A simulation was applied to the heating and cooling process for both electrical calibration and irradia- tion. The heat transfer in the calorimeter bodies and wire could be first estimated quantitatively. The radiation energy absorbed into the core during irradiation was estimated in a heat-loss-compensated mode of operation, and the effects of the wire conduction of the thermistor on the radiant heat loss were investigated. <![CDATA[ <p>An analytical model using finite element approximation was applied to determine the amount of heat dissipated in a three-body graphite calorimeter used in the field of dosimetry. The temperature drifts and the heat dissipation of the calorimeter bodies via conduction and radiative transfer during electrical heating were considered to enhance heat insulation for the accurate measurement of absorbed dose. A simulation was applied to the heating and cooling process for both electrical calibration and irradia- tion. The heat transfer in the calorimeter bodies and wire could be first estimated quantitatively. The radiation energy absorbed into the core during irradiation was estimated in a heat-loss-compensated mode of operation, and the effects of the wire conduction of the thermistor on the radiant heat loss were investigated.</p> ]]> Numerical Simulation of Heat-Loss Compensated Calorimeter yongsoo choi kook jin jeon youngho park sangil hyun doi: 10.2495/CMEM-V7-N3-285-296 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 285 10.2495/CMEM-V7-N3-285-296 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-285-296 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-275-284 In any racing competitions, the aerodynamic performances of the equipment are determinant. This is true, for example, for cars, where the geometry of the bodywork and of the wings can ensure a lower Cx coefficient and/or a higher down-force and a higher handling. In other competitions, like rowing, the aerodynamics of the hull can reduce the effort done by the athletes. In the cycle and motorcycle racing competitions, other aspects related to aerodynamics become important, such as the manoeuvrability and stability. In the present research, a numerical approach was used in order to compare different front-wheel geometries (of a racing motor-bike) in terms of drag, lift and axial forces. Three different wheel designs have been compared. The first one consists in a traditional seven spokes aluminium design, the second wheel is a 6 spokes magnesium solution and the third a solid-disk wheel. Steady state as well as transient simulations was performed with OpenfOaM®, a free open-source software. This was selected because it allows a higher flexibility with respect to any close-source commercial software. The possibility to customize the solver as well as the boundary conditions allows the analysis of the physical problem of interest. The free license allows a high parallelization of the computations. The steady-state simulations were performed by freezing the wheel position and introducing a rotating reference frame. In this way, the computational time was significantly reduced. For the transient simulations, the computational domain was split into two subdomains. The internal one is cylindrical and contains the wheel. The rotational velocity of the wheel was imposed by applying a rigid rotation to the mesh of the internal subdomain. Mesh interfaces ensures the continuity of the solution across the domains. <![CDATA[ <p>In any racing competitions, the aerodynamic performances of the equipment are determinant. This is true, for example, for cars, where the geometry of the bodywork and of the wings can ensure a lower Cx coefficient and/or a higher down-force and a higher handling. In other competitions, like rowing, the aerodynamics of the hull can reduce the effort done by the athletes. In the cycle and motorcycle racing competitions, other aspects related to aerodynamics become important, such as the manoeuvrability and stability. In the present research, a numerical approach was used in order to compare different front-wheel geometries (of a racing motor-bike) in terms of drag, lift and axial forces. Three different wheel designs have been compared. The first one consists in a traditional seven spokes aluminium design, the second wheel is a 6 spokes magnesium solution and the third a solid-disk wheel. Steady state as well as transient simulations was performed with OpenfOaM®, a free open-source software. This was selected because it allows a higher flexibility with respect to any close-source commercial software. The possibility to customize the solver as well as the boundary conditions allows the analysis of the physical problem of interest. The free license allows a high parallelization of the computations. The steady-state simulations were performed by freezing the wheel position and introducing a rotating reference frame. In this way, the computational time was significantly reduced. For the transient simulations, the computational domain was split into two subdomains. The internal one is cylindrical and contains the wheel. The rotational velocity of the wheel was imposed by applying a rigid rotation to the mesh of the internal subdomain. Mesh interfaces ensures the continuity of the solution across the domains.</p> ]]> Aerodynamic Study of Motorcycle Racing Wheels: A Performance Evaluation Based on Numerical Cfd Simulations f. concli m. gobbi c. gorla doi: 10.2495/CMEM-V7-N3-275-284 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 275 10.2495/CMEM-V7-N3-275-284 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-275-284 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-260-274 This article presents the general approach to incorrectly posed boundary value problems of the plane theory of elasticity with the boundary conditions formulated through the directions of displacement vectors and principal directions of the stress tensor. The approach is aimed at studying the solvability of problems of this type and allows one to determine the maximum number of arbitrary parameters on which the solution of the problem depends. We report analytical solutions for three particular formulations for the case of elastic half-plane and propose a numerical approach for solving the problems of this type for arbitrary contours. <![CDATA[ <p>This article presents the general approach to incorrectly posed boundary value problems of the plane theory of elasticity with the boundary conditions formulated through the directions of displacement vectors and principal directions of the stress tensor. The approach is aimed at studying the solvability of problems of this type and allows one to determine the maximum number of arbitrary parameters on which the solution of the problem depends. We report analytical solutions for three particular formulations for the case of elastic half-plane and propose a numerical approach for solving the problems of this type for arbitrary contours.</p> ]]> Incorrectly Posed BVPs for Elastic Half- Plane in Terms of Stress and Displacement Orientations a. n. galybin doi: 10.2495/CMEM-V7-N3-260-274 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 260 10.2495/CMEM-V7-N3-260-274 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-260-274 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-246-259 The radial basis function (RBF) collocation method is applied for the approximation of functions in two variables. When the RBFs employed include a shape parameter, the determination of an appropriate value for it is a major issue. In this work, this is addressed by including the value of the shape parameter in the unknowns along with the coefficients of the RBFs in the approximation. The variable shape parameter case when a different shape parameter is associated with each RBF in the approximation is also considered. Both approaches yield nonlinear systems of equations, which are solved by a standard non-linear solver. The results of several numerical experiments are presented. <![CDATA[ <p>The radial basis function (RBF) collocation method is applied for the approximation of functions in two variables. When the RBFs employed include a shape parameter, the determination of an appropriate value for it is a major issue. In this work, this is addressed by including the value of the shape parameter in the unknowns along with the coefficients of the RBFs in the approximation. The variable shape parameter case when a different shape parameter is associated with each RBF in the approximation is also considered. Both approaches yield nonlinear systems of equations, which are solved by a standard non-linear solver. The results of several numerical experiments are presented.</p> ]]> Shape Parameter Estimation in RBF Function Approximation a. karageorghis p. tryfonos doi: 10.2495/CMEM-V7-N3-246-259 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 246 10.2495/CMEM-V7-N3-246-259 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-246-259 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-236-245 This paper presents the simultaneous cost, standard sizes and rounded dimension optimization of a cantilever roof structure. Since the standard and rounded dimensions are proposed to be handled explicitly in the discrete type of the optimization, the mixed-integer non-linear programming (MINLP) is applied. The structure is built from the standard hot rolled steel I sections for columns, beams and struts, and from the reinforced concrete bases. The MINLP optimization model of the cantilever roof structure is developed. The model comprises the objective function of the structure’s self-manufacturing costs and the design, resistance and dimensioning (in)equality constraints. The latter are defined in accordance with the Eurocode 2, 3 and 7 specifications. The modified outer-approximation/equality- relaxation (OA/ER) algorithm is used. The MINLP optimization of a cantilever roof structure for a small football stadium near the city of Maribor in Slovenia is presented at the end of the paper. The obtained optimal result includes the minimal production costs of the structure, the optimal standard sections of steel elements and the optimal rounded dimensions of the concrete bases. <![CDATA[ <p>This paper presents the simultaneous cost, standard sizes and rounded dimension optimization of a cantilever roof structure. Since the standard and rounded dimensions are proposed to be handled explicitly in the discrete type of the optimization, the mixed-integer non-linear programming (MINLP) is applied. The structure is built from the standard hot rolled steel I sections for columns, beams and struts, and from the reinforced concrete bases. The MINLP optimization model of the cantilever roof structure is developed. The model comprises the objective function of the structure’s self-manufacturing costs and the design, resistance and dimensioning (in)equality constraints. The latter are defined in accordance with the Eurocode 2, 3 and 7 specifications. The modified outer-approximation/equality- relaxation (OA/ER) algorithm is used. The MINLP optimization of a cantilever roof structure for a small football stadium near the city of Maribor in Slovenia is presented at the end of the paper. The obtained optimal result includes the minimal production costs of the structure, the optimal standard sections of steel elements and the optimal rounded dimensions of the concrete bases.</p> ]]> Minlp Optimization of a Cantilever Roof Structure tomaž žula stojan kravanja doi: 10.2495/CMEM-V7-N3-236-245 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 236 10.2495/CMEM-V7-N3-236-245 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-236-245 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-226-235 Environmental concerns related to global warming and ozone depletion triggered the introduction of the fourth generation of thermofluids. amongst the recently introduced thermofluids, one of the most promising fourth generation of thermofluids are hydrofluoroethers (HFEs). HFEs have zero ozone depletion potential and have a lower global warming potential as compared to widely used thermofluids. The type of thermofluid used in a thermodynamic cycle directly affects the tribological performance of the system. HFEs have been reported to have good thermodynamic properties. The overall tribological performance of HFEs however have to be investigated in detail in order to fully assess the mechani- cal behaviour of interacting components utilizing these thermofluids. This study is concerned with the experimental test rig design modifications and commissioning to conduct tribological testing with HFEs as lubricants. This article covers the experimental test rig design and setup. Experiments to analyse the frictional force, the coefficient of friction and wear by using hydrofluororther-7000 (hfE-347mcc3) as lubrication medium have been conducted. Industrial applications were simulated by varying test condi- tions and the results are presented in this paper. <![CDATA[ <p>Environmental concerns related to global warming and ozone depletion triggered the introduction of the fourth generation of thermofluids. amongst the recently introduced thermofluids, one of the most promising fourth generation of thermofluids are hydrofluoroethers (HFEs). HFEs have zero ozone depletion potential and have a lower global warming potential as compared to widely used thermofluids. The type of thermofluid used in a thermodynamic cycle directly affects the tribological performance of the system. HFEs have been reported to have good thermodynamic properties. The overall tribological performance of HFEs however have to be investigated in detail in order to fully assess the mechani- cal behaviour of interacting components utilizing these thermofluids. This study is concerned with the experimental test rig design modifications and commissioning to conduct tribological testing with HFEs as lubricants. This article covers the experimental test rig design and setup. Experiments to analyse the frictional force, the coefficient of friction and wear by using hydrofluororther-7000 (hfE-347mcc3) as lubrication medium have been conducted. Industrial applications were simulated by varying test condi- tions and the results are presented in this paper.</p> ]]> Novel Experimental Setup to Assess Surfaces in Tribo-Contact Lubricated by the Next Generation of Environmentally Friendly Thermofluids muhammad usman bhutta zulfiqar ahmad khan nigel garland doi: 10.2495/CMEM-V7-N3-226-235 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 226 10.2495/CMEM-V7-N3-226-235 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-226-235 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-212-225 The construction of expanded polystyrene (EPS) dome houses requires intricate moulding equipment. A further obstacle in the accessibility of EPS dome houses is the minimum order placed by suppliers. Japan Dome House Company supplies dome houses at a minimum order of three-hundred units. This publication analyses how a miniature EPS dome house model created using a hot-wire system matches the claimed performance features of a factory-manufactured EPS Dome house. The purpose of this research is to investigate whether EPS dome houses can be created on an individual basis through a change in the construction method in order to increase product accessibility. All EPS dome pieces were carved over a period of 5 days. EPS pieces were assembled and left exposed to the elements since the main method of analysis of the live model was through exposure; particularly against rain and wind experienced within the jurisdiction of Pietermaritzburg, South Africa. Analysis of the live model was studied in conjunction with the compression, flexural and thermal qualities of EPS under laboratory conditions. With wind speeds of 39 km/h and a rainfall intensity of 28 mm, the model was still found to be in its original state of composure after three months even without having been permanently anchored to the ground. Observation of the model revealed that it is possible to successfully re-create an EPS dome house without complex moulding equipment. However, a compressive strength test on EPS revealed that the compressive qualities of EPS are significantly lower than that of conventional materials such as clay bricks. Contrary to what may be believed, a thermo-gravimetric analysis of three different densities (15, 20 and 30 kg/m3) of EPS revealed that as the density of EPS increases, the maximum degradation value decreases. Dome houses are pre-fabricated and therefore have a reduced impact on the environment. <![CDATA[ <p>The construction of expanded polystyrene (EPS) dome houses requires intricate moulding equipment. A further obstacle in the accessibility of EPS dome houses is the minimum order placed by suppliers. Japan Dome House Company supplies dome houses at a minimum order of three-hundred units. This publication analyses how a miniature EPS dome house model created using a hot-wire system matches the claimed performance features of a factory-manufactured EPS Dome house. The purpose of this research is to investigate whether EPS dome houses can be created on an individual basis through a change in the construction method in order to increase product accessibility. All EPS dome pieces were carved over a period of 5 days. EPS pieces were assembled and left exposed to the elements since the main method of analysis of the live model was through exposure; particularly against rain and wind experienced within the jurisdiction of Pietermaritzburg, South Africa. Analysis of the live model was studied in conjunction with the compression, flexural and thermal qualities of EPS under laboratory conditions. With wind speeds of 39 km/h and a rainfall intensity of 28 mm, the model was still found to be in its original state of composure after three months even without having been permanently anchored to the ground. Observation of the model revealed that it is possible to successfully re-create an EPS dome house without complex moulding equipment. However, a compressive strength test on EPS revealed that the compressive qualities of EPS are significantly lower than that of conventional materials such as clay bricks. Contrary to what may be believed, a thermo-gravimetric analysis of three different densities (15, 20 and 30 kg/m3) of EPS revealed that as the density of EPS increases, the maximum degradation value decreases. Dome houses are pre-fabricated and therefore have a reduced impact on the environment.</p> ]]> A Laboratory Investigation and an Appraisal of the Viability of Expanded Polystyrene Dwellings bonke mncwango dhiren allopi doi: 10.2495/CMEM-V7-N3-212-225 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 0 10.2495/CMEM-V7-N3-212-225 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-212-225 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-201-211 In this study, a novel simulation code to predict three-dimensional (3D) neurogenesis was developed by using a multilayered cellular automaton (CA) method. Recently, the induced pluripotent stem cell therapy treatments have rapidly grown up as an attractive repair and regeneration technologies for damaged central nervous system (CNS). However, understanding the repair mechanism and developing a numerical analysis code to predict CNS neurogenesis process have ultimate difficulties because more than hundreds of billions of neurons connect each other, and it is almost impossible to analyze the neurogenesis evolution process. Especially, the axonal extension to generate the neural network system is extremely difficult. In this study, based on the phase contrast microscopy (PCM) and the multiphoton microscope (MPM) observations of two-dimensional (2D) and 3D nerve cell network generation of the pheochromocytoma cells (PC12), a novel simulation code to predict the CNS morphogenesis was developed. At first, time-lapse PCM observations have been executed to understand the nerve cell axonal extension and branching. Secondly, 3D representative volume elements (RVEs) of cortex were derived by using Nissl-stained cerebral cortex images. Finally, a 3D CA simulation code for neurogenesis was developed based on multilayered CA algorithms, such as the dendrites outgrowth, an axon selection from dendrites, the extension enhancement induced by the nerve growth factor (NGF), and the branching caused by microtubule collapse under the effect of Netrin-1. Our newly developed CA simulation code was confirmed as a comprehensive code to predict neurogenesis processes through comparison with PCM and MPM observation results. <![CDATA[ <p>In this study, a novel simulation code to predict three-dimensional (3D) neurogenesis was developed by using a multilayered cellular automaton (CA) method. Recently, the induced pluripotent stem cell therapy treatments have rapidly grown up as an attractive repair and regeneration technologies for damaged central nervous system (CNS). However, understanding the repair mechanism and developing a numerical analysis code to predict CNS neurogenesis process have ultimate difficulties because more than hundreds of billions of neurons connect each other, and it is almost impossible to analyze the neurogenesis evolution process. Especially, the axonal extension to generate the neural network system is extremely difficult. In this study, based on the phase contrast microscopy (PCM) and the multiphoton microscope (MPM) observations of two-dimensional (2D) and 3D nerve cell network generation of the pheochromocytoma cells (PC12), a novel simulation code to predict the CNS morphogenesis was developed. At first, time-lapse PCM observations have been executed to understand the nerve cell axonal extension and branching. Secondly, 3D representative volume elements (RVEs) of cortex were derived by using Nissl-stained cerebral cortex images. Finally, a 3D CA simulation code for neurogenesis was developed based on multilayered CA algorithms, such as the dendrites outgrowth, an axon selection from dendrites, the extension enhancement induced by the nerve growth factor (NGF), and the branching caused by microtubule collapse under the effect of Netrin-1. Our newly developed CA simulation code was confirmed as a comprehensive code to predict neurogenesis processes through comparison with PCM and MPM observation results.</p> ]]> Development of a Novel Simulation Code to Predict Three-Dimensional Neurogenesis by Using Multilayered Cellular Automaton eiji nakamachi akie nakayama takehiko yamamoto yusuke morita hidetoshi sakamoto doi: 10.2495/CMEM-V7-N3-201-211 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 3 Article 201 10.2495/CMEM-V7-N3-201-211 https://www.acadlore.com/article/IJCMEM/2019_7_3/CMEM-V7-N3-201-211 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-93-105 The objective of this work is to gain insight into the process and development of a method for obtaining optimum design shapes for non-lifting aerodynamic struts while employing an interactive viscous- potential flow model for a range of airfoil reynolds numbers. This was done for axially loaded struts with constant cross-sectional area as well as struts loaded in bending with a fixed cross-sectional moment of inertia. The optimization sought the airfoil shape that resulted in minimum drag. The flow field was obtained by using a panel method that was iteratively coupled to a boundary layer solver. The viscous solver used was to model the boundary layer and was based on the zero-equation, Cebeci- Smith turbulence model. The main flow field was computed using a panel method. The airfoil shape was described using a bezier-PArSEC shape parameterization and optimization of the shape param- eters was obtained using differential evolution. The numerical approach of the flow field solver and the simplicity of the genetic algorithm allowed for these results to be obtained in an acceptable timely manner. This paper will present the results of a number of cases and discuss all of the issues that arose. While one can have confidence in the results, limitations and the need for future work were also exposed. The limitations occurred in this thesis were due to the limitations of the boundary layer flow field solver. This solver did not allow airfoils with significant thickness to be evaluated thus restricting the solution space to thin airfoils. It was observed that future work on dealing with separation modelling needs to be done to allow improved certainty of the optimization. <![CDATA[ <p>The objective of this work is to gain insight into the process and development of a method for obtaining optimum design shapes for non-lifting aerodynamic struts while employing an interactive viscous- potential flow model for a range of airfoil reynolds numbers. This was done for axially loaded struts with constant cross-sectional area as well as struts loaded in bending with a fixed cross-sectional moment of inertia. The optimization sought the airfoil shape that resulted in minimum drag. The flow field was obtained by using a panel method that was iteratively coupled to a boundary layer solver. The viscous solver used was to model the boundary layer and was based on the zero-equation, Cebeci- Smith turbulence model. The main flow field was computed using a panel method. The airfoil shape was described using a bezier-PArSEC shape parameterization and optimization of the shape param- eters was obtained using differential evolution. The numerical approach of the flow field solver and the simplicity of the genetic algorithm allowed for these results to be obtained in an acceptable timely manner. This paper will present the results of a number of cases and discuss all of the issues that arose. While one can have confidence in the results, limitations and the need for future work were also exposed. The limitations occurred in this thesis were due to the limitations of the boundary layer flow field solver. This solver did not allow airfoils with significant thickness to be evaluated thus restricting the solution space to thin airfoils. It was observed that future work on dealing with separation modelling needs to be done to allow improved certainty of the optimization.</p> ]]> A Study of the Viscous Optimization of the Shape of a Non-Lifting Strut r. w. derksen j. g. veenendaal doi: 10.2495/CMEM-V7-N2-93-105 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 93 10.2495/CMEM-V7-N2-93-105 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-93-105 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-181-192 Not only is the energy efficiency of buildings nowadays becoming more and more important; the legislative requirements, the people’s awareness of the environmental questions and their thermal com- fort expectations are also on a much higher level. all of these issues can be addressed by making the building envelope more thermally resistant. however, with the traditional thermal insulation materials the thickness of thermal insulation layers is already at the viable limits. Therefore, the development of new, more efficient thermal insulation products with a higher thermal resistance is highly promoted. Preliminary research results can be applied to models to develop and confirm the conceptual designs of such new materials. In this paper, an analysis of thermal performance is presented for a novel thermal insulation consisting of graphite polystyrene (gPS) matrix with cavities filled with an insulative gas, and a protective sheath to prevent it from leaking. bearing in mind the suitability for later production, differ- ent configurations of the assembly were considered, regarding the matrix geometry, the type of the gas filling, and the surface emissivity of the cavities. a range of numerical simulations of heat transfer was conducted to determine the efficiency of different designs in reducing the conductive, the convective, and the radiative heat transfer. advantages, limitations and some detailed parameters of the proposed design concepts were determined, which were then used for optimisation. The analysis of the results indicates that the equivalent thermal conductance of a gPS panel can be significantly reduced by the introduction of gas-filled cavities. The reduction is highly dependent on the type of the gas filling (ther- mal conductivity, viscosity, specific heat, etc.), the size of the cavities, and the cavity surface emissivity. <![CDATA[ <p>Not only is the energy efficiency of buildings nowadays becoming more and more important; the legislative requirements, the people’s awareness of the environmental questions and their thermal com- fort expectations are also on a much higher level. all of these issues can be addressed by making the building envelope more thermally resistant. however, with the traditional thermal insulation materials the thickness of thermal insulation layers is already at the viable limits. Therefore, the development of new, more efficient thermal insulation products with a higher thermal resistance is highly promoted. Preliminary research results can be applied to models to develop and confirm the conceptual designs of such new materials. In this paper, an analysis of thermal performance is presented for a novel thermal insulation consisting of graphite polystyrene (gPS) matrix with cavities filled with an insulative gas, and a protective sheath to prevent it from leaking. bearing in mind the suitability for later production, differ- ent configurations of the assembly were considered, regarding the matrix geometry, the type of the gas filling, and the surface emissivity of the cavities. a range of numerical simulations of heat transfer was conducted to determine the efficiency of different designs in reducing the conductive, the convective, and the radiative heat transfer. advantages, limitations and some detailed parameters of the proposed design concepts were determined, which were then used for optimisation. The analysis of the results indicates that the equivalent thermal conductance of a gPS panel can be significantly reduced by the introduction of gas-filled cavities. The reduction is highly dependent on the type of the gas filling (ther- mal conductivity, viscosity, specific heat, etc.), the size of the cavities, and the cavity surface emissivity. </p> ]]> Novel Thermal Insulation with Gas-filled Cavities – Assessment of Thermal Performance of Different Designs Based on Numerical Simulations of Heat Transfer miha jukić sabina jordan danijel lisičić doi: 10.2495/CMEM-V7-N2-181-192 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 181 10.2495/CMEM-V7-N2-181-192 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-181-192 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-167-180 This paper is concerned with the evaluation of effective material properties of wood. Since both mechanical loading and climatic changes play a crucial role in the prediction of wood response, we consider not only stiffness, but also non-mechanical properties driving the heat and moisture transport and thus indirectly addressing the swelling and shrinkage properties of wood. In this regard, classical micromechanical models as well as numerical simulations based on the Extended Finite Element Method are examined. A special attention is devoted to the influence of microstructural details of the porous phase. To that end, the X-ray computational micro-tomography is adopted when seeking for information beyond the volume fraction of phases that can be identified at various levels of a hierarchical arrangement of wood. A spruce wood is selected as one particular example to compare individual computational approaches. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper is concerned with the evaluation of effective material properties of wood. Since both mechanical loading and climatic changes play a crucial role in the prediction of wood response, we consider not only stiffness, but also non-mechanical properties driving the heat and moisture transport and thus indirectly addressing the swelling and shrinkage properties of wood. In this regard, classical micromechanical models as well as numerical simulations based on the Extended Finite Element Method are examined. A special attention is devoted to the influence of microstructural details of the porous phase. To that end, the X-ray computational micro-tomography is adopted when seeking for information beyond the volume fraction of phases that can be identified at various levels of a hierarchical arrangement of wood. A spruce wood is selected as one particular example to compare individual computational approaches.</span></p> ]]> Effective Material Properties of Wood Based on Homogenization m. šejnoha l. kucíková j. vorel j. sýkora w. p. de wilde doi: 10.2495/CMEM-V7-N2-167-180 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 167 10.2495/CMEM-V7-N2-167-180 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-167-180 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-154-166 The hydrocarbon leaks from process systems potentially lead to hazardous consequences with regard to human safety, environmental pollution and valuable assets. The hydrocarbon leaks may be gas leaks, liquid leaks or multiphase leaks. The gas leaks have the highest potential of damage due to explosion accidents. both gas and oil leaks can create long-lasting fires threatening personnel safety and structural integrity of process plants and offshore platforms. One common method for limiting the consequences associated with a process emergency is the rapid depressurization or blowdown of pressurized process systems. There is experimental evidence that the assumption of thermodynamic equilibrium is not appropriate during rapid depressurization, since the two phases show an independent temperature evolution. The current work proposes a model for the simulation of the blowdown of vessels containing two-phase (gas–liquid) hydrocarbon fluids, considering partial phase equilibrium between phases. Two phases may be present either already at the beginning of the blowdown process (for instance in gas– liquid separators) or as the liquid is formed from flashing of the vapour due to the cooling induced by pressure decrease. In addition, the transient behaviour of hydrocarbon leaks from pressurized process systems during depressurization is also included in the model providing the inputs for risk assessments. The model is based on a compositional approach, and it takes into account coupled effects of internal heat and mass transfer processes, as well as heat transfer with the vessel wall and the external environ- ment. The vapour liquid equilibria calculations are performed using dynamic link library provided by the comprehensive pressure volume temperature and physical properties package ‘Multiflash’. Numerical simulations show a generally good agreement with experimental measurements. <![CDATA[ <p>The hydrocarbon leaks from process systems potentially lead to hazardous consequences with regard to human safety, environmental pollution and valuable assets. The hydrocarbon leaks may be gas leaks, liquid leaks or multiphase leaks. The gas leaks have the highest potential of damage due to explosion accidents. both gas and oil leaks can create long-lasting fires threatening personnel safety and structural integrity of process plants and offshore platforms. One common method for limiting the consequences associated with a process emergency is the rapid depressurization or blowdown of pressurized process systems. There is experimental evidence that the assumption of thermodynamic equilibrium is not appropriate during rapid depressurization, since the two phases show an independent temperature evolution. The current work proposes a model for the simulation of the blowdown of vessels containing two-phase (gas–liquid) hydrocarbon fluids, considering partial phase equilibrium between phases. Two phases may be present either already at the beginning of the blowdown process (for instance in gas– liquid separators) or as the liquid is formed from flashing of the vapour due to the cooling induced by pressure decrease. In addition, the transient behaviour of hydrocarbon leaks from pressurized process systems during depressurization is also included in the model providing the inputs for risk assessments. The model is based on a compositional approach, and it takes into account coupled effects of internal heat and mass transfer processes, as well as heat transfer with the vessel wall and the external environ- ment. The vapour liquid equilibria calculations are performed using dynamic link library provided by the comprehensive pressure volume temperature and physical properties package ‘Multiflash’. Numerical simulations show a generally good agreement with experimental measurements.</p> ]]> Modelling of Hydrocarbon Gas and Liquid Leaks from Pressurized Process Systems anand bahuguni amaranath s. kumara knut e. t. giljarhus doi: 10.2495/CMEM-V7-N2-154-166 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 154 10.2495/CMEM-V7-N2-154-166 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-154-166 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-142-153 Overflows in the ocean occur when dense water flows down a continental slope into less dense ambient water. It is important to study idealized and small-scale models, which allow for confidence and control of parameters. The work presented here is a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Physical parameters are varied, including the Coriolis parameter, the inflow density, and the inflow volumetric flow rate. Laboratory experiments are conducted using a rotating square tank and high-resolution camera mounted on the table in the rotating reference frame. Video results are digitized in order to compare directly to numeri- cal simulations. The MIT General Circulation Model (MITgcm), a three-dimensional ocean model, is used for the direct numerical simulations corresponding to the specific laboratory experiments. It was found that the MITgcm was not a good match to laboratory experiments when physical parameters fell within the high eddy activity regime. However, a more extensive resolution study is needed to understand this fully. The MITgcm simulations did provide a good qualitative and quantitative match to laboratory experiments run in a low eddy activity regime. In all cases, the MITgcm simulations had more eddy activity than the laboratory experiments. <![CDATA[ <p>Overflows in the ocean occur when dense water flows down a continental slope into less dense ambient water. It is important to study idealized and small-scale models, which allow for confidence and control of parameters. The work presented here is a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Physical parameters are varied, including the Coriolis parameter, the inflow density, and the inflow volumetric flow rate. Laboratory experiments are conducted using a rotating square tank and high-resolution camera mounted on the table in the rotating reference frame. Video results are digitized in order to compare directly to numeri- cal simulations. The MIT General Circulation Model (MITgcm), a three-dimensional ocean model, is used for the direct numerical simulations corresponding to the specific laboratory experiments. It was found that the MITgcm was not a good match to laboratory experiments when physical parameters fell within the high eddy activity regime. However, a more extensive resolution study is needed to understand this fully. The MITgcm simulations did provide a good qualitative and quantitative match to laboratory experiments run in a low eddy activity regime. In all cases, the MITgcm simulations had more eddy activity than the laboratory experiments.</p> ]]> The Effect of Numerical Parameters on Eddies in Oceanic Overflows: A Laboratory and Numerical Study shanon m. reckinger thomas h. gibson fred m. hohman theresa j. morrison scott j. reckinger mateus carvalho doi: 10.2495/CMEM-V7-N2-142-153 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 142 10.2495/CMEM-V7-N2-142-153 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-142-153 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-130-141 Understanding the disturbances introduced by cavitation inside spray nozzles is important, when simulating the spray formation of highly viscous liquids. In this paper, a new model for cavitation-induced primary break-up is proposed, which is able to map the influence of cavitating nozzle flow on spray formation. Detailed experimental and numerical investigations of the viscous nozzle flow have been performed in order to develop an improved primary break-up model [1]. The proposed model describes the transition from the flow inside the nozzle, modelled using a homogeneous equilibrium model (HEM) method, to the first primary droplets modelled using a Eulerian–Lagrangian method. Thus, providing the boundary conditions for the calculation of the secondary break-up and spray formation. The nozzle exit is divided into a definite number of patches. Liquid momentum and vapor volume fraction from each patch are used to initialize the primary droplets. The model has been implemented in the open-source CFD software package OpenFOAM and validation has been done using high-speed shadow graphic imaging. The simulated spray tip penetration and spray cone angle at the near-nozzle region show a good agreement with the experiment results. <![CDATA[ <p>Understanding the disturbances introduced by cavitation inside spray nozzles is important, when simulating the spray formation of highly viscous liquids. In this paper, a new model for cavitation-induced primary break-up is proposed, which is able to map the influence of cavitating nozzle flow on spray formation. Detailed experimental and numerical investigations of the viscous nozzle flow have been performed in order to develop an improved primary break-up model [1]. The proposed model describes the transition from the flow inside the nozzle, modelled using a homogeneous equilibrium model (HEM) method, to the first primary droplets modelled using a Eulerian–Lagrangian method. Thus, providing the boundary conditions for the calculation of the secondary break-up and spray formation. The nozzle exit is divided into a definite number of patches. Liquid momentum and vapor volume fraction from each patch are used to initialize the primary droplets. The model has been implemented in the open-source CFD software package OpenFOAM and validation has been done using high-speed shadow graphic imaging. The simulated spray tip penetration and spray cone angle at the near-nozzle region show a good agreement with the experiment results.</p> ]]> Coupling Method for Internal Nozzle Flow and the Spray Formation for Viscous Liquids rathesan ravendran benny endelt jesper de claville christiansen peter jensen martin theile ibrahim najjar doi: 10.2495/CMEM-V7-N2-130-141 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 130 10.2495/CMEM-V7-N2-130-141 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-130-141 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-118-129 This paper deals with the economic optimization of high-performance post-tensioned concrete box-girder pedestrian bridges. To this end, a program analyzes and evaluates the structural restrictions following Spanish codes for structural concrete and bridge design loads. This problem includes 33 discrete design variables that define the geometry, the concrete, the reinforcing steel bars and the post-tensioned steel. Various acceptance criteria are proposed to modify a variant of the simulated annealing algorithm with a neighborhood move based on the mutation operator from the genetic algo- rithms (SAMO). An objective methodology based on the extreme value theory is used to determine the number of experimental tests required to provide a solution with user-defined accuracy as compared to a global optimum solution. Results indicate that the local optima found by SAMO2 fits a three- parameter Weibull distribution and improves the cost results for this structural problem. The minimum value obtained by SAMO2 differed just 0.34% compared to the theoretical minimum value so that, from the structural engineering perspective, the divergence was small enough to be accepted. High-strength concrete performance was further studied in a concrete strength parametric study to acquire more evidence-based knowledge on its implications for economic efficiency. Finally, the study showed that high-strength concrete decreases the cost by 4.5% and the amount of concrete by 26%. <![CDATA[ <p>This paper deals with the economic optimization of high-performance post-tensioned concrete box-girder pedestrian bridges. To this end, a program analyzes and evaluates the structural restrictions following Spanish codes for structural concrete and bridge design loads. This problem includes 33 discrete design variables that define the geometry, the concrete, the reinforcing steel bars and the post-tensioned steel. Various acceptance criteria are proposed to modify a variant of the simulated annealing algorithm with a neighborhood move based on the mutation operator from the genetic algo- rithms (SAMO). An objective methodology based on the extreme value theory is used to determine the number of experimental tests required to provide a solution with user-defined accuracy as compared to a global optimum solution. Results indicate that the local optima found by SAMO2 fits a three- parameter Weibull distribution and improves the cost results for this structural problem. The minimum value obtained by SAMO2 differed just 0.34% compared to the theoretical minimum value so that, from the structural engineering perspective, the divergence was small enough to be accepted. High-strength concrete performance was further studied in a concrete strength parametric study to acquire more evidence-based knowledge on its implications for economic efficiency. Finally, the study showed that high-strength concrete decreases the cost by 4.5% and the amount of concrete by 26%.</p> ]]> Optimization of High-Performance Concrete Post-Tensioned Box-Girder Pedestrian Bridges víctor yepes eloy pérez-lópez tatiana garcía-segura julián alcalá doi: 10.2495/CMEM-V7-N2-118-129 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 118 10.2495/CMEM-V7-N2-118-129 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-118-129 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-106-117 The importance of micro-shock tubes is growing in line with recent developments of microscale technology for products like micro-heat engines and micro-propulsion systems. The flow dynamics within a micro-shock tube are different from those found in a macro shock tube, and knowledge of these dynamics is not as yet well established, as the flow within these tubes includes extra physics namely rarefaction and complex effects due to viscosity. Studies have recently been made with assumed initial condition of instantaneous diaphragm rupture producing centred shock and expansion waves. However, for a real case, the diaphragm ruptures over a finite time causing a period of partial rupture and this will change the shock characteristics. The work here reports on a series of axisymmetric numerical simulations carried out to calculate the influence of an initial finite-time diaphragm rupture. Rarefaction effects were taken into account by the use of Maxwell’s slip velocity and temperature conditions. Use of an initial finite-time diaphragm rupture boundary condition causes the forming of a non-centred shock wave downstream of the diaphragm, and, the shock propagation distance is considerably reduced by use of the finite-time rupture process. <![CDATA[ <p>The importance of micro-shock tubes is growing in line with recent developments of microscale technology for products like micro-heat engines and micro-propulsion systems. The flow dynamics within a micro-shock tube are different from those found in a macro shock tube, and knowledge of these dynamics is not as yet well established, as the flow within these tubes includes extra physics namely rarefaction and complex effects due to viscosity. Studies have recently been made with assumed initial condition of instantaneous diaphragm rupture producing centred shock and expansion waves. However, for a real case, the diaphragm ruptures over a finite time causing a period of partial rupture and this will change the shock characteristics. The work here reports on a series of axisymmetric numerical simulations carried out to calculate the influence of an initial finite-time diaphragm rupture. Rarefaction effects were taken into account by the use of Maxwell’s slip velocity and temperature conditions. Use of an initial finite-time diaphragm rupture boundary condition causes the forming of a non-centred shock wave downstream of the diaphragm, and, the shock propagation distance is considerably reduced by use of the finite-time rupture process.</p> ]]> The Influence of Finite Rupture Times on Flow Dynamics within Micro-Shock Tubes desmond adair abilkaiyr mukhambetiyar martin jaeger michael malin doi: 10.2495/CMEM-V7-N2-106-117 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 2 Article 106 10.2495/CMEM-V7-N2-106-117 https://www.acadlore.com/article/IJCMEM/2019_7_2/CMEM-V7-N2-106-117 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-68-78 Vortical structures have been observed to develop in electrically driven fluid motion at the micro/nano scale, but no coherent theory has been put foreword in the literature to explain such a development. The present paper gives several results in a theory based upon the classical field equations. In particular, it is shown that the origin of vorticity production resides in the applied electric field interacting with any ion concentration gradients present in the fluid as defined by the vorticity equation. This is in addition to any viscous layer vorticity diffusion that may also exist in the flow. <![CDATA[ <p>Vortical structures have been observed to develop in electrically driven fluid motion at the micro/nano scale, but no coherent theory has been put foreword in the literature to explain such a development. The present paper gives several results in a theory based upon the classical field equations. In particular, it is shown that the origin of vorticity production resides in the applied electric field interacting with any ion concentration gradients present in the fluid as defined by the vorticity equation. This is in addition to any viscous layer vorticity diffusion that may also exist in the flow.</p> ]]> Micro/Nano Flows: Vorticity Generation trevor h. moulden doi: 10.2495/CMEM-V7-N1-68-78 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 68 10.2495/CMEM-V7-N1-68-78 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-68-78 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-57-67 This research investigates the unsteady free convective flow of a viscous incompressible fluid from a differentially heated rotating sphere. The flow is assumed to remain laminar and to possess equatorial and azimuthal symmetry. The governing Navier-Stokes and energy equations are posed in terms of a scaled stream function - vorticity formulation and are solved subject to no-slip and specified surface temperature conditions. At t = 0 an impulsive heat flux is applied in the form of a jump in surface temperature. An asymptotic solution valid for large Grashof numbers and small times following the impulsive startup is constructed. Two small parameters have been identified and based on this the flow variables are expanded in a double series in powers of these parameters. The non-zero leading-order terms in the asymptotic expansions have been determined analytically and the corresponding heat transfer coefficient has been found. Future work will involve obtaining numerical solutions. <![CDATA[ <p>This research investigates the unsteady free convective flow of a viscous incompressible fluid from a differentially heated rotating sphere. The flow is assumed to remain laminar and to possess equatorial and azimuthal symmetry. The governing Navier-Stokes and energy equations are posed in terms of a scaled stream function - vorticity formulation and are solved subject to no-slip and specified surface temperature conditions. At t = 0 an impulsive heat flux is applied in the form of a jump in surface temperature. An asymptotic solution valid for large Grashof numbers and small times following the impulsive startup is constructed. Two small parameters have been identified and based on this the flow variables are expanded in a double series in powers of these parameters. The non-zero leading-order terms in the asymptotic expansions have been determined analytically and the corresponding heat transfer coefficient has been found. Future work will involve obtaining numerical solutions.</p> ]]> An Analytical Study of the Early Stages of Unsteady Free Convective Flow from a Differentially Heated Rotating Sphere at Large Grashof Numbers s. j. d. d’alessio doi: 10.2495/CMEM-V7-N1-57-67 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 57 10.2495/CMEM-V7-N1-57-67 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-57-67 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-45-56 Solving potential problems, such as those that occur in the analysis of steady-state heat transfer, electrostatics, ideal fluid flow, and groundwater flow, is important in several fields of engineering, science, and applied mathematics. Numerical solution of the relevant governing equations typically involves using techniques such as domain methods (including finite element, finite difference, or finite volume), or boundary element methods (using either real or complex variables). In this paper, the Complex Vari- able Boundary Element method (“CVBEM”) is examined with respect to the use of different types of basis functions in the CVBEM approximation function. Four basis function families are assessed in their solution success in modeling an important benchmark problem in ideal fluid flow; namely, flow around a 90 degree bend. Identical problem domains are used in the examination, and identical degrees of freedom are used in the CVBEM approximation functions. Further, a new computational modeling error is defined and used to compare the results herein; specifically, M = E / N where M is the proposed computational error measure, E is the maximum difference (in absolute value) between approximation and boundary condition value, and N is the number of degrees of freedom used in the approximation. <![CDATA[ <p>Solving potential problems, such as those that occur in the analysis of steady-state heat transfer, electrostatics, ideal fluid flow, and groundwater flow, is important in several fields of engineering, science, and applied mathematics. Numerical solution of the relevant governing equations typically involves using techniques such as domain methods (including finite element, finite difference, or finite volume), or boundary element methods (using either real or complex variables). In this paper, the Complex Vari- able Boundary Element method (“CVBEM”) is examined with respect to the use of different types of basis functions in the CVBEM approximation function. Four basis function families are assessed in their solution success in modeling an important benchmark problem in ideal fluid flow; namely, flow around a 90 degree bend. Identical problem domains are used in the examination, and identical degrees of freedom are used in the CVBEM approximation functions. Further, a new computational modeling error is defined and used to compare the results herein; specifically, M = E / N where M is the proposed computational error measure, E is the maximum difference (in absolute value) between approximation and boundary condition value, and N is the number of degrees of freedom used in the approximation. </p> ]]> Assessment of Complex Variable Basis Functions in the Approximation of Ideal Fluid Flow Problems bryce d. wilkins t. v. hromadka ii anthony n. johnson randy boucher howard d. mcinvale steve horton doi: 10.2495/CMEM-V7-N1-45-56 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 45 10.2495/CMEM-V7-N1-45-56 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-45-56 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-33-44 This study analyses three dimensional fluid flow through horizontal pipelines with three-phase gas- liquid-solid Newtonian fluids by Computational Fluid Dynamics (CFD) simulation. Validating the simulation with experimental data, the study aims to develop a versatile acceptable simulation model that can be used further for different applied cases. An experimental setup is developed in our laboratory to determine slug flow (air-water) through a horizontal pipeline. Air as gas, water as liquid and silica as solid particle is used in this work. ANSYS Fluent version 16.2 is employed to perform the simulation. The Eulerian multiphase model with the Reynolds Stress Model (RSM) turbulence closure is adopted to analyse multiphase fluid flow. Parameters are selected from experimental works to validate the simula- tion. After a good agreement with experimental data, sensitivity analysis is conducted to observe the three phase fluid flow characteristics through horizontal flow. Pressure gradient (pressure drop per unit length) and in situ concentration profile are used as primary parameters. This article provides a clear relationship between the different parameters of three-phase fluid flow through a horizontal pipeline. <![CDATA[ <p>This study analyses three dimensional fluid flow through horizontal pipelines with three-phase gas- liquid-solid Newtonian fluids by Computational Fluid Dynamics (CFD) simulation. Validating the simulation with experimental data, the study aims to develop a versatile acceptable simulation model that can be used further for different applied cases. An experimental setup is developed in our laboratory to determine slug flow (air-water) through a horizontal pipeline. Air as gas, water as liquid and silica as solid particle is used in this work. ANSYS Fluent version 16.2 is employed to perform the simulation. The Eulerian multiphase model with the Reynolds Stress Model (RSM) turbulence closure is adopted to analyse multiphase fluid flow. Parameters are selected from experimental works to validate the simula- tion. After a good agreement with experimental data, sensitivity analysis is conducted to observe the three phase fluid flow characteristics through horizontal flow. Pressure gradient (pressure drop per unit length) and in situ concentration profile are used as primary parameters. This article provides a clear relationship between the different parameters of three-phase fluid flow through a horizontal pipeline. </p> ]]> CFD and Experimental Approach on Three Phase Gas-Liquid-Solid Newtonian Fluid Flow in Horizontal Pipes rasel a sultan serag alfarek m. a. rahman sohrab zendehboudi doi: 10.2495/CMEM-V7-N1-33-44 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 33 10.2495/CMEM-V7-N1-33-44 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-33-44 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-22-32 Pipe lines are useful for transporting water for drinking, irrigation and for fireing over long distances, this pipe lines are called “Transmission line” and are used to carry conveying raw or treated water from a well field or remote storage (large lake, reservoir, etc.,) facility to a treatment plant and/or distribution storage tank. In water-carrying piping systems, dangerous phenomena may occur. One such phenomenon is water hammer.The water hammer has always been an area of study, which has captivated the minds of researchers due to its complex and challenging phenomena. Modeling the phenomenon in real conditions is extremely difficult. Due to the dimensions of the piping systems, conducting research at real scales is impossible. However, thanks to the development of numerical methods, the study of water hammer and its effects can be performed using simulation programs. Unfortunately, the simulation results are not always consistent with the actual course of the phenomenon.One of the parameters that describes the nature of the course of a water hammer is the velocity of propagation of the pressure wave, c, which is called celerity. The transient surge pressure, p, may be calculated from the pressure celerity c, and the sudden change in fluid flow velocity, ∆ v. In a piping system, the value of the pressure wave celerity is not equal to the individual celerity, c, for a single pipeline. Therefore for piping systems for ∆p calculations the equivalent celerity shell be used.This article presents value of the equivalent celerity calculated from equations derived using linear analysis of natural vibrations of the system. For implement of the equations, an algorithm in MATLAB has been developed that allows one to easily calculate the equivalent celerity, ce, for N pipelines connected in series with varying diameter, length and material composition. <![CDATA[ <p>Pipe lines are useful for transporting water for drinking, irrigation and for fireing over long distances, this pipe lines are called “Transmission line” and are used to carry conveying raw or treated water from a well field or remote storage (large lake, reservoir, etc.,) facility to a treatment plant and/or distribution storage tank. In water-carrying piping systems, dangerous phenomena may occur. One such phenomenon is water hammer.</p><p>The water hammer has always been an area of study, which has captivated the minds of researchers due to its complex and challenging phenomena. Modeling the phenomenon in real conditions is extremely difficult. Due to the dimensions of the piping systems, conducting research at real scales is impossible. However, thanks to the development of numerical methods, the study of water hammer and its effects can be performed using simulation programs. Unfortunately, the simulation results are not always consistent with the actual course of the phenomenon.</p><p>One of the parameters that describes the nature of the course of a water hammer is the velocity of propagation of the pressure wave, c, which is called celerity. The transient surge pressure, p, may be calculated from the pressure celerity c, and the sudden change in fluid flow velocity, ∆ v. In a piping system, the value of the pressure wave celerity is not equal to the individual celerity, c, for a single pipeline. Therefore for piping systems for ∆p calculations the equivalent celerity shell be used.</p><p>This article presents value of the equivalent celerity calculated from equations derived using linear analysis of natural vibrations of the system. For implement of the equations, an algorithm in MATLAB has been developed that allows one to easily calculate the equivalent celerity, ce, for N pipelines connected in series with varying diameter, length and material composition.</p> ]]> Use of Equivalent Celerity to Estimate Maximum Pressure Increase in Serial Pipes During Water Hammer - Numerical Simulations in Matlab agnieszka malesińska mariusz rogulski pierfabrizio puntorieri giuseppe barbaro beata kowalska doi: 10.2495/CMEM-V7-N1-22-32 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 22 10.2495/CMEM-V7-N1-22-32 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-22-32 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-14-21 The vulnerability of reinforced concrete structures, which were built in the 1970s, under the effects of an earthquake is one of the major concerns of researchers, because the designs of these structures have been based on regulations, which are no longer valid. The parameters taken into account in this study to idealize the regulatory shortcomings are: low ratio of reinforcement, type of reinforcement and moderate resistance of concrete. The analysis to test these altered structures with one or both of the above parameters is carried out in the non-linear domain from the perspective of analysing their behaviour in an earthquake. In this paper, the modelling strategy is based on finite elements combined with a discretization of the shear wall most stressed by successive thin layers. The estimation of level of performance is achieved using capacity curves under increasing incremental loads; a non-linear characteristic force-displacement relationship can be determined. The results of the numerical model are compared with those of the Algerian seismic code (RPA). Through this comparison, it was found that there is an improvement in terms of displacement, shearing action and ductility. The introduction of confining as a local model makes it possible to refine the numerical model and improve the total behaviour of the structure. A parametric analysis is carried out to highlight the obvious weakness of structures designed and built in the 1970s. <![CDATA[ <p>The vulnerability of reinforced concrete structures, which were built in the 1970s, under the effects of an earthquake is one of the major concerns of researchers, because the designs of these structures have been based on regulations, which are no longer valid. The parameters taken into account in this study to idealize the regulatory shortcomings are: low ratio of reinforcement, type of reinforcement and moderate resistance of concrete. The analysis to test these altered structures with one or both of the above parameters is carried out in the non-linear domain from the perspective of analysing their behaviour in an earthquake. In this paper, the modelling strategy is based on finite elements combined with a discretization of the shear wall most stressed by successive thin layers. The estimation of level of performance is achieved using capacity curves under increasing incremental loads; a non-linear characteristic force-displacement relationship can be determined. The results of the numerical model are compared with those of the Algerian seismic code (RPA). Through this comparison, it was found that there is an improvement in terms of displacement, shearing action and ductility. The introduction of confining as a local model makes it possible to refine the numerical model and improve the total behaviour of the structure. A parametric analysis is carried out to highlight the obvious weakness of structures designed and built in the 1970s.</p> ]]> Non-Linear Behaviour of Structural Walls salima djehaichia rachid lassoued doi: 10.2495/CMEM-V7-N1-14-21 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 14 10.2495/CMEM-V7-N1-14-21 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-14-21 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-1-13 The Complex Variable Boundary Element Method, or CVBEM, was first published in Journal of Numerical Methods in Engineering in year 1984 by authors Hromadka and Guymon [1]. Since that time, several papers and books have been published that present various aspects of the numerical technique as well as advances in the computational method such as extension to three or higher dimensions for arbitrary geometries, nonhomogeneous domains, extension to use of a Hilbert Space setting as well as collocation methods, inclusion of the time derivative via coupling to generalized Fourier series techniques, examination of various families of basis functions including complex monomials, the product of complex polynomials with complex logarithm functions (i.e., the usual CVBEM basis functions), Laurent series expansions, reciprocal of complex monomials, other complex variable analytic functions including exponential and others, as well as linear combinations of these families. Other topics studied and developed include rotation of complex logarithm branch-cuts for extension of the problem computational domain to the exterior of the problem geometry, depiction of computational error in achieving problem boundary conditions by means of the approximate boundary technique, mixed boundary value problems, flow net development and visualization, display of flow field trajectory vectors in two and three dimensions for use in depicting streamlines and flow paths, among other topics. The CVBEM approach has also been extended to solving partial differential equations such as Laplace’s equation, Poisson’s equation, unsteady flow equation, and the wave equation, among other formulations that include sources, sinks and combinations of these equations with mixed boundary conditions.In the current paper, a detailed examination is made of the performance between four families of basis functions in order to assess computational efficiency in problem solving of two dimensional potential problems in a high aspect ratio geometric problem domain. Two selected problems are presented as case studies to demonstrate the different levels of success by each of the four families of examined basis functions. All four families involve basis functions that solve the governing partial differential equation, leaving only the goodness of fit in matching boundary conditions of the boundary value problem as the computational optimization goal. The modeling technique is implemented in computer programs Mathematica and MATLAB. Recommendations are made for future research directions and lessons learned from the current study effort. <![CDATA[ <p>The Complex Variable Boundary Element Method, or CVBEM, was first published in <em>Journal of Numerical Methods in Engineering </em>in year 1984 by authors Hromadka and Guymon [1]. Since that time, several papers and books have been published that present various aspects of the numerical technique as well as advances in the computational method such as extension to three or higher dimensions for arbitrary geometries, nonhomogeneous domains, extension to use of a Hilbert Space setting as well as collocation methods, inclusion of the time derivative via coupling to generalized Fourier series techniques, examination of various families of basis functions including complex monomials, the product of complex polynomials with complex logarithm functions (i.e., the usual CVBEM basis functions), Laurent series expansions, reciprocal of complex monomials, other complex variable analytic functions including exponential and others, as well as linear combinations of these families. Other topics studied and developed include rotation of complex logarithm branch-cuts for extension of the problem computational domain to the exterior of the problem geometry, depiction of computational error in achieving problem boundary conditions by means of the approximate boundary technique, mixed boundary value problems, flow net development and visualization, display of flow field trajectory vectors in two and three dimensions for use in depicting streamlines and flow paths, among other topics. The CVBEM approach has also been extended to solving partial differential equations such as Laplace’s equation, Poisson’s equation, unsteady flow equation, and the wave equation, among other formulations that include sources, sinks and combinations of these equations with mixed boundary conditions.</p><p style="text-align: justify">In the current paper, a detailed examination is made of the performance between four families of basis functions in order to assess computational efficiency in problem solving of two dimensional potential problems in a high aspect ratio geometric problem domain. Two selected problems are presented as case studies to demonstrate the different levels of success by each of the four families of examined basis functions. All four families involve basis functions that solve the governing partial differential equation, leaving only the goodness of fit in matching boundary conditions of the boundary value problem as the computational optimization goal. The modeling technique is implemented in computer programs Mathematica and MATLAB. Recommendations are made for future research directions and lessons learned from the current study effort.</p> ]]> 35 Years of Advancements with the Complex Variable Boundary Element Method noah j. demoes gabriel t. bann bryce d. wilkins theodore v. hromadka ii randy boucher doi: 10.2495/CMEM-V7-N1-1-13 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2019 7 1 Article 1 10.2495/CMEM-V7-N1-1-13 https://www.acadlore.com/article/IJCMEM/2019_7_1/CMEM-V7-N1-1-13 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-989-999 In general, internal cells are required to solve large deformation problems using a conventional boundary element method (BEM). However, in this case, the merit of BEM, which is the ease of data preparation, is lost. Triple-reciprocity BEM enables us to solve elastoplasticity problems with a small plastic deformation. In this study, it is shown that two-dimensional large plastic deformation problems with a friction coefficient can be solved without the use of internal cells, by the triple-reciprocity BEM. Initial stress and strain formulations are adopted and the initial stress or strain distribution is interpolated using boundary integral equations. In this method, only boundary elements are remeshed. A new computer program is developed and used to solve several problems. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In general, internal cells are required to solve large deformation problems using a conventional boundary element method (BEM). However, in this case, the merit of BEM, which is the ease of data preparation, is lost. Triple-reciprocity BEM enables us to solve elastoplasticity problems with a small plastic deformation. In this study, it is shown that two-dimensional large plastic deformation problems with a friction coefficient can be solved without the use of internal cells, by the triple-reciprocity BEM. Initial stress and strain formulations are adopted and the initial stress or strain distribution is interpolated using boundary integral equations. In this method, only boundary elements are remeshed. A new computer program is developed and used to solve several problems.</span></p> ]]> Meshless Large Plastic Deformation Analysis Considering with a Friction Coefficient by Triple-Reciprocity Boundary Element Method yoshihiro ochiai doi: 10.2495/CMEM-V6-N6-989-999 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 989 10.2495/CMEM-V6-N6-989-999 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-989-999 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-976-988 The paper presents a fluid-structure interaction analysis of fuel tanks with cylindrical and spherical compartments partially filled with a liquid. The compound shell of revolution is considered as a con- tainer model. The shell is supposed to be thin, so the Kirchhoff–Love linear theory hypotheses are applied. The liquid is an ideal and incompressible one. Its properties and filling levels may be different within each compartment. The shell vibrations coupled with liquid sloshing under the force of gravity have been considered. The tank structure is modelled by a finite element method, whereas liquid sloshing in the compartments is described by a boundary element method. A system of singular integral equations is obtained for evaluating the fluid pressure. At the first stage, both spherical and cylindrical fluid-filled unconnected rigid shells are considered. Different filling levels as well as small radii of free surfaces are taken into account in problems of liquid sloshing in spherical shells. The sloshing frequencies in the presence of complete or partially covered free surfaces are determined for cylindrical shells. The boundary element method has proven to be effective and accurate in all the problems considered. At the second stage, the natural frequencies and modes of the dual compartment tank are obtained including sloshing, elasticity, and gravity effects. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The paper presents a fluid-structure interaction analysis of fuel tanks with cylindrical and spherical compartments partially filled with a liquid. The compound shell of revolution is considered as a con- tainer model. The shell is supposed to be thin, so the Kirchhoff–Love linear theory hypotheses are applied. The liquid is an ideal and incompressible one. Its properties and filling levels may be different within each compartment. The shell vibrations coupled with liquid sloshing under the force of gravity have been considered. The tank structure is modelled by a finite element method, whereas liquid sloshing in the compartments is described by a boundary element method. A system of singular integral equations is obtained for evaluating the fluid pressure. At the first stage, both spherical and cylindrical fluid-filled unconnected rigid shells are considered. Different filling levels as well as small radii of free surfaces are taken into account in problems of liquid sloshing in spherical shells. The sloshing frequencies in the presence of complete or partially covered free surfaces are determined for cylindrical shells. The boundary element method has proven to be effective and accurate in all the problems considered. At the second stage, the natural frequencies and modes of the dual compartment tank are obtained including sloshing, elasticity, and gravity effects.</span></p> ]]> Coupled BEM and FEM Analysis of Fluid-Structure Interaction in Dual Compartment Tanks vasyl v. gnitko kyryl g. degtyariov vitaly v. naumenko elena a. strelnikova doi: 10.2495/CMEM-V6-N6-976-988 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 976 10.2495/CMEM-V6-N6-976-988 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-976-988 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-965-975 The paper reviews the collocation boundary element method (BEM) exactly as it has been originally proposed on the basis of a weighted residuals statement that leads to Somigliana’s identity, but with two subtle conceptual improvements for a generally curved boundary: (a) the interpolation function for normal fluxes or traction forces (for potential or elasticity problems) must be redefined and (b) only Gauss-Legendre quadrature turns out to be required if the numerical integration issues are mathematically adequately stated. A simple, unified code is proposed – as presently shown for 2D problems – to arrive at arbitrarily high computational accuracy of the constituent matrices as well as of results at internal points independently from how convoluted a problem’s topology may be (but given the representation limitations of a discretization mesh). In fact, the higher the effect of a quasi-singularity may be, as for an internal point infinitely close to the boundary, the more accurate a result is achievable with just a few number of quadrature points. A collateral, but not less relevant, outcome of the pro- posed developments is that regularization methods, special quadrature schemes and so many methods that intend to conceptually deviate from the originally stated BEM as an attempt to offer numerical improvements are actually unnecessary (they are in most cases just misleading). Moreover, the inaccurate, albeit popular constant element is actually not simpler to deal with than high-order elements. Owing to space restrictions, most of the detailed developments as well as the hopefully very convincing numerical results deal with potential problems, although the more general problem of elasticity is adequately posed and assessed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The paper reviews the collocation boundary element method (BEM) exactly as it has been originally proposed on the basis of a weighted residuals statement that leads to Somigliana’s identity, but with two subtle conceptual improvements for a generally curved boundary: (a) the interpolation function for normal fluxes or traction forces (for potential or elasticity problems) must be redefined and (b) only Gauss-Legendre quadrature turns out to be required if the numerical integration issues are mathematically adequately stated. A simple, unified code is proposed – as presently shown for 2D problems – to arrive at arbitrarily high computational accuracy of the constituent matrices as well as of results at internal points independently from how convoluted a problem’s topology may be (but given the representation limitations of a discretization mesh). In fact, the higher the effect of a quasi-singularity may be, as for an internal point infinitely close to the boundary, the more accurate a result is achievable with just a few number of quadrature points. A collateral, but not less relevant, outcome of the pro- posed developments is that regularization methods, special quadrature schemes and so many methods that intend to conceptually deviate from the originally stated BEM as an attempt to offer numerical improvements are actually unnecessary (they are in most cases just misleading). Moreover, the inaccurate, albeit popular constant element is actually not simpler to deal with than high-order elements. Owing to space restrictions, most of the detailed developments as well as the hopefully very convincing numerical results deal with potential problems, although the more general problem of elasticity is adequately posed and assessed.</span></p> ]]> The Collocation Boundary Element Method Revisited: Perfect Code for 2D Problems ney augusto dumont doi: 10.2495/CMEM-V6-N6-965-975 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 965 10.2495/CMEM-V6-N6-965-975 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-965-975 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1182-1191 The paper revisits the use of a surface equivalence theorem in deriving the surface integral equation (SIE) based formulation for a homogeneous bio-electromagnetics problem. The vector analog of Green’s 2nd identity is used to obtain the expression for the electric field representing the mathematical foundation of the equivalence theorem. The particular emphasis is put on the treatment of boundary integral when the observation and source points, respectively, coincide. The boundary conditions at infinity are taken into account via the Sommerfeld radiation conditions. The derived coupled SIE set can be used in problems involving biological body exposed to electromagnetic field radiation. <![CDATA[ <p>The paper revisits the use of a surface equivalence theorem in deriving the surface integral equation (SIE) based formulation for a homogeneous bio-electromagnetics problem. The vector analog of Green’s 2nd identity is used to obtain the expression for the electric field representing the mathematical foundation of the equivalence theorem. The particular emphasis is put on the treatment of boundary integral when the observation and source points, respectively, coincide. The boundary conditions at infinity are taken into account via the Sommerfeld radiation conditions. The derived coupled SIE set can be used in problems involving biological body exposed to electromagnetic field radiation. </p> ]]> Equivalence Principle and Surface Integral Equation (Sie) Revisited for Bioelectromagnetics Application m. cvetković d. poljak doi: 10.2495/CMEM-V6-N6-1182-1191 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1182 10.2495/CMEM-V6-N6-1182-1191 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1182-1191 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1173-1181 This study investigates solvability of boundary value problems of plane elasticity formulated in terms of principal directions of the stress tensor and the orientations of the displacement vector. The analysis of solvability is performed by using the following approach. Firstly, boundary values of the complex potentials are represented by the Cauchy-type integrals with unknown density. Then a system of singular integral equations is obtained by satisfying particular boundary conditions. This system is further reduced to the system of the Riemann boundary value problems for the determination of sectionally holomorphic functions. Solvability of the Riemann problems is investigated by calculating their indexes. This allows one to determine the number of linearly independent solutions and hence the number of arbitrary parameters entering into the general solution.Two novel formulations have been investigated for the case of elastic half-planes. In both cases the initial system of equations has been reduced to the form that allow for successive solution of its equations. <![CDATA[ <p>This study investigates solvability of boundary value problems of plane elasticity formulated in terms of principal directions of the stress tensor and the orientations of the displacement vector. The analysis of solvability is performed by using the following approach. Firstly, boundary values of the complex potentials are represented by the Cauchy-type integrals with unknown density. Then a system of singular integral equations is obtained by satisfying particular boundary conditions. This system is further reduced to the system of the Riemann boundary value problems for the determination of sectionally holomorphic functions. Solvability of the Riemann problems is investigated by calculating their indexes. This allows one to determine the number of linearly independent solutions and hence the number of arbitrary parameters entering into the general solution.</p><p>Two novel formulations have been investigated for the case of elastic half-planes. In both cases the initial system of equations has been reduced to the form that allow for successive solution of its equations. </p> ]]> Boundary Value Problems for Elastic Half-Planes Posed in Terms of Stress and Displacement Orientations a.n. galybin doi: 10.2495/CMEM-V6-N6-1173-1181 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1173 10.2495/CMEM-V6-N6-1173-1181 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1173-1181 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1161-1172 It is well known that the original 3D elasticity problem in plate structures subjected to transversal loading can be converted to a 2D problem. In addition to in-plane displacements, we need to introduce the deflection and/or rotation field variables in the plate mid-plane, in order to describe displacements and deformations within the plate structure. Thus, one can develop unified formulation for bending and in- plane deformation modes within the classical Kirchhoff-Love theory for bending of thin elastic plates and the shear deformation plate theories (the first order – FSDPT, and the third order - TSDPT). In this paper, we extend the derivation of the 2D formulation for coupled problems of thermoelasticity in plate structures. Three material coefficients play the role in stationary problems, namely the Young modulus, coefficient of linear thermal extension and the heat conduction coefficient. The influence of continuous gradation of these coefficients on the response of the plate subjected to thermal loadings is investigated in numerical simulations. The element-free strong formulation with using meshless approximations for spatial variation of field variables is developed. <![CDATA[ <p>It is well known that the original 3D elasticity problem in plate structures subjected to transversal loading can be converted to a 2D problem. In addition to in-plane displacements, we need to introduce the deflection and/or rotation field variables in the plate mid-plane, in order to describe displacements and deformations within the plate structure. Thus, one can develop unified formulation for bending and in- plane deformation modes within the classical Kirchhoff-Love theory for bending of thin elastic plates and the shear deformation plate theories (the first order – FSDPT, and the third order - TSDPT). In this paper, we extend the derivation of the 2D formulation for coupled problems of thermoelasticity in plate structures. Three material coefficients play the role in stationary problems, namely the Young modulus, coefficient of linear thermal extension and the heat conduction coefficient. The influence of continuous gradation of these coefficients on the response of the plate subjected to thermal loadings is investigated in numerical simulations. The element-free strong formulation with using meshless approximations for spatial variation of field variables is developed.</p> ]]> Thermoelastic Analysis of Bending Problems in FGM Plates v. sladek l. sator j. sladek doi: 10.2495/CMEM-V6-N6-1161-1172 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1161 10.2495/CMEM-V6-N6-1161-1172 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1161-1172 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1149-1160 Based on the recently developed finite integration method (FIM) for solving one and two dimensional ordinary and partial differential equations, this paper extends FIM to both stationary and transient heat conduction inverse problems for anisotropic and functionally graded materials with high degree of accuracy. Lagrange series approximation is applied to determine the first order of integral and differential matrices, which are used to form the system equation matrix for two and three dimensional problems. Singular Value Decomposition (SVD) is applied to solve the ill-conditioned system of algebraic equations obtained from the integral equation, boundary conditions and scattered temperature measurements. The convergence and accuracy of this method are investigated with two examples for anisotropic media and functionally graded materials. <![CDATA[ <p>Based on the recently developed finite integration method (FIM) for solving one and two dimensional ordinary and partial differential equations, this paper extends FIM to both stationary and transient heat conduction inverse problems for anisotropic and functionally graded materials with high degree of accuracy. Lagrange series approximation is applied to determine the first order of integral and differential matrices, which are used to form the system equation matrix for two and three dimensional problems. Singular Value Decomposition (SVD) is applied to solve the ill-conditioned system of algebraic equations obtained from the integral equation, boundary conditions and scattered temperature measurements. The convergence and accuracy of this method are investigated with two examples for anisotropic media and functionally graded materials.</p> ]]> Heat Conduction in Anisotropic and Functionally Graded Media by Finite Integration Method j. jin j.l., zheng t., huang j.j., yang h.s., wang p.h., wen j.m., li doi: 10.2495/CMEM-V6-N6-1149-1160 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1149 10.2495/CMEM-V6-N6-1149-1160 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1149-1160 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1138-1148 A computational tool that integrates a Radial basis function (RBF)-based Meshless solver with a Lumped Parameter model (LPM) is developed to analyze the multi-scale and multi-physics interaction between the cardiovascular flow hemodynamics, the cardiac function, and the peripheral circulation. The Meshless solver is based on localized RBF collocations at scattered data points which allows for automation of the model generation via CAD integration. The time-accurate incompressible flow hemodynamics are addressed via a pressure-velocity correction scheme where the ensuing Poisson equations are accurately and efficiently solved at each time step by a Dual-Reciprocity Boundary Element method (DRBEM) formulation that takes advantage of the integrated surface discretization and automated point distribution used for the Meshless collocation. The local hemodynamics are integrated with the peripheral circulation via compartments that account for branch viscous resistance (R), flow inertia (L), and vessel compliance (C), namely RLC electric circuit analogies. The cardiac function is modeled via time-varying capacitors simulating the ventricles and constant capacitors simulating the atria, connected by diodes and resistors simulating the atrioventricular and ventricular-arterial valves. This multi-scale integration in an in-house developed computational tool opens the possibility for model automation of patient-specific anatomies from medical imaging, elastodynamics analysis of vessel wall deformation for fluid-structure interaction, automated model refinement, and inverse analysis for parameter estimation. <![CDATA[ <p>A computational tool that integrates a Radial basis function (RBF)-based Meshless solver with a Lumped Parameter model (LPM) is developed to analyze the multi-scale and multi-physics interaction between the cardiovascular flow hemodynamics, the cardiac function, and the peripheral circulation. The Meshless solver is based on localized RBF collocations at scattered data points which allows for automation of the model generation via CAD integration. The time-accurate incompressible flow hemodynamics are addressed via a pressure-velocity correction scheme where the ensuing Poisson equations are accurately and efficiently solved at each time step by a Dual-Reciprocity Boundary Element method (DRBEM) formulation that takes advantage of the integrated surface discretization and automated point distribution used for the Meshless collocation. The local hemodynamics are integrated with the peripheral circulation via compartments that account for branch viscous resistance (R), flow inertia (L), and vessel compliance (C), namely RLC electric circuit analogies. The cardiac function is modeled via time-varying capacitors simulating the ventricles and constant capacitors simulating the atria, connected by diodes and resistors simulating the atrioventricular and ventricular-arterial valves. This multi-scale integration in an in-house developed computational tool opens the possibility for model automation of patient-specific anatomies from medical imaging, elastodynamics analysis of vessel wall deformation for fluid-structure interaction, automated model refinement, and inverse analysis for parameter estimation.</p> ]]> Multi-Scale Cardiovascular Flow Analysis by an Integrated Meshless-Lumped Parameter Model leonardo a. bueno eduardo a. divo alain j. kassab doi: 10.2495/CMEM-V6-N6-1138-1148 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1138 10.2495/CMEM-V6-N6-1138-1148 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1138-1148 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1127-1137 In this study, we investigate the distribution of eigenfrequencies of boundary integral equations (BIEs) of two-dimensional elastodynamics. The corresponding eigenvalue problem is classified as a nonlin- ear eigenvalue problem. We confirm that the Burton-Miller formulation can properly avoid fictitious eigenfrequencies. The boundary element method (BEM) is expected as a powerful numerical tool for designing sophisticated devices related to elastic waves such as acoustic metamaterials. However, the BEM is known that it loses its accuracy for certain frequencies, called as fictitious eigenfrequencies, for problems defined in the infinite domain. Recent researches It has also been revealed that not only the real-valued eigenfrequencies but also the complex-valued ones may affect the accuracy of the BEM results. We examine the distribution of complex eigenvalues obtained by BIEs for time-harmonic elas- todynamic problems with the help of the Sakurai-Sugiura method which is applicable to nonlinear eigenvalue problems. We also examine its relation to the accuracy of the BEM numerical results. We also discuss an appropriate choice of the coupling parameter from a viewpoint of the distribution of fictitious eigenfrequencies. <![CDATA[ <p>In this study, we investigate the distribution of eigenfrequencies of boundary integral equations (BIEs) of two-dimensional elastodynamics. The corresponding eigenvalue problem is classified as a nonlin- ear eigenvalue problem. We confirm that the Burton-Miller formulation can properly avoid fictitious eigenfrequencies. The boundary element method (BEM) is expected as a powerful numerical tool for designing sophisticated devices related to elastic waves such as acoustic metamaterials. However, the BEM is known that it loses its accuracy for certain frequencies, called as fictitious eigenfrequencies, for problems defined in the infinite domain. Recent researches It has also been revealed that not only the real-valued eigenfrequencies but also the complex-valued ones may affect the accuracy of the BEM results. We examine the distribution of complex eigenvalues obtained by BIEs for time-harmonic elas- todynamic problems with the help of the Sakurai-Sugiura method which is applicable to nonlinear eigenvalue problems. We also examine its relation to the accuracy of the BEM numerical results. We also discuss an appropriate choice of the coupling parameter from a viewpoint of the distribution of fictitious eigenfrequencies.</p> ]]> An Investigation of Eigenfrequencies of Boundary Integral Equations and the Burton- Miller Formulation in Two-Dimensional Elastodynamics kei matsushima hiroshi isakari toshiro matsumoto doi: 10.2495/CMEM-V6-N6-1127-1137 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1127 10.2495/CMEM-V6-N6-1127-1137 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1127-1137 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1120-1126 The dynamics of multi-connected thermoelastic semiplane with the non-stationary power source and thermal effects by using of a model of coupled thermoelasticity is investigated. Green’s tensor in the space of the Laplace transforms in time describes the displacements of medium under the effect of the impulse concentrated power and thermal sources. The generalized solution of the problem of the dynamics of thermoelastic semiplane with the free boundary under the effect of arbitrary mass forces and thermal sources in 2D-case is built. <![CDATA[ <p>The dynamics of multi-connected thermoelastic semiplane with the non-stationary power source and thermal effects by using of a model of coupled thermoelasticity is investigated. Green’s tensor in the space of the Laplace transforms in time describes the displacements of medium under the effect of the impulse concentrated power and thermal sources. The generalized solution of the problem of the dynamics of thermoelastic semiplane with the free boundary under the effect of arbitrary mass forces and thermal sources in 2D-case is built.</p> ]]> Boundary Integral Equations of Dynamics Problems for Multi-Connected Thermoelastic Semi-Plane with a Free Boundary lyudmila a. alexeyeva bakhyt n. alipova doi: 10.2495/CMEM-V6-N6-1120-1126 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1120 10.2495/CMEM-V6-N6-1120-1126 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1120-1126 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1108-1119 Phononic crystals have been extensively studied, and their capacity to attenuate the propagation of sound waves at specific frequency bands is well known and documented in the literature. However, few studies exist concerning the behaviour of such structures in the context of elastic media, with the purpose of attenuating the transmission of vibrations. Applying this concept can be quite interesting, and may allow new vibration control devices to be developed, tailored at specific applications. As an example, buried periodic structures may be used to control elastic wave propagation in the ground, and thus to help reducing the vibrations that can reach sensible structures.In this work, the authors make use of a 2.5D numerical model based on the Method of Fundamental Solutions (MFS) to analyse this complex problem, considering the case of arrays of elastic inclusions buried in a homogeneous medium, fully considering the complete elastodynamic interaction between the inclusions and the host medium. Due to the geometric periodicity of the analysed problem, the numerical formulation can be simplified, particularly in what concerns the calculation of the system matrix, and significant computational gains can be obtained. The results of a numerical study concerning the behaviour of a sequence of embedded inclusions within an elastic material, when subject to the incidence of waves with different frequencies, is here presented, and the interpretation of the involved phenomena is described in order to clarify the main wave propagation features in the presence of multiple elastic inclusions. The computed results are promising, clearly revealing the existence of band gaps where large attenuation occurs, although limitations related to the existence of guided waves traveling along the inclusions are also identified. <![CDATA[ <p>Phononic crystals have been extensively studied, and their capacity to attenuate the propagation of sound waves at specific frequency bands is well known and documented in the literature. However, few studies exist concerning the behaviour of such structures in the context of elastic media, with the purpose of attenuating the transmission of vibrations. Applying this concept can be quite interesting, and may allow new vibration control devices to be developed, tailored at specific applications. As an example, buried periodic structures may be used to control elastic wave propagation in the ground, and thus to help reducing the vibrations that can reach sensible structures.</p><p>In this work, the authors make use of a 2.5D numerical model based on the Method of Fundamental Solutions (MFS) to analyse this complex problem, considering the case of arrays of elastic inclusions buried in a homogeneous medium, fully considering the complete elastodynamic interaction between the inclusions and the host medium. Due to the geometric periodicity of the analysed problem, the numerical formulation can be simplified, particularly in what concerns the calculation of the system matrix, and significant computational gains can be obtained. The results of a numerical study concerning the behaviour of a sequence of embedded inclusions within an elastic material, when subject to the incidence of waves with different frequencies, is here presented, and the interpretation of the involved phenomena is described in order to clarify the main wave propagation features in the presence of multiple elastic inclusions. The computed results are promising, clearly revealing the existence of band gaps where large attenuation occurs, although limitations related to the existence of guided waves traveling along the inclusions are also identified.</p> ]]> MFS Analysis of the Vibration Filtering Effect of Periodic Structures in Elastic Media luís godinho paulo amado-mendes pedro alves-costa doi: 10.2495/CMEM-V6-N6-1108-1119 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1108 10.2495/CMEM-V6-N6-1108-1119 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1108-1119 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1097-1107 In this paper, we present a fast boundary element method (BEM) algorithm for the solution of the velocity-vorticity formulation of the Navier-Stokes equations. The Navier-Stokes equations govern incompressible fluid flow, which is inherently nonlinear and when discretizised by BEM requires the discretization of the domain and calculation of domain integrals. The computational demands of such method scale with O(N2), where N is the number of boundary nodes. To accelerate the solution process and reduce the computational demand, we present two different approaches, the subdomain method and an approximation procedure with hierarchical structure. Several approximation techniques exist, such as multipole approximation methods FMM (fast multiple method), SVD (singular value decomposition method), wavelet transform method and a cross approximation method. In this paper, we present the cross approximation method in combination with the hierarchical H-structure. The cross approximation method can reduce the computational demands from O(N2) to O(N log N). There are many forms of the cross approximation, like the algebraic cross approximation and the hybrid cross approximation. Here, we applied the algebraic cross approximation form. The main advantage is that we did not need to evaluate the integral and then to change it with a degenerate kernel function. The cross approximation algorithm was used to solve the kinematics equation for unknown boundary vorticity values. Results show that an increasing of the compression rate has a negative influence on the solution accuracy. On the other hand, the solution accuracy increases with computational grid density. Tests were performed using the 3D lid-driven cavity test case with Reynolds numbers up to 1000. Solution accuracy was similar for all Reynolds numbers considered. In conclusion, the tests showed that our implementation of the algebraic cross approximation for the acceleration of the solution of the kinematics equation can be applied to decrease the computational demands and to accelerate the BEM. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In this paper, we present a fast boundary element method (BEM) algorithm for the solution of the velocity-vorticity formulation of the Navier-Stokes equations. The Navier-Stokes equations govern incompressible fluid flow, which is inherently nonlinear and when discretizised by BEM requires the discretization of the domain and calculation of domain integrals. The computational demands of such method scale with O(N2), where N is the number of boundary nodes. To accelerate the solution process and reduce the computational demand, we present two different approaches, the subdomain method and an approximation procedure with hierarchical structure. Several approximation techniques exist, such as multipole approximation methods FMM (fast multiple method), SVD (singular value decomposition method), wavelet transform method and a cross approximation method. In this paper, we present the cross approximation method in combination with the hierarchical H-structure. The cross approximation method can reduce the computational demands from O(N2) to O(N log N). There are many forms of the cross approximation, like the algebraic cross approximation and the hybrid cross approximation. Here, we applied the algebraic cross approximation form. The main advantage is that we did not need to evaluate the integral and then to change it with a degenerate kernel function. The cross approximation algorithm was used to solve the kinematics equation for unknown boundary vorticity values. Results show that an increasing of the compression rate has a negative influence on the solution accuracy. On the other hand, the solution accuracy increases with computational grid density. Tests were performed using the 3D lid-driven cavity test case with Reynolds numbers up to 1000. Solution accuracy was similar for all Reynolds numbers considered. In conclusion, the tests showed that our implementation of the algebraic cross approximation for the acceleration of the solution of the kinematics equation can be applied to decrease the computational demands and to accelerate the BEM.</span></p> ]]> Acceleration of BEM with the Cross Approximation for Determination of Boundary Vorticity jan tibaut leopold škerget doi: 10.2495/CMEM-V6-N6-1097-1107 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1097 10.2495/CMEM-V6-N6-1097-1107 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1097-1107 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1087-1096 In this paper, we derive a boundary-domain integral formulation for the vorticity transport equation under the assumption that the viscosity of the fluid, through which the vorticity is transported by diffusion and convection, is spatially changing. The vorticity transport equation is a second order partial differential equation of a diffusion-convection type.The final boundary-domain integral representation of the vorticity transport equation is discretized using a domain decomposition approach, where a system of linear equations is set-up for each sub-domain, while subdomains are joint by compatibility conditions. The validity of the method is checked using several analytical examples. Convergence properties are studied yielding that the proposed discretization technique is second order accurate for constant and variable viscosity cases. <![CDATA[ <p>In this paper, we derive a boundary-domain integral formulation for the vorticity transport equation under the assumption that the viscosity of the fluid, through which the vorticity is transported by diffusion and convection, is spatially changing. The vorticity transport equation is a second order partial differential equation of a diffusion-convection type.</p><p style="text-align: justify">The final boundary-domain integral representation of the vorticity transport equation is discretized using a domain decomposition approach, where a system of linear equations is set-up for each sub-domain, while subdomains are joint by compatibility conditions. The validity of the method is checked using several analytical examples. Convergence properties are studied yielding that the proposed discretization technique is second order accurate for constant and variable viscosity cases.</p> ]]> Boundary-Domain Integral Method for Vorticity Transport Equation With Variable Viscosity j. ravnik j. tibaut doi: 10.2495/CMEM-V6-N6-1087-1096 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1087 10.2495/CMEM-V6-N6-1087-1096 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1087-1096 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1079-1086 This work investigates the mass ejected from surface perturbations as the shockwave reaches the AL-vacuum interface, which originates from unstable Richtmyer–Meshkov (RMI) impulse phenomena. The main purpose is to explore the relationships between the shockwave impulse and the geometric properties of surface perturbations, and how those relationships drive the total ejected mass, directionality and velocity distribution. We discuss in detail different types of surface geometry (sinusoidal, square-wave, chevron and semicircle), as well as the wavelengths and amplitudes of surface perturbation. The time evolutions of micro-jet ejection are simulated using a hydrodynamic Lagrangian-Remapping Eulerian method. The calculated results show that primary jetting ejection can be formed from the different shapes, and with increasing wavelength, the ejection mass keeps an increase while the jet head-velocity decreases. However, not all periodic perturbations behave similarly, and masses ejected from irregular surface cannot be normalized to its cross-sectional areas. The square-wave surface may yield pronounced, velocity-enhanced secondary jetting, which is a result of collision of primary jets. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This work investigates the mass ejected from surface perturbations as the shockwave reaches the AL-vacuum interface, which originates from unstable Richtmyer–Meshkov (RMI) impulse phenomena. The main purpose is to explore the relationships between the shockwave impulse and the geometric properties of surface perturbations, and how those relationships drive the total ejected mass, directionality and velocity distribution. We discuss in detail different types of surface geometry (sinusoidal, square-wave, chevron and semicircle), as well as the wavelengths and amplitudes of surface perturbation. The time evolutions of micro-jet ejection are simulated using a hydrodynamic Lagrangian-Remapping Eulerian method. The calculated results show that primary jetting ejection can be formed from the different shapes, and with increasing wavelength, the ejection mass keeps an increase while the jet head-velocity decreases. However, not all periodic perturbations behave similarly, and masses ejected from irregular surface cannot be normalized to its cross-sectional areas. The square-wave surface may yield pronounced, velocity-enhanced secondary jetting, which is a result of collision of primary jets.</span></p> ]]> Exploring Richtmyer–Meshkov Instability Phenomena and the Links between Surface Perturbations and Shocked-Induced Mass Ejection shi yina wang pei zhao qiang doi: 10.2495/CMEM-V6-N6-1079-1086 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1079 10.2495/CMEM-V6-N6-1079-1086 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1079-1086 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1067-1078 Sound transmission through thin elastic shell with different fluids on the inside and outside is simulated using the in-house program based on the coupled finite element and boundary element method. The structure dynamics is simulated using the finite element method and the acoustic fields are simulated using the boundary element method. To avoid the non-uniqueness problem existing in the exterior acoustic boundary element method, Burton and Miller formulation is employed. The hyper-singular boundary integral is dealt with a regularization relationship. To validate this approach, a case with analytical solutions is simulated. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Sound transmission through thin elastic shell with different fluids on the inside and outside is simulated using the in-house program based on the coupled finite element and boundary element method. The structure dynamics is simulated using the finite element method and the acoustic fields are simulated using the boundary element method. To avoid the non-uniqueness problem existing in the exterior acoustic boundary element method, Burton and Miller formulation is employed. The hyper-singular boundary integral is dealt with a regularization relationship. To validate this approach, a case with analytical solutions is simulated.</span></p> ]]> Simulation of Sound Structure Interactions by the Coupled FEM/BEM zai-you yan doi: 10.2495/CMEM-V6-N6-1067-1078 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1067 10.2495/CMEM-V6-N6-1067-1078 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1067-1078 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1057-1066 Crack propagation in a single-edge notched beam is analyzed with the three-point bending test. Two constitutive laws that describe the material softening in the cohesive zone were tested, and their results were compared. The dual boundary element method (DBEM) is employed with the traction boundary integral equation using the tangential differential operator. A constitutive law was introduced in the system of equations, and the cohesive forces were directly computed at each loading step. The results are compared with the experimental and numerical results available in the literature. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Crack propagation in a single-edge notched beam is analyzed with the three-point bending test. Two constitutive laws that describe the material softening in the cohesive zone were tested, and their results were compared. The dual boundary element method (DBEM) is employed with the traction boundary integral equation using the tangential differential operator. A constitutive law was introduced in the system of equations, and the cohesive forces were directly computed at each loading step. The results are compared with the experimental and numerical results available in the literature.</span></p> ]]> Analysis of Two Cohesive Zone Models for Crack Propagation in Notched Beams Using the BEM p.c. gonçalves l. palermo jr. s.p.b. proença doi: 10.2495/CMEM-V6-N6-1057-1066 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1057 10.2495/CMEM-V6-N6-1057-1066 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1057-1066 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1043-1056 A model for numerical analysis of compound structures made of various materials is presented. The mathematical concept of solution is based on quasi-static evolution of debonding processes occurring along the interface. It is formulated in terms of energies considering the stored energy represented by the elastic energy of the structures and dissipation due to damage processes, plastic slip at the inter- face or friction. The numerical solution includes a semi-implicit time stepping procedure, relying on splitting of the whole problem at a current time step into two problems of variational nature solved recursively. The space discretisation includes Symmetric Galerkin Boundary Element Method used to obtain the stored energies, and, in combination with the variational character of the recursive problems, also to calculate its gradients to be utilized in non-linear programming algorithms for finding the time- evolving solution. Numerical results are demonstrated for a steel-concrete interface frequently met in civil engineering applications to assess the model applicability in engineering practice. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A model for numerical analysis of compound structures made of various materials is presented. The mathematical concept of solution is based on quasi-static evolution of debonding processes occurring along the interface. It is formulated in terms of energies considering the stored energy represented by the elastic energy of the structures and dissipation due to damage processes, plastic slip at the inter- face or friction. The numerical solution includes a semi-implicit time stepping procedure, relying on splitting of the whole problem at a current time step into two problems of variational nature solved recursively. The space discretisation includes Symmetric Galerkin Boundary Element Method used to obtain the stored energies, and, in combination with the variational character of the recursive problems, also to calculate its gradients to be utilized in non-linear programming algorithms for finding the time- evolving solution. Numerical results are demonstrated for a steel-concrete interface frequently met in civil engineering applications to assess the model applicability in engineering practice.</span></p> ]]> A Quasi-Static Interface Damage Model with Frictional Contact – Applications to Steel Reinforced Concrete Structures roman vodička filip kšiňan doi: 10.2495/CMEM-V6-N6-1043-1056 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1043 10.2495/CMEM-V6-N6-1043-1056 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1043-1056 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1033-1042 This paper presents a numerical method for topology optimisation for two-dimensional elastodynamics based on the level set method and the boundary element method (BEM) accelerated by the H-matrix method and its application to identifications of defects in an infinite elastic medium. Gradient-based topology optimisation methods require design sensitivity, which is obtained by solving some boundary value problems. The BEM is employed for this sensitivity analysis because the BEM can deal with infinite domains rigorously without any approximation. However, the computational cost in the BEM is expensive, and this is a serious drawback since we need to repeat sensitivity analysis even for a single optimisation process. In this study, the H-matrix method is used as an acceleration method of the BEM for the reduction of the computational cost of the sensitivity analysis. Also proposed is a method to improve the efficiency of the H-matrix method by exploiting a property of the kernel function of the elastodynamic fundamental solution. Some numerical examples are demonstrated, and the effectiveness of the proposed method is confirmed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper presents a numerical method for topology optimisation for two-dimensional elastodynamics based on the level set method and the boundary element method (BEM) accelerated by the H-matrix method and its application to identifications of defects in an infinite elastic medium. Gradient-based topology optimisation methods require design sensitivity, which is obtained by solving some boundary value problems. The BEM is employed for this sensitivity analysis because the BEM can deal with infinite domains rigorously without any approximation. However, the computational cost in the BEM is expensive, and this is a serious drawback since we need to repeat sensitivity analysis even for a single optimisation process. In this study, the H-matrix method is used as an acceleration method of the BEM for the reduction of the computational cost of the sensitivity analysis. Also proposed is a method to improve the efficiency of the H-matrix method by exploiting a property of the kernel function of the elastodynamic fundamental solution. Some numerical examples are demonstrated, and the effectiveness of the proposed method is confirmed.</span></p> ]]> An Application of Topology Optimisation to Defect Identification in Two-Dimensional Elastodynamics with the BEM and H-Matrix Method kei matsushima hiroshi isakari toru takahashi doi: 10.2495/CMEM-V6-N6-1033-1042 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1033 10.2495/CMEM-V6-N6-1033-1042 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1033-1042 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1019-1032 The linear coupled stretching-bending problem for general laminates is here formulated with the mid-plane stress function and the lateral deflection as independent field variables. A mathematical similarity between the two problems is achieved by introducing a re-arranged mid-plane strain tensor as one of the dependent variables. As a step towards a genuine boundary element solution for this problem, its fundamental solutions are derived using a Fourier transform approach. First, the transforms of the solutions are obtained in terms of the transform space variables and their inverses are deduced using complex integral calculus. Through the use of these fundamental solutions, boundary integral equations of the linear coupled stretching-bending problem are formulated without the presence of any irreduc- ible domain integrals. Issues regarding the numerical implementation of this formulation are raised and discussed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The linear coupled stretching-bending problem for general laminates is here formulated with the mid-plane stress function and the lateral deflection as independent field variables. A mathematical similarity between the two problems is achieved by introducing a re-arranged mid-plane strain tensor as one of the dependent variables. As a step towards a genuine boundary element solution for this problem, its fundamental solutions are derived using a Fourier transform approach. First, the transforms of the solutions are obtained in terms of the transform space variables and their inverses are deduced using complex integral calculus. Through the use of these fundamental solutions, boundary integral equations of the linear coupled stretching-bending problem are formulated without the presence of any irreduc- ible domain integrals. Issues regarding the numerical implementation of this formulation are raised and discussed.</span></p> ]]> Fundamental Solutions for the General Laminate Problem with the Stress Function Formalism stavros syngellakis doi: 10.2495/CMEM-V6-N6-1019-1032 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1019 10.2495/CMEM-V6-N6-1019-1032 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1019-1032 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1008-1018 Nowadays, a variety of numerical methods and numerical formulations exits to solve complex or coupled field problems in three dimensions. Most of them are generally applicable to nearly arbitrary kind of field problems. On the other hand, some highly optimized methods are available, which are predestined for the solution of a specific kind of problem. Especially in the case of weakly coupled multiphysics problems, a mixture of several numerical methods is very advantages to benefit from different properties of numerical methods for diverse physical sub-problems. A very promising approach for a flexible coordination of the related solution process is the application of software agents. Then, the results of one sub-problem are converted into boundary values or volume source distributions for another sub-problem and software agents choose solution methods independently for each sub-problem. Furthermore, two main aspects have to be considered in applications of numerical methods. First, the solution of a boundary value problem should be computed efficiently and second, the solution is evaluated for visualization and interpretation of obtained results. In practice, it is difficult to choose a single appropriate method, which is well suited both for the solution of a problem and its evaluation, since the demands differ in both cases. Here, a concept is presented to apply various numerical methods successfully to the solution and evaluation of complex field problems. Attention is mainly turned on the integration of boundary element methods into the concept of mixed numerical formulations. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Nowadays, a variety of numerical methods and numerical formulations exits to solve complex or coupled field problems in three dimensions. Most of them are generally applicable to nearly arbitrary kind of field problems. On the other hand, some highly optimized methods are available, which are predestined for the solution of a specific kind of problem. Especially in the case of weakly coupled multiphysics problems, a mixture of several numerical methods is very advantages to benefit from different properties of numerical methods for diverse physical sub-problems. A very promising approach for a flexible coordination of the related solution process is the application of software agents. Then, the results of one sub-problem are converted into boundary values or volume source distributions for another sub-problem and software agents choose solution methods independently for each sub-problem. Furthermore, two main aspects have to be considered in applications of numerical methods. First, the solution of a boundary value problem should be computed efficiently and second, the solution is evaluated for visualization and interpretation of obtained results. In practice, it is difficult to choose a single appropriate method, which is well suited both for the solution of a problem and its evaluation, since the demands differ in both cases. Here, a concept is presented to apply various numerical methods successfully to the solution and evaluation of complex field problems. Attention is mainly turned on the integration of boundary element methods into the concept of mixed numerical formulations.</span></p> ]]> A Concept of Separated Numerical Formulations for the Solution and Evaluation of Complex Field Problems andré buchau matthias jüttner doi: 10.2495/CMEM-V6-N6-1008-1018 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1008 10.2495/CMEM-V6-N6-1008-1018 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1008-1018 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1000-1007 We apply the Kansa–radial basis function (RBF) collocation method to two– dimensional nonlinear boundary value problems. The system of nonlinear equations resulting from the Kansa–RBF discretization is solved by directly applying a standard nonlinear solver. In a natural way, the value of the shape parameter in the RBFs employed in the approximation is included in the unknowns to be determined. The numerical results of some examples are presented and analysed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">We apply the Kansa–radial basis function (RBF) collocation method to two– dimensional nonlinear boundary value problems. The system of nonlinear equations resulting from the Kansa–RBF discretization is solved by directly applying a standard nonlinear solver. In a natural way, the value of the shape parameter in the RBFs employed in the approximation is included in the unknowns to be determined. The numerical results of some examples are presented and analysed.</span></p> ]]> Kansa RBF Method for Nonlinear Problems m. a. jankowska a. karageorghis c. s. chen doi: 10.2495/CMEM-V6-N6-1000-1007 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 1000 10.2495/CMEM-V6-N6-1000-1007 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-1000-1007 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-0 This special issue contains papers selected from the 40th International Conference on Boundary Elements and other Mesh Reduction Methods, held in the New Forest, UK, organised by the Wessex Institute. The annual conference on Boundary Elements and other Mesh Reduction Methods (BEM/MRM) started in 1978 and is now in its 40th version. It is well established as the recognised international forum for the latest advances in those techniques and their application in science and engineering.The continued success of the meeting is a result of the strength of the research on boundary elements and mesh reduction techniques being carried out all over the world. The conference has continually evolved in line with the latest developments in the field since the successful development of boundary integral techniques into BEM was reported in the first meeting held in Southampton in 1978.The objective of the research papers presented at the meetings is the further development of techniques that reduce or eliminate the type of meshes required by first generation computational methods, such as finite differences or finite elements.This has steadily been achieved through the development of BEM as a computational tool and continues through more recent research into advanced techniques, leading to further mesh reduction aiming to produce truly meshless methods.Also included are papers on the use of BEM and, in particular, the description of new applications. The Editors would like to thank all authors for the quality of their papers and other colleagues for their help in reviewing the material. The Editors 2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This special issue contains papers selected from the 40th International Conference on Boundary Elements and other Mesh Reduction Methods, held in the New Forest, UK, organised by the Wessex Institute. </span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The annual conference on Boundary Elements and other Mesh Reduction Methods (BEM/MRM) started in 1978 and is now in its 40th version. It is well established as the recognised international forum for the latest advances in those techniques and their application in science and engineering.</span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The continued success of the meeting is a result of the strength of the research on boundary elements and mesh reduction techniques being carried out all over the world. The conference has continually evolved in line with the latest developments in the field since the successful development of boundary integral techniques into BEM was reported in the first meeting held in Southampton in 1978.</span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The objective of the research papers presented at the meetings is the further development of techniques that reduce or eliminate the type of meshes required by first generation computational methods, such as finite differences or finite elements.</span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This has steadily been achieved through the development of BEM as a computational tool and continues through more recent research into advanced techniques, leading to further mesh reduction aiming to produce truly meshless methods.</span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Also included are papers on the use of BEM and, in particular, the description of new applications. </span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The Editors would like to thank all authors for the quality of their papers and other colleagues for their help in reviewing the material. </span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The Editors </span><br><br><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">2017</span></p> ]]> Preface carlos a. brebbia alexander h.d. cheng doi: 10.2495/CMEM-V6-N6-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 6 Article 0 10.2495/CMEM-V6-N6-0 https://www.acadlore.com/article/IJCMEM/2018_6_6/CMEM-V6-N6-0 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-iii <![CDATA[ ]]> Preface doi: 10.2495/CMEM-V6-N5-iii International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 0 10.2495/CMEM-V6-N5-iii https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-iii https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-944-954 Earthquakes result in substantial structural damage of a number of structures across a region. Many studies have made an effort to examine regional seismic damage and vulnerability to different structure types, e.g. buildings and bridges, using varying computational methodologies. This paper focuses on the use of Response Surface Metamodels (RSMs) in conjunction with Monte Carlo Simulations (MCSs) to quantify probabilistic seismic performance for different classes of structural populations with irregularities, including irregular steel buildings and steel girder bridges. As part of the regional vulnerability study, each of the selected classes is constructed based upon the appropriate experimental design technique, i.e. the Central Composite Design (CCD), and the responses of each class subjected to multiple ground motions are captured during the nonlinear time history analyses of an individual computational model. Then, a RSM for each class is established by performing a least-square regression analysis within the considered CCD space. Seismic fragility curves are generated by means of the joint RSM-MCS enabling to treat uncertainties regarding overall configuration irregularities and additional structural parameters considered significant for each class. The influence of the irregularity parameters on seismic vulnerability for each class is investigated by comparison of the resulting fragilities. Results reveal that the RSM-MCS is able to efficiently assess seismic vulnerability of each class and directly examine the parameters’ influence on corresponding behaviours. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Earthquakes result in substantial structural damage of a number of structures across a region. Many studies have made an effort to examine regional seismic damage and vulnerability to different structure types, e.g. buildings and bridges, using varying computational methodologies. This paper focuses on the use of Response Surface Metamodels (RSMs) in conjunction with Monte Carlo Simulations (MCSs) to quantify probabilistic seismic performance for different classes of structural populations with irregularities, including irregular steel buildings and steel girder bridges. As part of the regional vulnerability study, each of the selected classes is constructed based upon the appropriate experimental design technique, i.e. the Central Composite Design (CCD), and the responses of each class subjected to multiple ground motions are captured during the nonlinear time history analyses of an individual computational model. Then, a RSM for each class is established by performing a least-square regression analysis within the considered CCD space. Seismic fragility curves are generated by means of the joint RSM-MCS enabling to treat uncertainties regarding overall configuration irregularities and additional structural parameters considered significant for each class. The influence of the irregularity parameters on seismic vulnerability for each class is investigated by comparison of the resulting fragilities. Results reveal that the RSM-MCS is able to efficiently assess seismic vulnerability of each class and directly examine the parameters’ influence on corresponding behaviours.</span></p> ]]> Seismic Fragility Characteristics of Structural Populations with Irregularities junwon seo doi: 10.2495/CMEM-V6-N5-944-954 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 944 10.2495/CMEM-V6-N5-944-954 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-944-954 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-933-943 The objective of earthquake-resistant design of critical infrastructures like nuclear power plants or lifelines is to ensure the prevention of catastrophic disasters. Experience from recent past like the earthquake of Amatrice (2016) or the Napa earthquake of 2014 have shown that traditional code requirements based on probabilistic seismic hazard maps are not able to prevent disasters. The purpose of probabilistic hazard assessment is to support risk analysis. The latter is used to separate tolerated residual risks from non-tolerable, more frequent risks. Therefore, these methods do not intend to provide protection against extreme events. Additionally, it is proven that the traditional hazard parameter used in probabilistic seismic hazard maps, peak ground acceleration (PGA), is not very suitable for the description of the physical impact of earthquakes on structures, systems and components. The only hazard parameter describing physical effects of earthquakes at least on macroseismic scale is intensity or in engineering units, intensity factors. The actual EMS-98 scale correlates reasonably well with the damage of structures classified into vulnerability classes.The availability of large databases of registered earthquake time-histories covering a wide range of site intensity values allows to model earthquake impact directly using dynamic time-history analysis methods. On this basis a methodology was developed that allows to design critical infrastructures for certain levels of seismic intensity directly.The methodology and some applications are presented. <![CDATA[ <p>The objective of earthquake-resistant design of critical infrastructures like nuclear power plants or lifelines is to ensure the prevention of catastrophic disasters. Experience from recent past like the earthquake of Amatrice (2016) or the Napa earthquake of 2014 have shown that traditional code requirements based on probabilistic seismic hazard maps are not able to prevent disasters. The purpose of probabilistic hazard assessment is to support risk analysis. The latter is used to separate tolerated residual risks from non-tolerable, more frequent risks. Therefore, these methods do not intend to provide protection against extreme events. Additionally, it is proven that the traditional hazard parameter used in probabilistic seismic hazard maps, peak ground acceleration (PGA), is not very suitable for the description of the physical impact of earthquakes on structures, systems and components. The only hazard parameter describing physical effects of earthquakes at least on macroseismic scale is intensity or in engineering units, intensity factors. The actual EMS-98 scale correlates reasonably well with the damage of structures classified into vulnerability classes.</p><p style="text-align: justify">The availability of large databases of registered earthquake time-histories covering a wide range of site intensity values allows to model earthquake impact directly using dynamic time-history analysis methods. On this basis a methodology was developed that allows to design critical infrastructures for certain levels of seismic intensity directly.</p><p style="text-align: justify">The methodology and some applications are presented.</p> ]]> Towards Damage-Consistent Performance-Based Design of Critical Infrastructures jens-uwe klügel sunay stäuble-akcay doi: 10.2495/CMEM-V6-N5-933-943 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 933 10.2495/CMEM-V6-N5-933-943 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-933-943 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-921-932 Structural damage computation using analytical methods requires the knowledge of the ground motion distribution in the urban area caused by a given earthquake. In this manuscript, the ground motion estimates (i.e. PGA and spectral acceleration values) are obtained through simulation of the 1829 Torrevieja earthquake using the NGA ground motion prediction equations (GMPE). The building stock under consideration has been classified according to the methodology presented in RISK-UE. The computations have been done using the last version of the software SELENA. The epistemic uncertainties of the analysis are accounted for by means of a logic tree computation scheme. The logic tree has two branches for the uncertainty in the earthquake scenario, two branches for the GMPEs and three branches to consider the uncertainties in average shear wave velocity Vs30 (soil conditions). Results indicate large differences derived for the different earthquake loss scenarios (ELE) obtained following each branch of the logic tree.The greatest structural damages and losses are obtained when the earthquake is located in the Bajo Segura fault zone, using Campbell and Bozorgnia GMPE and for soft soil conditions. This article has allowed us to see how the different possible input parameters for ELE should be carefully analyzed for each case study and the importance of providing ELE results in terms of mean values with corresponding uncertainty ranges. <![CDATA[ <p style="text-align: justify">Structural damage computation using analytical methods requires the knowledge of the ground motion distribution in the urban area caused by a given earthquake. In this manuscript, the ground motion estimates (i.e. PGA and spectral acceleration values) are obtained through simulation of the 1829 Torrevieja earthquake using the NGA ground motion prediction equations (GMPE). The building stock under consideration has been classified according to the methodology presented in RISK-UE. The computations have been done using the last version of the software SELENA. The epistemic uncertainties of the analysis are accounted for by means of a logic tree computation scheme. The logic tree has two branches for the uncertainty in the earthquake scenario, two branches for the GMPEs and three branches to consider the uncertainties in average shear wave velocity Vs30 (soil conditions). Results indicate large differences derived for the different earthquake loss scenarios (ELE) obtained following each branch of the logic tree.</p><p style="text-align: justify">The greatest structural damages and losses are obtained when the earthquake is located in the Bajo Segura fault zone, using Campbell and Bozorgnia GMPE and for soft soil conditions. This article has allowed us to see how the different possible input parameters for ELE should be carefully analyzed for each case study and the importance of providing ELE results in terms of mean values with corresponding uncertainty ranges.</p> ]]> Sensitivity of Structural Damage to Earthquake Ground Motion Scenarios. The Torrevieja Earthquake Case Study n. agea-medina s. molina-palacios d.h. lang i. ferreiro-prieto j.a. huesca j.j. galiana-merino j.l. soler-llorens doi: 10.2495/CMEM-V6-N5-921-932 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 921 10.2495/CMEM-V6-N5-921-932 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-921-932 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-910-920 This paper studies the impact of spatially varying ground motions on the responses of a railway bridge. The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and the local conditions of the site. Firstly, the seismic ground motions are modelled by assuming the base rock motions of the same intensity and modelling them with a filtered Tajimi-Kanai power spectral density function and a spatial ground motion coherency loss function. Then, the power spectral density function of ground motion on surface is derived by considering the site amplification effect based on the one-dimensional seismic wave propagation theory. A comparison between the bridge responses to uniform ground motion, to spatial ground motions with and without considering local site effects is established. Discussions on the seismic ground motion spatial variability and local site conditions effects on structural responses of railway bridge are made. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper studies the impact of spatially varying ground motions on the responses of a railway bridge. The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and the local conditions of the site. Firstly, the seismic ground motions are modelled by assuming the base rock motions of the same intensity and modelling them with a filtered Tajimi-Kanai power spectral density function and a spatial ground motion coherency loss function. Then, the power spectral density function of ground motion on surface is derived by considering the site amplification effect based on the one-dimensional seismic wave propagation theory. A comparison between the bridge responses to uniform ground motion, to spatial ground motions with and without considering local site effects is established. Discussions on the seismic ground motion spatial variability and local site conditions effects on structural responses of railway bridge are made.</span></p> ]]> Impact of Spatial Variability of Earthquake Ground Motion on Seismic Response of a Railway Bridge rachid derbal nassima benmansour mustapha djafour doi: 10.2495/CMEM-V6-N5-910-920 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 910 10.2495/CMEM-V6-N5-910-920 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-910-920 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-899-909 Lightweight (thin-walled or cold-formed) steel portal frame structure could be a popular and effective alternative to the traditional hot rolled structure and, with care to avoid buckling, could be used in earthquake areas owing to its economy and ease of fabrication and transportation, but no recommendations for seismic design of these structures is provided in the design codes. Accordingly, there is need for a lightweight design that is suitable for earthquake areas, which could be transported using lighter vehicles and erected quickly using smaller plant than is required for conventional hot rolled sections following an earthquake. The present paper shows some stages in the development of an earthquake-resistant frame, designed for by combining numerical finite element investigations with analytical check calculations based on EN 1993-1-3 for cold-formed steel members and EN 1993-1-1 for design of steel structures to estimate the loads on the frame structure within the use of EN 1998-1seismic design requirements. Although the initial buckling modes have been avoided, the frame still needs further modification to improve its ductility. It is planned to use this work to assist with the development of performance-based design recommendations for future structures that cover both thin-walled steel and cold-formed steel portal frame structures. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Lightweight (thin-walled or cold-formed) steel portal frame structure could be a popular and effective alternative to the traditional hot rolled structure and, with care to avoid buckling, could be used in earthquake areas owing to its economy and ease of fabrication and transportation, but no recommendations for seismic design of these structures is provided in the design codes. Accordingly, there is need for a lightweight design that is suitable for earthquake areas, which could be transported using lighter vehicles and erected quickly using smaller plant than is required for conventional hot rolled sections following an earthquake. The present paper shows some stages in the development of an earthquake-resistant frame, designed for by combining numerical finite element investigations with analytical check calculations based on EN 1993-1-3 for cold-formed steel members and EN 1993-1-1 for design of steel structures to estimate the loads on the frame structure within the use of EN 1998-1seismic design requirements. Although the initial buckling modes have been avoided, the frame still needs further modification to improve its ductility. It is planned to use this work to assist with the development of performance-based design recommendations for future structures that cover both thin-walled steel and cold-formed steel portal frame structures.</span></p> ]]> Seismic Analysis and Design Assisted by Numerical Simulation of Slender Steel Portal Frame Structures alia o. m. ahmed nigel d. p. barltrop doi: 10.2495/CMEM-V6-N5-899-909 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 899 10.2495/CMEM-V6-N5-899-909 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-899-909 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-887-898 Despite the technical advances in seismic structural design, many regions still present a high level of seismic risk, principally due to the high vulnerability of their buildings. A modification of the empirical method for assessing the seismic vulnerability of reinforced concrete buildings in urban areas is proposed in this contribution. In the RISK-UE LM1 framework, the values of certain behaviour modifiers related to the typological, structural and urban parameters of the buildings have been modified according to a review and analysis of the currently available models and an evaluation of the actual seismic performance of buildings. This provides continuity to the progress of the previous works published to date. The proposal has been applied to the city of Lorca, Spain, for which ample knowledge of the damage occurred in the earthquake of May 11, 2011 is available. Less dispersion between actual observed and estimated damage in buildings is presented in comparison with the previous studies, with a statistical significance of 5%, thus achieving a more accurate evaluation of seismic risk. The new model also provides valuable information to be used in the planning and management of post-earthquake emergency situations when combining with GIS techniques, thus allowing for a better definition of several damage scenarios to enhance the development and urban preparedness in case of further seismic events. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Despite the technical advances in seismic structural design, many regions still present a high level of seismic risk, principally due to the high vulnerability of their buildings. A modification of the empirical method for assessing the seismic vulnerability of reinforced concrete buildings in urban areas is proposed in this contribution. In the RISK-UE LM1 framework, the values of certain behaviour modifiers related to the typological, structural and urban parameters of the buildings have been modified according to a review and analysis of the currently available models and an evaluation of the actual seismic performance of buildings. This provides continuity to the progress of the previous works published to date. The proposal has been applied to the city of Lorca, Spain, for which ample knowledge of the damage occurred in the earthquake of May 11, 2011 is available. Less dispersion between actual observed and estimated damage in buildings is presented in comparison with the previous studies, with a statistical significance of 5%, thus achieving a more accurate evaluation of seismic risk. The new model also provides valuable information to be used in the planning and management of post-earthquake emergency situations when combining with GIS techniques, thus allowing for a better definition of several damage scenarios to enhance the development and urban preparedness in case of further seismic events.</span></p> ]]> Advances in Seismic Vulnerability Assessment of Reinforced Concrete Buildings Applied to the Experience of Lorca (Spain) 2011 Earthquake j.l. ródenas a. tomás s. garcía-ayllón doi: 10.2495/CMEM-V6-N5-887-898 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 887 10.2495/CMEM-V6-N5-887-898 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-887-898 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-880-886 Large deformable elastic braces (LDEBs) are devices which do never yield subject to large deforma-tion under great earthquakes. In structures with LDEBs, elastic restoring force by LDEBs can improve seismic response under great earthquakes. In previous works, the effectiveness of LDEBs for the steel structures was confirmed by experimental tests and seismic response analyses. Here, the topology of LDEBs is determined by an optimization method, and seismic response analyses of RC portal frames with LDEBs are conducted. The effectiveness of LDEBs for the RC structures is discussed. RC portal frame are designed by Japanese seismic design code. LDEBs are equipped with the frame as knee braces. Seismic responses of not only the frame with LDEBs but also that without LDEBs are computed by dynamic nonlinear analysis software. In the analysis LDEBs are regarded as elastic bar elements. An input earthquake is JMA Kobe NS wave (1995 Kobe earthquakes). Hysteresis of story shear force and story drift, axial deformation of LDEBs, maximum and residual story drift are investigated. It is observed from computational results that LDEBs show remarkable improvements on maximum and residual story drifts of RC portal frame under a very large amplitude earthquake such as 1995 Kobe earthquake in Japan. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Large deformable elastic braces (LDEBs) are devices which do never yield subject to large deforma-tion under great earthquakes. In structures with LDEBs, elastic restoring force by LDEBs can improve seismic response under great earthquakes. In previous works, the effectiveness of LDEBs for the steel structures was confirmed by experimental tests and seismic response analyses. Here, the topology of LDEBs is determined by an optimization method, and seismic response analyses of RC portal frames with LDEBs are conducted. The effectiveness of LDEBs for the RC structures is discussed. RC portal frame are designed by Japanese seismic design code. LDEBs are equipped with the frame as knee braces. Seismic responses of not only the frame with LDEBs but also that without LDEBs are computed by dynamic nonlinear analysis software. In the analysis LDEBs are regarded as elastic bar elements. An input earthquake is JMA Kobe NS wave (1995 Kobe earthquakes). Hysteresis of story shear force and story drift, axial deformation of LDEBs, maximum and residual story drift are investigated. It is observed from computational results that LDEBs show remarkable improvements on maximum and residual story drifts of RC portal frame under a very large amplitude earthquake such as 1995 Kobe earthquake in Japan.</span></p> ]]> Seismic Response Analyses of RC Portal Frames with Large Deformable Elastic Braces kiichiro sawada doi: 10.2495/CMEM-V6-N5-880-886 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 880 10.2495/CMEM-V6-N5-880-886 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-880-886 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-868-879 The objective of this study is to investigate the effects of the uncertainties of major modelling parameters on the bridge seismic response. The parameters examined include the superstructure mass, concrete compressive strength, plastic hinge length and damping. For the purpose of the evaluation, an existing 3-span reinforced concrete highway bridge located in Montreal, Canada, was selected for the analysis. A three-dimensional model of the bridge was developed using SAP2000. Nonlinear time-history analyses were conducted in order to assess the effects of the uncertainty of each of modelling parameters mentioned above. Fifteen records obtained from earthquakes around the world were used as seismic excitations in the time-history analysis. The deck displacement and the column curvature ductility were chosen to investigate the effect of the uncertainty of the modelling parameters on the seismic response of the bridge. <![CDATA[ <p>The objective of this study is to investigate the effects of the uncertainties of major modelling parameters on the bridge seismic response. The parameters examined include the superstructure mass, concrete compressive strength, plastic hinge length and damping. For the purpose of the evaluation, an existing 3-span reinforced concrete highway bridge located in Montreal, Canada, was selected for the analysis. A three-dimensional model of the bridge was developed using SAP2000. Nonlinear time-history analyses were conducted in order to assess the effects of the uncertainty of each of modelling parameters mentioned above. Fifteen records obtained from earthquakes around the world were used as seismic excitations in the time-history analysis. The deck displacement and the column curvature ductility were chosen to investigate the effect of the uncertainty of the modelling parameters on the seismic response of the bridge.</p> ]]> Effects of Modelling Parameters on the Seismic Analysis of Bridges yuling gao lan lin doi: 10.2495/CMEM-V6-N5-868-879 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 868 10.2495/CMEM-V6-N5-868-879 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-868-879 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-857-867 Seismic pounding may cause severe structural damage to buildings, such as partial or total collapse, and/or significant damage to non-structural elements. This may be caused by the difference in the dynamic properties of each building, and also an insufficient gap between each building. In this study, a shaking table test of building models was carried out to investigate the seismic pounding of (1) low-rise buildings and (2) a low-rise to a mid-rise building. The structural specimens considered in this study were two single-storey models with a different horizontal stiffness, and one two-storey model. The test parameters were a) pairings of building models, b) the size of gaps, and c) ground acceleration records. Based on the test results, the increment of kinetic energy during the collision was evaluated. The main findings from the test results are as follows: (1) In the case of the pounding of low-rise buildings, the peak displacement of the stiffer building increases, while that of the more flexible building decreases; (2) In the case of the pounding of a low-rise building to a mid-rise building, the peak inter-storey drift of the low-rise building increases. In the mid-rise building, the peak inter-storey drift of the upper storey increases, while that of the lower storey decreases; (3) The sum of the increment kinetic energy during the collision was larger as the gap between buildings was smaller. A significant loss of kinetic energy was seen in buildings whose maximum kinetic energy is larger. (4) The building model of smaller kinetic energy may gain more energy owing to collisions, and the unfavourable effect of seismic pounding to the response is predominant. <![CDATA[ <p>Seismic pounding may cause severe structural damage to buildings, such as partial or total collapse, and/or significant damage to non-structural elements. This may be caused by the difference in the dynamic properties of each building, and also an insufficient gap between each building. In this study, a shaking table test of building models was carried out to investigate the seismic pounding of (1) low-rise buildings and (2) a low-rise to a mid-rise building. The structural specimens considered in this study were two single-storey models with a different horizontal stiffness, and one two-storey model. The test parameters were a) pairings of building models, b) the size of gaps, and c) ground acceleration records. Based on the test results, the increment of kinetic energy during the collision was evaluated. The main findings from the test results are as follows: (1) In the case of the pounding of low-rise buildings, the peak displacement of the stiffer building increases, while that of the more flexible building decreases; (2) In the case of the pounding of a low-rise building to a mid-rise building, the peak inter-storey drift of the low-rise building increases. In the mid-rise building, the peak inter-storey drift of the upper storey increases, while that of the lower storey decreases; (3) The sum of the increment kinetic energy during the collision was larger as the gap between buildings was smaller. A significant loss of kinetic energy was seen in buildings whose maximum kinetic energy is larger. (4) The building model of smaller kinetic energy may gain more energy owing to collisions, and the unfavourable effect of seismic pounding to the response is predominant.</p> ]]> Shaking Table Test of Adjacent Building Models Considering Pounding k. fujii y. sakai doi: 10.2495/CMEM-V6-N5-857-867 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 5 Article 857 10.2495/CMEM-V6-N5-857-867 https://www.acadlore.com/article/IJCMEM/2018_6_5/CMEM-V6-N5-857-867 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-iii The main scope of this issue is to provide to the international technical and academic community information about the latest developments on the interaction and the complementary aspects of computational methods and experimental measurements. The main attention and relevance being committed to their reciprocal and advantageous integrationIt is recognised that the constant progresses in computers efficiency and numerical techniques are producing a steady growth of computational simulations, which nowadays applies to an everwidening range of engineering problems. Nonetheless, even if these simulations are continuously expanding and improving, there still exists the need for their validation, especially for the more complex cases, which can be only accomplished by performing dedicated experimental tests. Experimental techniques are becoming increasingly complex and sophisticated so that both their running as well as data collection can only be performed by computers. Finally, it must be emphasised that, for the majority of measurements, the data obtained must be processed numerically.This issue contains a substantial number of excellent scientific papers, which present several advanced approaches to the application of Computational Methods and Experimental Measurements.The EditorsAlicante, Spain2017 <![CDATA[ <p>The main scope of this issue is to provide to the international technical and academic community information about the latest developments on the interaction and the complementary aspects of computational methods and experimental measurements. The main attention and relevance being committed to their reciprocal and advantageous integration</p><p style="text-align: justify">It is recognised that the constant progresses in computers efficiency and numerical techniques are producing a steady growth of computational simulations, which nowadays applies to an everwidening range of engineering problems. Nonetheless, even if these simulations are continuously expanding and improving, there still exists the need for their validation, especially for the more complex cases, which can be only accomplished by performing dedicated experimental tests. Experimental techniques are becoming increasingly complex and sophisticated so that both their running as well as data collection can only be performed by computers. Finally, it must be emphasised that, for the majority of measurements, the data obtained must be processed numerically.</p><p style="text-align: justify">This issue contains a substantial number of excellent scientific papers, which present several advanced approaches to the application of Computational Methods and Experimental Measurements.</p><p style="text-align: justify">The Editors</p><p style="text-align: justify">Alicante, Spain</p><p style="text-align: justify">2017</p> ]]> Preface yolanda villacampa giovanni carlomagno salvador ivorra carlos a. brebbia doi: 10.2495/CMEM-V6-N4-iii International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 0 10.2495/CMEM-V6-N4-iii https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-iii https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-835-846 The use of lightweight concrete allows great flexibility and cost savings when it is used in building construction having a positive impact on the energy consumption of buildings due to its good thermal characteristics. However, it is also known that the differences between the densities of the materials used to produce these concretes make it highly susceptible to the segregation phenomenon. The main objective of the present work is to present a method to quantify this phenomenon using techniques of image analysis. In this work, a lightweight concrete produced was molded in cylindrical molds using different times of internal vibration and causing different degrees of segregation. The samples were cured, vertically saw-cut in two pieces (halves) and the sections were photographed. Subsequently, the halves were saw-cut horizontally in four equal parts and posteriorly their densities were determined experimentally. The densities obtained were used to calculate the segregation index of each sample (experimental method). Furthermore, the photographed sections were processed using image analysis software in order to determine the volumetric proportions of aggregates in each sample (noise reduction, threshold adjustment, binarization and fill holes). The processed images were used to calculate the densities and segregation index of the lightweight concrete produced through image analysis. In addition, using the photographed sections, a vertical density profile was programmed to analyze the distribution of the lightweight concrete components (mortar and aggregate). Finally, the results obtained experimentally and through image analysis were compared. This study demonstrates that the image analysis allows a deeper knowledge of the behavior of segregated concrete. <![CDATA[ <p>The use of lightweight concrete allows great flexibility and cost savings when it is used in building construction having a positive impact on the energy consumption of buildings due to its good thermal characteristics. However, it is also known that the differences between the densities of the materials used to produce these concretes make it highly susceptible to the segregation phenomenon. The main objective of the present work is to present a method to quantify this phenomenon using techniques of image analysis. In this work, a lightweight concrete produced was molded in cylindrical molds using different times of internal vibration and causing different degrees of segregation. The samples were cured, vertically saw-cut in two pieces (halves) and the sections were photographed. Subsequently, the halves were saw-cut horizontally in four equal parts and posteriorly their densities were determined experimentally. The densities obtained were used to calculate the segregation index of each sample (experimental method). Furthermore, the photographed sections were processed using image analysis software in order to determine the volumetric proportions of aggregates in each sample (noise reduction, threshold adjustment, binarization and fill holes). The processed images were used to calculate the densities and segregation index of the lightweight concrete produced through image analysis. In addition, using the photographed sections, a vertical density profile was programmed to analyze the distribution of the lightweight concrete components (mortar and aggregate). Finally, the results obtained experimentally and through image analysis were compared. This study demonstrates that the image analysis allows a deeper knowledge of the behavior of segregated concrete.</p> ]]> Image Analysis Applications for the Study of Segregation in Lightweight Concretes afonso m. solak antonio j. tenza-abril francisco baeza-brotons doi: 10.2495/CMEM-V6-N4-835-846 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 835 10.2495/CMEM-V6-N4-835-846 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-835-846 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-827-834 This research reports a vehicle occupant restraint system design that takes account of uncertainties of crash conditions and situations by using a multi-objective robust design optimization method called MORDO. The vehicle occupant restraint system is composed of restraint equipment, such as an airbag, a seatbelt and a knee bolster. The optimization aims to improve the safety performance of the system and its robustness simultaneously. The safety of the system is evaluated by some indexes based on some safety regulations, which are calculated by response surface model of an occupant at a crash. In addition, its robustness is evaluated by the mean value and the standard deviation of objective functions, which are calculated by using Monte Carlo simulation based on a certain probabilistic distribution in space of design variables around each design candidate. Some helpful information for designing the restraint systems, such as trade-off information of safety performance and its robustness, are provided by visualizing and analysing the Pareto optimal solutions. <![CDATA[ <p>This research reports a vehicle occupant restraint system design that takes account of uncertainties of crash conditions and situations by using a multi-objective robust design optimization method called MORDO. The vehicle occupant restraint system is composed of restraint equipment, such as an airbag, a seatbelt and a knee bolster. The optimization aims to improve the safety performance of the system and its robustness simultaneously. The safety of the system is evaluated by some indexes based on some safety regulations, which are calculated by response surface model of an occupant at a crash. In addition, its robustness is evaluated by the mean value and the standard deviation of objective functions, which are calculated by using Monte Carlo simulation based on a certain probabilistic distribution in space of design variables around each design candidate. Some helpful information for designing the restraint systems, such as trade-off information of safety performance and its robustness, are provided by visualizing and analysing the Pareto optimal solutions.</p> ]]> Vehicle Occupant Restraint System Design Under Uncertainty by Using Multi-Objective Robust Design Optimization hirosuke horii doi: 10.2495/CMEM-V6-N4-827-834 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 827 10.2495/CMEM-V6-N4-827-834 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-827-834 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-814-826 The effect of fluid rheology on acoustic streaming was studied experimentally using a low frequency (600Hz–15kHz) underwater acoustic transducer. The fluid rheology was compared with deionized water and non-Newtonian fluid polyanionic cellulose (PAC). Streaming effect generated by the transducer in a static liquid medium was visualized by particle image velocimetry (PIV) method. The motion of fluid was optically visualized using light scattering ‘seeding’ particles. Velocity profiles induced by the acoustic streaming have different shapes and range of magnitudes. First, the acoustic streaming in deionized water was visualized for different frequencies and pressure amplitudes (voltages). A maximum of 1 g/L PAC was then introduced in smaller steps for some selected frequency and voltage settings. The streaming disappeared completely when the total concentration of the fluid medium reached 0.19 g/L PAC. The measured streaming velocities are found to be in the range of 2.1 to 9.9 cm/s for water and it is proportional to the applied voltage and the operating frequency of the transducer. When introducing PAC, the streaming velocity within water gradually decreased until zero due to the attenuation of acoustic waves by viscous effects. This confirms that the streaming velocity is approximately inversely proportional to the bulk viscosity of the medium. The velocity vectors and the streaming velocity maps illustrate the induced non-linearities of the fluid medium due to the acoustic propagation. The results are part of a comprehensive study aimed at investigating the influence of acoustic vibration on particle settling in non-Newtonian fluids. <![CDATA[ <p>The effect of fluid rheology on acoustic streaming was studied experimentally using a low frequency (600Hz–15kHz) underwater acoustic transducer. The fluid rheology was compared with deionized water and non-Newtonian fluid polyanionic cellulose (PAC). Streaming effect generated by the transducer in a static liquid medium was visualized by particle image velocimetry (PIV) method. The motion of fluid was optically visualized using light scattering ‘seeding’ particles. Velocity profiles induced by the acoustic streaming have different shapes and range of magnitudes. First, the acoustic streaming in deionized water was visualized for different frequencies and pressure amplitudes (voltages). A maximum of 1 g/L PAC was then introduced in smaller steps for some selected frequency and voltage settings. The streaming disappeared completely when the total concentration of the fluid medium reached 0.19 g/L PAC. The measured streaming velocities are found to be in the range of 2.1 to 9.9 cm/s for water and it is proportional to the applied voltage and the operating frequency of the transducer. When introducing PAC, the streaming velocity within water gradually decreased until zero due to the attenuation of acoustic waves by viscous effects. This confirms that the streaming velocity is approximately inversely proportional to the bulk viscosity of the medium. The velocity vectors and the streaming velocity maps illustrate the induced non-linearities of the fluid medium due to the acoustic propagation. The results are part of a comprehensive study aimed at investigating the influence of acoustic vibration on particle settling in non-Newtonian fluids.</p> ]]> Visualisation of Acoustic Streaming Using PIV in Newtonian and Non-Newtonian Liquids maduranga amaratunga rune w. time doi: 10.2495/CMEM-V6-N4-814-826 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 814 10.2495/CMEM-V6-N4-814-826 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-814-826 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-804-813 Numerical methods, and especially the finite-element method (FEM), are usually adopted for the analyses of shockwave propagation in nonlinear inelastic media. Noise or spurious oscillations, in the calculated stresses and displacements, frequently appear in the FEM solutions. This article introduces and describes a numeric filter based on least-square analysis that can smooth out such fictitious noise. The sliced least-square method (SLSM) filter is implemented in a finite elements program that solves 1D time integration of dynamic equilibrium sets of equations that simulate shockwave propagation in multi-layered soils supported by a hard stratum. Elastic and elasto-viscoplastic material models with dynamic yield surface constitutive relations are invoked to model sand, clay, and concrete materials in the analyses. Results of the analyses of shockwave propagation in layers of soil and concrete without the filter are compared with identical conditions with the inclusion of the new filter in the finite-element program. Oscillations in calculated stresses and displacements were observed in the results when no filter was included in the solution program. Solution results showed little or no noise with the application of the new filter. The predicted FEM analyses results were compared with physical test results with very good to excellent comparisons obtained. <![CDATA[ <p>Numerical methods, and especially the finite-element method (FEM), are usually adopted for the analyses of shockwave propagation in nonlinear inelastic media. Noise or spurious oscillations, in the calculated stresses and displacements, frequently appear in the FEM solutions. This article introduces and describes a numeric filter based on least-square analysis that can smooth out such fictitious noise. The sliced least-square method (SLSM) filter is implemented in a finite elements program that solves 1D time integration of dynamic equilibrium sets of equations that simulate shockwave propagation in multi-layered soils supported by a hard stratum. Elastic and elasto-viscoplastic material models with dynamic yield surface constitutive relations are invoked to model sand, clay, and concrete materials in the analyses. Results of the analyses of shockwave propagation in layers of soil and concrete without the filter are compared with identical conditions with the inclusion of the new filter in the finite-element program. Oscillations in calculated stresses and displacements were observed in the results when no filter was included in the solution program. Solution results showed little or no noise with the application of the new filter. The predicted FEM analyses results were compared with physical test results with very good to excellent comparisons obtained.</p> ]]> Noise Filtration of Shockwave Propagation in Multi-Layered Soils laith i. namiq yousof q. abdaljalil doi: 10.2495/CMEM-V6-N4-804-813 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 804 10.2495/CMEM-V6-N4-804-813 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-804-813 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-797-803 A biomechanical model and mathematical formulation of the problem of propulsion of a solid nondeformable pellet by an isolated segment of the colon are presented. The organ is modeled as a soft orthotropic cylindrical biological shell. Its wall is reinforced by transversely isotropic muscle fibers of orthogonal type of weaving embedded in a connective tissue stroma. The mechanical properties of the wall are assumed to be nonlinear, deformations are finite. The longitudinal and circular smooth muscle syncitia possesses electrical properties and are under control of a pacemaker, which is represented by the interstitial cell of Cajal. The model describes the dynamics of the generation and propagation of the mechanical waves of contraction–relaxation along the surface of the bioshell and propulsion of the pellet. The governing system of equations has been solved numerically. The combined finite-difference and finite-element method has been used. The results of numerical experiments demonstrate that pendular movements alone provide a normal transit, without mixing though, of the bolus. Non-propagating segmental contractions show small amplitude librations of the pellet without its visible propulsion. Only the coordinated activity of the longitudinal and circular smooth muscle layers in a form of the peristaltic reflex provides physiologically significant simultaneous propulsion and mixing of the intraluminal content. <![CDATA[ <p>A biomechanical model and mathematical formulation of the problem of propulsion of a solid nondeformable pellet by an isolated segment of the colon are presented. The organ is modeled as a soft orthotropic cylindrical biological shell. Its wall is reinforced by transversely isotropic muscle fibers of orthogonal type of weaving embedded in a connective tissue stroma. The mechanical properties of the wall are assumed to be nonlinear, deformations are finite. The longitudinal and circular smooth muscle syncitia possesses electrical properties and are under control of a pacemaker, which is represented by the interstitial cell of Cajal. The model describes the dynamics of the generation and propagation of the mechanical waves of contraction–relaxation along the surface of the bioshell and propulsion of the pellet. The governing system of equations has been solved numerically. The combined finite-difference and finite-element method has been used. The results of numerical experiments demonstrate that pendular movements alone provide a normal transit, without mixing though, of the bolus. Non-propagating segmental contractions show small amplitude librations of the pellet without its visible propulsion. Only the coordinated activity of the longitudinal and circular smooth muscle layers in a form of the peristaltic reflex provides physiologically significant simultaneous propulsion and mixing of the intraluminal content.</p> ]]> Computer-Aided Model of Colonic Propulsive Activity o. al qatrawi r.n. miftahof doi: 10.2495/CMEM-V6-N4-797-803 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 797 10.2495/CMEM-V6-N4-797-803 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-797-803 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-785-796 A methodology for goal-oriented active learning with local model networks (LMNs) is proposed. It is applied for the generation of training data for a computational fluid dynamics (CFD) metamodel. The used metamodel is an LMN trained with data originating from CFD simulations. This metamodel describes the total-to-static efficiency for a given design point, defined by the pressure rise at a specific volume flow rate, depending on geometrical parameters of an impeller of centrifugal fans. The goal- oriented nature originates from three main targets that are addressed simultaneously during the active learning procedure. (I) The concentration on possibly optimal geometries and (II) the focus on areas in the input space where the metamodel’s performance is considered to be worst. Additionally, (III) new measurements should differ from already simulated geometries as much as possible. With these goals three important issues in modeling are addressed simultaneously: (I) optimality, (II) model bias, (III) model variance/uniformly space-filling property. In order to fulfill all goals, special properties of LMNs are utilized (embedded approach). Through the structure of LMNs, it is possible to assign local model errors to specific areas in the input space. New measurements are preferably placed in such high-error regions, while concentrating on presumably optimal geometries that differ most from the ones already available in the training data. In the field of fluid machinery, the range of achievable design points is usually identified by the Cordier diagram. While the design points obtained in the passive learning phase fairly agree with the standard Cordier diagram, an extension of achievable design points was observed due to the proposed goal-oriented learning strategy. In addition, the total-to-static efficiency could be improved in some areas of the Cordier diagram. <![CDATA[ <p>A methodology for goal-oriented active learning with local model networks (LMNs) is proposed. It is applied for the generation of training data for a computational fluid dynamics (CFD) metamodel. The used metamodel is an LMN trained with data originating from CFD simulations. This metamodel describes the total-to-static efficiency for a given design point, defined by the pressure rise at a specific volume flow rate, depending on geometrical parameters of an impeller of centrifugal fans. The goal- oriented nature originates from three main targets that are addressed simultaneously during the active learning procedure. (I) The concentration on possibly optimal geometries and (II) the focus on areas in the input space where the metamodel’s performance is considered to be worst. Additionally, (III) new measurements should differ from already simulated geometries as much as possible. With these goals three important issues in modeling are addressed simultaneously: (I) optimality, (II) model bias, (III) model variance/uniformly space-filling property. In order to fulfill all goals, special properties of LMNs are utilized (embedded approach). Through the structure of LMNs, it is possible to assign local model errors to specific areas in the input space. New measurements are preferably placed in such high-error regions, while concentrating on presumably optimal geometries that differ most from the ones already available in the training data. In the field of fluid machinery, the range of achievable design points is usually identified by the Cordier diagram. While the design points obtained in the passive learning phase fairly agree with the standard Cordier diagram, an extension of achievable design points was observed due to the proposed goal-oriented learning strategy. In addition, the total-to-static efficiency could be improved in some areas of the Cordier diagram.</p> ]]> Goal-Oriented Active Learning with Local Model Networks julian belz konrad bamberger oliver nelles thomas carolus doi: 10.2495/CMEM-V6-N4-785-796 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 785 10.2495/CMEM-V6-N4-785-796 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-785-796 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-772-784 Understanding human intention is an important ability for an intelligent robot to collaborate with a human to accomplish various tasks. During collaboration, a robot with such ability can predict the successive actions that a human partner intends to perform, provide necessary assistance and support, and remind for the missing and failure actions from the human to achieve a desired task purpose. This paper presents a framework that allows a robot to automatically recognize and infer the action intention of a human partner based on visualization, in which an inverse-reinforcement learning (IRL) system is learnt based on the observed human demonstration and used to infer the human successive actions. Compared to other systems based on reinforcement learning, the reward of a Markov-Decision process (MDP) is directly learned from the demonstration. In our experiment, we provide some examples of the proposed framework which yields promising results with coffee-making and pick-and-place tasks. Regarding to the human-intention model based on IRL, the coffee-making experiment indicates that the action is globally predicted because the action of putting down the water pot is selected instead of pouring water when the cup is already filled with water. <![CDATA[ <p>Understanding human intention is an important ability for an intelligent robot to collaborate with a human to accomplish various tasks. During collaboration, a robot with such ability can predict the successive actions that a human partner intends to perform, provide necessary assistance and support, and remind for the missing and failure actions from the human to achieve a desired task purpose. This paper presents a framework that allows a robot to automatically recognize and infer the action intention of a human partner based on visualization, in which an inverse-reinforcement learning (IRL) system is learnt based on the observed human demonstration and used to infer the human successive actions. Compared to other systems based on reinforcement learning, the reward of a Markov-Decision process (MDP) is directly learned from the demonstration. In our experiment, we provide some examples of the proposed framework which yields promising results with coffee-making and pick-and-place tasks. Regarding to the human-intention model based on IRL, the coffee-making experiment indicates that the action is globally predicted because the action of putting down the water pot is selected instead of pouring water when the cup is already filled with water.</p> ]]> Active Intention Inference for Robot-Human Collaboration hsien-i lin xuan-anh nguyen wei-kai chen doi: 10.2495/CMEM-V6-N4-772-784 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 772 10.2495/CMEM-V6-N4-772-784 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-772-784 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-764-771 In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges. <![CDATA[ <p>In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges.</p> ]]> A Crowd-Structure Interaction Model to Analyze the Lateral Lock-in Phenomenon on Footbridges javier fernando jiménez-alonso andres sáez elsa caetano alvaro cunha doi: 10.2495/CMEM-V6-N4-764-771 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 764 10.2495/CMEM-V6-N4-764-771 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-764-771 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-749-763 The problem of indentation of ductile materials by ball indenters is, in this paper, addressed by numerical modelling. A finite element model is built using general purpose software. The axisymmetry of the problem is taken into account thus reducing its dimensionality. Particular attention is given to contact modelling as well as mesh design for optimal performance. The model is validated by comparing its predictions to the exact elastic solution as well as experimental measurements from elasto-plastic indentation tests. In the latter case, indenter imperfection is accounted for and mate rial input are stress-strain curves originating from tensile tests. The sensitivity of numerical results to indenter elasticity is investigated. The effect of friction and specimen creep during indentation on load-displacement predictions is also assessed. <![CDATA[ <p>The problem of indentation of ductile materials by ball indenters is, in this paper, addressed by numerical modelling. A finite element model is built using general purpose software. The axisymmetry of the problem is taken into account thus reducing its dimensionality. Particular attention is given to contact modelling as well as mesh design for optimal performance. The model is validated by comparing its predictions to the exact elastic solution as well as experimental measurements from elasto-plastic indentation tests. In the latter case, indenter imperfection is accounted for and mate rial input are stress-strain curves originating from tensile tests. The sensitivity of numerical results to indenter elasticity is investigated. The effect of friction and specimen creep during indentation on load-displacement predictions is also assessed.</p> ]]> Finite Element Simulation of Spherical Indentation Experiments s. syngellakis h. habbab b. g. mellor doi: 10.2495/CMEM-V6-N4-749-763 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 749 10.2495/CMEM-V6-N4-749-763 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-749-763 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-737-748 Performance and emission characteristics of a gasoline direct injection (GDI) engine are mainly influenced by the in-cylinder mixture preparation. However, in these engines, mixture formation depends upon many factors viz., fuel injection strategy and parameters, mode of operation, engine geometry, etc. Therefore, understanding the mixture formation, under various engine operating conditions and fuel system configurations, is very much essential. In this study, an attempt has been made to understand the effect of fuel injector-hole diameter and fuel injection timing on the mixture formation in a four-stroke, wall-guided GDI engine using computational fluid dynamics (CFD) analysis. The CFD simulations are carried out from inlet valve opening (IVO) to exhaust valve opening (EVO) period using the CONVERGE. The CFD models used are validated with the available data from the literature. The engine considered has a compression ratio (CR) of 11.5. All the CFD simulations are carried out at the engine speed of 2000 rev/min. Three fuel injector-hole diameters viz., 0.1, 0.14 and 0.18 mm and three fuel injection timings viz., 605, 620 and 635 crank angle degree (CAD) are considered for the analysis. The mixture formation is analyzed in the vicinity of the spark plug and at other parts of the combustion chamber. From the results, it is found that higher nozzle-hole diameter yielded very rich mixture zones near spark plug. Also, lower nozzle-hole diameter and retarded fuel injection timing showed higher indicated mean effective pressure (IMEP). <![CDATA[ <p>Performance and emission characteristics of a gasoline direct injection (GDI) engine are mainly influenced by the in-cylinder mixture preparation. However, in these engines, mixture formation depends upon many factors viz., fuel injection strategy and parameters, mode of operation, engine geometry, etc. Therefore, understanding the mixture formation, under various engine operating conditions and fuel system configurations, is very much essential. In this study, an attempt has been made to understand the effect of fuel injector-hole diameter and fuel injection timing on the mixture formation in a four-stroke, wall-guided GDI engine using computational fluid dynamics (CFD) analysis. The CFD simulations are carried out from inlet valve opening (IVO) to exhaust valve opening (EVO) period using the CONVERGE. The CFD models used are validated with the available data from the literature. The engine considered has a compression ratio (CR) of 11.5. All the CFD simulations are carried out at the engine speed of 2000 rev/min. Three fuel injector-hole diameters viz., 0.1, 0.14 and 0.18 mm and three fuel injection timings viz., 605, 620 and 635 crank angle degree (CAD) are considered for the analysis. The mixture formation is analyzed in the vicinity of the spark plug and at other parts of the combustion chamber. From the results, it is found that higher nozzle-hole diameter yielded very rich mixture zones near spark plug. Also, lower nozzle-hole diameter and retarded fuel injection timing showed higher indicated mean effective pressure (IMEP).</p> ]]> Effect of Fuel Injector Hole Diameter and Injection Timing on the Mixture Formation in a GDI Engine - A CFD Study priyanka d. jadhav j. m. mallikarjuna doi: 10.2495/CMEM-V6-N4-737-748 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 737 10.2495/CMEM-V6-N4-737-748 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-737-748 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-726-736 In this work, numerical models were obtained for describing the segregation phenomenon in lightweight aggregate concrete. To that end, a numerical methodology based on the generation of geometric models of finite elements has been applied, selecting those that describe better this phenomenon. The use of lightweight aggregate concretes (LWC) allows greater design flexibility and substantial cost savings. It is also well known that it contributes to a positive impact on the energy consumption of a building due to the high-thermal resistance values. However, lightweight concretes are susceptible to present aggregate segregation due to density differences between its components during concrete vibration. Segregation in concrete may strongly affect the concrete global properties. This fact justifies the needs for the identification and quantification of this phenomenon, in order to estimate the concrete segregation experimentally, a LWC was mixed in laboratory conditions. Controlled segregation was caused applying different times of internal vibration in a cylinder specimen. The specimens were horizontally sectioned in order to obtain the density in each section because the segregation index can be estimated obtaining a relation by comparing the densities of the upper and lower parts. Firstly, ANOVA test was performed to determine the statistical significance (p <![CDATA[ <p>In this work, numerical models were obtained for describing the segregation phenomenon in lightweight aggregate concrete. To that end, a numerical methodology based on the generation of geometric models of finite elements has been applied, selecting those that describe better this phenomenon. The use of lightweight aggregate concretes (LWC) allows greater design flexibility and substantial cost savings. It is also well known that it contributes to a positive impact on the energy consumption of a building due to the high-thermal resistance values. However, lightweight concretes are susceptible to present aggregate segregation due to density differences between its components during concrete vibration. Segregation in concrete may strongly affect the concrete global properties. This fact justifies the needs for the identification and quantification of this phenomenon, in order to estimate the concrete segregation experimentally, a LWC was mixed in laboratory conditions. Controlled segregation was caused applying different times of internal vibration in a cylinder specimen. The specimens were horizontally sectioned in order to obtain the density in each section because the segregation index can be estimated obtaining a relation by comparing the densities of the upper and lower parts. Firstly, ANOVA test was performed to determine the statistical significance (p<0.05) of the differences in the density of the different sections, differences in the aggregate type and differences in the time of concrete vibration. Results show that there is a significant difference of each section and there is no significant difference of each lightweight aggregate used to mix the concrete in spite of their different density. In order to model the segregation in the LWC, at first, linear models were considered and rejected because for not explaining the phenomenon. However, the application of numerical models shows good results to describe the phenomenon of segregation in LWC.</p> ]]> Numerical Model for Describing the Segregation Phenomenon in Lightweight Concrete Using Density Sections a. j. tenza-abril y. villacampa f. baeza-brotons j. f. navarro-gonzález a. m. solak doi: 10.2495/CMEM-V6-N4-726-736 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 726 10.2495/CMEM-V6-N4-726-736 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-726-736 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-716-725 Free vibrations of beams and rods made of nano-materials are investigated. It is assumed that the dimensions of cross sections of nano-beams are piecewise constant and that the beams are weakened with cracks. It is expected that the vibrational behaviour of the nano-material can be described within the non-local theory of elasticity and that the crack induces additional local compliance. The latter is coupled with the stress intensity coefficient at the crack tip. <![CDATA[ <p>Free vibrations of beams and rods made of nano-materials are investigated. It is assumed that the dimensions of cross sections of nano-beams are piecewise constant and that the beams are weakened with cracks. It is expected that the vibrational behaviour of the nano-material can be described within the non-local theory of elasticity and that the crack induces additional local compliance. The latter is coupled with the stress intensity coefficient at the crack tip.</p> ]]> Free Vibrations of Stepped Nano-Beams jaan lellep artur lenbaum doi: 10.2495/CMEM-V6-N4-716-725 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 716 10.2495/CMEM-V6-N4-716-725 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-716-725 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-703-715 It is estimated that currently the consumption of natural aggregates used annually in the production of concrete in the world is around 10 billion tons. Moreover, more than 10 million tons of waste is generated annually from the construction industry. The incorporation of recycled aggregates in the production of concrete arises mainly due to an environmental factor, because it emphasizes the reduction in the consumption of raw materials, reduction of the emission of pollutants to the atmosphere derived from the processes of extraction of natural aggregates, between others. Several studies quantifies the decrease of mechanical properties according to the percentage of replacement of natural aggregate by recycled concrete aggregate. In the present study the authors provide several nonlinear models, which are able to predict the modulus of elasticity behaviour of the concrete manufactured with recycled aggregate. A database was composed of 147 different mixtures of recycled aggregate concrete collected from publications of scientific journals. The database has been used to introduce it to the software Polimodels. Polimodels is able to generate different models using different nonlinear regression algorithms. Six different models for the modulus of elasticity are proposed, dependents on certain physical and mechanical parameters of the recycled aggregate, as the following; the percentage of absorption, Los Angeles abrasion coefficient, and the percentage of substitution of natural aggregate by recycled aggregate. It is possible to appreciate the remarkable reduction in the modulus of elasticity due to the increase of recycled aggregates in the concrete. When the models have more independent variables a better adjustment is noticed that help us to improve the prediction of the modulus of elasticity of recycled aggregate concrete. <![CDATA[ <p>It is estimated that currently the consumption of natural aggregates used annually in the production of concrete in the world is around 10 billion tons. Moreover, more than 10 million tons of waste is generated annually from the construction industry. The incorporation of recycled aggregates in the production of concrete arises mainly due to an environmental factor, because it emphasizes the reduction in the consumption of raw materials, reduction of the emission of pollutants to the atmosphere derived from the processes of extraction of natural aggregates, between others. Several studies quantifies the decrease of mechanical properties according to the percentage of replacement of natural aggregate by recycled concrete aggregate. In the present study the authors provide several nonlinear models, which are able to predict the modulus of elasticity behaviour of the concrete manufactured with recycled aggregate. A database was composed of 147 different mixtures of recycled aggregate concrete collected from publications of scientific journals. The database has been used to introduce it to the software Polimodels. Polimodels is able to generate different models using different nonlinear regression algorithms. Six different models for the modulus of elasticity are proposed, dependents on certain physical and mechanical parameters of the recycled aggregate, as the following; the percentage of absorption, Los Angeles abrasion coefficient, and the percentage of substitution of natural aggregate by recycled aggregate. It is possible to appreciate the remarkable reduction in the modulus of elasticity due to the increase of recycled aggregates in the concrete. When the models have more independent variables a better adjustment is noticed that help us to improve the prediction of the modulus of elasticity of recycled aggregate concrete.</p> ]]> Predicting Modulus of Elasticity of Recycled Aggregate Concrete Using Nonlinear Mathematical Models junior a. reyes-sánchez antonio j. tenza-abril ferran verdu josé a. reyes perales doi: 10.2495/CMEM-V6-N4-703-715 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 703 10.2495/CMEM-V6-N4-703-715 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-703-715 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-691-702 The formation mechanism of inclined fatigue cracks in ultrafine-grained Cu processed by equal channel angular pressing was studied by using a smooth specimen with a small blind hole. The crack growth direction depended on the location of drilling hole along the circumferential direction of the round bar specimen and on the applied stress amplitudes. Although the low-cycle fatigue crack growth paths inclined 45° and 90° to the loading-axis were observed in the different locations on the surface, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the shear plane of the final processing. To study the crack growth behaviour, surface damage around the crack paths formed by the two-step fatigue stress tests was observed. Profile of crack face was examined, showing the aspect ratios (b/a) of b/a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions with respect to the loading axis, respectively. The role of the microstructure and deformation mode at the crack-tip areas on the formation of crack paths parallel to the shear plane of the final pressing was discussed in terms of the microstructural evolution caused by cyclic stressing and the mixed-mode stress intensity factor. <![CDATA[ <p>The formation mechanism of inclined fatigue cracks in ultrafine-grained Cu processed by equal channel angular pressing was studied by using a smooth specimen with a small blind hole. The crack growth direction depended on the location of drilling hole along the circumferential direction of the round bar specimen and on the applied stress amplitudes. Although the low-cycle fatigue crack growth paths inclined 45° and 90° to the loading-axis were observed in the different locations on the surface, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the shear plane of the final processing. To study the crack growth behaviour, surface damage around the crack paths formed by the two-step fatigue stress tests was observed. Profile of crack face was examined, showing the aspect ratios (<em>b/a</em>) of<em> b/a</em> = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions with respect to the loading axis, respectively. The role of the microstructure and deformation mode at the crack-tip areas on the formation of crack paths parallel to the shear plane of the final pressing was discussed in terms of the microstructural evolution caused by cyclic stressing and the mixed-mode stress intensity factor.</p> ]]> Relationship Between Shear Plane of the Final Pressing and Fatigue Crack Growth Behaviour of Round-Bar Specimens of Cu Processed by ECAP masahiro goto takaei yamamoto seung zeon han jee hyuk ahn junichi kitamura kusno kamil terutoshi yakushiji toshiki masuda takashi iwamura sangshik kim doi: 10.2495/CMEM-V6-N4-691-702 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 691 10.2495/CMEM-V6-N4-691-702 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-691-702 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-679-690 The main purpose of this work is to employ the Adomian modified decomposition method (AMDM) to calculate free transverse vibrations of non-uniform cantilever beams carrying a transversely and axially eccentric tip mass. The effects of the variable axial force are taken into account here, and Hamilton’s principle and Timoshenko beam theory are used to obtain a single governing non-linear partial differential equation of the system as well as the appropriate boundary conditions. Two product non-linearities result from the analysis and the respective Cauchy products are computed using Adomian polynomials. The use of AMDM to make calculations for such a cantilever beam/tip mass arrangement has not, to the authors’ knowledge, been used before. The obtained analytical results are compared with numerical calculations reported in the literature and good agreement is observed. The qualitative and quantitative knowledge gained from this research is expected to enable the study of the effects of an eccentric tip mass and beam non-uniformity on the vibration of beams for improved dynamic performance. <![CDATA[ <p>The main purpose of this work is to employ the Adomian modified decomposition method (AMDM) to calculate free transverse vibrations of non-uniform cantilever beams carrying a transversely and axially eccentric tip mass. The effects of the variable axial force are taken into account here, and Hamilton’s principle and Timoshenko beam theory are used to obtain a single governing non-linear partial differential equation of the system as well as the appropriate boundary conditions. Two product non-linearities result from the analysis and the respective Cauchy products are computed using Adomian polynomials. The use of AMDM to make calculations for such a cantilever beam/tip mass arrangement has not, to the authors’ knowledge, been used before. The obtained analytical results are compared with numerical calculations reported in the literature and good agreement is observed. The qualitative and quantitative knowledge gained from this research is expected to enable the study of the effects of an eccentric tip mass and beam non-uniformity on the vibration of beams for improved dynamic performance.</p> ]]> Simulation of the Vibrations of a Non-uniform Beam Loaded with Both A Transversely and Axially Eccentric Tip Mass desmond adair martin jaeger doi: 10.2495/CMEM-V6-N4-679-690 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 679 10.2495/CMEM-V6-N4-679-690 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-679-690 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-667-678 The present paper describes the application of an evolutionary algorithm to the optimum design of the reinforcement of timber beams using FRP laminates and sheets. The objective function is the material cost of the strengthening and is subjected to ten constraints derived from the ultimate limit states for flexural and shear behaviour as well as the serviceability limit states. A genetic algorithm is used and the optimization problem is transformed into an unconstrained one by means of an adaptive penalty function. The design variables are the CFRP and GFRP mechanical properties and dimensions and they are encoded in a binary chromosome: type of composite material (CFRP or GFRP), reinforcement mechanical properties and geometric configuration. The search space for the minimum cost consists of 65 billion possible solutions. The crossover operator switches randomly between a fenotype crossover and flat crossover. An adaptive mutation scheme has been as well as an elitism criterion. The algorithm has been used for obtaining optimum designs in several specific load and geometry cases of glued laminated timber beams. The objective is finding whether there are specific reinforcement configurations more feasible for a certain loading situations: short or long beams and lower or higher loading increments. Five cases have been analysed. In the first three cases the length of the beams has constant values of 2, 2.5 and 3 m, whereas the value of loading was variable. In the latter case, the value of the load was fixed and the length of the beam was variable. The analysis of the results shows that the GFRP reinforcement is more efficient than CFRP for designs governed by shear failure, whereas CFRP is more effective in the case of flexural failure and deflection controlled strengthening of timber beams. <![CDATA[ <p>The present paper describes the application of an evolutionary algorithm to the optimum design of the reinforcement of timber beams using FRP laminates and sheets. The objective function is the material cost of the strengthening and is subjected to ten constraints derived from the ultimate limit states for flexural and shear behaviour as well as the serviceability limit states. A genetic algorithm is used and the optimization problem is transformed into an unconstrained one by means of an adaptive penalty function. The design variables are the CFRP and GFRP mechanical properties and dimensions and they are encoded in a binary chromosome: type of composite material (CFRP or GFRP), reinforcement mechanical properties and geometric configuration. The search space for the minimum cost consists of 65 billion possible solutions. The crossover operator switches randomly between a fenotype crossover and flat crossover. An adaptive mutation scheme has been as well as an elitism criterion. The algorithm has been used for obtaining optimum designs in several specific load and geometry cases of glued laminated timber beams. The objective is finding whether there are specific reinforcement configurations more feasible for a certain loading situations: short or long beams and lower or higher loading increments. Five cases have been analysed. In the first three cases the length of the beams has constant values of 2, 2.5 and 3 m, whereas the value of loading was variable. In the latter case, the value of the load was fixed and the length of the beam was variable. The analysis of the results shows that the GFRP reinforcement is more efficient than CFRP for designs governed by shear failure, whereas CFRP is more effective in the case of flexural failure and deflection controlled strengthening of timber beams.</p> ]]> Application of An Evolutionary Algorithm to Reduce the Cost of Strengthening of Timber Beams francisco b. varona david bru-ort francisco j. baeza salvador ivorra doi: 10.2495/CMEM-V6-N4-667-678 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 667 10.2495/CMEM-V6-N4-667-678 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-667-678 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-656-666 In drive systems and component technology a high reliability is very important for machines. Machine element dimensions are calculated for reliability. The properties for these elements are based on conventional manufacturing techniques. Very high stresses are applied on bearings in their operating time. To improve the endurance life, residual stresses can be induced into the subsurface zone. In contrast to a conventional grinding process, the mechanical surface modification process deep rolling is able to induce very high compressive residual stresses. A computational approach was developed to establish an appropriate residual stress depth profile matching the applied loads. Thus, the costs of manufacturing can be chosen in accordance to the required properties. The method to determine the residual stresses is based on an iterative reverse calculation of an existing bearing fatigue life model of Ioannides et al. The model originates from the approach of Lundberg and Palmgren (1947) including a stress fatigue limit tu. For the term ti, the fatigue criterion of Dang-Van is applied. The equation accounts for the maximum orthogonal shear stress and the local hydrostatic pressure phyd, corrected for residual and hoop stress. The inputs into the computational model are the stresses on the surface, which are simulated based on the load and geometry of the contact between roller and bearing surface. As an output the required residual stress profile underneath the bearings raceway is given to achieve a bearing fatigue life as required for the given application. In order to verify the model, the bearing fatigue life was experimentally determined for a given residual stress profile by experiments. <![CDATA[ <p>In drive systems and component technology a high reliability is very important for machines. Machine element dimensions are calculated for reliability. The properties for these elements are based on conventional manufacturing techniques. Very high stresses are applied on bearings in their operating time. To improve the endurance life, residual stresses can be induced into the subsurface zone. In contrast to a conventional grinding process, the mechanical surface modification process deep rolling is able to induce very high compressive residual stresses. A computational approach was developed to establish an appropriate residual stress depth profile matching the applied loads. Thus, the costs of manufacturing can be chosen in accordance to the required properties. The method to determine the residual stresses is based on an iterative reverse calculation of an existing bearing fatigue life model of Ioannides et al. The model originates from the approach of Lundberg and Palmgren (1947) including a stress fatigue limit tu. For the term ti, the fatigue criterion of Dang-Van is applied. The equation accounts for the maximum orthogonal shear stress and the local hydrostatic pressure phyd, corrected for residual and hoop stress. The inputs into the computational model are the stresses on the surface, which are simulated based on the load and geometry of the contact between roller and bearing surface. As an output the required residual stress profile underneath the bearings raceway is given to achieve a bearing fatigue life as required for the given application. In order to verify the model, the bearing fatigue life was experimentally determined for a given residual stress profile by experiments.</p> ]]> Computational Approach to Improve Bearings by Residual Stresses Based on Their Required Bearing Fatigue Life f. pape o. maiss b. denkena g. poll doi: 10.2495/CMEM-V6-N4-656-666 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 656 10.2495/CMEM-V6-N4-656-666 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-656-666 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-647-655 The properties of light alloy castings are strongly affected by their inclusion content, particularly double oxide film defects (bifilms), which not only decrease the tensile and fatigue properties, but also increase their scatter. Recent research has suggested that oxide film defects may alter with time, as the air inside the bifilm would react with the surrounding melt, while the hydrogen dissolved in the melt could diffuse into the bifilm cavity to form hydrogen porosity. The mechanical properties of the casting were shown to be significantly dependent upon the new morphology of its entrained bifilms. In this work, the Weibull moduli of the tensile properties of three Al castings, all expected to contain oxide films of, approximately, the same amount were compared. The first casting was poured into a resin-bonded sand mould while the second and third castings were poured into ceramic moulds with the mould for the third casting being preheated prior to pouring. The results of mechanical property analysis and electron microscopy examination suggested a considerable influence of the type of the mould and the solidification time on the morphology of bifilms and by implication, on the reliability and reproducibility of the tensile properties. <![CDATA[ <p>The properties of light alloy castings are strongly affected by their inclusion content, particularly double oxide film defects (bifilms), which not only decrease the tensile and fatigue properties, but also increase their scatter. Recent research has suggested that oxide film defects may alter with time, as the air inside the bifilm would react with the surrounding melt, while the hydrogen dissolved in the melt could diffuse into the bifilm cavity to form hydrogen porosity. The mechanical properties of the casting were shown to be significantly dependent upon the new morphology of its entrained bifilms. In this work, the Weibull moduli of the tensile properties of three Al castings, all expected to contain oxide films of, approximately, the same amount were compared. The first casting was poured into a resin-bonded sand mould while the second and third castings were poured into ceramic moulds with the mould for the third casting being preheated prior to pouring. The results of mechanical property analysis and electron microscopy examination suggested a considerable influence of the type of the mould and the solidification time on the morphology of bifilms and by implication, on the reliability and reproducibility of the tensile properties.</p> ]]> Effect of Mould Type and Solidification Time on Bifilm Defects and Mechanical Properties of Al–7SI–0.3MG Alloy Castings mahmoud ahmed el-sayed khamis essa doi: 10.2495/CMEM-V6-N4-647-655 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 647 10.2495/CMEM-V6-N4-647-655 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-647-655 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-635-646 Recent alloy developments have produced a new generation of Al–Li alloys that provide not only weight savings, but also many property benefits such as excellent corrosion resistance, good spectrum fatigue crack growth performance, a good strength and toughness combination and compatibility with standard manufacturing techniques. The forging of such alloys would lead to mechanical properties that closely match the aircraft engine requirements including lower weight, improved performance and a longer life. As a result, detailed analyses need to be performed to determine which material properties are best suited for a specific structure and how to achieve the required mechanical and damage tolerant properties during material processing.We developed an integrated physics-based model for prediction of microstructure evolution and material property prediction of third-generation Al–Li alloys. In order to develop such a model, an elastic-plastic crystal plasticity model is developed and incorporated in finite element software (ANSYS). The model accounts for microstructural evolution during non-isothermal, non-homogeneous deformation and is coupled with the damage kinetics. Our model bridges the gap between dislocation dynamics and continuum mechanics scales.Model parameters have been calibrated against lab tests including micropillar in-situ simple compression tests of Al–Li alloy 2070. Numerical predictions are verified against the lab results including stress–strain curves and crystallographic texture evolution. <![CDATA[ <p>Recent alloy developments have produced a new generation of Al–Li alloys that provide not only weight savings, but also many property benefits such as excellent corrosion resistance, good spectrum fatigue crack growth performance, a good strength and toughness combination and compatibility with standard manufacturing techniques. The forging of such alloys would lead to mechanical properties that closely match the aircraft engine requirements including lower weight, improved performance and a longer life. As a result, detailed analyses need to be performed to determine which material properties are best suited for a specific structure and how to achieve the required mechanical and damage tolerant properties during material processing.</p><p style="text-align: justify">We developed an integrated physics-based model for prediction of microstructure evolution and material property prediction of third-generation Al–Li alloys. In order to develop such a model, an elastic-plastic crystal plasticity model is developed and incorporated in finite element software (ANSYS). The model accounts for microstructural evolution during non-isothermal, non-homogeneous deformation and is coupled with the damage kinetics. Our model bridges the gap between dislocation dynamics and continuum mechanics scales.</p><p style="text-align: justify">Model parameters have been calibrated against lab tests including micropillar in-situ simple compression tests of Al–Li alloy 2070. Numerical predictions are verified against the lab results including stress–strain curves and crystallographic texture evolution.</p> ]]> An Elastic-Visco-Plastic Deformation Model of Al–Li with Application to Forging l.b. borkowski j.a. sharon a. staroselsky doi: 10.2495/CMEM-V6-N4-635-646 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 635 10.2495/CMEM-V6-N4-635-646 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-635-646 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-625-634 This paper focuses on combined experimental and numerical approaches to model thermal processes and obtain accurate results on system behaviour and performance. Interest lies in obtaining repeatable and dependable inputs for choosing appropriate conditions and parameters for enhancing the efficiency and the desired output. These results can also form the basis for system design and optimization. Several fundamental and practical problems are considered and typical results presented to discuss the implications and applications of this methodology. Circumstances where experimental data are used to validate the model, provide greater physical insight and define the boundary conditions, thus allowing the numerical simulation to be carried out, are also presented. Results from a concurrent, or parallel, simulation and experimentation approach are also presented to indicate the usefulness of such a strategy. It is stressed that experimental data are indispensable in obtaining accurate and realistic results for complex practical problems involving thermal transport processes. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper focuses on combined experimental and numerical approaches to model thermal processes and obtain accurate results on system behaviour and performance. Interest lies in obtaining repeatable and dependable inputs for choosing appropriate conditions and parameters for enhancing the efficiency and the desired output. These results can also form the basis for system design and optimization. Several fundamental and practical problems are considered and typical results presented to discuss the implications and applications of this methodology. Circumstances where experimental data are used to validate the model, provide greater physical insight and define the boundary conditions, thus allowing the numerical simulation to be carried out, are also presented. Results from a concurrent, or parallel, simulation and experimentation approach are also presented to indicate the usefulness of such a strategy. It is stressed that experimental data are indispensable in obtaining accurate and realistic results for complex practical problems involving thermal transport processes.</span></p> ]]> Combined Experimental and Numerical Approach to Model, Design and Optimize Thermal Processes yogesh jaluria doi: 10.2495/CMEM-V6-N4-625-634 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 4 Article 625 10.2495/CMEM-V6-N4-625-634 https://www.acadlore.com/article/IJCMEM/2018_6_4/CMEM-V6-N4-625-634 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-iii The contents of this issue reflect the rapid advances that have taken place in materials science and engineering, prompted by the demand for high quality performance materials by industry.The contributions represent some of the latest developments in the field of Materials Characterisation, describing procedures for the assessment of physical and chemical properties of materials by experimental and computational methods. Apart from microstructural and macro-mechanical investigations on metallic substances, extensive coverage is also given to composites, biomaterials, polymers, ceramics and cementitious materials as well as to the effectiveness of various surface treatments. The wide range of topics includes interaction between disciplines, which is sometimes essential to achieving a proper understanding of material behaviour.All issues, including this one, have been published in paper as well as digital format and are being widely distributed throughout the worldThe EditorsTallinn, Estonia2017 <![CDATA[ <p>The contents of this issue reflect the rapid advances that have taken place in materials science and engineering, prompted by the demand for high quality performance materials by industry.</p><p style="text-align: justify">The contributions represent some of the latest developments in the field of Materials Characterisation, describing procedures for the assessment of physical and chemical properties of materials by experimental and computational methods. Apart from microstructural and macro-mechanical investigations on metallic substances, extensive coverage is also given to composites, biomaterials, polymers, ceramics and cementitious materials as well as to the effectiveness of various surface treatments. The wide range of topics includes interaction between disciplines, which is sometimes essential to achieving a proper understanding of material behaviour.</p><p style="text-align: justify">All issues, including this one, have been published in paper as well as digital format and are being widely distributed throughout the world</p><p style="text-align: justify">The Editors</p><p style="text-align: justify">Tallinn, Estonia</p><p style="text-align: justify">2017</p> ]]> Preface doi: 10.2495/CMEM-V6-N3-iii International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 0 10.2495/CMEM-V6-N3-iii https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-iii https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-605-613 Load capacities of pad eyes used in offshore lifting operations are generally determined based on the guidelines given in lifting standards. In 2012, NORSOK issued a new standard, R-002 ‘Lifting equipment’, to ensure that adequate safety requirements are complied with in connection with lifting operations on the Norwegian continental shelf. To ensure the accuracy of the followed design procedure, this paper presents a comparison of theoretical load capacities of 3.25-ton pad eyes with experimentally and numerically predicted load capacities. Several laboratory tests have been performed to conduct experimental analyses of the load capacities of pad eyes. These tests have included different pinhole sizes in the pad eyes, different strain directions of pad eye pinholes and different loads to which the pad eyes were subjected. Finite element (FE) simulation was performed for two different cases: with base plate and without base plates. The obtained numerical results show that the addition of the plate to the pad eyes increased the capacity of the pad eyes. It also shows that load capacity of the pad eyes gradually decreased with the increase in pinhole size. This shows the importance of following the standard’s requirements. The comparison of results shows that some of the load capacities provided by the FE analysis closer to the experimental and the theoretical results, while a few others were quite far from them. These differences have been comprehensively discussed in the latter part of the paper. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Load capacities of pad eyes used in offshore lifting operations are generally determined based on the guidelines given in lifting standards. In 2012, NORSOK issued a new standard, R-002 ‘Lifting equipment’, to ensure that adequate safety requirements are complied with in connection with lifting operations on the Norwegian continental shelf. To ensure the accuracy of the followed design procedure, this paper presents a comparison of theoretical load capacities of 3.25-ton pad eyes with experimentally and numerically predicted load capacities. Several laboratory tests have been performed to conduct experimental analyses of the load capacities of pad eyes. These tests have included different pinhole sizes in the pad eyes, different strain directions of pad eye pinholes and different loads to which the pad eyes were subjected. Finite element (FE) simulation was performed for two different cases: with base plate and without base plates. The obtained numerical results show that the addition of the plate to the pad eyes increased the capacity of the pad eyes. It also shows that load capacity of the pad eyes gradually decreased with the increase in pinhole size. This shows the importance of following the standard’s requirements. The comparison of results shows that some of the load capacities provided by the FE analysis closer to the experimental and the theoretical results, while a few others were quite far from them. These differences have been comprehensively discussed in the latter part of the paper.</span></p> ]]> Ultimate Capacity of Pad Eyes Used for Lifting Operations: Experimental and Numerical Simulations hikmat saaid saleh samdar kakay sudath c. siriwardane doi: 10.2495/CMEM-V6-N3-605-613 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 605 10.2495/CMEM-V6-N3-605-613 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-605-613 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-594-604 In response to the nano-scale miniaturization trend of IC devices, advanced semiconductor processes require more stringent cleanliness. This study sets up a UHV measurement system for particles detection within a highly cleanliness testing chamber with a UHV slit valve to be test, and an experimental procedure is proposed and examined to investigate particle generation while this slit valve is in operations. Cycle numbers of 10,000, 20,000 and 40,000, respectively, are set for slit valve testing. A series of experiments are conducted to gather particles generation information and to clarify the possible causes and sources of dust particles and its concentrations and the particle sizes. The condensation particle counter (CPC) is used to measure the particle concentration and the differential mobility analyzer (DMA) is for particle sizes measurement. Besides, scanning electron microscopy (SEM) and atomic force microscope (AFM) are used to investigate the condensation behaviors on a witness wafer and the energy dispersive x-ray spectroscopy (EDS) is used to the surface characterizations of the slit valve O-ring. In atmosphere experiments, the particle sizes and size distributions are measured by CPC and SMPS instruments and the gathered results are compared to the measured particle sizes by SEM and AFM and are used to evaluate the assumptions of particle generating sources and mechanisms. Experimental results show that the particle sizes and particle concentrations increase as the cycle numbers increases. To examine the particle generations in vacuum, the particle sizes of the deposited particles on wafer are measured by SEM and AFM. The results are compared with the SMPS measurement. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In response to the nano-scale miniaturization trend of IC devices, advanced semiconductor processes require more stringent cleanliness. This study sets up a UHV measurement system for particles detection within a highly cleanliness testing chamber with a UHV slit valve to be test, and an experimental procedure is proposed and examined to investigate particle generation while this slit valve is in operations. Cycle numbers of 10,000, 20,000 and 40,000, respectively, are set for slit valve testing. A series of experiments are conducted to gather particles generation information and to clarify the possible causes and sources of dust particles and its concentrations and the particle sizes. The condensation particle counter (CPC) is used to measure the particle concentration and the differential mobility analyzer (DMA) is for particle sizes measurement. Besides, scanning electron microscopy (SEM) and atomic force microscope (AFM) are used to investigate the condensation behaviors on a witness wafer and the energy dispersive x-ray spectroscopy (EDS) is used to the surface characterizations of the slit valve O-ring. In atmosphere experiments, the particle sizes and size distributions are measured by CPC and SMPS instruments and the gathered results are compared to the measured particle sizes by SEM and AFM and are used to evaluate the assumptions of particle generating sources and mechanisms. Experimental results show that the particle sizes and particle concentrations increase as the cycle numbers increases. To examine the particle generations in vacuum, the particle sizes of the deposited particles on wafer are measured by SEM and AFM. The results are compared with the SMPS measurement.</span></p> ]]> Study of Nano/Micro Aerosol Particles Measurement for the UHV Slit Valves rong-yuan jou jian-jia qiu che-chin chen james su ming-hua shiao doi: 10.2495/CMEM-V6-N3-594-604 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 594 10.2495/CMEM-V6-N3-594-604 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-594-604 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-584-593 A new cement-based material is presented in this research contribution. The material consists in a fibre-reinforced self-compacting concrete with 100% of mixed recycled aggregate. Six different mixes were produced in two different conditions: (1) in a concrete plant in order to verify the adaptability of the existing equipment to produce and pour this material under real boundary conditions and (2) in laboratory controlled conditions. A physical (density, porosity, fibre distribution and orientation) and mechanical (compressive, tensile and post-cracking strengths, Young modulus) characterization involving 1,100 specimens was carried out. The results obtained permit to conclude that compressive concrete strength superior to 30 MPa can be achieved with certain ductility and tenacity. In based of these results, this material could be used in applications like foundations, ground-supported slabs, retaining systems and other elements with moderate structural responsibility. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A new cement-based material is presented in this research contribution. The material consists in a fibre-reinforced self-compacting concrete with 100% of mixed recycled aggregate. Six different mixes were produced in two different conditions: (1) in a concrete plant in order to verify the adaptability of the existing equipment to produce and pour this material under real boundary conditions and (2) in laboratory controlled conditions. A physical (density, porosity, fibre distribution and orientation) and mechanical (compressive, tensile and post-cracking strengths, Young modulus) characterization involving 1,100 specimens was carried out. The results obtained permit to conclude that compressive concrete strength superior to 30 MPa can be achieved with certain ductility and tenacity. In based of these results, this material could be used in applications like foundations, ground-supported slabs, retaining systems and other elements with moderate structural responsibility.</span></p> ]]> Characterization of a Fibre-Reinforced Self- Compacting Concrete with 100% of Mixed Recycled Aggregates jose a. ortiz-lozano albert de la fuente-antequera ignacio segura-pérez antonio aguado de cea ana c. parapinski dos santos jesus pacheco-martinez juan j. soto-bernal doi: 10.2495/CMEM-V6-N3-584-593 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 584 10.2495/CMEM-V6-N3-584-593 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-584-593 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-571-583 Isotropic materials have the same properties in all directions of space, with the same magnitude. Strict isotropy requires a spherical symmetry, hence a cubic unit-cell. All other crystal systems give rise to property anisotropy, i.e. direction dependence of properties and of their magnitude, although the anisotropy may often be weak enough to be quite insignificant. However, some materials show very strong anisotropy, owing to their layered structure, which is the result of unequal bond strength versus direction in space. Property anisotropy is usually the consequence of bonding anisotropy that gives anisotropic crystal growth, i.e. the crystals grow faster in some directions and slower in others, resulting in a crystallite shape that is often sheet-like (two-dimensional) or needle-like (one-dimensional). Many tin(II)-containing materials are found to have very strong low dimensionality: (1) SnF2/MCl (M = alkali metals and NH4) give needle shaped crystals even long hair-shaped. For example, in M3Sn5Cl3F10, the intersection of planes of lone pairs creates cleavage planes in two directions, giving needle shaped crystals. Extreme cases of two-dimensionality were observed in MSnF4, particularly in α-PbSnF4. Bonding anisotropy in tin(II)-containing materials is due to the tin stereoactive lone pair, when the lone pairs cluster in sheets, since no bonding to tin can take place in the lone pair direction. This gives rise to high preferred orientation of polycrystalline samples. The presentation will show how the anisotropy of the tin(II) quadrupole doublet, measured on polycrystalline samples subjected to an extremely enhanced preferred orientation, can be used to predict the direction of the lone pairs in the unit-cell and this, in turn, explain the direction of the cleavage planes. The presentation will focus on the use of X-ray diffraction and Mössbauer spectroscopy to characterize highly anisotropic phases and understand their structure-textural properties. <![CDATA[ <p><em>Isotropic </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">materials have the same properties in all directions of space, with the same magnitude. Strict isotropy requires a spherical symmetry, hence a cubic unit-cell. All other crystal systems give rise to property </span><em>anisotropy</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">, i.e. direction dependence of properties and of their magnitude, although the anisotropy may often be weak enough to be quite insignificant. However, some materials show very strong anisotropy, owing to their layered structure, which is the result of unequal bond strength versus direction in space. Property anisotropy is usually the consequence of bonding anisotropy that gives anisotropic crystal growth, i.e. the crystals grow faster in some directions and slower in others, resulting in a crystallite shape that is often sheet-like (two-dimensional) or needle-like (one-dimensional). Many tin(II)-containing materials are found to have very strong low dimensionality: (1) SnF2/MCl (M = alkali metals and NH4) give needle shaped crystals even long hair-shaped. For example, in M3Sn5Cl3F10, the intersection of planes of lone pairs creates cleavage planes in two directions, giving needle shaped crystals. Extreme cases of two-dimensionality were observed in MSnF4, particularly in </span><em>α</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">-PbSnF4. Bonding anisotropy in tin(II)-containing materials is due to the tin stereoactive lone pair, when the lone pairs cluster in sheets, since no bonding to tin can take place in the lone pair direction. This gives rise to high preferred orientation of polycrystalline samples. The presentation will show how the anisotropy of the tin(II) quadrupole doublet, measured on polycrystalline samples subjected to an extremely enhanced preferred orientation, can be used to predict the direction of the lone pairs in the unit-cell and this, in turn, explain the direction of the cleavage planes. The presentation will focus on the use of X-ray diffraction and Mössbauer spectroscopy to characterize highly anisotropic phases and understand their structure-textural properties.</span></p> ]]> Low Dimensionality Materials: Origin of the Reduced Dimensonality in Tin(II) Fluoride- Containing Compounds and Its Study by X-Ray Diffraction and Mössbauer Spectroscopy georges dénès m. cecilia madamba hocine merazig abdualhafed muntasar doi: 10.2495/CMEM-V6-N3-571-583 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 571 10.2495/CMEM-V6-N3-571-583 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-571-583 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-563-570 The use of the lignin–corundum hybrid fillers for phenolic resins was showed. The very important aspect of the use of lignin for phenolic resin composites is the reduction of phenol emission. The emission of phenol from the phenolic resin-hybrid filler composites were studied by headspace analysis. The physicochemical properties of the new hybrid fillers as well as the thermomechanical properties of the composites with them were examined. The surface properties of hybrid fillers were studied by inverse gas chromatography (IGC). The chemical structure of the new fillers was tested by Fourier transform infrared spectroscopy (FTIR). The dynamic mechanical thermal analysis (DMTA) was used to test the thermomechanical properties of the model composites for the use of abrasive tool production. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The use of the lignin–corundum hybrid fillers for phenolic resins was showed. The very important aspect of the use of lignin for phenolic resin composites is the reduction of phenol emission. The emission of phenol from the phenolic resin-hybrid filler composites were studied by headspace analysis. The physicochemical properties of the new hybrid fillers as well as the thermomechanical properties of the composites with them were examined. The surface properties of hybrid fillers were studied by inverse gas chromatography (IGC). The chemical structure of the new fillers was tested by Fourier transform infrared spectroscopy (FTIR). The dynamic mechanical thermal analysis (DMTA) was used to test the thermomechanical properties of the model composites for the use of abrasive tool production.</span></p> ]]> New Ecological Composites Based on Natural Renewable Resources strzemiecka łukasz klapiszewski artur jamrozik teofil jesionowski adam voelkel doi: 10.2495/CMEM-V6-N3-563-570 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 563 10.2495/CMEM-V6-N3-563-570 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-563-570 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-551-562 Four-point bending is a standard test method that can be used to determine flexural properties of a material or for quality control. The ASTM and ISO test standards specify an allowable range of set-up parameters such as the coupon width, the support span and the load span that can be used to determine the flexural modulus. When angle-ply laminates are tested in four-point bending the apparent flexural modulus is over predicted due to the bending-twisting coupling and the interaction between the coupon and the test fixture. In the present study, the effect of the test configuration on the apparent flexural modulus of thin angle-ply laminates in four-point bending is evaluated for six different layups. It is shown that test set-ups that allow more twisting of the coupon will result in apparent flexural moduli that are closer to the theoretical value. The torsional moments induced by the test fixture are quantified, and it is shown that they are directly responsible for the increase in the apparent flexural modulus. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Four-point bending is a standard test method that can be used to determine flexural properties of a material or for quality control. The ASTM and ISO test standards specify an allowable range of set-up parameters such as the coupon width, the support span and the load span that can be used to determine the flexural modulus. When angle-ply laminates are tested in four-point bending the apparent flexural modulus is over predicted due to the bending-twisting coupling and the interaction between the coupon and the test fixture. In the present study, the effect of the test configuration on the apparent flexural modulus of thin angle-ply laminates in four-point bending is evaluated for six different layups. It is shown that test set-ups that allow more twisting of the coupon will result in apparent flexural moduli that are closer to the theoretical value. The torsional moments induced by the test fixture are quantified, and it is shown that they are directly responsible for the increase in the apparent flexural modulus.</span></p> ]]> The Effects of Test Set-up on the Apparent Flexural Modulus of Thin Angle-Ply Laminates Using Standard Four-Point Bend Testing doi: 10.2495/CMEM-V6-N3-551-562 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 551 10.2495/CMEM-V6-N3-551-562 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-551-562 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-540-550 A graded high-vanadium alloy composite coating was synthesized from premixed powders (V, Cr, Ti, Mo, Nb) on ductile iron (DI) substrate via atmospheric plasma arc surface alloying process. The resulted cross-section microstructure is divided into three distinct zones: upper alloyed zone (AZ) rich with spherical primary carbides, middle melted zone (MZ) with fine white iron structure and lower heat affected zone (HAZ). Spherical or bulk-like primary carbides with diameter <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A graded high-vanadium alloy composite coating was synthesized from premixed powders (V, Cr, Ti, Mo, Nb) on ductile iron (DI) substrate via atmospheric plasma arc surface alloying process. The resulted cross-section microstructure is divided into three distinct zones: upper alloyed zone (AZ) rich with spherical primary carbides, middle melted zone (MZ) with fine white iron structure and lower heat affected zone (HAZ). Spherical or bulk-like primary carbides with diameter < 1 μm in the AZ are formed via in-situ reactions between alloy powders and graphite in DI. Microstructural characterizations indicate that the carbides are primarily MC-type (M=V, Ti, Nb) carbides combined with mixed hardphases such as M2C, M7C3, M23C6, and martensite. Disperse distribution of spherical, submicron-sized metal carbides in an austenite/ledeburite matrix render the graded coating hard-yet-tough. The maximum microhardness of the upper alloyed zone is 950 HV0.2, which is five times that of the substrate. Significant plastic deformation with no cracking in the micro-indentations points to a high toughness. The graded high-vanadium alloy composite coating exhibits superior tribological performance in comparison to Mn13 steel and plasma transferred arc remelted DI.</span></p> ]]> Hard-Yet-Tough High-Vanadium High-Speed Steel Composite Coating in-Situ Alloyed on Ductile Iron by Atmospheric Plasma ARC huatang cao xuanpu dong yutao pei doi: 10.2495/CMEM-V6-N3-540-550 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 540 10.2495/CMEM-V6-N3-540-550 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-540-550 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-527-539 An improved elasto-plastic characterisation technique relying on instrumented indentation data, accounting for frame compliance, spherical indenter imperfections and, most importantly, material pile-up at indentation edges was validated on experimental data from control specimens with known properties. The method was subsequently applied to the characterisation of weld regions for which traditional testing methods are not applicable. Variations of elasto-plastic properties were obtained from indentations on a butt-welded steel specimen spanning the three distinct weld regions. The consistency of these results and their sensitivity to variations of experimental data was examined and discussed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">An improved elasto-plastic characterisation technique relying on instrumented indentation data, accounting for frame compliance, spherical indenter imperfections and, most importantly, material pile-up at indentation edges was validated on experimental data from control specimens with known properties. The method was subsequently applied to the characterisation of weld regions for which traditional testing methods are not applicable. Variations of elasto-plastic properties were obtained from indentations on a butt-welded steel specimen spanning the three distinct weld regions. The consistency of these results and their sensitivity to variations of experimental data was examined and discussed.</span></p> ]]> Weld Zone Material Characterisation Based on Spherical Indentation Data s. syngellakis h. habbab b.g. mellor doi: 10.2495/CMEM-V6-N3-527-539 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 527 10.2495/CMEM-V6-N3-527-539 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-527-539 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-515-526 Strain rate effect of strength is a crucial factor for material characterization. Attempts have been made to evaluate strain rate effect by indentation tests. An indentation causes a non-uniform stress and strain field inside a specimen. This must induce a non-uniform strain rate field. However, little has been reported about strain rate distribution beneath the indenter. So far, various indenter control methods have been used. In previous studies, no direct comparisons were available as to how strain rate distribution was affected by different control methods. In this study, we report on the strain rate effect of indentation with two indenter control methods: constant loading rate (CLR) and constant indentation strain rate (CISR). The finite element method was designed to reproduce deformation caused by a conical indenter of a half apex angle of 70.3°. Pure aluminum (99.999 mass% purity), which showed high strain rate dependence of strength, was chosen as a specimen. Material properties were obtained from low strain rate (10–4, 10–2/s) to high strain rate (102/s) tests, and results were incorporated into a FEM analysis using the Cowper-Symonds equation. Four constant loading rates (from 0.7 to 350 mN/s) and constant indentation strain rates (from 0.006 to 6/s) were used, and both results were compared. Differences between both indenter control methods were displacement-dependent. Loading curvature, which has been defined as a material constant in the indentation, was calculated from load divided by square of displacement. Although loading curvatures were decreased with increasing displacement for CLR, they were constant for CISR. Results also showed that values of strain rate decreased as displacement increased for CLR, whereas they were the same for CISR. Similarities of both indenter control methods were found as follows. The highest strain rate regions were observed at the edge of the indenter. In addition, higher strain rate region was distributed hemispherically from the edge of the indenter. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Strain rate effect of strength is a crucial factor for material characterization. Attempts have been made to evaluate strain rate effect by indentation tests. An indentation causes a non-uniform stress and strain field inside a specimen. This must induce a non-uniform strain rate field. However, little has been reported about strain rate distribution beneath the indenter. So far, various indenter control methods have been used. In previous studies, no direct comparisons were available as to how strain rate distribution was affected by different control methods. In this study, we report on the strain rate effect of indentation with two indenter control methods: constant loading rate (CLR) and constant indentation strain rate (CISR). The finite element method was designed to reproduce deformation caused by a conical indenter of a half apex angle of 70.3°. Pure aluminum (99.999 mass% purity), which showed high strain rate dependence of strength, was chosen as a specimen. Material properties were obtained from low strain rate (10–4, 10–2/s) to high strain rate (102/s) tests, and results were incorporated into a FEM analysis using the Cowper-Symonds equation. Four constant loading rates (from 0.7 to 350 mN/s) and constant indentation strain rates (from 0.006 to 6/s) were used, and both results were compared. Differences between both indenter control methods were displacement-dependent. Loading curvature, which has been defined as a material constant in the indentation, was calculated from load divided by square of displacement. Although loading curvatures were decreased with increasing displacement for CLR, they were constant for CISR. Results also showed that values of strain rate decreased as displacement increased for CLR, whereas they were the same for CISR. Similarities of both indenter control methods were found as follows. The highest strain rate regions were observed at the edge of the indenter. In addition, higher strain rate region was distributed hemispherically from the edge of the indenter.</span></p> ]]> Strain Rate Behavior of Pure Aluminum in Conical Indentation with Different Indenter Control Methods tsuyoshi kami hiroyuki yamada nagahisa ogasawara xi chen doi: 10.2495/CMEM-V6-N3-515-526 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 515 10.2495/CMEM-V6-N3-515-526 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-515-526 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-499-514 Corrosion causes damage to reinforcing steel in concrete structures and governs the service life of the structures. Currently, researchers are paying attention to modelling the behaviour of the bond between the concrete and steel interface of corroded reinforcement. The main objective of this paper is to study the recent research relevant to the bond behaviour at the interface between corroded ribbed bars and concrete and to identify the future research focus. Initially, the paper presents the mechanisms of corrosion damage of reinforced concrete by discussing corrosive agents, causes and effects. Then mechanisms of corrosion prorogation, mechanical properties of corroded reinforcing steel and effects of corrosion on bond degradation of reinforced concrete are discussed in details. Thereafter, recent experimental researches on bond degradation between reinforcement and concrete are reviewed. Previous studies have proposed formulae, which depend on cover, reinforcing bar diameter, concrete strength and corrosion level, to predict the ultimate bond strength. Effect of other parameters (i.e. type of the bars, bar spacing, crack size, aggregate size, type of loading, stress state and etc.) on bond strength have not been properly studied in literature. Bond strength against biaxial bending or combined load action has not been investigated. Finally, the paper concludes with the significance of testing naturally corroded test specimens, compared to the artificially corroded specimens, as well as discussing loading situations. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Corrosion causes damage to reinforcing steel in concrete structures and governs the service life of the structures. Currently, researchers are paying attention to modelling the behaviour of the bond between the concrete and steel interface of corroded reinforcement. The main objective of this paper is to study the recent research relevant to the bond behaviour at the interface between corroded ribbed bars and concrete and to identify the future research focus. Initially, the paper presents the mechanisms of corrosion damage of reinforced concrete by discussing corrosive agents, causes and effects. Then mechanisms of corrosion prorogation, mechanical properties of corroded reinforcing steel and effects of corrosion on bond degradation of reinforced concrete are discussed in details. Thereafter, recent experimental researches on bond degradation between reinforcement and concrete are reviewed. Previous studies have proposed formulae, which depend on cover, reinforcing bar diameter, concrete strength and corrosion level, to predict the ultimate bond strength. Effect of other parameters (i.e. type of the bars, bar spacing, crack size, aggregate size, type of loading, stress state and etc.) on bond strength have not been properly studied in literature. Bond strength against biaxial bending or combined load action has not been investigated. Finally, the paper concludes with the significance of testing naturally corroded test specimens, compared to the artificially corroded specimens, as well as discussing loading situations.</span></p> ]]> Corrosion Propagation Phase and Bond Strength Degradation of Reinforced Concrete Structures: State of the Art nirosha d. adasooriya samindi samarakoon ove tobias gudmestad doi: 10.2495/CMEM-V6-N3-499-514 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 499 10.2495/CMEM-V6-N3-499-514 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-499-514 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-487-498 This research presents analytical and mathematical modelling of coating failures within industrial components, structures, mobile assets and systems due to corrosive degradation and mechanical fracture. These failures lead to several surface problems; therefore, contact mechanics and electrochemistry approaches incorporating induced residual stresses have been adopted to develop a comprehensive solution for the prediction and prognostic of such failures. Experimental study of film cracking and its propagation into substrates, interfacial transient behaviours and film-substrate system has been conducted. A parallel study of corrosive degradation to include cathodic delamination, cathodic blistering and tribo-corrosion of films has been conducted. Experimental and analytical studies of induced residual stresses within the coating and their effects on failure mechanisms and propagation have been completed. A detailed investigation of elastic mismatch at the interfacial contact and interfacial crack tip field has been performed and a complex stress intensity factor is presented. Mathematical derivation of oscillatory singularity, mode mix and interfacial fracture criterion to include adhesion are presented. This paper presents novel mathematical modelling incorporating interfacial crack propagating, diffusion of corrosive species and cathodic blistering for prediction and prognoses of coating failures. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This research presents analytical and mathematical modelling of coating failures within industrial components, structures, mobile assets and systems due to corrosive degradation and mechanical fracture. These failures lead to several surface problems; therefore, contact mechanics and electrochemistry approaches incorporating induced residual stresses have been adopted to develop a comprehensive solution for the prediction and prognostic of such failures. Experimental study of film cracking and its propagation into substrates, interfacial transient behaviours and film-substrate system has been conducted. A parallel study of corrosive degradation to include cathodic delamination, cathodic blistering and tribo-corrosion of films has been conducted. Experimental and analytical studies of induced residual stresses within the coating and their effects on failure mechanisms and propagation have been completed. A detailed investigation of elastic mismatch at the interfacial contact and interfacial crack tip field has been performed and a complex stress intensity factor is presented. Mathematical derivation of oscillatory singularity, mode mix and interfacial fracture criterion to include adhesion are presented. This paper presents novel mathematical modelling incorporating interfacial crack propagating, diffusion of corrosive species and cathodic blistering for prediction and prognoses of coating failures.</span></p> ]]> Predictive and Prognostic Modelling and Simulation of Coatings Subject to Corrosion and Mechanical Failures zulfiqar ahmad khan jawwad latif hammad nazir adil saeed keith stokes doi: 10.2495/CMEM-V6-N3-487-498 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 487 10.2495/CMEM-V6-N3-487-498 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-487-498 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-476-486 A dynamic indentation experiment is presented for assessment of the adhesive behavior of a range of coatings in erosive defouling of commercial aircraft engines using CO$_2$ dry-ice. A series of experiments is presented in which particles made from a reference material (polyoxymethylene—POM) and from CO$_2$ dry-ice are made to impact compressor airfoils under a range of impact angle and velocity conditions. The airfoils investigated are coated with an indicator material (PTFE), which is typically used to visualise the defouling effect in large scale compressor defouling experiments. In addition, fouled compressor airfoils taken from service and coated with a fouling typically found in low-pressure compressor stages are investigated. The energy required for the reference particles (POM) to create a defouling effect for the different coatings is determined by an experimental evaluation of their coefficient of restitution. This energy requirement is assumed to be fouling specific. Empirical defouling functions are presented. They correlate the defouling effect for both particle materials under various impact conditions. The empirical correlations are developed into a simulation procedure to predict particle impact erosion and energy dissipation of coated surfaces in numerical indentation simulations. <![CDATA[ <p>A dynamic indentation experiment is presented for assessment of the adhesive behavior of a range of coatings in erosive defouling of commercial aircraft engines using CO$_2$ dry-ice. A series of experiments is presented in which particles made from a reference material (polyoxymethylene<span style="color: rgb(0, 0, 0); font-family: Times New Roman, sans-serif">—</span>POM) and from CO$_2$ dry-ice are made to impact compressor airfoils under a range of impact angle and velocity conditions. The airfoils investigated are coated with an indicator material (PTFE), which is typically used to visualise the defouling effect in large scale compressor defouling experiments. In addition, fouled compressor airfoils taken from service and coated with a fouling typically found in low-pressure compressor stages are investigated. The energy required for the reference particles (POM) to create a defouling effect for the different coatings is determined by an experimental evaluation of their coefficient of restitution. This energy requirement is assumed to be fouling specific. Empirical defouling functions are presented. They correlate the defouling effect for both particle materials under various impact conditions. The empirical correlations are developed into a simulation procedure to predict particle impact erosion and energy dissipation of coated surfaces in numerical indentation simulations.</p> ]]> An Energy-Based Approach to Assess and Predict Erosive Airfoil Defouling arthur rudek thomas-alexander zitzmann gerald russ barry duignan doi: 10.2495/CMEM-V6-N3-476-486 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 476 10.2495/CMEM-V6-N3-476-486 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-476-486 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-463-475 High-speed impacts such as ballistic and hurricane debris can cause severe damages due to the high kinetic energies in the impacting objects. A good understanding of the mechanism of high-speed impacts can help develop impact-resistant or protective systems. Experimental studies of high-speed impact problem, though valid and useful, are often limited and challenged by the large, nonlinear deformations and contacts involved in such problems. To this end, physical experiments are best used as a validation tool rather than an exploration tool for new system designs. In this study, nonlinear finite element simulations are performed to evaluate the response of metallic materials (e.g. steels) and non-metallic materials (e.g. woven fabrics) under high-speed impacts. In addition, the effects of layered structures of different types of materials as well as layer configurations are investigated. <![CDATA[ <p>High-speed impacts such as ballistic and hurricane debris can cause severe damages due to the high kinetic energies in the impacting objects. A good understanding of the mechanism of high-speed impacts can help develop impact-resistant or protective systems. Experimental studies of high-speed impact problem, though valid and useful, are often limited and challenged by the large, nonlinear deformations and contacts involved in such problems. To this end, physical experiments are best used as a validation tool rather than an exploration tool for new system designs. In this study, nonlinear finite element simulations are performed to evaluate the response of metallic materials (e.g. steels) and non-metallic materials (e.g. woven fabrics) under high-speed impacts. In addition, the effects of layered structures of different types of materials as well as layer configurations are investigated.</p> ]]> Numerical Simulation of High-Speed Impacts Involving Metallic and Non-Metallic Materials howie fang emre palta matthew gutowski doi: 10.2495/CMEM-V6-N3-463-475 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 463 10.2495/CMEM-V6-N3-463-475 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-463-475 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-455-462 An unalloyed ductile iron, which incorporates C and Si as major and Mn as minor alloying elements, is processed by a novel austempering process, in order to obtain superior mechanical properties. The samples are initially austenitized at 890°C for 20 min, then quenched into patented water-based quenching liquid at 180°C for 0.5, 2 and 3.5 s respectively, and austempered at 220°C for 240 min in an electric furnace. Optical microscopy (OM) and scanning electron microscopy (SEM) are performed to correlate the mechanical properties with microstructural characteristics. It is found that partial martensite can be formed firstly upon quenching, which will accelerate the subsequent bainitic transformation and promote refinement of multiphase colonies during austempering. The prior martensite content increases with increasing holding time during quenching. A tensile strength of 1330MPa, an elongation of 3.13% and a hardness of 45HRC can be achieved by controlling the prior martensite content to 12%. SEM of fracture surfaces reveals a mixed ductile and cleavage rupture morphology type in all samples. The results indicate that the tensile behavior of the investigated ADI is mainly influenced by the content of prior martensite. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">An unalloyed ductile iron, which incorporates C and Si as major and Mn as minor alloying elements, is processed by a novel austempering process, in order to obtain superior mechanical properties. The samples are initially austenitized at 890°C for 20 min, then quenched into patented water-based quenching liquid at 180°C for 0.5, 2 and 3.5 s respectively, and austempered at 220°C for 240 min in an electric furnace. Optical microscopy (OM) and scanning electron microscopy (SEM) are performed to correlate the mechanical properties with microstructural characteristics. It is found that partial martensite can be formed firstly upon quenching, which will accelerate the subsequent bainitic transformation and promote refinement of multiphase colonies during austempering. The prior martensite content increases with increasing holding time during quenching. A tensile strength of 1330MPa, an elongation of 3.13% and a hardness of 45HRC can be achieved by controlling the prior martensite content to 12%. SEM of fracture surfaces reveals a mixed ductile and cleavage rupture morphology type in all samples. The results indicate that the tensile behavior of the investigated ADI is mainly influenced by the content of prior martensite.</span></p> ]]> Effect of Prior Martensite on Mechanical Properties of Austempered Ductile Iron chen yang derek o. northwood cheng liu doi: 10.2495/CMEM-V6-N3-455-462 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 3 Article 455 10.2495/CMEM-V6-N3-455-462 https://www.acadlore.com/article/IJCMEM/2018_6_3/CMEM-V6-N3-455-462 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-433-445 Fine-grained sediment in Florida’s eutrophic lakes displays a characteristically multiphase and layered structure including fluid mud that accounts for most of the nutrient-rich suspended matter potentially contributing to water quality degradation. The viscometric properties of fluid mud layer are particularly important for calculating the sediment load and rate of accumulation. Following a description of fine-sediment layering, a method is outlined to determine the yield stress and viscosity of the characteristically viscoplastic fluid mud. Based upon previous analytic work, these two quantities are deduced from the flow curves for sediment samples (with a mean organic content of about 63%) collected by coring at four sites in Lake Apopka. The analysis indicates an increase in the yield stress and decrease in the relative viscosity with increasing floc volume fraction. Inherent in these trends is the influence of organic content that increases with the floc volume fraction. Comparison with flow curves for sediment of higher density, greater cohesion and lower organic content from a bayou in Louisiana reveals three orders of magnitude higher yield stresses and somewhat lower viscosities relative to Apopka. High yield stresses in the bayou are associated with a dense bed subject to tidal current, which possibly prevents the retention of weak sediment at the bottom. Calculation of the sediment load and annual rate of accumulation due to a fluid mud undercurrent is illustrated for viscous flow over a mildly sloping bottom. For a realistic assessment of the accumulation it will be essential to take into account the role of the episodic wind field and the turbulent flow driving the suspended matter in the lake. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Fine-grained sediment in Florida’s eutrophic lakes displays a characteristically multiphase and layered structure including fluid mud that accounts for most of the nutrient-rich suspended matter potentially contributing to water quality degradation. The viscometric properties of fluid mud layer are particularly important for calculating the sediment load and rate of accumulation. Following a description of fine-sediment layering, a method is outlined to determine the yield stress and viscosity of the characteristically viscoplastic fluid mud. Based upon previous analytic work, these two quantities are deduced from the flow curves for sediment samples (with a mean organic content of about 63%) collected by coring at four sites in Lake Apopka. The analysis indicates an increase in the yield stress and decrease in the relative viscosity with increasing floc volume fraction. Inherent in these trends is the influence of organic content that increases with the floc volume fraction. Comparison with flow curves for sediment of higher density, greater cohesion and lower organic content from a bayou in Louisiana reveals three orders of magnitude higher yield stresses and somewhat lower viscosities relative to Apopka. High yield stresses in the bayou are associated with a dense bed subject to tidal current, which possibly prevents the retention of weak sediment at the bottom. Calculation of the sediment load and annual rate of accumulation due to a fluid mud undercurrent is illustrated for viscous flow over a mildly sloping bottom. For a realistic assessment of the accumulation it will be essential to take into account the role of the episodic wind field and the turbulent flow driving the suspended matter in the lake.</span></p> ]]> Multiphase Layering and Mobility of Suspended Fine Sediment in Lake Apopka, Florida ashish j. mehta john m. jaeger ziynet boz yogesh p. khare doi: 10.2495/CMEM-V6-N2-433-445 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 433 10.2495/CMEM-V6-N2-433-445 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-433-445 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-423-432 The impingement and evaporation processes of droplet widely exist in many industrial fields such as fuel injection in combustion engines, spray drying and turbines. When a single droplet falls and impacts on an inclined hot surface under the effect of gravity, it evaporates after contacting with the surface due to the heated transfer. The inclined angle of surfaces has great effects on droplet dynamics and heat transfer. In this work, the pseudo-potential model and a thermal lattice Boltzmann model are combined to simulate the impact process and the heat transfer. Moreover, the Peng-Robinson equation of state is incorporated in the effective density function to consider the large liquid/gas density ratio. The influences of inclined angle on droplet shape and evaporation rate are obtained and analyzed. The results show that for a fixed initial velocity, when the inclined angel increases, droplet deformation is significant as the motion between droplet and the surface is strengthened and the droplet evaporation rate gets faster since the heat transfer is enhanced. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The impingement and evaporation processes of droplet widely exist in many industrial fields such as fuel injection in combustion engines, spray drying and turbines. When a single droplet falls and impacts on an inclined hot surface under the effect of gravity, it evaporates after contacting with the surface due to the heated transfer. The inclined angle of surfaces has great effects on droplet dynamics and heat transfer. In this work, the pseudo-potential model and a thermal lattice Boltzmann model are combined to simulate the impact process and the heat transfer. Moreover, the Peng-Robinson equation of state is incorporated in the effective density function to consider the large liquid/gas density ratio. The influences of inclined angle on droplet shape and evaporation rate are obtained and analyzed. The results show that for a fixed initial velocity, when the inclined angel increases, droplet deformation is significant as the motion between droplet and the surface is strengthened and the droplet evaporation rate gets faster since the heat transfer is enhanced.</span></p> ]]> Lattice Boltzmann Simulation of a Single Droplet Impingement and Evaporation on Inclined Heated Surface rui ma jing gong yong wang weizhong li bo dong doi: 10.2495/CMEM-V6-N2-423-432 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 423 10.2495/CMEM-V6-N2-423-432 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-423-432 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-411-422 The main objectives of this work is to produce detailed velocity profile measurements over a range of operating conditions of two phase gas/liquid flow with low liquid fractions in horizontal and inclined pipes. The experiments are performed in a 15 m long stainless steel pipe section with internal diameter 56 mm at room temperature and atmospheric outlet pressure. Exxsol D60 oil (viscosity 1.30 mPa s, density 793 kg/m$^3$), water (viscosity 0.89 mPa s, density 999 kg/m$^3$) and air (viscosity 0.018 mPa s, density 1.22 kg/m$^3$) are used as test fluids. The pipe inclination is changed in the range from 5° upward to 5° downward. The measurements are made at mixture velocity, 5 m/s for different inlet liquid fractions. The cross-sectional distribution of phase fractions is measured using a traversable single-beam gamma densitometer. The particle image velocimetry (PIV) is utilized in order to obtain non-invasive instantaneous velocity measurements of the flow field. Based on the instantaneous local velocities, mean velocities, root mean squared velocities and Reynolds stresses are calculated. The measured mean velocity and turbulence profiles show a strong dependency with pipe inclination. The present measurements show that PIV can be successfully used as a practical measurement technique for multiphase flow applications with potential to become even more powerful in the near future as digital camera technology progresses. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The main objectives of this work is to produce detailed velocity profile measurements over a range of operating conditions of two phase gas/liquid flow with low liquid fractions in horizontal and inclined pipes. The experiments are performed in a 15 m long stainless steel pipe section with internal diameter 56 mm at room temperature and atmospheric outlet pressure. Exxsol D60 oil (viscosity 1.30 mPa s, density 793 kg/m$^3$), water (viscosity 0.89 mPa s, density 999 kg/m$^3$) and air (viscosity 0.018 mPa s, density 1.22 kg/m$^3$) are used as test fluids. The pipe inclination is changed in the range from 5° upward to 5° downward. The measurements are made at mixture velocity, 5 m/s for different inlet liquid fractions. The cross-sectional distribution of phase fractions is measured using a traversable single-beam gamma densitometer. The particle image velocimetry (PIV) is utilized in order to obtain non-invasive instantaneous velocity measurements of the flow field. Based on the instantaneous local velocities, mean velocities, root mean squared velocities and Reynolds stresses are calculated. The measured mean velocity and turbulence profiles show a strong dependency with pipe inclination. The present measurements show that PIV can be successfully used as a practical measurement technique for multiphase flow applications with potential to become even more powerful in the near future as digital camera technology progresses.</span></p> ]]> Particle Image Velocimetry Measurements of Stratified Gas-Liquid Flow in Horizontal and Inclined Pipes s. vestøl w.a.s. kumara m.c. melaaen doi: 10.2495/CMEM-V6-N2-411-422 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 411 10.2495/CMEM-V6-N2-411-422 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-411-422 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-385-397 For granular debris flows, two characteristics play a crucial role in their dynamic behavior: the pore- pressure feedback, which reduces the intergranular friction and, therefore, enhances the mobility of the whole mixture, and the non-linear deformational behavior that stems from the internal contact stress between grains. In a previous work, the entropy principle based on the formulation of Müller and Liu was exploited in order to find restrictions on the constitutive equations of a general grain-fluid multiphase mixture, including two additional internal variables. In this report, a thermodynamically consistent model for debris flows is depth-integrated and employed for numerical simulation.Including extra pore-pressure and hypoplastic stress, internal variables that are, respectively, described by a pressure diffusion equation and a transport equation related to the hypoplastic material, are considered. Comparison of the obtained results with those from classical debris flow models shows that the proposed thermodynamic model provides a phenomenological insight into the influence of the pore-pressure feedback and intergranular friction in the flow dynamics.To better understand the significance of the pore-pressure feedback and the intergranular friction, a simple grain-fluid material sliding on a slope with runout is numerically investigated by using depth- integrated model equations. A non-oscillatory, shock-capturing central-upwind scheme with the total variation diminishing property is applied for this purpose. Numerical results indicate the significant importance of the pore-pressure feedback and the hypoplastic behavior on determining the flow dynamics of debris flows. <![CDATA[ <p>For granular debris flows, two characteristics play a crucial role in their dynamic behavior: the pore- pressure feedback, which reduces the intergranular friction and, therefore, enhances the mobility of the whole mixture, and the non-linear deformational behavior that stems from the internal contact stress between grains. In a previous work, the entropy principle based on the formulation of Müller and Liu was exploited in order to find restrictions on the constitutive equations of a general grain-fluid multiphase mixture, including two additional internal variables. In this report, a thermodynamically consistent model for debris flows is depth-integrated and employed for numerical simulation.</p><p>Including extra pore-pressure and hypoplastic stress, internal variables that are, respectively, described by a pressure diffusion equation and a transport equation related to the hypoplastic material, are considered. Comparison of the obtained results with those from classical debris flow models shows that the proposed thermodynamic model provides a phenomenological insight into the influence of the pore-pressure feedback and intergranular friction in the flow dynamics.</p><p>To better understand the significance of the pore-pressure feedback and the intergranular friction, a simple grain-fluid material sliding on a slope with runout is numerically investigated by using depth- integrated model equations. A non-oscillatory, shock-capturing central-upwind scheme with the total variation diminishing property is applied for this purpose. Numerical results indicate the significant importance of the pore-pressure feedback and the hypoplastic behavior on determining the flow dynamics of debris flows.</p> ]]> Modeling Debris Flow: On the Influence of Pore Pressure Evolution and Hypoplasticity julian heß yongqi wang doi: 10.2495/CMEM-V6-N2-385-397 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 385 10.2495/CMEM-V6-N2-385-397 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-385-397 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-373-384 Flow patterns in oil-water carrying pipes vary due to the flow characteristics, fluid properties and pipe inclination. For inclined pipes, the gravity component along the pipe influences the flow patterns. Plug flow (PF) is one special flow pattern that occurs in slightly upward inclined pipe-lines. Mineral oil-Exxsol D60 (viscosity = 1.6 mPa.s, density =788 kg/m3) and water (viscosity = 1mPa.s, density = 997 kg/m3) were used as test-fluids. A test matrix was carried out to determine the possible flow patterns that occur at upward pipe inclinations +1° , +3° , +5° and +6° for low mixture velocities (0.2–0.5 m/s), and at water-cut 0.9. The plug flow regime was found only for +5° and +6° inclinations, while no plug flow was noticed at +1° and +3° inclinations. Plug flow was found only for lower flow velocity and higher water-cuts. Plug flow patterns were identified both through visual observation and by means of high-speed video imaging. Two new flow patterns ‘oil droplet clusters in continuous oil and water (OC/O&W)’ and ‘distinct oil droplet clusters in water (D-OC/W)’ were introduced, and they occur around the plug flow regime. High-speed images were post-processed for determination of the oil–water interface and subsequently used to calculate the water hold-up. The time averaged water hold up decreased with increasing mixture velocity due to the decrease of oil–water slip as a result of increased degree of dispersion. The oil plugs entrained more droplets as mixture velocity was increased, leading to high-frequency fluctuations of volume fraction of the oil plugs. Hold-up increased with increasing inclination due to the onset of plug flow, which leads to increased slip. The pressure drop over the test section was measured, and the frictional pressure drops were calculated using average water hold-up values. The frictional pressure drop increased with increasing mixture velocity, due to increased mixing and subsequent increase of effective viscosity. The frictional pressure drop decreased with increased inclination due to the appearing of oil plugs and the drag reduction effect associated with the plug flow. <![CDATA[ <p>Flow patterns in oil-water carrying pipes vary due to the flow characteristics, fluid properties and pipe inclination. For inclined pipes, the gravity component along the pipe influences the flow patterns. Plug flow (PF) is one special flow pattern that occurs in slightly upward inclined pipe-lines. Mineral oil-Exxsol D60 (viscosity = 1.6 mPa.s, density =788 kg/m3) and water (viscosity = 1mPa.s, density = 997 kg/m3) were used as test-fluids. A test matrix was carried out to determine the possible flow patterns that occur at upward pipe inclinations +1° , +3° , +5° and +6° for low mixture velocities (0.2–0.5 m/s), and at water-cut 0.9. The plug flow regime was found only for +5° and +6° inclinations, while no plug flow was noticed at +1° and +3° inclinations. Plug flow was found only for lower flow velocity and higher water-cuts. Plug flow patterns were identified both through visual observation and by means of high-speed video imaging. Two new flow patterns ‘oil droplet clusters in continuous oil and water (OC/O&W)’ and ‘distinct oil droplet clusters in water (D-OC/W)’ were introduced, and they occur around the plug flow regime. High-speed images were post-processed for determination of the oil–water interface and subsequently used to calculate the water hold-up. The time averaged water hold up decreased with increasing mixture velocity due to the decrease of oil–water slip as a result of increased degree of dispersion. The oil plugs entrained more droplets as mixture velocity was increased, leading to high-frequency fluctuations of volume fraction of the oil plugs. Hold-up increased with increasing inclination due to the onset of plug flow, which leads to increased slip. The pressure drop over the test section was measured, and the frictional pressure drops were calculated using average water hold-up values. The frictional pressure drop increased with increasing mixture velocity, due to increased mixing and subsequent increase of effective viscosity. The frictional pressure drop decreased with increased inclination due to the appearing of oil plugs and the drag reduction effect associated with the plug flow.</p> ]]> Characterization of Oil–Water Plug Related Flow in Slightly Inclined Pipes kshanthi perera saba mylvaganam rune w. time doi: 10.2495/CMEM-V6-N2-373-384 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 373 10.2495/CMEM-V6-N2-373-384 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-373-384 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-358-372 The present paper focusses on the numerical rebuilding of different multiphase flow regimes in a medium scale pipe system (6 inch). Principal investigations are performed by CFD to initiate hydrodynamic instabilities and develop them into the correct flow pattern (slug, stratified, etc.) at a given downwind position without applying artificial models or boundary conditions. The numerical predictions of the flow obtained by a volume of fluid CFD method (OpenFoam) are compared with available experimental data. Numerical investigations are performed with respect to grid resolution, initial conditions and turbulence modelling but also for obtaining a representative, comparable set of numerical and experimental data. For different flow regimes from slug flow to stratified flow good agreement with the experimental data was achieved with respect to the predicted flow regime and topology but also the forces predicted on the bend. Especially the large variation of the root mean squared values but also peak-to-peak values of the forces are predicted well by the numerical solutions for the different flow regimes. <![CDATA[ <p>The present paper focusses on the numerical rebuilding of different multiphase flow regimes in a medium scale pipe system (6 inch). Principal investigations are performed by CFD to initiate hydrodynamic instabilities and develop them into the correct flow pattern (slug, stratified, etc.) at a given downwind position without applying artificial models or boundary conditions. </p><p>The numerical predictions of the flow obtained by a volume of fluid CFD method (OpenFoam) are compared with available experimental data. Numerical investigations are performed with respect to grid resolution, initial conditions and turbulence modelling but also for obtaining a representative, comparable set of numerical and experimental data. </p><p>For different flow regimes from slug flow to stratified flow good agreement with the experimental data was achieved with respect to the predicted flow regime and topology but also the forces predicted on the bend. Especially the large variation of the root mean squared values but also peak-to-peak values of the forces are predicted well by the numerical solutions for the different flow regimes.</p> ]]> Numerical Rebuilding of Dynamic Instabilities and Forces in Multiphase Pipe Bend Flow andreas mack hrishikesh joshi stefan belfroid doi: 10.2495/CMEM-V6-N2-358-372 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 358 10.2495/CMEM-V6-N2-358-372 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-358-372 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-345-357 Vapor bubbles can be formed in liquids by increasing the temperature over the boiling threshold (evaporation) or by reducing the pressure below its vapor pressure threshold (cavitation). The liquid can be held in these tensile conditions (metastable states) for a long time without any bubble formation. The bubble nucleation is indeed an activated process, in fact a given amount of energy is needed to bring the liquid from that local stable condition into a more stable one, where a vapor bubble is formed. Crucial question in this field is how to correctly estimate the bubble nucleation rate, i.e. the amount of vapor bubbles formed in a given time and in a given volume of liquid, in different thermodynamic conditions. Several theoretical models have been proposed, ranging from classical nucleation theory, to density functional theory. These theories can give good estimate of the energy barriers but lack of a precise estimate of the nucleation rate, especially in complex systems. Molecular dynamics simulations can give more precise results, but the computational cost of this technique makes it unfeasible to be applied on systems larger than few tenth of nanometers. In this work the approach of fluctuating hydrodynamics has been embedded into a continuum diffuse interface modeling of the two-phase fluid. The resulting model provides a complete description of both the thermodynamic and fluid dynamic fields enabling the description of vapor-liquid phase change through stochastic fluctuations. The continuum model has been exploited to investigate the bubble nucleation rate in different metastable conditions. Such an approach has a huge impact since it reduces the computational cost and allows to investigate longer time scales and larger spatial scales with respect to more conventional techniques. <![CDATA[ <p>Vapor bubbles can be formed in liquids by increasing the temperature over the boiling threshold (evaporation) or by reducing the pressure below its vapor pressure threshold (cavitation). The liquid can be held in these tensile conditions (metastable states) for a long time without any bubble formation. The bubble nucleation is indeed an activated process, in fact a given amount of energy is needed to bring the liquid from that local stable condition into a more stable one, where a vapor bubble is formed. Crucial question in this field is how to correctly estimate the bubble nucleation rate, i.e. the amount of vapor bubbles formed in a given time and in a given volume of liquid, in different thermodynamic conditions. Several theoretical models have been proposed, ranging from classical nucleation theory, to density functional theory. These theories can give good estimate of the energy barriers but lack of a precise estimate of the nucleation rate, especially in complex systems. Molecular dynamics simulations can give more precise results, but the computational cost of this technique makes it unfeasible to be applied on systems larger than few tenth of nanometers. In this work the approach of fluctuating hydrodynamics has been embedded into a continuum diffuse interface modeling of the two-phase fluid. The resulting model provides a complete description of both the thermodynamic and fluid dynamic fields enabling the description of vapor-liquid phase change through stochastic fluctuations. The continuum model has been exploited to investigate the bubble nucleation rate in different metastable conditions. Such an approach has a huge impact since it reduces the computational cost and allows to investigate longer time scales and larger spatial scales with respect to more conventional techniques.</p> ]]> Fluctuating Hydrodynamics as a Tool to Investigate Nucleation of Cavitation Bubbles mirko gallo francesco magaletti carlo massimo casciola doi: 10.2495/CMEM-V6-N2-345-357 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 345 10.2495/CMEM-V6-N2-345-357 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-345-357 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-334-344 The present study deals with plumes of water, called here resurgent flows, which can result from the impact of a liquid jet on a reverse-flow liquid surface. This phenomenon has to be taken into account in the conception of the industrial device. Most of the studies on this topic are oriented towards the air entrainment created by a plunging jet. The aim of this study is twofold: to characterize the main parameters about the phenomenology of resurgent jets and to predict the resurgence generation using a dual numerical and experimental approach. A large test campaign had been realized and assesses the influence of several parameters such as velocities, diameter of jets, impinging angle thanks to an injection pipe put on a moving platform. It appears that the phenomenon induces high levels of loads and cannot be neglected when singular conditions are met. Experimental results were faced to numerical results in order to validate models. These results show a great accordance between experiments and calculations and therefore the capabilities of the numerical code STAR-CCM+© to restitute resurgent jets. <![CDATA[ <p>The present study deals with plumes of water, called here resurgent flows, which can result from the impact of a liquid jet on a reverse-flow liquid surface. This phenomenon has to be taken into account in the conception of the industrial device. Most of the studies on this topic are oriented towards the air entrainment created by a plunging jet. The aim of this study is twofold: to characterize the main parameters about the phenomenology of resurgent jets and to predict the resurgence generation using a dual numerical and experimental approach. A large test campaign had been realized and assesses the influence of several parameters such as velocities, diameter of jets, impinging angle thanks to an injection pipe put on a moving platform. It appears that the phenomenon induces high levels of loads and cannot be neglected when singular conditions are met. Experimental results were faced to numerical results in order to validate models. These results show a great accordance between experiments and calculations and therefore the capabilities of the numerical code STAR-CCM+© to restitute resurgent jets.</p> ]]> Experimental and Numerical Analysis of Liquid Counterflow Jets: Study of Resurgent Jet Generation dimitri domingie jean-baptiste deuff olivier perelman doi: 10.2495/CMEM-V6-N2-334-344 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 334 10.2495/CMEM-V6-N2-334-344 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-334-344 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-326-333 During their operation or in the event of an accident, power transformer can release a certain amount of oil in the subjacent soil. In order to avoid a fire hazard or any contamination to the environment, it is critical to capture any oil that was accidentally spilled. For this reason, catchment basins are placed below each power transformer and each basin is connected through pipes to a gravitational oil–water separator, which allows the oil droplets carried by the water flow to rise toward the surface and coalesce near the free surface. By doing so, the oil phase is separated from the mixture and it can be properly disposed afterwards. Prior to 1995, gravitational separators at Hydro-Québec have not been designed according to the American Petroleum Institute (API) standards [1] but this does not necessarily imply that such separators do not comply with the environmental legislation in place. Thus, in order to evaluate if modifications to the existing gravitational separators are required, Hydro-Québec has launched in 2012 an R&D project aimed at performing separator efficiency studies through a Computational Fluid Dynamics (CFD). In this paper, a numerical simulation of a gravitational oil–water separator in service at Hydro-Québec using an inhomogeneous multiphase model is presented. Moreover, a new configuration of the existing separator is numerically tested and the results show that its performance is significantly improved. <![CDATA[ <p>During their operation or in the event of an accident, power transformer can release a certain amount of oil in the subjacent soil. In order to avoid a fire hazard or any contamination to the environment, it is critical to capture any oil that was accidentally spilled. For this reason, catchment basins are placed below each power transformer and each basin is connected through pipes to a gravitational oil–water separator, which allows the oil droplets carried by the water flow to rise toward the surface and coalesce near the free surface. By doing so, the oil phase is separated from the mixture and it can be properly disposed afterwards. Prior to 1995, gravitational separators at Hydro-Québec have not been designed according to the American Petroleum Institute (API) standards [1] but this does not necessarily imply that such separators do not comply with the environmental legislation in place. Thus, in order to evaluate if modifications to the existing gravitational separators are required, Hydro-Québec has launched in 2012 an R&D project aimed at performing separator efficiency studies through a Computational Fluid Dynamics (CFD). In this paper, a numerical simulation of a gravitational oil–water separator in service at Hydro-Québec using an inhomogeneous multiphase model is presented. Moreover, a new configuration of the existing separator is numerically tested and the results show that its performance is significantly improved.</p> ]]> Numerical Study of an Oil–Water Flow in a Gravitational Separator federico torriano marie-claude lessard nathalie thibeault doi: 10.2495/CMEM-V6-N2-326-333 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 326 10.2495/CMEM-V6-N2-326-333 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-326-333 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-314-325 The present study shows new results from the recently proposed method for numerical simulations of the spray break-up of cavitating liquid jets. A three-component system consisting of liquid, vapor and gas is applied for the volume-of-fluid simulation of the liquid disintegration in order to track the liquid–gas interface. To keep the numerical effort moderate, the liquid–vapor interface is not resolved by the computational grid, there mass and momentum transfer are described within the Eulerian-Eulerian framework. The numerical method is applied on a simplified injector-like geometry from the literature operated with gasoline at low pressure difference. For quantification of the detached spray ligaments, a new evaluation algorithm has been developed and implemented into the applied CFD code. It scans the liquid volume fraction field for separated ligaments, and determines their position, size and velocity. Additionally the ligament extensions along the principal axes of inertia are determined in order to evaluate the non-sphericity of each ligament after break-up. The presented simulation technique allows detailed numerical investigations of the spray formation process on the micro-scale by taking into account nozzle cavitation, turbulence and aerodynamic forces. <![CDATA[ <p>The present study shows new results from the recently proposed method for numerical simulations of the spray break-up of cavitating liquid jets. A three-component system consisting of liquid, vapor and gas is applied for the volume-of-fluid simulation of the liquid disintegration in order to track the liquid–gas interface. To keep the numerical effort moderate, the liquid–vapor interface is not resolved by the computational grid, there mass and momentum transfer are described within the Eulerian-Eulerian framework. The numerical method is applied on a simplified injector-like geometry from the literature operated with gasoline at low pressure difference. For quantification of the detached spray ligaments, a new evaluation algorithm has been developed and implemented into the applied CFD code. It scans the liquid volume fraction field for separated ligaments, and determines their position, size and velocity. Additionally the ligament extensions along the principal axes of inertia are determined in order to evaluate the non-sphericity of each ligament after break-up. The presented simulation technique allows detailed numerical investigations of the spray formation process on the micro-scale by taking into account nozzle cavitation, turbulence and aerodynamic forces.</p> ]]> Numerical Simulation of Spray Break-Up from Cavitating Nozzle Flow by Combined Eulerian– Eulerian and Volume-of-Fluid Methods wilfried edelbauer patrick kolar david schellander zoran pavlovic raimund almbauer doi: 10.2495/CMEM-V6-N2-314-325 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 314 10.2495/CMEM-V6-N2-314-325 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-314-325 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-303-313 The blood flow properties in microvessels were examined through simulating the dynamics of deformable red blood cells suspended in plasma using dissipative particle dynamics. The cell membrane was considered as a spring-based triangulated network and the intercellular interaction was modeled by a Morse potential function. The cell distribution in the cross section indicated that red blood cells migrate away from the wall to the tube center, resulting in a cell-free layer near the wall and blunt velocity profile. The findings also showed that the bluntness of velocity profile increases with increasing hematocrit. In addition, the Fahraeus and Fahraeus–Lindqvist effects were captured through investigating the effects of tube diameter and hematocrit on the discharge hematocrit and relative apparent viscosity. It appears that this flow model can capture the blood flow behaviors under physiological and pathological conditions. <![CDATA[ <p>The blood flow properties in microvessels were examined through simulating the dynamics of deformable red blood cells suspended in plasma using dissipative particle dynamics. The cell membrane was considered as a spring-based triangulated network and the intercellular interaction was modeled by a Morse potential function. The cell distribution in the cross section indicated that red blood cells migrate away from the wall to the tube center, resulting in a cell-free layer near the wall and blunt velocity profile. The findings also showed that the bluntness of velocity profile increases with increasing hematocrit. In addition, the Fahraeus and Fahraeus–Lindqvist effects were captured through investigating the effects of tube diameter and hematocrit on the discharge hematocrit and relative apparent viscosity. It appears that this flow model can capture the blood flow behaviors under physiological and pathological conditions.</p> ]]> Dissipative Particle Dynamics Simulation of Multiple Deformable Red Blood Cells in a Vessel lanlan xiao yang liu shuo chen bingmei fu doi: 10.2495/CMEM-V6-N2-303-313 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 303 10.2495/CMEM-V6-N2-303-313 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-303-313 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-291-302 Overheating of power electronic devices has become a significant issue due to their continued miniaturization and increased heat flux that needs to be dissipated. Microchannel heat sinks utilising two-phase flow are capable of very high heat transfer rates and represent a possible means of cooling such devices. In this paper, we focus on two-phase liquid–liquid plug flow using water-based ferrofluid (magnetic nanofluid) plugs as the dispersed phase and silicone oil as the continuous phase. An external magnetic field was applied to generate enhanced mixing of the microfluidic flow. We show that material properties of the ferrofluid plug influence heat transfer properties of the microfluidic flow, and demonstrate that cooling performance is further enhanced by the application of an external magnetic field, which induces mixing. We also show that microchannel heat transfer using a ferrofluid is superior to that using de-ionized water as the dispersed phase for two-phase liquid-liquid plug flow. <![CDATA[ <p>Overheating of power electronic devices has become a significant issue due to their continued miniaturization and increased heat flux that needs to be dissipated. Microchannel heat sinks utilising two-phase flow are capable of very high heat transfer rates and represent a possible means of cooling such devices. In this paper, we focus on two-phase liquid–liquid plug flow using water-based ferrofluid (magnetic nanofluid) plugs as the dispersed phase and silicone oil as the continuous phase. An external magnetic field was applied to generate enhanced mixing of the microfluidic flow. We show that material properties of the ferrofluid plug influence heat transfer properties of the microfluidic flow, and demonstrate that cooling performance is further enhanced by the application of an external magnetic field, which induces mixing. We also show that microchannel heat transfer using a ferrofluid is superior to that using de-ionized water as the dispersed phase for two-phase liquid-liquid plug flow.</p> ]]> Ferrofluidic Plug Flow Heat Transfer Enhancement nicolette gan jia gui cameron stanley nam-trung nguyen gary rosengarten doi: 10.2495/CMEM-V6-N2-291-302 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 291 10.2495/CMEM-V6-N2-291-302 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-291-302 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-282-290 For energy saving and less environmental impact, efficient energy utilization is of importance. In a gasturbine engine, its performance increases as increasing temperature of the turbine inlet flow. However, turbine components are required to be protected from the high temperature flows. Recently, ceramic matrix composite (referred as CMC, hereafter) is expected to be utilized as protecting the gas-turbine components due to the excellent properties of CMC in high temperature conditions: low density, high strength and high rigidity. Therefore, the CMC allows us to increase the inlet temperature and leads to high performance of gas-turbine engines. On the other hand, sand erosion phenomenon is one of serious problems in gas-turbine engines. Sand particles ingested from the engine inlet impinge and erode the wall surfaces, which can cause engine failure. In order to prevent the sand erosion phenomenon, anti-erosion coatings have been developed and adopted for gas-turbines, although the anti-erosion characteristics of the CMC coating have not completely been clarified. The objective of the present paper is to perform numerical simulations of sand erosion phenomenon on the coated and the uncoated T106 CMC vanes in a low-pressure gas turbine. We investigate the flow field, particle trajectories and the eroded shape of the CMC turbine vanes. The results show that the erosion occurs near the leading edge and at the 90 percent axial chord on the pressure surface in both of the coated and uncoated cases. In the uncoated case, the severe erosion phenomenon is observed especially. Accordingly, we have concluded that the coating obviously played an important role in protecting the CMC vanes from sand erosion. <![CDATA[ <p>For energy saving and less environmental impact, efficient energy utilization is of importance. In a gasturbine engine, its performance increases as increasing temperature of the turbine inlet flow. However, turbine components are required to be protected from the high temperature flows. Recently, ceramic matrix composite (referred as CMC, hereafter) is expected to be utilized as protecting the gas-turbine components due to the excellent properties of CMC in high temperature conditions: low density, high strength and high rigidity. Therefore, the CMC allows us to increase the inlet temperature and leads to high performance of gas-turbine engines. On the other hand, sand erosion phenomenon is one of serious problems in gas-turbine engines. Sand particles ingested from the engine inlet impinge and erode the wall surfaces, which can cause engine failure. In order to prevent the sand erosion phenomenon, anti-erosion coatings have been developed and adopted for gas-turbines, although the anti-erosion characteristics of the CMC coating have not completely been clarified. The objective of the present paper is to perform numerical simulations of sand erosion phenomenon on the coated and the uncoated T106 CMC vanes in a low-pressure gas turbine. We investigate the flow field, particle trajectories and the eroded shape of the CMC turbine vanes. The results show that the erosion occurs near the leading edge and at the 90 percent axial chord on the pressure surface in both of the coated and uncoated cases. In the uncoated case, the severe erosion phenomenon is observed especially. Accordingly, we have concluded that the coating obviously played an important role in protecting the CMC vanes from sand erosion.</p> ]]> Numerical Investigation on Sand Erosion Phenomenon of Coated and Uncoated Vanes in Low-Pressure Gas Turbine yoshimasa fuma hiroya mamori naoya fukushima makoto yamamoto yoji okita doi: 10.2495/CMEM-V6-N2-282-290 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 282 10.2495/CMEM-V6-N2-282-290 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-282-290 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-269-281 A novel multi-scale theoretical model for coalescence rate of droplets induced by turbulence has been developed. This model proposed two kinds of interaction mechanisms between the underlying turbulent flow and droplets and can be a kernel function required for population balance model (PBM). Most previous models only considered the contribution of the eddies of size equal to the droplets to the coalescence since the velocity of droplet was assumed to be equal to that of eddies of same size; the sizes of droplets was usually assumed to fall in the inertial sub-range of turbulent energy spectrum and only considered the eddies in this sub-range to coalescence. But the distribution of the sizes of droplets may be quite wide in the device, considering the entire energy spectrum (i.e. containing the dissipation sub-range, the inertial sub-range and the energy-containing sub-range) may be more reasonable. The above assumptions in the previous models are no more needed in this work. A novel model based on the entire energy spectrum and the collisions between two droplets and between eddy and droplet has been derived. The contribution of eddies of different sizes to the coalescence has been considered. The results predicted by coupling novel model with PBM agree with experimental data. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">A novel multi-scale theoretical model for coalescence rate of droplets induced by turbulence has</span><span> </span>been developed. This model proposed two kinds of interaction mechanisms between the underlying turbulent flow and droplets and can be a kernel function required for population balance model (PBM). Most previous models only considered the contribution of the eddies of size equal to the droplets to the coalescence since the velocity of droplet was assumed to be equal to that of eddies<span> </span>of same size; the sizes of droplets was usually assumed to fall in the inertial sub-range of turbulent energy spectrum and only considered the eddies in this sub-range to coalescence. But the distribution of the sizes of droplets may be quite wide in the device, considering the entire energy spectrum (i.e. containing the dissipation sub-range, the inertial sub-range and the energy-containing sub-range)<span> </span>may be more reasonable. The above assumptions in the previous models are no more needed in this work. A novel model based on the entire energy spectrum and the collisions between two droplets<span> </span>and between eddy and droplet has been derived. The contribution of eddies of different sizes to the coalescence has been considered. The results predicted by coupling novel model with PBM agree<span> </span>with experimental<span> </span>data.</p> ]]> A Novel Multiscale Theoretical Model for Droplet Coalescence in Turbulent Dispersions shenggao gong luchang han he’an luo doi: 10.2495/CMEM-V6-N2-269-281 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 269 10.2495/CMEM-V6-N2-269-281 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-269-281 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-260-268 Transport phenomena in two-phase systems are studied when solving various problems problems of natural science or technology. One of the consti relations defined in porous media mechanics is the relation between the solid phase concentration and the hydraulic conductivity of a two-phase system. Forty-five experiments were carried out with a suspension consisting of water and kaolin. The one-dimensional equations of Darcian mechanics were applied to formulate the studied process mathematically. The nature of the process allowed for finding a solution to the forward problem. Fitting the theoretical solution to the experimental data made it possible to invert the problem and to get the sought hydraulic conductivity as a function of the suspension concentration. The method and the obtained results are presented and discussed. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Transport phenomena in two-phase systems are studied when solving various problems problems </span><span>of </span>natural science or technology. One of the consti relations defined in porous media mechanics is the relation between the solid phase concentration and the hydraulic conductivity of a two-phase <span>sys</span>tem. Forty-five experiments were carried out with a suspension consisting of water and kaolin. <span>The </span>one-dimensional equations of Darcian mechanics were applied to formulate the studied process <span>math</span>ematically. The nature of the process allowed for finding a solution to the forward problem. Fitting<span> </span>the theoretical<span> </span>solution<span> </span>to<span> </span>the<span> </span>experimental<span> </span>data<span> </span>made<span> </span>it<span> </span>possible<span> </span>to<span> </span>invert<span> </span>the<span> </span>problem<span> </span>and<span> </span>to<span> </span>get<span> </span>the<span> </span>sought hydraulic conductivity as a function of the suspension concentration. The method and the obtained results are presented and discussed.</p> ]]> Hydraulic Conductivity of a Suspension—An Inverse Problem jiri mls marketa sedlackova doi: 10.2495/CMEM-V6-N2-260-268 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 260 10.2495/CMEM-V6-N2-260-268 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-260-268 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-251-259 Dissolved air flotation (DAF) technologies are commonly used in water and wastewater treatment. In particular, flotation of suspended solids to pre-treat high salinity water such as seawater is now becoming more widespread, even though conductivity effects on microbubble formation and behaviour are not yet well known. Thus, a series of experiments were conducted with artificial sea water and distilled water to study the effects of conductivity on size and flow patterns of the air bubbles inside a pilot- scale DAF tank. The experimental set-up included a high-speed CCD camera to capture the generated microbubbles. Posterior image processing determined the bubble diameters. Also, fluorescein was used as a fluorescent tracer to follow flow paths. The viability of using fluorescein was first assessed at laboratory scale. The intensity of the dye was determined through molecular fluorescence as a function of the concentration using a high conductivity matrix. Furthermore, a stability study of the intensity along time was performed in order to ensure reliability of the experimental measurements. The results showed that bubble size decreased and dead areas increased when seawater was used instead of distilled water. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Dissolved air flotation (DAF) technologies are commonly used in water and wastewater treatment. In particular,</span><span> </span>flotation<span> </span>of<span> </span>suspended<span> </span>solids<span> </span>to<span> </span>pre-treat<span> </span>high<span> </span>salinity<span> </span>water<span> </span>such<span> </span>as<span> </span>seawater<span> </span>is<span> </span>now<span> </span>becoming more widespread, even though conductivity effects on microbubble formation and behaviour are not<span> </span>yet<span> </span>well<span> </span>known.<span> </span>Thus,<span> </span>a<span> </span>series<span> </span>of<span> </span>experiments<span> </span>were<span> </span>conducted<span> </span>with<span> </span>artificial<span> </span>sea<span> </span>water<span> </span>and<span> </span>distilled water to study the effects of conductivity on size and flow patterns of the air bubbles inside a pilot- scale DAF tank. The experimental set-up included a high-speed CCD camera to capture the generated microbubbles.<span> </span>Posterior<span> </span>image<span> </span>processing<span> </span>determined<span> </span>the<span> </span>bubble<span> </span>diameters.<span> </span>Also,<span> </span>fluorescein<span> </span>was<span> </span>used as a fluorescent tracer to follow flow paths. The viability of using fluorescein was first assessed at laboratory<span> </span>scale.<span> </span>The<span> </span>intensity<span> </span>of<span> </span>the<span> </span>dye<span> </span>was<span> </span>determined<span> </span>through<span> </span>molecular<span> </span>fluorescence<span> </span>as<span> </span>a<span> </span>function of the concentration using a high conductivity matrix. Furthermore, a stability study of the intensity along time was performed in order to ensure reliability of the experimental measurements. The results showed that bubble size decreased and dead areas increased when seawater was used instead of distilled<span> water.</span></p> ]]> Effects of Water Conductivity on Microbubble Size and Distribution for Seawater Flotation in Desalination Pre- Treatment Processes n. margarit c. bayona s. navea e. ferrero j.j. malfeito doi: 10.2495/CMEM-V6-N2-251-259 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 251 10.2495/CMEM-V6-N2-251-259 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-251-259 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-240-250 The drift flux formulation is widely regarded as being amenable to computationally efficient calculation of averaged slip between phases (i.e. averaged volume fraction) in multiphase flows. However, contrary to the common perception in practice that this formulation provides two simple data-fitting parameters for describing averaged slip, it is shown that these parameters cannot be mathematically disassociated from each other and are intricately related to both the averaged and local phase velocities and volume fractions. This derived fact also provides a rational explanation for the extreme difficulty in the past to resolve the influence of the local lateral distribution (multidimensional) effects of the dispersed phase in the flow on the averaged flow characteristics. Of further significance from this derivation is the fact that correlations for drift flux parameters in which these terms are expressed explicitly from each other cannot claim a better understanding of the flow physics unless they capture this inherent analytical bi- directional dependency. All of the multiphase flow variables that affect the drift velocity parameter also affect the distribution parameter. In terms of simulation applications, the new analytical derivations presented enable a re-formulation and unification of prior volume fraction models and an explanation for field observations of why a reduction in the drift velocity parameter will lead to reduction in the distribution parameter. As much as numerical computing and simulation methods are invaluable tools, the results of this work show that it is equally important to explore their mathematical basis and scien- tific understanding that can help to advance more efficient simulation of multiphase flow behaviors in the field. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The</span><span> </span>drift<span> </span>flux<span> </span>formulation<span> </span>is<span> </span>widely<span> </span>regarded<span> </span>as<span> </span>being<span> </span>amenable<span> </span>to<span> </span>computationally<span> </span>efficient<span> </span>calculation of<span> </span>averaged<span> </span>slip<span> </span>between<span> </span>phases<span> </span>(i.e.<span> </span>averaged<span> </span>volume<span> </span>fraction)<span> </span>in<span> </span>multiphase<span> </span>flows.<span> </span>However,<span> </span>contrary to the common perception in practice that this formulation provides two simple data-fitting<span> </span>parameters for describing averaged slip, it is shown that these parameters cannot be mathematically <span>disassociated </span>from each other and are intricately related to both the averaged and local phase velocities and volume fractions. This derived fact also provides a rational explanation for the extreme difficulty in the past to resolve the influence of the local lateral distribution (multidimensional) effects of the dispersed <span>phase </span>in the flow on the averaged flow characteristics. Of further significance from this derivation is the <span>fact </span>that<span> </span>correlations<span> </span>for<span> </span>drift<span> </span>flux<span> </span>parameters<span> </span>in<span> </span>which<span> </span>these<span> </span>terms<span> </span>are<span> </span>expressed<span> </span>explicitly<span> </span>from<span> </span>each<span> </span>other cannot claim a better understanding of the flow physics unless they capture this inherent analytical bi- directional<span> </span>dependency.<span> </span>All<span> </span>of<span> </span>the<span> </span>multiphase<span> </span>flow<span> </span>variables<span> </span>that<span> </span>affect<span> </span>the<span> </span>drift<span> </span>velocity<span> </span>parameter<span> also </span>affect the distribution parameter. In terms of simulation applications, the new analytical derivations presented enable a re-formulation and unification of prior volume fraction models and an explanation for field observations of why a reduction in the drift velocity parameter will lead to reduction in the distribution parameter. As much as numerical computing and simulation methods are invaluable <span>tools, </span>the results of this work show that it is equally important to explore their mathematical basis and scien- tific understanding that can help to advance more efficient simulation of multiphase flow behaviors <span>in </span>the<span> </span>field.</p> ]]> Finer Theoretical Aspects of the Drift Flux Family of Equations for Simulating Averaged Volume Fraction in Multiphase Flows a.s. nagoo m.m. sharma doi: 10.2495/CMEM-V6-N2-240-250 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 240 10.2495/CMEM-V6-N2-240-250 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-240-250 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-231-239 The main goal of the present grinding concept GrindBall is to develop a manufacturing process to machine micro structures [1] on hard and brittle materials, using a spherical and shaftless grinding tool. Thereby the negative effect of cutting speed variation caused by fixed rotational axes of conventional grinding pins is reduced. Spherical tools require new technologies for contactless tool drive and positioning [2] that are able to be miniaturised to a compact machining module and fit in the workspace of small machine tools [3]. Therefore, a fluidic drive and an electromagnetic bearing system were chosen for the GrindBall module as practically contactless technologies for power transmission [4]. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The main goal of the present grinding concept </span><em><span style="color: rgb(35, 31, 32)">GrindBall </span></em><span style="color: rgb(35, 31, 32)">is to develop a manufacturing process </span><span>to </span>machine<span> </span>micro<span> </span>structures<span> </span>[1]<span> </span>on<span> </span>hard<span> </span>and<span> </span>brittle<span> </span>materials,<span> </span>using<span> </span>a<span> </span>spherical<span> </span>and<span> </span>shaftless<span> </span>grinding<span> tool. </span>Thereby the negative effect of cutting speed variation caused by fixed rotational axes of conventional grinding pins is reduced. Spherical tools require new technologies for contactless tool drive and positioning [2] that are able to be miniaturised to a compact machining module and fit in the workspace <span>of </span>small machine tools [3]. Therefore, a fluidic drive and an electromagnetic bearing system were <span>chosen </span>for the GrindBall module as practically contactless technologies for power transmission [4].</p> ]]> Shear Force Analysis of an Oil-Driven Grinding Tool rodion groll christoph kühn doi: 10.2495/CMEM-V6-N2-231-239 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 231 10.2495/CMEM-V6-N2-231-239 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-231-239 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-0 <![CDATA[ ]]> Preface peter vorobieff carlos a. brebbia doi: 10.2495/CMEM-V6-N2-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 2 Article 0 10.2495/CMEM-V6-N2-0 https://www.acadlore.com/article/IJCMEM/2018_6_2/CMEM-V6-N2-0 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-98-109 In this work, a numerical framework for the direct numerical simulation of tsunami waves generated by landslide events is proposed. The method, implemented on the TermoFluids numerical platform, adopts a free surface model for the simulation of momentum equations; thus, considering the effect of air on the flow physics negligible. The effect of the solid motion on the flow is taken into account by means of a direct forcing immersed boundary method (IBM).The method is available for 3-D unstructured meshes; however, it can be integrated with an adaptive mesh refinement (AMR) tool to dynamically increase the local definition of the mesh in the vicinity of the interfaces, which separate the phases or in the presence of vortical structures.The method is firstly validated by simulating the entrance of objects into still water surfaces for 2-D and 3-D configurations. Next, the case of tsunami generation from a subaerial landslide is studied and the results are validated by comparison to experimental and numerical measurements. Overall, the model demonstrates its efficiency in the simulation of this type of physics, and a wide versatility in the choice of the domain discretization. <![CDATA[ <p>In this work, a numerical framework for the direct numerical simulation of tsunami waves generated by landslide events is proposed. The method, implemented on the TermoFluids numerical platform, adopts a free surface model for the simulation of momentum equations; thus, considering the effect of air on the flow physics negligible. The effect of the solid motion on the flow is taken into account by means of a direct forcing immersed boundary method (IBM).</p><p style="text-align: justify">The method is available for 3-D unstructured meshes; however, it can be integrated with an adaptive mesh refinement (AMR) tool to dynamically increase the local definition of the mesh in the vicinity of the interfaces, which separate the phases or in the presence of vortical structures.</p><p style="text-align: justify">The method is firstly validated by simulating the entrance of objects into still water surfaces for 2-D and 3-D configurations. Next, the case of tsunami generation from a subaerial landslide is studied and the results are validated by comparison to experimental and numerical measurements. Overall, the model demonstrates its efficiency in the simulation of this type of physics, and a wide versatility in the choice of the domain discretization.</p> ]]> Numerical Study of an Impulse Wave Generated by a Sliding Mass eugenio schillaci federico favre oscar antepara néstor balcázar asensi oliva doi: 10.2495/CMEM-V6-N1-98-109 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 98 10.2495/CMEM-V6-N1-98-109 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-98-109 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-86-97 Two-phase flows can be encountered in a wide variety of industrial applications including a nuclear reactor, boilers, chemical reactor, etc. Bubble column is a simple and commonly used way to investigate two-phase flow due to their relatively simple construction and ease of operation. In the study of two-phase flow, the knowledge of gas and liquid velocities are required for better understanding of transport phenomena. Therefore, many measurement techniques have been developed such as LDV and PIV. However, those measurement techniques for velocity measurements require transparent test section and obviously fail if working fluid is opaque. To overcome this problem, there is another one technique, Ultrasonic Velocity Profiler (UVP), which can obtain the velocity information of both gas and liquid phases in non-transparent test section and opaque liquid. Originally, the UVP only measures one-dimensional velocity profile. For two-dimensional flow mapping, it is necessary to measure two velocity component at one spatial point to form a vector. In the present work, measurement system with two ultrasonic array sensors have been developed for two-dimensional velocity measurement and tested at two-phase bubbly column flow. The measurement results of UVP were compared with PIV measurement result to evaluate performance of the system. In two-phase bubbly flow, the performance of measurement system with ultrasonic array sensor is evaluated as 20% comparing with PIV measurement results for one and two-dimensional velocity measurement. <![CDATA[ <p>Two-phase flows can be encountered in a wide variety of industrial applications including a nuclear reactor, boilers, chemical reactor, etc. Bubble column is a simple and commonly used way to investigate two-phase flow due to their relatively simple construction and ease of operation. In the study of two-phase flow, the knowledge of gas and liquid velocities are required for better understanding of transport phenomena. Therefore, many measurement techniques have been developed such as LDV and PIV. However, those measurement techniques for velocity measurements require transparent test section and obviously fail if working fluid is opaque. To overcome this problem, there is another one technique, Ultrasonic Velocity Profiler (UVP), which can obtain the velocity information of both gas and liquid phases in non-transparent test section and opaque liquid. Originally, the UVP only measures one-dimensional velocity profile. For two-dimensional flow mapping, it is necessary to measure two velocity component at one spatial point to form a vector. In the present work, measurement system with two ultrasonic array sensors have been developed for two-dimensional velocity measurement and tested at two-phase bubbly column flow. The measurement results of UVP were compared with PIV measurement result to evaluate performance of the system. In two-phase bubbly flow, the performance of measurement system with ultrasonic array sensor is evaluated as 20% comparing with PIV measurement results for one and two-dimensional velocity measurement.</p> ]]> Velocity Measurement on Two-Phase Air Bubble Column Flow Using Array Ultrasonic Velocity Profiler munkhbat batsaikhan ari hamdani hiroshige kikura doi: 10.2495/CMEM-V6-N1-86-97 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 86 10.2495/CMEM-V6-N1-86-97 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-86-97 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-71-85 In dense gas–solid fluidized beds the heat transfer to immersed objects is strongly coupled to the hydrodynamic behavior. The objective of this study is to experimentally and numerically assess the heat transfer coefficient around a horizontal tube in a Geldart B bubbling fluidized bed and derive a numerical-correlative approach for predicting the angular dependent heat transfer coefficient. The considered system consists of corundum as the solid bed material and air as the fluidization gas, entering the cylindrical geometry through a Tuyere nozzle distributor. Experimental data are obtained from a pilot scale test-rig with different tubular heat transfer probes and evaluated in a comprehensive uncertainty analysis. The resulting magnitude and angle dependent variations of the heat transfer coefficient at different superficial gas velocities are compared to three dimensional numerical simulations. The applied CFD model of the fluidized bed treats both gas and powder as Eulerian phases. The size distribution of the particles is described by two granular phases with corresponding mean diameters and a sphericity factor to account for their non-spherical shape. The fluid–solid interactions in this Multi Fluid Model are considered by incorporating the Kinetic Theory of Granular Flow and a sphericity-adapted drag model. The hydrodynamics at the tube surface, e.g. solid volume fraction, gas and particle velocities, are used for a novel numerical-correlative calculation of the angle dependent heat transfer coefficient between the bed material and the immersed tube. Special focus is set on depicting the particle contact time at the tube surface appropriately. The numerical results show the correct tendency of an increasing heat transfer coefficient with rising gas velocity and are partially in good agreement with the experimental observations. <![CDATA[ <p>In dense gas–solid fluidized beds the heat transfer to immersed objects is strongly coupled to the hydrodynamic behavior. The objective of this study is to experimentally and numerically assess the heat transfer coefficient around a horizontal tube in a Geldart B bubbling fluidized bed and derive a numerical-correlative approach for predicting the angular dependent heat transfer coefficient. The considered system consists of corundum as the solid bed material and air as the fluidization gas, entering the cylindrical geometry through a Tuyere nozzle distributor. Experimental data are obtained from a pilot scale test-rig with different tubular heat transfer probes and evaluated in a comprehensive uncertainty analysis. The resulting magnitude and angle dependent variations of the heat transfer coefficient at different superficial gas velocities are compared to three dimensional numerical simulations. The applied CFD model of the fluidized bed treats both gas and powder as Eulerian phases. The size distribution of the particles is described by two granular phases with corresponding mean diameters and a sphericity factor to account for their non-spherical shape. The fluid–solid interactions in this Multi Fluid Model are considered by incorporating the Kinetic Theory of Granular Flow and a sphericity-adapted drag model. The hydrodynamics at the tube surface, e.g. solid volume fraction, gas and particle velocities, are used for a novel numerical-correlative calculation of the angle dependent heat transfer coefficient between the bed material and the immersed tube. Special focus is set on depicting the particle contact time at the tube surface appropriately. The numerical results show the correct tendency of an increasing heat transfer coefficient with rising gas velocity and are partially in good agreement with the experimental observations.</p> ]]> Hydrodynamics and Heat Transfer Around a Horizontal Tube Immersed in a Geldart B Bubbling Fluidized Bed peter ostermeier annelies vandersickel moritz becker stephan gleis hartmut spliethoff doi: 10.2495/CMEM-V6-N1-71-85 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 71 10.2495/CMEM-V6-N1-71-85 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-71-85 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-59-70 We present a two-dimensional computational study of a shock interaction with a particle-seeded curtain where particles initially comprise 4% by volume, and the rest is air. If the initial depth of the curtain in the streamwise direction is variable, numerical results predict vortex formation in both the gas phase and the dispersed phase after the shock-curtain interaction. The phenomenon is distinct from baroclinic (Richtmyer–Meshkov) instability observed on gaseous density interfaces and is caused by the changes in the particle phase number density distribution and related interphase velocity changes. <![CDATA[ <p>We present a two-dimensional computational study of a shock interaction with a particle-seeded curtain where particles initially comprise 4% by volume, and the rest is air. If the initial depth of the curtain in the streamwise direction is variable, numerical results predict vortex formation in both the gas phase and the dispersed phase after the shock-curtain interaction. The phenomenon is distinct from baroclinic (Richtmyer–Meshkov) instability observed on gaseous density interfaces and is caused by the changes in the particle phase number density distribution and related interphase velocity changes.</p> ]]> Instabilities in a Shock Interaction with a Perturbed Curtain of Particles ricardo gonzalez izard sumanth reddy lingampally patrick wayne gustaaf jacobs peter vorobieff doi: 10.2495/CMEM-V6-N1-59-70 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 59 10.2495/CMEM-V6-N1-59-70 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-59-70 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-46-58 The Euler-Granular approach was used to predict pneumatic conveying characteristics of vertically upward dilute phase flow. Three-dimensional computational fluid dynamics simulations were carried out for 8 m long and 30.5 mm diameter circular pipe. The density of conveyed materials was 1020 kgm-3. Simulations for different particle diameters: 200 µm, 500 µm and 3 mm were performed. The air velocities ranged from 7 to 16 ms-1 and solid to air mass flow ratios ranged from 1.2 to 3.6. The main objective of this study was to analyse the sensitivity of specularity coefficient in Johnson and Jackson particle-wall boundary conditions on conveying characteristics. It was found that there is a significant sensitivity of certain ranges of specularity coefficients on pressure drop, air and particle velocities and solid distribution in pipe cross section. Among the tested range of the specularity coefficient values, some values are recommended for different particle sizes by comparing the predicted results with experimental data from existing literature. Moreover, it was also found that the coefficient of restitution for particle-wall collisions which counts the momentum loss by the walls in normal direction has less sensitivity on the results compared to that of specularity coefficient which counts the momentum loss by the walls in tangential direction. <![CDATA[ <p>The Euler-Granular approach was used to predict pneumatic conveying characteristics of vertically upward dilute phase flow. Three-dimensional computational fluid dynamics simulations were carried out for 8 m long and 30.5 mm diameter circular pipe. The density of conveyed materials was 1020 kgm-3. Simulations for different particle diameters: 200 µm, 500 µm and 3 mm were performed. The air velocities ranged from 7 to 16 ms-1 and solid to air mass flow ratios ranged from 1.2 to 3.6. The main objective of this study was to analyse the sensitivity of specularity coefficient in Johnson and Jackson particle-wall boundary conditions on conveying characteristics. It was found that there is a significant sensitivity of certain ranges of specularity coefficients on pressure drop, air and particle velocities and solid distribution in pipe cross section. Among the tested range of the specularity coefficient values, some values are recommended for different particle sizes by comparing the predicted results with experimental data from existing literature. Moreover, it was also found that the coefficient of restitution for particle-wall collisions which counts the momentum loss by the walls in normal direction has less sensitivity on the results compared to that of specularity coefficient which counts the momentum loss by the walls in tangential direction.</p> ]]> A Parametric Study for Euler-Granular Model in Dilute Phase Vertical Pneumatic Conveying w.k. hiromi ariyaratne prasanna welahettige morten c. melaaen doi: 10.2495/CMEM-V6-N1-46-58 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 46 10.2495/CMEM-V6-N1-46-58 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-46-58 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-35-45 Homogeneous nucleation of calcium carbonate is a common phenomenon in nature, which has attracted attention from researchers due to its importance in biomineralization processes, climatic changes and incrustations in pipelines. In this work, by using a numerical scheme based on SIMPLE algorithm, 3D numerical simulations are performed for the homogeneous nucleation of calcium carbonate in highly concentrated electrolyte solutions. For this purpose, one couples the Eulerian equations for multiphase flows to the discretized population balance equations, so that the resulting system of non-linear partial differential equations accounts for the mass transfer and changes in the particles size during the precipitation reaction. In order to validate the proposed model, experimental measurements of pH versus time and particles size distribution are compared with theoretical data. The remarkable agreement observed between the theoretical and experimental results indicates that the employed approach can be successfully used in studies of homogeneous nucleation of other sparingly soluble mineral salts. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Homogeneous nucleation of calcium carbonate is a common phenomenon in nature, which has attracted attention from researchers due to its importance in biomineralization processes, climatic changes and incrustations in pipelines. In this work, by using a numerical scheme based on SIMPLE algorithm, 3D numerical simulations are performed for the homogeneous nucleation of calcium carbonate in highly concentrated electrolyte solutions. For this purpose, one couples the Eulerian equations for multiphase flows to the discretized population balance equations, so that the resulting system of non-linear partial differential equations accounts for the mass transfer and changes in the particles size during the precipitation reaction. In order to validate the proposed model, experimental measurements of pH versus time and particles size distribution are compared with theoretical data. The remarkable agreement observed between the theoretical and experimental results indicates that the employed approach can be successfully used in studies of homogeneous nucleation of other sparingly soluble mineral salts.</span></p> ]]> Numerical Simulations for Homogeneous Nucleation of Calcium Carbonate in Concentrated Electrolyte Solutions martina costa reis maria de fátima brito sousa falah alobaid celso aparecido bertran yongqi wang doi: 10.2495/CMEM-V6-N1-35-45 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 35 10.2495/CMEM-V6-N1-35-45 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-35-45 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-23-34 The Aerosol Jet® direct-write technology enables microscale printing of functional inks on various substrates with complex shapes, which is of great interest in many applications. It deposits the ink material in a form of high-speed collimated mist stream of fine droplets with diameters typically ranging from 1 to 5 microns, through a deposition nozzle connected via mist transport pathways to a liquid atomizer. Because the liquid atomization process often produces droplets with a wide size distribution having diameters much larger than 5 microns, removal of large ink droplets becomes the primary task of mist transport pathway design in the Aerosol Jet® system development, especially for printing fine features down to the 10 micron range. In the same time, the mist transport pathways must allow smaller droplets to pass through for desired ink material throughput. Therefore, it is important to understand the physical principles for mist transport pathway design based on multiphase mist flow analysis. With simplified models of particles flowing with a carrier gas in straight tubes of various inclination angles, convenient analytical formulas can be derived (even with particle inertia effect included to describe trajectories of large droplets), for calculating the rate of removal of droplets of given sizes due to gravitational sedimentation as a function of tube diameter and length. Rather intricate effect of particle inertia on gravitational wall deposition is revealed by the analytical results. For mist pathways of more complicated geometries, an OpenFOAM® lagrangian solver is used for the mist flow simulation, to gain insights into the wall deposition behaviour of ink droplets during mist transport from the liquid atomizer to the ink deposition nozzle. Applications of such mist flow analysis for mist transport channel design are illustrated with practical examples. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The Aerosol Jet® direct-write technology enables microscale printing of functional inks on various substrates with complex shapes, which is of great interest in many applications. It deposits the ink material in a form of high-speed collimated mist stream of fine droplets with diameters typically ranging from 1 to 5 microns, through a deposition nozzle connected via mist transport pathways to a liquid atomizer. Because the liquid atomization process often produces droplets with a wide size distribution having diameters much larger than 5 microns, removal of large ink droplets becomes the primary task of mist transport pathway design in the Aerosol Jet® system development, especially for printing fine features down to the 10 micron range. In the same time, the mist transport pathways must allow smaller droplets to pass through for desired ink material throughput. Therefore, it is important to understand the physical principles for mist transport pathway design based on multiphase mist flow analysis. With simplified models of particles flowing with a carrier gas in straight tubes of various inclination angles, convenient analytical formulas can be derived (even with particle inertia effect included to describe trajectories of large droplets), for calculating the rate of removal of droplets of given sizes due to gravitational sedimentation as a function of tube diameter and length. Rather intricate effect of particle inertia on gravitational wall deposition is revealed by the analytical results. For mist pathways of more complicated geometries, an OpenFOAM® lagrangian solver is used for the mist flow simulation, to gain insights into the wall deposition behaviour of ink droplets during mist transport from the liquid atomizer to the ink deposition nozzle. Applications of such mist flow analysis for mist transport channel design are illustrated with practical examples.</span></p> ]]> Multiphase Flow Analysis of Mist Transport Behavior in Aerosol Jet® System james q. feng doi: 10.2495/CMEM-V6-N1-23-34 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 23 10.2495/CMEM-V6-N1-23-34 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-23-34 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-208-219 A coupled Conservative Level Set – Moving Mesh – Immersed Boundary method is formulated and validated against the three-dimensional gravity-driven falling drop problem. First, by employing Conservative Level-Set (CLS) method, the multiphase domain can be successfully handled, while the mass conservation is controlled. Then, by using an Arbitrary Lagrangian-Eulerian formulation (i.e. a moving mesh), the simulation domain can be optimized by reducing the domain size and by allowing an improved mesh, resulting in a computational resources saving. Finally, the use of an Immersed Boundary (IB) method allows to deal with intricate geometries. All these functionalities result in a versatile and robustness method to simulate bubbles/drops problems in complex geometries. The mentioned method was successfully used to thoroughly study the falling of a drop against a plane surface, providing detailed results including velocity evolution, mesh independence study, evolution of the vertical position of the drop, streamlines and vorticity fields, and profiles evolution. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">A coupled Conservative Level Set – Moving Mesh – Immersed Boundary method is formulated and validated against the three-dimensional gravity-driven falling drop problem. First, by employing </span><span>Con</span>servative<span> </span>Level-Set<span> </span>(CLS)<span> </span>method,<span> </span>the<span> </span>multiphase<span> </span>domain<span> </span>can<span> </span>be<span> </span>successfully<span> </span>handled,<span> </span>while<span> </span>the<span> </span>mass conservation is controlled. Then, by using an Arbitrary Lagrangian-Eulerian formulation (i.e. a <span>mov</span>ing mesh), the simulation domain can be optimized by reducing the domain size and by allowing an improved<span> </span>mesh,<span> </span>resulting<span> </span>in<span> </span>a<span> </span>computational<span> </span>resources<span> </span>saving.<span> Finally, </span>the<span> </span>use<span> </span>of<span> </span>an<span> Immersed Boundary (IB) method allows </span>to <span>deal with intricate geometries. </span>All these functionalities result in a versatile and robustness<span> </span>method<span> </span>to<span> </span>simulate<span> </span>bubbles/drops<span> </span>problems<span> </span>in<span> </span>complex<span> </span>geometries.<span> </span>The<span> </span>mentioned<span> </span>method was<span> </span>successfully<span> </span>used<span> </span>to<span> </span>thoroughly<span> </span>study<span> </span>the<span> </span>falling<span> </span>of<span> </span>a<span> </span>drop<span> </span>against<span> </span>a<span> </span>plane<span> </span>surface,<span> </span>providing<span> </span>detailed results including velocity evolution, mesh independence study, evolution of the vertical position of<span> </span>the drop, streamlines and vorticity fields, and profiles<span> </span>evolution.</p> ]]> On the Solution of the Problem of a Drop Falling Against a Plane by Using a Level Set – Moving Mesh – Immersed Boundary Method enrique gutiérrez federico favre néstor balcázar joaquim rigola doi: 10.2495/CMEM-V6-N1-208-219 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 208 10.2495/CMEM-V6-N1-208-219 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-208-219 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-198-207 Air–water flow in a 90° sharp elbow (mitre bend) is studied in a new purpose-built experimental facility at the University of Sheffield. For the first time, the two-phase flow is investigated in a mitre bend for water-based Reynolds numbers Rew = 5600–12800 and water-to-air mass flow rate ratios $\dot{m}_w / \dot{m}_a$ =10–3800. Four different flow patterns are observed in the upstream pipe (plug, slug, slug-annular and annular) by using a high-speed high-resolution camera. The results show that the perturbation length upstream and downstream of the elbow and the pressure drop are significantly affected by the flow patterns. Two new values of the Lockhart–Martinelli parameter C are found for the pressure drop across the elbow. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Air–water flow in a 90</span><span style="color: rgb(35, 31, 32); font-family: Symbol">°</span><span> </span><span style="color: rgb(35, 31, 32)">sharp elbow (mitre bend) is studied in a new purpose-built </span><span>experimental </span>facility at the University of Sheffield. For the first time, the two-phase flow is investigated in a<span> </span>mitre<span> </span>bend<span> </span>for<span> </span>water-based<span> </span>Reynolds<span> </span>numbers<span> </span><em>Re_{<span style="color: rgb(35, 31, 32)">w</span>}<span> </span></em><span style="color: rgb(35, 31, 32); font-family: Symbol">=</span><span style="color: rgb(35, 31, 32)"> 5600–12800</span><span> </span>and<span> </span>water-to-air<span> </span>mass<span> </span>flow<span> </span>rate <span style="color: rgb(35, 31, 32)">ratios</span><span> </span>$\dot{m}_w / \dot{m}_a$<em><span> </span></em><span style="color: rgb(35, 31, 32); font-family: Symbol">=</span><span style="color: rgb(35, 31, 32)">10–3800.</span><span> Fou</span>r<span> differen</span>t<span> flow pattern</span>s<span> ar</span>e<span> observe</span>d<span> i</span>n<span> th</span>e<span> upstrea</span>m<span> pip</span>e<span> (plug</span>,<span> slug, </span><span style="color: rgb(35, 31, 32)">slug-annular and annular) by using a high-speed high-resolution camera. The results show that the perturbation length upstream and downstream of the elbow and the pressure drop are significantly affected by the flow patterns. Two new values of the Lockhart–Martinelli parameter </span><em><span style="color: rgb(35, 31, 32)">C </span></em><span style="color: rgb(35, 31, 32)">are found for the pressure drop across the elbow.</span></p> ]]> Pattern-Based Pressure Drop of Air–Water Flow Across a 90° Sharp Mitre Elbow wameedh t. m. al-tameemi pierre ricco doi: 10.2495/CMEM-V6-N1-198-207 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 198 10.2495/CMEM-V6-N1-198-207 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-198-207 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-186-197 The quantification of overall mass transfers in gas–liquid systems depends on the spatial evolution of the relevant variables close to the interface of the two phases. When turbulence is present (in the present study the turbulence is considered in the liquid phase), the methods of treating the problem consider the differential form of the momentum and mass conservation equations. The continuous hypothesis that underlies these equations in principle allows verifying the limiting trends very close to the interface. Because the theoretical concepts of turbulence are defined using statistical tools, the mentioned verification depends on the intrinsic definitions used in the statistical approach. In this study the turbulent mass transfer parameters are calculated for the thin region close to the interface based on the tool of random square waves (RSW). Theoretical results are obtained and analyzed in the context of existing experimental data and conceptual discussions of the literature, using a constant ‘reduction function’, a parameter defined in this methodology. The results of the present analysis show that the RSW method allows obtaining functional trends, as well as indicate the adequacy of using a variable reduction function to better represent reality. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The quantification of overall mass transfers in gas–liquid systems depends on the spatial evolution </span><span>of </span>the<span> </span>relevant<span> </span>variables<span> </span>close<span> </span>to<span> </span>the<span> </span>interface<span> </span>of<span> </span>the<span> </span>two<span> </span>phases.<span> </span>When<span> </span>turbulence<span> </span>is<span> </span>present<span> </span>(in<span> </span>the<span> </span>present study<span> </span>the<span> </span>turbulence<span> </span>is<span> </span>considered<span> </span>in<span> </span>the<span> </span>liquid<span> </span>phase),<span> </span>the<span> </span>methods<span> </span>of<span> </span>treating<span> </span>the<span> </span>problem<span> </span>consider<span> the </span>differential form of the momentum and mass conservation equations. The continuous hypothesis that underlies these equations in principle allows verifying the limiting trends very close to the interface. Because the theoretical concepts of turbulence are defined using statistical tools, the mentioned <span>veri</span>fication depends on the intrinsic definitions used in the statistical approach. In this study the turbulent mass transfer parameters are calculated for the thin region close to the interface based on the tool of random square waves (RSW). Theoretical results are obtained and analyzed in the context of existing experimental data and conceptual discussions of the literature, using a constant ‘reduction function’, a parameter defined in this methodology. The results of the present analysis show that the RSW <span>method </span>allows<span> </span>obtaining<span> </span>functional<span> </span>trends,<span> </span>as<span> </span>well<span> </span>as<span> </span>indicate<span> </span>the<span> </span>adequacy<span> </span>of<span> </span>using<span> </span>a<span> </span>variable<span> </span>reduction<span> </span>function to better represent<span> </span>reality.</p> ]]> Turbulence Aspects of Mass Transfer in the Thin Interfacial Region of the Concentration Boundary Layer in Gas–Liquid Systems harry edmar schulz francisco antonio loyola lavin bruno batista gonçalves doi: 10.2495/CMEM-V6-N1-186-197 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 186 10.2495/CMEM-V6-N1-186-197 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-186-197 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-176-185 Flash boiling is the rapid phase change of a pressurised fluid that emerges to ambient conditions below its vapour pressure. Flashing of a flowing liquid through an orifice or a nozzle can occur either inside or outside the nozzle depending on the local pressure and geometry. Vapour generation during flashing leads to interfacial interactions that eventually influence the jet.Empirical models in the literature for simulating the inter-phase heat transfer employ many simplifying assumptions, which limits their applicability. Typical models, usually derived from cavitation, fail to describe the physics of heat and mass transfer, making them unreliable for flashing. The Homogeneous Relaxation Model (HRM) is a reliable model able to capture heat transfer under these conditions accounting for the non-equilibrium vapour generation. This approach uses a relaxation term in the transport equation for the vapour. On the basis of the generic compressible flow solver within the open source computational fluid dynamics (CFD) code OpenFOAM, the HRM has been implemented to create a dedicated new solver HRMSonicELSAFoam. An algorithm that links the standard pressure–velocity coupling algorithm to the HRM is used. In this method, a pressure equation is derived which employs the continuity equation including compressibility effects. A relaxation term has been defined such that the instantaneous quality would relax to the equilibrium value over a given timescale. Although it is possible to consider this timescale constant, it is calculated via an empirical correlation in the present study.Validations have been carried out by simulating two-phase flows through sharp-edged orifices. The relatively good agreement achieved has demonstrated that the solver accurately calculates the pressure and vapour mass fraction. This demonstrates the potential of HRMSonicELSAFoam for flash boiling simulations and predicting the properties of the subsequent flash atomisation. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Flash</span><span> </span>boiling<span> </span>is<span> </span>the<span> </span>rapid<span> </span>phase<span> </span>change<span> </span>of<span> </span>a<span> </span>pressurised<span> </span>fluid<span> </span>that<span> </span>emerges<span> </span>to<span> </span>ambient<span> </span>conditions<span> below </span>its vapour pressure. Flashing of a flowing liquid through an orifice or a nozzle can occur either inside or<span> </span>outside<span> </span>the<span> </span>nozzle<span> </span>depending<span> </span>on<span> </span>the<span> </span>local<span> </span>pressure<span> </span>and<span> </span>geometry.<span> </span>Vapour<span> </span>generation<span> </span>during<span> </span>flashing leads to interfacial interactions that eventually influence the<span> </span>jet.</p><p><span style="color: rgb(35, 31, 32)">Empirical models in </span><span>the literature for simulating the inter-phase heat transfer employ many simplifying assumptions, which limits their applicability. Typical models, usually derived from cavitation, fail to describe the physics </span>of <span>heat and mass transfer, making them unreliable for flashing. The Homogeneous Relaxation Model (HRM) </span>is<span> </span>a<span> reliable model able </span>to<span> capture heat transfer under these conditions accounting for the non-equilibrium vapour generation. This approach uses </span>a <span>relaxation term </span>in <span>the transport equation for the vapour. </span>On <span>the basis </span>of <span>the generic compressible </span>flow <span>solver within the open source computational fluid dynamics (CFD) code OpenFOAM, the HRM has been implemented </span>to <span>create </span>a <span>dedicated new solver HRMSonicELSAFoam. </span>An <span>algorithm that links the standard pressure–velocity coupling algorithm </span>to <span>the HRM </span>is <span>used. </span>In <span>this method, </span>a <span>pressure equation </span>is <span>derived which employs the continuity equation including compressibility effects. </span>A <span>relaxation term has been defined such that the instantaneous quality would relax </span>to <span>the equilibrium value over </span>a <span>given timescale. Although </span>it is <span>possible </span>to <span>consider this timescale constant, </span>it<span> </span>is<span> calculated via </span>an<span> empirical correlation </span>in<span> the present study.</span></p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">Validations</span><span> </span>have<span> </span>been<span> </span>carried<span> </span>out<span> </span>by<span> </span>simulating<span> </span>two-phase<span> </span>flows<span> </span>through<span> </span>sharp-edged<span> </span>orifices.<span> </span>The relatively good agreement achieved has demonstrated that the solver accurately calculates the pressure and vapour mass fraction. This demonstrates the potential of HRMSonicELSAFoam for flash boiling simulations and predicting the properties of the subsequent flash<span> </span>atomisation.</p> ]]> Numerical Simulation of Flash-Boiling Through Sharp-Edged Orifices konstantinos lyras siaka dembele elena vyazmina simon jallais jennifer wen doi: 10.2495/CMEM-V6-N1-176-185 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 176 10.2495/CMEM-V6-N1-176-185 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-176-185 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-162-175 This study was devoted to investigate the interaction between platelets and blood cells in a blood plasma by using computational fluid dynamics (CFD). In this study, we developed a flow solver to solve the two-dimensional incompressible solid–liquid multiphase flow including collision and adhesion effects. This solver is based on equally-spaced Cartesian mesh and immersed boundary method (IBM) to represent the platelets and red blood cells including the interaction. We proposed a new adhesion algorithm to simulate the collision and interaction of the platelet–platelet and platelet–blood vessel. This adhesive strength determined by Kelvin Voigt model is enforced on the immersed boundary. In addition, we introduced a collision algorithm for complex-shaped object to analyze the flow including real blood cells. In the previous study by Kamada et al. [1], the moving particle semi-implicit (MPS) method was adopted to simulate the behaviour of blood plasma, platelets and red blood cells. From this study, it was confirmed that the number of adhesion platelet increases with the value of shear rate at the wall. Then, in this study, we analyzed the solid–liquid multiphase channel flow to confirm the deposit of the platelet. The channel flow including an obstacle of a medical stent and the moving cylinders of platelets was investigated for the comparison with the previous study. The Reynolds number based on the channel height was set to be between 5 and 50. As results, we confirmed that the platelets adhere to the wall due to the separation and vortex generation behind the obstacle. The influence of the vortex became more effective with increasing the Reynolds number. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">This study was devoted to investigate the interaction between platelets and blood cells in a</span><span> blood plasma by using computational fluid dynamics (CFD). In this study, we developed </span>a <span>flow solver to solve the two-dimensional incompressible solid–liquid multiphase flow including collision and adhesion effects. This solver is based on equally-spaced Cartesian mesh and immersed boundary method (IBM) to represent the platelets and red blood cells including the interaction. We proposed </span>a <span>new adhesion algorithm to simulate the collision and interaction of the platelet–platelet and platelet–blood vessel. This adhesive strength determined by Kelvin Voigt model is enforced on the immersed boundary. In addition, we introduced </span>a<span> collision algorithm for complex-shaped object to analyze the flow including real blood cells. In the previous study by Kamada </span><em><span>et al</span></em><span>. [1], the moving particle semi-implicit (MPS) method was adopted to simulate the behaviour of blood plasma, platelets and red blood cells. From this study, it was confirmed that the number of adhesion platelet increases with the value of shear rate at the wall. Then, in this study, we analyzed the solid–liquid multiphase channel flow to confirm the deposit of the platelet. The channel flow including an obstacle of </span>a<span> medical stent and the moving cylinders of platelets was investigated for the comparison with the previous study. The Reynolds number based on the channel height was set to be between </span>5 <span>and 50. As results, we confirmed that the platelets adhere to the wall due to the separation and vortex generation behind the obstacle. The influence of the vortex became more effective with increasing the Reynolds number.</span></p> ]]> Numerical Simulation on Solid–Liquid Multiphase Flow Including Complex-Shaped Objects with Collision and Adhesion Effects Using Immersed Boundary Method mamoru hosaka takayuki nagata shun takahashi kota fukuda doi: 10.2495/CMEM-V6-N1-162-175 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 162 10.2495/CMEM-V6-N1-162-175 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-162-175 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-152-161 Experimental work on high viscosity two-phase flows is presented. Newtonian mixtures were produced by simultaneously injecting Glycerine, with dynamic viscosity of 1.2 Pa.s (1,200 cP), and air. Then, the analysed flow developed in a horizontal pipe with a length-to-diameter ratio L/d=500. Various combinations of gas and liquid flow rates were considered within the respective ranges 1.66 (1.66×10−3≤qg≤3.33×10−3)m3/s, and (0.125×10−3≤ql≤0.785×10−3)m3/s. The experiments show that only intermittent flow patterns can be produced with the flow rates under consideration. Furthermore, a preliminary comparison with some well-known correlations suggests that the typical methods could yield inadequate predictions of the flow properties. Therefore, an alternative analysis based on the spectral content of the pressures is considered. This method allows for a proper characterization of a given flow in terms of its unique spectral 'footprint', which globally condenses all aspects of the underlying dynamics. <![CDATA[ <p>Experimental work on high viscosity two-phase flows is presented. Newtonian mixtures were produced by simultaneously injecting Glycerine, with dynamic viscosity of 1.2 Pa.s (1,200 cP), and air. Then, the analysed flow developed in a horizontal pipe with a length-to-diameter ratio L/d=500. Various combinations of gas and liquid flow rates were considered within the respective ranges 1.66 (1.66×10⁻³≤qg≤3.33×10⁻³)m³/s, and (0.125×10−3≤ql≤0.785×10−3)m³/s. The experiments show that only intermittent flow patterns can be produced with the flow rates under consideration. Furthermore, a preliminary comparison with some well-known correlations suggests that the typical methods could yield inadequate predictions of the flow properties. Therefore, an alternative analysis based on the spectral content of the pressures is considered. This method allows for a proper characterization of a given flow in terms of its unique spectral 'footprint', which globally condenses all aspects of the underlying dynamics.</p> ]]> Horizontal Evolution of Intermittent Gas- Liquid Flows with Highly Viscous Phases j. hernandez j.c. montiel a. palacio-perez a. rodríguez-valdés j.e.v. guzmán doi: 10.2495/CMEM-V6-N1-152-161 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 152 10.2495/CMEM-V6-N1-152-161 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-152-161 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-139-151 The structure of the two-phase flow inside the nozzle of an aerated-liquid injector and in the near field of the discharged plumes was experimentally explored with synchrotron x-ray diagnostics, including x-ray radiography, x-ray fluorescence, and x-ray high-speed imaging. One axisymmetric beryllium aerated liquid injector featuring the inside-out aerating scheme was fabricated to mate with three aerating tube designs for the creation of two-phase flows. Water and nitrogen were doped with x-ray fluorescent elements at low concentrations to facilitate the x-ray diagnostics. Quantitative time-averaged liquid mass distributions for the two-phase mixture were successfully obtained from both radiography and fluorescence measurements. Averaged flow properties, such as liquid density and liquid velocity, at various cross-sections, were also derived from these measurements. Temporal formation and evolution of the two-phase mixture inside the aerated-liquid injector were also characterized with high-speed imaging. It was found that an annular flow is typically created in the two-phase mixture near the nozzle exit, despite the complex fluid dynamics in the liquid/gas interaction, flow passage volume change, and recirculation zone. The two-phase flow structures in the nozzle and the spray regions created from the present injector and aerating tube configurations are highly similar for a given injection condition. The major factor contributing to the similarity of the two-phase flow structures in the two regions may be the large area contraction ratio between the mixing chamber and the nozzle passage, which leads to a significant increase in flow speed and thus to aerodynamic stretching of the two-phase flow into fine structures. <![CDATA[ <p>The structure of the two-phase flow inside the nozzle of an aerated-liquid injector and in the near field of the discharged plumes was experimentally explored with synchrotron x-ray diagnostics, including x-ray radiography, x-ray fluorescence, and x-ray high-speed imaging. One axisymmetric beryllium aerated liquid injector featuring the inside-out aerating scheme was fabricated to mate with three aerating tube designs for the creation of two-phase flows. Water and nitrogen were doped with x-ray fluorescent elements at low concentrations to facilitate the x-ray diagnostics. Quantitative time-averaged liquid mass distributions for the two-phase mixture were successfully obtained from both radiography and fluorescence measurements. Averaged flow properties, such as liquid density and liquid velocity, at various cross-sections, were also derived from these measurements. Temporal formation and evolution of the two-phase mixture inside the aerated-liquid injector were also characterized with high-speed imaging. It was found that an annular flow is typically created in the two-phase mixture near the nozzle exit, despite the complex fluid dynamics in the liquid/gas interaction, flow passage volume change, and recirculation zone. The two-phase flow structures in the nozzle and the spray regions created from the present injector and aerating tube configurations are highly similar for a given injection condition. The major factor contributing to the similarity of the two-phase flow structures in the two regions may be the large area contraction ratio between the mixing chamber and the nozzle passage, which leads to a significant increase in flow speed and thus to aerodynamic stretching of the two-phase flow into fine structures.</p> ]]> Characterization of Time-Averaged and Temporal Two-Phase Flow Structures in Aerated-Liquid Jets Using X-Ray Diagnostics kuo-cheng lin alan l. kastengren scott j. peltier campbell d. carter doi: 10.2495/CMEM-V6-N1-139-151 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 139 10.2495/CMEM-V6-N1-139-151 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-139-151 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-132-138 We investigated gas–particle flows by using the three-dimensional incompressible Navier–Stokes equation with the immersed boundary method (IBM) to treat particles–wall collisions. We compared flow structures from the two-way coupled simulation with the one-way simulation that is usually used in the industrial simulation. In this study, all objectives, which are particles and walls, are defined by the level-set function for the ghost-cell method of the IBM. The proposed algorithms to represent particle–particle and particle–wall collisions are simple and stable for the coupling simulation. More- over, flow structures obtained with the coupled simulation of the moving, colliding and rebounding particles are in good agreement with the previous numerical and experimental results. The one-way and two-way coupling simulations were carried out based on a number of particles of 50, 100 and 200, respectively. As a result, the one-way scheme indicated more frequently collisions on the particle and wall than the two-way scheme. The reason is that the one-way scheme ignored the particle–flow interactions. <![CDATA[ <p>We investigated gas–particle flows by using the three-dimensional incompressible Navier–Stokes equation with the immersed boundary method (IBM) to treat particles–wall collisions. We compared flow structures from the two-way coupled simulation with the one-way simulation that is usually used in the industrial simulation. In this study, all objectives, which are particles and walls, are defined by the level-set function for the ghost-cell method of the IBM. The proposed algorithms to represent particle–particle and particle–wall collisions are simple and stable for the coupling simulation. More- over, flow structures obtained with the coupled simulation of the moving, colliding and rebounding particles are in good agreement with the previous numerical and experimental results. The one-way and two-way coupling simulations were carried out based on a number of particles of 50, 100 and 200, respectively. As a result, the one-way scheme indicated more frequently collisions on the particle and wall than the two-way scheme. The reason is that the one-way scheme ignored the particle–flow interactions.</p> ]]> Investigation of a Gas–Particle Flow with Particle–Particle and Particle–Wall Collisions by Immersed Boundary Method yusuke mizuno takuya inoue shun takahashi kota fukuda doi: 10.2495/CMEM-V6-N1-132-138 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 132 10.2495/CMEM-V6-N1-132-138 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-132-138 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-120-131 The ability to accurately predict the volume fraction of different phases flowing in a pipe is of extreme importance to nuclear and oil industries, among others. This article will focus on the application of a single-beam gamma densitometer to investigate gas/liquid flows with low liquid fractions in horizontal and inclined pipes. The experiments are performed in a 15 m long, 56 mm diameter, inclinable stainless steel pipe using Exxsol D60 oil (viscosity 1.30 mPa s, density 793 kg/m3), water (viscosity 0.89 mPa s, density 999 kg/m3) and air (viscosity 0.018 mPa s, density 1.22 kg/m3) as test fluids. The test pipe inclination is changed in the range from 5º upward to 5º downward. Experimental measurements are reported at three different mixture velocities, 5, 10 and 15 m/s, and the inlet liquid fraction is varied from 0.0010 to 0.0100. In the experiments, the vertical interface position is measured by traversing horizontal gamma beams, and the curvature of the interface is measured by traversing vertical and angular gamma beams. <![CDATA[ <p>The ability to accurately predict the volume fraction of different phases flowing in a pipe is of extreme importance to nuclear and oil industries, among others. This article will focus on the application of a single-beam gamma densitometer to investigate gas/liquid flows with low liquid fractions in horizontal and inclined pipes. The experiments are performed in a 15 m long, 56 mm diameter, inclinable stainless steel pipe using Exxsol D60 oil (viscosity 1.30 mPa s, density 793 kg/m3), water (viscosity 0.89 mPa s, density 999 kg/m3) and air (viscosity 0.018 mPa s, density 1.22 kg/m3) as test fluids. The test pipe inclination is changed in the range from 5º upward to 5º downward. Experimental measurements are reported at three different mixture velocities, 5, 10 and 15 m/s, and the inlet liquid fraction is varied from 0.0010 to 0.0100. In the experiments, the vertical interface position is measured by traversing horizontal gamma beams, and the curvature of the interface is measured by traversing vertical and angular gamma beams.</p> ]]> Gamma Densitometry Measurements of Gas/ Liquid Flow with Low Liquid Fractions in Horizontal and Inclined Pipes s. vestøl w.a.s. kumara m.c. melaaen doi: 10.2495/CMEM-V6-N1-120-131 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 120 10.2495/CMEM-V6-N1-120-131 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-120-131 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-110-119 A method is developed to determine the hydraulic resistance in Safety Injection Tanks (SIT) with Fluidic Device (FD), which is to be used in the system thermal-hydraulic calculation of Large Break Loss-Of-Coolant Accident (LBLOCA) of Advance Power Reactors 1400 (APR1400). From the overall loss factor estimated from the SIT blowdown test data, the loss factor through the standpipe flow path and the one through the connecting holes of FD are determined from the hydrodynamic consideration. Also, a range of uncertainty of the hydraulic resistances is obtained by confirming that the trend of the SIT test data is covered by the results from the calculations of the test sequence using the set of lower bound K-factors and the set of upper bound K-factors, respectively. Nitrogen release during the blow- down test is discussed in terms of its amount and timing. Implementing the K-factors and the related modelling scheme of SIT, a LBLOCA of APR1400 is calculated using a system thermal-hydraulic code, MARS-KS 1.4. Fuel cladding response and nitrogen gas intrusion to the core are investigated. Sensitivity study is conducted to support to address the effect of uncertainty of SIT/FD to fuel cladding thermal response. <![CDATA[ <p>A method is developed to determine the hydraulic resistance in Safety Injection Tanks (SIT) with Fluidic Device (FD), which is to be used in the system thermal-hydraulic calculation of Large Break Loss-Of-Coolant Accident (LBLOCA) of Advance Power Reactors 1400 (APR1400). From the overall loss factor estimated from the SIT blowdown test data, the loss factor through the standpipe flow path and the one through the connecting holes of FD are determined from the hydrodynamic consideration. Also, a range of uncertainty of the hydraulic resistances is obtained by confirming that the trend of the SIT test data is covered by the results from the calculations of the test sequence using the set of lower bound K-factors and the set of upper bound K-factors, respectively. Nitrogen release during the blow- down test is discussed in terms of its amount and timing. Implementing the K-factors and the related modelling scheme of SIT, a LBLOCA of APR1400 is calculated using a system thermal-hydraulic code, MARS-KS 1.4. Fuel cladding response and nitrogen gas intrusion to the core are investigated. Sensitivity study is conducted to support to address the effect of uncertainty of SIT/FD to fuel cladding thermal response.</p> ]]> Nitrogen Gas Behavior in Safety Injection Tank with Fluidic Device and Effect on Core Cooling young seok bang doi: 10.2495/CMEM-V6-N1-110-119 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 110 10.2495/CMEM-V6-N1-110-119 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-110-119 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-11-22 The Young–Laplace equation describes the stress balance between the interfacial tension and the gravi- tational body force. Its modified form can be applied to model the dynamics of the interface of the two-phase flow. It is analytically difficult to solve the Young–Laplace equation due to its strong non- linearity, in the form of the surface curvature and the implicit body force on the interface. This work aims to numerically solve the Young–Laplace equation with a finite-volume method (FVM) and an overlapped grid. The overlapped grid allocates the variable and its derivative together at every grid point, and is compared with the traditional staggered grid. The proposed overlapped grid can achieve fourth-order numerical accuracy, which is higher than the second-order accuracy of the staggered grid. Also, the overlapped grid, with full states defined at every grid point, offers convenience to the imple- mentation of the boundary condition as well as the coupling of multi-physics. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The Young–Laplace equation describes the stress balance between the interfacial tension and the gravi- tational body force. Its modified form can be applied to model the dynamics of the interface of the two-phase flow. It is analytically difficult to solve the Young–Laplace equation due to its strong non- linearity, in the form of the surface curvature and the implicit body force on the interface. This work aims to numerically solve the Young–Laplace equation with a finite-volume method (FVM) and an overlapped grid. The overlapped grid allocates the variable and its derivative together at every grid point, and is compared with the traditional staggered grid. The proposed overlapped grid can achieve fourth-order numerical accuracy, which is higher than the second-order accuracy of the staggered grid. Also, the overlapped grid, with full states defined at every grid point, offers convenience to the imple- mentation of the boundary condition as well as the coupling of multi-physics.</span></p> ]]> Solution of Young–Laplace Equation with Finite-Volume Method and Overlapped Grid zeyi zhang liqiu wang doi: 10.2495/CMEM-V6-N1-11-22 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 11 10.2495/CMEM-V6-N1-11-22 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-11-22 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-1-10 Daltons and Amagats laws (also known as the law of partial pressures and the law of partial vol- umes respectively) are two well-known thermodynamic models describing gas mixtures. Our current research is focused on determining the suitability of these models in predicting effects of shock propa- gation through gas mixtures. Experiments are conducted at the Shock Tube Facility at the University of New Mexico (UNM). The gas mixture used in these experiments consists of approximately 50% sulfur hexafluoride (SF6) and 50% helium (He) by moles. Fast response pressure transducers are used to obtain pressure readings both before and after the shock wave; these data are then used to determine the velocity of the shock wave. Temperature readings are obtained using an ultra-fast mercury cadmium telluride (MCT) infrared (IR) detector, with a response time on the order of nanoseconds. Coupled with a stabilized broadband infrared light source (operating at 1500 K), the detector provides pre- and post- shock line-of-sight readings of average temperature within the shock tube, which are used to determine the speed of sound in the gas mixture. Paired with the velocity of the shock wave, this information allows us to determine the Mach number. These experimental results are compared with theoretical predictions of Daltons and Amagats laws to determine which one is more suitable. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Daltons and Amagats laws (also known as the law of partial pressures and the law of partial vol- umes respectively) are two well-known thermodynamic models describing gas mixtures. Our current research is focused on determining the suitability of these models in predicting effects of shock propa- gation through gas mixtures. Experiments are conducted at the Shock Tube Facility at the University of New Mexico (UNM). The gas mixture used in these experiments consists of approximately 50% sulfur hexafluoride (SF6) and 50% helium (He) by moles. Fast response pressure transducers are used to obtain pressure readings both before and after the shock wave; these data are then used to determine the velocity of the shock wave. Temperature readings are obtained using an ultra-fast mercury cadmium telluride (MCT) infrared (IR) detector, with a response time on the order of nanoseconds. Coupled with a stabilized broadband infrared light source (operating at 1500 K), the detector provides pre- and post- shock line-of-sight readings of average temperature within the shock tube, which are used to determine the speed of sound in the gas mixture. Paired with the velocity of the shock wave, this information allows us to determine the Mach number. These experimental results are compared with theoretical predictions of Daltons and Amagats laws to determine which one is more suitable.</span></p> ]]> Investigation of Dalton and Amagat’s Laws for Gas Mixtures with Shock Propagation patrick wayne sean cooper dylan simons ignacio trueba monje jae hwun yoo peter vorobieff c. randall truman sanjay kumar doi: 10.2495/CMEM-V6-N1-1-10 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 1 10.2495/CMEM-V6-N1-1-10 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-1-10 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-0 Multiphase flow occurs in a vast number of problems whose solutions are crucial both to our understanding of Nature and to our ability to successfully design and implement engineering processes. It usually involves a mixture in which gaseous, liquid and solid phases are present, often in conditions far from thermodynamic equilibrium. A common special case referred to as two-phase flow is characterized by the presence of only two phases of matter, e.g., liquid with solid particles or gas bubbles, or gas with solid particles or liquid droplets. Multiphase flow components can differ not only in continuum physical properties such as density or viscosity, but also in velocities and temperatures. A good example of multiphase flow with such temperature and velocity differences would be shock-accelerated gas seeded with solid particles. Phase transformations occurring within multiphase flows further complicate the picture and expand the range of relevant physical processes from that characterizing homogeneous single-phase flow. Interaction of solid and liquid particles with gas, their acceleration or deceleration, heating or cooling all lead to non-trivial aerodynamics on the particle scale. For liquid droplets, evaporation, breakup or coagulation are also important, which in turn affects the parameters of the gas phase. Initially evenly distributed inclusions in the carrier phase (particles in liquid or gas, drops in gas, or bubbles in liquid) can migrate between flow areas in accelerated or sheared flow. In the flow of gas with solid and liquid particles, as well as in vapor-liquid flows moving in channels, tubes, and nozzles of jet engines, particles can collide, fracture, and so on. In multiphase pipe flows, films can form on the walls, leading to deposition of droplets and particles on them, and resulting in complex heat exchange between the vapor, droplets and film. Solid or liquid particles can fall on the walls, settle on them or be reflected and re-enter the stream. During the interaction of particles with walls, erosion of the latter may also be important.In multiphase flow, a complex interaction of the phases takes place, accompanied by a variety of physical phenomena. Accordingly, processes of diffusion, viscous interaction, turbulence evolution, sound propagation, radiation, and shock propagation are substantially different in multiphase media and in the flow of homogeneous mixtures.A full description of a multiphase continuous medium uses the laws of conservation of mass, momentum and energy for each of the phases and the mixture as a whole, written in the integral or differential forms, using the concept of a multi-velocity continuum with interpenetrating motion of components. The multi-velocity continuum is a collection of N continua, each of which corresponds to its component of the mixture and fills the volume occupied by the mixture. For each of these constituent continua, density, velocity, and other parameters are determined in each flow. Then at each point of the volume occupied by the mixture, N densities, temperatures, and velocities must be determined. The complete description of the motion of a multiphase medium must also include thermal and caloric equations of state, making it possible to describe the stress tensor and internal energy through the remaining parameters of the mixture and some physicochemical constants. When solving specific problems, it is also necessary to use the relationships that determine the parameters of mass, force, and energetic interaction between the phases. Among such relationships are, for example, the relationships that allow us to determine the rate of condensation of the liquid phase, the drag forces on particles in the flow, the laws of coagulation and break-up of liquid particles, the rate of crystallization, and so on. The high quality of this publication is a reflection on the work carried out by the members of the Board and other colleagues who reviewed the contributions. The editors are especially indebted to them as well as to all authors for their excellent papers.The EditorsTallinn, Estonia2017 <![CDATA[ <p>Multiphase flow occurs in a vast number of problems whose solutions are crucial both to our understanding of Nature and to our ability to successfully design and implement engineering processes. It usually involves a mixture in which gaseous, liquid and solid phases are present, often in conditions far from thermodynamic equilibrium. A common special case referred to as two-phase flow is characterized by the presence of only two phases of matter, e.g., liquid with solid particles or gas bubbles, or gas with solid particles or liquid droplets. Multiphase flow components can differ not only in continuum physical properties such as density or viscosity, but also in velocities and temperatures. A good example of multiphase flow with such temperature and velocity differences would be shock-accelerated gas seeded with solid particles. Phase transformations occurring within multiphase flows further complicate the picture and expand the range of relevant physical processes from that characterizing homogeneous single-phase flow. Interaction of solid and liquid particles with gas, their acceleration or deceleration, heating or cooling all lead to non-trivial aerodynamics on the particle scale. For liquid droplets, evaporation, breakup or coagulation are also important, which in turn affects the parameters of the gas phase. Initially evenly distributed inclusions in the carrier phase (particles in liquid or gas, drops in gas, or bubbles in liquid) can migrate between flow areas in accelerated or sheared flow. In the flow of gas with solid and liquid particles, as well as in vapor-liquid flows moving in channels, tubes, and nozzles of jet engines, particles can collide, fracture, and so on. In multiphase pipe flows, films can form on the walls, leading to deposition of droplets and particles on them, and resulting in complex heat exchange between the vapor, droplets and film. Solid or liquid particles can fall on the walls, settle on them or be reflected and re-enter the stream. During the interaction of particles with walls, erosion of the latter may also be important.</p><p style="text-align: justify">In multiphase flow, a complex interaction of the phases takes place, accompanied by a variety of physical phenomena. Accordingly, processes of diffusion, viscous interaction, turbulence evolution, sound propagation, radiation, and shock propagation are substantially different in multiphase media and in the flow of homogeneous mixtures.</p><p style="text-align: justify">A full description of a multiphase continuous medium uses the laws of conservation of mass, momentum and energy for each of the phases and the mixture as a whole, written in the integral or differential forms, using the concept of a multi-velocity continuum with interpenetrating motion of components. The multi-velocity continuum is a collection of N continua, each of which corresponds to its component of the mixture and fills the volume occupied by the mixture. For each of these constituent continua, density, velocity, and other parameters are determined in each flow. Then at each point of the volume occupied by the mixture, N densities, temperatures, and velocities must be determined. The complete description of the motion of a multiphase medium must also include thermal and caloric equations of state, making it possible to describe the stress tensor and internal energy through the remaining parameters of the mixture and some physicochemical constants. When solving specific problems, it is also necessary to use the relationships that determine the parameters of mass, force, and energetic interaction between the phases. Among such relationships are, for example, the relationships that allow us to determine the rate of condensation of the liquid phase, the drag forces on particles in the flow, the laws of coagulation and break-up of liquid particles, the rate of crystallization, and so on. The high quality of this publication is a reflection on the work carried out by the members of the Board and other colleagues who reviewed the contributions. The editors are especially indebted to them as well as to all authors for their excellent papers.</p><p style="text-align: justify">The Editors</p><p style="text-align: justify">Tallinn, Estonia</p><p style="text-align: justify">2017</p> ]]> Preface peter vorobieff carlos a. brebbia doi: 10.2495/CMEM-V6-N1-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2018 6 1 Article 0 10.2495/CMEM-V6-N1-0 https://www.acadlore.com/article/IJCMEM/2018_6_1/CMEM-V6-N1-0 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-985-996 Throughout the centuries, nearly all signal buildings on the European continent have been built in masonry or concrete – in harsh, ‘stone-like’ materials. Norway differs remarkably from this main trend. We see that the European examples of stone architecture are largely reinterpreted in Norway as architecture in wood. The keywords are climate, economy, knowledge and tradition. Climate: Wood provides significantly better thermal insulation than brick, stone and concrete. Economy: With the exception of the last 50 years, Norway has been a poor country on the edge of Europe; therefore, there were rarely sufficient finances to build resource-intensive, magnificent buildings in stone or masonry. Knowledge and tradition: These factors are interrelated; tradition leads to knowledge and knowledge creates tradition. Norway has always had skilled carpenters, joiners and wood carvers from the Viking era until the present day. Despite poverty and distance, Norway was not an isolated and uninformed country; Norwegians have always been a seafaring people who grasped European impulses and style trends and brought them home. 10-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Throughout the centuries, nearly all signal buildings on the European continent have been built in masonry or concrete – in harsh, ‘stone-like’ materials. Norway differs remarkably from this main trend. We see that the European examples of stone architecture are largely reinterpreted in Norway as architecture in wood. The keywords are climate, economy, knowledge and tradition. Climate: Wood provides significantly better thermal insulation than brick, stone and concrete. Economy: With the exception of the last 50 years, Norway has been a poor country on the edge of Europe; therefore, there were rarely sufficient finances to build resource-intensive, magnificent buildings in stone or masonry. Knowledge and tradition: These factors are interrelated; tradition leads to knowledge and knowledge creates tradition. Norway has always had skilled carpenters, joiners and wood carvers from the Viking era until the present day. Despite poverty and distance, Norway was not an isolated and uninformed country; Norwegians have always been a seafaring people who grasped European impulses and style trends and brought them home.</span></p> ]]> From Stone to Norwegian Wood knut jonas espedal doi: 10.2495/CMEM-V5-N6-985-996 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 985 10.2495/CMEM-V5-N6-985-996 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-985-996 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-979-984 The Douglas is one of the most used species in France, especially in the Auvergne-Rhone Alpes Regions. This species found in unprotected outdoor environment is a major resource for the wood industry. However, variations in moisture content (MC), relative humidity (HR) and temperature (T) coupled with creep, can weaken its mechanical resistance. The main objective of this work is to study the mechanical behaviour of cracked wood beams under climate changes (T, HR and MC), the long-term loadings and the defects of wood (cracks, knots, orientation of annual rings etc). In this study, the evolutions of the crack length and the crack opening are presented. The results show the influence of climatic changes on the sustainability of timber structures of Douglas beams. 10-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The Douglas is one of the most used species in France, especially in the Auvergne-Rhone Alpes Regions. This species found in unprotected outdoor environment is a major resource for the wood industry. However, variations in moisture content (</span><em>MC</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">), relative humidity (</span><em>HR</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">) and temperature (</span><em>T</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">) coupled with creep, can weaken its mechanical resistance. The main objective of this work is to study the mechanical behaviour of cracked wood beams under climate changes (</span><em>T, HR </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">and </span><em>MC</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">), the long-term loadings and the defects of wood (cracks, knots, orientation of annual rings etc). In this study, the evolutions of the crack length and the crack opening are presented. The results show the influence of climatic changes on the sustainability of timber structures of Douglas beams.</span></p> ]]> Impacts of Climatic Changes and Creep Loadings on the Cracked Douglas (Pseudotsuga Menziesii) Timber Beam in Outdoor Conditions claude feldman pambou nziengui rostand moutou pitti eric fournely gaël godi doi: 10.2495/CMEM-V5-N6-979-984 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 979 10.2495/CMEM-V5-N6-979-984 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-979-984 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-966-978 The need to mitigate damage of buildings even after strong earthquakes has led to the development of high-performance seismic resisting systems. Extensive studies have been made in the last decade on the development and use of jointed ductile connections and on the effects of rocking vibration systems in reducing seismic damage of buildings. A recently developed technology for construction of multi-storey timber buildings called Pres-Lam system uses long lengths of prefabricated laminated timber and binds them together using pre-stressing steel tendons. When appropriately combining unbounded post-tensioned tendons, or rocking columns with additional sources of energy dissipation devices, a hybrid system is obtained, with self-centering and dissipative properties, leading to a characteristic flag-shape hysteresis behaviour.A three-dimensional, three-storey, two-third scaled, post-tensioned timber frame model was tested at the structural laboratory of the University of Basilicata. During shaking table tests, two different configurations of the test model have been studied considering column-table connections with and without the activation of dissipative steel angles. This paper focuses on different numerical modelling of the rocking mechanisms at the column-foundation connections. Two different modelling have been considered for two different test configurations by means of a pinned base or an appropriate combination of nonlinear rotational springs, for free rocking and a suitable combination of gap elements and linear springs or rotational springs, for dissipative rocking. The numerical outcomes of nonlinear dynamic analysis are compared with experimental test results providing an adequate representation of the seismic response. 10-31-2017 <![CDATA[ <p>The need to mitigate damage of buildings even after strong earthquakes has led to the development of high-performance seismic resisting systems. Extensive studies have been made in the last decade on the development and use of jointed ductile connections and on the effects of rocking vibration systems in reducing seismic damage of buildings. A recently developed technology for construction of multi-storey timber buildings called Pres-Lam system uses long lengths of prefabricated laminated timber and binds them together using pre-stressing steel tendons. When appropriately combining unbounded post-tensioned tendons, or rocking columns with additional sources of energy dissipation devices, a hybrid system is obtained, with self-centering and dissipative properties, leading to a characteristic flag-shape hysteresis behaviour.</p><p style="text-align: justify">A three-dimensional, three-storey, two-third scaled, post-tensioned timber frame model was tested at the structural laboratory of the University of Basilicata. During shaking table tests, two different configurations of the test model have been studied considering column-table connections with and without the activation of dissipative steel angles. This paper focuses on different numerical modelling of the rocking mechanisms at the column-foundation connections. Two different modelling have been considered for two different test configurations by means of a pinned base or an appropriate combination of nonlinear rotational springs, for free rocking and a suitable combination of gap elements and linear springs or rotational springs, for dissipative rocking. The numerical outcomes of nonlinear dynamic analysis are compared with experimental test results providing an adequate representation of the seismic response.</p> ]]> Modelling of Post-Tensioned Timber-Framed Buildings with Seismic Rocking Mechanism at the Column-Foundation Connections felice carlo ponzo antonio di cesare nicla lamarucciola domenico nigro stefano pampanin doi: 10.2495/CMEM-V5-N6-966-978 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 966 10.2495/CMEM-V5-N6-966-978 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-966-978 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-953-965 This work reports a summary of different type of analyses and modelling approaches, typically adopted by practitioners and researchers for the prediction of the seismic response of multi-storey CLT buildings. Specifically, two different modelling approaches are deeply investigated and compared; the first one is a component approach, which adopts springs (linear or non-linear) for connections, while the second one is based on a simplified phenomenological model where the behaviour of the system is reproduced by means of diagonal springs (linear or non-linear). The advantages and disadvantages of the two approaches are presented and critically discussed with reference to the types of the performed analysis (linear or non-linear).In order to verify the capability of the two modelling approaches to predict the seismic response of CLT structures performing linear analyses, a series of multi-storey buildings with increasing number of storeys and increasing values of design PGA are investigated. Obtained results are compared in terms of principal elastic periods, internal forces in the connection elements and drifts. Moreover, some correlations between results from the component and the phenomenological approach are given. Then, a first attempt of defining a numerical model suitable for non-linear analyses of a single CLT shear-wall, according to both the component and the phenomenological approaches is presented. Finally, the obtained results are discussed, highlighting the key issues in non-linear modelling of CLT structures. 10-31-2017 <![CDATA[ <p>This work reports a summary of different type of analyses and modelling approaches, typically adopted by practitioners and researchers for the prediction of the seismic response of multi-storey CLT buildings. Specifically, two different modelling approaches are deeply investigated and compared; the first one is a component approach, which adopts springs (linear or non-linear) for connections, while the second one is based on a simplified phenomenological model where the behaviour of the system is reproduced by means of diagonal springs (linear or non-linear). The advantages and disadvantages of the two approaches are presented and critically discussed with reference to the types of the performed analysis (linear or non-linear).</p><p style="text-align: justify">In order to verify the capability of the two modelling approaches to predict the seismic response of CLT structures performing linear analyses, a series of multi-storey buildings with increasing number of storeys and increasing values of design PGA are investigated. Obtained results are compared in terms of principal elastic periods, internal forces in the connection elements and drifts. Moreover, some correlations between results from the component and the phenomenological approach are given. Then, a first attempt of defining a numerical model suitable for non-linear analyses of a single CLT shear-wall, according to both the component and the phenomenological approaches is presented. Finally, the obtained results are discussed, highlighting the key issues in non-linear modelling of CLT structures.</p> ]]> Effect of Different Modelling Approaches on the Prediction of the Seismic Response of Multi-Storey CLT Buildings luca pozza marco savoia luca franco anna saetta diego talledo doi: 10.2495/CMEM-V5-N6-953-965 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 953 10.2495/CMEM-V5-N6-953-965 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-953-965 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-940-952 This work investigates the exploitation of a historical timber device used as masonry reinforcement in seismic prevention in the Mediterranean area. Such a technology is realized by means of a three-dimensional timber frame embedded in stone masonry in order to bind together the various structural parts, and contribute to the overall seismic resistance. Very often, such a constructive principle was extended not only to the weakest parts but to the whole building, creating new structural configurations that were able to absorb the effects of seismic ground motions. From Roman times (opus craticium), this system spread all across the Mediterranean area becoming common during the eighteenth century in Italy (Bourbon casa baraccata), in Portugal (Pombaline gaiola), in Turkey (hımış), etc. However, examples of timber devices and frameworks may be found almost worldwide: in the continental northern Europe, including those countries that are usually not subjected to earthquakes, as well as in Central Asia or in Japan, to America and North Africa. A large number of examples are reported to show how some traditional technologies, along with the suboptimal rules of the art, made a robust construction possible. Furthermore, by means of philological criterion and detailed analysis of seismic vulnerability improvement, the knowledge of such a system may allow developing novel designs and specific preservation works that could ensure the structural safety of historical constructions without modifying their main structural configuration. From such a perspective, this study examines the aspects of using diffused timber frameworks with masonry infill that go beyond anti-seismic technology, describes the common constructive features and helps develop guidelines for preservation of such systems. 10-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This work investigates the exploitation of a historical timber device used as masonry reinforcement in seismic prevention in the Mediterranean area. Such a technology is realized by means of a three-dimensional timber frame embedded in stone masonry in order to bind together the various structural parts, and contribute to the overall seismic resistance. Very often, such a constructive principle was extended not only to the weakest parts but to the whole building, creating new structural configurations that were able to absorb the effects of seismic ground motions. From Roman times (</span><em>opus craticium</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">), this system spread all across the Mediterranean area becoming common during the eighteenth century in Italy (Bourbon </span><em>casa baraccata</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">), in Portugal (Pombaline </span><em>gaiola</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">), in Turkey (</span><em>hımış)</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">, etc. However, examples of timber devices and frameworks may be found almost worldwide: in the continental northern Europe, including those countries that are usually not subjected to earthquakes, as well as in Central Asia or in Japan, to America and North Africa. A large number of examples are reported to show how some traditional technologies, along with the suboptimal rules of the art, made a robust construction possible. Furthermore, by means of philological criterion and detailed analysis of seismic vulnerability improvement, the knowledge of such a system may allow developing novel designs and specific preservation works that could ensure the structural safety of historical constructions without modifying their main structural configuration. From such a perspective, this study examines the aspects of using diffused timber frameworks with masonry infill that go beyond anti-seismic technology, describes the common constructive features and helps develop guidelines for preservation of such systems.</span></p> ]]> Timber Anti-Seismic Devices in Historical Architecture in the Mediterranean Area tiziana campisi manfredi saeli doi: 10.2495/CMEM-V5-N6-940-952 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 940 10.2495/CMEM-V5-N6-940-952 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-940-952 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-928-939 As a natural raw material timber shows indisputable environmental excellence and certainly represents one of the best choices for sustainable construction. The use of glazing in buildings has always contributed to openness, visual comfort and better daylight situation. The features of the both building materials lead to the development of a new type of highly attractive structures, the so-called timber–glass buildings. However, in a view to maximising the use of natural solar radiation gains, the most of the glazing is usually placed in the south facade of such buildings, which can lead to many structural problems, especially when the building is exposed to heavy horizontal loads. In such cases it is usu- ally to assure a horizontal stability by using additional visible diagonal elements or by internal wall elements. In this study we are presenting another solution by using timber-frame wall elements with fixed insulating glazing placed on the external side of the timber frame where the glass pane is consid- ered as a load-bearing element. It is presented that such timber–glass load-bearing wall element can significantly contribute to the overall horizontal resistance of the whole building. The behaviour of load-bearing timber–glass wall elements is additionally modelled with FE model where the bonding line is modelled with spring elements. With such developed mathematical model it is possible further parametrically to analyse many various parameters which significantly influence on the capacity, stiff- ness and failure mechanism of such composite elements. 10-31-2017 <![CDATA[ <p><span style="font-family: Times New Roman, serif">As a natural raw material timber shows indisputable environmental excellence and certainly represents one of the best choices for sustainable construction. The use of glazing in buildings has always contributed to openness, visual comfort and better daylight situation. The features of the both building materials lead to the development of a new type of highly attractive structures, the so-called timber–glass buildings. However, in a view to maximising the use of natural solar radiation gains, the most of the glazing is usually placed in the south facade of such buildings, which can lead to many structural problems, especially when the building is exposed to heavy horizontal loads. In such cases it is usu- ally to assure a horizontal stability by using additional visible diagonal elements or by internal wall elements. In this study we are presenting another solution by using timber-frame wall elements with fixed insulating glazing placed on the external side of the timber frame where the glass pane is consid- ered as a load-bearing element. It is presented that such timber–glass load-bearing wall element can significantly contribute to the overall horizontal resistance of the whole building. The behaviour of load-bearing timber–glass wall elements is additionally modelled with FE model where the bonding line is modelled with spring elements. With such developed mathematical model it is possible further parametrically to analyse many various parameters which significantly influence on the capacity, stiff- ness and failure mechanism of such composite elements.</span></p> ]]> Cyclic and Shaking-Table Tests of Timber–Glass Buildings miroslav premrov boštjan ber andrej štrukelj doi: 10.2495/CMEM-V5-N6-928-939 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 928 10.2495/CMEM-V5-N6-928-939 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-928-939 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-917-927 In the field of timber engineering, adhesive bonding remains a promising, though poorly developed, joining technique that may increase the structural stiffness and capacity of timber joints and structures. Selecting ductile adhesives may further allow to conceive ductile joints, which can compensate for the missing material ductility of timber. To demonstrate the potential of this approach, adhesively bonded double-lap timber joints were manufactured using a ductile acrylic adhesive and then subjected to axial tension and compression. The load–displacement responses were captured and compared to those of the same joints composed of a brittle epoxy adhesive. The effect of the different adhesives on the joint ductility has been studied and quantified. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">In the field of timber engineering, adhesive bonding remains a promising, though poorly developed, joining technique that may increase the structural stiffness and capacity of timber joints and structures. Selecting ductile adhesives may further allow to conceive ductile joints, which can compensate for the missing material ductility of timber. To demonstrate the potential of this approach, adhesively bonded double-lap timber joints were manufactured using a ductile acrylic adhesive and then subjected to axial tension and compression. The load–displacement responses were captured and compared to those of the same joints composed of a brittle epoxy adhesive. The effect of the different adhesives on the joint ductility has been studied and quantified.</span></p> ]]> Ductility of Adhesively Bonded Timber Joints m. angelidi a. p. vassilopoulos t. keller doi: 10.2495/CMEM-V5-N6-917-927 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 917 10.2495/CMEM-V5-N6-917-927 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-917-927 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-905-916 Massive timber plate elements, specifically cross laminated timber (CLT), has gained popularity recently in North America as major alternative construction material for building components offering competitive advantages relative to traditional reinforced concrete slab for medium rise applications. There are two major structural applications for this kind of timber plate, as floor slab or shear wall components of multi-storey buildings. The following study will be focused on the structural performance of hybrid multi-storey buildings constructed using CLT plate as the floor slab elements. The specific objective of this paper is to investigate lateral deformability of floor diaphragm that is composed of CLT slab in combination with reinforced concrete and steel floor framing loaded under seismic excitation. Critical irregular floor layouts of medium rise buildings are selected and modeled using computer structural and building analysis software ETABS. Major outputs including lateral floor deformation (drift), storey shear and dynamic characteristic analyses are analyzed and contrasted with the current design practices, i.e. building code application with respect to diaphragm assumption for seismic design. As in the reinforced concrete-based floor diaphragm, expected general outcome from this study is to provide input for design code provision regarding whether rigid, flexible, or in-between (semi-rigid) assumption of CLT-based diaphragm is adequate for performing design standard procedure for seismic design of hybrid multi-storey buildings. Structural analysis and modeling challenges for CLT-based diaphragm used in hybrid multi-storey buildings are presented and design recommendations will be given. 10-31-2017 <![CDATA[ <p>Massive timber plate elements, s<span style="color: black; font-family: Times New Roman, serif">pecifically cross laminated timber (CLT), has gained popularity recently in North America as major alternative construction material for building components offering competitive advantages relative to traditional reinforced concrete slab for medium rise applications. There are two major structural applications for this kind of timber plate, as floor slab or shear wall components of multi-storey buildings. The following study will be focused on the structural performance of hybrid multi-storey buildings constructed using CLT plate as the floor slab elements. The specific objective of this paper is to investigate lateral deformability of floor diaphragm that is composed of CLT slab in combination with reinforced concrete and steel floor framing loaded under seismic excitation. Critical irregular floor layouts of medium rise buildings are selected and modeled using computer structural and building analysis software ETABS. Major outputs including lateral floor deformation (drift), storey shear and dynamic characteristic analyses are analyzed and contrasted with the current design practices, i.e. building code application with respect to diaphragm assumption for seismic design. As in the reinforced concrete-based floor diaphragm, expected general outcome from this study is to provide input for design code provision regarding whether rigid, flexible, or in-between (semi-rigid) assumption of CLT-based diaphragm is adequate for performing design standard procedure for seismic design of hybrid multi-storey buildings. Structural analysis and modeling challenges for CLT-based diaphragm used in hybrid multi-storey buildings are presented and design recommendations will be given.</span></p> ]]> Structural Performance of Hybrid Multi-Storey Buildings with Massive Timber-Based Floor Elements Loaded Under Extreme Lateral Loads danish ahmed andi asiz doi: 10.2495/CMEM-V5-N6-905-916 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 905 10.2495/CMEM-V5-N6-905-916 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-905-916 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-894-904 Wood is referred to as a material but in the true material sciences definition, a material is uniform, predictable, continuous, and reproducible. No two pieces of wood are the same even if they came from the same tree and the same board. Wood is better described as a composite and, more accurately, as a porous three-dimensional, hydroscopic, viscoelastic, anisotropic bio-polymer composite composed of an interconnecting matrix of cellulose, hemicelluloses, and lignin with minor amounts of inorganic elements and organic extractives. So, even solid wood is a composite. The characteristics we deal with at the solid wood level (swelling/shrinking, biological attack, and strength) are derived from the properties at the cell wall matrix and polymer level. Moisture sorption and desorption in the cell wall polymers results in dimensional instability and changing mechanical properties. Many different types of microorganisms recognize wood as a food source and are able to break it down resulting in both weight and strength losses. One technology that has now been commercialized to achieve high levels of stability, durability, and improved wet mechanical properties is acetylation: a reaction between the hydroxyl groups in the wood cell wall polymers and acetic anhydride. While all woods contain a low level of acetyl groups, increasing this acetyl content changes the properties and, thereby, the performance of the reacted wood. When a substantial number of the accessible hydroxyl groups are acetylated consistently across the entire cell wall, the wood reaches its highest level of stability and durability. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">Wood is referred to as a material but in the true material sciences definition, a material is uniform, predictable, continuous, and reproducible. No two pieces of wood are the same even if they came from the same tree and the same board. Wood is better described as a composite and, more accurately, as a porous three-dimensional, hydroscopic, viscoelastic, anisotropic bio-polymer composite composed of an interconnecting matrix of cellulose, hemicelluloses, and lignin with minor amounts of inorganic elements and organic extractives. So, even solid wood is a composite. The characteristics we deal with at the solid wood level (swelling/shrinking, biological attack, and strength) are derived from the properties at the cell wall matrix and polymer level. Moisture sorption and desorption in the cell wall polymers results in dimensional instability and changing mechanical properties. Many different types of microorganisms recognize wood as a food source and are able to break it down resulting in both weight and strength losses. One technology that has now been commercialized to achieve high levels of stability, durability, and improved wet mechanical properties is acetylation: a reaction between the hydroxyl groups in the wood cell wall polymers and acetic anhydride. While all woods contain a low level of acetyl groups, increasing this acetyl content changes the properties and, thereby, the performance of the reacted wood. When a substantial number of the accessible hydroxyl groups are acetylated consistently across the entire cell wall, the wood reaches its highest level of stability and durability.</span></p> ]]> Stable and Durable Wood Building Materials Based on Molecular Level Chemical Modification roger m. rowell doi: 10.2495/CMEM-V5-N6-894-904 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 894 10.2495/CMEM-V5-N6-894-904 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-894-904 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-884-893 Laminated timber-concrete (LTC) and steel-timber-concrete composite beam (S-LTC) members with adhesive interlayer connections were experimentally investigated. This paper presents the results of the acoustic emission (AE) investigation performed during short-term static ramp-loading to failure tests. The beam specimens were continuously monitored using accelerometers connected to a four channel dynamic signal analyzer. For LTC beams, the failure of the timber in tension was typically observed; therefore, a steel layer was added to the tension side of the timber layer to increase the strength and to induce a ductile behaviour. The results of the AE investigations on two LTC and two S-LTC specimens reveal the progression of the failure as it initiates and gradually develops within the beams, leading to the tension failure and shear failure modes for the LTC and S-LTC specimens, respectively. The results confirm that the fast Fourier transformation (FFT) and waterfall type of spectral analysis have an important role in supplying substantial and reliable amounts of information for the identification of different phenomena in connection with the failure process of the investigated structural members. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">Laminated timber-concrete (LTC) and steel-timber-concrete composite beam (S-LTC) members with adhesive interlayer connections were experimentally investigated. This paper presents the results of the acoustic emission (AE) investigation performed during short-term static ramp-loading to failure tests. The beam specimens were continuously monitored using accelerometers connected to a four channel dynamic signal analyzer. For LTC beams, the failure of the timber in tension was typically observed; therefore, a steel layer was added to the tension side of the timber layer to increase the strength and to induce a ductile behaviour. The results of the AE investigations on two LTC and two S-LTC specimens reveal the progression of the failure as it initiates and gradually develops within the beams, leading to the tension failure and shear failure modes for the LTC and S-LTC specimens, respectively. The results confirm that the fast Fourier transformation (FFT) and waterfall type of spectral analysis have an important role in supplying substantial and reliable amounts of information for the identification of different phenomena in connection with the failure process of the investigated structural members.</span></p> ]]> Acoustic Emission Investigation Of Laminated Timber-Concrete Test Beams istván szűcs jeno balogh rose holtzman doi: 10.2495/CMEM-V5-N6-884-893 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 884 10.2495/CMEM-V5-N6-884-893 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-884-893 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-872-883 This paper presents an innovative lateral load-resisting wall system, which is an evolution of the light-timber frame (LTF) shear walls currently available on the market. In comparison to traditional LTF walls, the novelty aspect is the use of cross-laminated timber (CLT) beams and studs instead of solid timber elements. Thanks to this ‘hybrid’ approach, this new system combines some peculiar aspects of LTF structures (such as the limited weight and the high dissipative behaviour) with the potentials of CLT. Moreover, the use of CLT elements limits the issues due to the compressive deformations on bottom beams and permits to employ some innovative connections with high mechanical properties. Cyclic shear tests are carried out on two configurations of interest, assembled by considering different layouts of the load-bearing elements. Test results are compared to the experimental data obtained on similar LTF systems and differences are critically discussed. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">This paper presents an innovative lateral load-resisting wall system, which is an evolution of the light-timber frame (LTF) shear walls currently available on the market. In comparison to traditional LTF walls, the novelty aspect is the use of cross-laminated timber (CLT) beams and studs instead of solid timber elements. Thanks to this ‘hybrid’ approach, this new system combines some peculiar aspects of LTF structures (such as the limited weight and the high dissipative behaviour) with the potentials of CLT. Moreover, the use of CLT elements limits the issues due to the compressive deformations on bottom beams and permits to employ some innovative connections with high mechanical properties. Cyclic shear tests are carried out on two configurations of interest, assembled by considering different layouts of the load-bearing elements. Test results are compared to the experimental data obtained on similar LTF systems and differences are critically discussed.</span></p> ]]> Experimental Tests on a Hybrid Timber-Frame Wall System m. izzi d. casagrande e. sinito g. pasetto a. polastri doi: 10.2495/CMEM-V5-N6-872-883 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 872 10.2495/CMEM-V5-N6-872-883 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-872-883 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-858-871 Infrared is a part of electromagnetic spectrum not visible for the human eye, but contain important information regarding material status. Several scientific methods have been developed during years to acquire, analyse and interpret the infrared radiation in active and passive way. The technology become especially interesting nowadays when infrared measuring instruments become portable and affordable, being reasonably accurate at the same time. This research summarizes some possibilities of implementing modern instruments available on the market but also presents prototype solutions developed for the research needs in the laboratory. Near- and mid-infrared spectroscopies as well as hyperspectral and thermal imaging in different configurations are briefly described with a special focus on the specific application in assessment of timber structures. Advantages for implementation but also limiting factors for each technology are listed and discussed. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">Infrared is a part of electromagnetic spectrum not visible for the human eye, but contain important information regarding material status. Several scientific methods have been developed during years to acquire, analyse and interpret the infrared radiation in active and passive way. The technology become especially interesting nowadays when infrared measuring instruments become portable and affordable, being reasonably accurate at the same time. This research summarizes some possibilities of implementing modern instruments available on the market but also presents prototype solutions developed for the research needs in the laboratory. Near- and mid-infrared spectroscopies as well as hyperspectral and thermal imaging in different configurations are briefly described with a special focus on the specific application in assessment of timber structures. Advantages for implementation but also limiting factors for each technology are listed and discussed.</span></p> ]]> Using Various Infrared Techniques for Assessing Timber Structures jakub sandak anna sandak doi: 10.2495/CMEM-V5-N6-858-871 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 858 10.2495/CMEM-V5-N6-858-871 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-858-871 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-847-857 The resistance to horizontal loads provided by timber constructions is determined by the racking resistance of the timber frame walls within the structure. In Eurocode 5 (EN 1995-1-1), two methods are described to assess the racking resistance of these structural elements. Method A refers to a mechanical model while method B is empirically based and therefore less attractive. When using method A, full anchorage of the leading stud is needed. Moreover, contributions of wall panels with openings are neglected in the assessment of the racking resistance. In this paper, an experimental campaign studying the racking resistance of partially anchored walls with different wall and loading configurations is presented. The study shows that window and door openings lead to a reduction of the racking resistance of the wall depending on the size of the opening. Additionally, a comparison between the experimental data and several design methods for the assessment of the racking resistance of the wall panels is made. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">The resistance to horizontal loads provided by timber constructions is determined by the racking resistance of the timber frame walls within the structure. In Eurocode 5 (EN 1995-1-1), two methods are described to assess the racking resistance of these structural elements. Method A refers to a mechanical model while method B is empirically based and therefore less attractive. When using method A, full anchorage of the leading stud is needed. Moreover, contributions of wall panels with openings are neglected in the assessment of the racking resistance. In this paper, an experimental campaign studying the racking resistance of partially anchored walls with different wall and loading configurations is presented. The study shows that window and door openings lead to a reduction of the racking resistance of the wall depending on the size of the opening. Additionally, a comparison between the experimental data and several design methods for the assessment of the racking resistance of the wall panels is made.</span></p> ]]> Experimental And Analytical Assessment of Racking Resistance of Partially Anchored Timber Frame Walls r. steensels k. de proft b. vandoren doi: 10.2495/CMEM-V5-N6-847-857 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 847 10.2495/CMEM-V5-N6-847-857 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-847-857 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-834-846 Over the last few years, Cross-Laminated Timber (CLT) panels have become increasingly popular in many structural applications. The growth in CLT uptake by the construction sector is likely to continue in line with the pressing need for sustainable construction. Although current design methods exist for CLT, often these have limits of applicability. In order to gain upmost efficiency, there is a need for improved analytical methods to fully determine the structural behaviour of CLT. In this article, CLT panels will be investigated as a novel application of the State Space Approach (SSA). As CLT is a laminated composite panel, the 3D analytical approach provided by the SSA is highly applicable. Comparison with existing experimental results for different CLT panels are explored for simply supported orthotropic CLT panels under different types of loading. The effect of the plate thickness on displacements and stresses is described quantitatively. The results demonstrate the capability of the SSA method to capture the nonlinear distribution of the stresses through the depth of the plates over a range of thicknesses, thus offering an improved understanding of CLT structural behaviour. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">Over the last few years, Cross-Laminated Timber (CLT) panels have become increasingly popular in many structural applications. The growth in CLT uptake by the construction sector is likely to continue in line with the pressing need for sustainable construction. Although current design methods exist for CLT, often these have limits of applicability. In order to gain upmost efficiency, there is a need for improved analytical methods to fully determine the structural behaviour of CLT. In this article, CLT panels will be investigated as a novel application of the State Space Approach (SSA). As CLT is a laminated composite panel, the 3D analytical approach provided by the SSA is highly applicable. Comparison with existing experimental results for different CLT panels are explored for simply supported orthotropic CLT panels under different types of loading. The effect of the plate thickness on displacements and stresses is described quantitatively. The results demonstrate the capability of the SSA method to capture the nonlinear distribution of the stresses through the depth of the plates over a range of thicknesses, thus offering an improved understanding of CLT structural behaviour.</span></p> ]]> Structural Behaviour of Cross-Laminated Timber Panels by the State Space Approach asad s. albostami zhangjian wu lee s. cunningham doi: 10.2495/CMEM-V5-N6-834-846 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 834 10.2495/CMEM-V5-N6-834-846 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-834-846 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-821-833 A 3D Finite Element (FE) model has been developed, which accounted the geometric nonlinearity of flange and web portions of I-beams. The nonlinear FE model was reviewed against tests on castellated timber beams having a web with hexagonal holes. Load carrying capacity, load-deflection responses and failure modes for castellated beams in flexure were predicted and compared to the experimental results. An additional parametric study involving two different web opening shapes (circular and rectangular) was performed using the presented FE model to study the effects of the change of shapes of holes in web portions on the strength and buckling behaviour of castellated beams in bending. The parametric study has shown that castellated timber beams failing due to web-post buckling modes exhibited a strong decrease in the initial load capacity. 10-31-2017 <![CDATA[ <p><span style="color: black; font-family: Times New Roman, serif">A 3D Finite Element (FE) model has been developed, which accounted the geometric nonlinearity of flange and web portions of I-beams. The nonlinear FE model was reviewed against tests on castellated timber beams having a web with hexagonal holes. Load carrying capacity, load-deflection responses and failure modes for castellated beams in flexure were predicted and compared to the experimental results. An additional parametric study involving two different web opening shapes (circular and rectangular) was performed using the presented FE model to study the effects of the change of shapes of holes in web portions on the strength and buckling behaviour of castellated beams in bending. The parametric study has shown that castellated timber beams failing due to web-post buckling modes exhibited a strong decrease in the initial load capacity.</span></p> ]]> Modelling of Timber I-Beams in Bending m. li v.d. thi m. khelifa m. el ganaoui doi: 10.2495/CMEM-V5-N6-821-833 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 821 10.2495/CMEM-V5-N6-821-833 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-821-833 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-807-820 Timber–concrete composite structures are often used as floor solutions in new and existing buildings to combine better acoustic separation and improved thermal insulation with increased stiffness and greater load-carrying capacity. The choice of a structurally effective yet cheap shear connection between the concrete topping and the timber joist is crucial to make the composite floor a viable solution that can compete with reinforced concrete and steel structures. The use of inclined screws is a possible option to maximize the slip modulus of the connection and, at the same time, keep the construction cost within acceptable values. In this paper, the results from an experimental and numerical investigation carried out on such a type of shear connection are reported. Push-out tests were carried out at the Laboratory of the Department of Civil, Building and Environmental Engineering of the University of L’Aquila. Each specimen consisted of a timber block connected to two concrete slabs by means of two 8 mm diameter screws per side produced by Rotho Blaas. A layer of OSB was interposed to reproduce the timber flooring often used as permanent formwork for the placement of the concrete slab in new floors or the existing timber flooring when strengthening existing timber structures. Two different screw lengths and interlayer thicknesses were investigated. For each configuration, 10 push-out specimens were tested. The results were statistically assessed by computing the mean slip moduli and the characteristic values of the shear strength. Numerical simulations were also carried out to investigate the dependency of the slip modulus upon the screw inclination and the interlayer flooring thickness. 10-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Timber–concrete composite structures are often used as floor solutions in new and existing buildings to combine better acoustic separation and improved thermal insulation with increased stiffness and greater load-carrying capacity. The choice of a structurally effective yet cheap shear connection between the concrete topping and the timber joist is crucial to make the composite floor a viable solution that can compete with reinforced concrete and steel structures. The use of inclined screws is a possible option to maximize the slip modulus of the connection and, at the same time, keep the construction cost within acceptable values. In this paper, the results from an experimental and numerical investigation carried out on such a type of shear connection are reported. Push-out tests were carried out at the Laboratory of the Department of Civil, Building and Environmental Engineering of the University of L’Aquila. Each specimen consisted of a timber block connected to two concrete slabs by means of two 8 mm diameter screws per side produced by Rotho Blaas. A layer of OSB was interposed to reproduce the timber flooring often used as permanent formwork for the placement of the concrete slab in new floors or the existing timber flooring when strengthening existing timber structures. Two different screw lengths and interlayer thicknesses were investigated. For each configuration, 10 push-out specimens were tested. The results were statistically assessed by computing the mean slip moduli and the characteristic values of the shear strength. Numerical simulations were also carried out to investigate the dependency of the slip modulus upon the screw inclination and the interlayer flooring thickness.</span></p> ]]> Mechanical Behavior of Timber–Concrete Connections with Inclined Screws beatrice berardinucci simona di nino amedeo gregori massimo fragiacomo doi: 10.2495/CMEM-V5-N6-807-820 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 807 10.2495/CMEM-V5-N6-807-820 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-807-820 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-797-806 Panels protect timber elements in timber frame assemblies during fire. The influence of the panels can be incorporated into calculations according to EN 1995-1-2, Annex C [1]. The number of panels incorporated in this standard is limited. Moreover, the calculations performed according to this standard result in overestimation of the charred area. In this work, experimental analysis of the protective behaviour was performed. Small-scale fire tests were used to monitor the temperature inside the timber element and the timber frame assembly. The measured results are compared with calculations according to the standard. 10-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Panels protect timber elements in timber frame assemblies during fire. The influence of the panels can be incorporated into calculations according to EN 1995-1-2, Annex C [1]. The number of panels incorporated in this standard is limited. Moreover, the calculations performed according to this standard result in overestimation of the charred area. In this work, experimental analysis of the protective behaviour was performed. Small-scale fire tests were used to monitor the temperature inside the timber element and the timber frame assembly. The measured results are compared with calculations according to the standard.</span></p> ]]> Effects of Protective Panels on Charring of Timber Elements in Timber Frame Assemblies k. de proft r. steensels b. van doren doi: 10.2495/CMEM-V5-N6-797-806 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 797 10.2495/CMEM-V5-N6-797-806 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-797-806 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-0-0 This issue contains a number of state of the art contributions on Timber Structures and Engineering. They are written by scientists, architects and engineers interested in promoting the use of timber as a construction material. In fact, when trying to find a reliable timber engineering solution, the designers of structural elements are facing a major challenge, i.e. although timber is one of the most widely used materials in the world, it lacks the reliability of stone, concrete and other materials. Indeed, it is easy to understand why the Eurocodes only accept its use under simple uni-axial load conditions, in view of its anisotropy, heterogeneity and many other imperfections. Timber has been regarded in the past as an unreliable material. Its main advantage was its local availability, which made its use easy and economical. However, a major structural engineering revolution took place in the XXth Century. It was the emergence of composites, for which synergy between different materials offers a reliable and strong structural solution. One thus discovers the advantages of “composite materials solutions” in combination with more mechanically reliable materials, plus others that offer thermal, acoustic, insulation, fire resistance, anti seismic behaviour, and other properties. Timber has gained credibility in structural applications despite its incertitudes in mechanical properties and its limited possibilities in the case of traction structural joints or multi-axial states of stress. It is also a beautiful material, which can be used for a multitude of complex structural forms which has led to its ever-increasing use in the modern built environment. 10-31-2017 <![CDATA[ <p>This issue contains a number of state of the art contributions on Timber Structures and Engineering. They are written by scientists, architects and engineers interested in promoting the use of timber as a construction material.</p><p> In fact, when trying to find a reliable timber engineering solution, the designers of structural elements are facing a major challenge, i.e. although timber is one of the most widely used materials in the world, it lacks the reliability of stone, concrete and other materials. Indeed, it is easy to understand why the Eurocodes only accept its use under simple uni-axial load conditions, in view of its anisotropy, heterogeneity and many other imperfections. </p><p>Timber has been regarded in the past as an unreliable material. Its main advantage was its local availability, which made its use easy and economical. </p><p>However, a major structural engineering revolution took place in the XXth Century. It was the emergence of composites, for which synergy between different materials offers a reliable and strong structural solution. One thus discovers the advantages of “composite materials solutions” in combination with more mechanically reliable materials, plus others that offer thermal, acoustic, insulation, fire resistance, anti seismic behaviour, and other properties. </p><p>Timber has gained credibility in structural applications despite its incertitudes in mechanical properties and its limited possibilities in the case of traction structural joints or multi-axial states of stress. It is also a beautiful material, which can be used for a multitude of complex structural forms which has led to its ever-increasing use in the modern built environment.</p> ]]> Preface doi: 10.2495/CMEM-V5-N6-0-0 International Journal of Computational Methods and Experimental Measurements 10-31-2017 International Journal of Computational Methods and Experimental Measurements 10-31-2017 2017 5 6 Article 1 10.2495/CMEM-V5-N6-0-0 https://www.acadlore.com/article/IJCMEM/2017_5_6/CMEM-V5-N6-0-0 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-771-779 In the 1960s, coinciding with the massive demand for credit cards, financial companies needed a method to know their exposure to risk insolvency. It began applying credit-scoring techniques. In the 1980s credit-scoring techniques were extended to loans due to the increased demand for credit and computational progress. In 2004, new recommendations of the Basel Committee (as called Basel II) on banking supervision appeared. With the ensuing global financial crisis, a new document, Basel III, appeared. It introduced more demanding changes on the control of borrowed capital.Nowadays, one of the main problems not addressed is the presence of large datasets. This research is focused on calculating probabilities of default in home equity loans, and measuring the computational efficiency of some statistical and data mining methods. In order to do these, some Monte Carlo experiments with known techniques and algorithms have been developed.These computational experiments reveal that large datasets need BigData techniques and algorithms that yield faster and unbiased estimators. 08-31-2017 <![CDATA[ <p>In the 1960s, coinciding with the massive demand for credit cards, financial companies needed a method to know their exposure to risk insolvency. It began applying credit-scoring techniques. In the 1980s credit-scoring techniques were extended to loans due to the increased demand for credit and computational progress. In 2004, new recommendations of the Basel Committee (as called Basel II) on banking supervision appeared. With the ensuing global financial crisis, a new document, Basel III, appeared. It introduced more demanding changes on the control of borrowed capital.</p><p style="text-align: justify">Nowadays, one of the main problems not addressed is the presence of large datasets. This research is focused on calculating probabilities of default in home equity loans, and measuring the computational efficiency of some statistical and data mining methods. In order to do these, some Monte Carlo experiments with known techniques and algorithms have been developed.</p><p style="text-align: justify">These computational experiments reveal that large datasets need BigData techniques and algorithms that yield faster and unbiased estimators.</p> ]]> Computational Experiment to Compare Techniques in Large Datasets to Measure Credit Banking Risk in Home Equity Loans a. pérez-martín m. vaca doi: 10.2495/CMEM-V5-N5-771-779 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 771 10.2495/CMEM-V5-N5-771-779 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-771-779 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-760-770 Using oil-spill booms as floating barriers must respect environmental conditions, mechanical limitations and operational constraints. Numerical modelling of boom behaviour can be used in order to prepare or validate booming plans, which respect these constraints. We present simulations of boom behaviour during an exercise in Galicia to support existing contingency plans. The main inputs of the modelled simulations are: environmental data on meteorology and oceanography, pollution field data and technical specifications of commercially available booms. The barrier structural analysis uses four-step modelling with an adaptive geometry. Modelled results are used in two ways. Firstly, a pre-paredness approach is conducted with a three-section boom plan to protect a mussel farm near the Puebla del Caramiñal. Secondly, a post-experiment analysis is made with a four-section plan and time- dependant boundary conditions given by the five GPS buoys position records carried out during the experiment. This numerical validation of the boom plan is complementary to the operational training of the boom deployment. The model results reproduce the barriers’ behaviour during the exercise and improve contingency planning for future response. The proposed approach has been generalized to other environments such as estuaries, ports and lakes. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Using oil-spill booms as floating barriers must respect environmental conditions, mechanical limitations and operational constraints. Numerical modelling of boom behaviour can be used in order to prepare or validate booming plans, which respect these constraints. We present simulations of boom behaviour during an exercise in Galicia to support existing contingency plans. The main inputs of the modelled simulations are: environmental data on meteorology and oceanography, pollution field data and technical specifications of commercially available booms. The barrier structural analysis uses four-step modelling with an adaptive geometry. Modelled results are used in two ways. Firstly, a pre-paredness approach is conducted with a three-section boom plan to protect a mussel farm near the Puebla del Caramiñal. Secondly, a post-experiment analysis is made with a four-section plan and time- dependant boundary conditions given by the five GPS buoys position records carried out during the experiment. This numerical validation of the boom plan is complementary to the operational training of the boom deployment. The model results reproduce the barriers’ behaviour during the exercise and improve contingency planning for future response. The proposed approach has been generalized to other environments such as estuaries, ports and lakes.</span></p> ]]> Numerical Modelling and Full-Scale Exercise of Oil-Spill Containment Boom on Galician Coast f. muttin r. campbell a. ouansafi y. benelmostafa doi: 10.2495/CMEM-V5-N5-760-770 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 760 10.2495/CMEM-V5-N5-760-770 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-760-770 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-750-759 The depth of closure of the beach profile, from now on termed as DoC, is a key parameter to perform effective evaluations of beach nourishments or coastal defence works. It is defined for a given time interval, as the closest depth to the shore at which there is no significant change in seabed elevation and no significant net sediment transport between the nearshore and offshore. To obtain this point it is necessary to compare profile surveys at a given period of time, and evaluate them to find the point in the profile where the depth variation is equal to, or less than, a pre-selected criteria. In order to manage all this information, a software application has been developed. On providing the input of the beach profiles, this tool offers the possibility of selecting the dates of the desired period of study, graph the profiles and then obtain, for each XY coordinate, all the required parameters, such as offshore distance, maximum, average and minimum depth, standard deviation and area difference between profiles. By evaluating each point along the profile, the DoC can be obtained at that point that meets the criteria. Moreover, this tool allows to graph not only the initial and final profile of the period, but all the beach profiles recorded, creating its maximum and minimum envelope. In addition, if the user introduces the parameters related to the equilibrium beach profile, this tool also corrects the area difference, taking into account the morphological changes (erosion– accretion) that may have occurred during the period studied. In conclusion, this tool has a friendly interface for obtaining the DoC with accuracy by interactive selection of the period of study. It also stores all the information and exports it to different formats. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The depth of closure of the beach profile, from now on termed as DoC, is a key parameter to perform effective evaluations of beach nourishments or coastal defence works. It is defined for a given time interval, as the closest depth to the shore at which there is no significant change in seabed elevation and no significant net sediment transport between the nearshore and offshore. To obtain this point it is necessary to compare profile surveys at a given period of time, and evaluate them to find the point in the profile where the depth variation is equal to, or less than, a pre-selected criteria. In order to manage all this information, a software application has been developed. On providing the input of the beach profiles, this tool offers the possibility of selecting the dates of the desired period of study, graph the profiles and then obtain, for each XY coordinate, all the required parameters, such as offshore distance, maximum, average and minimum depth, standard deviation and area difference between profiles. By evaluating each point along the profile, the DoC can be obtained at that point that meets the criteria. Moreover, this tool allows to graph not only the initial and final profile of the period, but all the beach profiles recorded, creating its maximum and minimum envelope. In addition, if the user introduces the parameters related to the equilibrium beach profile, this tool also corrects the area difference, taking into account the morphological changes (erosion– accretion) that may have occurred during the period studied. In conclusion, this tool has a friendly interface for obtaining the DoC with accuracy by interactive selection of the period of study. It also stores all the information and exports it to different formats.</span></p> ]]> A Software Application to Obtain the Depth of Closure from Beach Profile Data j.i. pagán y. villacampa l. aragonés i. lópez doi: 10.2495/CMEM-V5-N5-750-759 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 750 10.2495/CMEM-V5-N5-750-759 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-750-759 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-741-749 One of the main problems of coastlines around the world is their erosion. There are many studies that have tried to link coastal erosion with different parameters such as: maritime climate, sediment transport, sea level rise etc. However, it is unclear to what extent these factors influence coastal erosion. For example, the Intergovernmental Panel on Climate Change (IPCC) has predicted an increase in sea level at a much faster rate than that experienced in the first part of this century, reaching 1 m of elevation in some areas. Another factor to consider is the lack of sediment supply, since currently the contribution of new sediments from rivers or ravines is interrupted by anthropic activities carried out in their basins (dams, channelling, etc.). The big storms, increasingly frequent due to climate change, also should be considered, since they produce an off-shore sediments transport, so that these cross the depth of clo- sure, causing nonreturn of the sediment to the beach. Also, the sediment undergoes a process of wear due to various reasons such as the dissolution of the carbonate fraction and/or breakage and separation of the components of the particles. All these elements, to a greater or lesser extent, lead to the retreat of the coastline. Therefore, the aim of this study is to analyse the different factors causing the retreat of the coastline, in order to determine the degree of involvement of each of them and, therefore, be able to pose different proposals to reduce the consequences of coastal erosion. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">One of the main problems of coastlines around the world is their erosion. There are many studies that have tried to link coastal erosion with different parameters such as: maritime climate, sediment transport, sea level rise etc. However, it is unclear to what extent these factors influence coastal erosion. For example, the Intergovernmental Panel on Climate Change (IPCC) has predicted an increase in sea level at a much faster rate than that experienced in the first part of this century, reaching 1 m of elevation in some areas. Another factor to consider is the lack of sediment supply, since currently the contribution of new sediments from rivers or ravines is interrupted by anthropic activities carried out in their basins (dams, channelling, etc.). The big storms, increasingly frequent due to climate change, also should be considered, since they produce an off-shore sediments transport, so that these cross the depth of clo- sure, causing nonreturn of the sediment to the beach. Also, the sediment undergoes a process of wear due to various reasons such as the dissolution of the carbonate fraction and/or breakage and separation of the components of the particles. All these elements, to a greater or lesser extent, lead to the retreat of the coastline. Therefore, the aim of this study is to analyse the different factors causing the retreat of the coastline, in order to determine the degree of involvement of each of them and, therefore, be able to pose different proposals to reduce the consequences of coastal erosion.</span></p> ]]> Factors Influencing the Retreat of the Coastline m. lópez j.i. pagán i. lópez a.j. tenza-abril j. garcía-barba doi: 10.2495/CMEM-V5-N5-741-749 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 741 10.2495/CMEM-V5-N5-741-749 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-741-749 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-733-740 An axle bearing is one of the most important components to guarantee the service life of a rail car. In order to ensure the stable and reliable bearing life, it is essential to estimate the fatigue life of an axle bearing under the loading conditions. The fatigue life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, operating temperature, loading conditions, bearing geometry, the internal clearance of bearing, and so on. Because these factors are so complicatedly related to each other, it is very important to investigate the effects of these factors on the axle bearing life. This paper presents the process of estimating the fatigue life of a railroad roller bearing, which takes into account geometric parameters of the bearing in the life calculation. The load distributions of the bearing were determined by solving numerically force and moment equilibrium equations with Lundberg’s approximate model. This paper focuses on analyzing the effects of bearing geometric parameters on the fatigue life using Taguchi method. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">An axle bearing is one of the most important components to guarantee the service life of a rail car. In order to ensure the stable and reliable bearing life, it is essential to estimate the fatigue life of an axle bearing under the loading conditions. The fatigue life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, operating temperature, loading conditions, bearing geometry, the internal clearance of bearing, and so on. Because these factors are so complicatedly related to each other, it is very important to investigate the effects of these factors on the axle bearing life. This paper presents the process of estimating the fatigue life of a railroad roller bearing, which takes into account geometric parameters of the bearing in the life calculation. The load distributions of the bearing were determined by solving numerically force and moment equilibrium equations with Lundberg’s approximate model. This paper focuses on analyzing the effects of bearing geometric parameters on the fatigue life using Taguchi method.</span></p> ]]> Fatigue Life Analysis of a Railway Bearing Using Taguchi Method t.k. ahn j.y. heo s.h. lee h.j. jung j.w. kim h.b. yi doi: 10.2495/CMEM-V5-N5-733-740 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 733 10.2495/CMEM-V5-N5-733-740 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-733-740 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-723-732 The design and optimisation of a latent heat thermal storage system require knowledge of flow, heat and mass transfer during the melting (charging) and solidification (discharging) processes of high-temperature phase change materials (PCMs). Using fluent, numerical modeling was performed to study the impact of natural convection and turbulence in the melting process of a high- temperature PCM in a latent heat storage system with Ra = 1012. Numerical calculation was conducted, considering a two dimensional symmetric grid of a dual-tube element in a parallel flow shell and tube configuration where the heat transfer fluid passes through the tube and PCM fills the shell. Three melting processes of PCM were considered; pure conduction, conduction and natural convection, and finally the latter with turbulence. The first study showed a one dimensional melt front, evolving parallel to the tube, which results in lower peak temperatures and temperature gradients, higher heat transfer area for a longer period of time, however lower heat transfer rate due to natural convection being ignored. The second study presented a two dimensional melt front which evolves mainly perpendicular to the tube, shrinking downward, resulting in the loss of heat transfer area and higher peak temperatures and temperature gradient, however, the higher rate of heat transfer rate due to the creation of convection cells which facilitate mass and heat transfer. Including turbulence led to a higher mixing effect due to the higher velocity of convection cells, resulting in a more uniform process with lower peak temperature and temperature gradients and higher heat transfer rate. In a melting process with Ra>1011, including convection and turbulence impact provides more realistic data of flow, mass and heat transfer. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The design and optimisation of a latent heat thermal storage system require knowledge of flow, heat and mass transfer during the melting (charging) and solidification (discharging) processes of high-temperature phase change materials (PCMs). Using fluent, numerical modeling was performed to study the impact of natural convection and turbulence in the melting process of a high- temperature PCM in a latent heat storage system with Ra = 1012. Numerical calculation was conducted, considering a two dimensional symmetric grid of a dual-tube element in a parallel flow shell and tube configuration where the heat transfer fluid passes through the tube and PCM fills the shell. Three melting processes of PCM were considered; pure conduction, conduction and natural convection, and finally the latter with turbulence. The first study showed a one dimensional melt front, evolving parallel to the tube, which results in lower peak temperatures and temperature gradients, higher heat transfer area for a longer period of time, however lower heat transfer rate due to natural convection being ignored. The second study presented a two dimensional melt front which evolves mainly perpendicular to the tube, shrinking downward, resulting in the loss of heat transfer area and higher peak temperatures and temperature gradient, however, the higher rate of heat transfer rate due to the creation of convection cells which facilitate mass and heat transfer. Including turbulence led to a higher mixing effect due to the higher velocity of convection cells, resulting in a more uniform process with lower peak temperature and temperature gradients and higher heat transfer rate. In a melting process with Ra>1011, including convection and turbulence impact provides more realistic data of flow, mass and heat transfer. </span></p> ]]> Numerical Study of Melting Process of a High-Temperature Phase Change Material Including Natural Convection and Turbulence s. riahi w.y. saman f. bruno n.h.s. tay doi: 10.2495/CMEM-V5-N5-723-732 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 723 10.2495/CMEM-V5-N5-723-732 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-723-732 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-713-722 Polyhydroxyalkanoates (PHAs) are a family of biodegradable and biocompatible polyesters that have recently attracted much industrial attention. The most representative PHA is poly(3-hydroxybutyrate) (PHB), though it presents several shortcomings such as brittleness and poor impact resistance. 3-hydroxy- hexanoate units can be incorporated in PHB to obtain poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a copolymer with improved mechanical properties, processability and biodegradability, more suitable for biomedical applications. In this study, chitosan-grafted polycaprolactone (CS-g- PCL)/PHBHHx fiber blends in different compositions were developed by wet electrospinning, and their morphology, biodegradability, mechanical and tribological properties were investigated. A direct correlation was found between the wear rate and the mechanical properties, pointing that fiber breakage is the mechanism responsible for both the abrasive wear and yield. The interactions between the components led to a synergistic effect on tensile and tribological properties at a blend composition of 70/30, resulting in an optimum combination of maximum stiffness, strength, ductility and toughness and minimum coefficient of friction and wear rate, ascribed to the lower porosity and higher crystallinity of this sample. Further, it exhibits the slowest degradation rate. These fiber blends are ideal candidates as scaffolds for tissue engineering applications. 08-31-2017 <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Polyhydroxyalkanoates (PHAs) are a family of biodegradable and biocompatible polyesters that have recently attracted much industrial attention. The most representative PHA is poly(3-hydroxybutyrate) (PHB), though it presents several shortcomings such as brittleness and poor impact resistance. 3-hydroxy- hexanoate units can be incorporated in PHB to obtain poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a copolymer with improved mechanical properties, processability and biodegradability, more suitable for biomedical applications. In this study, chitosan-grafted polycaprolactone (CS-g- PCL)/PHBHHx fiber blends in different compositions were developed by wet electrospinning, and their morphology, biodegradability, mechanical and tribological properties were investigated. A direct correlation was found between the wear rate and the mechanical properties, pointing that fiber breakage is the mechanism responsible for both the abrasive wear and yield. The interactions between the components led to a synergistic effect on tensile and tribological properties at a blend composition of 70/30, resulting in an optimum combination of maximum stiffness, strength, ductility and toughness and minimum coefficient of friction and wear rate, ascribed to the lower porosity and higher crystallinity of this sample. Further, it exhibits the slowest degradation rate. These fiber blends are ideal candidates as scaffolds for tissue engineering applications.</span></p> ]]> Development and Characterization of Chitosan-Grafted Polycaprolactone/Poly (3-Hydroxybutyrate-CO-3-Hydroxyhexanoate) Fiber Blends for Tissue Engineering Applications a.m. diez-pascual doi: 10.2495/CMEM-V5-N5-713-722 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 713 10.2495/CMEM-V5-N5-713-722 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-713-722 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-696-712 This paper discussed about the consequences of using different filler metal by metal inert gas (MIG) welding process on aluminium alloys Al 7075 sheet metal joint. Nowadays, Al 7075 is widely used in automobile and aviation industry due to its light weight, strong, and high hardness. Fusion welding, such as MIG and TIG were commonly used in joining the aluminium alloys due to its low cost. However, defects usually occurred using fusion welding because of the inaccurate welding parameters and types of filler metal used. The purpose of this study is to determine whether the filler metal with different elements and welding parameters affect the mechanical properties of welded Al 7075. Welding parameters used were current, voltage, welding speed, and Argon (Ar) as shielding gas. Two different types of filler metal were used which is Electrode Rod (ER) 4043 and ER5356 which is from Al-Si and Al-Mg based element, respectively. From microstructure analysis, fusion zone (FZ) of sample welded with ER4043 has a smaller grain size than that of with ER5356. Both filler produced equiaxed dendritic grain at FZ. Both samples welded with ER4043 and ER5356 has lower hardness value than heat affected zone (HAZ) and base metal (BM) due to the differences in their elements where ER4043 from Al-Si and ER5356 from Al-Mg group. The weld efficiency of sample welded using ER5356 was 61% which was higher compared to sample welded using ER4043 which at 43% and both sample was brittle fractured. Sample welded with ER5356 was fractured at HAZ due to porosity while sample welded with ER4043 fractured at FZ due to the oxide inclusion. 08-31-2017 <![CDATA[ <p>This paper discussed about the consequences of using different filler metal by metal inert gas (MIG) welding process on aluminium alloys Al 7075 sheet metal joint. Nowadays, Al 7075 is widely used in automobile and aviation industry due to its light weight, strong, and high hardness. Fusion welding, such as MIG and TIG were commonly used in joining the aluminium alloys due to its low cost. However, defects usually occurred using fusion welding because of the inaccurate welding parameters and types of filler metal used. The purpose of this study is to determine whether the filler metal with different elements and welding parameters affect the mechanical properties of welded Al 7075. Welding parameters used were current, voltage, welding speed, and Argon (Ar) as shielding gas. Two different types of filler metal were used which is Electrode Rod (ER) 4043 and ER5356 which is from Al-Si and Al-Mg based element, respectively. From microstructure analysis, fusion zone (FZ) of sample welded with ER4043 has a smaller grain size than that of with ER5356. Both filler produced equiaxed dendritic grain at FZ. Both samples welded with ER4043 and ER5356 has lower hardness value than heat affected zone (HAZ) and base metal (BM) due to the differences in their elements where ER4043 from Al-Si and ER5356 from Al-Mg group. The weld efficiency of sample welded using ER5356 was 61% which was higher compared to sample welded using ER4043 which at 43% and both sample was brittle fractured. Sample welded with ER5356 was fractured at HAZ due to porosity while sample welded with ER4043 fractured at FZ due to the oxide inclusion.</p> ]]> The Mechanical and Microstructural Study of Welded AA7075 Using Different Filler Metals m. ishak m.n.m. salleh s.r. aisha doi: 10.2495/CMEM-V5-N5-696-712 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 696 10.2495/CMEM-V5-N5-696-712 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-696-712 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-686-695 In this study, we develop an efficient topology optimisation method with the H -matrix method and the boundary element method (BEM). In sensitivity analyses of topology optimisation, we need to solve a set of two algebraic equations whose coefficient matrices are common, particularly in many cases. For such cases, by using a direct solver such as LU decomposition to factorise the coefficient matrix, we can reduce the computational time for the sensitivity analysis. A coefficient matrix derived by the BEM is, however, fully populated, which causes high numerical costs for the LU decomposition. In this research, the LU decomposition is accelerated by using the H -matrix method for the sensitivity analyses of topology optimisation problems. We demonstrate the efficiency of the proposed method by a numerical example of a multi-objective optimisation problem for 2D electromagnetic field. 08-31-2017 <![CDATA[ <p>In this study, we develop an efficient topology optimisation method with the H -matrix method and the boundary element method (BEM). In sensitivity analyses of topology optimisation, we need to solve a set of two algebraic equations whose coefficient matrices are common, particularly in many cases. For such cases, by using a direct solver such as LU decomposition to factorise the coefficient matrix, we can reduce the computational time for the sensitivity analysis. A coefficient matrix derived by the BEM is, however, fully populated, which causes high numerical costs for the LU decomposition. In this research, the LU decomposition is accelerated by using the H -matrix method for the sensitivity analyses of topology optimisation problems. We demonstrate the efficiency of the proposed method by a numerical example of a multi-objective optimisation problem for 2D electromagnetic field.</p> ]]> Acceleration of a Multi-objective Topology Optimisation in 2D Electro-Magnetic Field Based on the Level-Set Method and the Boundary Element Method by the $\mathscr{H}$-Matrix Method k. nakamoto h. isakari t. takahashi t. matsumoto doi: 10.2495/CMEM-V5-N5-686-695 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 686 10.2495/CMEM-V5-N5-686-695 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-686-695 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-678-685 The paper deals with time domain-deterministic stochastic assessment of a transient electric field generated by a ground penetrating radar (GPR) dipole antenna and transmitted into a lower half-space. The deterministic time domain formulation is based on the space-time Hallen integral equation for half-space problems. The Hallen equation is solved via the Galerkin–Bubnov variant of the Indirect Boundary Element Method (GB-IBEM) and the space-time current distribution along the dipole antenna is obtained, thus providing the field calculation. The field transmitted into the lower medium is obtained by solving the corresponding field integrals.As GPR systems are subjected to a rather complex environment, some input parameters, for example the antenna height over ground or earth properties, are partly or entirely unknown and, therefore, a simple stochastic collocation (SC) method is used to properly access relevant statistics about GPR time responses. The SC approach also aids in the assessment of corresponding confidence intervals from the set of obtained numerical results. The expansion of statistical output in terms of mean and variance over a polynomial basis, via the SC method, is shown to be a robust and efficient approach providing a satisfactory convergence rate. 08-31-2017 <![CDATA[ <p>The paper deals with time domain-deterministic stochastic assessment of a transient electric field generated by a ground penetrating radar (GPR) dipole antenna and transmitted into a lower half-space. The deterministic time domain formulation is based on the space-time Hallen integral equation for half-space problems. The Hallen equation is solved via the Galerkin–Bubnov variant of the Indirect Boundary Element Method (GB-IBEM) and the space-time current distribution along the dipole antenna is obtained, thus providing the field calculation. The field transmitted into the lower medium is obtained by solving the corresponding field integrals.</p><p style="text-align: justify">As GPR systems are subjected to a rather complex environment, some input parameters, for example the antenna height over ground or earth properties, are partly or entirely unknown and, therefore, a simple stochastic collocation (SC) method is used to properly access relevant statistics about GPR time responses. The SC approach also aids in the assessment of corresponding confidence intervals from the set of obtained numerical results. The expansion of statistical output in terms of mean and variance over a polynomial basis, via the SC method, is shown to be a robust and efficient approach providing a satisfactory convergence rate.</p> ]]> Stochastic Post-Processing of the Deterministic Boundary Element Modelling of the Transient Electric Field from Gpr Dipole Antenna Propagating Through Lower Half-Space d. poljak s. sesnic s. lallechere k. el khamlichi drissi doi: 10.2495/CMEM-V5-N5-678-685 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 678 10.2495/CMEM-V5-N5-678-685 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-678-685 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-667-677 This paper deals with a shape optimization of pump suction, with the objective of improving the pump performance. A combination of ANSYS CFX software tools and a surrogate-based, so-called multistart local metric stochastic RBF (MLMSRBF) method for the global optimization of “expensive black-box functions” is employed. The shape of the suction is driven by 18 geometric parameters, and the cost functional is based on the CFD results. The practical aspects of assembling and evaluating a parametric CFD model, including mesh independence study, are shown. After initial design of experiment evaluation, a response surface model is created and used for generating new sample points for the expensive CFD evaluation. Then, the whole process is repeated as long as necessary. A parallel version of the method is used, with necessary modifications for dealing with CFD-specific problems, such as failed designs and uncertainty of computational times. Both steady-state and transient models are used for the optimization, each with a different objective function. The resulting designs are then compared with the original geometry, using a complete model of the pump and fully-transient simulation. Both hydraulic characteristics and multiphase cavitational simulations are considered for the comparison. At the end, the results and challenges of using these methods for CFD-driven shape optimization are discussed. 08-31-2017 <![CDATA[ <p>This paper deals with a shape optimization of pump suction, with the objective of improving the pump performance. A combination of ANSYS CFX software tools and a surrogate-based, so-called multistart local metric stochastic RBF (MLMSRBF) method for the global optimization of “expensive black-box functions” is employed. The shape of the suction is driven by 18 geometric parameters, and the cost functional is based on the CFD results. The practical aspects of assembling and evaluating a parametric CFD model, including mesh independence study, are shown. After initial design of experiment evaluation, a response surface model is created and used for generating new sample points for the expensive CFD evaluation. Then, the whole process is repeated as long as necessary. A parallel version of the method is used, with necessary modifications for dealing with CFD-specific problems, such as failed designs and uncertainty of computational times. Both steady-state and transient models are used for the optimization, each with a different objective function. The resulting designs are then compared with the original geometry, using a complete model of the pump and fully-transient simulation. Both hydraulic characteristics and multiphase cavitational simulations are considered for the comparison. At the end, the results and challenges of using these methods for CFD-driven shape optimization are discussed. </p> ]]> Pump Suction Shape Optimization Using a Parallel Stochastic Radial Basis Function Method t. kratky l. zavadil m. tabatabaei doi: 10.2495/CMEM-V5-N5-667-677 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 667 10.2495/CMEM-V5-N5-667-677 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-667-677 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-659-666 Cathodic protection (CP) is a technique that prevents corrosion of underground metallic structures. Design of any CP system first requires defining the protection of current density and potential distribution, which should meet the given criterion. It also needs to provide, as uniform as possible, current density distribution on the protected object surface. Determination of current density and potential distribution of CP system is based on solving the Laplace partial differential equation. Mathematical model, along with the Laplace equation, is represented by two additional equations that define boundary conditions. These two equations are non-linear and they represent the polarization curves that define the relationship between current density and potential on electrode surfaces. Nowadays, the only reliable way to determine current density and potential distribution is by applying numerical techniques. This paper presents efficient numerical techniques for the calculation of current density and potential distribution of CP system based on the coupled boundary element method (BEM) and finite element method (FEM). 08-31-2017 <![CDATA[ <p>Cathodic protection (CP) is a technique that prevents corrosion of underground metallic structures. Design of any CP system first requires defining the protection of current density and potential distribution, which should meet the given criterion. It also needs to provide, as uniform as possible, current density distribution on the protected object surface. Determination of current density and potential distribution of CP system is based on solving the Laplace partial differential equation. Mathematical model, along with the Laplace equation, is represented by two additional equations that define boundary conditions. These two equations are non-linear and they represent the polarization curves that define the relationship between current density and potential on electrode surfaces. Nowadays, the only reliable way to determine current density and potential distribution is by applying numerical techniques. This paper presents efficient numerical techniques for the calculation of current density and potential distribution of CP system based on the coupled boundary element method (BEM) and finite element method (FEM).</p> ]]> Application of the Coupled BEM/FEM Method for Calculation of Cathodic Protection System Parameters adnan mujezinović sanja martinez alija muharemović irfan turković doi: 10.2495/CMEM-V5-N5-659-666 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 659 10.2495/CMEM-V5-N5-659-666 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-659-666 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-647-658 Isosurfaces are an appropriate approach to visualize scalar fields or the absolute value of vector fields in three dimensions. The nodes of the corresponding isosurface mesh are determined using an efficient and accurate isovalue search method. Then, these nodes are typically connected by triangular elements, which are obtained with the help of an adapted advancing front algorithm. An important prerequisite of an isovalue search method is that volume data of the examined field is available in total space. That means, the field values are precomputed in the nodes of an auxiliary post-processing volume mesh or a novel meshfree method is developed that enables both efficient computations of field values in arbitrary points and fast determination of domains with a defined range of field values. If the first approach is applied, a classical isovalue search method is to use an octree scheme to find relevant volume elements, which are intersected by the isosurface. Finally, the surface elements of the isosurface are constructed based on the intersection points of the isosurface with the volume elements. In that case, the accuracy and the computational costs are mainly influenced by the density of the post-processing volume mesh. In contrast, an innovative coupling of established isovalue search methods, fast boundary element method (BEM) techniques, and advancing front meshing algorithms is here presented to compute isosurfaces with high accuracy only using the original BEM model. This novel meshfree method enables very accurate isovalue search methods along with nearly arbitrarily adjustable resolution of the computed isosurface. Furthermore, refinements of the isosurface are also possible, for instance in dependency of the current viewing position. The main idea to realize this meshfree method is to directly combine an octree-based isovalue search method with the octree-based fast multipole method (FMM). 08-31-2017 <![CDATA[ <p>Isosurfaces are an appropriate approach to visualize scalar fields or the absolute value of vector fields in three dimensions. The nodes of the corresponding isosurface mesh are determined using an efficient and accurate isovalue search method. Then, these nodes are typically connected by triangular elements, which are obtained with the help of an adapted advancing front algorithm. An important prerequisite of an isovalue search method is that volume data of the examined field is available in total space. That means, the field values are precomputed in the nodes of an auxiliary post-processing volume mesh or a novel meshfree method is developed that enables both efficient computations of field values in arbitrary points and fast determination of domains with a defined range of field values. If the first approach is applied, a classical isovalue search method is to use an octree scheme to find relevant volume elements, which are intersected by the isosurface. Finally, the surface elements of the isosurface are constructed based on the intersection points of the isosurface with the volume elements. In that case, the accuracy and the computational costs are mainly influenced by the density of the post-processing volume mesh. In contrast, an innovative coupling of established isovalue search methods, fast boundary element method (BEM) techniques, and advancing front meshing algorithms is here presented to compute isosurfaces with high accuracy only using the original BEM model. This novel meshfree method enables very accurate isovalue search methods along with nearly arbitrarily adjustable resolution of the computed isosurface. Furthermore, refinements of the isosurface are also possible, for instance in dependency of the current viewing position. The main idea to realize this meshfree method is to directly combine an octree-based isovalue search method with the octree-based fast multipole method (FMM)<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">. </span></p> ]]> A Meshfree Isosurface Computation Method for Boundary Element Methods andré buchau wolfgang m. rucker doi: 10.2495/CMEM-V5-N5-647-658 International Journal of Computational Methods and Experimental Measurements 08-31-2017 International Journal of Computational Methods and Experimental Measurements 08-31-2017 2017 5 5 Article 647 10.2495/CMEM-V5-N5-647-658 https://www.acadlore.com/article/IJCMEM/2017_5_5/CMEM-V5-N5-647-658 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-631-641 The paper investigates the possibility to create kinetic rosette patterns and their tessellations by means of modular linkages which rely on the same type and number of symmetry operations as the reference models. The mechanisms show a hierarchy of movements. It is found that symmetry is an effective unifying concept in the design of both the fixed models and the mechanisms. Furthermore, the resulting rosette linkages and their tessellations have peculiar kinematic characteristics if compared to other modular mechanisms which may be alternatively used to reproduce the same kind of models. <![CDATA[ <p>The paper investigates the possibility to create kinetic rosette patterns and their tessellations by means of modular linkages which rely on the same type and number of symmetry operations as the reference models. The mechanisms show a hierarchy of movements. It is found that symmetry is an effective unifying concept in the design of both the fixed models and the mechanisms. Furthermore, the resulting rosette linkages and their tessellations have peculiar kinematic characteristics if compared to other modular mechanisms which may be alternatively used to reproduce the same kind of models. </p> ]]> Kinetic Rosette Patterns and Tessellations valentina beatini doi: 10.2495/CMEM-V5-N4-631-641 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 631 10.2495/CMEM-V5-N4-631-641 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-631-641 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-619-630 To intrinsically motivate students by challenging concrete tasks is an effective way of learning – and in particular, if the task is intended to deliver a tangible outcome. Bearing this in mind, a challenging Problem Based Learning assignment for Master students of TU/e was found in developing a sustainable pavilion for festivals in cooperation with a third party (Double2). Many (music) festivals nowadays go on the message of sustainability in addition to their core business of ‘music and food’. This can offer a very challenging assignment; to develop an iconic object that stands out in a large-scale event and by making sustainability tangible to a large audience. The aspect of designing a temporal and original creation is already challenging, yet it becomes integral (‘Research by Design’) by involving practical requirements that have to be met too regarding safety aspects, fast and practical assembling, et cetera. And by actually building a full-scale creation makes this project exceptionally, being the proof of the pudding of the creation as well as the icing on the cake for all involved (and a special item for a students’ portfolio). Making prototypes and considering details on different scale levels (‘learning by doing’) is very instructive for students who study buildings. And helping to assemble the pavilions on a festival and support the set-up on location (‘learning by precedent’) is highly enlightening, too.This paper describes the ‘Summerlabb’ project of developing a number of structures as itinerant exhibition at festivals and events that were developed in analogy with earlier design projects where student teams were involved. <![CDATA[ <p>To intrinsically motivate students by challenging concrete tasks is an effective way of learning – and in particular, if the task is intended to deliver a tangible outcome. Bearing this in mind, a challenging Problem Based Learning assignment for Master students of TU/e was found in developing a sustainable pavilion for festivals in cooperation with a third party (Double2). Many (music) festivals nowadays go on the message of sustainability in addition to their core business of ‘music and food’. This can offer a very challenging assignment; to develop an iconic object that stands out in a large-scale event and by making sustainability tangible to a large audience. The aspect of designing a temporal and original creation is already challenging, yet it becomes integral (‘Research by Design’) by involving practical requirements that have to be met too regarding safety aspects, fast and practical assembling, et cetera. And by actually building a full-scale creation makes this project exceptionally, being the proof of the pudding of the creation as well as the icing on the cake for all involved (and a special item for a students’ portfolio). Making prototypes and considering details on different scale levels (‘learning by doing’) is very instructive for students who study buildings. And helping to assemble the pavilions on a festival and support the set-up on location (‘learning by precedent’) is highly enlightening, too.</p><p>This paper describes the ‘Summerlabb’ project of developing a number of structures as itinerant exhibition at festivals and events that were developed in analogy with earlier design projects where student teams were involved.</p> ]]> Visibility of Sustainability: The Making of the Itinerant Pavilion ‘Summerlabb’ s.p.g. moonen doi: 10.2495/CMEM-V5-N4-619-630 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 619 10.2495/CMEM-V5-N4-619-630 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-619-630 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-607-618 Kinetic behavior is a progressive methodology in architecture and design that allows some parts to move by mechanics or sensors, without reducing the overall structural integrity. It’s the dynamic approach that integrates the different aspects arranging the outlined design. This paper aims to study the impact of intelligent systems in the interior design to produce new structures for interior elements within the terms of varied patterns and shape. It reveals the emergence of kinetic systems as an adequate procedure and substantial function to rethink and reshape interior spaces through metamorphic design, mobility, and mechanisms. These systems are applied due to their transition to portray and shift either, through specific forms or materials to plan new interactive inhabited spaces. This paper dissects the changes affecting the function of interior spaces through the analysis and interpretation of some architectural projects adapting dynamic mobile systems on setting the state and the structure of the building. Additionally, the main criteria pertaining the design to achieve further responsive potential, that is more engaged to the recipient and the environmental surroundings. Finally, the paper discusses the results of implementing canny dynamic systems and kinetic mechanisms to the elements of interior design tend- ing how they can rapidly modify their function and regulate the performance and the efficiency and how to apply this methodology to reshape interior spaces. <![CDATA[ <p>Kinetic behavior is a progressive methodology in architecture and design that allows some parts to move by mechanics or sensors, without reducing the overall structural integrity. It’s the dynamic approach that integrates the different aspects arranging the outlined design. This paper aims to study the impact of intelligent systems in the interior design to produce new structures for interior elements within the terms of varied patterns and shape. It reveals the emergence of kinetic systems as an adequate procedure and substantial function to rethink and reshape interior spaces through metamorphic design, mobility, and mechanisms. These systems are applied due to their transition to portray and shift either, through specific forms or materials to plan new interactive inhabited spaces. This paper dissects the changes affecting the function of interior spaces through the analysis and interpretation of some architectural projects adapting dynamic mobile systems on setting the state and the structure of the building. Additionally, the main criteria pertaining the design to achieve further responsive potential, that is more engaged to the recipient and the environmental surroundings. Finally, the paper discusses the results of implementing canny dynamic systems and kinetic mechanisms to the elements of interior design tend- ing how they can rapidly modify their function and regulate the performance and the efficiency and how to apply this methodology to reshape interior spaces.</p> ]]> Kinetic Behavior, the Dynamic Potential through Architecture and Design mai m. youssef doi: 10.2495/CMEM-V5-N4-607-618 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 607 10.2495/CMEM-V5-N4-607-618 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-607-618 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-593-606 The paper discusses research that concerns itself with the design explorations of high performance structural and climatic systems. It also examines their efficient and low-cost application techniques in refugee facilities. Initially, the paper presents a survey of the current conditions of refugee schools in Lebanon. The survey highlights the need for alternative design strategies in the provision of environmentally friendly educational facilities with low-cost yet adequate learning conditions. Considering the current conditions, the premise is set that required design strategies call for an integrated strategic approach. This is to promote sustainable development models as post-disaster responses. The “Nasma” project is then taken as a case study that exemplifies a sustainable pilot project as a post-disaster response. It is an educational unit developed and implemented in Lebanon by the author in collaboration with a team from Transsolar climate engineers led by Christian Frenzel. It therefore represents a paradigm of integrated architectural and environmental design strategies taking into considering the complex socio-political context of refugee settlements in Lebanon’s Bekaa Valley. The project aims to provide visual, air, thermal and acoustic comfort. It also integrates innovative structural systems and construction methods that allow the school to be rapidly deployed and relocated. Strategies that aim towards social impact include using local materials and engaging the community in the building process. Finally the paper concludes by assessing the actual performance of the structure as a replicable post-disaster response. <![CDATA[ <p>The paper discusses research that concerns itself with the design explorations of high performance structural and climatic systems. It also examines their efficient and low-cost application techniques in refugee facilities. Initially, the paper presents a survey of the current conditions of refugee schools in Lebanon. The survey highlights the need for alternative design strategies in the provision of environmentally friendly educational facilities with low-cost yet adequate learning conditions. Considering the current conditions, the premise is set that required design strategies call for an integrated strategic approach. This is to promote sustainable development models as post-disaster responses. The “Nasma” project is then taken as a case study that exemplifies a sustainable pilot project as a post-disaster response. It is an educational unit developed and implemented in Lebanon by the author in collaboration with a team from Transsolar climate engineers led by Christian Frenzel. It therefore represents a paradigm of integrated architectural and environmental design strategies taking into considering the complex socio-political context of refugee settlements in Lebanon’s Bekaa Valley. The project aims to provide visual, air, thermal and acoustic comfort. It also integrates innovative structural systems and construction methods that allow the school to be rapidly deployed and relocated. Strategies that aim towards social impact include using local materials and engaging the community in the building process. Finally the paper concludes by assessing the actual performance of the structure as a replicable post-disaster response.</p> ]]> Nasma; Sustainable Climate-Responsive Schools for Syrian Refugees in Lebanon k. najjar b. madi a. nouraldeen doi: 10.2495/CMEM-V5-N4-593-606 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 593 10.2495/CMEM-V5-N4-593-606 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-593-606 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-583-592 In the Canadian high Arctic, subsistence hunters and fishers have learned, over generations, to construct shelters from available materials so they can survive inclement weather while harvesting food. Now, as accelerating climate change exacerbates the intensity and unpredictability of extreme weather, scientists and country food harvesters once again worry about becoming stranded. To envision how tradition-based dwellings might serve as modern short-term survival/emergency structures, we reconstructed four vernacular structures in largely- Indigenous Arctic communities and compared them with a Sami reconstruction from Arctic Scandinavia. Local knowledge-holders and students participated and proposed adaptations using modern materials and concepts. The five structures were qualitatively evaluated for replicability, adaptability to modern situations, on-going usefulness, thermal performance, and materials availability. Quantitative evaluations included speed of construction relative to length of use and approximate mass of structure per person. The structures that were most adaptable, replicable, and efficient were elliptic paraboloid-shaped dwellings: Inuvialuit willow-framed moss-and-skin-clad dwellings (Western Canadian Arctic), Inuinnaqtun snow houses (iglus and qarmaqs) (central Canadian high Arctic), and birch-framed turf-clad homes (Scandinavian Arctic). All shared the following characteristics: (1) catenary- or elliptic paraboloid-domed frame- work, (2) materials accessed from immediate vicinity of building site, (3) ease of construction by 1 or few people, (4) passive heating and insulated assemblies, (5) windbreaks incorporated into siting and design, (6) strong structure resistant to high winds and inclement weather, and (7) siting along routes where foods are harvested. These characteristics are now serving as design principles for tem- porary Arctic dwellings, demonstrating how recording, adapting, and sharing long-resident peoples’ architectural knowledge facilitates survival during extreme events associated with accelerated climate change. <![CDATA[ <p>In the Canadian high Arctic, subsistence hunters and fishers have learned, over generations, to construct shelters from available materials so they can survive inclement weather while harvesting food. Now, as accelerating climate change exacerbates the intensity and unpredictability of extreme weather, scientists and country food harvesters once again worry about becoming stranded. To envision how tradition-based dwellings might serve as modern short-term survival/emergency structures, we reconstructed four vernacular structures in largely- Indigenous Arctic communities and compared them with a Sami reconstruction from Arctic Scandinavia. Local knowledge-holders and students participated and proposed adaptations using modern materials and concepts. The five structures were qualitatively evaluated for replicability, adaptability to modern situations, on-going usefulness, thermal performance, and materials availability. Quantitative evaluations included speed of construction relative to length of use and approximate mass of structure per person. The structures that were most adaptable, replicable, and efficient were elliptic paraboloid-shaped dwellings: Inuvialuit willow-framed moss-and-skin-clad dwellings (Western Canadian Arctic), Inuinnaqtun snow houses (iglus and qarmaqs) (central Canadian high Arctic), and birch-framed turf-clad homes (Scandinavian Arctic). All shared the following characteristics: (1) catenary- or elliptic paraboloid-domed frame- work, (2) materials accessed from immediate vicinity of building site, (3) ease of construction by 1 or few people, (4) passive heating and insulated assemblies, (5) windbreaks incorporated into siting and design, (6) strong structure resistant to high winds and inclement weather, and (7) siting along routes where foods are harvested. These characteristics are now serving as design principles for tem- porary Arctic dwellings, demonstrating how recording, adapting, and sharing long-resident peoples’ architectural knowledge facilitates survival during extreme events associated with accelerated climate change.</p> ]]> Future Architecture, Ancient Wisdom: Adaptable Structures from Arctic Tradition n.p. mackin doi: 10.2495/CMEM-V5-N4-583-592 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 583 10.2495/CMEM-V5-N4-583-592 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-583-592 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-574-582 StemXel is a response to the need of continuous change of functions in interior design and architecture. It can be converted into mutable forms with the use of a permanent material without any waste and provide physical change with seamless work. The structure is flexible to turn a simple single space into an adaptable environment that can be used for multiple programs at multiple instances. The structure is designed to be implemented as a furniture, for housing, commercial activities and for spaces that are undergoing a constant change. StemXel responds to different inputs, digital or analogic, in order to create a fast and fluid physical change. Its flexibility allows the possibility to absorb digital informa- tion, meanwhile reflecting it in a tangible form. It is a structure that goes beyond two-dimension, yet involves the totality of a defined volume. Intelligent interaction between users and space is one of the major characteristics to be exploited in future design development. <![CDATA[ <p>StemXel is a response to the need of continuous change of functions in interior design and architecture. It can be converted into mutable forms with the use of a permanent material without any waste and provide physical change with seamless work. The structure is flexible to turn a simple single space into an adaptable environment that can be used for multiple programs at multiple instances. The structure is designed to be implemented as a furniture, for housing, commercial activities and for spaces that are undergoing a constant change. StemXel responds to different inputs, digital or analogic, in order to create a fast and fluid physical change. Its flexibility allows the possibility to absorb digital informa- tion, meanwhile reflecting it in a tangible form. It is a structure that goes beyond two-dimension, yet involves the totality of a defined volume. Intelligent interaction between users and space is one of the major characteristics to be exploited in future design development.</p> ]]> Stemxel: Interactive Structure for Adaptive Design pier alessio rizzardi basak sakcak hankun zhang edoardo giancola martin huba alejandro rey yamhure doi: 10.2495/CMEM-V5-N4-574-582 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 574 10.2495/CMEM-V5-N4-574-582 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-574-582 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-562-573 Rapid construction, modularity, deconstruction, and reconfiguration facilitate economy and sustainability allowing for changes in a building’s use over time. Typical one-way composite steel/concrete floor systems lend themselves to terminal construction practices that make assumptions about the occupancy and usage needs that must last through the life of the structure. To address this, a lightweight rapidly constructible and reconfigurable modular steel floor (RCRMSF) system that utilizes two-way bending behavior and cold-formed steel building materials has been developed. RCRMSF improves upon the efficiency benefits of traditional composite steel/concrete flooring systems, reducing beam and girder usage and size, and allowing for highly flexible building configurations and mobility. The system con- sists of a series of prefabricated panels composed of a grid of cold-formed steel channels running in orthogonal directions sandwiched together by steel plates. A simple performance assessment has been formulated and a finite element model parametric study has been carried out in the Abaqus finite ele- ment analysis (FEA) software. The results of the developed performance assessment and FEA study show that RCRMSF systems are suitable for rapidly constructible buildings in terms of strength and serviceability, providing an initial step to fully modular and reconfigurable steel buildings. <![CDATA[ <p>Rapid construction, modularity, deconstruction, and reconfiguration facilitate economy and sustainability allowing for changes in a building’s use over time. Typical one-way composite steel/concrete floor systems lend themselves to terminal construction practices that make assumptions about the occupancy and usage needs that must last through the life of the structure. To address this, a lightweight rapidly constructible and reconfigurable modular steel floor (RCRMSF) system that utilizes two-way bending behavior and cold-formed steel building materials has been developed. RCRMSF improves upon the efficiency benefits of traditional composite steel/concrete flooring systems, reducing beam and girder usage and size, and allowing for highly flexible building configurations and mobility. The system con- sists of a series of prefabricated panels composed of a grid of cold-formed steel channels running in orthogonal directions sandwiched together by steel plates. A simple performance assessment has been formulated and a finite element model parametric study has been carried out in the Abaqus finite ele- ment analysis (FEA) software. The results of the developed performance assessment and FEA study show that RCRMSF systems are suitable for rapidly constructible buildings in terms of strength and serviceability, providing an initial step to fully modular and reconfigurable steel buildings.</p> ]]> Lightweight Modular Steel Floor System for Rapidly Constructible and Reconfigurable Buildings eugene boadi-danquah brian robertson matthew fadden elaina j. sutley joe colistra doi: 10.2495/CMEM-V5-N4-562-573 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 562 10.2495/CMEM-V5-N4-562-573 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-562-573 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-551-561 Reciprocal structures or nexorade are composed by the assembling of groups of three or more beams mutually connected by mono-lateral T joints in a way that any relative movement is suppressed. This kind of structures can be easily built in relatively unprepared sites, dismantled, transported and re-used even by not specialized handcraft. For these reasons, reciprocal structures have been widely used in the past for military purposes, and nowadays they seem to satisfy very well the different requirements of a quick and temporary shelter of a large archaeological area when they are shaped as grid shells.This paper proposes the design of a reversible, reciprocal framed grid shell to shelter the archaeological site of the Roman Shipwrecks in Pisa. The structure must protect excavations and archaeologists from the weather and provide an easy access to visitors. Additionally, it must allow for easy disassembling and moving to another site.The design choices aim at optimizing both structural efficiency and esthetical qualities. A parametric workflow for both the form finding and the digital fabrication processes has been developed, and a prototype of accommodative steel T-joint for timber reciprocal beams has been realized. Finally, a model using CNC-cutting tested the structural feasibility of such a design approach. <![CDATA[ <p>Reciprocal structures or nexorade are composed by the assembling of groups of three or more beams mutually connected by mono-lateral T joints in a way that any relative movement is suppressed. This kind of structures can be easily built in relatively unprepared sites, dismantled, transported and re-used even by not specialized handcraft. For these reasons, reciprocal structures have been widely used in the past for military purposes, and nowadays they seem to satisfy very well the different requirements of a quick and temporary shelter of a large archaeological area when they are shaped as grid shells.</p><p>This paper proposes the design of a reversible, reciprocal framed grid shell to shelter the archaeological site of the Roman Shipwrecks in Pisa. The structure must protect excavations and archaeologists from the weather and provide an easy access to visitors. Additionally, it must allow for easy disassembling and moving to another site.</p><p>The design choices aim at optimizing both structural efficiency and esthetical qualities. A parametric workflow for both the form finding and the digital fabrication processes has been developed, and a prototype of accommodative steel T-joint for timber reciprocal beams has been realized. Finally, a model using CNC-cutting tested the structural feasibility of such a design approach.</p> ]]> Conception and Parametric Design Workflow for a Timber Large-Spanned Reversible Grid Shell to Shelter the Archaeological Site of the Roman Shipwrecks in Pisa e. corio f. laccone n. pietroni p. cignoni m. froli doi: 10.2495/CMEM-V5-N4-551-561 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 551 10.2495/CMEM-V5-N4-551-561 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-551-561 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-539-550 For over 20 years, we have followed a line of research that seeks to propose models for architecture which minimize the environmental impact caused by both its construction as its use. We understand that, in order to reduce the environmental impact produced by current constructions, it is necessary to change the way they are designed and built.The followed process has been firstly focused on the search for geometries constructed with adequate materiality which would provide effective architectural solutions with a minimum consumption of material (lightweight solutions). Secondly, we have experienced quick assembly and disassembly procedures (deployable mesh, modular systems, etc.) that reduced the assembly time of the proposed systems and, therefore, will minimize the impact (quick assembly/reversibility). Finally, it has been possible to relate the proposed models (lightweight, quick assembly and reversible) with tools for life- cycle assessment which allow accurately assess the environmental impact of them.The use and development of LCA tools has allowed us to optimize the proposed models. In addition, in the described process, original parametric control tools (geometry and processes) have been used. They allow to particularize the proposed models to each case based on their possibilities of manufacture.The way followed by several made works, which are applications of the proposed models, will be described then. <![CDATA[ <p>For over 20 years, we have followed a line of research that seeks to propose models for architecture which minimize the environmental impact caused by both its construction as its use. We understand that, in order to reduce the environmental impact produced by current constructions, it is necessary to change the way they are designed and built.</p><p>The followed process has been firstly focused on the search for geometries constructed with adequate materiality which would provide effective architectural solutions with a minimum consumption of material (lightweight solutions). Secondly, we have experienced quick assembly and disassembly procedures (deployable mesh, modular systems, etc.) that reduced the assembly time of the proposed systems and, therefore, will minimize the impact (quick assembly/reversibility). Finally, it has been possible to relate the proposed models (lightweight, quick assembly and reversible) with tools for life- cycle assessment which allow accurately assess the environmental impact of them.</p><p>The use and development of LCA tools has allowed us to optimize the proposed models. In addition, in the described process, original parametric control tools (geometry and processes) have been used. They allow to particularize the proposed models to each case based on their possibilities of manufacture.</p><p>The way followed by several made works, which are applications of the proposed models, will be described then.</p> ]]> Lightweight and Quickly Assembled: The Most Eco-Efficient Model for Architecture j. c. gómez de cózar a. garcía martínez i. ariza lópez m. ruiz alfonsea doi: 10.2495/CMEM-V5-N4-539-550 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 539 10.2495/CMEM-V5-N4-539-550 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-539-550 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-532-538 The Sim[PLY] framing system leverages CNC prefabrication and unique connection design in service of rapid and safe on-site assembly without power tools or heavy equipment. Sim[PLY] components are cut from standard sheets of structural plywood and interlock using tab and slot connections in lieu of nails. Steel cable ties are used to secure the connections. In addition to fast and accurate assembly, CNC processing also allows for various forms of intelligent customization, including mechanical and electrical systems integration, component labeling, and diminished thermal bridging.Preliminary structural testing examined the performance of individual connections as well as the performance of full-scale assemblies, including rafters and shear walls. Test results confirmed the ade- quacy of the Sim[PLY] system for natural hazard loading scenarios, including seismic and hurricane events.This paper describes the development and details of the Sim[PLY] system as well as preliminary testing and case studies from various applications. The reader will, in turn, recognize an accessible and economical framing system that simultaneously offers high quality control, minimal waste, structural resiliency, and rapid and intuitive assembly and disassembly. <![CDATA[ <p>The Sim[PLY] framing system leverages CNC prefabrication and unique connection design in service of rapid and safe on-site assembly without power tools or heavy equipment. Sim[PLY] components are cut from standard sheets of structural plywood and interlock using tab and slot connections in lieu of nails. Steel cable ties are used to secure the connections. In addition to fast and accurate assembly, CNC processing also allows for various forms of intelligent customization, including mechanical and electrical systems integration, component labeling, and diminished thermal bridging.</p><p>Preliminary structural testing examined the performance of individual connections as well as the performance of full-scale assemblies, including rafters and shear walls. Test results confirmed the ade- quacy of the Sim[PLY] system for natural hazard loading scenarios, including seismic and hurricane events.</p><p>This paper describes the development and details of the Sim[PLY] system as well as preliminary testing and case studies from various applications. The reader will, in turn, recognize an accessible and economical framing system that simultaneously offers high quality control, minimal waste, structural resiliency, and rapid and intuitive assembly and disassembly.</p> ]]> Sim[PLY]: Rapid Structural Assemblies Using CNC-Fabricated Plywood Components d. albright v. blouin d.n. harding u. heine d. pastre doi: 10.2495/CMEM-V5-N4-532-538 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 532 10.2495/CMEM-V5-N4-532-538 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-532-538 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-522-531 The current return to a logic of movement implied in human behavior and contemporary society, less static than previous generations, involves that modern architecture, in its innumerable fields of application. An effect of this is a change in the design logic of the modern construction to satisfy the requirement of the end-users of architecture more flexible and adaptable, as temporary.The project Mob:om is a part of that, a prefabricated multifunctional module responsive to multiple needs, both functionally and dimensionally. The design concept is based on the realization of a product that, starting from the idea of a furniture, as an object container, arrives to the one of the building container of function, with the same design logic. The Mob:oM, in fact, is designed as a wooden structure that is able to hold itself and its structural, finishing and furnishing elements. It is a flexible and modular building structure whose basic module can be aggregated to other ones, allowing the growth in size, according to the spatial and functional requirements of the users: temporary events, fairs, tourist and emergency residences, exhibition stands. It is also suitable for a controlled disassembly through removable modular components: in fact, on the basis of the concept of flexibility, dry assembly techniques and stratification of constructive components have been used to allow building organism to change itself from the technological, compositive, distributive, functional and performance point of view, according to the needs of the users and the place.The result is a multifunctional, easy to carry, reversible and modular product, characterized by an innovative design and advanced technological solutions. <![CDATA[ <p>The current return to a logic of movement implied in human behavior and contemporary society, less static than previous generations, involves that modern architecture, in its innumerable fields of application. An effect of this is a change in the design logic of the modern construction to satisfy the requirement of the end-users of architecture more flexible and adaptable, as temporary.</p><p>The project <em>Mob:om </em>is a part of that, a prefabricated multifunctional module responsive to multiple needs, both functionally and dimensionally. The design concept is based on the realization of a product that, starting from the idea of a furniture, as an object container, arrives to the one of the building container of function, with the same design logic. The <em>Mob:oM</em>, in fact, is designed as a wooden structure that is able to hold itself and its structural, finishing and furnishing elements. It is a flexible and modular building structure whose basic module can be aggregated to other ones, allowing the growth in size, according to the spatial and functional requirements of the users: temporary events, fairs, tourist and emergency residences, exhibition stands. It is also suitable for a controlled disassembly through removable modular components: in fact, on the basis of the concept of flexibility, dry assembly techniques and stratification of constructive components have been used to allow building organism to change itself from the technological, compositive, distributive, functional and performance point of view, according to the needs of the users and the place.</p><p>The result is a multifunctional, easy to carry, reversible and modular product, characterized by an innovative design and advanced technological solutions. </p> ]]> Mob:Om: A Multifunctional Prefabricated and Flexible Module p. de berardinis c. marchionni l. capannolo doi: 10.2495/CMEM-V5-N4-522-531 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 522 10.2495/CMEM-V5-N4-522-531 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-522-531 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-514-521 Cable arch stayed bridges are one type of tensile structures, and there are increasingly such structures constructed. Their performance relies on how they are designed. This type of structures can suffer big deflections under load, in this situation the displacements may need to be reduced. Sometimes, it may be necessary to control internal force of a specific cable so the cable force remains within the desired limit. More study need to be done to develop the techniques that are available for such adjustments. This paper deals with theoretical and experimental adjusting of two physical models, and the linear and nonlinear geometrical behavior of cable (arch) stayed bridges. It was concluded that the techniques of adjustment were practical and efficient to reduce, eliminate shape distortion, and control internal bar force of both structures. For structures that behave linearly, it is easier to get the target (displacement or force), but for non-linear structures one iteration of adjustments was not enough to get the displacement target. Through the techniques of the internal bar force adjustment, the amount of force can be reduced even to the zero, e.g. in case of replacing damaged members. <![CDATA[ <p>Cable arch stayed bridges are one type of tensile structures, and there are increasingly such structures constructed. Their performance relies on how they are designed. This type of structures can suffer big deflections under load, in this situation the displacements may need to be reduced. Sometimes, it may be necessary to control internal force of a specific cable so the cable force remains within the desired limit. More study need to be done to develop the techniques that are available for such adjustments. This paper deals with theoretical and experimental adjusting of two physical models, and the linear and nonlinear geometrical behavior of cable (arch) stayed bridges. It was concluded that the techniques of adjustment were practical and efficient to reduce, eliminate shape distortion, and control internal bar force of both structures. For structures that behave linearly, it is easier to get the target (displacement or force), but for non-linear structures one iteration of adjustments was not enough to get the displacement target. Through the techniques of the internal bar force adjustment, the amount of force can be reduced even to the zero, <em>e.g. </em>in case of replacing damaged members.</p> ]]> Adjustment for Shape Restoration and Force Control of Cable Arch Stayed Bridges a.a. manguri a.s.k. kwan n.m. saeed doi: 10.2495/CMEM-V5-N4-514-521 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 514 10.2495/CMEM-V5-N4-514-521 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-514-521 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-504-513 The methodology for the analysis of deployable structures with 2 degrees of freedom (DoF) and optimisation of the deployment sequence is proposed. A parametrically controlled geometry, based on the design of biomimetic deployable structures, is systematically cycled through all available combinations of deployment and analysed for the full range of available motion established by the two DoFs. In other words, structural analysis is carried out for all potential configurations for the 2 DoFs, which act independently from one another. The results are, then, automatically post-processed to give contour plots showing the change in performance criteria such as the force or moment that develops in the struc- ture during deployment. Knowing that the structure needs to deploy from the fully folded to the fully unfolded state, the generation of convex hull profiles allows the selection of the optimum path to reach the fully deployed state based on whatever the governing criteria is deemed to be, such as maximum deployment force, deflection, weight of structure, or in service stresses. <![CDATA[ <p>The methodology for the analysis of deployable structures with 2 degrees of freedom (DoF) and optimisation of the deployment sequence is proposed. A parametrically controlled geometry, based on the design of biomimetic deployable structures, is systematically cycled through all available combinations of deployment and analysed for the full range of available motion established by the two DoFs. In other words, structural analysis is carried out for all potential configurations for the 2 DoFs, which act independently from one another. The results are, then, automatically post-processed to give contour plots showing the change in performance criteria such as the force or moment that develops in the struc- ture during deployment. Knowing that the structure needs to deploy from the fully folded to the fully unfolded state, the generation of convex hull profiles allows the selection of the optimum path to reach the fully deployed state based on whatever the governing criteria is deemed to be, such as maximum deployment force, deflection, weight of structure, or in service stresses.</p> ]]> Optimisation of the Deployment Sequence of 2 DoF Systems g.e. fenci n.g.r. currie doi: 10.2495/CMEM-V5-N4-504-513 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 504 10.2495/CMEM-V5-N4-504-513 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-504-513 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-495-503 This paper presents a method of building deployable network assemblies derived from the single degree of freedom (DoF) over constrained Altmann linkage as a basic module. The method is based on assembling linkages with common links and joints or overlapping with extra R or 2R joints. New loops are emerged with overlapping method. The networks created have a single DoF, are over-constrained and have both fully deployed and folded configurations. The computer-aided models (CAD) are used to demonstrate these derived novel mechanisms. <![CDATA[ <p>This paper presents a method of building deployable network assemblies derived from the single degree of freedom (DoF) over constrained Altmann linkage as a basic module. The method is based on assembling linkages with common links and joints or overlapping with extra R or 2R joints. New loops are emerged with overlapping method. The networks created have a single DoF, are over-constrained and have both fully deployed and folded configurations. The computer-aided models (CAD) are used to demonstrate these derived novel mechanisms.</p> ]]> Design Alternatives of Network of Altmann Linkages f. atarer k. korkmaz g. kiper doi: 10.2495/CMEM-V5-N4-495-503 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 495 10.2495/CMEM-V5-N4-495-503 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-495-503 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-484-494 Reconfigurable systems of hinge-connected beams strengthened through struts and continuous cables, utilize their morphology and cable active members through a synergetic process to enhance structural flexibility, stability and energy efficient transformability. The ‘effective 4-bar’ concept may be applied for the transformation of planar n-bar systems, using a sequence of 1–DOF motion steps through selec-tively locking (n-4) joints of the primary members and actuating the cables, in order to adjust the system’s joints to the desired values during the motion steps involved. The control system includes only two motion actuators located at the structural supports, as well as brakes installed on each individual joint. It performs the reconfiguration sequences through tensioning of one single cable at a time. A numerical investigation presented in the current paper involves four arch systems of 8, 9, 10 and 11-bar linkages with 60/90, 75/75 and 90/60 cm strut lengths on each side of the systems’ circumference. In their initial position, all arch systems have 5.0 m span and 5.35 m height following a quasi-vertical ellipsoid shape. The target configuration of the systems with 4.20 m height corresponds to a quasi-horizontal ellipsoid shape. Different reconfiguration sequences are investigated, in order to achieve the target configuration for each system. The comparative numerical analysis refers to the maximum stresses developed in the members and the required brake torques for each transformation. The analysis provides an insight into the hybrid structural morphology and mechanical characteristics of the mem-bers for optimal implementation of the reconfiguration approach. <![CDATA[ <p>Reconfigurable systems of hinge-connected beams strengthened through struts and continuous cables, utilize their morphology and cable active members through a synergetic process to enhance structural flexibility, stability and energy efficient transformability. The ‘effective 4-bar’ concept may be applied for the transformation of planar n-bar systems, using a sequence of 1–DOF motion steps through selec-tively locking (n-4) joints of the primary members and actuating the cables, in order to adjust the system’s joints to the desired values during the motion steps involved. The control system includes only two motion actuators located at the structural supports, as well as brakes installed on each individual joint. It performs the reconfiguration sequences through tensioning of one single cable at a time. A numerical investigation presented in the current paper involves four arch systems of 8, 9, 10 and 11-bar linkages with 60/90, 75/75 and 90/60 cm strut lengths on each side of the systems’ circumference. In their initial position, all arch systems have 5.0 m span and 5.35 m height following a quasi-vertical ellipsoid shape. The target configuration of the systems with 4.20 m height corresponds to a quasi-horizontal ellipsoid shape. Different reconfiguration sequences are investigated, in order to achieve the target configuration for each system. The comparative numerical analysis refers to the maximum stresses developed in the members and the required brake torques for each transformation. The analysis provides an insight into the hybrid structural morphology and mechanical characteristics of the mem-bers for optimal implementation of the reconfiguration approach.</p> ]]> On the Morphology of Reconfigurable Hybrid Structures Based on the Effective 4-Bar Mechanism m. matheou m.c. phocas e.g. christoforou doi: 10.2495/CMEM-V5-N4-484-494 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 484 10.2495/CMEM-V5-N4-484-494 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-484-494 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-475-483 Reconfigurable structural systems aim at spatial adaptability in respect to changing functional, aesthetic or other architecture-oriented objectives. At the same time, adaptive systems are called to reserve the structure’s load-bearing capacity according to external loading criteria and scenarios. While pantograph structures have proven promising in these critical aspects, bending-active elements discard multiple local hinges and number of members by replacing them with single members of enhanced elastic bending deformability. This soft approach renders the possibility to form complex-, single- or double-curved primary structures from straight or planar members, providing in this respect an alternative frame- work to realize constructions of increased transformability and diversity in forms. The development of hybrid systems composed of bending-active members using secondary cables as means of stability and control, enables adjustability of the systems’ form-found shape and deformation control. In the current paper, a hybrid cable bending active structure is investigated at the level of prototype unit and overall structure. On the horizontal plane, the unit consists of a pair of vertically oriented PTFE lamellas, interconnected at mid-length and deformed in inverse direction to form a curvilinear symmetric shape. Cable and strut elements stabilize the primary elastic members by connecting them at both ends in longitudinal and transverse direction, respectively. The overall structure acquires three arc-like configurations, controlled by the secondary system of cables and struts positioned at the periphery of the primary system’s span. All systems are examined in their form-finding and load-bearing behaviour. <![CDATA[ <p>Reconfigurable structural systems aim at spatial adaptability in respect to changing functional, aesthetic or other architecture-oriented objectives. At the same time, adaptive systems are called to reserve the structure’s load-bearing capacity according to external loading criteria and scenarios. While pantograph structures have proven promising in these critical aspects, bending-active elements discard multiple local hinges and number of members by replacing them with single members of enhanced elastic bending deformability. This soft approach renders the possibility to form complex-, single- or double-curved primary structures from straight or planar members, providing in this respect an alternative frame- work to realize constructions of increased transformability and diversity in forms. The development of hybrid systems composed of bending-active members using secondary cables as means of stability and control, enables adjustability of the systems’ form-found shape and deformation control. In the current paper, a hybrid cable bending active structure is investigated at the level of prototype unit and overall structure. On the horizontal plane, the unit consists of a pair of vertically oriented PTFE lamellas, interconnected at mid-length and deformed in inverse direction to form a curvilinear symmetric shape. Cable and strut elements stabilize the primary elastic members by connecting them at both ends in longitudinal and transverse direction, respectively. The overall structure acquires three arc-like configurations, controlled by the secondary system of cables and struts positioned at the periphery of the primary system’s span. All systems are examined in their form-finding and load-bearing behaviour. </p> ]]> Configuration and Deformation Control of a Hybrid Cable Bending-Active Structure o. kontovourkis m. c. phocas k. c. alexandrou s. frangogiannopoulos doi: 10.2495/CMEM-V5-N4-475-483 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 475 10.2495/CMEM-V5-N4-475-483 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-475-483 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-464-474 Deployable structures can expand and/or contract due to their geometrical, material and mechanical properties. This research proposes a classification of geometry for deployable structures. This classification system applied to structures made with scissor 2 bar can lead to architectural innovation. This is demonstrated in the case study of a new design for surfaces based on scissors 2 bar. Through this case study a form generation method of relative ratios is formulated that can be applied to infinite geometrical arrangements. This geometry classification is an attempt to seek further understanding of the subject of deployable structures. In order to gain a comprehensive understanding of this field, different ways of ordering information are being considered. <![CDATA[ <p>Deployable structures can expand and/or contract due to their geometrical, material and mechanical properties. This research proposes a classification of geometry for deployable structures. This classification system applied to structures made with scissor 2 bar can lead to architectural innovation. This is demonstrated in the case study of a new design for surfaces based on scissors 2 bar. Through this case study a form generation method of relative ratios is formulated that can be applied to infinite geometrical arrangements. This geometry classification is an attempt to seek further understanding of the subject of deployable structures. In order to gain a comprehensive understanding of this field, different ways of ordering information are being considered.</p> ]]> Classification of Geometry for Deployable Structures Used for Innovation: Design of New Surfaces With Scissor 2 Bar, and Form Generation Method of Relative Ratios esther rivas-adrover doi: 10.2495/CMEM-V5-N4-464-474 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 464 10.2495/CMEM-V5-N4-464-474 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-464-474 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-451-463 New technologies and fabrication tools urge us to explore new materials and their potential for integration in architectural construction. One such material, Concrete Canvas, is explored in this paper for its hybrid characteristics that blend fabric and thin-shell tectonics. The potential of Concrete Canvas lies in its ability to modify itself from a flexible fabric that when activated with water becomes a rigid concrete structure. Combined with a digitally controlled workflow of on-site cutting and an iterative material feedback loop, the process can serve as a radical alternative to current concrete formwork fabrication techniques. This paper outlines a prototypical design process that combines a phase-changing material, physical computer simulations, robotic fabrication and scanning technologies on a feedback loop between the digital and the physical that allow for customized, free-form, on-site concrete structures to pop-up without the need of a complex formwork. In this process the architect sets the various parameters based on fabrication techniques and material properties and adjusts them iteratively in the physical and digital model during the ‘popping-up’ process until a balance between material properties, technical requirements and aesthetics is reached, exploring new potentials on digital fabrication processes. The paper outlines the proposed workflow including iterative experiments with robotic cutting of flat patterns, their ‘popping-up’ into 3D concrete shells, and material phase transitions during its forming process. The established feedback loop consisting of geometry scanning, parametric perforation pattern control, computational analysis and simulation, and robotic fabrication is described in detail. The paper concludes by exploring the potential of this process to enable a dialogue between digital architecture and the process of materialization and discusses the implications of this approach in relation to architectural design and fabrication workflows <![CDATA[ <p>New technologies and fabrication tools urge us to explore new materials and their potential for integration in architectural construction. One such material, Concrete Canvas, is explored in this paper for its hybrid characteristics that blend fabric and thin-shell tectonics. The potential of Concrete Canvas lies in its ability to modify itself from a flexible fabric that when activated with water becomes a rigid concrete structure. Combined with a digitally controlled workflow of on-site cutting and an iterative material feedback loop, the process can serve as a radical alternative to current concrete formwork fabrication techniques. This paper outlines a prototypical design process that combines a phase-changing material, physical computer simulations, robotic fabrication and scanning technologies on a feedback loop between the digital and the physical that allow for customized, free-form, on-site concrete structures to pop-up without the need of a complex formwork. In this process the architect sets the various parameters based on fabrication techniques and material properties and adjusts them iteratively in the physical and digital model during the ‘popping-up’ process until a balance between material properties, technical requirements and aesthetics is reached, exploring new potentials on digital fabrication processes. The paper outlines the proposed workflow including iterative experiments with robotic cutting of flat patterns, their ‘popping-up’ into 3D concrete shells, and material phase transitions during its forming process. The established feedback loop consisting of geometry scanning, parametric perforation pattern control, computational analysis and simulation, and robotic fabrication is described in detail. The paper concludes by exploring the potential of this process to enable a dialogue between digital architecture and the process of materialization and discusses the implications of this approach in relation to architectural design and fabrication workflows</p> ]]> Pop-Up Concrete Constructions: Forming Fabric Reinforced Concrete Sheets a. n. vazquez w. jabi doi: 10.2495/CMEM-V5-N4-451-463 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 451 10.2495/CMEM-V5-N4-451-463 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-451-463 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-442-450 In this paper, a novel two-dimensional scissor structure that transforms between concave and convex configurations is presented. The structure is designed by a method of assembling kite or anti-kite loops in the flat configuration. Angulated units are generated from the assembled loops. Finally, a new angulated scissor unit is introduced in order to design the novel scissor structure. <![CDATA[ <p>In this paper, a novel two-dimensional scissor structure that transforms between concave and convex configurations is presented. The structure is designed by a method of assembling kite or anti-kite loops in the flat configuration. Angulated units are generated from the assembled loops. Finally, a new angulated scissor unit is introduced in order to design the novel scissor structure.</p> ]]> A Novel Planar Scissor Structure Transforming Between Concave and Convex Configurations m. yar k. korkmaz g. kiper f. maden y. akgün e. aktas doi: 10.2495/CMEM-V5-N4-442-450 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 442 10.2495/CMEM-V5-N4-442-450 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-442-450 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-432-441 Reciprocally supported element (RSE) lattice honeycomb dome structures have the ability to support considerable loading via their composition of interconnected closed circuits of elements. Distinctively, these dome structures use only three elements in each circuit. To understand the structural behaviour of these RSE lattice domes, a structural modelling investigation was carried out. Global linear elas- tic analysis was considered where the behaviour of the structure under the application of loading on selected elements was monitored. The aim of the modelling was to investigate the influencing factors to monitor for model calibration as well as to compare predicted structural behaviour output with future monitored behaviour in laboratory experiments involving the manufacture and construction of an RSE lattice honeycomb dome structure. The creation of the selected RSE honeycomb lattice structures together with the structural modelling findings are presented and discussed. Predicted displacements and stresses were compared under varying boundary support conditions. The von Mises ductile material failure criterion showing the onset of local yielding is considered. <![CDATA[ <p>Reciprocally supported element (RSE) lattice honeycomb dome structures have the ability to support considerable loading via their composition of interconnected closed circuits of elements. Distinctively, these dome structures use only three elements in each circuit. To understand the structural behaviour of these RSE lattice domes, a structural modelling investigation was carried out. Global linear elas- tic analysis was considered where the behaviour of the structure under the application of loading on selected elements was monitored. The aim of the modelling was to investigate the influencing factors to monitor for model calibration as well as to compare predicted structural behaviour output with future monitored behaviour in laboratory experiments involving the manufacture and construction of an RSE lattice honeycomb dome structure. The creation of the selected RSE honeycomb lattice structures together with the structural modelling findings are presented and discussed. Predicted displacements and stresses were compared under varying boundary support conditions. The von Mises ductile material failure criterion showing the onset of local yielding is considered.</p> ]]> Structural Modelling Investigation of Reciprocally Supported Element Lattice Honeycomb Domes j.p. rizzuto doi: 10.2495/CMEM-V5-N4-432-441 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 432 10.2495/CMEM-V5-N4-432-441 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-432-441 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-421-431 Since their earliest conceptualization, structures with reconfigurable characteristics contributed to the emergence of an architecture, able to respond and adjust itself to shifting environmental conditions, or time dependent users’ needs. In this respect, the development of tensegrity and scissor-like structures to obtain adaptive capabilities, is primarily based on articulated joints and embedded mechanical actuators, following a hard mechanical approach. Although these systems are usually designed to use a small number of components to achieve maximum shape adjustments, their implementation often causes an increase of unsustainable processes with regard to the number and characteristics of the actuators used and mechanisms complexity, as well as energy-inefficient processes, in terms of both construction and kinetic operation. An alternative soft approach for adaptive structures is proposed in the current paper through an implementation of hybrid cable bending-active members, while the latter replaces multiple local hinges through reversible elastic bending deformations. Through the cables own length modification, these are responsible for the structure deformability and sufficient prestressing of the primary elastic members. Such pliable structures increase the level of design complexity due to the inherent elastic properties of the materials used and their nonlinear structural behaviour during transformation. In demonstrating this, a series of single, coupled and coupled-interconnected cable bending-active system configurations are investigated. Results obtained describe the stress distribution between the structural components during the systems’ form-finding process and load-bearing behaviour. <![CDATA[ <p>Since their earliest conceptualization, structures with reconfigurable characteristics contributed to the emergence of an architecture, able to respond and adjust itself to shifting environmental conditions, or time dependent users’ needs. In this respect, the development of tensegrity and scissor-like structures to obtain adaptive capabilities, is primarily based on articulated joints and embedded mechanical actuators, following a hard mechanical approach. Although these systems are usually designed to use a small number of components to achieve maximum shape adjustments, their implementation often causes an increase of unsustainable processes with regard to the number and characteristics of the actuators used and mechanisms complexity, as well as energy-inefficient processes, in terms of both construction and kinetic operation. An alternative soft approach for adaptive structures is proposed in the current paper through an implementation of hybrid cable bending-active members, while the latter replaces multiple local hinges through reversible elastic bending deformations. Through the cables own length modification, these are responsible for the structure deformability and sufficient prestressing of the primary elastic members. Such pliable structures increase the level of design complexity due to the inherent elastic properties of the materials used and their nonlinear structural behaviour during transformation. In demonstrating this, a series of single, coupled and coupled-interconnected cable bending-active system configurations are investigated. Results obtained describe the stress distribution between the structural components during the systems’ form-finding process and load-bearing behaviour. </p> ]]> Adaptive Structures – Soft Mechanical Approach m.c. phocas k.c. alexandrou doi: 10.2495/CMEM-V5-N4-421-431 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 421 10.2495/CMEM-V5-N4-421-431 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-421-431 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-0 Structures that move in the course of normal use, or which have to be assembled or erected rapidly on a relatively unprepared site, offer a particular challenge to the designer. The interaction between the structure and the mechanism by which it moves is essential in these cases. The speed of assembly, and what this means in terms of logistics, materials and cost, is a major factor in many such structures. Mobile and rapidly assembled structures play a major role in disaster mitigation and temporary accommodation. They are of primary importance in many military as well as civilian applications and are widely used for rescue and maintenance services. Their importance continues to grow in contemporary society where speed of response is of primary importance. There are problems such as the efficient design of assembly joints, the resistance to damage of the membrane and metal cladding, crashworthiness and the limits of serviceability. Some areas of the subject are already well documented, but knowledge is fragmented and there is little design guidance available in the form of textbooks, data sheets or codes of practice. The interaction between morphology, kinematic behaviour and structural performance – typical of these structures – poses real challenges in terms of design and successful realisation. This Special Issue contains selected papers presented at the International Conference on Mobile, Adaptive and Rapidly Assembled Structures which took place at La Certosa di Pontignano near Siena, Italy. The meeting was sponsored by the Free University of Brussels and The Wessex Institute, UK to highlight major developments that have recently taken place in this exciting field. <![CDATA[ <p>Structures that move in the course of normal use, or which have to be assembled or erected rapidly on a relatively unprepared site, offer a particular challenge to the designer. The interaction between the structure and the mechanism by which it moves is essential in these cases. The speed of assembly, and what this means in terms of logistics, materials and cost, is a major factor in many such structures. Mobile and rapidly assembled structures play a major role in disaster mitigation and temporary accommodation. They are of primary importance in many military as well as civilian applications and are widely used for rescue and maintenance services. Their importance continues to grow in contemporary society where speed of response is of primary importance. There are problems such as the efficient design of assembly joints, the resistance to damage of the membrane and metal cladding, crashworthiness and the limits of serviceability. Some areas of the subject are already well documented, but knowledge is fragmented and there is little design guidance available in the form of textbooks, data sheets or codes of practice. The interaction between morphology, kinematic behaviour and structural performance – typical of these structures – poses real challenges in terms of design and successful realisation. This Special Issue contains selected papers presented at the International Conference on Mobile, Adaptive and Rapidly Assembled Structures which took place at La Certosa di Pontignano near Siena, Italy. The meeting was sponsored by the Free University of Brussels and The Wessex Institute, UK to highlight major developments that have recently taken place in this exciting field.</p> ]]> Preface niels de temmerman carlos a. brebbia doi: 10.2495/CMEM-V5-N4-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2017 5 4 Article 0 10.2495/CMEM-V5-N4-0 https://www.acadlore.com/article/IJCMEM/2017_5_4/CMEM-V5-N4-0 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-404-414 The boundary element method (BEM) is a widely used engineering tool in acoustics. The major disadvantage of the three-dimensional boundary element method (3D-BEM) is its computational cost, which increases with the size of the simulated obstacle and the simulated wave number. Thus, the geometrical details of the obstacle and the simulated frequency range are limited by computer speed and memory. The computational cost for simulating large obstacles like noise barriers is often reduced by applying the two-dimensional boundary element method (2D-BEM) on three-dimensional obstacles. However, the 2D-BEM limits the geometry of the boundary to obstacles with a one-dimensionally constant profile. An interesting compromise solution between the 2D-BEM and the 3D-BEM is the quasi-periodic boundary element method (QP-BEM). The QP-BEM allows the simulation of periodically repetitive complex three-dimensional structures and periodic sound fields while keeping the computational cost at a reasonable level. In this study, first, the QP-BEM was implemented and coupled with the fast multipole method. Second, the QP-BEM was used to simulate the sound field radiated by a simple geometric object, i.e., a uniformly vibrating cylinder. Results were compared to an analytic solution, for the evaluation of the numerical accuracy of our QP-BEM implementation. For the demonstration of some use cases, third, the QP-BEM was used to simulate the sound field scattered by a sonic crystal noise barrier and a noise- barrier top element. 03-31-2017 <![CDATA[ <p>The boundary element method (BEM) is a widely used engineering tool in acoustics. The major disadvantage of the three-dimensional boundary element method (3D-BEM) is its computational cost, which increases with the size of the simulated obstacle and the simulated wave number. Thus, the geometrical details of the obstacle and the simulated frequency range are limited by computer speed and memory. The computational cost for simulating large obstacles like noise barriers is often reduced by applying the two-dimensional boundary element method (2D-BEM) on three-dimensional obstacles. However, the 2D-BEM limits the geometry of the boundary to obstacles with a one-dimensionally constant profile. An interesting compromise solution between the 2D-BEM and the 3D-BEM is the quasi-periodic boundary element method (QP-BEM). The QP-BEM allows the simulation of periodically repetitive complex three-dimensional structures and periodic sound fields while keeping the computational cost at a reasonable level. In this study, first, the QP-BEM was implemented and coupled with the fast multipole method. Second, the QP-BEM was used to simulate the sound field radiated by a simple geometric object, i.e., a uniformly vibrating cylinder. Results were compared to an analytic solution, for the evaluation of the numerical accuracy of our QP-BEM implementation. For the demonstration of some use cases, third, the QP-BEM was used to simulate the sound field scattered by a sonic crystal noise barrier and a noise- barrier top element.</p> ]]> The Three-Dimensional Quasi-Periodic Boundary Element Method: Implementation, Evaluation, and Use Cases h. ziegelwanger p. reiter m. conter doi: 10.2495/CMEM-V5-N3-404-414 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 404 10.2495/CMEM-V5-N3-404-414 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-404-414 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-395-403 The Dual Reciprocity BEM (DRBEM) and the Time-Dependent BEM (TDBEM) are considered in the context of radiative and time-dependent thermal transport, respectively. In order to achieve sensible solution times for realistic 3D problems with large meshes, a range of optimisation techniques are considered, and a number of parallelisation techniques applied: shared memory using multi-core threading, Graphics Processing Unit (GPU) acceleration using CUDA, and distributed memory on a high performance cluster using MPI. Particular consideration is given to practical methods to invert large dense matrices. 03-31-2017 <![CDATA[ <p>The Dual Reciprocity BEM (DRBEM) and the Time-Dependent BEM (TDBEM) are considered in the context of radiative and time-dependent thermal transport, respectively. In order to achieve sensible solution times for realistic 3D problems with large meshes, a range of optimisation techniques are considered, and a number of parallelisation techniques applied: shared memory using multi-core threading, Graphics Processing Unit (GPU) acceleration using CUDA, and distributed memory on a high performance cluster using MPI. Particular consideration is given to practical methods to invert large dense matrices.</p> ]]> Parallelisation Techniques for the Dual Reciprocity and Time-Dependent Boundary Element Method Algorithms tim bashford kelvin donne arnaud marotin ala al-hussany doi: 10.2495/CMEM-V5-N3-395-403 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 395 10.2495/CMEM-V5-N3-395-403 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-395-403 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-387-394 In boundary element method (BEM), one encounters linear system with a dense and non-symmetric square matrix which might be so large that inverting the linear system is too prohibitive in terms of cpu time and/or memory. Each usual powerful treatment (Fast Multipole Method, H-matrices) developed to deal with this issue is optimized to efficiently perform matrix vector products. This work presents a new technique to adequately and quickly handle such products: the Sparse Cardinal Sine Decomposition. This approach, recently pioneered for the Laplace and Helmholtz equations, rests on the decomposition of each encountered kernel as series of radial Cardinal Sine functions. Here, we achieve this decompo- sition for the Stokes problem and implement it in MyBEM, a new fast solver for multi-physical BEM. The reported computational examples permit us to compare the advocated method against a usual BEM in terms of both accuracy and convergence. 03-31-2017 <![CDATA[ <p>In boundary element method (BEM), one encounters linear system with a dense and non-symmetric square matrix which might be so large that inverting the linear system is too prohibitive in terms of cpu time and/or memory. Each usual powerful treatment (Fast Multipole Method, H-matrices) developed to deal with this issue is optimized to efficiently perform matrix vector products. This work presents a new technique to adequately and quickly handle such products: the Sparse Cardinal Sine Decomposition. This approach, recently pioneered for the Laplace and Helmholtz equations, rests on the decomposition of each encountered kernel as series of radial Cardinal Sine functions. Here, we achieve this decompo- sition for the Stokes problem and implement it in MyBEM, a new fast solver for multi-physical BEM. The reported computational examples permit us to compare the advocated method against a usual BEM in terms of both accuracy and convergence.</p> ]]> Application of the Sparse Cardinal Sine decomposition to 3D Stokes Flows f. alouges m. aussal a. lefebvre-lepot f. pigeonneau a. sellier doi: 10.2495/CMEM-V5-N3-387-394 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 387 10.2495/CMEM-V5-N3-387-394 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-387-394 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-377-386 In this paper, we apply the recently proposed fast block-greedy algorithm to a convergent kernel-based collocation method. In particular, we discretize three-dimensional second-order elliptic differential equations by the meshless asymmetric collocation method with over-sampling. Approximated solutions are obtained by solving the resulting weighted least squares problem. Such formulation has been proven to have optimal convergence in H2. Our aim is to investigate the convergence behaviour of some three dimensional test problems. We also study the low-rank solution by restricting the approximation in some smaller trial subspaces. A block-greedy algorithm, which costs at most O(NK2) to select K columns (or trial centers) out of an M × N overdetermined matrix, is employed for such an adaptivity. Numerical simulations are provided to justify these reductions. 03-31-2017 <![CDATA[ <p>In this paper, we apply the recently proposed fast block-greedy algorithm to a convergent kernel-based collocation method. In particular, we discretize three-dimensional second-order elliptic differential equations by the meshless asymmetric collocation method with over-sampling. Approximated solutions are obtained by solving the resulting weighted least squares problem. Such formulation has been proven to have optimal convergence in H2. Our aim is to investigate the convergence behaviour of some three dimensional test problems. We also study the low-rank solution by restricting the approximation in some smaller trial subspaces. A block-greedy algorithm, which costs at most O(NK2) to select K columns (or trial centers) out of an M × N overdetermined matrix, is employed for such an adaptivity. Numerical simulations are provided to justify these reductions.</p> ]]> Convergence Studies for an Adaptive Meshless Least-Squares Collocation Method ka chun cheung leevan ling doi: 10.2495/CMEM-V5-N3-377-386 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 377 10.2495/CMEM-V5-N3-377-386 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-377-386 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-369-376 This article addresses a specific type of boundary conditions in plane elastic boundary value problems, BVP. An elastic plane composed of two dissimilar isotropic materials is considered. It is assumed that the displacement vector orientations are known on both sides of the contour that separates the entire plane into interior and exterior domains. The stress vector is assumed to be continuous across the contour. The aim of this study is the investigation of solvability of this BVP and the development of appropriate numerical methods for solving the corresponding singular integral equation. The latter is necessary as the integral equation is homogeneous. It is shown that depending on the behaviour of the displacement vector orientations the solution of the problem may include a certain number of arbitrary linear parameters. A numerical approach is proposed based on the solution of the homogeneous Riemann BVP to form a non-homogeneous right hand side of the integral equation. 03-31-2017 <![CDATA[ <p>This article addresses a specific type of boundary conditions in plane elastic boundary value problems, BVP. An elastic plane composed of two dissimilar isotropic materials is considered. It is assumed that the displacement vector orientations are known on both sides of the contour that separates the entire plane into interior and exterior domains. The stress vector is assumed to be continuous across the contour. The aim of this study is the investigation of solvability of this BVP and the development of appropriate numerical methods for solving the corresponding singular integral equation. The latter is necessary as the integral equation is homogeneous. It is shown that depending on the behaviour of the displacement vector orientations the solution of the problem may include a certain number of arbitrary linear parameters. A numerical approach is proposed based on the solution of the homogeneous Riemann BVP to form a non-homogeneous right hand side of the integral equation.</p> ]]> On Solvability of the BVP Formulated in Terms of Displacement Orientations on the Interface Between Dissimilar Elastic Materials a.n. galybin doi: 10.2495/CMEM-V5-N3-369-376 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 369 10.2495/CMEM-V5-N3-369-376 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-369-376 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-359-368 Velocity-pressure coupling schemes for the solution of incompressible fluid flow problems in Computational Fluid Dynamics (CFD) rely on the formulation of Poisson-like equations through projection methods. The solution of these Poisson-like equations represent the pressure correction and the velocity correction to ensure proper satisfaction of the conservation of mass equation at each step of a time-marching scheme or at each level of an iteration process. Inaccurate solutions of these Poisson-like equations result in meaningless instantaneous or intermediate approximations that do not represent the proper time-accurate behavior of the flow. The fact that these equations must be solved to convergence at every step of the overall solution process introduces a major bottleneck for the efficiency of the method. We present a formulation that achieves high levels of accuracy and efficiency by properly solving the Poisson equations at each step of the solution process by formulating a Localized RBF Collocation Meshless Method (LRC-MM) solution approach for the approxima- tion of the diffusive and convective derivatives while employing the same framework to implement a Dual-Reciprocity Boundary Element Method (DR-BEM) for the solution of the ensuing Poisson equations. The same boundary discretization and point distribution employed in the LRC-MM is used for the DR-BEM. The methodology is implemented and tested in the solution of a backward- facing step problem. 03-31-2017 <![CDATA[ <p>Velocity-pressure coupling schemes for the solution of incompressible fluid flow problems in Computational Fluid Dynamics (CFD) rely on the formulation of Poisson-like equations through projection methods. The solution of these Poisson-like equations represent the pressure correction and the velocity correction to ensure proper satisfaction of the conservation of mass equation at each step of a time-marching scheme or at each level of an iteration process. Inaccurate solutions of these Poisson-like equations result in meaningless instantaneous or intermediate approximations that do not represent the proper time-accurate behavior of the flow. The fact that these equations must be solved to convergence at every step of the overall solution process introduces a major bottleneck for the efficiency of the method. We present a formulation that achieves high levels of accuracy and efficiency by properly solving the Poisson equations at each step of the solution process by formulating a Localized RBF Collocation Meshless Method (LRC-MM) solution approach for the approxima- tion of the diffusive and convective derivatives while employing the same framework to implement a Dual-Reciprocity Boundary Element Method (DR-BEM) for the solution of the ensuing Poisson equations. The same boundary discretization and point distribution employed in the LRC-MM is used for the DR-BEM. The methodology is implemented and tested in the solution of a backward- facing step problem.</p> ]]> A Coupled Localized RBF Meshless/Drbem Formulation for Accurate Modeling of Incompressible Fluid Flows leonardo a. bueno eduardo a. divo alain j. kassab doi: 10.2495/CMEM-V5-N3-359-368 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 359 10.2495/CMEM-V5-N3-359-368 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-359-368 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-348-358 The objective of this article is to develop a boundary element numerical model to solve coupled problems involving heat energy diffusion, convection and radiation in a participating medium. In this study, the contributions from radiant energy transfer are presented using two approaches for optical thick fluids: the Rosseland diffusion approximation and the P1 approximation. The governing Navier– Stokes equations are written in the velocity–vorticity formulation for the kinematics and kinetics of the fluid motion. The approximate numerical solution algorithm is based on a boundary element numerical model in its macro-element formulation. Validity of the proposed implementation is tested on a one-dimensional test case using a grey participating medium at radiative equilibrium between two isothermal black surfaces. 03-31-2017 <![CDATA[ <p>The objective of this article is to develop a boundary element numerical model to solve coupled problems involving heat energy diffusion, convection and radiation in a participating medium. In this study, the contributions from radiant energy transfer are presented using two approaches for optical thick fluids: the Rosseland diffusion approximation and the P1 approximation. The governing Navier– Stokes equations are written in the velocity–vorticity formulation for the kinematics and kinetics of the fluid motion. The approximate numerical solution algorithm is based on a boundary element numerical model in its macro-element formulation. Validity of the proposed implementation is tested on a one-dimensional test case using a grey participating medium at radiative equilibrium between two isothermal black surfaces.</p> ]]> Implementation of the Rosseland and the P1 Radiation Models in the System of Navier-Stokes Equations with the Boundary Element Method crnjac, p. škerget, l. ravnik, j. hriberšek, m. doi: 10.2495/CMEM-V5-N3-348-358 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 348 10.2495/CMEM-V5-N3-348-358 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-348-358 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-337-347 In this paper, we derive a boundary-domain integral formulation for the energy transport equation under the assumption that the fluid properties, through which the energy is transported by diffusion and convection, are spatially and temporally changing. The energy transport equation is a second-order partial differential equation of a diffusion-convection type, with the fluid temperature as the independent variable. The presented formulation does not require a calculation of the temperature gradient, thus it is, for a known fluid velocity field, linear.The final boundary-domain integral equation is discretized using a domain decomposition approach, where the equation is solved on each sub-domain, while subdomains are joined by compatibility conditions. The validity of the method is checked using several analytical examples. Convergence properties are studied yielding that the proposed discretization technique is second-order accurate.The developed method is used to simulate flow and heat transfer of nanofluids, which exhibit properties that depend on the solid particle concentration. A Lagrange-Euler approach is used. 03-31-2017 <![CDATA[ <p>In this paper, we derive a boundary-domain integral formulation for the energy transport equation under the assumption that the fluid properties, through which the energy is transported by diffusion and convection, are spatially and temporally changing. The energy transport equation is a second-order partial differential equation of a diffusion-convection type, with the fluid temperature as the independent variable. The presented formulation does not require a calculation of the temperature gradient, thus it is, for a known fluid velocity field, linear.</p><p>The final boundary-domain integral equation is discretized using a domain decomposition approach, where the equation is solved on each sub-domain, while subdomains are joined by compatibility conditions. The validity of the method is checked using several analytical examples. Convergence properties are studied yielding that the proposed discretization technique is second-order accurate.</p><p>The developed method is used to simulate flow and heat transfer of nanofluids, which exhibit properties that depend on the solid particle concentration. A Lagrange-Euler approach is used. </p><p></p> ]]> Solution of Energy Transport Equation with Variable Material Properties by BEM ravnik, j. skerget, l. tibaut, j yeigh, b.w. doi: 10.2495/CMEM-V5-N3-337-347 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 337 10.2495/CMEM-V5-N3-337-347 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-337-347 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-329-336 This paper is focused on the analysis of the numerical solution of flow problems in irregular domains. The numerical approach is based on the weighted least squares (WLS) approximation constructed over the local support domain, i.e. a sub cluster of computational nodes, to evaluate partial differential operators, in our case spatial derivatives up to second order. There are several possibilities for elegant formulation as well as computer implementation of such method, which are first and foremost consequence of the fact that the node has to be aware only of the distance to other nodes, i.e. no topological relation between nodes is required. The presented meshless approach is applied on the lid-driven cavity problem in randomly generated domain. It is demonstrated that using adequately wide support domains, i.e. enough support nodes with a proper weighting, provide stable results even in highly deformed domains, however, at the cost of the accuracy and computational complexity, especially in cases when the support domain changes during the computation. The optimal meshless configuration, i.e. support of 15 nodes weighted with Gaussian weight function and monomials up to second order as basis, is suggested based on experimental analyses. The results are presented in terms of comparison with already published data on regular nodal distributions, convergence analysis on regular nodal distribution and stability analysis of the solution with respect to the level of nodal irregularity and local support size. 03-31-2017 <![CDATA[ <p>This paper is focused on the analysis of the numerical solution of flow problems in irregular domains. The numerical approach is based on the weighted least squares (WLS) approximation constructed over the local support domain, i.e. a sub cluster of computational nodes, to evaluate partial differential operators, in our case spatial derivatives up to second order. There are several possibilities for elegant formulation as well as computer implementation of such method, which are first and foremost consequence of the fact that the node has to be aware only of the distance to other nodes, i.e. no topological relation between nodes is required. The presented meshless approach is applied on the lid-driven cavity problem in randomly generated domain. It is demonstrated that using adequately wide support domains, i.e. enough support nodes with a proper weighting, provide stable results even in highly deformed domains, however, at the cost of the accuracy and computational complexity, especially in cases when the support domain changes during the computation. The optimal meshless configuration, i.e. support of 15 nodes weighted with Gaussian weight function and monomials up to second order as basis, is suggested based on experimental analyses. The results are presented in terms of comparison with already published data on regular nodal distributions, convergence analysis on regular nodal distribution and stability analysis of the solution with respect to the level of nodal irregularity and local support size. </p> ]]> Stability Analysis of a Meshless Method in Irregular Nodal Distributions for Flow Problems kosec, g doi: 10.2495/CMEM-V5-N3-329-336 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 329 10.2495/CMEM-V5-N3-329-336 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-329-336 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-317-328 In this paper we consider vibrations of the baffled elastic fuel tank partially filled with a liquid. The compound shell was a simplified model of a fuel tank. The shell is considered to be thin and the Kirchhoff–Love linear theory hypotheses are applied. The liquid is supposed to be an ideal and incompressible one and its flow introduced by the vibrations of a shell is irrotational. The problem of the fluid-structure interaction was solved using the reduced boundary and finite element methods. The tank structure was modeled by the FEM and the liquid sloshing in a fluid domain was described by using the multi-domain BEM. The rigid and elastic baffled tanks of different forms were considered. The dependencies of frequencies via the filling level were obtained numerically for vibrations of the fluid-filled tanks with and without baffles. 03-31-2017 <![CDATA[ <p>In this paper we consider vibrations of the baffled elastic fuel tank partially filled with a liquid. The compound shell was a simplified model of a fuel tank. The shell is considered to be thin and the Kirchhoff–Love linear theory hypotheses are applied. The liquid is supposed to be an ideal and incompressible one and its flow introduced by the vibrations of a shell is irrotational. The problem of the fluid-structure interaction was solved using the reduced boundary and finite element methods. The tank structure was modeled by the FEM and the liquid sloshing in a fluid domain was described by using the multi-domain BEM. The rigid and elastic baffled tanks of different forms were considered. The dependencies of frequencies via the filling level were obtained numerically for vibrations of the fluid-filled tanks with and without baffles.</p> ]]> BEM and FEM Analysis of the Fluid-Structure Interaction in Tanks with Baffles gnitko, v. degtyariov, k naumenko, v. strelnikova, e. podgorny, a.n. doi: 10.2495/CMEM-V5-N3-317-328 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 317 10.2495/CMEM-V5-N3-317-328 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-317-328 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-306-316 In this paper, we present briefly the derivation of the equations of motion and boundary conditions for elastic plates with functionally graded Young’s modulus and mass density of the plate subjected to transversal transient dynamic loads. The unified formulation is derived for three plate bending theories, such as the Kirchhoff–Love theory (KLT) for bending of thin elastic plates and the shear deformation plate theories (the first order – FSDPT, and the third order – TSDPT). It is shown that the transversal gradation of Young’s modulus gives rise to coupling between the bending and in-plane deformation modes in plates subject to transversal loading even in static problems. In dynamic problems, there are also the inertial coupling terms. The influence of the gradation of material coef- ficients on bending and in-plane deformation modes with including coupling is studied in numerical experiments with consideration of Heaviside impact loading as well as Heaviside pulse loading. To decrease the order of the derivatives in the coupled PDE with variable coefficients, the decomposition technique is employed. The element-free strong formulation with using meshless approximations for spatial variation of field variables is developed and the discretized ordinary differential equations with respect to time variable are solved by using time stepping techniques. The attention is paid to the stability of numerical solutions. Several numerical results are presented for illustration of the coupling effects in bending of elastic FGM (Functionally Graded Material) plates. The role of the thickness and shear deformations is studied via numerical simulations by comparison of the plate response in three plate bending theories. 03-31-2017 <![CDATA[ <p>In this paper, we present briefly the derivation of the equations of motion and boundary conditions for elastic plates with functionally graded Young’s modulus and mass density of the plate subjected to transversal transient dynamic loads. The unified formulation is derived for three plate bending theories, such as the Kirchhoff–Love theory (KLT) for bending of thin elastic plates and the shear deformation plate theories (the first order – FSDPT, and the third order – TSDPT). It is shown that the transversal gradation of Young’s modulus gives rise to coupling between the bending and in-plane deformation modes in plates subject to transversal loading even in static problems. In dynamic problems, there are also the inertial coupling terms. The influence of the gradation of material coef- ficients on bending and in-plane deformation modes with including coupling is studied in numerical experiments with consideration of Heaviside impact loading as well as Heaviside pulse loading. To decrease the order of the derivatives in the coupled PDE with variable coefficients, the decomposition technique is employed. The element-free strong formulation with using meshless approximations for spatial variation of field variables is developed and the discretized ordinary differential equations with respect to time variable are solved by using time stepping techniques. The attention is paid to the stability of numerical solutions. Several numerical results are presented for illustration of the coupling effects in bending of elastic FGM (Functionally Graded Material) plates. The role of the thickness and shear deformations is studied via numerical simulations by comparison of the plate response in three plate bending theories.</p> ]]> Simulations of Coupling Effects in Vibration of FGM Plates by Mesh-Free Methods sladek, v. sator, l. sladek, j. doi: 10.2495/CMEM-V5-N3-306-316 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 306 10.2495/CMEM-V5-N3-306-316 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-306-316 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-293-305 The vibration behaviour of ships is noticeably influenced by the surrounding water, which represents a fluid of high density. In this case, the feedback of the fluid pressure onto the structure cannot be neglected and a strong coupling scheme between the fluid domain and the structural domain is necessary. In this work, fast boundary element methods (BEMs) are used to model the semi-infinite fluid domain with the free water surface. Two approaches are compared: A symmetric mixed formulation is applied where a part of the water surface is discretized. The second approach is a formulation with a special half-space fundamental solution, which allows the exact representation of the Dirichlet boundary condition on the free water surface without its discretization. Furthermore, the influence of the compressibility of the water is investigated by comparing the solutions of the Helmholtz and the Laplace equation. The ship itself is modeled with the finite element method (FEM). A binary interface to the commercial finite element package ANSYS is used to import the mass matrix and the stiffness matrix. The coupled problems are formulated using Schur complements. To solve the resulting sys- tem of equations, a combination of a direct solver for the finite element matrix and a preconditioned GMRES for the overall Schur complement is chosen. The applicability of the approach is demonstrated using a realistic model problem. 03-31-2017 <![CDATA[ <p>The vibration behaviour of ships is noticeably influenced by the surrounding water, which represents a fluid of high density. In this case, the feedback of the fluid pressure onto the structure cannot be neglected and a strong coupling scheme between the fluid domain and the structural domain is necessary. In this work, fast boundary element methods (BEMs) are used to model the semi-infinite fluid domain with the free water surface. Two approaches are compared: A symmetric mixed formulation is applied where a part of the water surface is discretized. The second approach is a formulation with a special half-space fundamental solution, which allows the exact representation of the Dirichlet boundary condition on the free water surface without its discretization. Furthermore, the influence of the compressibility of the water is investigated by comparing the solutions of the Helmholtz and the Laplace equation. The ship itself is modeled with the finite element method (FEM). A binary interface to the commercial finite element package ANSYS is used to import the mass matrix and the stiffness matrix. The coupled problems are formulated using Schur complements. To solve the resulting sys- tem of equations, a combination of a direct solver for the finite element matrix and a preconditioned GMRES for the overall Schur complement is chosen. The applicability of the approach is demonstrated using a realistic model problem.</p> ]]> Acoustic Fluid–Structure Interaction of Ships by Coupled Fast BE–FE Approaches gaul, l brunner, d. junge, m. doi: 10.2495/CMEM-V5-N3-293-305 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 293 10.2495/CMEM-V5-N3-293-305 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-293-305 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-281-292 In recent years significant focus has been given to the study of Radial basis functions (RBF), especially in their use on solving partial differential equations (PDE). RBF have an impressive capability of inter- polating scattered data, even when this data presents localized discontinuities. However, for infinitely smooth RBF such as the Multiquadrics, inverse Multiquadrics, and Gaussian, the shape parameter must be chosen properly to obtain accurate approximations while avoiding ill-conditioning of the interpolating matrices. The optimum shape parameter can vary significantly depending on the field, particularly in locations of steep gradients, shocks, or discontinuities. Typically, the shape parameter is chosen to be high value to render flatter RBF therefore yielding a high condition number for the ensuing interpola- tion matrix. However, this optimization strategy fails for problems that present steep gradients, shocks or discontinuities. Instead, in such cases, the optimal interpolation occurs when the shape parameter is chosen to be low in order to render steeper RBF therefore yielding low condition number for the interpolation matrix. The focus of this work is to demonstrate the use of RBF interpolation to capture the behaviour of steep gradients and shocks by implementing a blending scheme that combines high and low shape parameters. A formulation of the RBF blending interpolation scheme along with test- ing and validation through its implementation in the solution of the Burger’s linear advection equation and compressible Euler equations using a Localized RBF Collocation Meshless Method (LRC-MM) is presented in this paper. 03-31-2017 <![CDATA[ <p>In recent years significant focus has been given to the study of Radial basis functions (RBF), especially in their use on solving partial differential equations (PDE). RBF have an impressive capability of inter- polating scattered data, even when this data presents localized discontinuities. However, for infinitely smooth RBF such as the Multiquadrics, inverse Multiquadrics, and Gaussian, the shape parameter must be chosen properly to obtain accurate approximations while avoiding ill-conditioning of the interpolating matrices. The optimum shape parameter can vary significantly depending on the field, particularly in locations of steep gradients, shocks, or discontinuities. Typically, the shape parameter is chosen to be high value to render flatter RBF therefore yielding a high condition number for the ensuing interpola- tion matrix. However, this optimization strategy fails for problems that present steep gradients, shocks or discontinuities. Instead, in such cases, the optimal interpolation occurs when the shape parameter is chosen to be low in order to render steeper RBF therefore yielding low condition number for the interpolation matrix. The focus of this work is to demonstrate the use of RBF interpolation to capture the behaviour of steep gradients and shocks by implementing a blending scheme that combines high and low shape parameters. A formulation of the RBF blending interpolation scheme along with test- ing and validation through its implementation in the solution of the Burger’s linear advection equation and compressible Euler equations using a Localized RBF Collocation Meshless Method (LRC-MM) is presented in this paper. </p><p> </p> ]]> An RBF Interpolation Blending Scheme for Effective Shock-Capturing harris, m. kassab, a divo, e. doi: 10.2495/CMEM-V5-N3-281-292 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 281 10.2495/CMEM-V5-N3-281-292 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-281-292 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-271-280 The corrosion electric field around the surface of stainless steel under tensile stress is addressed through the experiment and simulation. When the stress is applied, the passive film is locally damaged on the grain boundaries causing microscopic stress and strain concentrations. In a corrosive environment, the plastic strain induced by the strain concentration breaks the passive film and generates a new surface without the passive film. This causes a galvanic corrosion between the intact surface with passive film and the damaged surface without passive film. The effect of stress on the polarization curve was observed by electrochemical and mechanical experiments, and we found that the spontaneous potential decreased as the applied stress increased. To evaluate the electrochemical property of stressed stainless steel, the electric field analysis is formulated by the boundary element method (BEM) with the damaged passive film model and the empirical polarization curve model. 03-31-2017 <![CDATA[ <p>The corrosion electric field around the surface of stainless steel under tensile stress is addressed through the experiment and simulation. When the stress is applied, the passive film is locally damaged on the grain boundaries causing microscopic stress and strain concentrations. In a corrosive environment, the plastic strain induced by the strain concentration breaks the passive film and generates a new surface without the passive film. This causes a galvanic corrosion between the intact surface with passive film and the damaged surface without passive film. The effect of stress on the polarization curve was observed by electrochemical and mechanical experiments, and we found that the spontaneous potential decreased as the applied stress increased. To evaluate the electrochemical property of stressed stainless steel, the electric field analysis is formulated by the boundary element method (BEM) with the damaged passive film model and the empirical polarization curve model.</p><p> </p> ]]> Electrostatic Corrosion Analysis with Damaged Passive Film Model of Stainless Steel kuwazuru, o ode, k. liu, w. doi: 10.2495/CMEM-V5-N3-271-280 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 271 10.2495/CMEM-V5-N3-271-280 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-271-280 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-260-270 A time-dependent fully-parallelised formulation of the BEM is applied to transient thermal problems in the context of light-based medical devices. The method is initially verified against benchmark problems. The limitations of the model are discussed, particularly the singularity challenge inherent in the fundamental solution. The method is then applied for a representative 3D clinical problem, further illustrating the singularity challenge. 03-31-2017 <![CDATA[ <p>A time-dependent fully-parallelised formulation of the BEM is applied to transient thermal problems in the context of light-based medical devices. The method is initially verified against benchmark problems. The limitations of the model are discussed, particularly the singularity challenge inherent in the fundamental solution. The method is then applied for a representative 3D clinical problem, further illustrating the singularity challenge.</p> ]]> Solution of the Transient Thermal Diffusion Equation Using the Time-Dependent Boundary Element Method donne, k.e. marotin, a. bashford, t. doi: 10.2495/CMEM-V5-N3-260-270 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 260 10.2495/CMEM-V5-N3-260-270 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-260-270 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-250-259 The paper reviews the influence of the variability in the morphology and the tissue properties of the human brain and eye, respectively, exposed to high-frequency (HF) radiation. Deterministic-stochastic modeling enables one to estimate the effects of the parameter uncertainties on the maximum induced electric field and Specific Absorption Rate (SAR). Surface Integral Equation (SIE) scheme applied to the brain exposed to HF radiation and hybrid boundary element method (BEM)/finite element method (FEM) scheme used to handle the eye exposure to HF radiation are discussed.Furthermore, a simple stochastic collocation (SC), through which the relevant parameter uncertainties are taken into account, is presented. The SC approach also provides the assessment of corresponding confidence intervals in the set of obtained numerical results. The expansion of statistical output in terms of the mean and variance over a polynomial basis (via SC approach) is shown to be robust and efficient method providing a satisfactory convergence rate. Some illustrative numerical results for the maximum induced field and SAR in the brain and eye, respectively, are given in the paper, as well. 03-31-2017 <![CDATA[ <p>The paper reviews the influence of the variability in the morphology and the tissue properties of the human brain and eye, respectively, exposed to high-frequency (HF) radiation. Deterministic-stochastic modeling enables one to estimate the effects of the parameter uncertainties on the maximum induced electric field and Specific Absorption Rate (SAR). Surface Integral Equation (SIE) scheme applied to the brain exposed to HF radiation and hybrid boundary element method (BEM)/finite element method (FEM) scheme used to handle the eye exposure to HF radiation are discussed.</p><p>Furthermore, a simple stochastic collocation (SC), through which the relevant parameter uncertainties are taken into account, is presented. The SC approach also provides the assessment of corresponding confidence intervals in the set of obtained numerical results. The expansion of statistical output in terms of the mean and variance over a polynomial basis (via SC approach) is shown to be robust and efficient method providing a satisfactory convergence rate. Some illustrative numerical results for the maximum induced field and SAR in the brain and eye, respectively, are given in the paper, as well.</p> ]]> Deterministic-Stochastic Boundary Element Modeling of the Brain and Eye Exposed to High-Frequency Radiation d. poljak h. dodig m. cvetković s. lallechere k. el khamlichi drissi p. bonnet doi: 10.2495/CMEM-V5-N3-250-259 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 250 10.2495/CMEM-V5-N3-250-259 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-250-259 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-241-249 For the analysis of cracks in three-dimensional isotropic thermoelastic media, a temperature and displacement discontinuity boundary element method is developed. The Green functions for unit-point temperature and displacement discontinuities are derived, and the temperature and displacement discontinuity boundary integral equations are obtained for an arbitrarily shaped planar crack. Our boundary element method is based on the Green functions for a triangular element. As an application, elliptical cracks are analyzed to validate the developed method. The influence of various thermal boundary conditions is studied. 03-31-2017 <![CDATA[ <p>For the analysis of cracks in three-dimensional isotropic thermoelastic media, a temperature and displacement discontinuity boundary element method is developed. The Green functions for unit-point temperature and displacement discontinuities are derived, and the temperature and displacement discontinuity boundary integral equations are obtained for an arbitrarily shaped planar crack. Our boundary element method is based on the Green functions for a triangular element. As an application, elliptical cracks are analyzed to validate the developed method. The influence of various thermal boundary conditions is studied. </p> ]]> Temperature and Displacement Discontinuity Boundary Element Method for Analysis of Cracks in Three-Dimensional Isotropic Thermoelastic Media m.h. zhao h.y. dang y. li c.y. fan g.t. xu doi: 10.2495/CMEM-V5-N3-241-249 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 241 10.2495/CMEM-V5-N3-241-249 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-241-249 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-231-240 A formulation is presented to perform crack propagation analyses in cohesive materials with the dual boundary element method (DBEM) using the tangential differential operator in the traction boundary-integral equations. The cohesive law is introduced in the system of equations to directly compute the cohesive forces at each loading step. A single edge crack is analyzed with the linear function to describe the material softening law in the cohesive zone, and the results are compared with those from the literature. 03-31-2017 <![CDATA[ <p>A formulation is presented to perform crack propagation analyses in cohesive materials with the dual boundary element method (DBEM) using the tangential differential operator in the traction boundary-integral equations. The cohesive law is introduced in the system of equations to directly compute the cohesive forces at each loading step. A single edge crack is analyzed with the linear function to describe the material softening law in the cohesive zone, and the results are compared with those from the literature.</p> ]]> A Boundary Element Formulation for Crack Analyses Incorporating a Cohesive Zone Model p.c. gonçalves l. palermo jr. s.p.b. proença doi: 10.2495/CMEM-V5-N3-231-240 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 231 10.2495/CMEM-V5-N3-231-240 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-231-240 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-215-230 A review of Green’s functions for dissimilar or homogeneous elastic space containing penny-shaped or annular interfacial cracks under singular ring-shaped loading sources is presented. The solutions are based on fictitious singular loading sources and superposition of the fundamental solutions of the following two problems: (a) Dissimilar elastic solid without crack under singular source, and (b) Dis-similar elastic solid containing crack under surface tractions. The above Green’s functions have the following advantages: (i) No multi-region BE modeling for the dissimilar material is necessary, and (ii) No discretization of the crack surface is necessary. Numerical examples are presented and discussed. 03-31-2017 <![CDATA[ <p>A review of Green’s functions for dissimilar or homogeneous elastic space containing penny-shaped or annular interfacial cracks under singular ring-shaped loading sources is presented. The solutions are based on fictitious singular loading sources and superposition of the fundamental solutions of the following two problems: (a) Dissimilar elastic solid without crack under singular source, and (b) Dis-similar elastic solid containing crack under surface tractions. The above Green’s functions have the following advantages: (i) No multi-region BE modeling for the dissimilar material is necessary, and (ii) No discretization of the crack surface is necessary. Numerical examples are presented and discussed.</p> ]]> Green’s Functions for Dissimilar or Homogeneous Materials Containing Interfacial Crack, under Axisymmetric Singular Loading Sources d.g. pavlou doi: 10.2495/CMEM-V5-N3-215-230 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 215 10.2495/CMEM-V5-N3-215-230 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-215-230 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-0 This special issue contains a selection of papers presented at the renowned International Conference on Boundary Elements and other Mesh Reduction Methods (BEM) which is now in its 39th edition, having started in 1978. The meeting was organised by the University of Mississippi in the USA and the Wessex Institute, UK.It was at Southampton University where the technique started in the mid-1970s, with the first successful development of boundary integral equations into what is now known as the Boundary Element Method. The success of the meeting has been possible by its continuous evolution. In the early 1990s it was decided to cover all types of Mesh Reduction, opening up a wide new field of technical and applied research.The success of that policy is reflected in the continuous growth of the ranking of the Journal associated with the Conference, i.e. the one of Engineering Analysis with Boundary Elements. The Journal is now in the top third of all its categories.A major development took place last year when WIT Press decided to make available in Open Access form all the conference papers published since 1993. This move has dramatically increased the number of citations that the papers achieve. It is part of the Wessex Institute policy of disseminating scientific and technical outputs as widely as possible.The international researcher will find in this issue a selection of the most recent developments in the method which in the last few years has attracted the attention of a variety of industrial users.The next 40th Conference will take place in the New Forest National Park in the UK, home of the Wessex Institute, giving the occasion to the participants to become more aware of the activities on Campus, where research is focused on the development and applications of boundary elements.The Editors would like to thank all authors for the quality of their papers and the members of the International Scientific Advisory Committee and other colleagues for their help in reviewing the material. The support of Elsevier is gratefully acknowledged for financing the expenses associated with awarding of the 2016 George Green’s Medal.The EditorsSiena, 2016 03-31-2017 <![CDATA[ <p>This special issue contains a selection of papers presented at the renowned International Conference on Boundary Elements and other Mesh Reduction Methods (BEM) which is now in its 39th edition, having started in 1978. The meeting was organised by the University of Mississippi in the USA and the Wessex Institute, UK.</p><p>It was at Southampton University where the technique started in the mid-1970s, with the first successful development of boundary integral equations into what is now known as the Boundary Element Method. The success of the meeting has been possible by its continuous evolution. In the early 1990s it was decided to cover all types of Mesh Reduction, opening up a wide new field of technical and applied research.</p><p>The success of that policy is reflected in the continuous growth of the ranking of the Journal associated with the Conference, i.e. the one of Engineering Analysis with Boundary Elements. The Journal is now in the top third of all its categories.</p><p>A major development took place last year when WIT Press decided to make available in Open Access form all the conference papers published since 1993. This move has dramatically increased the number of citations that the papers achieve. It is part of the Wessex Institute policy of disseminating scientific and technical outputs as widely as possible.</p><p>The international researcher will find in this issue a selection of the most recent developments in the method which in the last few years has attracted the attention of a variety of industrial users.</p><p>The next 40th Conference will take place in the New Forest National Park in the UK, home of the Wessex Institute, giving the occasion to the participants to become more aware of the activities on Campus, where research is focused on the development and applications of boundary elements.</p><p>The Editors would like to thank all authors for the quality of their papers and the members of the International Scientific Advisory Committee and other colleagues for their help in reviewing the material. The support of Elsevier is gratefully acknowledged for financing the expenses associated with awarding of the 2016 George Green’s Medal.</p><p><em>The Editors</em></p><p><em>Siena, 2016</em></p> ]]> Preface alexander h-d. cheng carlos a. brebbia doi: 10.2495/CMEM-V5-N3-0 International Journal of Computational Methods and Experimental Measurements 03-31-2017 International Journal of Computational Methods and Experimental Measurements 03-31-2017 2017 5 3 Article 0 10.2495/CMEM-V5-N3-0 https://www.acadlore.com/article/IJCMEM/2017_5_3/CMEM-V5-N3-0 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-200-210 Producing a light structure with affordable cost without sacrificing strength has always been a challenging task for designers. Using a hybrid material approach provides an expanded methodology to combine materials having different costs and properties (for example, combining fibers with high cost and high stiffness such as carbon with low cost, less stiffness fibers such as glass). Hence, a comparative approach is useful for the evaluation of design solutions in terms of weight and cost. In this study, a methodology for a combined weight and cost optimization for sandwich plates with hybrid composite facesheets and foam core is presented. The weight and cost of the hybrid sandwich plates considered are the objective functions subject to required equality constraints based on the bending and torsional stiffnesses. The hybrid sandwich plates considered consisted of thin hybrid composite facesheets, symmetric with respect to the mid-plane of the sandwich plates. The facesheets considered consisted of carbon/epoxy and E-glass/epoxy fiber-reinforced polymer. The layup of the fibers of the facesheets were restricted to some discrete sets of plies having orientation angles of 0, ±45 and 90. A multi-objective optimization technique was applied to minimize simultaneously the weight and the cost of the hybrid sandwich plate. The normalized normal constraint method with Pareto filter was used to generate the Pareto frontier trade-off curve. The Pareto trade-off curve was constructed by optimizing a sequence of combining weight and cost objective functions, while every function was minimized using the Active Set Algorithm. 02-28-2017 <![CDATA[ <p>Producing a light structure with affordable cost without sacrificing strength has always been a challenging task for designers. Using a hybrid material approach provides an expanded methodology to combine materials having different costs and properties (for example, combining fibers with high cost and high stiffness such as carbon with low cost, less stiffness fibers such as glass). Hence, a comparative approach is useful for the evaluation of design solutions in terms of weight and cost. In this study, a methodology for a combined weight and cost optimization for sandwich plates with hybrid composite facesheets and foam core is presented. The weight and cost of the hybrid sandwich plates considered are the objective functions subject to required equality constraints based on the bending and torsional stiffnesses. The hybrid sandwich plates considered consisted of thin hybrid composite facesheets, symmetric with respect to the mid-plane of the sandwich plates. The facesheets considered consisted of carbon/epoxy and E-glass/epoxy fiber-reinforced polymer. The layup of the fibers of the facesheets were restricted to some discrete sets of plies having orientation angles of 0, ±45 and 90. A multi-objective optimization technique was applied to minimize simultaneously the weight and the cost of the hybrid sandwich plate. The normalized normal constraint method with Pareto filter was used to generate the Pareto frontier trade-off curve. The Pareto trade-off curve was constructed by optimizing a sequence of combining weight and cost objective functions, while every function was minimized using the Active Set Algorithm.</p> ]]> Weight and Cost Multi-Objective Optimization of Hybrid Composite Sandwich Structures a. i. salem s. l. donaldson doi: 10.2495/CMEM-V5-N2-200-210 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 200 10.2495/CMEM-V5-N2-200-210 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-200-210 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-190-199 Composite structures with the shell-like geometry must provide the sufficient mechanical stiffness in order to eliminate the unwanted deformations caused by the action of airflow. Because the pressure field on the design surface caused by airflow is generally uniform, the ensuring of the necessary stiffness can be achieved by creating a nonuniform thickness along the shell surface. In the present study the CFD finite element analysis of the virtual wind-tunnel test for the studied composite shell is performed assuming its absolute stiffness. The problem is further parameterized by the introduction of the auxiliary sphere, which causes a smooth distribution function of the shell thickness. The optimum seeking is performed by means of the four parameter variation of this function, providing a minimum total energy of the shell deformation under the given restrictions on its weight. 02-28-2017 <![CDATA[ <p>Composite structures with the shell-like geometry must provide the sufficient mechanical stiffness in order to eliminate the unwanted deformations caused by the action of airflow. Because the pressure field on the design surface caused by airflow is generally uniform, the ensuring of the necessary stiffness can be achieved by creating a nonuniform thickness along the shell surface. In the present study the CFD finite element analysis of the virtual wind-tunnel test for the studied composite shell is performed assuming its absolute stiffness. The problem is further parameterized by the introduction of the auxiliary sphere, which causes a smooth distribution function of the shell thickness. The optimum seeking is performed by means of the four parameter variation of this function, providing a minimum total energy of the shell deformation under the given restrictions on its weight.</p> ]]> Optimization of Wall Thickness and Lay-up Design for Composite Structure with Open-Shell Geometry m. shevtsova i. zhilyaev p. oganesyan v. shevtsova doi: 10.2495/CMEM-V5-N2-190-199 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 190 10.2495/CMEM-V5-N2-190-199 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-190-199 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-179-189 In this paper, the influence of steel fiber-reinforcement when designing precast-prestressed concrete (PPC) road bridges with a double U-shape cross-section is studied through heuristic optimization. A hybrid evolutionary algorithm (EA) combining a genetic algorithm (GA) with variable-depth neighborhood search (VDNS) is formulated to minimize the economic cost and $\mathrm{CO}_2$ emissions, while imposing constraints on all the relevant limit states. The case study proposed is a 30-m span-length with a deck width of 12 m. The problem involved 41 discrete design variables. The algorithm requires the initial calibration. Moreover, the heuristic is run nine times so as to obtain statistical information about the minimum, average and deviation of the results. The evolution of the objective function during the opti- mization procedure is highlighted. Findings show that heuristic optimization is a forthcoming option for the design of real-life prestressed structures. This paper provides useful knowledge that could offer a better understanding of the steel fiber-reinforcement in U-beam road bridges. 02-28-2017 <![CDATA[ <p>In this paper, the influence of steel fiber-reinforcement when designing precast-prestressed concrete (PPC) road bridges with a double U-shape cross-section is studied through heuristic optimization. A hybrid evolutionary algorithm (EA) combining a genetic algorithm (GA) with variable-depth neighborhood search (VDNS) is formulated to minimize the economic cost and $\mathrm{CO}_2$ emissions, while imposing constraints on all the relevant limit states. The case study proposed is a 30-m span-length with a deck width of 12 m. The problem involved 41 discrete design variables. The algorithm requires the initial calibration. Moreover, the heuristic is run nine times so as to obtain statistical information about the minimum, average and deviation of the results. The evolution of the objective function during the opti- mization procedure is highlighted. Findings show that heuristic optimization is a forthcoming option for the design of real-life prestressed structures. This paper provides useful knowledge that could offer a better understanding of the steel fiber-reinforcement in U-beam road bridges.</p> ]]> Design Optimization of Precast-Prestressed Concrete Road Bridges with Steel Fiber-Reinforcement by a Hybrid Evolutionary Algorithm v. yepes j.v. martí t. garcía-segura doi: 10.2495/CMEM-V5-N2-179-189 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 179 10.2495/CMEM-V5-N2-179-189 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-179-189 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-171-178 In bridge design, many variables like material grades, cross-sectional dimensions, passive and prestressing steel need to be modeled to evaluate structural performance. Efficiency gains are intended while satisfying the serviceability and ultimate limit states imposed by the structural code. In this paper, a computer-support tool is presented to analyze continuous post-tensioned concrete (PSC) box-girder road bridges, to minimize the cost as well as to provide optimum design variables. The program encompasses six modules to perform the optimization process, the finite-element analysis, and the limit states verification. The methodology is defined and applied to a case study. A harmony search (HS) algorithm optimizes 33 variables that define a three-span PSC box-girder bridge located in a coastal region. However, the same procedure could be implemented to optimize any structure. This tool enables one to define the fixed parameters and the variables that are optimized by the heuristic algorithm. Moreover, the output provides useful rules to guide engineers in designing PSC box-girder road bridges. 02-28-2017 <![CDATA[ <p>In bridge design, many variables like material grades, cross-sectional dimensions, passive and prestressing steel need to be modeled to evaluate structural performance. Efficiency gains are intended while satisfying the serviceability and ultimate limit states imposed by the structural code. In this paper, a computer-support tool is presented to analyze continuous post-tensioned concrete (PSC) box-girder road bridges, to minimize the cost as well as to provide optimum design variables. The program encompasses six modules to perform the optimization process, the finite-element analysis, and the limit states verification. The methodology is defined and applied to a case study. A harmony search (HS) algorithm optimizes 33 variables that define a three-span PSC box-girder bridge located in a coastal region. However, the same procedure could be implemented to optimize any structure. This tool enables one to define the fixed parameters and the variables that are optimized by the heuristic algorithm. Moreover, the output provides useful rules to guide engineers in designing PSC box-girder road bridges.</p> ]]> Computer-Support Tool to Optimize Bridges Automatically t. garcía-segura v. yepes j. alcalá doi: 10.2495/CMEM-V5-N2-171-178 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 171 10.2495/CMEM-V5-N2-171-178 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-171-178 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-163-170 This research reports a vehicle occupant restraint system design by using evolutionary multi-objective optimization with response surface model. The vehicle occupant restraint systems are composed of restraint equipment, such as an airbag, a seat belt and a knee bolster. The optimization aims to improve the safety of the system by evaluating some indexes based on some safety regulations. Estimation mod- els of the safety indexes are introduced for accelerating the optimization. The estimation models, which are called the response surface models, are constructed by using Gaussian Process, which is a kind of machine learning method. The Gaussian Process constructs the estimation model from sampling results, which are calculated by using multi-body dynamics simulation. Some helpful information for designing the restraint systems, such as trade-off information of safety performance and contribution of design variables for the safety performance, is obtained by analysing the Pareto optimal solutions. 02-28-2017 <![CDATA[ <p>This research reports a vehicle occupant restraint system design by using evolutionary multi-objective optimization with response surface model. The vehicle occupant restraint systems are composed of restraint equipment, such as an airbag, a seat belt and a knee bolster. The optimization aims to improve the safety of the system by evaluating some indexes based on some safety regulations. Estimation mod- els of the safety indexes are introduced for accelerating the optimization. The estimation models, which are called the response surface models, are constructed by using Gaussian Process, which is a kind of machine learning method. The Gaussian Process constructs the estimation model from sampling results, which are calculated by using multi-body dynamics simulation. Some helpful information for designing the restraint systems, such as trade-off information of safety performance and contribution of design variables for the safety performance, is obtained by analysing the Pareto optimal solutions. </p> ]]> Multi-Objective Optimization of Vehicle Occupant Restraint System by Using Evolutionary Algorithm with Response Surface Model h. horii doi: 10.2495/CMEM-V5-N2-163-170 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 163 10.2495/CMEM-V5-N2-163-170 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-163-170 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-154-162 We propose a new framework for topology optimization based on the boundary element discretization and kernel-independent fast multipole method (KIFMM). The boundary value problem for the considered partial differential equation is reformulated as a surface integral equation and is solved on the domain boundary. Volume solution at selected points is found via surface integrals. At every iteration of the optimization process, the new boundary is extracted as a level set of a topological derivative. Both surface and volume solutions are accelerated using KIFMM. The obtained technique is highly universal, fully parallelized, it allows achieving asymptotically the best performance with the optimization iteration complexity proportional to a number of surface discretization elements. More-over, our approach is free of the artifacts that are inherent for finite element optimization techniques, such as “checkerboard” instability. The performance of the approach is showcased on few illustrative examples. 02-28-2017 <![CDATA[ <p>We propose a new framework for topology optimization based on the boundary element discretization and kernel-independent fast multipole method (KIFMM). The boundary value problem for the considered partial differential equation is reformulated as a surface integral equation and is solved on the domain boundary. Volume solution at selected points is found via surface integrals. At every iteration of the optimization process, the new boundary is extracted as a level set of a topological derivative. Both surface and volume solutions are accelerated using KIFMM. The obtained technique is highly universal, fully parallelized, it allows achieving asymptotically the best performance with the optimization iteration complexity proportional to a number of surface discretization elements. More-over, our approach is free of the artifacts that are inherent for finite element optimization techniques, such as “checkerboard” instability. The performance of the approach is showcased on few illustrative examples.</p> ]]> Parallel Optimization with Boundary Elements and Kernel Independent Fast Multipole Method igor ostanin denis zorin ivan oseledets doi: 10.2495/CMEM-V5-N2-154-162 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 154 10.2495/CMEM-V5-N2-154-162 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-154-162 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-144-153 The effects of ceramic powder, a waste material, on the properties of lime-cement plasters were investigated in this article. The influence of the addition of the pozzolana as a supplementary cementitious material on mechanical and thermal properties of the studied materials was assessed in relation to its basic physical properties and pore structure characterization. Investigated parameters were bulk density, matrix density, open porosity, pore-size distribution, compressive strength, tensile strength, thermal conductivity and specific heat capacity. The results revealed the densifying effect of the pozzolana on the plaster microstructure as the open porosity decreased and bulk density rose to binder replacement level. Although the mean diameter of pores for plasters with higher amount of pozzolana was slightly higher, the volume of pores was lower. The presence of ceramic powder also showed a positive effect on the mechanical properties of plasters. Both compressive and tensile strength rose with increasing replacement ratio. Varying porosities were reflected in the increasing trend of thermal conductivity with rising binder replacement level. On the contrary, specific heat capacity showed the lower values the higher the amount of pozzolana. 02-28-2017 <![CDATA[ <p>The effects of ceramic powder, a waste material, on the properties of lime-cement plasters were investigated in this article. The influence of the addition of the pozzolana as a supplementary cementitious material on mechanical and thermal properties of the studied materials was assessed in relation to its basic physical properties and pore structure characterization. Investigated parameters were bulk density, matrix density, open porosity, pore-size distribution, compressive strength, tensile strength, thermal conductivity and specific heat capacity. The results revealed the densifying effect of the pozzolana on the plaster microstructure as the open porosity decreased and bulk density rose to binder replacement level. Although the mean diameter of pores for plasters with higher amount of pozzolana was slightly higher, the volume of pores was lower. The presence of ceramic powder also showed a positive effect on the mechanical properties of plasters. Both compressive and tensile strength rose with increasing replacement ratio. Varying porosities were reflected in the increasing trend of thermal conductivity with rising binder replacement level. On the contrary, specific heat capacity showed the lower values the higher the amount of pozzolana.</p> ]]> Properties of Lime-cement Plasters Incorporating Ceramic Powder m. cˇáchová d. konˇáková e. vejmelková e. bartonˇková m. keppert r. cˇerný doi: 10.2495/CMEM-V5-N2-144-153 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 144 10.2495/CMEM-V5-N2-144-153 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-144-153 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-135-143 The present paper describes experimental measurements of wood stiffness and analytical homogenization to provide estimates of the Micro-fibril angle (MFA). It is known that the orientation of fiber-like aggregates of crystalline cellulose in S2 layer of the wood cell with respect to the alignment of lumens considerably influences the overall stiffness of wood. Recently an inverse approach exploiting the results of nanoindentation at the level of wood cell and analytical homogenization has been proposed as a suitable tool for the MFA determination. A simpler methodology based on the results of indentation at the structural level using the Pilodyn 6J testing device has also been advocated as an alternative appealing particularly to engineering practice. Comparison of the two approaches suggesting their advantages as well as drawbacks is the principal objective of this contribution. As an example, an application to spruce as the most common type of wood used in building structures is considered. 02-28-2017 <![CDATA[ <p>The present paper describes experimental measurements of wood stiffness and analytical homogenization to provide estimates of the Micro-fibril angle (MFA). It is known that the orientation of fiber-like aggregates of crystalline cellulose in S2 layer of the wood cell with respect to the alignment of lumens considerably influences the overall stiffness of wood. Recently an inverse approach exploiting the results of nanoindentation at the level of wood cell and analytical homogenization has been proposed as a suitable tool for the MFA determination. A simpler methodology based on the results of indentation at the structural level using the Pilodyn 6J testing device has also been advocated as an alternative appealing particularly to engineering practice. Comparison of the two approaches suggesting their advantages as well as drawbacks is the principal objective of this contribution. As an example, an application to spruce as the most common type of wood used in building structures is considered.</p> ]]> Comparing Nano and Macroindentation in Search of Microfibril Angle in Spruce l. kucíková j. vorel v. hrbek j. němeček m. šejnoha doi: 10.2495/CMEM-V5-N2-135-143 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 135 10.2495/CMEM-V5-N2-135-143 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-135-143 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-125-134 Nowadays, in different industrial fields as transport or aerospace, a research effort is conducted to reduce the structural weight. One of the most promising solutions is the use of composite structures due to their high stiffness, their low mass density and their low damping factor. At the same time, there is an intensification of the operational dynamic environment and an increase of durability requirements. These different expectations seem to be contradictory. One solution to manage these points is to design and manufacture smart composite structures with a fully distributed set of integrated piezoelectric transducers. These structures are able to modify their mechanical properties with respect to their environment (e.g. active vibration control), to interact with other structures (e.g. mechatronic) or with human beings (e.g. Human–Machine Interaction).To meet the technical specifications of smart composite structures, in particular for complex geometries, it is necessary to master the manufacturing process and consequently the material parameters of the manufactured composite. Indeed, during the design phase, these parameters have to be absolutely known. A design approach based on engineering system theory and uncertainty calculation is applied to our manufacturing process of smart composite structures. In this paper, two different material identification methods (the Resonalyser technique and the Time-of-Flight technique) were selected and are applied to several test plates and, finally, on a large smart spherical cap. The Resonalyser technique is a good method to extract overall material parameters. Its major drawback in terms of cost and difficulty of implementation is the use of contactless devices for the measurements. The Time-of-Flight technique is based on the duration measurements of pulse propagation with a simple and low cost experimental setup. Integrated piezoelectric transducers are used for this purpose in the present analysis. The results obtained are quite local (mean values along the propagation path) and need a strong physical interpretation. The different material parameters obtained are compared and discussed. 02-28-2017 <![CDATA[ <p>Nowadays, in different industrial fields as transport or aerospace, a research effort is conducted to reduce the structural weight. One of the most promising solutions is the use of composite structures due to their high stiffness, their low mass density and their low damping factor. At the same time, there is an intensification of the operational dynamic environment and an increase of durability requirements. These different expectations seem to be contradictory. One solution to manage these points is to design and manufacture smart composite structures with a fully distributed set of integrated piezoelectric transducers. These structures are able to modify their mechanical properties with respect to their environment (e.g. active vibration control), to interact with other structures (e.g. mechatronic) or with human beings (e.g. Human–Machine Interaction).</p><p>To meet the technical specifications of smart composite structures, in particular for complex geometries, it is necessary to master the manufacturing process and consequently the material parameters of the manufactured composite. Indeed, during the design phase, these parameters have to be absolutely known. A design approach based on engineering system theory and uncertainty calculation is applied to our manufacturing process of smart composite structures. In this paper, two different material identification methods (the Resonalyser technique and the Time-of-Flight technique) were selected and are applied to several test plates and, finally, on a large smart spherical cap. The Resonalyser technique is a good method to extract overall material parameters. Its major drawback in terms of cost and difficulty of implementation is the use of contactless devices for the measurements. The Time-of-Flight technique is based on the duration measurements of pulse propagation with a simple and low cost experimental setup. Integrated piezoelectric transducers are used for this purpose in the present analysis. The results obtained are quite local (mean values along the propagation path) and need a strong physical interpretation. The different material parameters obtained are compared and discussed.</p> ]]> Complex Composite Structures with Integrated Piezoelectric Transducers xianlong chen rémy lachat sébastien salmon morvan ouisse yann meyer doi: 10.2495/CMEM-V5-N2-125-134 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 125 10.2495/CMEM-V5-N2-125-134 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-125-134 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-116-124 Crack formations in concrete may cause major damages in concrete structures. These damages require extensive maintenance work and thus have high costs. This paper addresses issues such as what causes cracks in concrete structures and how does the appearance of cracks look like with respect to an applied load? Can the appearance, distance, and size of the crack tell us something about crack initiation and propagation, or is it just by pure coincidence that cracks occur in structures as they do?This research work investigated the effect of external factors such as load variables, time, the dimensions of the beam and the relative humidity on crack formation. Internal factors that have been investigated are the various constituents of the concrete, and how various levels of these constituents have an impact on cracking. In addition, the influence of concrete quality, tensile reinforcement, shear reinforcement, and anchoring reinforcement was investigated.The paper presents technical calculations, where both the bending moment and shear forces are included in the analysis to determine how crack formations will propagate in the beam as a function of the applied loads. The first part of the paper deals with the theoretical factors that influence cracking in concrete. The second part deals with the calculations of crack formation in concrete. The results show how the cracks propagate in the x and y directions as a function of the load being applied. 02-28-2017 <![CDATA[ <p>Crack formations in concrete may cause major damages in concrete structures. These damages require extensive maintenance work and thus have high costs. This paper addresses issues such as what causes cracks in concrete structures and how does the appearance of cracks look like with respect to an applied load? Can the appearance, distance, and size of the crack tell us something about crack initiation and propagation, or is it just by pure coincidence that cracks occur in structures as they do?</p><p>This research work investigated the effect of external factors such as load variables, time, the dimensions of the beam and the relative humidity on crack formation. Internal factors that have been investigated are the various constituents of the concrete, and how various levels of these constituents have an impact on cracking. In addition, the influence of concrete quality, tensile reinforcement, shear reinforcement, and anchoring reinforcement was investigated.</p><p>The paper presents technical calculations, where both the bending moment and shear forces are included in the analysis to determine how crack formations will propagate in the beam as a function of the applied loads. The first part of the paper deals with the theoretical factors that influence cracking in concrete. The second part deals with the calculations of crack formation in concrete. The results show how the cracks propagate in the x and y directions as a function of the load being applied.</p> ]]> Crack Formation and Crack Propagation into the Compression Zone on Reinforced Concrete Beam Structures samdar kakay daniel bårdsen ove t. gudmestad doi: 10.2495/CMEM-V5-N2-116-124 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 116 10.2495/CMEM-V5-N2-116-124 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-116-124 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-105-115 Research into structural reliability for tensile structures is needed. The semi-probabilistic format for verification of so-called form-passive structures is well-established in the Eurocodes. Partial factors are the main features of this semi-probabilistic or design value method. Whereas for conventional structures these partial factors are calibrated to previous experience [1], appropriate partial factors have to be proposed and evaluated for tensile structures. A cable net structure built in 1958 was used as a case study to gain insight into the effect of partial factors according to Eurocode 3 (steel structures). Prestress contributes to the stiffness in the non-linear structural behaviour of membrane structures and thus increasing the prestress with factor 1.35 according to the Eurocodes might be non-conservative. The article investigates the effect of the partial factor for prestress (1.0 or 1.35) on a membrane structure. A similar geometry as the steel cable net structure is designed and analysed for comparison with the cable net structure. For the primary steel structure the partial factor for prestress 1.35 has to be applied. An in-depth study of the effect of the partial factor for prestress on the stress distribution in the membrane in warp and weft direction is performed. The stress distribution clearly depends on the boundary conditions. A sound conclusion though requires a thorough in-depth study for different shapes and membrane types. In a first step towards a reliability approach, the structural reliability of a three segments cable net structure is currently being analysed, taking into account the uncertainties associated with the pre-tensioned system. 02-28-2017 <![CDATA[ <p>Research into structural reliability for tensile structures is needed. The semi-probabilistic format for verification of so-called form-passive structures is well-established in the Eurocodes. Partial factors are the main features of this semi-probabilistic or design value method. Whereas for conventional structures these partial factors are calibrated to previous experience [1], appropriate partial factors have to be proposed and evaluated for tensile structures. A cable net structure built in 1958 was used as a case study to gain insight into the effect of partial factors according to Eurocode 3 (steel structures). Prestress contributes to the stiffness in the non-linear structural behaviour of membrane structures and thus increasing the prestress with factor 1.35 according to the Eurocodes might be non-conservative. The article investigates the effect of the partial factor for prestress (1.0 or 1.35) on a membrane structure. A similar geometry as the steel cable net structure is designed and analysed for comparison with the cable net structure. For the primary steel structure the partial factor for prestress 1.35 has to be applied. An in-depth study of the effect of the partial factor for prestress on the stress distribution in the membrane in warp and weft direction is performed. The stress distribution clearly depends on the boundary conditions. A sound conclusion though requires a thorough in-depth study for different shapes and membrane types. In a first step towards a reliability approach, the structural reliability of a three segments cable net structure is currently being analysed, taking into account the uncertainties associated with the pre-tensioned system.</p> ]]> Approach to a Reliability Framework FOR Membrane Structure Design AND Analysis l. pyl x. wang e. de smedt m. mollaert doi: 10.2495/CMEM-V5-N2-105-115 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 105 10.2495/CMEM-V5-N2-105-115 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-105-115 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-0 The present issue contains a selection of edited papers presented at the Conference on High Performance and Optimum Design of Structures and Methods held at the University of Siena and co-organised by the Wessex Institute, UK, the Free University of Brussels and the University of A Coruña in Spain.The issue contains papers on advanced types of structures, based on new design concepts. Modern structural design requires the development of new methods that can lead to systems able to resist a range of external stimuli. Particular emphasis is being placed on intelligent structures and materials.Modern materials used in engineering components of structures are required to withstand a wide range of external stimuli. These range from high temperatures to special materials for restoration of heritage structures. Textile structures are usually highly stressed but they must result in minimal creep or relaxation for instance. Current research is also focused on their durability, which allows them to operate properly during their required lifetime.Structural engineers must find adequate answers to the challenges of contemporary civil architecture, very often being a combination of lightweight structures with large spans. This requires sophisticated calculation techniques, including non-linear and vibration behaviour.These new challenges require analysis, not only in terms of ultimate strength, serviceability and limit states but also in terms of their reliability and integrity. The engineer is also faced with the need to design ecological friendly structures to reduce their environmental impacts and incorporate reasonable resources.The development and application of modern computational methods and powerful computers for structural modelling, control and management has increased the probabilities of using graphic interfaces and the incorporation of optimisation in the design process.Some of the contributions in this issue are devoted to theoretical advances and practical applications of optimum design methodologies to several engineering disciplines. They demonstrate the current maturity of this design technique that has evolved with time from academic research to become a tool, useful to practising engineers. In fact, papers included in this issue originate not only from universities and research institutions but also from engineering companies. The papers are related to optimization of concrete and steel bridges, special structures and mechanical engineering. The problems formulated are very diverse and include size, shape and topology optimization, composite materials and a variety of nonlinear analysis.Re-use and recyclability of materials and structural components is becoming increasingly important, i.e. supporting the “cradle to cradle” approach. Re-use is also found nowadays in two levels, not only from the re-use of structural components and materials but also the transformation of complete buildings, such as offices into schools or residential accommodation.The papers included in this issue reflect these advances and provide a state of the art view of some of the most recent advances in high performance structures and materials. They are published by WIT Press and available Open Access in the eLibrary of the Institute (witpress. com/elibrary) where they can be downloaded for free by the international community.The Editors are grateful to the authors for their papers and to the reviewers for their help in ensuring the quality of the contents of this issue.The EditorsSiena, 2016 02-28-2017 <![CDATA[ <p>The present issue contains a selection of edited papers presented at the Conference on High Performance and Optimum Design of Structures and Methods held at the University of Siena and co-organised by the Wessex Institute, UK, the Free University of Brussels and the University of A Coruña in Spain.</p><p>The issue contains papers on advanced types of structures, based on new design concepts. Modern structural design requires the development of new methods that can lead to systems able to resist a range of external stimuli. Particular emphasis is being placed on intelligent structures and materials.</p><p>Modern materials used in engineering components of structures are required to withstand a wide range of external stimuli. These range from high temperatures to special materials for restoration of heritage structures. Textile structures are usually highly stressed but they must result in minimal creep or relaxation for instance. Current research is also focused on their durability, which allows them to operate properly during their required lifetime.</p><p>Structural engineers must find adequate answers to the challenges of contemporary civil architecture, very often being a combination of lightweight structures with large spans. This requires sophisticated calculation techniques, including non-linear and vibration behaviour.</p><p>These new challenges require analysis, not only in terms of ultimate strength, serviceability and limit states but also in terms of their reliability and integrity. The engineer is also faced with the need to design ecological friendly structures to reduce their environmental impacts and incorporate reasonable resources.</p><p>The development and application of modern computational methods and powerful computers for structural modelling, control and management has increased the probabilities of using graphic interfaces and the incorporation of optimisation in the design process.</p><p>Some of the contributions in this issue are devoted to theoretical advances and practical applications of optimum design methodologies to several engineering disciplines. They demonstrate the current maturity of this design technique that has evolved with time from academic research to become a tool, useful to practising engineers. In fact, papers included in this issue originate not only from universities and research institutions but also from engineering companies. The papers are related to optimization of concrete and steel bridges, special structures and mechanical engineering. The problems formulated are very diverse and include size, shape and topology optimization, composite materials and a variety of nonlinear analysis.</p><p>Re-use and recyclability of materials and structural components is becoming increasingly important, i.e. supporting the “cradle to cradle” approach. Re-use is also found nowadays in two levels, not only from the re-use of structural components and materials but also the transformation of complete buildings, such as offices into schools or residential accommodation.</p><p>The papers included in this issue reflect these advances and provide a state of the art view of some of the most recent advances in high performance structures and materials. They are published by WIT Press and available Open Access in the eLibrary of the Institute (witpress. com/elibrary) where they can be downloaded for free by the international community.</p><p>The Editors are grateful to the authors for their papers and to the reviewers for their help in ensuring the quality of the contents of this issue.</p><p>The Editors</p><p>Siena, 2016</p> ]]> Preface doi: 10.2495/CMEM-V5-N2-0 International Journal of Computational Methods and Experimental Measurements 02-28-2017 International Journal of Computational Methods and Experimental Measurements 02-28-2017 2017 5 2 Article 0 10.2495/CMEM-V5-N2-0 https://www.acadlore.com/article/IJCMEM/2017_5_2/CMEM-V5-N2-0 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-87-95 Flame spread along the energized polyethylene (PE) insulated copper wire under low pressure was investigated experimentally to gain a better understanding of electrical wire fire in aircraft and space habitats. Three types of sample wires, with the same insulation thickness and different core diameters, were used in this research study. First, a simplified model was developed to quantitatively explain the impact of lower pressure on the flame propagation over the energized wires. As with the pressure decreased, both of Grashof number (Gr) and Reynolds number (Re) were decreased and the air-flow diffusion played a gradual and dominant role in the combustion process. Mainly caused by the decrease of natural convention, the heat loss turned to be reduced, resulting in the reduction of oxygen flow and the formation of carbon black was inhibited. Second, several experiments were conducted to investigate the flame spread along the energized wires in a walk-in hypobaric chamber. The experimental results showed that, with the decrease of pressure, the flame height was reduced, the flame shape turned to be spherical, and the blue area showed increased. But the flame shape was reduced gradually along the wire, till extinguished when the pressure set out below a critical value. The accumulation of melt insulation increased and the dripping behavior occurred easily under lower pressure. Moreover, the influence of overload current on the flame spreading velocity was also presented. This work was useful for a further study on the fire risk of electrical wires under low pressure. 12-31-2016 <![CDATA[ <p>Flame spread along the energized polyethylene (PE) insulated copper wire under low pressure was investigated experimentally to gain a better understanding of electrical wire fire in aircraft and space habitats. Three types of sample wires, with the same insulation thickness and different core diameters, were used in this research study. First, a simplified model was developed to quantitatively explain the impact of lower pressure on the flame propagation over the energized wires. As with the pressure decreased, both of Grashof number (Gr) and Reynolds number (Re) were decreased and the air-flow diffusion played a gradual and dominant role in the combustion process. Mainly caused by the decrease of natural convention, the heat loss turned to be reduced, resulting in the reduction of oxygen flow and the formation of carbon black was inhibited. Second, several experiments were conducted to investigate the flame spread along the energized wires in a walk-in hypobaric chamber. The experimental results showed that, with the decrease of pressure, the flame height was reduced, the flame shape turned to be spherical, and the blue area showed increased. But the flame shape was reduced gradually along the wire, till extinguished when the pressure set out below a critical value. The accumulation of melt insulation increased and the dripping behavior occurred easily under lower pressure. Moreover, the influence of overload current on the flame spreading velocity was also presented. This work was useful for a further study on the fire risk of electrical wires under low pressure.</p> ]]> Flame Propagation over Energized Pe-Insulated Wire under Low Pressure h. he q. x. zhang l. y. zhao j. liu j. j. wang y. m. zhang doi: 10.2495/CMEM-V5-N1-87-95 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 87 10.2495/CMEM-V5-N1-87-95 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-87-95 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-76-86 Steam cycles are a mature technology that has been used for many decades to produce power from heat. Novel expanders that can expand in the two-phase region have been developed for years but only recently have achieved a level of maturity that makes them commercially interesting.In this study wet and dry steam cycles recovering heat from gas turbines in offshore industry are compared in a thermodynamic basis. Three different cycle configurations are studied in three scenarios with different combinations of power and heat demand. Every case is optimized with and without restrictions for two-phase steam expansion.It is shown that wet expansion cycles can achieve higher steam pressures which increase steam cycle efficiency. Steam cycle power increase has been found to be large for single expansion cases (20%) due to the low pressures that can be achieved by the dry cycles.Optimization of two-stage wet expansion does not produce significant improvements and in some cases results are equivalent to single stage wet expansion cycles.Energy savings and CO2 emissions reduction when comparing with the reference cases without steam cycle installation are found to be in the range of 17%–26%. 12-31-2016 <![CDATA[ <p>Steam cycles are a mature technology that has been used for many decades to produce power from heat. Novel expanders that can expand in the two-phase region have been developed for years but only recently have achieved a level of maturity that makes them commercially interesting.</p><p>In this study wet and dry steam cycles recovering heat from gas turbines in offshore industry are compared in a thermodynamic basis. Three different cycle configurations are studied in three scenarios with different combinations of power and heat demand. Every case is optimized with and without restrictions for two-phase steam expansion.</p><p>It is shown that wet expansion cycles can achieve higher steam pressures which increase steam cycle efficiency. Steam cycle power increase has been found to be large for single expansion cases (20%) due to the low pressures that can be achieved by the dry cycles.</p><p>Optimization of two-stage wet expansion does not produce significant improvements and in some cases results are equivalent to single stage wet expansion cycles.</p><p>Energy savings and CO2 emissions reduction when comparing with the reference cases without steam cycle installation are found to be in the range of 17%–26%.</p> ]]> Wet Expansion Steam Cycles for Offshore Industry d. p. clos g. skaugen m. mazetti d. rohde doi: 10.2495/CMEM-V5-N1-76-86 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 76 10.2495/CMEM-V5-N1-76-86 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-76-86 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-66-75 This study reports the results of a numerical investigation and optimization of the hydrodynamic and thermal performance of two new types of pin-fin and plate-fin heat sinks. The first type consists of inclined cones and is inspired by the larger heat transfer extents in impinging flow conditions, whilst the second type concerns wavy form plate-fins chosen such as to combine the effects of thermal boundary layer re-initialization, flow separation and large heat transfer area of classical plate fins. Fairly complex features are considered, which cannot be manufactured easily using traditional approaches. However, in this study we exploit the manufacturing flexibility offered by a new surface-structuring technology, which allows to produce more complex geometries than possible with the current state-of-the-art techniques. A simplified numerical methodology has been proposed to decrease the computational cost, which was then validated with respect to the literature and the laboratory tests. Baseline versions of the two proposed geometries were compared to more common geometries found in the literature in order to make a first choice. The results show that the inclined cone features can increase the heat transfer coefficient, especially in inverse configuration, whereas the wave structures require very large pressure losses to achieve similar levels of thermal performance. Subsequently, only inclined cones have been optimized using an Evolutionary Algorithm optimization platform. The optimized geometries increase the overall performance, especially reducing the pressure drop, in comparison to the geometries found in the literature. 12-31-2016 <![CDATA[ <p>This study reports the results of a numerical investigation and optimization of the hydrodynamic and thermal performance of two new types of pin-fin and plate-fin heat sinks. The first type consists of inclined cones and is inspired by the larger heat transfer extents in impinging flow conditions, whilst the second type concerns wavy form plate-fins chosen such as to combine the effects of thermal boundary layer re-initialization, flow separation and large heat transfer area of classical plate fins. Fairly complex features are considered, which cannot be manufactured easily using traditional approaches. However, in this study we exploit the manufacturing flexibility offered by a new surface-structuring technology, which allows to produce more complex geometries than possible with the current state-of-the-art techniques. A simplified numerical methodology has been proposed to decrease the computational cost, which was then validated with respect to the literature and the laboratory tests. Baseline versions of the two proposed geometries were compared to more common geometries found in the literature in order to make a first choice. The results show that the inclined cone features can increase the heat transfer coefficient, especially in inverse configuration, whereas the wave structures require very large pressure losses to achieve similar levels of thermal performance. Subsequently, only inclined cones have been optimized using an Evolutionary Algorithm optimization platform. The optimized geometries increase the overall performance, especially reducing the pressure drop, in comparison to the geometries found in the literature.</p> ]]> Optimization of Electron Beam Generated Inclined Conical Pin Fins For Efficient Heat Sinks z. zeren k. hillewaert t. pinto a. ferhati m. serri m. malagutti doi: 10.2495/CMEM-V5-N1-66-75 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 66 10.2495/CMEM-V5-N1-66-75 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-66-75 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-55-65 In the last twenty years the modeling of heat transfer on gas turbine cascades has been based on computational fluid dynamic and turbulence modeling at sonic transition. The method is called Conjugate Flow and Heat Transfer (CHT). The quest for higher Turbine Inlet Temperature (TIT) to increase electrical efficiency makes radiative transfer the more and more effective in the leading edge and suction/pressure sides. Calculation of its amount and transfer towards surface are therefore needed. In this paper we decouple convection and radiation load, the first assumed from convective heat transfer data and the second by means of emissivity charts and analytical fits of heteropolar species as CO2 and H2O. Then we propose to solve the temperature profile in the blade through a quasi-two-dimensional power balance in the form of a second order partial differential equation which includes radiation and convection. Real cascades are cooled internally trough cool compressed air, so that we include in the power balance the effect of a heat sink or law of cooling that is up to the designer to test in order to reduce the thermal gradients and material temperature. The problem is numerically solved by means of the Finite Element Method (FEM) and, subsequently, some numerical simulations are also presented. 12-31-2016 <![CDATA[ <p>In the last twenty years the modeling of heat transfer on gas turbine cascades has been based on computational fluid dynamic and turbulence modeling at sonic transition. The method is called Conjugate Flow and Heat Transfer (CHT). The quest for higher Turbine Inlet Temperature (TIT) to increase electrical efficiency makes radiative transfer the more and more effective in the leading edge and suction/pressure sides. Calculation of its amount and transfer towards surface are therefore needed. In this paper we decouple convection and radiation load, the first assumed from convective heat transfer data and the second by means of emissivity charts and analytical fits of heteropolar species as CO₂ and H₂O. Then we propose to solve the temperature profile in the blade through a quasi-two-dimensional power balance in the form of a second order partial differential equation which includes radiation and convection. Real cascades are cooled internally trough cool compressed air, so that we include in the power balance the effect of a heat sink or law of cooling that is up to the designer to test in order to reduce the thermal gradients and material temperature. The problem is numerically solved by means of the Finite Element Method (FEM) and, subsequently, some numerical simulations are also presented.</p> ]]> Mathematical Modeling on Gas Turbine Blades/Vanes Under Variable Convective and Radiative Heat Flux with Tentative Different Laws of Cooling f. floris g. viglialoro doi: 10.2495/CMEM-V5-N1-55-65 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 55 10.2495/CMEM-V5-N1-55-65 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-55-65 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-44-54 To evaluate the wall heat losses in combustion vessel, an alternative to existing macroscopic models of heat transfer is suggested. This study aims to provide a physical approach for wall heat transfer based on kinetic theory of gases to describe the conduction phenomena between gas particles and the cold wall in short scales. The model mentioned is implemented in a code simulating combustion in a constant volume spherical chamber. 12-31-2016 <![CDATA[ <p>To evaluate the wall heat losses in combustion vessel, an alternative to existing macroscopic models of heat transfer is suggested. This study aims to provide a physical approach for wall heat transfer based on kinetic theory of gases to describe the conduction phenomena between gas particles and the cold wall in short scales. The model mentioned is implemented in a code simulating combustion in a constant volume spherical chamber.</p> ]]> Modeling of Unsteady Heat Transfer by Impact Between Gas Particles and A Cold Wall in A Spherical Combustion Vessel t. kasraoui k. joulain r. bertossi m. bellenoue b. boust j. sotton doi: 10.2495/CMEM-V5-N1-44-54 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 44 10.2495/CMEM-V5-N1-44-54 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-44-54 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-34-43 We report on the development of measurement system for characterizing physico-chemical properties of colloidal liquids used in heat transfer applications. In future thermal management, colloids consisting of micro- and nano-sized particles will play major roles in heat transfer for thermal storage and heat- transfer enhancement. In these applications, an important issue is the dispersion stability of colloidal particles. The functionality of the colloidal liquids becomes deteriorated when the particles aggregate and turn into sedimentation. The dispersion of colloidal liquid is maintained by the interaction of electrokinetic forces acting on the particles. The electrostatic state of the surface of a particle is represented by zeta potential, which represents the electrical potential difference between the particle surface and the surrounding. The zeta potential can be measured from the mobility of colloidal particles under electrophoresis. We use a pair of evanescent waves for measuring the zeta potential of colloidal particles. An evanescent wave propagates along an interface and exponentially attenuates away from it. The use of evanescent waves can achieve a spatial resolution smaller than a micrometer, which is not feasible with a conventional optical system whose resolution is bounded by diffraction limit. We describe the principle and design of the measurement system. A prototype measurement system was developed in the laboratory. We report on the development and performance of the system for characterizing col- loidal particles for heat transfer applications. 12-31-2016 <![CDATA[ <p><span style="color: rgb(35, 31, 32)">We report on the development of measurement system for characterizing physico-chemical properties of</span><span> </span>colloidal<span> </span>liquids<span> </span>used<span> </span>in<span> </span>heat<span> </span>transfer<span> </span>applications.<span> </span>In<span> </span>future<span> </span>thermal<span> </span>management,<span> </span>colloids<span> </span>consisting of micro- and nano-sized particles will play major roles in heat transfer for thermal storage and heat- transfer enhancement. In these applications, an important issue is the dispersion stability of colloidal particles. The functionality of the colloidal liquids becomes deteriorated when the particles aggregate and turn into sedimentation. The dispersion of colloidal liquid is maintained by the interaction of <span>elec</span>trokinetic<span> </span>forces<span> </span>acting<span> </span>on<span> </span>the<span> </span>particles.<span> </span>The<span> </span>electrostatic<span> </span>state<span> </span>of<span> </span>the<span> </span>surface<span> </span>of<span> </span>a<span> </span>particle<span> </span>is<span> </span>represented by zeta potential, which represents the electrical potential difference between the particle surface <span>and </span>the<span> </span>surrounding.<span> </span>The<span> </span>zeta<span> </span>potential<span> </span>can<span> </span>be<span> </span>measured<span> </span>from<span> </span>the<span> </span>mobility<span> </span>of<span> </span>colloidal<span> </span>particles<span> </span>under<span> </span>electrophoresis. We use a pair of evanescent waves for measuring the zeta potential of colloidal particles. An evanescent wave propagates along an interface and exponentially attenuates away from it. The <span>use </span>of evanescent waves can achieve a spatial resolution smaller than a micrometer, which is not feasible with a conventional optical system whose resolution is bounded by diffraction limit. We describe the principle and design of the measurement system. A prototype measurement system was developed in the laboratory. We report on the development and performance of the system for characterizing col- loidal particles for heat transfer applications.</p> ]]> Development of Measurement System Using Evanescent Waves for Characterizing Colloidal Liquids in Heat Transfer Applications k. shirai s. kaji t. kawanami s. hirasawa doi: 10.2495/CMEM-V5-N1-34-43 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 34 10.2495/CMEM-V5-N1-34-43 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-34-43 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-23-33 This paper focuses on thermal transport processes and systems and discusses their modeling, simulation, design and optimization to reduce the effect on the environment, reduce energy consumption and enhance product quality and productivity. These processes are generally quite complex and several challenges are encountered to obtain accurate and reliable results that can be used as the basis for design and optimization. Some major challenges are material properties, model validation, uncertain- ties in the governing parameters and operating conditions, complex combined transport mechanisms, and multiscale effects. Once accurate simulation results are obtained, these can be used to optimize the process to enhance the output. Reduction in energy and material consumption, as well as the effect on the environment, are of particular concern today. The paper discusses these aspects and presents a few practical systems by way of illustration. For example, working with the changing environment, the energy consumed by the thermal system for the cooling of data centers can be minimized. Similarly, other concerns and approaches are outlined. 12-31-2016 <![CDATA[ <p><span style="color: rgb(35, 31, 32)">This paper focuses on thermal transport processes and systems and discusses their modeling, simulation, design and optimization to reduce the effect on the environment, reduce energy consumption and enhance product quality and productivity. These processes are generally quite complex and several challenges are encountered to obtain accurate and reliable results that can be used as the basis </span><span>for </span>design and optimization. Some major challenges are material properties, model validation, <span>uncertain- </span>ties in the governing parameters and operating conditions, complex combined transport mechanisms, and<span> </span>multiscale<span> </span>effects.<span> </span>Once<span> </span>accurate<span> </span>simulation<span> </span>results<span> </span>are<span> </span>obtained,<span> </span>these<span> </span>can<span> </span>be<span> </span>used<span> </span>to<span> </span>optimize<span> </span>the process to enhance the output. Reduction in energy and material consumption, as well as the effect on the environment, are of particular concern today. The paper discusses these aspects and presents a few practical systems by way of illustration. For example, working with the changing environment, <span>the </span>energy consumed by the thermal system for the cooling of data centers can be minimized. Similarly, other concerns and approaches are outlined.</p> ]]> Simulation of Thermal Transport Processes to Reduce Environmental Impact and Improve Output yogesh jaluria doi: 10.2495/CMEM-V5-N1-23-33 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 23 10.2495/CMEM-V5-N1-23-33 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-23-33 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-13-22 The number of disposable molecular diagnostics tests in the IVD market has been growing rapidly and is bound to continue to grow in the near future. The internal complexity of these rapid tests increases with the complexity of the diagnostic assay implemented by them. Some assays require precise tem- perature control (±1°C –5°C) for an extended time (i.e. 15–60 minutes) for the reactions involved to run properly. Microheating components in them must meet strict criteria with respect to power con- sumption, physical size and cost. The proposed finite element model is intended to provide tools for in silico validation of device designs (geometries, structural materials), as well as to help in the interpre- tation of heat transfer processes inside the thermal system present in a molecular diagnostics device. The proposed model was developed for and validated with polyimide etched foil heating elements actively controlled via a mini-thermostat. The thermostat was designed for battery-based operation and implemented with open-source hardware (Arduino-compatible). Plastic test structures were created that emulated disposable Lab-on-a-Chip devices with microfluidic channels to hold liquid volumes on the scale of 0.1 mL. The experimental setup was demonstrated to maintain target temperatures over at least 30 minutes with at least ±1°C around the set point operated from batteries. Physical parameters of the resistive heating element used were fed into the finite element model and simulation results compared to the performance of the aforementioned experimental setup. 12-31-2016 <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The number of disposable molecular diagnostics tests in the IVD market has been growing rapidly</span><span> and </span>is bound to continue to grow in the near future. The internal complexity of these rapid tests increases with the complexity of the diagnostic assay implemented by them. Some assays require precise tem- perature control (±1°C –5°C) for an extended time (i.e. 15–60 minutes) for the reactions involved to run properly. Microheating components in them must meet strict criteria with respect to power <span>con- </span>sumption, physical size and cost. The proposed finite element model is intended to provide tools for <em><span>in </span>silico </em>validation of device designs (geometries, structural materials), as well as to help in the interpre- tation of heat transfer processes inside the thermal system present in a molecular diagnostics <span>device. </span>The proposed model was developed for and validated with polyimide etched foil heating elements actively<span> </span>controlled<span> </span>via<span> </span>a<span> </span>mini-thermostat.<span> </span>The<span> </span>thermostat<span> </span>was<span> </span>designed<span> </span>for<span> </span>battery-based<span> </span>operation<span> and </span>implemented<span> </span>with<span> </span>open-source<span> </span>hardware<span> </span>(Arduino-compatible).<span> </span>Plastic<span> </span>test<span> </span>structures<span> </span>were<span> </span>created<span> </span>that emulated disposable Lab-on-a-Chip devices with microfluidic channels to hold liquid volumes on the scale<span> </span>of<span> </span>0.1<span> </span>mL.<span> </span>The<span> </span>experimental<span> </span>setup<span> </span>was<span> </span>demonstrated<span> </span>to<span> </span>maintain<span> </span>target<span> </span>temperatures<span> </span>over<span> </span>at<span> least </span>30 minutes with at least ±1°C around the set point operated from batteries. Physical parameters of <span>the </span>resistive heating element used were fed into the finite element model and simulation results compared to the performance of the aforementioned experimental setup.</p> ]]> Finite Element Modelling for the Optimization of Microheating in Disposable Molecular Diagnostics t. pardy t. rang i. tulp doi: 10.2495/CMEM-V5-N1-13-22 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 13 10.2495/CMEM-V5-N1-13-22 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-13-22 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-1-12 Hundreds of young people have had limbs amputated after being wounded by civil wars, explosions or gunshots. Heat and perspiration within a prosthetic socket are the most common side effects of reduced quality life for prosthesis. Besides, the environment between liner and skin is an ideal host of residual limb skin problems such as contact dermatitis and bacterial infections. It is important to minimize the limiting heat transfer to improve amputee safety and comfort. Usually, when there is a skin problem, the treatment requires the amputee not to wear his/her prosthesis for an extended period of time. This functional loss can adversely affect the amputee’s physical, mental and emotional well-being. This work aims to highlight a number of important issues concerning the effect of thermal conditions on prosthetics to shed light on new design methods for prosthetics. 12-31-2016 <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Hundreds of young people have had limbs amputated after being wounded by civil wars, explosions</span><span> or </span>gunshots.<span> </span>Heat<span> </span>and<span> </span>perspiration<span> </span>within<span> </span>a<span> </span>prosthetic<span> </span>socket<span> </span>are<span> </span>the<span> </span>most<span> </span>common<span> </span>side<span> </span>effects<span> </span>of<span> </span>reduced quality life for prosthesis. Besides, the environment between liner and skin is an ideal host of residual limb skin problems such as contact dermatitis and bacterial infections. It is important to minimize the limiting heat transfer to improve amputee safety and comfort. Usually, when there is a skin problem, the treatment requires the amputee not to wear his/her prosthesis for an extended period of time. This functional loss can adversely affect the amputee’s physical, mental and emotional well-being. This work aims to highlight a number of important issues concerning the effect of thermal conditions <span>on </span>prosthetics to shed light on new design methods for prosthetics.</p> ]]> Thermal Assessment for Prostheses: State-of-the-Art Review sahar a. abbood zan wu bengt sundén doi: 10.2495/CMEM-V5-N1-1-12 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 1 10.2495/CMEM-V5-N1-1-12 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-1-12 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-0 Heat transfer continues to play a major role in new emerging areas such as sustainable development and reduction of greenhouse gases as well as for micro- and nano-scale structures and bio-engineering and in traditional areas like heat exchangers, gas turbine cooling, turbulent combustion and fires, electronics cooling, melting, solidification and many others. Tremendous advancements have been achieved during recent years.The Wessex Institute of Technology (WIT) Heat Transfer Conference Series aims to provide a forum for presentation and discussion of new approaches and applications of computational methods and experimental measurements to heat and mass transfer and related phenomena.Many relevant research topics were discussed during the Fourteenth International Conference on Simulation and Experiments in Heat Transfer and its Applications held in Ancona, Italy during September 2016. This special issue of the International Journal of Computational Methods and Experimental Measurements contains the edited versions of some selected papers presented at the Conference. The contributions reflect the quality and width of the topics covered in the conference.The guest editors would like to thank all the distinguished and well-known scientists who supported the Conference by serving on the International Scientific Advisory Committee, reviewing the submitted abstracts and papers. The excellent administrative work of the conference secretariat at WIT is greatly appreciated and the efficient co-operation and encouragement by the staff at WIT Press were essential in producing this special issue.| 12-31-2016 <![CDATA[ <p>Heat transfer continues to play a major role in new emerging areas such as sustainable development and reduction of greenhouse gases as well as for micro- and nano-scale structures and bio-engineering and in traditional areas like heat exchangers, gas turbine cooling, turbulent combustion and fires, electronics cooling, melting, solidification and many others. Tremendous advancements have been achieved during recent years.</p><p>The Wessex Institute of Technology (WIT) Heat Transfer Conference Series aims to provide a forum for presentation and discussion of new approaches and applications of computational methods and experimental measurements to heat and mass transfer and related phenomena.</p><p>Many relevant research topics were discussed during the Fourteenth International Conference on Simulation and Experiments in Heat Transfer and its Applications held in Ancona, Italy during September 2016. This special issue of the International Journal of Computational Methods and Experimental Measurements contains the edited versions of some selected papers presented at the Conference. The contributions reflect the quality and width of the topics covered in the conference.</p><p>The guest editors would like to thank all the distinguished and well-known scientists who supported the Conference by serving on the International Scientific Advisory Committee, reviewing the submitted abstracts and papers. The excellent administrative work of the conference secretariat at WIT is greatly appreciated and the efficient co-operation and encouragement by the staff at WIT Press were essential in producing this special issue.|</p> ]]> Preface bengt sundén carlos brebbia doi: 10.2495/CMEM-V5-N1-0 International Journal of Computational Methods and Experimental Measurements 12-31-2016 International Journal of Computational Methods and Experimental Measurements 12-31-2016 2017 5 1 Article 0 10.2495/CMEM-V5-N1-0 https://www.acadlore.com/article/IJCMEM/2017_5_1/CMEM-V5-N1-0 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-615-624 The process of cooling caused by a water droplet contacting a surface has been extensively reported in the literature; however, the effect of surface wettability on the outcome of the cooling rate has yet to be analyzed. Due to optical limitations inside a liquid droplet, a three-dimensional (3D) computational fluid dynamics (CFD) model, including coupling between multiphase flow and the conjugated heat transfer module was developed to simulate the impact, spreading and transient heat transfer between a cold-water droplet and a heated surface. The total heat transfer results were calculated for both superhydrophobic and hydrophilic surfaces. The Navier-Stokes equation expressing the flow distribution of the liquid and the gas, coupled with the volume of fluid (VOF) method for tracking the liquid interface, was solved numerically using the finite volume methodology. The grid dependency test was examined for the 3D model, even though the convergence of the results was not exact. The 2 mm diameter water droplet with the Weber numbers 7, 25 and 62, which correspond to non-splashing regimes, were impinged onto two different surfaces. We showed that spray cooling on a superhydrophobic substrate was capable of improving the efficiency of the cooling process up to 40% compared to that of a hydrophilic surface. Additionally, the critical Weber regime was obtained for the optimal heat transfer between the droplet and the two substrates. 11-29-2016 <![CDATA[ <p>The process of cooling caused by a water droplet contacting a surface has been extensively reported in the literature; however, the effect of surface wettability on the outcome of the cooling rate has yet to be analyzed. Due to optical limitations inside a liquid droplet, a three-dimensional (3D) computational fluid dynamics (CFD) model, including coupling between multiphase flow and the conjugated heat transfer module was developed to simulate the impact, spreading and transient heat transfer between a cold-water droplet and a heated surface. The total heat transfer results were calculated for both superhydrophobic and hydrophilic surfaces. The Navier-Stokes equation expressing the flow distribution of the liquid and the gas, coupled with the volume of fluid (VOF) method for tracking the liquid interface, was solved numerically using the finite volume methodology. The grid dependency test was examined for the 3D model, even though the convergence of the results was not exact. The 2 mm diameter water droplet with the Weber numbers 7, 25 and 62, which correspond to non-splashing regimes, were impinged onto two different surfaces. We showed that spray cooling on a superhydrophobic substrate was capable of improving the efficiency of the cooling process up to 40% compared to that of a hydrophilic surface. Additionally, the critical Weber regime was obtained for the optimal heat transfer between the droplet and the two substrates.</p> ]]> Numerical Study of the Effect of Surface Wettability on Performance of the Spray Cooling Process r. attarzadeh a. dolatabadi doi: 10.2495/CMEM-V4-N4-615-624 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 615 10.2495/CMEM-V4-N4-615-624 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-615-624 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-604-614 The Czochralski crystal growth manufacturing process results in small periodic and undesirable fluctuations in the crystal diameter under certain conditions. These fluctuations have strong, non-linear characteristics and are likely to appear at combinations of critical values of certain parameters, such as the rotational velocity, the ratio of crystal radius to crucible radius, and the temperature gradient.This paper uses perturbation theory to try to identify the critical combinations of parameters that lead to these fluctuations. Firstly, the zero and first-order equations are obtained. Secondly, numer-ically-based steady-state solutions of these equations are calculated, and finally, the stability of the steady-state solutions is examined. It is observed that the steady-state solutions do not exhibit any unusual patterns for any values of the configuration parameters. Furthermore, all the steady-state solutions are found to be stable for all initial conditions; therefore, the steady-state solutions and the analysis of their stability did not indicate the source of the observed fluctuations. This analysis suggests that a better approximation of the equations such as second order perturbation analysis may be needed to identify the conditions that lead to the observed fluctuations. 11-29-2016 <![CDATA[ <p>The Czochralski crystal growth manufacturing process results in small periodic and undesirable fluctuations in the crystal diameter under certain conditions. These fluctuations have strong, non-linear characteristics and are likely to appear at combinations of critical values of certain parameters, such as the rotational velocity, the ratio of crystal radius to crucible radius, and the temperature gradient.</p><p>This paper uses perturbation theory to try to identify the critical combinations of parameters that lead to these fluctuations. Firstly, the zero and first-order equations are obtained. Secondly, numer-ically-based steady-state solutions of these equations are calculated, and finally, the stability of the steady-state solutions is examined. It is observed that the steady-state solutions do not exhibit any unusual patterns for any values of the configuration parameters. Furthermore, all the steady-state solutions are found to be stable for all initial conditions; therefore, the steady-state solutions and the analysis of their stability did not indicate the source of the observed fluctuations. This analysis suggests that a better approximation of the equations such as second order perturbation analysis may be needed to identify the conditions that lead to the observed fluctuations.</p> ]]> Stability Analysis of the First-Order Steady- State Solution in the Czochralski Crystal Growth Process Using Perturbation Techniques najib georges arthur david snider camille amine issa doi: 10.2495/CMEM-V4-N4-604-614 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 604 10.2495/CMEM-V4-N4-604-614 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-604-614 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-594-603 Nowadays open-source CFD codes provide suitable environments for implementation and testing low-dissipative algorithms typically used for turbulence simulation. Moreover these codes produce a reliable tool to test high-fidelity numerics on unstructured grids, which are particularly appealing for industrial applications. Therefore in this work we have developed several solvers for incompressible Navier-Stokes equations (NSE) based on high-order explicit and implicit Runge-Kutta (RK) schemes for time-integration. Note that for NSE space discretization the numerical technology available within OpenFOAM (Open-source Field Operation And Manipulation) library was used.Specifically in this work we have considered explicit RK projected type schemes for index 2 DAE system and L-stable Singly Diagonally Implicit Runge-Kutta (SDIRK) techniques. In the latter case an iterated PISO-like procedure based on Rhie-Chow correction was used for handling pressure-velocity coupling within each RK stage. The accuracy of the considered algorithms was evaluated studying the Taylor-Green vortex. Moreover several benchmark solutions have been computed in order to assess the reliability, the accuracy and the robustness of the presented solvers. 11-29-2016 <![CDATA[ <p>Nowadays open-source CFD codes provide suitable environments for implementation and testing low-dissipative algorithms typically used for turbulence simulation. Moreover these codes produce a reliable tool to test high-fidelity numerics on unstructured grids, which are particularly appealing for industrial applications. Therefore in this work we have developed several solvers for incompressible Navier-Stokes equations (NSE) based on high-order explicit and implicit Runge-Kutta (RK) schemes for time-integration. Note that for NSE space discretization the numerical technology available within OpenFOAM (Open-source Field Operation And Manipulation) library was used.</p><p>Specifically in this work we have considered explicit RK projected type schemes for index 2 DAE system and L-stable Singly Diagonally Implicit Runge-Kutta (SDIRK) techniques. In the latter case an iterated PISO-like procedure based on Rhie-Chow correction was used for handling pressure-velocity coupling within each RK stage. The accuracy of the considered algorithms was evaluated studying the Taylor-Green vortex. Moreover several benchmark solutions have been computed in order to assess the reliability, the accuracy and the robustness of the presented solvers.</p> ]]> Development of Openfoam Solvers for Incompressible Navier–stokes Equations Based on High-Order Runge–kutta Schemes v. d’alessandro a. zoppi l. binci r. ricci doi: 10.2495/CMEM-V4-N4-594-603 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 594 10.2495/CMEM-V4-N4-594-603 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-594-603 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-583-593 The characteristics of the measurement capacity of air-coupled ultrasonic sensor influenced by the incident angle were investigated analytically and experimentally. The optimized incident angle between ultrasound and test pipe was determined. The air-coupled ultrasonic sensor with this determined incident angle was applied to the flowrate measurement in the aluminium pipe. The measurement results were compared to those obtained by using the electromagnetic flowmeter. Since the measurement results show good linearity, the capacity of the air-coupled ultrasonic flowmeter is revealed. 11-29-2016 <![CDATA[ <p>The characteristics of the measurement capacity of air-coupled ultrasonic sensor influenced by the incident angle were investigated analytically and experimentally. The optimized incident angle between ultrasound and test pipe was determined. The air-coupled ultrasonic sensor with this determined incident angle was applied to the flowrate measurement in the aluminium pipe. The measurement results were compared to those obtained by using the electromagnetic flowmeter. Since the measurement results show good linearity, the capacity of the air-coupled ultrasonic flowmeter is revealed.</p> ]]> Flowrate Measurement on Metal Pipes by Air-Coupled Ultrasound keisuke tsukada hiroshige kikura doi: 10.2495/CMEM-V4-N4-583-593 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 583 10.2495/CMEM-V4-N4-583-593 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-583-593 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-573-582 Surface cleaning prior to coating and fabrication processes is an important process to ensure the quality and proper functioning of the products. The current work involves the modeling of a cleaning process where viscous media is removed from surfaces using mechanical force from impinging water jets. The jets are mounted on a rotating nozzle carrier, which combine the normal force with increased tangential force resulting in the removal of oil present in the grooves of metal surfaces.The modeling of such a process is performed with the volume of fluid (VOF) method with an open source Computational Fluid Dynamics (CFD) code Open-FOAM®. Rectangular grooves, which represent an idealized form of roughness are considered for numerical analysis. The oil present in the roughness grooves is resolved by the computational mesh.The inlet is modified to model the phenomenon of rotating jets. In order to model the effect of rotating jets, a reference vector is transformed by a time-dependent rotational tensor. All the faces which make a certain angle (opening angle) with the reference vector are activated. This results in the formation of jets with a thickness which can be controlled by the opening angle. The numerical model is used to study the influence of the frequency of rotation, nozzle exit velocity, viscosity of oil and the aspect ratio of the grooves on surface cleaning. An impinging turbulent jet is modeled using the k-epsilon turbulence model.Finally, the CFD simulations are qualitatively compared with a previously developed semi-empirical model and experiments conducted in an industrial setup. The tendencies of oil removal due to the effect of the process parameters observed in the simulation are in close agreement with the semi-empirical model and experimental results. Thus, the cleaning model can be used to conduct sensitivity analysis to achieve an optimal performance of the cleaning process. 11-29-2016 <![CDATA[ <p>Surface cleaning prior to coating and fabrication processes is an important process to ensure the quality and proper functioning of the products. The current work involves the modeling of a cleaning process where viscous media is removed from surfaces using mechanical force from impinging water jets. The jets are mounted on a rotating nozzle carrier, which combine the normal force with increased tangential force resulting in the removal of oil present in the grooves of metal surfaces.</p><p>The modeling of such a process is performed with the volume of fluid (VOF) method with an open source Computational Fluid Dynamics (CFD) code Open-FOAM®. Rectangular grooves, which represent an idealized form of roughness are considered for numerical analysis. The oil present in the roughness grooves is resolved by the computational mesh.</p><p>The inlet is modified to model the phenomenon of rotating jets. In order to model the effect of rotating jets, a reference vector is transformed by a time-dependent rotational tensor. All the faces which make a certain angle (opening angle) with the reference vector are activated. This results in the formation of jets with a thickness which can be controlled by the opening angle. The numerical model is used to study the influence of the frequency of rotation, nozzle exit velocity, viscosity of oil and the aspect ratio of the grooves on surface cleaning. An impinging turbulent jet is modeled using the k-epsilon turbulence model.</p><p>Finally, the CFD simulations are qualitatively compared with a previously developed semi-empirical model and experiments conducted in an industrial setup. The tendencies of oil removal due to the effect of the process parameters observed in the simulation are in close agreement with the semi-empirical model and experimental results. Thus, the cleaning model can be used to conduct sensitivity analysis to achieve an optimal performance of the cleaning process.</p> ]]> Numerical Modeling and Analysis of Viscous Media Removal from Grooved Surfaces with Rotating Impinging Jets c. mohan kumar p. elsen b. berger u. janoske doi: 10.2495/CMEM-V4-N4-573-582 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 573 10.2495/CMEM-V4-N4-573-582 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-573-582 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-561-572 Particle interactions in highly-viscous nonlinear and linear shear flows play an important role in a variety of applications including composite materials processing, microfluidics, chromatography, and particle resuspension, to name a few. Binary interactions among particles can provide information used in rheological models for suspension flows such as migration rates and self-diffusivity. In past numeri- cal studies, particle roughness has been treated, for the most part, as a constant, static quantity. In the current study, roughness is treated as a stochastic parameter. Hence, quantities such as dispersion, net particle migration, and self-diffusivity also become stochastic parameters. Numerical simulations are performed using a semi-analytic solution for the motion of two particles in an arbitrary unbounded flow field to determine the effects of random particle roughness. 11-29-2016 <![CDATA[ <p>Particle interactions in highly-viscous nonlinear and linear shear flows play an important role in a variety of applications including composite materials processing, microfluidics, chromatography, and particle resuspension, to name a few. Binary interactions among particles can provide information used in rheological models for suspension flows such as migration rates and self-diffusivity. In past numeri- cal studies, particle roughness has been treated, for the most part, as a constant, static quantity. In the current study, roughness is treated as a stochastic parameter. Hence, quantities such as dispersion, net particle migration, and self-diffusivity also become stochastic parameters. Numerical simulations are performed using a semi-analytic solution for the motion of two particles in an arbitrary unbounded flow field to determine the effects of random particle roughness.</p> ]]> The Effects of Surface Roughness on Particle Dispersion, Migration, And Self-Diffusivity in Linear and Nonlinear Shear Flows m. darbeheshti j. stokan u. dam m. s. ingber doi: 10.2495/CMEM-V4-N4-561-572 International Journal of Computational Methods and Experimental Measurements 11-29-2016 International Journal of Computational Methods and Experimental Measurements 11-29-2016 2016 4 4 Article 561 10.2495/CMEM-V4-N4-561-572 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-561-572 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-554-560 The compatibility of the semiempirical turbulence theory of L. Prandtl with the actual flow pattern in a turbulent boundary layer is considered in this article, and, based on this theory, the final calculation results of the boundary layer are analyzed. These show that the accepted additional conditions and relationships, which integrate the differential equation of L. Prandtl, associating the turbulent stresses in the boundary layer with the transverse velocity gradient, are fulfilled only in the near-wall region, where the mentioned equation loses meaning, and are inconsistent with the physical meaning in the main part of integration.It is noted that an introduced concept regarding the presence of a laminar sublayer between the wall and the turbulent boundary layer is the way to give a physical meaning to the logarithmic velocity profile.It shows that coincidence of the experimental data with the actual logarithmic profile is obtained as a result of the use not of a particular physical value, as an argument, but of a function of this value. In this way, the coincident experimental points in general are concerned with different sections of the boundary layer. Accordingly, the informational value of the comparison of the calculations and the experiment given in the literature is actually eliminated. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The compatibility of the semiempirical turbulence theory of L. Prandtl with the actual flow pattern </span><span>in </span>a turbulent boundary layer is considered in this article, and, based on this theory, the final calculation results of the boundary layer are analyzed. These show that the accepted additional conditions <span>and </span>relationships, which integrate the differential equation of L. Prandtl, associating the turbulent stresses in the boundary layer with the transverse velocity gradient, are fulfilled only in the near-wall region, where the mentioned equation loses meaning, and are inconsistent with the physical meaning in the main part of integration.</p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">It is noted that an introduced concept regarding the presence of a laminar sublayer between the wall and the turbulent boundary layer is the way to give a physical meaning to the logarithmic velocity profile.</span></p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">It shows that coincidence of the experimental data with the actual logarithmic profile is obtained</span><span> </span>as a result of the use not of a particular physical value, as an argument, but of a function of this value. In this way, the coincident experimental points in general are concerned with different sections of the boundary layer. Accordingly, the informational value of the comparison of the calculations and the experiment given in the literature is actually eliminated.</p> ]]> On The Compatibility of a Logarithmic Turbulent Boundary Layer Velocity Profile with Experimental Data a. zaryankin a. rogalev v. kindra g. kurdiukova a. vegera doi: 10.2495/CMEM-V4-N4-554-560 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 554 10.2495/CMEM-V4-N4-554-560 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-554-560 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-543-553 A numerical formulation of flow-induced instability modelling of laminated anisotropic pipelines is derived. The analysis is based on fluid-structure interaction equations and FEA. Taking into account the flow parameters and the material properties, critical flow velocities causing instability are calculated for fibre-reinforced polymeric (FRP) pipelines resting on elastic supports. A parametric study of the effect of fibre orientation, stiffness of elastic supports and span length between supports is carried out. The results are commented and discussed. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">A numerical formulation of flow-induced instability modelling of laminated anisotropic pipelines is derived.</span><span> </span>The<span> </span>analysis<span> </span>is<span> </span>based<span> </span>on<span> </span>fluid-structure<span> </span>interaction<span> </span>equations<span> </span>and<span> </span>FEA.<span> </span>Taking<span> </span>into<span> </span>account<span> the </span>flow<span> </span>parameters<span> </span>and<span> </span>the<span> </span>material<span> </span>properties,<span> </span>critical<span> </span>flow<span> </span>velocities<span> </span>causing<span> </span>instability<span> </span>are<span> </span>calculated<span> for </span>fibre-reinforced<span> </span>polymeric<span> </span>(FRP)<span> </span>pipelines<span> </span>resting<span> </span>on<span> </span>elastic<span> </span>supports.<span> </span>A<span> </span>parametric<span> </span>study<span> </span>of<span> </span>the<span> </span>effect of fibre orientation, stiffness of elastic supports and span length between supports is carried out. The results are commented and discussed.</p> ]]> Flow-Induced Instability of Multi-Layered Anisotropic Pipelines d.g. pavlou doi: 10.2495/CMEM-V4-N4-543-553 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 543 10.2495/CMEM-V4-N4-543-553 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-543-553 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-532-542 In this paper, we study the problem of scattering of surface water waves by a thin circular arc shaped porous plate submerged in the deep ocean. The problem is formulated in terms of a hypersingular integral equation of the second kind in terms of an unknown function representing the difference of potential function across the curved barrier. The hypersingular integral equation is then solved by a collocation method after expanding the unknown function in terms of Chebyshev polynomials of the second kind. Using the solution of the hyper-singular integral equation, the reflection coefficient, trans- mission coefficient and energy dissipation coefficient are computed and depicted graphically against the wave number. Known results for the rigid curved barrier are recovered. It is observed that the poros- ity of the barrier reduces the reflection and transmission of the waves and enhances the dissipation of wave energy. The reflection coefficient and dissipation of wave energy decreases as the length of the porous curved barrier increases. Also the reflection coefficient is almost independent of the inertial force coefficient of the material of the porous barrier. However, the inertial force coefficient of the material of the porous barrier enhances transmission and reduces dissipation of wave energy. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">In this paper, we study the problem of scattering of surface water waves by a thin circular arc shaped porous plate submerged in the deep ocean. The problem is formulated in terms of a hypersingular integral equation of the second kind in terms of an unknown function representing the difference </span><span>of </span>potential function across the curved barrier. The hypersingular integral equation is then solved by <span>a </span>collocation method after expanding the unknown function in terms of Chebyshev polynomials of the second<span> </span>kind.<span> </span>Using<span> </span>the<span> </span>solution<span> </span>of<span> </span>the<span> </span>hyper-singular<span> </span>integral<span> </span>equation,<span> </span>the<span> </span>reflection<span> </span>coefficient,<span> </span>trans- mission coefficient and energy dissipation coefficient are computed and depicted graphically against the<span> </span>wave<span> </span>number.<span> </span>Known<span> </span>results<span> </span>for<span> </span>the<span> </span>rigid<span> </span>curved<span> </span>barrier<span> </span>are<span> </span>recovered.<span> </span>It<span> </span>is<span> </span>observed<span> </span>that<span> </span>the<span> poros- </span>ity of the barrier reduces the reflection and transmission of the waves and enhances the dissipation <span>of </span>wave energy. The reflection coefficient and dissipation of wave energy decreases as the length of <span>the </span>porous curved barrier increases. Also the reflection coefficient is almost independent of the inertial force coefficient of the material of the porous barrier. However, the inertial force coefficient of <span>the </span>material of the porous barrier enhances transmission and reduces dissipation of wave energy.</p> ]]> Scattering of Water Waves by a Porous Circular Arc-Shaped Barrier Submerged in Ocean dibakar mondal sudeshna banerjea doi: 10.2495/CMEM-V4-N4-532-542 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 532 10.2495/CMEM-V4-N4-532-542 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-532-542 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-522-531 In this paper, a computational approach, based on the solution of Reynolds-averaged-Navier–Stokes (RANS) equations, to describe the flow within and around a diffuser augmented wind turbine (DAWT) is reported. In order to reduce the computational cost, the turbine is modeled as an actuator disc (AD) that imposes a resistance to the passage of the flow. The effect of the AD is modeled applying two body forces, upstream and downstream of the AD, such that they impose a desired pressure jump. Com- parison with experiments carried out in similar conditions shows a good agreement suggesting that the adopted methodology is able to carefully reproduce real flow features. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">In this paper, a computational approach, based on the solution of Reynolds-averaged-Navier–Stokes (RANS)</span><span> </span>equations,<span> </span>to<span> </span>describe<span> </span>the<span> </span>flow<span> </span>within<span> </span>and<span> </span>around<span> </span>a<span> </span>diffuser<span> </span>augmented<span> </span>wind<span> </span>turbine<span> (DAWT) </span>is reported. In order to reduce the computational cost, the turbine is modeled as an actuator disc (AD) that<span> </span>imposes<span> </span>a<span> </span>resistance<span> </span>to<span> </span>the<span> </span>passage<span> </span>of<span> </span>the<span> </span>flow.<span> </span>The<span> </span>effect<span> </span>of<span> </span>the<span> </span>AD<span> </span>is<span> </span>modeled<span> </span>applying<span> </span>two<span> body </span>forces, upstream and downstream of the AD, such that they impose a desired pressure jump. Com- parison with experiments carried out in similar conditions shows a good agreement suggesting that <span>the </span>adopted methodology is able to carefully reproduce real flow<span> </span>features.</p> ]]> Computational Study of Diffuser Augmented Wind Turbine Using Actuator Disc Force Method v.v. dighe f. avallone g.j.w. van bussel doi: 10.2495/CMEM-V4-N4-522-531 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 522 10.2495/CMEM-V4-N4-522-531 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-522-531 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-513-521 Diffuser Augmented Wind Turbines (DAWTs) have been a highlight of research in small size wind turbines due to their potential capability of exceeding Betz Limit. Bringing a wall in close proximity of blade tip may have strong influences on physics of tip leakage flow. In current study, the effect of the diffuser wall on tip leakage flow is examined. Different tip gap to diffuser radius ratios are numerically studied in a two dimensional domain. As tip leakage flow in DAWTs has not been studied before, the methodology for the current work is adopted from similar research in gas turbines. Obtained results indicate that as the tip gap to diffuser radius ratio is reduced from 0.067 to 0.02, tip leakage mass flow rate reduces to 6% and the total pressure loss increases by 56%. This behavior of tip leakage flow is further elaborated by discussing the flow physics in the gap region. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Diffuser Augmented Wind Turbines (DAWTs) have been a highlight of research in small size </span><span>wind </span>turbines<span> </span>due<span> </span>to<span> </span>their<span> </span>potential<span> </span>capability<span> </span>of<span> </span>exceeding<span> </span>Betz<span> </span>Limit.<span> </span>Bringing<span> </span>a<span> </span>wall<span> </span>in<span> </span>close<span> </span>proximity<span> </span>of blade tip may have strong influences on physics of tip leakage flow. In current study, the effect of the diffuser<span> </span>wall<span> </span>on<span> </span>tip<span> </span>leakage<span> </span>flow<span> </span>is<span> </span>examined.<span> </span>Different<span> </span>tip<span> </span>gap<span> </span>to<span> </span>diffuser<span> </span>radius<span> </span>ratios<span> </span>are<span> </span>numerically studied in a two dimensional domain. As tip leakage flow in DAWTs has not been studied before, the methodology for the current work is adopted from similar research in gas turbines. Obtained results indicate that as the tip gap to diffuser radius ratio is reduced from 0.067 to 0.02, tip leakage mass <span>flow </span>rate reduces to 6% and the total pressure loss increases by 56%. This behavior of tip leakage flow is further elaborated by discussing the flow physics in the gap<span> </span>region.</p> ]]> Effect of Wall Proximity on Cross Flow Tip Leakage in Diffuser Augmented Wind Turbines (DAWTs) a.s. dar z.m. sheikh s.h.w. gilani doi: 10.2495/CMEM-V4-N4-513-521 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 513 10.2495/CMEM-V4-N4-513-521 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-513-521 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-502-512 This study presents an experimental investigation on a diffuser augmented wind turbine (DAWT). A screen mesh is used to simulate the energy extraction mechanisms of a wind turbine in experiment. Different screen porosities corresponding to different turbine loading coefficients are tested. Measure- ments of the axial force and of the velocity distribution in radial direction are reported. The general purpose is to highlight the dependency between the diffuser and the screen, and to compare the radial velocity distributions in the diffuser between unloaded and loaded conditions. It is shown that the thrust on an unshrouded screen is lower than on a shrouded screen, under the same inflow condition. More- over, the thrust on the diffuser largely depends on the screen loading. For the present configuration, the thrust on the screen with high loading coefficient contributes for more than 70% of the total thrust on the DAWT. Smoke visualizations and radial velocity profiles reveal that the high loading screen induces flow separation on the outer surface of the diffuser, justifying the results of the thrust measurements. It is also inferred that the flow separation leads to loss of thrust and has a great effect on the total pressure drag. It should be emphasized that the experimental results indicate that the flow field around the diffuser is strongly affected by the choice of screen porosity, that is, turbine loading. And that, the thrust coef- ficient of the diffuser does not show a linear dependence on the thrust coefficient of the screen. The axial momentum theory, therefore, is not a solid predictor for DAWT performance with high loaded screens. <![CDATA[ <p><span style="color: rgb(35, 31, 32); font-family: Times New Roman, serif">This study presents an experimental investigation on a diffuser augmented wind turbine (DAWT).</span><span> </span>A screen mesh is used to simulate the energy extraction mechanisms of a wind turbine in experiment. Different screen porosities corresponding to different turbine loading coefficients are tested. Measure- ments of the axial force and of the velocity distribution in radial direction are reported. The general purpose is to highlight the dependency between the diffuser and the screen, and to compare the radial velocity<span> </span>distributions<span> </span>in<span> </span>the<span> </span>diffuser<span> </span>between<span> </span>unloaded<span> </span>and<span> </span>loaded<span> </span>conditions.<span> </span>It<span> </span>is<span> </span>shown<span> </span>that<span> </span>the<span> </span>thrust on an unshrouded screen is lower than on a shrouded screen, under the same inflow condition. More- over,<span> </span>the<span> </span>thrust<span> </span>on<span> </span>the<span> </span>diffuser<span> </span>largely<span> </span>depends<span> </span>on<span> </span>the<span> </span>screen<span> </span>loading.<span> </span>For<span> </span>the<span> </span>present<span> </span>configuration,<span> </span>the thrust on the screen with high loading coefficient contributes for more than 70% of the total thrust on the<span> </span>DAWT.<span> </span>Smoke<span> </span>visualizations<span> </span>and<span> </span>radial<span> </span>velocity<span> </span>profiles<span> </span>reveal<span> </span>that<span> </span>the<span> </span>high<span> </span>loading<span> </span>screen<span> </span>induces flow<span> </span>separation<span> </span>on<span> </span>the<span> </span>outer<span> </span>surface<span> </span>of<span> </span>the<span> </span>diffuser,<span> </span>justifying<span> </span>the<span> </span>results<span> </span>of<span> </span>the<span> </span>thrust<span> </span>measurements.<span> </span>It is<span> </span>also<span> </span>inferred<span> </span>that<span> </span>the<span> </span>flow<span> </span>separation<span> </span>leads<span> </span>to<span> </span>loss<span> </span>of<span> </span>thrust<span> </span>and<span> </span>has<span> </span>a<span> </span>great<span> </span>effect<span> </span>on<span> </span>the<span> </span>total<span> </span>pressure drag.<span> </span>It<span> </span>should<span> </span>be<span> </span>emphasized<span> </span>that<span> </span>the<span> </span>experimental<span> </span>results<span> </span>indicate<span> </span>that<span> </span>the<span> </span>flow<span> </span>field<span> </span>around<span> </span>the<span> </span>diffuser is strongly affected by the choice of screen porosity, that is, turbine loading. And that, the thrust coef- ficient<span> </span>of<span> </span>the<span> </span>diffuser<span> </span>does<span> </span>not<span> </span>show<span> </span>a<span> </span>linear<span> </span>dependence<span> </span>on<span> </span>the<span> </span>thrust<span> </span>coefficient<span> </span>of<span> </span>the<span> </span>screen.<span> </span>The<span> </span>axial momentum<span> </span>theory,<span> </span>therefore,<span> </span>is<span> </span>not<span> </span>a<span> </span>solid<span> </span>predictor<span> </span>for<span> </span>DAWT<span> </span>performance<span> </span>with<span> </span>high<span> </span>loaded<span> </span>screens.</p> ]]> Experimental Study of Flow Field of an Aerofoil Shaped Diffuser with a porous Screen Simulating the Rotor j. tang f. avallone g.j.w. van bussel doi: 10.2495/CMEM-V4-N4-502-512 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 502 10.2495/CMEM-V4-N4-502-512 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-502-512 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-493-501 We present an experimental investigation of water flow around a hydrofoil with a superhydrophobic patterned surface. The experimental setup uses a water tunnel to measure the drag over the hydrofoil and acquire velocity field measurements using particle image velocimetry (PIV). Drag reduction on the order of 10% or higher was observed on hydrofoils with irregular surface textures combined with super-hydrophobic coating, leading to effective Navier slip on the surface. However, we report that other macroscopic flow characteristics, including the stall angle, are also changed by application of the coating. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">We present an experimental investigation of water flow around a hydrofoil with a superhydrophobic patterned surface. The experimental setup uses a water tunnel to measure the drag over the hydrofoil and acquire velocity field measurements using particle image velocimetry (PIV). Drag reduction </span><span>on </span>the order of 10% or higher was observed on hydrofoils with irregular surface textures combined with super-hydrophobic coating, leading to effective Navier slip on the surface. However, we report <span>that </span>other<span> </span>macroscopic<span> </span>flow<span> </span>characteristics,<span> </span>including<span> </span>the<span> </span>stall<span> </span>angle,<span> </span>are<span> </span>also<span> </span>changed<span> </span>by<span> </span>application<span> </span>of<span> the </span>coating.</p> ]]> Flow Pattern Alteration Near A Hydrofoil Due to Effective Slip: An Experimental Study salil gogte andrea mammoli peter vorobieff doi: 10.2495/CMEM-V4-N4-493-501 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 493 10.2495/CMEM-V4-N4-493-501 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-493-501 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-484-492 Cavitation is the formation of vapour cavities in a liquid due to a local low pressure. The traditional cavitation number is used to predict the occurrence of cavitation in liquid flows through devices such as pumps, propellers or dam spillways. However, this number can only be applied when cavitation is produced by changes in the dynamic and static pressure in a liquid flow. There are other means to pro- duce cavitation where the traditional cavitation number cannot be applied. The purpose of this research is to formulate a new dimensionless number valid to predict cavitation in some scenarios where the traditional cavitation number fails. The ‘tube-arrest’ method produces cavitation by subjecting a col- umn of liquid to a high acceleration without the need of any velocity between the liquid and the tube. In this scenario, the traditional number is not useful due to the low values of relative velocity between liquid and walls. However, the dimensionless number reported here predicts accurately the occurrence of cavitation in the ‘tube-arrest’ method, as it is shown by Finite Element Method analysis. There is another scenario where the dimensionless number is tested successfully; that is, in the bulk of a liquid downstream of a closing valve. A systematic comparison between the values of the dimensionless number and the occurrence of cavitation predicted by the FEM analysis is given. On the other hand, the values of the traditional cavitation number are calculated and it is shown that these values are meaning- less in these scenarios. In contrast, the agreement between the prediction of the dimensionless number and the simulations is excellent. It is concluded that the new dimensionless number predicts cavitation in scenarios where the traditional number is meaningless. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Cavitation is the formation of vapour cavities in a liquid due to a local low pressure. The traditional cavitation number is used to predict the occurrence of cavitation in liquid flows through devices such as pumps, propellers or dam spillways. However, this number can only be applied when cavitation is produced by changes in the dynamic and static pressure in a liquid flow. There are other means to</span><span> </span>pro- duce<span> </span>cavitation<span> </span>where<span> </span>the<span> </span>traditional<span> </span>cavitation<span> </span>number<span> </span>cannot<span> </span>be<span> </span>applied.<span> </span>The<span> </span>purpose<span> </span>of<span> </span>this<span> </span>research is to formulate a new dimensionless number valid to predict cavitation in some scenarios where <span>the </span>traditional cavitation number fails. The ‘tube-arrest’ method produces cavitation by subjecting a col- umn of liquid to a high acceleration without the need of any velocity between the liquid and the tube. In this scenario, the traditional number is not useful due to the low values of relative velocity between liquid and walls. However, the dimensionless number reported here predicts accurately the occurrence of cavitation in the ‘tube-arrest’ method, as it is shown by Finite Element Method analysis. There is another scenario where the dimensionless number is tested successfully; that is, in the bulk of a liquid downstream of a closing valve. A systematic comparison between the values of the dimensionless number<span> </span>and<span> </span>the<span> </span>occurrence<span> </span>of<span> </span>cavitation<span> </span>predicted<span> </span>by<span> </span>the<span> </span>FEM<span> </span>analysis<span> </span>is<span> </span>given.<span> </span>On<span> </span>the<span> </span>other<span> </span>hand,<span> the </span>values<span> </span>of<span> </span>the<span> </span>traditional<span> </span>cavitation<span> </span>number<span> </span>are<span> </span>calculated<span> </span>and<span> </span>it<span> </span>is<span> </span>shown<span> </span>that<span> </span>these<span> </span>values<span> </span>are<span> meaning- </span>less in these scenarios. In contrast, the agreement between the prediction of the dimensionless number and the simulations is excellent. It is concluded that the new dimensionless number predicts cavitation in scenarios where the traditional number is meaningless.</p> ]]> New Dimensionless Number to Predict Cavitation in Accelerated Fluid g. garcia-atance fatjo doi: 10.2495/CMEM-V4-N4-484-492 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 484 10.2495/CMEM-V4-N4-484-492 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-484-492 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-474-483 Effects of circulation on the evolution of vortex tubes and the associated response of near-wall flows in the shear of laminar boundary-layer flows are investigated using a model proposed by Hon and Walker (Hon, T.L. & Walker, J.D.A, Computers & Fluids, 20(3), pp. 343–358, 1991). Direct numerical simula- tions with freestream Mach number of 0.5 are conducted. Firstly, the dynamics of single hairpin vortex is investigated. Numerous secondary hairpin vortices, much more than previously reported, which are regularly aligned in the streamwise direction are allowed to be newly generated according to the shear-layer instability of the legs of an initial hairpin vortex. Small-scale turbulence is then produced when the circulation is sufficiently large. Secondly, a straight vortex tube model is investigated. Sinu- ous deformation of a shear layer, which leads to the generation of discrete hairpin vortices, becomes obvious especially near the upper region of the vortex tube. In order to quantify the initial instability triggering the generation of the secondary hairpin vortices, quasi-linear stability analysis is conducted. While only one unstable mode appears when the circulation is small, two modes, that is, off-wall mode and near-wall mode, appear when the circulation is large. The cases of circulation where the two modes appear correspond to those of circulation where the production of small-scale turbulence is observed in the simulations of the single hairpin vortex. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Effects</span><span> </span>of<span> </span>circulation<span> </span>on<span> </span>the<span> </span>evolution<span> </span>of<span> </span>vortex<span> </span>tubes<span> </span>and<span> </span>the<span> </span>associated<span> </span>response<span> </span>of<span> </span>near-wall<span> </span>flows<span> in </span>the<span> </span>shear<span> </span>of<span> </span>laminar<span> </span>boundary-layer<span> </span>flows<span> </span>are<span> </span>investigated<span> </span>using<span> </span>a<span> </span>model<span> </span>proposed<span> </span>by<span> </span>Hon<span> </span>and<span> Walker </span>(Hon,<span> </span>T.L.<span> </span>&<span> </span>Walker,<span> </span>J.D.A,<span> </span>Computers<span> </span>&<span> </span>Fluids,<span> </span>20(3),<span> </span>pp.<span> </span>343–358,<span> </span>1991).<span> </span>Direct<span> </span>numerical<span> </span>simula- tions<span> </span>with<span> </span>freestream<span> </span>Mach<span> </span>number<span> </span>of<span> </span>0.5<span> </span>are<span> </span>conducted.<span> </span>Firstly,<span> </span>the<span> </span>dynamics<span> </span>of<span> </span>single<span> </span>hairpin<span> </span>vortex is investigated. Numerous secondary hairpin vortices, much more than previously reported, <span>which </span>are regularly aligned in the streamwise direction are allowed to be newly generated according to the shear-layer instability of the legs of an initial hairpin vortex. Small-scale turbulence is then produced when the circulation is sufficiently large. Secondly, a straight vortex tube model is investigated. <span>Sinu- </span>ous deformation of a shear layer, which leads to the generation of discrete hairpin vortices, becomes obvious especially near the upper region of the vortex tube. In order to quantify the initial instability triggering the generation of the secondary hairpin vortices, quasi-linear stability analysis is conducted. While<span> </span>only<span> </span>one<span> </span>unstable<span> </span>mode<span> </span>appears<span> </span>when<span> </span>the<span> </span>circulation<span> </span>is<span> </span>small,<span> </span>two<span> </span>modes,<span> </span>that<span> </span>is,<span> </span>off-wall<span> </span>mode and<span> </span>near-wall<span> </span>mode,<span> </span>appear<span> </span>when<span> </span>the<span> </span>circulation<span> </span>is<span> </span>large.<span> </span>The<span> </span>cases<span> </span>of<span> </span>circulation<span> </span>where<span> </span>the<span> </span>two<span> </span>modes appear<span> </span>correspond<span> </span>to<span> </span>those<span> </span>of<span> </span>circulation<span> </span>where<span> </span>the<span> </span>production<span> </span>of<span> </span>small-scale<span> </span>turbulence<span> </span>is<span> </span>observed<span> </span>in the simulations of the single hairpin vortex.</p> ]]> Direct Numerical Simulation of A Straight Vortex Tube in A Laminar Boundary-Layer Flow k. matsuura doi: 10.2495/CMEM-V4-N4-474-483 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 474 10.2495/CMEM-V4-N4-474-483 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-474-483 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-464-473 A numerical study on the laminar vortex shedding frequency on a porous and partially porous circular tube has been made. Porous tubes characterised by an inner and outer diameter of the porous zone are subjected to a uniform flow. The porous region is divided in eight segments of 45° with a different porous structure. The porous behaviour has been modelled by a Darcy-equation. To ensure a laminar vortex shedding, the Reynolds number has been chosen between 40 and 200. The influence of the Reynolds number and the properties of the porous zone (thickness, pressure drop), characterised by a dimensionless thickness L and a Darcy number Da on vortex shedding frequency (dimensionless Strouhal number Sr) and volume flow through the porous zone (dimensionless volume flow P) has been analysed. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">A numerical study on the laminar vortex shedding frequency on a porous and partially porous circular tube has been made. Porous tubes characterised by an inner and outer diameter of the porous zone </span><span>are </span>subjected to a uniform flow. The porous region is divided in eight segments of 45° with a different porous structure. The porous behaviour has been modelled by a Darcy-equation. To ensure a laminar vortex shedding, the Reynolds number has been chosen between 40 and 200. The influence of <span>the </span>Reynolds number and the properties of the porous zone (thickness, pressure drop), characterised by<span> </span>a dimensionless thickness <span style="color: rgb(35, 31, 32); font-family: Symbol">L</span><span style="color: rgb(35, 31, 32)"> and a Darcy number </span><em><span style="color: rgb(35, 31, 32)">Da </span></em><span style="color: rgb(35, 31, 32)">on vortex shedding frequency (dimensionless Strouhal number </span><em><span style="color: rgb(35, 31, 32)">Sr) </span></em><span style="color: rgb(35, 31, 32)">and volume flow through the porous zone (dimensionless volume flow </span><span style="color: rgb(35, 31, 32); font-family: Symbol">P</span><span style="color: rgb(35, 31, 32)">) </span><span>has </span>been analysed.</p> ]]> Vortex Shedding Frequency of Porous Circular Tubes with Varying Porous Properties Along the Circumference u. janoske doi: 10.2495/CMEM-V4-N4-464-473 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 464 10.2495/CMEM-V4-N4-464-473 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-464-473 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-454-463 Suspensions of nanoscale particles and fluids have been recently subject of intense research, since it was proved that they considerably improve heat transfer capabilities of the fluid which can be crucial in several technological processes. Several applications can be found in the field of porous media flow, such as oil recovery systems, thermal and geothermal energy, nuclear reactors cooling. Since nanofluids are a mixture of a solid and fluid phase, in general, the two phase mathematical model would be the most appropriate to use. However, due to very small size of nanoparticles (1–100 nm) can be assumed, that they behave as a water molecule and a single phase model along with empirical correlations for nanofluid properties can be used. In the present study a convective flow through porous cavity fully saturated with nanofluid is analyzed in detail using the single phase mathematical model based on the Navier-Stokes equations taking into account the non-Darcy parameters. The mathematical model is written at a macroscopic level enabling the simulation of the porous media flow. The solutions are obtained with the in house numerical code based on the Boundary Element Method, which was already proved to have some unique advantages when considering fluid flow problems in different configurations. The effects of the presence of different types of nanoparticles as well as the porous matrix were investigated in detail for different values of governing parameters in order to examine the improved heat transfer characteristics of added nanoparticles. <![CDATA[ <p>Suspensions of nanoscale particles and fluids have been recently subject of intense research, since it was proved that they considerably improve heat transfer capabilities of the fluid which can be crucial in several technological processes. Several applications can be found in the field of porous media flow, such as oil recovery systems, thermal and geothermal energy, nuclear reactors cooling. Since nanofluids are a mixture of a solid and fluid phase, in general, the two phase mathematical model would be the most appropriate to use. However, due to very small size of nanoparticles (1–100 nm) can be assumed, that they behave as a water molecule and a single phase model along with empirical correlations for nanofluid properties can be used. In the present study a convective flow through porous cavity fully saturated with nanofluid is analyzed in detail using the single phase mathematical model based on the Navier-Stokes equations taking into account the non-Darcy parameters. The mathematical model is written at a macroscopic level enabling the simulation of the porous media flow. The solutions are obtained with the in house numerical code based on the Boundary Element Method, which was already proved to have some unique advantages when considering fluid flow problems in different configurations. The effects of the presence of different types of nanoparticles as well as the porous matrix were investigated in detail for different values of governing parameters in order to examine the improved heat transfer characteristics of added nanoparticles.</p> ]]> Numerical Simulation of Convective Flow in a Non-Darcy Porous Cavity Filled with Nanofluid j. k. stajnko r. jecl j. ravnik doi: 10.2495/CMEM-V4-N4-454-463 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 454 10.2495/CMEM-V4-N4-454-463 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-454-463 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-444-453 To model submarine flows of granular materials we propose an extension of the drift-flux approach. The extended model is able to represent dilute suspensions as well as dense granular flows. The dense granwular flow is modelled as a Herschel–Bulkley fluid, with a yield stress that depends on the dispersed phase pressure. Qualitative numerical experiments show that the model is able to correctly reproduce the stability of submerged sand heaps with different internal angles of friction and initial slopes. When initially starting with heaps with an angle smaller than the internal angle of friction, the heaps are stable. When starting with heaps with angles larger than the internal angle of friction, a flow of solid material is initiated. The flow later stops when the bed is at an angle smaller than the internal angle of friction. <![CDATA[ <p>To model submarine flows of granular materials we propose an extension of the drift-flux approach. The extended model is able to represent dilute suspensions as well as dense granular flows. The dense granwular flow is modelled as a Herschel–Bulkley fluid, with a yield stress that depends on the dispersed phase pressure. Qualitative numerical experiments show that the model is able to correctly reproduce the stability of submerged sand heaps with different internal angles of friction and initial slopes. When initially starting with heaps with an angle smaller than the internal angle of friction, the heaps are stable. When starting with heaps with angles larger than the internal angle of friction, a flow of solid material is initiated. The flow later stops when the bed is at an angle smaller than the internal angle of friction.</p> ]]> An Extension of the Drift-Flux Model for Submarine Granular Flows dave weij geert h. keetels joep goere cees van rhee doi: 10.2495/CMEM-V4-N4-444-453 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 444 10.2495/CMEM-V4-N4-444-453 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-444-453 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-434-443 The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation is an attractive and economic solution to develop deep offshore fields producing fluid without hydrate or wax. Recently the subsea separation system is designed for a water depth of 3,000 m and internal design pressure up to 690 bar. Development and application of subsea separation system are relatively common in the developed countries and many studies have been conducted previously, but it is still a new field in Korea and this is the significance of this study. In this study, gas-liquid mixture flow characteristics inside in-line type subsea separation system are investigated by numerical and experimental studies for the development of subsea separator. For the subsea separator designed in this study, it is predicted to have a separating efficiency of 70%. <![CDATA[ <p>The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation is an attractive and economic solution to develop deep offshore fields producing fluid without hydrate or wax. Recently the subsea separation system is designed for a water depth of 3,000 m and internal design pressure up to 690 bar. Development and application of subsea separation system are relatively common in the developed countries and many studies have been conducted previously, but it is still a new field in Korea and this is the significance of this study. In this study, gas-liquid mixture flow characteristics inside in-line type subsea separation system are investigated by numerical and experimental studies for the development of subsea separator. For the subsea separator designed in this study, it is predicted to have a separating efficiency of 70%.</p> ]]> A Study on the Gas–Liquid Mixture Flow Characteristics Inside in-Line Type Subsea Separator y. j. kim n. s. woo s. m. han doi: 10.2495/CMEM-V4-N4-434-443 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 434 10.2495/CMEM-V4-N4-434-443 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-434-443 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-424-433 The use of compressed natural gas (CNG) as a fuel in internal combustion engines brings significant advantages in terms of reduction of CO2-emissions and fuel consumption. Compared to standard gasoline combustion, the CO2-production can be clearly reduced by using a methane-based fuel as it has a beneficial H/C ratio. The high knock resistance of methane allows higher compression ratios so that the thermodynamic efficiency is enhanced. Furthermore, the realization of a stratified mixture formation concept shows great potential to further increase fuel savings due to the reduced throttling losses.In the present work, an URANS-based simulation strategy using the commercial code AVL Fire for the direct injection (DI) of CNG and the mixture formation, including a discretisation of the full nozzle and cylinder geometry is presented. High pressure ratios between the injector and the cylinder lead to a choked flow inside the nozzle. A supersonic region, including shock-occurrence follows as the jet is expanded further downstream the orifice. To successfully resolve the multi-scale flow phenomena the mesh generation process involves the design of a fine hexahedral mesh for the injector, which is merged to the moving cylinder mesh by an arbitrary interface. Turbulence is modelled using the k-ζ-f model. To estimate the grid-induced error of the simulation, a set of calculations was performed on meshes of decreasing cell dimension. Different nozzle geometries are investigated and evaluated with regard to their mixture formation suitability as well as the effect of increasing rail pressure. Variations include an inward opening multi-hole injector and an outward opening annular ring injector. The results show a strong tendency of the gas jets to interact with each other and with the surrounding walls. <![CDATA[ <p>The use of compressed natural gas (CNG) as a fuel in internal combustion engines brings significant advantages in terms of reduction of CO₂-emissions and fuel consumption. Compared to standard gasoline combustion, the CO₂-production can be clearly reduced by using a methane-based fuel as it has a beneficial H/C ratio. The high knock resistance of methane allows higher compression ratios so that the thermodynamic efficiency is enhanced. Furthermore, the realization of a stratified mixture formation concept shows great potential to further increase fuel savings due to the reduced throttling losses.</p><p>In the present work, an URANS-based simulation strategy using the commercial code AVL Fire for the direct injection (DI) of CNG and the mixture formation, including a discretisation of the full nozzle and cylinder geometry is presented. High pressure ratios between the injector and the cylinder lead to a choked flow inside the nozzle. A supersonic region, including shock-occurrence follows as the jet is expanded further downstream the orifice. To successfully resolve the multi-scale flow phenomena the mesh generation process involves the design of a fine hexahedral mesh for the injector, which is merged to the moving cylinder mesh by an arbitrary interface. Turbulence is modelled using the k-ζ-f model. To estimate the grid-induced error of the simulation, a set of calculations was performed on meshes of decreasing cell dimension. Different nozzle geometries are investigated and evaluated with regard to their mixture formation suitability as well as the effect of increasing rail pressure. Variations include an inward opening multi-hole injector and an outward opening annular ring injector. The results show a strong tendency of the gas jets to interact with each other and with the surrounding walls.</p> ]]> A Novel CFD Approach for Modelling the High-Pressure Direct Injection and Mixture Formation in a Spark-Ignited CNG Engine a. twellmeyer f. köpple b. weigand doi: 10.2495/CMEM-V4-N4-424-433 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 424 10.2495/CMEM-V4-N4-424-433 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-424-433 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-413-423 This paper presents a newly developed overlapping domain decomposition (ODD) method, which forms the basis of a near-far field coupling solver for a wide range of wave-structure interaction problem. In this method, the computational domain is decomposed into near- and far-fields which are then modeled separately by solving the viscous Navier-Stokes equation (NSE) and the Potential Laplacian equation (PLE), respectively. The free-surface problem is solved in both domains but using totally different strategies: a moving mesh-free surface tracking method is adopted in the potential domain; and the volume of fluid (VOF) method is used to track the free surface in the viscous domain. The novelty of the reported method lies in two-folds. First, similar to the relaxation zone technique, the introduction of the overlapped buffer zone eliminates the need of performing time time-consuming iterative schemes in the non-ODD methods to ensure the matching of free-surface elevation at the domain boundaries. Second, an in-house developed OVERSET method is adopted for the viscous domain solver to handle large object displacement in the case of extreme event. Finite volume method (FVM) is adopted to discretize both the NS and PL equations. The proposed method has been implemented in the OpenFOAM platform. To validate the method, is firstly employed to simulate a solitary wave and the resulting wave parameters are compared to the analytical solution, which suggests the accuracy and efficiency of the proposed method. <![CDATA[ <p>This paper presents a newly developed overlapping domain decomposition (ODD) method, which forms the basis of a near-far field coupling solver for a wide range of wave-structure interaction problem. In this method, the computational domain is decomposed into near- and far-fields which are then modeled separately by solving the viscous Navier-Stokes equation (NSE) and the Potential Laplacian equation (PLE), respectively. The free-surface problem is solved in both domains but using totally different strategies: a moving mesh-free surface tracking method is adopted in the potential domain; and the volume of fluid (VOF) method is used to track the free surface in the viscous domain. The novelty of the reported method lies in two-folds. First, similar to the relaxation zone technique, the introduction of the overlapped buffer zone eliminates the need of performing time time-consuming iterative schemes in the non-ODD methods to ensure the matching of free-surface elevation at the domain boundaries. Second, an in-house developed OVERSET method is adopted for the viscous domain solver to handle large object displacement in the case of extreme event. Finite volume method (FVM) is adopted to discretize both the NS and PL equations. The proposed method has been implemented in the OpenFOAM platform. To validate the method, is firstly employed to simulate a solitary wave and the resulting wave parameters are compared to the analytical solution, which suggests the accuracy and efficiency of the proposed method.</p> ]]> Coupling of Viscous and Potential Flow Models with Free Surface: Implementation and Application to Offshore Engineering xin lu yu chen dominic denver john chandar jing lou doi: 10.2495/CMEM-V4-N4-413-423 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 413 10.2495/CMEM-V4-N4-413-423 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-413-423 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-403-412 Among basic problems associated with additive manufacturing of metal objects by accretion of moltenmetal droplets is a number of questions of fluid-mechanical character. Authors concentrate attention on two alternative designs of droplets generation: one using centrifugal force and the other with liquid surface deformed electrostatically into a cone producing the droplets at its tip. <![CDATA[ <p>Among basic problems associated with additive manufacturing of metal objects by accretion of moltenmetal droplets is a number of questions of fluid-mechanical character. Authors concentrate attention on two alternative designs of droplets generation: one using centrifugal force and the other with liquid surface deformed electrostatically into a cone producing the droplets at its tip.</p> ]]> Fluid Mechanics of Molten Metal Droplets in Additive Manufacturing v. tesař j. šonský doi: 10.2495/CMEM-V4-N4-403-412 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 403 10.2495/CMEM-V4-N4-403-412 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-403-412 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-393-402 A high speed camera investigation is presented into the behavior of CO2 dry-ice particles in an application of dry-ice blasting to the defouling of commercial aircraft engine compressors. An image acquisition system is deployed in the compressor section of an aircraft engine and is used to determine the evolution of dry-ice particle size and velocity from the nozzle exit to the entrance to the engine’s high pressure compressor as the engine is cranked. A comparison study between CO2 dry-ice particle laden flows and airflows with single Polyoxymethylene (POM) particles of various diameters is also presented. Measurements are made using a range of blasting system pressures and using sonic and supersonic blasting nozzles. The behavior of large CO2 dry-ice particles (dP ≥ 1 mm) in this discontinuously and inhomogenously laden flow is compared to that of single POM particles under similar flow conditions and is found to behave similarly. The experiments presented turn out to be useful for supporting development of special purpose dry-ice blasting systems. <![CDATA[ <p>A high speed camera investigation is presented into the behavior of <em>CO₂</em> dry-ice particles in an application of dry-ice blasting to the defouling of commercial aircraft engine compressors. An image acquisition system is deployed in the compressor section of an aircraft engine and is used to determine the evolution of dry-ice particle size and velocity from the nozzle exit to the entrance to the engine’s high pressure compressor as the engine is cranked. A comparison study between <em>CO₂</em> dry-ice particle laden flows and airflows with single Polyoxymethylene (POM) particles of various diameters is also presented. Measurements are made using a range of blasting system pressures and using sonic and supersonic blasting nozzles. The behavior of large <em>CO₂</em> dry-ice particles (dP ≥ 1 mm) in this discontinuously and inhomogenously laden flow is compared to that of single POM particles under similar flow conditions and is found to behave similarly. The experiments presented turn out to be useful for supporting development of special purpose dry-ice blasting systems.</p> ]]> Particle Laden Flow Investigations in Special Purpose Dry-Ice Blasting Applications a. rudek g. russ b. duignan doi: 10.2495/CMEM-V4-N4-393-402 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 393 10.2495/CMEM-V4-N4-393-402 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-393-402 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-380-392 The magnetoplasmadynamic (MPD) arcjet is a promising thruster which is developed for exploration missions to the moon and Mars, and for raising orbits of large space structures. The MPD arcjet utilizes mainly electromagnetic force, i.e Lorentz force J × B, which is generated in this work by interaction between the current density and a coaxial magnetic field azimuthally induced by the total discharge current. In the present notes, we describe the implementation of a density–pressure-based method for the simulation of the magnetohydrodynamic (MHD) equations under a finite volume formulation. This new algorithm was developed for both ideal and resistive MHD equations and make use of the central-upwind schemes of Kurganov and Tadmor for flux calculation. As we assume that the plasma flow is a continuum fluid, electrical conductivity is predicted according to the Spitzer-Harm formulation. With the developed model, a limited set of computer runs was performed to assess the effect of geometric scale changes on an Argon self-field MPD thrusters performance. The results are reported and discussed. <![CDATA[ <p>The magnetoplasmadynamic (MPD) arcjet is a promising thruster which is developed for exploration missions to the moon and Mars, and for raising orbits of large space structures. The MPD arcjet utilizes mainly electromagnetic force, i.e Lorentz force <em>J</em> × <em>B</em>, which is generated in this work by interaction between the current density and a coaxial magnetic field azimuthally induced by the total discharge current. In the present notes, we describe the implementation of a density–pressure-based method for the simulation of the magnetohydrodynamic (MHD) equations under a finite volume formulation. This new algorithm was developed for both ideal and resistive MHD equations and make use of the central-upwind schemes of Kurganov and Tadmor for flux calculation. As we assume that the plasma flow is a continuum fluid, electrical conductivity is predicted according to the Spitzer-Harm formulation. With the developed model, a limited set of computer runs was performed to assess the effect of geometric scale changes on an Argon self-field MPD thrusters performance. The results are reported and discussed.</p> ]]> A Markov Chain Approach to Model Reconstruction chelem c r. groll doi: 10.2495/CMEM-V4-N4-380-392 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 380 10.2495/CMEM-V4-N4-380-392 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-380-392 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-369-379 The following remarks outline the structure of the Newtonian Mach’s principle and its implications for fluid motion and turbulence. This principle can only be understood as part of classical thermomechanics on a global scale and is directly related to both the first axiom of Newtonian mechanics and to global total energy covariance. <![CDATA[ <p>The following remarks outline the structure of the Newtonian Mach’s principle and its implications for fluid motion and turbulence. This principle can only be understood as part of classical thermomechanics on a global scale and is directly related to both the first axiom of Newtonian mechanics and to global total energy covariance.</p> ]]> Mach’s Principle Is Equivalent to Newton’s First Axiom (a Survey) t. h. moulden doi: 10.2495/CMEM-V4-N4-369-379 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 369 10.2495/CMEM-V4-N4-369-379 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-369-379 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-0 <![CDATA[ ]]> Preface carlos a. brebbia doi: 10.2495/CMEM-V4-N4-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 4 Article 0 10.2495/CMEM-V4-N4-0 https://www.acadlore.com/article/IJCMEM/2016_4_4/CMEM-V4-N4-0 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-iii This special issue of the International Journal of Computational Methods and Experimental Measurements contains a selected number of edited papers presented at the Conference on Structures under Shock and Impact held in Crete in 2016.The papers cover a variety of topics, including impact and blast loading, response of buildings and other structures to large dynamic loads and their material behaviour at high rates of strain. These are all areas of active research and special interest, focused on the survivability of physical facilities and the protection of people.The issue comprises a series of research contributions, essential to deepen the knowledge of how structures and materials behave under a wide variety of dynamic load actions. The contributors are from different centres throughout the world in which advanced impact and blast studies are carried out.This issue is of primary importance to scientists and engineers working in a variety of academic disciplines and industrial organisations who need to be aware of the latest developments in the impact response of materials and structures and the vulnerability of our infrastructure and environment to accidental explosions and terrorist attacks. <![CDATA[ <p>This special issue of the International Journal of Computational Methods and Experimental Measurements contains a selected number of edited papers presented at the Conference on Structures under Shock and Impact held in Crete in 2016.</p><p style="text-align: justify">The papers cover a variety of topics, including impact and blast loading, response of buildings and other structures to large dynamic loads and their material behaviour at high rates of strain. These are all areas of active research and special interest, focused on the survivability of physical facilities and the protection of people.</p><p style="text-align: justify">The issue comprises a series of research contributions, essential to deepen the knowledge of how structures and materials behave under a wide variety of dynamic load actions. The contributors are from different centres throughout the world in which advanced impact and blast studies are carried out.</p><p style="text-align: justify">This issue is of primary importance to scientists and engineers working in a variety of academic disciplines and industrial organisations who need to be aware of the latest developments in the impact response of materials and structures and the vulnerability of our infrastructure and environment to accidental explosions and terrorist attacks.</p> ]]> Preface doi: 10.2495/CMEM-V4-N3-iii International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 0 10.2495/CMEM-V4-N3-iii https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-iii https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-353-363 The preferred procedure for steel guardrails in the state of Georgia, USA for vehicle impact employs a post-installation machine to drive the posts through a layer of asphalt placed to retard vegetation growth around the system. However, in order to avoid undesirable restraint at the ground line, the AASHTO Roadside Design Guide recommends incorporating leave-outs. Using a leave-out in vegetation barriers is seen as less desirable because of issues including significantly higher expected costs, variability in the placement and spacing of posts, and the need for variable construction scheduling. In lieu of leave- outs, predetermined fracture planes, or “pre-cuts” were installed in the asphalt and evaluated in terms of ground restraint. An experimental program was carried out on an outdoor test site. Posts were installed in pre-cut asphalt and subjected to static loading to provide a better understanding of the behavior of a post restrained with an asphalt layer at the ground line. In parallel with the experimental program, a three dimensional finite element model was developed for a guardrail post installed through an asphalt layer. The model was refined using the experimental results from the test program as well as material testing. Results from the experimental program and finite element analyses indicate that certain pre-cutting configurations lead to significantly less ground restraint as desired. <![CDATA[ <p>The preferred procedure for steel guardrails in the state of Georgia, USA for vehicle impact employs a post-installation machine to drive the posts through a layer of asphalt placed to retard vegetation growth around the system. However, in order to avoid undesirable restraint at the ground line, the AASHTO Roadside Design Guide recommends incorporating leave-outs. Using a leave-out in vegetation barriers is seen as less desirable because of issues including significantly higher expected costs, variability in the placement and spacing of posts, and the need for variable construction scheduling. In lieu of leave- outs, predetermined fracture planes, or “pre-cuts” were installed in the asphalt and evaluated in terms of ground restraint. An experimental program was carried out on an outdoor test site. Posts were installed in pre-cut asphalt and subjected to static loading to provide a better understanding of the behavior of a post restrained with an asphalt layer at the ground line. In parallel with the experimental program, a three dimensional finite element model was developed for a guardrail post installed through an asphalt layer. The model was refined using the experimental results from the test program as well as material testing. Results from the experimental program and finite element analyses indicate that certain pre-cutting configurations lead to significantly less ground restraint as desired.</p> ]]> Effect of Pre-Cut Asphalt Fracture Planes on Highway Guardrail Performance s. h. lee e. bakhtiary l. k. stewart d. scott d. white doi: 10.2495/CMEM-V4-N3-353-363 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 353 10.2495/CMEM-V4-N3-353-363 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-353-363 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-345-352 There are some difficulties of non-destructive test and evaluation for immersed or submerged structures such as nuclear reactor pipe line, submarine or huge ship. This paper proposes the method of damage detection of immersed metallic structure which has crack on weld zone and placed in the water with slight and random surface oscillation using ultrasonic wave propagation imaging (UWPI) system with piezoelectric transducer. A T-shape metallic structure with artificial surface crack on weld zone, which with size 2 mm by 0.3 mm and the depth 2 mm, used as the specimen. A 532 nm Q-switched continuous wave laser is used for scanning an area of 20 mm by 40 mm. A piezoelectric sensor with magnetic sensor head, which is attachable to metallic structure is used as a contact ultrasonic sensor. The tests are performed in three cases: a specimen without water, a specimen immersed in water and a specimen immersed in water with random surface oscillation. Ultrasonic wave propagation image algorithm and adjacent wave subtraction (AWS) algorithm are used for visualizing wave propagation and detecting the crack. For the case where the specimen is immersed in the water, the signal amplitude is increased compared with the specimen without water case. In AWS algorithm results of the immersed case, scattering waves which are generated by cracks were observed. In random surface oscillation case, the excitation laser beam is refracted randomly by Snell’s law resulting in the diluted wave propagation images. However, improvements in signal-to-noise ratio using repeat scan technology enable to the detection of the crack and estimation of the crack size.This paper examines the damage detection using ultrasonic wave propagation caused by laser excitation from outside of the water even when the water surface oscillation exists and implies the possibility of application of ultrasonic propagation imaging system to submerged structures. <![CDATA[ <p>There are some difficulties of non-destructive test and evaluation for immersed or submerged structures such as nuclear reactor pipe line, submarine or huge ship. This paper proposes the method of damage detection of immersed metallic structure which has crack on weld zone and placed in the water with slight and random surface oscillation using ultrasonic wave propagation imaging (UWPI) system with piezoelectric transducer. A T-shape metallic structure with artificial surface crack on weld zone, which with size 2 mm by 0.3 mm and the depth 2 mm, used as the specimen. A 532 nm Q-switched continuous wave laser is used for scanning an area of 20 mm by 40 mm. A piezoelectric sensor with magnetic sensor head, which is attachable to metallic structure is used as a contact ultrasonic sensor. The tests are performed in three cases: a specimen without water, a specimen immersed in water and a specimen immersed in water with random surface oscillation. Ultrasonic wave propagation image algorithm and adjacent wave subtraction (AWS) algorithm are used for visualizing wave propagation and detecting the crack. For the case where the specimen is immersed in the water, the signal amplitude is increased compared with the specimen without water case. In AWS algorithm results of the immersed case, scattering waves which are generated by cracks were observed. In random surface oscillation case, the excitation laser beam is refracted randomly by Snell’s law resulting in the diluted wave propagation images. However, improvements in signal-to-noise ratio using repeat scan technology enable to the detection of the crack and estimation of the crack size.</p><p style="text-align: justify">This paper examines the damage detection using ultrasonic wave propagation caused by laser excitation from outside of the water even when the water surface oscillation exists and implies the possibility of application of ultrasonic propagation imaging system to submerged structures.</p> ]]> Crack Detection of Immersed Metallic Structure in Water with Surface Oscillation using Scanning Laser Pulse j.y. park j.r. lee b.y. koo doi: 10.2495/CMEM-V4-N3-345-352 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 345 10.2495/CMEM-V4-N3-345-352 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-345-352 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-336-344 Sandwich panels are commonly used for aerospace structures that require a high-bending stiffness, but the thin facesheets that are bonded to the core can be susceptible to impact damage. It is necessary to be able to identify and assess the severity of the damage, but this can be difficult when dents are not visible on the surface of the skin. This can occur when the dent elastically springs back immediately after impact, and can cause the skin to return close to its original position, leaving little indication that a damaged core exists. Identifying combinations of skin thickness and core density that are more susceptible to spring back can enable better decisions to be made with respect to inspection procedures. Finite element simulations of metal-skinned honeycomb panels indicate that more spring back is expected to occur from panels composed of thicker skins and lower density core. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Sandwich panels are commonly used for aerospace structures that require a high-bending stiffness, but the thin facesheets that are bonded to the core can be susceptible to impact damage. It is necessary to be able to identify and assess the severity of the damage, but this can be difficult when dents are not visible on the surface of the skin. This can occur when the dent elastically springs back immediately after impact, and can cause the skin to return close to its original position, leaving little indication that a damaged core exists. Identifying combinations of skin thickness and core density that are more susceptible to spring back can enable better decisions to be made with respect to inspection procedures. Finite element simulations of metal-skinned honeycomb panels indicate that more spring back is expected to occur from panels composed of thicker skins and lower density core.</span></p> ]]> Effects of Skin Thickness and Core Density on the Residual Dent Depth in Aerospace Sandwich Panels d. wowk c. marsden doi: 10.2495/CMEM-V4-N3-336-344 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 336 10.2495/CMEM-V4-N3-336-344 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-336-344 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-321-335 This work is an experimental study of the dynamic fields of a turbulent premixed methane-air flame in a Bunsen burner. The Particle Image Velocimetry (PIV) is used to determine the dynamic fields, and Laser Sheet Tomography (LST) for the flame fronts. The turbulent main jet has a Reynolds number Re = 10 000. Turbulence is generated using perforated grids having three whose provide different inlet turbulence intensities. Velocity fields are measured for various equivalence ratio (F = 0.6–1.3) and different axial flame positions. For the reactive jet, interesting results are obtained concerning the dynamic field and the flame front. It is shown that radial profiles of U and V correspond to the axial positions located before the end of the potential core in the reactive jet. The velocity increases at the jet center to 20 m/s, and is less influenced by turbulent mixing in the flame. The greatest velocity and turbulent kinetic energy are obtained using the grid with the smallest ratio (d/M). Most important values of the radial velocity correspond to the lean flames. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This work is an experimental study of the dynamic fields of a turbulent premixed methane-air flame in a Bunsen burner. The Particle Image Velocimetry (PIV) is used to determine the dynamic fields, and Laser Sheet Tomography (LST) for the flame fronts. The turbulent main jet has a Reynolds number Re = 10 000. Turbulence is generated using perforated grids having three whose provide different inlet turbulence intensities. Velocity fields are measured for various equivalence ratio (F = 0.6–1.3) and different axial flame positions. For the reactive jet, interesting results are obtained concerning the dynamic field and the flame front. It is shown that radial profiles of U and V correspond to the axial positions located before the end of the potential core in the reactive jet. The velocity increases at the jet center to 20 m/s, and is less influenced by turbulent mixing in the flame. The greatest velocity and turbulent kinetic energy are obtained using the grid with the smallest ratio (d/M). Most important values of the radial velocity correspond to the lean flames.</span></p> ]]> Experimental Study of the Dynamic Field of Turbulent Premixed Methane/Air Flame using PIV Technique m.s. boulahlib m. chekired m. benzitouni s. boukebbab doi: 10.2495/CMEM-V4-N3-321-335 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 321 10.2495/CMEM-V4-N3-321-335 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-321-335 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-311-320 Laminar pipe flow is becoming an important experimental test case for new high efficiency heat carriers like nano- and ferrofluids. Here, a new scaling approach for mixed convection in laminar pipe flow with constant heat flux is proposed. The model relates the radial temperature gradient at the wall, represented as the local Nusselt number, with local Reynolds, Prandtl, and Grashof numbers. The proposed scaling approach is successfully employed to collapse data from different test rigs with horizontally oriented pipes and operated with water. Influences of differing strengths following from free convection are gathered with the new scaling. Moreover, the new scaling approach is successfully utilised to value experimentally obtained heat transfer data of nanofluid flow. In this regard, the impact of nanoparticles, namely the suppression of heat transfer in mixed convection, is experimentally shown and theoretically analysed. Finally, the influence of pipe orientation (vertical / horizontal) is discussed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Laminar pipe flow is becoming an important experimental test case for new high efficiency heat carriers like nano- and ferrofluids. Here, a new scaling approach for mixed convection in laminar pipe flow with constant heat flux is proposed. The model relates the radial temperature gradient at the wall, represented as the local Nusselt number, with local Reynolds, Prandtl, and Grashof numbers. The proposed scaling approach is successfully employed to collapse data from different test rigs with horizontally oriented pipes and operated with water. Influences of differing strengths following from free convection are gathered with the new scaling. Moreover, the new scaling approach is successfully utilised to value experimentally obtained heat transfer data of nanofluid flow. In this regard, the impact of nanoparticles, namely the suppression of heat transfer in mixed convection, is experimentally shown and theoretically analysed. Finally, the influence of pipe orientation (vertical / horizontal) is discussed.</span></p> ]]> Modelling Mixed Convection in Laminar Pipe Flow m.h. buschmann l. colla l. fedele doi: 10.2495/CMEM-V4-N3-311-320 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 311 10.2495/CMEM-V4-N3-311-320 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-311-320 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-301-310 To reduce the vulnerability of both civilian and military aircraft, it is important to take the hydrodynamic ram (HRAM) effect into account when designing their fuel tanks. HRAM is especially dangerous for liquid- filled thin walled lightweight structures that cannot be armoured due to weight penalty reasons. However, the response of the tank structure during HRAM events depends on a coupling model between fluid and structure. Water is generally used as a liquid candidate for experimental observations of HRAM, since it is a safe and affordable solution. However, its characteristics in thermal transfers are far different from the ones of hydrocarbons, and it may influence the bubble behaviour and thus its resulting loading on the tank walls. A good understanding of all these aspects is still needed to enhance the tank designs. Similarities in bubble behaviour between HRAM and underwater explosion situations were observed in recent high-speed tank penetration/water entry experiments. A confined version of the Rayleigh-Plesset equation – which is classically used for bubble dynamics analysis (including underwater explosion) – has been previously proposed to simulate a bubble created by an HRAM event. The work the presented work is a first attempt to the estimation of the influence of thermal effects in HRAM processes, by using the Rayleigh-Plesset equation in confined regime. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">To reduce the vulnerability of both civilian and military aircraft, it is important to take the hydrodynamic ram (HRAM) effect into account when designing their fuel tanks. HRAM is especially dangerous for liquid- filled thin walled lightweight structures that cannot be armoured due to weight penalty reasons. However, the response of the tank structure during HRAM events depends on a coupling model between fluid and structure. Water is generally used as a liquid candidate for experimental observations of HRAM, since it is a safe and affordable solution. However, its characteristics in thermal transfers are far different from the ones of hydrocarbons, and it may influence the bubble behaviour and thus its resulting loading on the tank walls. A good understanding of all these aspects is still needed to enhance the tank designs. Similarities in bubble behaviour between HRAM and underwater explosion situations were observed in recent high-speed tank penetration/water entry experiments. A confined version of the Rayleigh-Plesset equation – which is classically used for bubble dynamics analysis (including underwater explosion) – has been previously proposed to simulate a bubble created by an HRAM event. The work the presented work is a first attempt to the estimation of the influence of thermal effects in HRAM processes, by using the Rayleigh-Plesset equation in confined regime.</span></p> ]]> Prediction of Thermal Effects of Magnitude for HRAM Event in Fuel-Filled Tank using the Rayleigh-Plesset Equation t. fourest m. arrigoni e. deletombe j. dupas j-m. laurens doi: 10.2495/CMEM-V4-N3-301-310 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 301 10.2495/CMEM-V4-N3-301-310 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-301-310 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-288-300 The integrity of reactor pressure vessels (RPVs) of nuclear power plants is one of the most important topics in the field of nuclear energy production. Therefore, the integrity of RPVs has to be assessed for normal operation as well as for emergency transients. A critical transient concerning the RPV integrity is the emergency cooling of a pressurized water reactor, initiated by a leak in the hot leg. Such shock-like cooling in combination with the pressure, the so-called pressurized thermal shock (PTS), causes high thermal stresses in the RPV wall and stress intensities of pre-existing cracks which could exceed the remaining fracture toughness of the material, which is additionally embrittled due to neutron irradiation. This may result in a cleavage fracture of the most safety relevant reactor component.We present a PTS study of a reference reactor, starting with the calculation of the thermal-hydraulic system behaviour, followed by the simulation of the cold water temperature injection and mixing by means of computational fluid dynamics (CFD) method and the subsequent structural and fracture mechanics calculation. In the safety assessment, we compare the evolution of the stress intensity factors (SIF) during an emergency cooling transient with the fracture toughness at the tip of postulated cracks. Results and open questions will be discussed in the light of a realistic estimation of safety margins. <![CDATA[ <p>The integrity of reactor pressure vessels (RPVs) of nuclear power plants is one of the most important topics in the field of nuclear energy production. Therefore, the integrity of RPVs has to be assessed for normal operation as well as for emergency transients. A critical transient concerning the RPV integrity is the emergency cooling of a pressurized water reactor, initiated by a leak in the hot leg. Such shock-like cooling in combination with the pressure, the so-called pressurized thermal shock (PTS), causes high thermal stresses in the RPV wall and stress intensities of pre-existing cracks which could exceed the remaining fracture toughness of the material, which is additionally embrittled due to neutron irradiation. This may result in a cleavage fracture of the most safety relevant reactor component.</p><p style="text-align: justify">We present a PTS study of a reference reactor, starting with the calculation of the thermal-hydraulic system behaviour, followed by the simulation of the cold water temperature injection and mixing by means of computational fluid dynamics (CFD) method and the subsequent structural and fracture mechanics calculation. In the safety assessment, we compare the evolution of the stress intensity factors (SIF) during an emergency cooling transient with the fracture toughness at the tip of postulated cracks. Results and open questions will be discussed in the light of a realistic estimation of safety margins.</p> ]]> Analysis of a Reactor Pressure Vessel Subjected to Pressurized Thermal Shocks m. niffenegger g. qian v.f. gonzalez-albuixech m. sharabi n. lafferty doi: 10.2495/CMEM-V4-N3-288-300 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 288 10.2495/CMEM-V4-N3-288-300 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-288-300 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-280-287 Recent studies with numerical models regarding edge protection systems (EPS), class C according to standard EN 13374, showed that some requirements are inadequate for human safety. This problem mainly arises when a person is injured by falling directly against the EPS supports.To analyse this subject, three series of numerical models, in accordance with EN 13374, have been produced. The paper describes these studies, which have been carried out using straight supports, different weight ballasts and also a deformable ballast.In the first series, impacts against straight supports have been analyzed and a standard EN 13374 ballast has been used. These first studies showed too many high impact factors on the ballast. The obtained values are absolutely inadequate and dangerous to the integrity of the human body. The second series was conducted to know how different weights and shapes of ballast affect the maximum accelerations suffered by the human body. Finally, in the third series, a more deformable ballast has been used to simulate impacts of workers against straight supports, nearest to the real behaviour of a human body.Results confirm and measure an excessive impact factor suffered by the falling person. Mainly in the first series, with direct impacts of standard ballast against straight supports, acceleration values have been generated that could seriously injure the body or even could kill workers.The second series showed that different weights and shapes – cylinder or sphere – of ballast affect the acceleration values calculated.Finally, in the third series, the deformable ballast has achieved results truer than previous studies with the more rigid ballast established by EN 13374. <![CDATA[ <p>Recent studies with numerical models regarding edge protection systems (EPS), class C according to standard EN 13374, showed that some requirements are inadequate for human safety. This problem mainly arises when a person is injured by falling directly against the EPS supports.</p><p style="text-align: justify">To analyse this subject, three series of numerical models, in accordance with EN 13374, have been produced. The paper describes these studies, which have been carried out using straight supports, different weight ballasts and also a deformable ballast.</p><p style="text-align: justify">In the first series, impacts against straight supports have been analyzed and a standard EN 13374 ballast has been used. These first studies showed too many high impact factors on the ballast. The obtained values are absolutely inadequate and dangerous to the integrity of the human body. The second series was conducted to know how different weights and shapes of ballast affect the maximum accelerations suffered by the human body. Finally, in the third series, a more deformable ballast has been used to simulate impacts of workers against straight supports, nearest to the real behaviour of a human body.</p><p style="text-align: justify">Results confirm and measure an excessive impact factor suffered by the falling person. Mainly in the first series, with direct impacts of standard ballast against straight supports, acceleration values have been generated that could seriously injure the body or even could kill workers.</p><p style="text-align: justify">The second series showed that different weights and shapes – cylinder or sphere – of ballast affect the acceleration values calculated.</p><p style="text-align: justify">Finally, in the third series, the deformable ballast has achieved results truer than previous studies with the more rigid ballast established by EN 13374.</p> ]]> Previous Numerical Studies with Deformable Ballast on Body Impacts Against Building Edge Protection Systems j.c. pomares r. irles e. carrion a. gonzález e.g. segovia doi: 10.2495/CMEM-V4-N3-280-287 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 280 10.2495/CMEM-V4-N3-280-287 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-280-287 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-269-279 Precast concrete components are manufactured in a well-controlled environment. It has been proven to show good behaviour under gravity and lateral loads. However, the beam to column connections remain the critical part in the precast concrete structures under the column loss scenario in a progressive collapse scenario. In this paper, different beam to column connections, wet and dry connections, are studied and investigated numerically under the column removal scenario. A detailed model for the different connections is developed using the Applied Element Method (AEM). Different column removal locations are considered in the study to provide a comprehensive assessment. The performance of the connections is studied in terms of ultimate load capacity and rotational ductility. According to the results obtained, a connection enhancement is suggested to increase the resistance of precast concrete structures to progressive collapse. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Precast concrete components are manufactured in a well-controlled environment. It has been proven to show good behaviour under gravity and lateral loads. However, the beam to column connections remain the critical part in the precast concrete structures under the column loss scenario in a progressive collapse scenario. In this paper, different beam to column connections, wet and dry connections, are studied and investigated numerically under the column removal scenario. A detailed model for the different connections is developed using the Applied Element Method (AEM). Different column removal locations are considered in the study to provide a comprehensive assessment. The performance of the connections is studied in terms of ultimate load capacity and rotational ductility. According to the results obtained, a connection enhancement is suggested to increase the resistance of precast concrete structures to progressive collapse.</span></p> ]]> Progressive Collapse Assessment of Precast Concrete Connections using the Applied Element Method (AEM) m. ehab h. salem m. abdel-mooty doi: 10.2495/CMEM-V4-N3-269-279 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 269 10.2495/CMEM-V4-N3-269-279 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-269-279 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-258-268 Advanced damage behaviour of reinforced concrete is modelled using a mixed modelling approach, in which concrete is represented through the spherical-type discrete element model, whereas steel reinforcement is modelled by using beam-type finite elements. An original steel-concrete bond model developed and calibrated on pull-out tests is used to ensure transfer of forces between steel and concrete. The proposed approach is applied to simulate soft and hard-type impacts on RC beams within a very complete modelling framework, thus allowing validating by comparison with experimental data the overall numerical approach developed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Advanced damage behaviour of reinforced concrete is modelled using a mixed modelling approach, in which concrete is represented through the spherical-type discrete element model, whereas steel reinforcement is modelled by using beam-type finite elements. An original steel-concrete bond model developed and calibrated on pull-out tests is used to ensure transfer of forces between steel and concrete. The proposed approach is applied to simulate soft and hard-type impacts on RC beams within a very complete modelling framework, thus allowing validating by comparison with experimental data the overall numerical approach developed.</span></p> ]]> Using a Mixed DEM/FEM Approach to Model Advanced Damage of Reinforced Concrete under Impact s. potapov a. masurel l. daudeville p. marin doi: /10.2495/CMEM-V4-N3-258-268 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 258 /10.2495/CMEM-V4-N3-258-268 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-258-268 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-247-257 A blast retrofit technique for concrete structures using carbon fiber-reinforced polymer (CFRP) layers was investigated for use in large infrastructure systems with the overarching goal of preventing against major loss of life and considerable damage that would require extensive repair. Large-scale experiments were conducted and the retrofit behavior was investigated for application on relatively large reinforced concrete walls subjected to blast-like loadings. The experimental program utilized the University of California San Diego (UCSD) Blast Simulator. The Blast Simulator is able to induce various blast-like shock waves to the test specimen in a controlled laboratory environment. The performance of this blast retrofit was tested and then analyzed using SDOF and finite element modeling methods. A finite element model was created using LS-DYNA and utilized contact algorithms for the CFRP-concrete interface. Results and comparisons between the two analysis methods are given. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A blast retrofit technique for concrete structures using carbon fiber-reinforced polymer (CFRP) layers was investigated for use in large infrastructure systems with the overarching goal of preventing against major loss of life and considerable damage that would require extensive repair. Large-scale experiments were conducted and the retrofit behavior was investigated for application on relatively large reinforced concrete walls subjected to blast-like loadings. The experimental program utilized the University of California San Diego (UCSD) Blast Simulator. The Blast Simulator is able to induce various blast-like shock waves to the test specimen in a controlled laboratory environment. The performance of this blast retrofit was tested and then analyzed using SDOF and finite element modeling methods. A finite element model was created using LS-DYNA and utilized contact algorithms for the CFRP-concrete interface. Results and comparisons between the two analysis methods are given.</span></p> ]]> Analysis Methods for CFRP Blast Retrofitted Reinforced Concrete Wall Systems g.l. pezzola l.k. stewart g. hegemier doi: 10.2495/CMEM-V4-N3-247-257 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 247 10.2495/CMEM-V4-N3-247-257 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-247-257 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-231-246 With continuous advancements in computational capacity, it has become possible and feasible to numerically model very complex physical phenomena, for instance, high dynamic loads. Hydrocodes or, in other words, “wave propagation codes” were conceived to model such scenarios. Several numerical discretisations are available in these programs, which require the problem at hand to be modelled in distinct ways and which yield different results. In the present contribution, three different numerical strategies are compared. These employ a coupling of the Euler and the Lagrange scheme, the Euler scheme by itself as well as the Smooth Particle Hydrodynamics (SPH) scheme. Their application in the hydrocode ANSYS Autodyn to a contact detonation scenario with a concrete target and with a breakthrough is described as an example of a high dynamic load. This scenario is of special interest since it is a possible threat to critical infrastructure. The numerical results are compared and contrasted; individual strengths and weaknesses of the three numerical modelling strategies are identified also by validating their numerical results with an experimental one. To the authors’ knowledge, such comparison has not yet been done for contact detonation. It is concluded that the SPH method is the preferred strategy to model the considered scenario. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">With continuous advancements in computational capacity, it has become possible and feasible to numerically model very complex physical phenomena, for instance, high dynamic loads. Hydrocodes or, in other words, “wave propagation codes” were conceived to model such scenarios. Several numerical discretisations are available in these programs, which require the problem at hand to be modelled in distinct ways and which yield different results. In the present contribution, three different numerical strategies are compared. These employ a coupling of the Euler and the Lagrange scheme, the Euler scheme by itself as well as the Smooth Particle Hydrodynamics (SPH) scheme. Their application in the hydrocode ANSYS Autodyn to a contact detonation scenario with a concrete target and with a breakthrough is described as an example of a high dynamic load. This scenario is of special interest since it is a possible threat to critical infrastructure. The numerical results are compared and contrasted; individual strengths and weaknesses of the three numerical modelling strategies are identified also by validating their numerical results with an experimental one. To the authors’ knowledge, such comparison has not yet been done for contact detonation. It is concluded that the SPH method is the preferred strategy to model the considered scenario.</span></p> ]]> A Comparison of Numerical Modelling Strategies in Contact Detonation Scenarios with Concrete Targets b. esteban n. gebbeken doi: 10.2495/CMEM-V4-N3-231-246 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 231 10.2495/CMEM-V4-N3-231-246 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-231-246 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-221-230 Understanding the bond behaviour between reinforcing steel and concrete under high-loading rates is becoming more and more important with increasing frequency of natural disasters, impact loadings and a threat of terrorism. This paper aims to obtain a better understanding of the material interactions between the steel rebar and the concrete in the bond zone under different loading rates. During the experimental program push-in tests were conducted under quasi-static and dynamic loading conditions. Both a servo-hydraulic machine as well as an instrumented drop tower were used during the investigation. Samples with short-bond zone in the middle of a cylindrical specimen were used and only a small reinforcement bar diameter (10 mm) was investigated. This approach was chosen to ensure constant bond stress distribution and that the failure occurs during the first pass of the stress wave through the bond zone. Throughout the experimental programme the loading rate was varied from 0.01 mm/s to 8.3 m/s. Bond stress–slip relationships in dependence on the bond stress rate are presented in this paper. The results indicate a bond stress dependence on the loading rate although the scattering of the results is quite high. The experimentally determined dynamic increase factor (DIF) for concrete-steel bond stress is around 1.5 which is a value comparable to other authors. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Understanding the bond behaviour between reinforcing steel and concrete under high-loading rates is becoming more and more important with increasing frequency of natural disasters, impact loadings and a threat of terrorism. This paper aims to obtain a better understanding of the material interactions between the steel rebar and the concrete in the bond zone under different loading rates. During the experimental program push-in tests were conducted under quasi-static and dynamic loading conditions. Both a servo-hydraulic machine as well as an instrumented drop tower were used during the investigation. Samples with short-bond zone in the middle of a cylindrical specimen were used and only a small reinforcement bar diameter (10 mm) was investigated. This approach was chosen to ensure constant bond stress distribution and that the failure occurs during the first pass of the stress wave through the bond zone. Throughout the experimental programme the loading rate was varied from 0.01 mm/s to 8.3 m/s. Bond stress–slip relationships in dependence on the bond stress rate are presented in this paper. The results indicate a bond stress dependence on the loading rate although the scattering of the results is quite high. The experimentally determined dynamic increase factor (DIF) for concrete-steel bond stress is around 1.5 which is a value comparable to other authors.</span></p> ]]> Bond Stress-Slip Behaviour of Concrete and Steel under High-Loading Rates p. máca doi: 10.2495/CMEM-V4-N3-221-230 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 221 10.2495/CMEM-V4-N3-221-230 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-221-230 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-213-220 The purpose of the paper is to investigate the influence of geometry of charges on the propagation of blast waves. Various shape charges (cylinder, sphere, irregular shape) were used in the field tests. The main type of explosive, homemade ANFO (Ammonium nitrate + fuel oil), was used as the most common used explosives in improvised explosive devices used in terrorist attacks. Characteristics of homemade and industrially made ANFO explosives are different. There were comparing charges of various types of industrially produced types of explosives and homemade explosive in the field tests. The blast wave propagation were investigated and compared. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The purpose of the paper is to investigate the influence of geometry of charges on the propagation of blast waves. Various shape charges (cylinder, sphere, irregular shape) were used in the field tests. The main type of explosive, homemade ANFO (Ammonium nitrate + fuel oil), was used as the most common used explosives in improvised explosive devices used in terrorist attacks. Characteristics of homemade and industrially made ANFO explosives are different. There were comparing charges of various types of industrially produced types of explosives and homemade explosive in the field tests. The blast wave propagation were investigated and compared.</span></p> ]]> Influence of Homemade Ammonium Nitrate and Fuel Oil Explosives Charge Shapes on Blast Wave Propagation l. figuli v. kavicky z. ligasová p. maňas doi: 10.2495/CMEM-V4-N3-213-220 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 213 10.2495/CMEM-V4-N3-213-220 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-213-220 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-201-212 Many terrorist attacks in the last decade around the world have exposed the vulnerability of citizens in public places. Public trash receptacles can be easily abused as well-covered places in which Improvised Explosive Devices (IED) can be simply left and then remotely activated. Therefore, blast resistance and possibility of blast loads redirection are very important characteristics of trash receptacles placed in crowded public areas. This paper presents the results of three different trash receptacles: non-blast resistant, blast resistant and blast resistant trash receptacle with blast load redirection. The results have shown that a considerable effect can be achieved by using blast resistant receptacles, thus reducing the possibility of deaths and injuries. A thickness optimization study was additionally performed, based on the size and geometry of the opening by using a finite element model. Based on the results of the study, some valuable recommendations for design of trash receptacles are also given. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Many terrorist attacks in the last decade around the world have exposed the vulnerability of citizens in public places. Public trash receptacles can be easily abused as well-covered places in which Improvised Explosive Devices (IED) can be simply left and then remotely activated. Therefore, blast resistance and possibility of blast loads redirection are very important characteristics of trash receptacles placed in crowded public areas. This paper presents the results of three different trash receptacles: non-blast resistant, blast resistant and blast resistant trash receptacle with blast load redirection. The results have shown that a considerable effect can be achieved by using blast resistant receptacles, thus reducing the possibility of deaths and injuries. A thickness optimization study was additionally performed, based on the size and geometry of the opening by using a finite element model. Based on the results of the study, some valuable recommendations for design of trash receptacles are also given.</span></p> ]]> Blast Resistant Trash Receptacles with Blast Loading Redirection–Comparative Analyses jovan trajkovski robert kunc jasenko perenda matevž fazarnic ivan prebil doi: 10.2495/CMEM-V4-N3-201-212 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 201 10.2495/CMEM-V4-N3-201-212 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-201-212 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-191-200 In a joint endeavor conducted for the US Department of State (DoS) Bureau of Diplomatic Security, K&C has developed curtain-wall technology for US government infrastructure overseas capable of withstanding the threats anticipated from large explosive events such as VBIEDs at close proximity. The analysis utilized high fidelity physics-based (HFPB) calculations based on a combination of com- putational fluid dynamics (CFD) and computational structural dynamics (CSD) modeling methods. Unlike many similar analysis and simulation efforts, this work was validated by a full-scale explosive test. This provided an opportunity to compare the calculation outputs with test data to determine the efficacy and accuracy of the calculation methods as well as providing indicators for further calibra- tion of the analysis model. This paper will provide description and commentary of the calculation approach as adopted to analyze the structure using both CFD and CSD methods, as well as planning and conduct of the test including positioning of instrumentation and the purpose and nature of data collec- tion. Comparison of the simulation and test data is accompanied by discussion of the most significant discrepancies and areas in which the calculations closely matched the observed calculation results. Finally, conclusions are presented regarding the efficacy of the calculational approach adopted and recommendations presented for future calculations, and testing of conventional structural systems that are to be subject to blast loading of this magnitude. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In a joint endeavor conducted for the US Department of State (DoS) Bureau of Diplomatic Security, K&C has developed curtain-wall technology for US government infrastructure overseas capable of withstanding the threats anticipated from large explosive events such as VBIEDs at close proximity. The analysis utilized high fidelity physics-based (HFPB) calculations based on a combination of com- putational fluid dynamics (CFD) and computational structural dynamics (CSD) modeling methods. Unlike many similar analysis and simulation efforts, this work was validated by a full-scale explosive test. This provided an opportunity to compare the calculation outputs with test data to determine the efficacy and accuracy of the calculation methods as well as providing indicators for further calibra- tion of the analysis model. This paper will provide description and commentary of the calculation approach as adopted to analyze the structure using both CFD and CSD methods, as well as planning and conduct of the test including positioning of instrumentation and the purpose and nature of data collec- tion. Comparison of the simulation and test data is accompanied by discussion of the most significant discrepancies and areas in which the calculations closely matched the observed calculation results. Finally, conclusions are presented regarding the efficacy of the calculational approach adopted and recommendations presented for future calculations, and testing of conventional structural systems that are to be subject to blast loading of this magnitude.</span></p> ]]> Design, Analysis, and Testing of a Blast- Resistant Building Façade t.r. brewer j.e. crawford k.b. morrill j. abraham doi: 10.2495/CMEM-V4-N3-191-200 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 3 Article 191 10.2495/CMEM-V4-N3-191-200 https://www.acadlore.com/article/IJCMEM/2016_4_3/CMEM-V4-N3-191-200 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-50-57 In past studies, some of the authors presented how the integration of different systems, for the prevention of fires or explosions due to impact or bullet damage, may significantly improve the safety of fuel tanks. Leakage, after bullet penetration or debris impact, can be significantly reduced by introducing polymeric materials with self-healing capabilities for the container’s walls, while an internal aluminium filler can reduce the sloshing and the danger of fuel ignition. In the present paper, an experimental evaluation of the proposed solution is presented. A ballistic test campaign on a fluid container was performed to investigate the interaction between an ethylene–methacrylic acid (EMAA)-based ionomeric wall (i.e. Dupont®Surlyn 8940) and an internal aluminium filler (i.e. Explosafe®). Results show that the presence of the fluid increases the self-healing capabilities, which are however slightly affected by the internal aluminium filler; the contribution in terms of sloshing reduction remains relevant. Moreover, additional configurations based on multilayer panels are presented. The authors studied the healing process of EMAA in a sandwich configuration made of one skin of ionomer and one skin of carbon fibre, sepa- rated by an aramidic honeycomb. The main objective of the honeycomb is to prevent the remarkable reduction of the healing capabilities observed when ionomer is directly coupled to aramidic fabric or composite panels. The new multilayer configurations have been tested at different impact conditions. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">In past studies, some of the authors presented how the integration of different systems, for the prevention of fires or explosions due to impact or bullet damage, may significantly improve the safety of fuel tanks. Leakage, after bullet penetration or debris impact, can be significantly reduced by introducing polymeric materials with self-healing capabilities for the container’s walls, while an internal aluminium filler can reduce the sloshing and the danger of fuel ignition. In the present paper, an experimental evaluation of the proposed solution is presented. A ballistic test campaign on a fluid container was performed to investigate the interaction between an ethylene–methacrylic acid (EMAA)-based ionomeric wall (i.e. Dupont</span>^®<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Surlyn 8940) and an internal aluminium filler (i.e. Explosafe</span>^®<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">). Results show that the presence of the fluid increases the self-healing capabilities, which are however slightly affected by the internal aluminium filler; the contribution in terms of sloshing reduction remains relevant. Moreover, additional configurations based on multilayer panels are presented. The authors studied the healing process of EMAA in a sandwich configuration made of one skin of ionomer and one skin of carbon fibre, sepa- rated by an aramidic honeycomb. The main objective of the honeycomb is to prevent the remarkable reduction of the healing capabilities observed when ionomer is directly coupled to aramidic fabric or composite panels. The new multilayer configurations have been tested at different impact conditions.</span></p> ]]> Prospective Improvements for Safer Fuel Tanks: Experimental Tests g. janszenx a. galbiati l. di landro doi: 10.2495/CMEM-V4-N1-50-57 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 50 10.2495/CMEM-V4-N1-50-57 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-50-57 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-42-49 Flow within thick liquid films present owing to capillary effects in the pore space is of key importance in many multiphase flow applications in porous media, for example, drying or oil recovery processes. The viscous resistance to the flow is a key parameter for modelling fluid transport in such situations. It is well known for liquid films wetting the corners of tubes of polygonal cross-section. In this latter case, the liquid films shape is simple and can be readily obtained. The situation is much more involved when considering a realistic pore space, as in a packing of spherical particles, for example. In this case, X-ray tomography observations have shown that most of the liquid is confined around contact points between particles at intermediate liquid saturation. Nonetheless, a connectivity of all the liquid bridges throughout the particle packing can exist, allowing liquid transport across the porous medium. The ultimate goal of the present research is to provide the viscous flow resistance for such capillary liquid cluster of complex shape. As a first step in this direction, we present in this paper direct numerical simulation of the Stokes flow in liquid bridges obtained between two cylindrical pillars confined between two hori- zontal plates. The liquid bridge shape is obtained under conditions of hydrostatic equilibrium thanks to the Surface Evolver software. Then simulations of the viscous flow within the bridge are performed using Comsol Multiphysics® Creeping flow solver. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Flow within thick liquid films present owing to capillary effects in the pore space is of key importance in many multiphase flow applications in porous media, for example, drying or oil recovery processes. The viscous resistance to the flow is a key parameter for modelling fluid transport in such situations. It is well known for liquid films wetting the corners of tubes of polygonal cross-section. In this latter case, the liquid films shape is simple and can be readily obtained. The situation is much more involved when considering a realistic pore space, as in a packing of spherical particles, for example. In this case, X-ray tomography observations have shown that most of the liquid is confined around contact points between particles at intermediate liquid saturation. Nonetheless, a connectivity of all the liquid bridges throughout the particle packing can exist, allowing liquid transport across the porous medium. The ultimate goal of the present research is to provide the viscous flow resistance for such capillary liquid cluster of complex shape. As a first step in this direction, we present in this paper direct numerical simulation of the Stokes flow in liquid bridges obtained between two cylindrical pillars confined between two hori- zontal plates. The liquid bridge shape is obtained under conditions of hydrostatic equilibrium thanks to the Surface Evolver software. Then simulations of the viscous flow within the bridge are performed using Comsol Multiphysics</span>^®<span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Creeping flow solver.</span></p> ]]> Towards the Computation of Viscous Flow Resistance of a Liquid Bridge c. chen p. duru m. prat p. joseph s. geoffroy doi: 10.2495/CMEM-V4-N1-42-49 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 42 10.2495/CMEM-V4-N1-42-49 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-42-49 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-33-41 Binary drop electrocoalescence is the process of inducing two drops, suspended in an immiscible fluid, to coalesce in the presence of an external electric field. Electric forces have been known to accelerate the rupture of the interfacial film and enhance drop coalescence but the process has not been well characterized. The effects of the drop ion concentration and interfacial tension on the coalescence process are studied. It is shown that increasing interfacial tension, along with electric field makes it more likely that the drops stabilize after coalescence, as opposed to breaking up. This is due to the relative magnitudes of the drop deformation and charge separation timescales. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Binary drop electrocoalescence is the process of inducing two drops, suspended in an immiscible fluid, to coalesce in the presence of an external electric field. Electric forces have been known to accelerate the rupture of the interfacial film and enhance drop coalescence but the process has not been well characterized. The effects of the drop ion concentration and interfacial tension on the coalescence process are studied. It is shown that increasing interfacial tension, along with electric field makes it more likely that the drops stabilize after coalescence, as opposed to breaking up. This is due to the relative magnitudes of the drop deformation and charge separation timescales.</span></p> ]]> Electrohydrodynamic Deformation and Interaction of Microscale Drop Pairs r. pillai j.d. berry d.j.e. harvie m.r. davidson doi: 10.2495/CMEM-V4-N1-33-41 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 33 10.2495/CMEM-V4-N1-33-41 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-33-41 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-24-32 Water droplets emitted from cooling towers must be prevented for several reasons, human health hazards are the most important ones. The generation and control of these droplets are the main tasks for drift eliminators: devices installed inside mechanical draft cooling towers useful to prevent water droplets, originated by the crossflow between air and water inside the tower, from being released into the environment. This is the phenomenon called ‘drift’. In this paper, the operating conditions of a type of drift eliminator placed in a cooling tower are studied. This work is focused on the numerical and experimental characterization of the multiphase flow taking place when water droplets, drifted by the airstream, impact on the water film formed over the drift eliminators plates. The problem of these drop impacts has been studied throughout an experimental installation and a numerical model has been developed throughout the ANSYS software and several VOF multiphase flow simulations have been carried out showing a good agreement with experimental data. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Water droplets emitted from cooling towers must be prevented for several reasons, human health hazards are the most important ones. The generation and control of these droplets are the main tasks for drift eliminators: devices installed inside mechanical draft cooling towers useful to prevent water droplets, originated by the crossflow between air and water inside the tower, from being released into the environment. This is the phenomenon called ‘drift’. In this paper, the operating conditions of a type of drift eliminator placed in a cooling tower are studied. This work is focused on the numerical and experimental characterization of the multiphase flow taking place when water droplets, drifted by the airstream, impact on the water film formed over the drift eliminators plates. The problem of these drop impacts has been studied throughout an experimental installation and a numerical model has been developed throughout the ANSYS software and several VOF multiphase flow simulations have been carried out showing a good agreement with experimental data.</span></p> ]]> Analysis of the Impact of Droplets onto Water Films in Drift Eliminators j. lópez a. s. káiser b. zamora a. viedma j. a. vera m. jiménez j. ruiz m. lucas doi: 10.2495/CMEM-V4-N1-24-32 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 24 10.2495/CMEM-V4-N1-24-32 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-24-32 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-13-23 The subject matter of this paper involves the examination of the process of liquid drop formation at the outlet of a nozzle. A theoretical model of the formation of liquid droplet has been developed. The model is based on a recursive equation. Solution of this equation is obtained by the solution set, which is similar to the process of liquid droplets formation. The objective is to demonstrate that a recursive theoretical model can reproduce the chaotic behavior of physical phenomena, which is the formation of liquid droplets. In this paper, it is the assessment of the non-stationary characteristics in the process of drop formation. The potential for describing it in terms of principles familiar from deterministic chaos is presented. The paper contains the results of experiments which indicate that chaotic phenomena occur during the formation of liquid drops. The results of the research are elaborated and presented in the form of attractors and power spectrum diagrams. The ranges of the parameters are determined for which the time intervals between the successive drops tend to be non-stationary. Their presentation in the phase space has revealed the occurrence of chaotic phenomena. It was concluded that numerical calculations and the results gained from experiment are comparable. Consequently, it was indicated that relatively simple mathematical model can be used for simulation of the states of actual physical processes. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The subject matter of this paper involves the examination of the process of liquid drop formation at the outlet of a nozzle. A theoretical model of the formation of liquid droplet has been developed. The model is based on a recursive equation. Solution of this equation is obtained by the solution set, which is similar to the process of liquid droplets formation. The objective is to demonstrate that a recursive theoretical model can reproduce the chaotic behavior of physical phenomena, which is the formation of liquid droplets. In this paper, it is the assessment of the non-stationary characteristics in the process of drop formation. The potential for describing it in terms of principles familiar from deterministic chaos is presented. The paper contains the results of experiments which indicate that chaotic phenomena occur during the formation of liquid drops. The results of the research are elaborated and presented in the form of attractors and power spectrum diagrams. The ranges of the parameters are determined for which the time intervals between the successive drops tend to be non-stationary. Their presentation in the phase space has revealed the occurrence of chaotic phenomena. It was concluded that numerical calculations and the results gained from experiment are comparable. Consequently, it was indicated that relatively simple mathematical model can be used for simulation of the states of actual physical processes.</span></p> ]]> The Theoretical and Experimental Study of Deterministic Chaos Phenomena in a Process of Liquid Droplets Formation m. r. rzasa b. dobrowolski doi: 10.2495/CMEM-V4-N1-13-23 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 13 10.2495/CMEM-V4-N1-13-23 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-13-23 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-1-12 The performance of a gas–liquid cylindrical cyclone separator for the separation of air bubbles from hydraulic fluid has been analyzed numerically using the commercial computational fluid dynamics flow solver CFX. Two-phase flow behavior is modeled based on an Eulerian–Eulerian approach, representing both liquid and dispersed gas phase as interpenetrating media with interphase momentum transfer captured based on existing bubble drag models. Only a single bubble size is considered for the dispersed phase and bubble coalescence is ignored. At the tangential inlet, a homogeneous gas– liquid mixture is assumed with specified mass flow and air/liquid volume fractions. Pressure conditions were imposed at both the upper gas outlet and the lower liquid outlet boundaries. Effect of changes in turbulence model and bubble drag model on analysis predictions was analyzed for selected operating conditions, that is, bubble sizes, air/liquid volume fractions and flow rates. Separation efficiency was high only for larger bubble sizes (100 mm) and high flow rates (250 L/min). For bubble sizes below 35 mm, the cyclone was ineffective. At high flow rates, cyclone performance suffers due to liquid carry over in the form of a swirling liquid wall film carried with the gas (bubble) phase through the top outlet. The Explicit Algebraic Reynolds Stress Turbulence Model together with the Grace Drag Model was found to be effective in exploring changes to the cyclone geometry. Here, improvements in separation efficiency were only achieved with significantly increased tangential velocities as a consequences of a reduced inlet port cross section. Predicted bubble size separation limits as a function of Reynolds number and axial-to-tangential velocity ratios were found to compare favorably with existing literature. <![CDATA[ <p>The performance of a gas–liquid cylindrical cyclone separator for the separation of air bubbles from hydraulic fluid has been analyzed numerically using the commercial computational fluid dynamics flow solver CFX. Two-phase flow behavior is modeled based on an Eulerian–Eulerian approach, representing both liquid and dispersed gas phase as interpenetrating media with interphase momentum transfer captured based on existing bubble drag models. Only a single bubble size is considered for the dispersed phase and bubble coalescence is ignored. At the tangential inlet, a homogeneous gas– liquid mixture is assumed with specified mass flow and air/liquid volume fractions. Pressure conditions were imposed at both the upper gas outlet and the lower liquid outlet boundaries. Effect of changes in turbulence model and bubble drag model on analysis predictions was analyzed for selected operating conditions, that is, bubble sizes, air/liquid volume fractions and flow rates. Separation efficiency was high only for larger bubble sizes (100 mm) and high flow rates (250 L/min). For bubble sizes below 35 mm, the cyclone was ineffective. At high flow rates, cyclone performance suffers due to liquid carry over in the form of a swirling liquid wall film carried with the gas (bubble) phase through the top outlet. The Explicit Algebraic Reynolds Stress Turbulence Model together with the Grace Drag Model was found to be effective in exploring changes to the cyclone geometry. Here, improvements in separation efficiency were only achieved with significantly increased tangential velocities as a consequences of a reduced inlet port cross section. Predicted bubble size separation limits as a function of Reynolds number and axial-to-tangential velocity ratios were found to compare favorably with existing literature.</p> ]]> Dispersed Two-Phase Flow in A Gas–Liquid Cylindrical Cyclone Separator carsten mehring doi: 10.2495/CMEM-V4-N1-1-12 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2016 4 1 Article 1 10.2495/CMEM-V4-N1-1-12 https://www.acadlore.com/article/IJCMEM/2016_4_1/CMEM-V4-N1-1-12 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-340-349 Structural, optical and electronic properties and elastic constants of Be1–xZnxS alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers–Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard’s law. It is seen that results obtained from theory and experiments are all in agreement. <![CDATA[ <p>Structural, optical and electronic properties and elastic constants of Be1–xZnxS alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers–Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard’s law. It is seen that results obtained from theory and experiments are all in agreement.</p> ]]> DFT and X-Ray Study of Structural, Electronic, Elastic and Optical Properties in BE1–XZNXS Alloys Depending on Vegard’S Law a. gultekin p. pashaei z. khan m.k. ozturk m. tamer y. bas doi: 10.2495/CMEM-V3-N4-340-349 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 4 Article 340 10.2495/CMEM-V3-N4-340-349 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-340-349 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-329-339 In this paper, the nickel–phosphorus (Ni–P) diffusion barrier layer between Sn–4Ag–0.5Cu solder alloy and copper-printed circuit board was developed. The electroless plating technique was used to develop Ni–P diffusion barrier layer with different percentage of phosphorus content, which are 1–5 wt% (low), 5–8 wt% (medium) and above 8 wt% (high). The results reveal that the high phosphorus content in nickel layer acts as a good diffusion barrier for Sn–4Ag–0.5Cu since it can suppress the intermetallic compound formation. This is because in higher phosphorus content, the grain boundaries were found to be eliminated. Hence, resulted in thinner intermetallic compound thickness. <![CDATA[ <p>In this paper, the nickel–phosphorus (Ni–P) diffusion barrier layer between Sn–4Ag–0.5Cu solder alloy and copper-printed circuit board was developed. The electroless plating technique was used to develop Ni–P diffusion barrier layer with different percentage of phosphorus content, which are 1–5 wt% (low), 5–8 wt% (medium) and above 8 wt% (high). The results reveal that the high phosphorus content in nickel layer acts as a good diffusion barrier for Sn–4Ag–0.5Cu since it can suppress the intermetallic compound formation. This is because in higher phosphorus content, the grain boundaries were found to be eliminated. Hence, resulted in thinner intermetallic compound thickness.</p> ]]> Development of Diffusion Barrier Layer on Copper-Printed Circuit Board Using Electroless Plating Method siti rabiatull aisha idris ali ourdjini azmah hanim mohamad ariff saliza azlina osman doi: 10.2495/CMEM-V3-N4-329-339 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 4 Article 329 10.2495/CMEM-V3-N4-329-339 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-329-339 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-316-328 The influence of three parameters, i.e. interfacial roughness λ, coating thickness h and impurity radius r at the coating–substrate interface on interfacial toughness, has been investigated within the framework of two approaches, i.e. thermodynamics and fracture mechanics. The governing equations for both the approaches have been derived independently and then fused to form a governing law for evaluating the interfacial toughness. The analysis in this paper which considers three parameters (λ, h and r) has been divided into three setups. Each setup is used to analyse the effect of one variable parameter on interfacial toughness while keeping the other two parameters constant. Three samples for each setup were prepared considering the requirements of constant and variable parameters for each setup. Simulation techniques founded on the experimental studies have been developed during this research in order to find the optimised values of three parameters. These optimised values act as critical values (boundary point) between coating fail-safe and coating fail conditions. The experiment employed ASTM-B117 test, which is used to analyse the interfacial toughness of samples under each setup. These experiments showed excellent, quantitative agreement with the simulation trends predicted by the theoretical model. <![CDATA[ <p>The influence of three parameters, i.e. interfacial roughness λ, coating thickness h and impurity radius r at the coating–substrate interface on interfacial toughness, has been investigated within the framework of two approaches, i.e. thermodynamics and fracture mechanics. The governing equations for both the approaches have been derived independently and then fused to form a governing law for evaluating the interfacial toughness. The analysis in this paper which considers three parameters (λ, h and r) has been divided into three setups. Each setup is used to analyse the effect of one variable parameter on interfacial toughness while keeping the other two parameters constant. Three samples for each setup were prepared considering the requirements of constant and variable parameters for each setup. Simulation techniques founded on the experimental studies have been developed during this research in order to find the optimised values of three parameters. These optimised values act as critical values (boundary point) between coating fail-safe and coating fail conditions. The experiment employed ASTM-B117 test, which is used to analyse the interfacial toughness of samples under each setup. These experiments showed excellent, quantitative agreement with the simulation trends predicted by the theoretical model.</p> ]]> Maximising the Interfacial Toughness of Thin Coatings and Substrate Through Optimisation of Defined Parameters m. h nazir z. khan doi: 10.2495/CMEM-V3-N4-316-328 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 4 Article 316 10.2495/CMEM-V3-N4-316-328 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-316-328 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-305-315 This article presents a study of the sensitivities of different parameters that affect the accuracy of simulating flyer plate impact experiments. Two approaches are explored: the CTH hydrodynamic and the LS-DYNA smoothed particle hydrodynamic (SPH) codes. Simulations using these two methods are compared to experimental data from a single-stage gas gun experiment in which a copper flyer plate impacted another copper target plate. The experiment was designed to cause spall in the target plate. The numerical simulations are conducted using these combined physics models: the Mie–Grüneisen equation of state, the Johnson–Cook compressive strength model, and spall rupture. Effects of artificial viscosity, spall strength, and computational cell size are studied and discussed with the objective of improving the accuracy of these simulations. The results are verified by applying the proposed simulation approach to other flyer plate experiments. <![CDATA[ <p>This article presents a study of the sensitivities of different parameters that affect the accuracy of simulating flyer plate impact experiments. Two approaches are explored: the CTH hydrodynamic and the LS-DYNA smoothed particle hydrodynamic (SPH) codes. Simulations using these two methods are compared to experimental data from a single-stage gas gun experiment in which a copper flyer plate impacted another copper target plate. The experiment was designed to cause spall in the target plate. The numerical simulations are conducted using these combined physics models: the Mie–Grüneisen equation of state, the Johnson–Cook compressive strength model, and spall rupture. Effects of artificial viscosity, spall strength, and computational cell size are studied and discussed with the objective of improving the accuracy of these simulations. The results are verified by applying the proposed simulation approach to other flyer plate experiments.</p> ]]> Parametric Sensitivity Comparison of Simulation Models for Flyer Plate Impact Experiments d. somasundaram s. k. roy m. trabia b. o’toole r. hixson doi: 10.2495/CMEM-V3-N4-305-315 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 4 Article 305 10.2495/CMEM-V3-N4-305-315 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-305-315 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-291-304 This paper explores, through the medium of literature review and a single in-depth empirical study conducted over a 1-year period, the ways in which a third sector organisation (TSO) is engaging in reuse behaviour change. The paper forms part of a larger scale PhD research project examining the ways in which corporate bodies can be helped to implement the UK government’s ambition to move up the so-called waste hierarchy from recycling to ‘reuse and preparing for reuse’ [1]. The paper starts by exploring the existing literature on current reuse practices, which both confirms that normative behaviour is concentrated on recycling and identifies TSOs as leading proactive stakeholders in promoting reuse behaviour, noting that the literature is generally limited to household waste. Therefore, the empirical research sought to understand and identify whether, and if so how, normative behaviour towards reuse can be developed both within TSOs and potentially their business supply chain network. The paper reports on a single TSO (the Selby Trust), studied through a process of engaged action research and testing a behaviour change theoretical framework developed by Tavri et al. [2]. The action research tested the theory that by building a process known as ‘associative strength’ [3, 4], motivation for organisational behaviour change can be developed and, over the short term at least, maintained. The results point to the possibility of the case being replicable across other TSOs and throughout the business supply chain. <![CDATA[ <p>This paper explores, through the medium of literature review and a single in-depth empirical study conducted over a 1-year period, the ways in which a third sector organisation (TSO) is engaging in reuse behaviour change. The paper forms part of a larger scale PhD research project examining the ways in which corporate bodies can be helped to implement the UK government’s ambition to move up the so-called waste hierarchy from recycling to ‘reuse and preparing for reuse’ [1]. The paper starts by exploring the existing literature on current reuse practices, which both confirms that normative behaviour is concentrated on recycling and identifies TSOs as leading proactive stakeholders in promoting reuse behaviour, noting that the literature is generally limited to household waste. Therefore, the empirical research sought to understand and identify whether, and if so how, normative behaviour towards reuse can be developed both within TSOs and potentially their business supply chain network. The paper reports on a single TSO (the Selby Trust), studied through a process of engaged action research and testing a behaviour change theoretical framework developed by Tavri et al. [2]. The action research tested the theory that by building a process known as ‘associative strength’ [3, 4], motivation for organisational behaviour change can be developed and, over the short term at least, maintained. The results point to the possibility of the case being replicable across other TSOs and throughout the business supply chain.</p> ]]> Organisational Behaviour Change Towards Waste Reuse in the UK Third Sector p. tavri s. sayce v. hands doi: 10.2495/CMEM-V3-N4-291-304 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 4 Article 291 10.2495/CMEM-V3-N4-291-304 https://www.acadlore.com/article/IJCMEM/2015_3_4/CMEM-V3-N4-291-304 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-iii This Special Issue contains some of the papers presented at MIT to pay tribute to Professor Jerry Connor of its Civil Engineering Department on the occasion of his retirement after 60 years there. The event was fully reported in Volume 2, Number 4 of this Journal. The occasion brought together a number of academics and professionals who were profoundly influenced by Jerry’s knowledge and personality, whose support was decisive for starting their careers off on the right track, my own included. In my case, my association with Jerry helped me to clarify and extend the finite element concepts and integral equations mathematical tools that gave rise to the Boundary Element Method. Professor Herbert Einstein, one of his colleagues at MIT, commented on Jerry’s ability to always be ahead of what needs to be solved. He introduced a series of major innovations in research and teaching of Civil Engineering, always keeping in mind the professional relevance of whatever he was teaching. Herbert was grateful to Jerry for his help in reaching tenure at MIT and for his many illuminating discussions. He concluded by describing his contribution in engineering. Jerry, Herbert said, is an engineer’s engineer! Professor Jose Roesset, remembers Jerry’s teaching as a breath of fresh air, managing to simplify the most difficult of problems to their fundamentals and applying simple concepts. Jerry, Jose said, is foremost a teacher and a true scholar. Jerry’s influence on Ove Gudmestad, was decisive in shaping his career in the offshore oil industry. Some topics of Ove’s research, including the development of arctic engineering and earthquake effects, arose out of his collaboration with Jerry. More importantly perhaps was the fact that Jerry impressed on Ove the need to carry out research work thoroughly and as a team member. John Niedzwecki, now Professor at Texas A&M, related how he started work on artificial intelligence under Jerry’s guidance. This resulted in John’s innovative research on offshore structures instrumentation tools.Petros Komodromos, now at the University of Cyprus, expressed his appreciation to Jerry for his support during his PhD thesis. He is author of many papers on the Response of Seismically isolated Buildings, a topic he has fully developed in several publications, including a book.Mauricio Sarrazin, Head of his own Consulting firm and Professor at the University of Chile, referred also to the importance of Jerry in the development of his own career particularly on the solution of non linear equilibrium problems. Professor Simon Laflamme of Iowa State University on coming to MIT, was impressed by the way Jerry interacted with his students, particularly those in the Master of Engineering programme which he created and which, every year, included a trip abroad at the end to visit outstanding engineering works. Jerry’s input has had a great impact on several generations of researchers, changing their lives, including my own. A secret of his success has been his ability to listen and respect the opinions of all his colleagues and students. Jerry maintained that students should be treated as equals, instilling in them the confidence that they would require in their future professional lives, just one of the many reasons why so many of us feel indebted to Jerry. <![CDATA[ <p>This Special Issue contains some of the papers presented at MIT to pay tribute to Professor Jerry Connor of its Civil Engineering Department on the occasion of his retirement after 60 years there. The event was fully reported in Volume 2, Number 4 of this Journal. The occasion brought together a number of academics and professionals who were profoundly influenced by Jerry’s knowledge and personality, whose support was decisive for starting their careers off on the right track, my own included. In my case, my association with Jerry helped me to clarify and extend the finite element concepts and integral equations mathematical tools that gave rise to the Boundary Element Method. </p><p>Professor Herbert Einstein, one of his colleagues at MIT, commented on Jerry’s ability to always be ahead of what needs to be solved. He introduced a series of major innovations in research and teaching of Civil Engineering, always keeping in mind the professional relevance of whatever he was teaching. Herbert was grateful to Jerry for his help in reaching tenure at MIT and for his many illuminating discussions. He concluded by describing his contribution in engineering. Jerry, Herbert said, is an engineer’s engineer! Professor Jose Roesset, remembers Jerry’s teaching as a breath of fresh air, managing to simplify the most difficult of problems to their fundamentals and applying simple concepts. Jerry, Jose said, is foremost a teacher and a true scholar. Jerry’s influence on Ove Gudmestad, was decisive in shaping his career in the offshore oil industry. Some topics of Ove’s research, including the development of arctic engineering and earthquake effects, arose out of his collaboration with Jerry. More importantly perhaps was the fact that Jerry impressed on Ove the need to carry out research work thoroughly and as a team member. John Niedzwecki, now Professor at Texas A&M, related how he started work on artificial intelligence under Jerry’s guidance. This resulted in John’s innovative research on offshore structures instrumentation tools.</p><p>Petros Komodromos, now at the University of Cyprus, expressed his appreciation to Jerry for his support during his PhD thesis. He is author of many papers on the Response of Seismically isolated Buildings, a topic he has fully developed in several publications, including a book.</p><p>Mauricio Sarrazin, Head of his own Consulting firm and Professor at the University of Chile, referred also to the importance of Jerry in the development of his own career particularly on the solution of non linear equilibrium problems. Professor Simon Laflamme of Iowa State University on coming to MIT, was impressed by the way Jerry interacted with his students, particularly those in the Master of Engineering programme which he created and which, every year, included a trip abroad at the end to visit outstanding engineering works. Jerry’s input has had a great impact on several generations of researchers, changing their lives, including my own. A secret of his success has been his ability to listen and respect the opinions of all his colleagues and students. Jerry maintained that students should be treated as equals, instilling in them the confidence that they would require in their future professional lives, just one of the many reasons why so many of us feel indebted to Jerry.</p><p></p> ]]> Preface doi: 10.2495/CMEM-V3-N3-iii International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 0 10.2495/CMEM-V3-N3-iii https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-iii https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-269-278 The complex variable boundary element method or CVBEM is a numerical technique that can provide solutions to potential value problems in two or more dimensions by the use of an approximation function that is derived from the Cauchy integral equation in complex analysis. Given the potential values (i.e. a Dirichlet problem) along the boundary, the typical problem is to use the potential function to solve the governing Laplace equation. In this approach, it is not necessary to know the streamline values on the boundary. The modeling approach can be extended to problems where the streamline function is needed because there are known streamline values along the problem boundary (i.e. a mixed boundary value problem). Two common problems that have such conditions are insulation on a boundary and fluid flow around a solid obstacle. In this paper, five advances in the CVBEM are made with respect to the modeling of the mixed boundary value problem; namely (1) the use of Mathematica and Matlab in tandem to calculate and plot the flow net of a boundary value problem. (2) The magnitude of the size of the problem domain is extended. (3) The modeling results include direct computation and development of a flow net. (4) The graphical displays of the total flownet are developed simultaneously. And (5) the nodal point location as an additional degree of freedom in the CVBEM modeling approach is extended to mixed boundaries. A demonstration problem of fluid flow is included to illustrate the flownet development capability. <![CDATA[ <p>The complex variable boundary element method or CVBEM is a numerical technique that can provide solutions to potential value problems in two or more dimensions by the use of an approximation function that is derived from the Cauchy integral equation in complex analysis. Given the potential values (i.e. a Dirichlet problem) along the boundary, the typical problem is to use the potential function to solve the governing Laplace equation. In this approach, it is not necessary to know the streamline values on the boundary. The modeling approach can be extended to problems where the streamline function is needed because there are known streamline values along the problem boundary (i.e. a mixed boundary value problem). Two common problems that have such conditions are insulation on a boundary and fluid flow around a solid obstacle. In this paper, five advances in the CVBEM are made with respect to the modeling of the mixed boundary value problem; namely (1) the use of Mathematica and Matlab in tandem to calculate and plot the flow net of a boundary value problem. (2) The magnitude of the size of the problem domain is extended. (3) The modeling results include direct computation and development of a flow net. (4) The graphical displays of the total flownet are developed simultaneously. And (5) the nodal point location as an additional degree of freedom in the CVBEM modeling approach is extended to mixed boundaries. A demonstration problem of fluid flow is included to illustrate the flownet development capability.</p> ]]> Modeling Mixed Boundary Problems with the Complex Variable Boundary Element Method (CVBEM) Using Matlab and Mathematica anthony n. johnson t. v. hromadka ii m. t. hughes s. b. horton doi: 10.2495/CMEM-V3-N3-269-278 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 269 10.2495/CMEM-V3-N3-269-278 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-269-278 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-250-268 This article reviews numerical modeling methods for certain electromagnetic compatibility topics in wind turbine (WT) analysis. Some scenarios in which WTs behave as electromagnetic interference sources and victims, respectively, are considered. The formulation is carried out in the frequency domain and it is based on the related Electric Field Integral Equation type. The numerical solution of the governing equations is obtained by some variants of the boundary element method. The computational examples are related to the transient response of WTs struck by lightning and to the disturbances of radio system operation caused by WTs. The analysis of WT impact to the radar system operation is carried out by solving the corresponding integral equations via the boundary integral equation method combined with physical optics. <![CDATA[ <p>This article reviews numerical modeling methods for certain electromagnetic compatibility topics in wind turbine (WT) analysis. Some scenarios in which WTs behave as electromagnetic interference sources and victims, respectively, are considered. The formulation is carried out in the frequency domain and it is based on the related Electric Field Integral Equation type. The numerical solution of the governing equations is obtained by some variants of the boundary element method. The computational examples are related to the transient response of WTs struck by lightning and to the disturbances of radio system operation caused by WTs. The analysis of WT impact to the radar system operation is carried out by solving the corresponding integral equations via the boundary integral equation method combined with physical optics.</p> ]]> Electromagnetic Compatibility Issues of Wind Turbine Analysis and Design d. poljak d. čavka doi: 10.2495/CMEM-V3-N3-250-268 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 250 10.2495/CMEM-V3-N3-250-268 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-250-268 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-230-249 Fabrication of silicon carbide fibres reinforced silicon carbide composite (SiC/SiC) by chemical vapour infiltration (CVI) process was investigated in this research with the help of both simulation and experimental set-up. CVI of silicon carbide preform was carried out through the pyrolysis of methyltrichlorosilane (MTS) over a broad temperature range at atmospheric pressure. The overall aim was the morphological description of the matrix (co-deposition of Si, SiC and C) during pyrolysis of MTS by CVI process and its state-of-the-art numerical calculation. Phase-field model was developed and deployed to predict the evolution of the microstructures and to describe the influence of the infiltration conditions on the properties of the composite during CVI process in conjunction with the implication of finite element method. Both mass transport and fluid motion in gas phase were considered. Experimental results exhibit three deposition regimes at different temperature ranges as predicted by the numerical simulation results. This also implies different deposition kinetics involved as investigated in the present research. The great difference of the steady-state deposition rate exceeding three orders of magnitude was explained in terms of a multiple steady-state surface reaction model of co-deposition of SiC, Si and C. Corresponding gas-phase compositions, over the temperature region covered in the present experiments, were calculated with a detailed pyrolysis reaction mechanism of MTS. <![CDATA[ <p>Fabrication of silicon carbide fibres reinforced silicon carbide composite (SiC/SiC) by chemical vapour infiltration (CVI) process was investigated in this research with the help of both simulation and experimental set-up. CVI of silicon carbide preform was carried out through the pyrolysis of methyltrichlorosilane (MTS) over a broad temperature range at atmospheric pressure. The overall aim was the morphological description of the matrix (co-deposition of Si, SiC and C) during pyrolysis of MTS by CVI process and its state-of-the-art numerical calculation. Phase-field model was developed and deployed to predict the evolution of the microstructures and to describe the influence of the infiltration conditions on the properties of the composite during CVI process in conjunction with the implication of finite element method. Both mass transport and fluid motion in gas phase were considered. Experimental results exhibit three deposition regimes at different temperature ranges as predicted by the numerical simulation results. This also implies different deposition kinetics involved as investigated in the present research. The great difference of the steady-state deposition rate exceeding three orders of magnitude was explained in terms of a multiple steady-state surface reaction model of co-deposition of SiC, Si and C. Corresponding gas-phase compositions, over the temperature region covered in the present experiments, were calculated with a detailed pyrolysis reaction mechanism of MTS.</p> ]]> A Coupled Numerical Modelling and Experimental Approach in Chemical Vapour Infiltration (CVI) Process of Sic/Sic Composites e. schnack a. li a. m. rahman y. zhu doi: 10.2495/CMEM-V3-N3-230-249 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 230 10.2495/CMEM-V3-N3-230-249 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-230-249 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-205-229 Long span bridges and high rise buildings are two types of structures that have always arisen the atten­tion of engineers and architects. The former are appropriate for creating crossings over wide rivers or estuaries in a sort of recreation of the geography of our planet. The latter are many times used to be a symbol of the wealthy of the cities where they are erected.Construction of both typologies has experienced a dramatic activity since the last decades of the past century in many countries located in different continents such as Europe, Asia or America, and such tendency has even increased in recent years, and several challenging proposals have also been proposed for the years to come.This article starts with a brief description of the capabilities and advantages of long span bridges and tall buildings. Afterwards, a description of the main realizations of suspension and cable-stayed bridges already existing all around the world is presented mentioning their main characteristics and fea­tures. Additionally, information on bridge projects that could take place in a near future are mentioned. Then, a similar treatment is carried out for the vast collection of signature buildings erected in the last decades. It will be observed that in addition to the new tall structures in already very cosmopolitan cit­ies, many of them have been built in other places and have transformed radically the skyline of cities in China, Singapore, Korea or the Arabic Gulf countries, to name a few. <![CDATA[ <p>Long span bridges and high rise buildings are two types of structures that have always arisen the atten­tion of engineers and architects. The former are appropriate for creating crossings over wide rivers or estuaries in a sort of recreation of the geography of our planet. The latter are many times used to be a symbol of the wealthy of the cities where they are erected.</p><p>Construction of both typologies has experienced a dramatic activity since the last decades of the past century in many countries located in different continents such as Europe, Asia or America, and such tendency has even increased in recent years, and several challenging proposals have also been proposed for the years to come.</p><p>This article starts with a brief description of the capabilities and advantages of long span bridges and tall buildings. Afterwards, a description of the main realizations of suspension and cable-stayed bridges already existing all around the world is presented mentioning their main characteristics and fea­tures. Additionally, information on bridge projects that could take place in a near future are mentioned. Then, a similar treatment is carried out for the vast collection of signature buildings erected in the last decades. It will be observed that in addition to the new tall structures in already very cosmopolitan cit­ies, many of them have been built in other places and have transformed radically the skyline of cities in China, Singapore, Korea or the Arabic Gulf countries, to name a few.</p> ]]> Design Of Long Span Bridges And High Rise Buildings In The Twenty-First Century s. hernandez doi: 10.2495/CMEM-V3-N3-205-229 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 205 10.2495/CMEM-V3-N3-205-229 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-205-229 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-187-204 The theory of morphological indicators (MI) provides user-friendly tools guiding the structural designer towards low volume consuming solutions during the exploration and comparison of different structural types. Since a first doctoral thesis published in 1999, a decade of research has refined MI into a bench­marked structural optimisation method for conceptual design. This article surveys the milestones that lead to today’s method and contains the published references that contributed to the major evolutions of MI. The article also refers to the work of other researchers in structural and architectural engineer­ing, this time in the quest of optimisation of structures through a more sustainable design, offering the possibility of re-use and recombination of structural components. This technique, called 4D design methodology, was based on a research proposal by Hendrickx and Van Walleghem, which was further developed at Vrije Universiteit Brussel. <![CDATA[ <p>The theory of morphological indicators (<em>MI</em>) provides user-friendly tools guiding the structural designer towards low volume consuming solutions during the exploration and comparison of different structural types. Since a first doctoral thesis published in 1999, a decade of research has refined <em>MI </em>into a bench­marked structural optimisation method for conceptual design. This article surveys the milestones that lead to today’s method and contains the published references that contributed to the major evolutions of <em>MI</em>. The article also refers to the work of other researchers in structural and architectural engineer­ing, this time in the quest of optimisation of structures through a more sustainable design, offering the possibility of re-use and recombination of structural components. This technique, called 4D design methodology, was based on a research proposal by Hendrickx and Van Walleghem, which was further developed at Vrije Universiteit Brussel.</p> ]]> Structural Optimisation and Sustainable Design w.p. de wilde t. vandenbergh w. debacker doi: 10.2495/CMEM-V3-N3-187-204 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 3 Article 187 10.2495/CMEM-V3-N3-187-204 https://www.acadlore.com/article/IJCMEM/2015_3_3/CMEM-V3-N3-187-204 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-89-100 Increasing attention toward electromagnetic interference (EMI) in defense applications has resulted in initiatives to develop multifunctional materials that can satisfy structural performance requirements while effectively shielding electronic components from EMI. The goal of this article is to characterize the electrical properties of carbon nanotube (CNT) loaded resins with an emphasis on those properties that directly influence EMI shielding effectiveness; particularly conductivity. Limiting the measurements to conductivity allowed studying a wide range of candidate materials to identify the most promising combinations of overall cost, manufacturing process and materials. Various parameters affecting the conductivity of CNT-loaded resins were considered in this study from CNT characteristics (CNT loading as weight percentage and functionalization) and dispersion processes (sonication or microfluidization) used during fabrication. Electrical testing of specimens was conducted using a low-frequency impedance analyzer in order to measure the conductivity of manufactured CNT-loaded materials for a wide range of frequencies depending on the experiment. For the materials and conditions tested, the percolation threshold (CNT loading that produces a conductive material) was established to be approximately 0.3% by weight. Given the low percolation threshold, these results can be considered as a positive indication that CNT-loaded resins can be incorporated into conventional composites intended for load bearing applications and provide EMI shielding as well. An even more promising approach is to incorporate CNTs into composites using nanocomp-non-woven-fabric, which results in conductivities of 102 S/cm. <![CDATA[ <p>Increasing attention toward electromagnetic interference (EMI) in defense applications has resulted in initiatives to develop multifunctional materials that can satisfy structural performance requirements while effectively shielding electronic components from EMI. The goal of this article is to characterize the electrical properties of carbon nanotube (CNT) loaded resins with an emphasis on those properties that directly influence EMI shielding effectiveness; particularly conductivity. Limiting the measurements to conductivity allowed studying a wide range of candidate materials to identify the most promising combinations of overall cost, manufacturing process and materials. Various parameters affecting the conductivity of CNT-loaded resins were considered in this study from CNT characteristics (CNT loading as weight percentage and functionalization) and dispersion processes (sonication or microfluidization) used during fabrication. Electrical testing of specimens was conducted using a low-frequency impedance analyzer in order to measure the conductivity of manufactured CNT-loaded materials for a wide range of frequencies depending on the experiment. For the materials and conditions tested, the percolation threshold (CNT loading that produces a conductive material) was established to be approximately 0.3% by weight. Given the low percolation threshold, these results can be considered as a positive indication that CNT-loaded resins can be incorporated into conventional composites intended for load bearing applications and provide EMI shielding as well. An even more promising approach is to incorporate CNTs into composites using nanocomp-non-woven-fabric, which results in conductivities of 102 S/cm.</p> ]]> A Comparison of Electrical Properties of Carbon Nanotube-loaded Resins h. estrada l.s. lee j. trovillion m.tusz a. kumar l.d. stephenson doi: 10.2495/CMEM-V3-N2-89-100 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 89 10.2495/CMEM-V3-N2-89-100 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-89-100 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-79-88 This paper illustrates the dependence of the near-surface properties of polyethylene-based nanocomposites on the temperature and the nanofiller content using nanoindentation techniques. The specimens were manufactured by melt processing a premixed blend of 75 wt.% ultra-high molecular weight polyethylene (UHMWPE) and 25 wt.% high-density polyethylene (HDPE) with 0.5, 1 and 3 wt.% multiwalled carbon nanotube (MWCNT) or 0.5, 1 and 2 wt.% inorganic clay. The results showed that the incorporation of MWCNT can increase the indentation resistance, with indentation resistance increasing with filler content. The indentation resistance was significantly increased with the addition of 1 wt.% clay nanoparticles. However, increasing the volume fraction of clay nanoparticle further resulted in a reduction in the indentation resistance. The indentation hardness and elastic modulus were significantly increased with the incorporation of both MWCNT and clay nanoparticles at room temperature. At elevated temperatures, up to 65°C, a significant reduction was observed in the indentation resistance, hardness and elastic modulus, which indicated a thermal softening of the materials. However, it is interesting to find that the presence of the nanoparticle can enhance these properties at both room and high temperatures. Therefore, it is important to consider these variations in the near-surface properties of polyethylene-based nanocomposites when using such materials at various ambient temperatures. <![CDATA[ <p>This paper illustrates the dependence of the near-surface properties of polyethylene-based nanocomposites on the temperature and the nanofiller content using nanoindentation techniques. The specimens were manufactured by melt processing a premixed blend of 75 wt.% ultra-high molecular weight polyethylene (UHMWPE) and 25 wt.% high-density polyethylene (HDPE) with 0.5, 1 and 3 wt.% multiwalled carbon nanotube (MWCNT) or 0.5, 1 and 2 wt.% inorganic clay. The results showed that the incorporation of MWCNT can increase the indentation resistance, with indentation resistance increasing with filler content. The indentation resistance was significantly increased with the addition of 1 wt.% clay nanoparticles. However, increasing the volume fraction of clay nanoparticle further resulted in a reduction in the indentation resistance. The indentation hardness and elastic modulus were significantly increased with the incorporation of both MWCNT and clay nanoparticles at room temperature. At elevated temperatures, up to 65°C, a significant reduction was observed in the indentation resistance, hardness and elastic modulus, which indicated a thermal softening of the materials. However, it is interesting to find that the presence of the nanoparticle can enhance these properties at both room and high temperatures. Therefore, it is important to consider these variations in the near-surface properties of polyethylene-based nanocomposites when using such materials at various ambient temperatures.</p> ]]> High Temperature Effects on the Nanoindentation Behaviour of Polyethylene-based Nanocomposites a.s. alghamdi i.a. ashcroft m.o. song doi: 10.2495/CMEM-V3-N2-79-88 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 79 10.2495/CMEM-V3-N2-79-88 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-79-88 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-165-174 The MnO–Zn thin films were fabricated by radio frequency (RF) magnetron sputtering and compared with pulse electrodeposition (PED) Zn thin films, doped with MnO and ZrO nanoparticles. Surface morphology, structural properties, chemical composition and corrosion resistance of these coatings were investigated by using scanning electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, 3-D scanning interferometry and environmental chamber. Surface morphology and degree of crystallinity have different behaviours for different deposition methods. Pulse-coated films have polycrystalline structure with high surface roughness (Ra), whereas sputtered films are monocrys­talline with reduced roughness (Ra). Corrosion tests of both RF sputter and PED films revealed that the distribution of corrosion products formed on the surface of sputter films were not severe in extent as in case of electrodeposited coatings. Results showed that the doping of ZrO nano-sized particles in Zn matrix and Mn–Zn composite films significantly improved the corrosion resistance of PED thin films. <![CDATA[ <p>The MnO–Zn thin films were fabricated by radio frequency (RF) magnetron sputtering and compared with pulse electrodeposition (PED) Zn thin films, doped with MnO and ZrO nanoparticles. Surface morphology, structural properties, chemical composition and corrosion resistance of these coatings were investigated by using scanning electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, 3-D scanning interferometry and environmental chamber. Surface morphology and degree of crystallinity have different behaviours for different deposition methods. Pulse-coated films have polycrystalline structure with high surface roughness (Ra), whereas sputtered films are monocrys­talline with reduced roughness (Ra). Corrosion tests of both RF sputter and PED films revealed that the distribution of corrosion products formed on the surface of sputter films were not severe in extent as in case of electrodeposited coatings. Results showed that the doping of ZrO nano-sized particles in Zn matrix and Mn–Zn composite films significantly improved the corrosion resistance of PED thin films.</p> ]]> Fabrication And Characterization of Electrodeposited and Magnetron-Sputtered Thin Films z.a. khan p. pashaei r.s. bajwa m.h. nazir m. cakmak doi: 10.2495/CMEM-V3-N2-165-174 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 165 10.2495/CMEM-V3-N2-165-174 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-165-174 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-150-164 To describe and predict wear in a tribosystem, theoretical wear formulas and empirical models exist. Most of the existing formulations have a short range of validity and can only be applied for a specific contact situation. In this paper, the aim is to investigate a specific technical application of a tribocontact in an internal combustion engine. In particular, the contact between a piston skirt and a cylinder liner is experimentally simulated using a linear reciprocating tribometer and original engine parts, under close-to-reality loading conditions. The experimental findings will be analysed with a wear model that is most applicable to the actual tribosystem. This wear model, which is based on a combination of energy theories and a molecular mechanics approach, will be extended in the paper in order to add surface topography relevant parameters. The modified wear model is capable of combining the prediction of wear volume loss with the theory of fatigue and can be applied to any kind of tribosystems suffering damage due to reciprocating relative motion. For comparison with classical wear models, an empiri­cal power law – including Archard as a special case – is shown. Using the measurement results of the tribometer, the parameters that are specific to the aforementioned wear model are determined. Further­more, the applicability of the used model to describe the wear processes in this specific tribosystem will be discussed. <![CDATA[ <p>To describe and predict wear in a tribosystem, theoretical wear formulas and empirical models exist. Most of the existing formulations have a short range of validity and can only be applied for a specific contact situation. In this paper, the aim is to investigate a specific technical application of a tribocontact in an internal combustion engine. In particular, the contact between a piston skirt and a cylinder liner is experimentally simulated using a linear reciprocating tribometer and original engine parts, under close-to-reality loading conditions. The experimental findings will be analysed with a wear model that is most applicable to the actual tribosystem. This wear model, which is based on a combination of energy theories and a molecular mechanics approach, will be extended in the paper in order to add surface topography relevant parameters. The modified wear model is capable of combining the prediction of wear volume loss with the theory of fatigue and can be applied to any kind of tribosystems suffering damage due to reciprocating relative motion. For comparison with classical wear models, an empiri­cal power law – including Archard as a special case – is shown. Using the measurement results of the tribometer, the parameters that are specific to the aforementioned wear model are determined. Further­more, the applicability of the used model to describe the wear processes in this specific tribosystem will be discussed.</p> ]]> A Modified Energy-Based Model for Describing Wear Processes Applied to an Internal Combustion Engine j. sequard-base c. lenauer v. lazarev k. gavrilov a. doikin g. vorlaufer doi: 10.2495/CMEM-V3-N2-150-164 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 150 10.2495/CMEM-V3-N2-150-164 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-150-164 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-139-149 Bolted space frames are usually used to allow easy assembly and disassembly, as well as replacing defective components. Although the performance of bolted space frame structures under static loads is well understood, research on the shock propagation through these frames is limited. The focus of this study is to understand shock propagation through space frames, which is a critical factor when assessing the functionality of these frames. In this research, a lab-scale space frame structure, comprising hollow square members that are connected together through bolted joints is constructed. Non-destructive impact testing is carried out on this structure and the resulting acceleration signals at various locations are recorded. The objective of this work is to develop a finite element (FE) modeling approach that can reasonably replicate experimental results. <![CDATA[ <p>Bolted space frames are usually used to allow easy assembly and disassembly, as well as replacing defective components. Although the performance of bolted space frame structures under static loads is well understood, research on the shock propagation through these frames is limited. The focus of this study is to understand shock propagation through space frames, which is a critical factor when assessing the functionality of these frames. In this research, a lab-scale space frame structure, comprising hollow square members that are connected together through bolted joints is constructed. Non-destructive impact testing is carried out on this structure and the resulting acceleration signals at various locations are recorded. The objective of this work is to develop a finite element (FE) modeling approach that can reasonably replicate experimental results.</p> ]]> Computational Prediction of Low Impact Shock Propagation in a Lab-scale Space Bolted Frame Structure j. thota m.b. trabia b.j. o’toole doi: 10.2495/CMEM-V3-N2-139-149 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 139 10.2495/CMEM-V3-N2-139-149 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-139-149 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-121-138 <![CDATA[ ]]> Experimental and Numerical Investigations of Glass Curtain Walls Subjected to Low-level Blast Loads adam d. ralston david. c. weggel matthew j. whelan hongbing fang doi: 10.2495/CMEM-V3-N2-121-138 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 121 10.2495/CMEM-V3-N2-121-138 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-121-138 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-101-120 This paper presents a proposed methodology for applying statistical techniques as the basis for validation activities of a computer model of heat transfer. To demonstrate this approach, a case study of a Ruggedized Instrumentation Package subject to heating from battery discharge and electrical resistance during normal operations is considered. First, the uncertainty in the simulation due to the discretization of the governing partial differential equations is quantified. This error is analogous to the measurement error in an experiment in that it is not representative of actual physical variation, and is necessary to completely characterize the range of simulation outcomes. Secondly, physical uncertainties, such as unknown or variable material properties, are incorporated into the model and propagated through it. To this end, a sensitivity study enables exploration of the output space of the model. Experiments are considered to be a realization of one of these possible outcomes, with the added complication of containing physical processes not included in the model. Statistical tests are proposed to quantitatively compare experimental measurements and simulation results. The problem of discrepancies between the computational model and tests is considered as well. <![CDATA[ <p>This paper presents a proposed methodology for applying statistical techniques as the basis for validation activities of a computer model of heat transfer. To demonstrate this approach, a case study of a Ruggedized Instrumentation Package subject to heating from battery discharge and electrical resistance during normal operations is considered. First, the uncertainty in the simulation due to the discretization of the governing partial differential equations is quantified. This error is analogous to the measurement error in an experiment in that it is not representative of actual physical variation, and is necessary to completely characterize the range of simulation outcomes. Secondly, physical uncertainties, such as unknown or variable material properties, are incorporated into the model and propagated through it. To this end, a sensitivity study enables exploration of the output space of the model. Experiments are considered to be a realization of one of these possible outcomes, with the added complication of containing physical processes not included in the model. Statistical tests are proposed to quantitatively compare experimental measurements and simulation results. The problem of discrepancies between the computational model and tests is considered as well.</p> ]]> Statistical Validation for Heat Transfer Problems: A Case Study s.n. scott j.a. templeton p.d. hough j.r. ruthruff m.v. rosario j.p. peterson doi: 10.2495/CMEM-V3-N2-101-120 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 2 Article 101 10.2495/CMEM-V3-N2-101-120 https://www.acadlore.com/article/IJCMEM/2015_3_2/CMEM-V3-N2-101-120 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-7-12 Norway’s oil industry is shifting attention toward the north, to the Barents Sea. This means it must adjust to temperatures down to −30°C, storms, sleet, and snow, and possibly to drift-ice in the case of operations toward the north and east of these seas. Furthermore, operations during winter time will be carried out in the blackest night as the sun is away for several weeks. We have some information about the climate; however, compared with our expertise from the southern Norwegian continental shelf, we know little about how to run an offshore production installation in a cold climate. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Norway’s oil industry is shifting attention toward the north, to the Barents Sea. This means it must adjust to temperatures down to −30°C, storms, sleet, and snow, and possibly to drift-ice in the case of operations toward the north and east of these seas. Furthermore, operations during winter time will be carried out in the blackest night as the sun is away for several weeks. We have some information about the climate; however, compared with our expertise from the southern Norwegian continental shelf, we know little about how to run an offshore production installation in a cold climate.</span></p> ]]> Oil and Gas Operations Under Extreme Conditions in the Cold North o.t. gudmestad t. markeset doi: 10.2495/CMEM-V3-N1-7-12 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 7 10.2495/CMEM-V3-N1-7-12 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-7-12 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-49-64 The design of closed-loop structural control systems necessitates a certain level of robustness to cope with system uncertainties. Neurocontrollers, a type of adaptive control system, have been proposed to cope with those uncertainties. However, the performance of neural networks can be substantially influenced by the choice of the input space, or the hyperspace in which the representation lies. For instance, input selection may influence computation time, adaptation speed, effects of the curse of dimensionality, understanding of the representation, and model complexity. Input space selection is often overlooked in literature, and inputs are traditionally determined offline for an optimized performance of the neurocontroller. Such offline input selection is often unrealistic to conduct in the case of civil structures. In this paper, a novel method for automating the input selection process for neural networks is presented. The method is purposefully designed for online input selection during adaptive identification and control of nonlinear systems. Input selection is conducted online and sequentially, while the excitation is occurring. The algorithm designed for the adaptive input space assumes local quasi-stationarity of the time series, and embeds local maps sequentially in a delay vector using the embedding theorem. The input space of the representation is subsequently updated. The performance of the proposed dynamic input selection method is demonstrated through simulating semi-active control of an existing structure located in Boston, MA, U.S.A. Simulation results show the substantial performance of the proposed algorithm over traditional fixed-inputs strategies. <![CDATA[ <p>The design of closed-loop structural control systems necessitates a certain level of robustness to cope with system uncertainties. Neurocontrollers, a type of adaptive control system, have been proposed to cope with those uncertainties. However, the performance of neural networks can be substantially influenced by the choice of the input space, or the hyperspace in which the representation lies. For instance, input selection may influence computation time, adaptation speed, effects of the curse of dimensionality, understanding of the representation, and model complexity. Input space selection is often overlooked in literature, and inputs are traditionally determined offline for an optimized performance of the neurocontroller. Such offline input selection is often unrealistic to conduct in the case of civil structures. In this paper, a novel method for automating the input selection process for neural networks is presented. The method is purposefully designed for online input selection during adaptive identification and control of nonlinear systems. Input selection is conducted online and sequentially, while the excitation is occurring. The algorithm designed for the adaptive input space assumes local quasi-stationarity of the time series, and embeds local maps sequentially in a delay vector using the embedding theorem. The input space of the representation is subsequently updated. The performance of the proposed dynamic input selection method is demonstrated through simulating semi-active control of an existing structure located in Boston, MA, U.S.A. Simulation results show the substantial performance of the proposed algorithm over traditional fixed-inputs strategies.</p> ]]> Adaptive Structural Control Using Dynamic Hyperspace s. laflamme doi: 10.2495/CMEM-V3-N1-49-64 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 49 10.2495/CMEM-V3-N1-49-64 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-49-64 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-33-48 The paper presents the application of power series to the numerical solution of equilibrium problems in elasticity. Complete bases of power series that satisfy the differential equations are developed, first for unidimensional problems like the equilibrium of a beam on elastic foundation, second for the harmonic differential equation in two dimensions, with application to the Saint-Venant’s torsion problem and, finally, for the biharmonic equation, which can be applied to plane elasticity problems as well as to the plate-bending problem. In the case of unidimensional problems the solution is exact, because the number of boundary conditions is equal to the number of parameters involved in the series expansion, whereas in the two-dimensional problems the solution satisfies exactly the differential equation but only approximately the boundary conditions. The approximation of the solution will depend on the number of points selected at the boundary. The method presented here can also be used for developing high-order finite elements of any number of nodes and boundary shapes using complete polynomial expansions that satisfy the differential equation. Selected practical applications are shown. <![CDATA[ <p>The paper presents the application of power series to the numerical solution of equilibrium problems in elasticity. Complete bases of power series that satisfy the differential equations are developed, first for unidimensional problems like the equilibrium of a beam on elastic foundation, second for the harmonic differential equation in two dimensions, with application to the Saint-Venant’s torsion problem and, finally, for the biharmonic equation, which can be applied to plane elasticity problems as well as to the plate-bending problem. In the case of unidimensional problems the solution is exact, because the number of boundary conditions is equal to the number of parameters involved in the series expansion, whereas in the two-dimensional problems the solution satisfies exactly the differential equation but only approximately the boundary conditions. The approximation of the solution will depend on the number of points selected at the boundary. The method presented here can also be used for developing high-order finite elements of any number of nodes and boundary shapes using complete polynomial expansions that satisfy the differential equation. Selected practical applications are shown.</p> ]]> Solution of Solid Mechanic Equilibrium Problems by Power Series e. gonzález m. sarrazin doi: 10.2495/CMEM-V3-N1-33-48 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 33 10.2495/CMEM-V3-N1-33-48 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-33-48 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-21-32 This paper presents indicative results from the numerical investigation of two special issues of the seismic behaviour of base-isolated buildings, using custom-made software that utilizes modern object-oriented design approaches. The first issue concerns the modelling of the nonlinear behaviour of seismic isolation systems, focusing on the lead rubber bearings (LRBs), which are among the most commonly used seismic isolation systems. In particular, the inaccuracies between the actual behaviour of the LRBs, which can be more precisely represented by the Bouc–Wen model, and the usage of a bilinear inelastic model, which is often used in practice, are assessed through numerical simulations and parametric analyses. The second issue concerns potential pounding of base-isolated buildings with adjacent structures, when the available clearance around a seismically isolated building is limited, during very strong earthquakes. The consequences of potential pounding and the influence of certain parameters on the overall seismic response of base-isolated buildings are also assessed through numerical simulations and parametric analyses using custom-made software. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper presents indicative results from the numerical investigation of two special issues of the seismic behaviour of base-isolated buildings, using custom-made software that utilizes modern object-oriented design approaches. The first issue concerns the modelling of the nonlinear behaviour of seismic isolation systems, focusing on the lead rubber bearings (LRBs), which are among the most commonly used seismic isolation systems. In particular, the inaccuracies between the actual behaviour of the LRBs, which can be more precisely represented by the Bouc–Wen model, and the usage of a bilinear inelastic model, which is often used in practice, are assessed through numerical simulations and parametric analyses. The second issue concerns potential pounding of base-isolated buildings with adjacent structures, when the available clearance around a seismically isolated building is limited, during very strong earthquakes. The consequences of potential pounding and the influence of certain parameters on the overall seismic response of base-isolated buildings are also assessed through numerical simulations and parametric analyses using custom-made software.</span></p> ]]> Computer-Aided Investigation of Special Issues of the Response of Seismically Isolated Buildings e. mavronicola p. polycarpou l. papaloizou p. komodromos doi: 10.2495/CMEM-V3-N1-21-32 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 21 10.2495/CMEM-V3-N1-21-32 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-21-32 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-13-20 There have been many interesting technical ideas and parallels in thinking that have resulted from the technical discussions that I have had with Professor Jerome J. Connor since 1986. This brief article provides a context and reflects upon his mentorship, which helped shape the thinking of a then young professor from another University, and on the impact that Professor Connor has had on his students and others beyond the halls of MIT’s Building 1. The optimization topic presented here provides an example of that influence. Extracting the desired response information from an instrumented slender structure, while minimizing the number of sensors, is a challenging problem requiring well-defined objectives that can be used in an optimization process. In this study, a methodology that builds upon a Genetic Algorithm optimization procedure is used to investigate sensor placement needed to recover specific vibration modes. Data recorded from an experiment investigating the flow-induced vibration of a smooth horizontally towed cylinder is used to explore the optimization process and subtleties associated with its application subject to single or multiple objectives and gaps in sensor data due to several possible constraints. The use of the Paterno Front Method and the difficulty in accurately capturing higher modes are addressed. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">There have been many interesting technical ideas and parallels in thinking that have resulted from the technical discussions that I have had with Professor Jerome J. Connor since 1986. This brief article provides a context and reflects upon his mentorship, which helped shape the thinking of a then young professor from another University, and on the impact that Professor Connor has had on his students and others beyond the halls of MIT’s Building 1. The optimization topic presented here provides an example of that influence. Extracting the desired response information from an instrumented slender structure, while minimizing the number of sensors, is a challenging problem requiring well-defined objectives that can be used in an optimization process. In this study, a methodology that builds upon a Genetic Algorithm optimization procedure is used to investigate sensor placement needed to recover specific vibration modes. Data recorded from an experiment investigating the flow-induced vibration of a smooth horizontally towed cylinder is used to explore the optimization process and subtleties associated with its application subject to single or multiple objectives and gaps in sensor data due to several possible constraints. The use of the Paterno Front Method and the difficulty in accurately capturing higher modes are addressed.</span></p> ]]> Sensor Placement on Slender Structural Systems j. m. niedzwecki s. m. fang doi: 10.2495/CMEM-V3-N1-13-20 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 13 10.2495/CMEM-V3-N1-13-20 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-13-20 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-1-6 The contents of this paper reflect work that was conducted in the early 1960s in preparation of class notes for a graduate course on Elastic Stability taught in the Civil Engineering Department of MIT. This material is now well known and the presentation is not submitted as a new or original contribution but rather as a reflection of some work done that is related to the teachings of Professor Jerry Connor when he started at MIT. It is intended as an example of Jerry's impact since his early years on generations of students and young colleagues and an acknowledgement of our debt to him. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The contents of this paper reflect work that was conducted in the early 1960s in preparation of class notes for a graduate course on Elastic Stability taught in the Civil Engineering Department of MIT. This material is now well known and the presentation is not submitted as a new or original contribution but rather as a reflection of some work done that is related to the teachings of Professor Jerry Connor when he started at MIT. It is intended as an example of Jerry's impact since his early years on generations of students and young colleagues and an acknowledgement of our debt to him.</span></p> ]]> Elastic Stability of 3D Ideal Trusses j.m. roesset doi: 10.2495/CMEM-V3-N1-1-6 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 1 10.2495/CMEM-V3-N1-1-6 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-1-6 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-0 This Special Issue contains some of the papers presented at MIT to pay tribute to Professor Jerry Connor of its Civil Engineering Department on the occasion of his retirement after 60 years there. The event was fully reported in Volume 2, Number 4 of this Journal.The occasion brought together a number of academics and professionals who were profoundly influenced by Jerry's knowledge and personality, whose support was decisive for starting their careers off on the right track, my own included.In my case, my association with Jerry helped me to clarify and extend the finite element concepts and integral equations mathematical tools that gave rise to the Boundary Element Method.Professor Herbert Einstein, one of his colleagues at MIT, commented on Jerry's ability to always be ahead of what needs to be solved. He introduced a series of major innovations in research and teaching of Civil Engineering, always keeping in mind the professional relevance of whatever he was teaching. Herbert was grateful to Jerry for his help in reaching tenure at MIT and for his many illuminating discussions. He concluded by describing his contribution in engineering. Jerry, Herbert said, is an engineer's engineer!Professor Jose Roesset, author of one of the papers in this issue, remembers Jerry's teaching as a breath of fresh air, managing to simplify the most difficult of problems to their fundamentals and applying simple concepts. Jerry, Jose said, is foremost a teacher and a true scholar.Jerry's influence on Ove Gudmestad, author of another paper in this issue, was decisive in shaping his career in the offshore oil industry. Some topics of Ove's research, including the development of arctic engineering and earthquake effects, arose out of his collaboration with Jerry. More importantly perhaps was the fact that Jerry impressed on Ove the need to carry out research work thoroughly and as a team member.John Niedzwecki, now Professor at Texas A\&M, related how he started work on artificial intelligence under Jerry's guidance. This resulted in John's innovative research on offshore structures instrumentation tools.Petros Komodromos, now at the University of Cyprus, expressed his appreciation to Jerry for his support during his PhD thesis. He is author of the paper on the Response of Seismically isolated Buildings, a topic he has fully developed in several publications, including a book.Mauricio Sarrazin, Head of his own Consulting firm and Professor at the University of Chile, referred also to the importance of Jerry in the development of his own career. His paper on the solution of non linear equilibrium problems refers to research also influenced by Jerry.The last of the papers in this issue is by Professor Simon Laflamme of Iowa State University. On coming to MIT, he was impressed by the way Jerry interacted with his students, particularly those in the Master of Engineering programme which he created and which, every year, included a trip abroad at the end to visit outstanding engineering works.Jerry's input has had a great impact on several generations of researchers, changing their lives, including my own. A secret of his success has been his ability to listen and respect the opinions of all his colleagues and students. Jerry maintained that students should be treated as equals, instilling in them the confidence that they would require in their future professional lives, just one of the many reasons why so may of us feel indebted to Jerry.Professor Carlos A BrebbiaWessex Institute of Technology, UK <![CDATA[ <p>This Special Issue contains some of the papers presented at MIT to pay tribute to Professor Jerry Connor of its Civil Engineering Department on the occasion of his retirement after 60 years there. The event was fully reported in Volume 2, Number 4 of this Journal.</p><p style="text-align: justify">The occasion brought together a number of academics and professionals who were profoundly influenced by Jerry's knowledge and personality, whose support was decisive for starting their careers off on the right track, my own included.</p><p style="text-align: justify">In my case, my association with Jerry helped me to clarify and extend the finite element concepts and integral equations mathematical tools that gave rise to the Boundary Element Method.</p><p style="text-align: justify">Professor Herbert Einstein, one of his colleagues at MIT, commented on Jerry's ability to always be ahead of what needs to be solved. He introduced a series of major innovations in research and teaching of Civil Engineering, always keeping in mind the professional relevance of whatever he was teaching. Herbert was grateful to Jerry for his help in reaching tenure at MIT and for his many illuminating discussions. He concluded by describing his contribution in engineering. Jerry, Herbert said, is an engineer's engineer!</p><p style="text-align: justify">Professor Jose Roesset, author of one of the papers in this issue, remembers Jerry's teaching as a breath of fresh air, managing to simplify the most difficult of problems to their fundamentals and applying simple concepts. Jerry, Jose said, is foremost a teacher and a true scholar.</p><p style="text-align: justify">Jerry's influence on Ove Gudmestad, author of another paper in this issue, was decisive in shaping his career in the offshore oil industry. Some topics of Ove's research, including the development of arctic engineering and earthquake effects, arose out of his collaboration with Jerry. More importantly perhaps was the fact that Jerry impressed on Ove the need to carry out research work thoroughly and as a team member.</p><p style="text-align: justify">John Niedzwecki, now Professor at Texas A\&M, related how he started work on artificial intelligence under Jerry's guidance. This resulted in John's innovative research on offshore structures instrumentation tools.</p><p style="text-align: justify">Petros Komodromos, now at the University of Cyprus, expressed his appreciation to Jerry for his support during his <span style="font-family: MathJax_Main">PhD</span> thesis. He is author of the paper on the Response of Seismically isolated Buildings, a topic he has fully developed in several publications, including a book.</p><p style="text-align: justify">Mauricio Sarrazin, Head of his own Consulting firm and Professor at the University of Chile, referred also to the importance of Jerry in the development of his own career. His paper on the solution of non linear equilibrium problems refers to research also influenced by Jerry.</p><p style="text-align: justify">The last of the papers in this issue is by Professor Simon Laflamme of Iowa State University. On coming to MIT, he was impressed by the way Jerry interacted with his students, particularly those in the Master of Engineering programme which he created and which, every year, included a trip abroad at the end to visit outstanding engineering works.</p><p style="text-align: justify">Jerry's input has had a great impact on several generations of researchers, changing their lives, including my own. A secret of his success has been his ability to listen and respect the opinions of all his colleagues and students. Jerry maintained that students should be treated as equals, instilling in them the confidence that they would require in their future professional lives, just one of the many reasons why so may of us feel indebted to Jerry.</p><p style="text-align: justify"><em>Professor Carlos A Brebbia</em></p><p><em>Wessex Institute of Technology, UK</em></p> ]]> Tribute To Jerry Connor on His Retirement carlos a. brebbia doi: 10.2495/CMEM-V3-N1-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2015 3 1 Article 0 10.2495/CMEM-V3-N1-0 https://www.acadlore.com/article/IJCMEM/2015_3_1/CMEM-V3-N1-0 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-403-419 A practical approach is proposed and used to investigate the electromagnetic (EM) signature of bare- faced terrain using 3D computer electromagnetic models (CEM). Six barefaced terrain types with different electrical, physical and chemical properties were investigated. They comprise homogeneous and heterogeneous terrain. The approach developed CEMs in software using reflectance spectroscopy and dielectric permittivity data. EM signature models of the barefaced terrain are based on finite inte- gration technique (FIT) solvers. The developed technique and models are valid for diverse materials under test including unconventional petroleum resources like shale rock and oil sands. The remote sensing of terrain from airborne or satellite synthetic aperture radar requires a prior determination of the EM signature for accurate classification. The implementation of our new method combined empirical measurements and FIT in three steps. Geochemical properties determined using reflectance spectros- copy in the mid-infrared region (2.5–25 µm) identified the presence of bitumen, clay and moisture in Nigerian oil sands while reststrahlen effects were observed in beach sand compared with gravel and pebble. Also new information on both real, e′r and imaginary, e′r permittivity of terrain was experimentally obtained for frequency varying from 1 to 11 GHz. After post-processing, the results differed from expectation of complex refractive index method for petrophysics although adequate Kramers–Krönig correlation between measured real, e′r and imaginary, e′r permittivity data was exhibited. Our approach uses the results to improve the CEMs for superior EM signature determination. An application of our new technique to land degradation monitoring using radar is also presented. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A practical approach is proposed and used to investigate the electromagnetic (EM) signature of bare- faced terrain using 3D computer electromagnetic models (CEM). Six barefaced terrain types with different electrical, physical and chemical properties were investigated. They comprise homogeneous and heterogeneous terrain. The approach developed CEMs in software using reflectance spectroscopy and dielectric permittivity data. EM signature models of the barefaced terrain are based on finite inte- gration technique (FIT) solvers. The developed technique and models are valid for diverse materials under test including unconventional petroleum resources like shale rock and oil sands. The remote sensing of terrain from airborne or satellite synthetic aperture radar requires a prior determination of the EM signature for accurate classification. The implementation of our new method combined empirical measurements and FIT in three steps. Geochemical properties determined using reflectance spectros- copy in the mid-infrared region (2.5–25 µm) identified the presence of bitumen, clay and moisture in Nigerian oil sands while reststrahlen effects were observed in beach sand compared with gravel and pebble. Also new information on both real, </span><em>e</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">′</span><em>r </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">and imaginary, </span><em>e</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">′</span><em>r </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">permittivity of terrain was experimentally obtained for frequency varying from 1 to 11 GHz. After post-processing, the results differed from expectation of complex refractive index method for petrophysics although adequate Kramers–Krönig correlation between measured real, </span><em>e</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">′</span><em>r </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">and imaginary, </span><em>e</em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">′</span><em>r </em><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">permittivity data was exhibited. Our approach uses the results to improve the CEMs for superior EM signature determination. An application of our new technique to land degradation monitoring using radar is also presented.</span></p> ]]> A Practical Approach for Modelling the Electromagnetic Radar Signature of Barefaced Terrain for Remote Sensing m. ezeoke k. tong s. shi doi: 10.2495/CMEM-V2-N4-403-419 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 403 10.2495/CMEM-V2-N4-403-419 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-403-419 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-392-402 This paper presents a computational and experimental study of a valveless pump driven by a noble piezoelectric composite actuator consisting of a bimorph piezoelectric plate and a metal cap. The superiority of deformation performance of the proposed composite actuator was demonstrated computationally through finite element simulation and was then verified experimentally by deflection measurements of a disc-shaped prototype under an alternating electric field. The proposed composite actuator was applied to a valveless pump in a Y-shaped fluid channel. The pump’s performance was estimated using a piezoelectric-fluid interaction finite element simulation. The effect of the fluid channel configuration was investigated, and the liquid feed volume is discussed and compared with that of conventional actuators. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This paper presents a computational and experimental study of a valveless pump driven by a noble piezoelectric composite actuator consisting of a bimorph piezoelectric plate and a metal cap. The superiority of deformation performance of the proposed composite actuator was demonstrated computationally through finite element simulation and was then verified experimentally by deflection measurements of a disc-shaped prototype under an alternating electric field. The proposed composite actuator was applied to a valveless pump in a Y-shaped fluid channel. The pump’s performance was estimated using a piezoelectric-fluid interaction finite element simulation. The effect of the fluid channel configuration was investigated, and the liquid feed volume is discussed and compared with that of conventional actuators.</span></p> ]]> Performance Enhancement of a Valveless Pump Driven by a Noble Piezoelectric Composite Actuator y. uetsuji t. hiramori n. nishiguchi h. kuramae k. tsuchiya doi: 10.2495/CMEM-V2-N4-392-402 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 392 10.2495/CMEM-V2-N4-392-402 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-392-402 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-374-391 Hydrodynamic slug flow is the commonest flow regime observed in high viscosity liquid–gas horizontal pipelines over a wide range of different flow conditions. Hydrodynamic slugging tends to generate large vibrations that may impose structural instability or even damage oil production pipelines. For that reason, there is a need to investigate high viscosity slug flow regime to understand its complex characteristics. This is pertinent when considering that existing slug flow models used in the petroleum industry to design production pipelines are not suitable for predicting the behaviour of high viscosity oil–gas flow. In this study, the effects of liquid viscosity and flow variables on slug flow regime were investigated experimentally through the analysis of two key parameters—slug frequency and slug body liquid holdup, both measured with a gamma densitometer. Comparison of the measured slug parameters to existing correlations revealed that slug body liquid holdup correlations were in close agreement with high viscosity experimental data. However, none of the existing slug frequency correlations used was able to produce accurate predictions. A new empirical correlation for slug frequency was proposed. Compared with existing correlations, the newly proposed correlation performed much better in predict- ing slug frequency of high viscosity liquid–gas flows. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Hydrodynamic slug flow is the commonest flow regime observed in high viscosity liquid–gas horizontal pipelines over a wide range of different flow conditions. Hydrodynamic slugging tends to generate large vibrations that may impose structural instability or even damage oil production pipelines. For that reason, there is a need to investigate high viscosity slug flow regime to understand its complex characteristics. This is pertinent when considering that existing slug flow models used in the petroleum industry to design production pipelines are not suitable for predicting the behaviour of high viscosity oil–gas flow. In this study, the effects of liquid viscosity and flow variables on slug flow regime were investigated experimentally through the analysis of two key parameters—slug frequency and slug body liquid holdup, both measured with a gamma densitometer. Comparison of the measured slug parameters to existing correlations revealed that slug body liquid holdup correlations were in close agreement with high viscosity experimental data. However, none of the existing slug frequency correlations used was able to produce accurate predictions. A new empirical correlation for slug frequency was proposed. Compared with existing correlations, the newly proposed correlation performed much better in predict- ing slug frequency of high viscosity liquid–gas flows.</span></p> ]]> Evaluating the Effects of High Liquid Viscosity and Flow Variables on Horizontal Oil–Gas Slug Flows by Gamma Radiation Method c.n. okezue doi: 10.2495/CMEM-V2-N4-374-391 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 374 10.2495/CMEM-V2-N4-374-391 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-374-391 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-362-373 Particle size reduction of dry granular material by mechanical means, also known as milling or comminution, is undoubtedly a very important unit operation in pharmaceutical, agricultural, food, mineral and paper industries. As comminution is a stochastic and a nonlinear process, an attempt was made to understand this complicated process by conducting parametric studies experimentally and computationally using discrete element method (DEM). Greater size reduction was observed at higher rotational speed of the hammer owing to the greater centrifugal force experienced by the particles. Increase in impeller wall tolerance resulted in rolling mode regime of powder bed, which was found to be significant at low impeller speeds. A numerical model based on DEM was used to simulate a hammer mill and study the breakage and kinematics of the particle motion within the hammer mill. In the simulations, increase in hammer tip speed causes higher frequency of impact of particles per unit time and higher specific energy of impact resulting in generation of much finer end product. A limit can be conceived during the breakage event. This is because as size reduction occurs, the breakage rates can fall for very fine particles as crack propagation ceases. This is because as size decreases the probability of finding a flaw also decreases. Simulations also showed a higher milling rate for big hammers as larger hammers decrease the tolerance between the milling chamber and rotating impeller. To study the effect of material properties, the energy of fragmentation was estimated and it was found to increase as the material became more cohesive. <![CDATA[ <p>Particle size reduction of dry granular material by mechanical means, also known as milling or comminution, is undoubtedly a very important unit operation in pharmaceutical, agricultural, food, mineral and paper industries. As comminution is a stochastic and a nonlinear process, an attempt was made to understand this complicated process by conducting parametric studies experimentally and computationally using discrete element method (DEM). Greater size reduction was observed at higher rotational speed of the hammer owing to the greater centrifugal force experienced by the particles. Increase in impeller wall tolerance resulted in rolling mode regime of powder bed, which was found to be significant at low impeller speeds. A numerical model based on DEM was used to simulate a hammer mill and study the breakage and kinematics of the particle motion within the hammer mill. In the simulations, increase in hammer tip speed causes higher frequency of impact of particles per unit time and higher specific energy of impact resulting in generation of much finer end product. A limit can be conceived during the breakage event. This is because as size reduction occurs, the breakage rates can fall for very fine particles as crack propagation ceases. This is because as size decreases the probability of finding a flaw also decreases. Simulations also showed a higher milling rate for big hammers as larger hammers decrease the tolerance between the milling chamber and rotating impeller. To study the effect of material properties, the energy of fragmentation was estimated and it was found to increase as the material became more cohesive.</p> ]]> Experiment and Model-Based Investigation of Comminution in a Hammer Mill s. naik y. feng b. chaudhuri doi: 10.2495/CMEM-V2-N4-362-373 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 362 10.2495/CMEM-V2-N4-362-373 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-362-373 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-346-361 Contrary to military or essential government buildings, most bridges are designed without any consideration for blast resistance. Fiber-reinforced polymers (FRPs) can provide an effective means for strengthening of critical bridges against such loading. This study has focused on the effectiveness of FRP retrofitting in the dynamic response of reinforced concrete bridge columns under blast loading. Using a simplified equivalent I-section with a virtual material lumped at the two flanges; a lightly meshed uniaxial finite element model was developed and successfully validated against previous studies. The proposed model was then used for a thorough parametric study on the blast resistance of bridge substructures in the form of a single-column, two-column pier frame, and an entire bridge. The study showed the benefits of strengthening with composites against blast loading. The FRP tensile strength and diameter-to-thickness ratio, steel reinforcement ratio, and column length and damping ratio significantly affect the blast resistance of an FRP-retrofitted bridge. Finally, based on the parametric study results, predictive equations with multiple linear regression and high order terms were developed statistically for the FRP retrofit design of single columns against blast loading. <![CDATA[ <p>Contrary to military or essential government buildings, most bridges are designed without any consideration for blast resistance. Fiber-reinforced polymers (FRPs) can provide an effective means for strengthening of critical bridges against such loading. This study has focused on the effectiveness of FRP retrofitting in the dynamic response of reinforced concrete bridge columns under blast loading. Using a simplified equivalent I-section with a virtual material lumped at the two flanges; a lightly meshed uniaxial finite element model was developed and successfully validated against previous studies. The proposed model was then used for a thorough parametric study on the blast resistance of bridge substructures in the form of a single-column, two-column pier frame, and an entire bridge. The study showed the benefits of strengthening with composites against blast loading. The FRP tensile strength and diameter-to-thickness ratio, steel reinforcement ratio, and column length and damping ratio significantly affect the blast resistance of an FRP-retrofitted bridge. Finally, based on the parametric study results, predictive equations with multiple linear regression and high order terms were developed statistically for the FRP retrofit design of single columns against blast loading.</p> ]]> Performance of FRP-Retrofitted Concrete Bridge Columns Under Blast Loading r. zheng p. zohrevand h. erdogan a. mirmiran doi: 10.2495/CMEM-V2-N4-346-361 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 346 10.2495/CMEM-V2-N4-346-361 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-346-361 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-331-345 An isothermal and non-isothermal numerical study of effusion cooling flow and heat transfer is conducted using a Reynolds-averaged Navier–Stokes (RANS) approach. A Reynolds stress transport (RST) turbulence model is used to predict the flow field of a staggered array of 12 rows of effusion holes, each hole inclined at 30° to the flat plate. The Reynolds number based on the hole diameter and jet exit velocity is 3800. The blowing ratio in both studies is 5. A conjugate heat transfer approach is adopted in the non-isothermal simulation. For the isothermal case, the RST model is shown to be capable of predicting the injection, penetration, downstream decay and lateral mixing of the effusion jets reasonably well. In addition, the numerical model captures the existence of two counter-rotating vortices emanating from each hole, which causes the entrainment of combustor flow towards the surface of the plate at the leading edge and downstream, influences the mixing of accumulated coolant flow, providing a more uniform surface temperature across the plate. The presence and characteristics of these vortices are in good agreement with previously published research. In the non-isothermal case, the laterally averaged cooling effectiveness across the plate is under-predicted but the trend conforms to that exhibited during experimentation. <![CDATA[ <p>An isothermal and non-isothermal numerical study of effusion cooling flow and heat transfer is conducted using a Reynolds-averaged Navier–Stokes (RANS) approach. A Reynolds stress transport (RST) turbulence model is used to predict the flow field of a staggered array of 12 rows of effusion holes, each hole inclined at 30° to the flat plate. The Reynolds number based on the hole diameter and jet exit velocity is 3800. The blowing ratio in both studies is 5. A conjugate heat transfer approach is adopted in the non-isothermal simulation. For the isothermal case, the RST model is shown to be capable of predicting the injection, penetration, downstream decay and lateral mixing of the effusion jets reasonably well. In addition, the numerical model captures the existence of two counter-rotating vortices emanating from each hole, which causes the entrainment of combustor flow towards the surface of the plate at the leading edge and downstream, influences the mixing of accumulated coolant flow, providing a more uniform surface temperature across the plate. The presence and characteristics of these vortices are in good agreement with previously published research. In the non-isothermal case, the laterally averaged cooling effectiveness across the plate is under-predicted but the trend conforms to that exhibited during experimentation.</p> ]]> Numerical Study of Effusion Cooling Flow and Heat Transfer m. walton z. yang doi: 10.2495/CMEM-V2-N4-331-345 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 4 Article 331 10.2495/CMEM-V2-N4-331-345 https://www.acadlore.com/article/IJCMEM/2014_2_4/CMEM-V2-N4-331-345 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-313-322 A general model for flocs settling velocity is still an open field of research in the scientific literature. In this work, a reduced model of an aquaculture recirculation tank was used to validate a model for floc settling velocity. Cohesive sediments from non-used food and fish excreta are a main concern in those tanks design. Excess concentrations of sediments can cause fish death or additional costs of energy for aeration. This research is aimed to understand the settling behavior of flocs when subjected to a liquid shear rate. A reduced scale model of an aquaculture recirculation tank was build in Plexiglas in order to use particle image velocimetry and particle tracking velocimetry techniques to measure fluid velocities, solid settling velocities, flocs shape and size. Different flow rates and solid concentrations were used to develop varied configurations in the sys- tem; models for floc settling velocity based on fractal theory were calibrated. Cohesive sediments from fish food were observed in long-term experiments at constant fluid shear rate in the recirculation tank. A group of 50 images were obtained for every 5 min. Image analysis provided us with floc settling velocity data and floc size. Using floc settling velocity data, floc density was obtained for different diameters at equilibrium conditions, after 1 h or larger experiments. Statistical analysis of floc velocities for different floc sizes allowed us to obtain an expression for the drag coefficient as a function of floc particle Reynolds number (Rep). The results were compared with floc settling velocity results from different researchers. The model is able to define the general behavior of floc settling velocity, which shows a reduction for larger flocs that is not taken into account in classical models. Only two parameters of the drag coefficient model for a permeable spherical particle are needed to be calibrated, for different types of sediments, in order to have more general applicability. <![CDATA[ <p>A general model for flocs settling velocity is still an open field of research in the scientific literature. In this work, a reduced model of an aquaculture recirculation tank was used to validate a model for floc settling velocity. Cohesive sediments from non-used food and fish excreta are a main concern in those tanks design. Excess concentrations of sediments can cause fish death or additional costs of energy for aeration. This research is aimed to understand the settling behavior of flocs when subjected to a liquid shear rate. A reduced scale model of an aquaculture recirculation tank was build in Plexiglas in order to use particle image velocimetry and particle tracking velocimetry techniques to measure fluid velocities, solid settling velocities, flocs shape and size. Different flow rates and solid concentrations were used to develop varied configurations in the sys- tem; models for floc settling velocity based on fractal theory were calibrated. Cohesive sediments from fish food were observed in long-term experiments at constant fluid shear rate in the recirculation tank. A group of 50 images were obtained for every 5 min. Image analysis provided us with floc settling velocity data and floc size. Using floc settling velocity data, floc density was obtained for different diameters at equilibrium conditions, after 1 h or larger experiments. Statistical analysis of floc velocities for different floc sizes allowed us to obtain an expression for the drag coefficient as a function of floc particle Reynolds number (Rep). The results were compared with floc settling velocity results from different researchers. The model is able to define the general behavior of floc settling velocity, which shows a reduction for larger flocs that is not taken into account in classical models. Only two parameters of the drag coefficient model for a permeable spherical particle are needed to be calibrated, for different types of sediments, in order to have more general applicability.</p> ]]> A Model for the Settling Velocity of Flocs; Application to an Aquaculture Recirculation Tank j. a. garcia-aragon h. salinas-tapia j. moreno-guevara v. diaz-palomarez s. tejeda-vega doi: 10.2495/CMEM-V2-N3-313-322 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 313 10.2495/CMEM-V2-N3-313-322 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-313-322 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-298-312 Cavitation is a heavy threat for spillways with concrete chutes. Besides a proper design and execution, aeration is an effective means to avoid severe damages. A detailed study on bottom aerators of spillway chutes is presented here. Data from laboratory experiments were used to calibrate the coefficients of a physically based equation, which considers the effects of aerator geometry and different roughnesses of the surface of the aerator. After adjustment of scale factors, results computed by this equation showed a good agreement with observed data of different prototypes found in the literature. The main physical concepts of the developed equation are presented. The quantification of the air flow into the water jet was performed by separately considering the gas and liquid phases and using the subpressure under the jet of the aerator as a liaison between the two formulations. Consequently, this subpressure does not appear explicitly in the final formulation and does not need to be known for the quantification of the gas flow. The results show that the approach is suitable for the given problem. <![CDATA[ <p>Cavitation is a heavy threat for spillways with concrete chutes. Besides a proper design and execution, aeration is an effective means to avoid severe damages. A detailed study on bottom aerators of spillway chutes is presented here. Data from laboratory experiments were used to calibrate the coefficients of a physically based equation, which considers the effects of aerator geometry and different roughnesses of the surface of the aerator. After adjustment of scale factors, results computed by this equation showed a good agreement with observed data of different prototypes found in the literature. The main physical concepts of the developed equation are presented. The quantification of the air flow into the water jet was performed by separately considering the gas and liquid phases and using the subpressure under the jet of the aerator as a liaison between the two formulations. Consequently, this subpressure does not appear explicitly in the final formulation and does not need to be known for the quantification of the gas flow. The results show that the approach is suitable for the given problem.</p> ]]> Solution for Spillway Chute Aeration Through Bottom Aerators h. fuhrhop h. e. schulz h. wittenberg doi: 10.2495/CMEM-V2-N3-298-312 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 298 10.2495/CMEM-V2-N3-298-312 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-298-312 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-280-297 In this paper, the response characteristics of an offshore wind turbine (OWT) structure under breaking wave forces and wind forces are studied. A 3D numerical model, based on solving the viscous and incompressible Navier–Stokes equations and the volume of fluid method, is employed to estimate the breaking wave forces on an OWT structure (6.0-m diameter monopile). The calculated wave forces are then applied with the wind forces on the OWT structure modeled in the computer program HAWC2 to understand the nature of its response. The effects from the aerodynamic damping and the foundation flexibility on the structure’s response are also discussed. <![CDATA[ <p>In this paper, the response characteristics of an offshore wind turbine (OWT) structure under breaking wave forces and wind forces are studied. A 3D numerical model, based on solving the viscous and incompressible Navier–Stokes equations and the volume of fluid method, is employed to estimate the breaking wave forces on an OWT structure (6.0-m diameter monopile). The calculated wave forces are then applied with the wind forces on the OWT structure modeled in the computer program HAWC2 to understand the nature of its response. The effects from the aerodynamic damping and the foundation flexibility on the structure’s response are also discussed.</p> ]]> Dynamic Characteristics of an Offshore Wind Turbine with Breaking Wave and Wind Load s.j. choi a. sarkar doi: 10.2495/CMEM-V2-N3-280-297 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 280 10.2495/CMEM-V2-N3-280-297 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-280-297 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-269-279 The occurrence of calcium carbonate (CaCO3) efflorescence phenomenon is not new and is generally found in the form of unsightly white deposits on the surface of cement products. It appears just after completion of building construction and causes aesthetically unpleasant sight. This paper presents and discusses the results of microstructural study on the effectiveness of commercial polymer emulsion as cement additives to mitigate efflorescence on cement-based products that are dry-cured in the concrete laboratory at daily room temperature (T) and relative humidity in the range of 18°C–28°C and 65%–90%, respectively. Polymers used as cement additives were styrene acrylic ester (SAE) and styrene butadiene rubber (SBR) emulsion. Due to their pore-blocking characteristics and interaction with cement to improve mortar quality, they are added into cement to form mortar used for repair purposes. In order to investigate on how they can microstructurally influence efflorescence formation, efflorescence intensities (EI) in terms of percentages of CaCO3 resulting from the combination of puddle test and standard chemical method were compared systematically between all samples on 28, 60 and 90 days and the findings were discussed and corroborated physicochemically using initial surface absorption test, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and morphology using scanning electron microscopy (SEM). Results indicated that 10% and 5% SAE addition significantly reduced primary efflorescence and secondary efflorescence, respectively, in comparison to SBR and Control. The influence were on chemical reactivity, interaction between polymer and cement and on the movement of the polymer particles within the hydrating mortar as hydration progressed to form pore-blocking effects in the microstructures of cement-based materials and were reflected in the XRD patterns, TGA/DTG analysis, SEM images and the decreased initial surface water absorption. <![CDATA[ <p>The occurrence of calcium carbonate (CaCO3) efflorescence phenomenon is not new and is generally found in the form of unsightly white deposits on the surface of cement products. It appears just after completion of building construction and causes aesthetically unpleasant sight. This paper presents and discusses the results of microstructural study on the effectiveness of commercial polymer emulsion as cement additives to mitigate efflorescence on cement-based products that are dry-cured in the concrete laboratory at daily room temperature (T) and relative humidity in the range of 18°C–28°C and 65%–90%, respectively. Polymers used as cement additives were styrene acrylic ester (SAE) and styrene butadiene rubber (SBR) emulsion. Due to their pore-blocking characteristics and interaction with cement to improve mortar quality, they are added into cement to form mortar used for repair purposes. In order to investigate on how they can microstructurally influence efflorescence formation, efflorescence intensities (EI) in terms of percentages of CaCO3 resulting from the combination of puddle test and standard chemical method were compared systematically between all samples on 28, 60 and 90 days and the findings were discussed and corroborated physicochemically using initial surface absorption test, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and morphology using scanning electron microscopy (SEM). Results indicated that 10% and 5% SAE addition significantly reduced primary efflorescence and secondary efflorescence, respectively, in comparison to SBR and Control. The influence were on chemical reactivity, interaction between polymer and cement and on the movement of the polymer particles within the hydrating mortar as hydration progressed to form pore-blocking effects in the microstructures of cement-based materials and were reflected in the XRD patterns, TGA/DTG analysis, SEM images and the decreased initial surface water absorption.</p> ]]> Microstructural Study on the Effectiveness of Commercial Polymer Emulsion as Cement Additives to Mitigate Efflorescence n. mohamed sutan i. yakub s. hamdan z. a. talib doi: 10.2495/CMEM-V2-N3-269-279 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 269 10.2495/CMEM-V2-N3-269-279 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-269-279 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-255-268 The paper is focused on identification of micro-structural and mechanical alterations in porous matrices of Portland fly ash cement mortar, during frost deterioration. An attempt is made to assess the efficiency of superabsorbent polymer (SAP) ‘protection’ based on analysis of three SAP types with different water absorption/desorption capacities. Two different exposure regimes have been adopted in the study; the exposure to freeze/thaw cycles and the exposure to freeze/thaw with de-icing solution. In order to eval- uate the effect of SAPs on the micro-structural features of deteriorating mortars comprehensive MIP and SEM analyses were performed. It has been found that SAPs with high water absorption capacities may prevent flexural strength reduction caused by frost action. The limitation in micro-cracks propagation by SAP additions can be attributed to the higher tensile strength of ‘SAP pores’ walls, resulting from densification of CSH gel. This is consistent with the finding of higher ‘breaking pressure’ for ‘SAP pores’. Nevertheless, it was shown that the additional exposure to salt ions reduces the initial resistance to less than one month. Desorption characteristics of SAPs may play a particularly important role in the case of very early exposure to F/T cycles. Too slow release of water does not sufficiently facilitate densification of structure prior frost action. Neither can it create a suitable network of air pockets for the expansion of ice and freezing water as in air-entrainers. This is particularly relevant to fly ash cementitious composites due to delayed pozzolanic reaction. <![CDATA[ <p>The paper is focused on identification of micro-structural and mechanical alterations in porous matrices of Portland fly ash cement mortar, during frost deterioration. An attempt is made to assess the efficiency of superabsorbent polymer (SAP) ‘protection’ based on analysis of three SAP types with different water absorption/desorption capacities. Two different exposure regimes have been adopted in the study; the exposure to freeze/thaw cycles and the exposure to freeze/thaw with de-icing solution. In order to eval- uate the effect of SAPs on the micro-structural features of deteriorating mortars comprehensive MIP and SEM analyses were performed. It has been found that SAPs with high water absorption capacities may prevent flexural strength reduction caused by frost action. The limitation in micro-cracks propagation by SAP additions can be attributed to the higher tensile strength of ‘SAP pores’ walls, resulting from densification of CSH gel. This is consistent with the finding of higher ‘breaking pressure’ for ‘SAP pores’. Nevertheless, it was shown that the additional exposure to salt ions reduces the initial resistance to less than one month. Desorption characteristics of SAPs may play a particularly important role in the case of very early exposure to F/T cycles. Too slow release of water does not sufficiently facilitate densification of structure prior frost action. Neither can it create a suitable network of air pockets for the expansion of ice and freezing water as in air-entrainers. This is particularly relevant to fly ash cementitious composites due to delayed pozzolanic reaction.</p> ]]> The Effect of Superabsorbent Polymers on Performance of Fly Ash Cementitious Mortars Exposed to Accelerated Freezing/ Thawing Conditions karol s. sikora agnieszka j. klemm doi: 10.2495/CMEM-V2-N3-255-268 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 255 10.2495/CMEM-V2-N3-255-268 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-255-268 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-243-254 The effect of unidirectional surface roughness on the corrosion behaviour of nickel in 0.5 M H2SO4 solution was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The surfaces, both before and after corrosion, were characterized by scanning electron microscopy, profilometry for roughness and energy dispersive spectroscopy for oxygen content. The results were compared with those for patterned samples consisting of an array of holes. For the unidirectional surface roughness samples, an increase in roughness gave rise to an increase in corrosion rate, reflecting the decreased ability to form a stable passive film. The patterned samples showed a higher corrosion resistance, which is attributed to a different corrosion protection mechanism, namely heterogeneous wetting. <![CDATA[ <p>The effect of unidirectional surface roughness on the corrosion behaviour of nickel in 0.5 M H2SO4 solution was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The surfaces, both before and after corrosion, were characterized by scanning electron microscopy, profilometry for roughness and energy dispersive spectroscopy for oxygen content. The results were compared with those for patterned samples consisting of an array of holes. For the unidirectional surface roughness samples, an increase in roughness gave rise to an increase in corrosion rate, reflecting the decreased ability to form a stable passive film. The patterned samples showed a higher corrosion resistance, which is attributed to a different corrosion protection mechanism, namely heterogeneous wetting.</p> ]]> An Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization Study of the Effect of Unidirectional Roughness on the Corrosion of Nickel a. s. toloei v. stoilov d. o. northwood doi: 10.2495/CMEM-V2-N3-243-254 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 243 10.2495/CMEM-V2-N3-243-254 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-243-254 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-225-242 The development of predictive tools, such as finite element models, to calculate the response of structures subjected to vehicle-borne explosive loads has become increasingly important for the engineering and defence communities. Typically, the development of such methodologies is driven by conclusions that have been obtained via field tests; however, collecting data throughout such experiments can be problematic due to the harsh testing environment. Utilizing the University of California, San Diego Blast simulator, which can simulate explosive loads in a controlled laboratory setting, a series of experiments were conducted to investigate the performance of steel columns subjected to vehicle-borne threats and a computational model was created using the qualitative and quantitative findings from the experiments. This paper describes, in detail, the development and calibration of the finite element model, initially discussed in, created from 17 blast simulator experiments that were validated against field tests. The finite element analysis was performed with LS-DYNA, a three dimensional, explicit, Lagrangian finite element code that uses a central difference time integration method from Livermore Software Technology Corporation. The model incorporated constitutive models to represent material behaviors of interest, specifically those with strain rate effects. Loading of the column was modeled using a previously calibrated low-density foam model and smooth particle hydrodynamic elements, where appropriate. <![CDATA[ <p>The development of predictive tools, such as finite element models, to calculate the response of structures subjected to vehicle-borne explosive loads has become increasingly important for the engineering and defence communities. Typically, the development of such methodologies is driven by conclusions that have been obtained via field tests; however, collecting data throughout such experiments can be problematic due to the harsh testing environment. Utilizing the University of California, San Diego Blast simulator, which can simulate explosive loads in a controlled laboratory setting, a series of experiments were conducted to investigate the performance of steel columns subjected to vehicle-borne threats and a computational model was created using the qualitative and quantitative findings from the experiments. This paper describes, in detail, the development and calibration of the finite element model, initially discussed in, created from 17 blast simulator experiments that were validated against field tests. The finite element analysis was performed with LS-DYNA, a three dimensional, explicit, Lagrangian finite element code that uses a central difference time integration method from Livermore Software Technology Corporation. The model incorporated constitutive models to represent material behaviors of interest, specifically those with strain rate effects. Loading of the column was modeled using a previously calibrated low-density foam model and smooth particle hydrodynamic elements, where appropriate.</p> ]]> Computational Modeling of Steel Columns Subjected to Experimentally Simulated Blasts l. k. stewart doi: 10.2495/CMEM-V2-N3-225-242 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 3 Article 225 10.2495/CMEM-V2-N3-225-242 https://www.acadlore.com/article/IJCMEM/2014_2_3/CMEM-V2-N3-225-242 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-202-216 The inhomogeneous theory of elasticity considers bodies, the mechanical characteristics of which (the modulus of elasticity and Poisson’s ratio) are functions of the coordinates. If indirect problems of the inhomogeneous theory of elasticity are identified, and the stress-strain state of the body has well-known functions of mechanical characteristics, the essence of inverse problems is to determine the functions of the inhomogeneity for a given stress state of the body. One of the first solutions to such an inverse problem was published in the work of Lekhnitskii (“Radial distribution of stresses in the wedge and half-plane with variable modulus of elasticity”. PMM, XXVI(1), pp. 146–151, 1962). In this article, we consider one-dimensional inverse problems for thick-walled cylindrical and spherical shells that are subjected to internal and external pressures in a non-varying temperature field. The aim of this work is to identify the dependence of the elastic modulus on the radial co-ordinate for which the equivalent stress according to a particular theory of strength will be constant at all points of the body (such structures are called equal stress), or the equivalent stress in all points will be equal to the strength of the material (such structures are called equal strength). For example, the author has proven that the limit loads on resulting equal-strength inhomogeneous shells can be significantly increased. <![CDATA[ <p>The inhomogeneous theory of elasticity considers bodies, the mechanical characteristics of which (the modulus of elasticity and Poisson’s ratio) are functions of the coordinates. If indirect problems of the inhomogeneous theory of elasticity are identified, and the stress-strain state of the body has well-known functions of mechanical characteristics, the essence of inverse problems is to determine the functions of the inhomogeneity for a given stress state of the body. One of the first solutions to such an inverse problem was published in the work of Lekhnitskii (“Radial distribution of stresses in the wedge and half-plane with variable modulus of elasticity”. PMM, XXVI(1), pp. 146–151, 1962). In this article, we consider one-dimensional inverse problems for thick-walled cylindrical and spherical shells that are subjected to internal and external pressures in a non-varying temperature field. The aim of this work is to identify the dependence of the elastic modulus on the radial co-ordinate for which the equivalent stress according to a particular theory of strength will be constant at all points of the body (such structures are called equal stress), or the equivalent stress in all points will be equal to the strength of the material (such structures are called equal strength). For example, the author has proven that the limit loads on resulting equal-strength inhomogeneous shells can be significantly increased.</p> ]]> Inverse Problems of the Inhomogeneous Theory of Elasticity for Thick-Walled Shells v. andreev doi: 10.2495/CMEM-V2-N2-202-216 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 202 10.2495/CMEM-V2-N2-202-216 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-202-216 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-184-201 Municipal solid waste landfills are potential long-term sources of pollution for both humans and the environment and need to be managed properly both during their lifetime and after closure. This paper analyzes the influence of the Râureni-Râmnicu Vâlcea landfill (Romania) on the concentration of pollutant reaching the groundwater and the nearby Olt River. Prediction of contaminant concentration in groundwater is based on a simple mathematical model of solute transport. Model parameters are determined from field data and scale analysis. Despite its recent closure after 32 years of activity, this landfill has the potential to continue to pollute both the Olt River and the groundwater for decades. Sensitivity analyses are performed to determine the impact of varying the dispersivity coefficients on the resulting contaminant transport and distribution in the aquifer. Aquifer pollution is predicted for twenty years beyond the landfill closure. Enhanced landfill monitoring and establishment of a shared data portal for Romanian environmental data is highly recommended. <![CDATA[ <p>Municipal solid waste landfills are potential long-term sources of pollution for both humans and the environment and need to be managed properly both during their lifetime and after closure. This paper analyzes the influence of the Râureni-Râmnicu Vâlcea landfill (Romania) on the concentration of pollutant reaching the groundwater and the nearby Olt River. Prediction of contaminant concentration in groundwater is based on a simple mathematical model of solute transport. Model parameters are determined from field data and scale analysis. Despite its recent closure after 32 years of activity, this landfill has the potential to continue to pollute both the Olt River and the groundwater for decades. Sensitivity analyses are performed to determine the impact of varying the dispersivity coefficients on the resulting contaminant transport and distribution in the aquifer. Aquifer pollution is predicted for twenty years beyond the landfill closure. Enhanced landfill monitoring and establishment of a shared data portal for Romanian environmental data is highly recommended.</p> ]]> The Influence of a Municipal Solid Waste Landfill on Groundwater Quality: A Modeling Case Study for Râureni–Râmnicu Vâlcea (Romania) i. marinov a. m. marinov doi: 10.2495/CMEM-V2-N2-184-201 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 184 10.2495/CMEM-V2-N2-184-201 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-184-201 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-168-183 A steel plate is one of the critical components of a scroll expander system that can experience cavitation micro-pitting while in service. The content of the present paper consists of two distinct but interrelated parts. The first part aims to highlight that the use of computational fluid dynamics (CFD) simulations can constitute a potential tool for the prediction of cavitation erosion areas in scroll expander systems. For this purpose, a three-dimensional CFD, steady-state numerical simulation of the refrigerant working fluid is employed. Numerical results revealed the critical areas where cavitation bubbles are formed. These numerical critical areas are in direct qualitative agreement with the actual eroded regions by cavitation, which were found by microscopic observations across the steel plate on an after use, scroll expander system. The second part of the paper aims to further investigate the behaviour and the durability of the steel plate of the studied scroll expander system subjected to cavitation erosion by using an ultrasonic experimental test rig. Scanning electron microscopy and optical interferometer micrographs of the damaged surfaces were observed, showing the nature of the cavitation erosion mechanism and the morphological alterations of the steel plate samples. Experimental results are explained in terms of the cavitation erosion rates, roughness profile, accumulated strain energy, and hardness of the matrix. The experimental study can serve as a valuable input for future development of a CFD numerical model that predicts both cavitation bubbles formation as well as cavitation damage induced by the bubbles that implode on the steels plates. <![CDATA[ <p>A steel plate is one of the critical components of a scroll expander system that can experience cavitation micro-pitting while in service. The content of the present paper consists of two distinct but interrelated parts. The first part aims to highlight that the use of computational fluid dynamics (CFD) simulations can constitute a potential tool for the prediction of cavitation erosion areas in scroll expander systems. For this purpose, a three-dimensional CFD, steady-state numerical simulation of the refrigerant working fluid is employed. Numerical results revealed the critical areas where cavitation bubbles are formed. These numerical critical areas are in direct qualitative agreement with the actual eroded regions by cavitation, which were found by microscopic observations across the steel plate on an after use, scroll expander system. The second part of the paper aims to further investigate the behaviour and the durability of the steel plate of the studied scroll expander system subjected to cavitation erosion by using an ultrasonic experimental test rig. Scanning electron microscopy and optical interferometer micrographs of the damaged surfaces were observed, showing the nature of the cavitation erosion mechanism and the morphological alterations of the steel plate samples. Experimental results are explained in terms of the cavitation erosion rates, roughness profile, accumulated strain energy, and hardness of the matrix. The experimental study can serve as a valuable input for future development of a CFD numerical model that predicts both cavitation bubbles formation as well as cavitation damage induced by the bubbles that implode on the steels plates.</p> ]]> Cavitation Erosion Damage of Scroll Steel Plates by High-Speed Gas Working Fluid i. tzanakis a. georgoulas m. hadfield n. kotsovinos doi: 10.2495/CMEM-V2-N2-168-183 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 168 10.2495/CMEM-V2-N2-168-183 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-168-183 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-157-167 Efficiency is becoming more and more a main concern in the design of power transmissions and the demand for high efficiency gearboxes is continuously increasing. Also the more and more restrictive euro standards for the reduction of pollutant emissions from light vehicles impose to improve the efficiency of the engines but also of the gear transmissions. For this reason the resources dedicated to this goal are continuously increasing. The first step to improve efficiency is to have appropriate models to compare different design solutions. Even if the efficiency of transmissions is quit high if compared with the efficiency of the engines and appropriate models to predict the power losses due to gear meshing, to bearings and to seals already exist, in order to have a further improvement, some aspects like the power losses related to the oil churning, oil squeezing and windage are still to be investigated. In previous papers the authors have investigated by means of computational fluid dynamic (CFD) analysis and experimental measurements the churning losses of planetary speed reducers (in which there is a relative motion between the “planets + planet carrier” and the lubricant). Also the windage power losses have been studied by the authors in previous papers. This report is focused on the oil squeezing power losses. This kind of losses is associated with the compression expansion process by the meshing teeth. The contraction of the volume at the gear mesh implies an overpressure that induces a fluid flow primarily in the axial direction and this, for viscous fluids, means additional power losses and a decrease of the efficiency.In this work this phenomena has been studied by means of some CFD simulations. The influence of some operating conditions like the lubricant properties, the rotational speed and the temperature has been studied. <![CDATA[ <p>Efficiency is becoming more and more a main concern in the design of power transmissions and the demand for high efficiency gearboxes is continuously increasing. Also the more and more restrictive euro standards for the reduction of pollutant emissions from light vehicles impose to improve the efficiency of the engines but also of the gear transmissions. For this reason the resources dedicated to this goal are continuously increasing. The first step to improve efficiency is to have appropriate models to compare different design solutions. Even if the efficiency of transmissions is quit high if compared with the efficiency of the engines and appropriate models to predict the power losses due to gear meshing, to bearings and to seals already exist, in order to have a further improvement, some aspects like the power losses related to the oil churning, oil squeezing and windage are still to be investigated. In previous papers the authors have investigated by means of computational fluid dynamic (CFD) analysis and experimental measurements the churning losses of planetary speed reducers (in which there is a relative motion between the “planets + planet carrier” and the lubricant). Also the windage power losses have been studied by the authors in previous papers. This report is focused on the oil squeezing power losses. This kind of losses is associated with the compression expansion process by the meshing teeth. The contraction of the volume at the gear mesh implies an overpressure that induces a fluid flow primarily in the axial direction and this, for viscous fluids, means additional power losses and a decrease of the efficiency.In this work this phenomena has been studied by means of some CFD simulations. The influence of some operating conditions like the lubricant properties, the rotational speed and the temperature has been studied.</p> ]]> A CFD Analysis of the Oil Squeezing Power Losses of a Gear Pair franco concli carlo gorla doi: 10.2495/CMEM-V2-N2-157-167 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 157 10.2495/CMEM-V2-N2-157-167 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-157-167 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-145-156 Lattice Boltzmann method (LBM) is used to model the hydrogen production by splitting water by incident sunlight over Si nanorods. The purpose of this study is to investigate the transport and the formation of the hydrogen bubbles by electrochemical reactions with a 2D and a 3D numerical model using LBM. An ordered array of nanorods is created where each rod is 10 μm in high and 10 nm in diameter. The numerical models are simulated using MATLAB and parallel computing with the program Palabos. A reaction–advection–diffusion transport for two components is analyzed with electrochemical reactions. This process is further coupled with the momentum transport. The effect of different bond numbers and contact angels on the simulation results are analyzed. It has here been shown that LBM can be used to evaluate the transport processes at microscale and it is possible to include the effect of electrochemical reactions on the transport processes. An increased Bond number increases the bubble flow through the nanorod domain. A decreased contact angle facilitates the disconnection of the bubble to the nanorod at the top surface. The collection of the hydrogen bubbles at the top surface of the nanorods will be facilitated by an easy disconnection of the bubbles. <![CDATA[ <p>Lattice Boltzmann method (LBM) is used to model the hydrogen production by splitting water by incident sunlight over Si nanorods. The purpose of this study is to investigate the transport and the formation of the hydrogen bubbles by electrochemical reactions with a 2D and a 3D numerical model using LBM. An ordered array of nanorods is created where each rod is 10 μm in high and 10 nm in diameter. The numerical models are simulated using MATLAB and parallel computing with the program Palabos. A reaction–advection–diffusion transport for two components is analyzed with electrochemical reactions. This process is further coupled with the momentum transport. The effect of different bond numbers and contact angels on the simulation results are analyzed. It has here been shown that LBM can be used to evaluate the transport processes at microscale and it is possible to include the effect of electrochemical reactions on the transport processes. An increased Bond number increases the bubble flow through the nanorod domain. A decreased contact angle facilitates the disconnection of the bubble to the nanorod at the top surface. The collection of the hydrogen bubbles at the top surface of the nanorods will be facilitated by an easy disconnection of the bubbles.</p> ]]> Analysis of Hydrogen Bubble Flow Between Nanorods Using Lattice Boltzmann Method hedvig paradis costas grigoropoulos bengt sundén doi: 10.2495/CMEM-V2-N2-145-156 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 145 10.2495/CMEM-V2-N2-145-156 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-145-156 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-135-144 Glicksman’s viscous limit set of dimensionless parameters have been investigated using experimentally verified computational fluid dynamics model. Simulations have been performed for the two bubbling fluidized beds with different particle sizes and densities. Dimensionless average pressure drops across the bed height, dimensionless pressure standard deviations and dimensionless relative pressures have been investigated as a function of dimensionless superficial gas velocities for the two beds. Fluctuation of solid volume fraction and contours of solid volume fraction have also been investigated at different dimensionless gas velocities. Time series data of the pressure fluctuation and solid volume fraction are compared. The results indicate that the fluid dynamic similarity between two beds holds up to particle Reynolds number of 15. After this, the bubble activities in the two beds start to deviate significantly. The results of the work show that the analysis of solid volume fraction fluctuation gives higher accuracy than time-series pressure fluctuation when scaling the bubbling fluidized bed within the viscous limit. <![CDATA[ <p>Glicksman’s viscous limit set of dimensionless parameters have been investigated using experimentally verified computational fluid dynamics model. Simulations have been performed for the two bubbling fluidized beds with different particle sizes and densities. Dimensionless average pressure drops across the bed height, dimensionless pressure standard deviations and dimensionless relative pressures have been investigated as a function of dimensionless superficial gas velocities for the two beds. Fluctuation of solid volume fraction and contours of solid volume fraction have also been investigated at different dimensionless gas velocities. Time series data of the pressure fluctuation and solid volume fraction are compared. The results indicate that the fluid dynamic similarity between two beds holds up to particle Reynolds number of 15. After this, the bubble activities in the two beds start to deviate significantly. The results of the work show that the analysis of solid volume fraction fluctuation gives higher accuracy than time-series pressure fluctuation when scaling the bubbling fluidized bed within the viscous limit.</p> ]]> Scaling of Bubbling Fluidized Bed Reactors with Glicksman’s Viscous Limit Set and CFD Simulation r. k. thapa b. m. halvorsen doi: 10.2495/CMEM-V2-N2-135-144 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 2 Article 135 10.2495/CMEM-V2-N2-135-144 https://www.acadlore.com/article/IJCMEM/2014_2_2/CMEM-V2-N2-135-144 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-92-106 Most pavements in developing countries are designed based on index material properties related to a single design chart, restricting the incorporation of marginal and new materials for which the index property data sets are not available. To promote the introduction of naturally abundantly occurring marginal materials as well as recycled road base subbase materials in the road construction in those countries, mechanical behaviour of granular material can be used for design. The mechanical properties of these materials can be obtained from a simplified repeated load California bearing ratio (RL-CBR) characterization technique. An extensive RL-CBR characterization has been carried out on (sub) tropical base and subbase granular materials. A finite element method analysis has been attempted for the purpose of modelling the RL-CBR and derives an equivalent resilient modulus of the sample material. Furthermore, a cyclic triaxial test was carried out to validate the result of the RL-CBR. Through the RL-CBR characterization technique not only the practical accessibility of characterizing the mechanical behaviour of unbound granular materials is enhanced but also the effect of moisture content and degree of compaction on these behaviours is well demonstrated. <![CDATA[ <p>Most pavements in developing countries are designed based on index material properties related to a single design chart, restricting the incorporation of marginal and new materials for which the index property data sets are not available. To promote the introduction of naturally abundantly occurring marginal materials as well as recycled road base subbase materials in the road construction in those countries, mechanical behaviour of granular material can be used for design. The mechanical properties of these materials can be obtained from a simplified repeated load California bearing ratio (RL-CBR) characterization technique. An extensive RL-CBR characterization has been carried out on (sub) tropical base and subbase granular materials. A finite element method analysis has been attempted for the purpose of modelling the RL-CBR and derives an equivalent resilient modulus of the sample material. Furthermore, a cyclic triaxial test was carried out to validate the result of the RL-CBR. Through the RL-CBR characterization technique not only the practical accessibility of characterizing the mechanical behaviour of unbound granular materials is enhanced but also the effect of moisture content and degree of compaction on these behaviours is well demonstrated.</p> ]]> Simplified Characterization Techniques for (SUB) Tropical Base Materials and Modelling a. a. araya doi: 10.2495/CMEM-V2-N1-92-106 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 92 10.2495/CMEM-V2-N1-92-106 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-92-106 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-71-91 The presence of a sample matrix is one of the most important practical considerations in gas chromatography analysis as there are potentially numerous problems associated with matrix based injections. This paper aims to highlight the distinction between blank sample analysis and real sample analysis using automated solid phase extraction (SPE) and gas chromatography-mass spectrometry. Four reversed sorbent phases, including a Supelco LC-18, Strata C-18-E and Strata-X (styrene divinyl benzene) were used for SPE method development using an automated Gilson GX-271 AspecTM liquid handling instrument to determine the best solid phase and treatment for optimum organochlorine determination. The method developed proved to be valid when tested against parameters such as calibration range, coefficient of regression, linearity, repeatability and sensitivity. The StrataX and LC-18 cartridges produced the best recoveries, varying between 90% and 130% for most analytes. The LC-18 was selected for further analysis of the matrix effects as it showed greater reproducibility and method parameter robustness. Various real matrix sample volumes were tested on the selected LC-18 cartridge to determine its optimum maximum matrix load for efficient recoveries (breakthrough volume equivalent). A 100 ml sample volume was determined as the optimum matrix load volume as it produced more precise recoveries than other spiked sample matrix volumes. Visual comparison and analysis of selective ion monitoring chromatograms of both matrix based and matrix-free extracts indicate that there are significant matrix effects potentially capable of adversely affecting the chromatographic system from producing accurate identification and quantification of target analytes. <![CDATA[ <p>The presence of a sample matrix is one of the most important practical considerations in gas chromatography analysis as there are potentially numerous problems associated with matrix based injections. This paper aims to highlight the distinction between blank sample analysis and real sample analysis using automated solid phase extraction (SPE) and gas chromatography-mass spectrometry. Four reversed sorbent phases, including a Supelco LC-18, Strata C-18-E and Strata-X (styrene divinyl benzene) were used for SPE method development using an automated Gilson GX-271 AspecTM liquid handling instrument to determine the best solid phase and treatment for optimum organochlorine determination. The method developed proved to be valid when tested against parameters such as calibration range, coefficient of regression, linearity, repeatability and sensitivity. The StrataX and LC-18 cartridges produced the best recoveries, varying between 90% and 130% for most analytes. The LC-18 was selected for further analysis of the matrix effects as it showed greater reproducibility and method parameter robustness. Various real matrix sample volumes were tested on the selected LC-18 cartridge to determine its optimum maximum matrix load for efficient recoveries (breakthrough volume equivalent). A 100 ml sample volume was determined as the optimum matrix load volume as it produced more precise recoveries than other spiked sample matrix volumes. Visual comparison and analysis of selective ion monitoring chromatograms of both matrix based and matrix-free extracts indicate that there are significant matrix effects potentially capable of adversely affecting the chromatographic system from producing accurate identification and quantification of target analytes.</p> ]]> Matrix Influence on Determination of Organochlorine Pesticide Residues in Water by Solid Phase Extraction Coupled to Gas Chromatography-Mass Spectrometry c. rimayi d. odusanya f. mtunzi c. van wyk doi: 10.2495/CMEM-V2-N1-71-91 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 71 10.2495/CMEM-V2-N1-71-91 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-71-91 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-58-70 Due to the need to know and modify the radiation pattern of the ultrasonic sensors, to suit them to a particular application, in this paper is presented an automated measure system to obtain the radiation pattern for ultrasonic sensors in air. The system allows to obtain the radiation pattern in different conditions, for example for checking the characteristics of the ultrasonic sensors provided by the manufacturer, or for obtaining the modifications in the radiation pattern when a mechanical element is coupled to the ultrasonic sensor. In addition, the system has been improved by shortening the measurement time and decreasing the volume of data needed to carry out a measure. Furthermore, due to the fact of implementing the system inside a climatic chamber, the system allows to analyze the influence of environmental factors such as temperature and humidity, plus an evaluation of the degradation behaviour of the ultrasonic sensors in air under conditions of high temperature and humidity. At the end of the paper, two measurements have been done and the results have been compared with the characteristics of the radiation pattern provided by the manufacturer. Finally, a robust measurement system is presented, designed to find the modifications in the radiation pattern of an ultrasonic sensor when it is coupled to a mechanical element. <![CDATA[ <p>Due to the need to know and modify the radiation pattern of the ultrasonic sensors, to suit them to a particular application, in this paper is presented an automated measure system to obtain the radiation pattern for ultrasonic sensors in air. The system allows to obtain the radiation pattern in different conditions, for example for checking the characteristics of the ultrasonic sensors provided by the manufacturer, or for obtaining the modifications in the radiation pattern when a mechanical element is coupled to the ultrasonic sensor. In addition, the system has been improved by shortening the measurement time and decreasing the volume of data needed to carry out a measure. Furthermore, due to the fact of implementing the system inside a climatic chamber, the system allows to analyze the influence of environmental factors such as temperature and humidity, plus an evaluation of the degradation behaviour of the ultrasonic sensors in air under conditions of high temperature and humidity. At the end of the paper, two measurements have been done and the results have been compared with the characteristics of the radiation pattern provided by the manufacturer. Finally, a robust measurement system is presented, designed to find the modifications in the radiation pattern of an ultrasonic sensor when it is coupled to a mechanical element.</p> ]]> Optimized Automatic System to Obtain Ultrasonic Radiation Patterns m. fernández c. rodríguez l. alonso j. m. pérez-oria doi: 10.2495/CMEM-V2-N1-58-70 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 58 10.2495/CMEM-V2-N1-58-70 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-58-70 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-46-57 As a first step towards a new approach for the simulation of two-phase flows, the objective of this work is to check out the prediction of a model dedicated to large and distorted bubbles on two bubble coalescence cases. The multifield hybrid approach for two-phase flow modelling consists in dealing separately with the small and spherical bubbles, treated with a dispersed approach, and with the large and distorted ones, whose interface is located. The overall method relies also on an existing building block, consisting in a set of averaged models dedicated to dispersed bubbles, which has already been validated and has given a reasonable agreement with experimental data in cases where the spherical shape assumption is still valid for the dispersed phase. This paper aims to assess a conservative interface locating method based on level set adapted to two-fluid model for two-phase flows. The interface locating method is a part of a model dedicated to the simulation of large and distorted bubbles. At different liquid viscosities and densities, the model provides reasonable predictions of terminal velocities and shapes for rising bubble experiments. The main outcome is the simulation of bubble coalescence where the distortion of the interface during the coalescence phenomenon is followed. The ability to simulate coalescence phenomena correctly is an important issue in the modelling of slug flows with interface locating methods. <![CDATA[ <p>As a first step towards a new approach for the simulation of two-phase flows, the objective of this work is to check out the prediction of a model dedicated to large and distorted bubbles on two bubble coalescence cases. The multifield hybrid approach for two-phase flow modelling consists in dealing separately with the small and spherical bubbles, treated with a dispersed approach, and with the large and distorted ones, whose interface is located. The overall method relies also on an existing building block, consisting in a set of averaged models dedicated to dispersed bubbles, which has already been validated and has given a reasonable agreement with experimental data in cases where the spherical shape assumption is still valid for the dispersed phase. This paper aims to assess a conservative interface locating method based on level set adapted to two-fluid model for two-phase flows. The interface locating method is a part of a model dedicated to the simulation of large and distorted bubbles. At different liquid viscosities and densities, the model provides reasonable predictions of terminal velocities and shapes for rising bubble experiments. The main outcome is the simulation of bubble coalescence where the distortion of the interface during the coalescence phenomenon is followed. The ability to simulate coalescence phenomena correctly is an important issue in the modelling of slug flows with interface locating methods.</p> ]]> Multifield Hybrid Method Applied to Bubble Rising and Coalescence r. denefle s. mimouni j-p. caltagirone s. vincent doi: 10.2495/CMEM-V2-N1-46-57 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 46 10.2495/CMEM-V2-N1-46-57 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-46-57 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-30-45 Cables and various subsea product flow-lines are often subjected to flow-induced vibrations as a consequence of wave or wave and current flow excitation. An experimental study that explores the comparative suppression effectiveness of airfoil and ribbon fairings is presented. In the experimental investigation, an instrumented tensioned 29 m horizontal composite cylinder with a length to diameter ratio of 760 is subjected to a range of uniform current and combined current and regular wave conditions. In the analysis of the cross-flow response amplitude ratios, modal parameters, such as mode shape, damping ratio were extracted. The analytical procedures were performed using a modified time domain decomposition technique. The analysis illustrated the amplified response behavior for bare cylinders, and illustrated that full coverage by airfoil and ribbon fairings could effectively suppress flow-induced vibrations in current only conditions, but both fairings were ineffective when regular wave conditions were superimposed on the uniform current conditions, even though the airfoil provided larger damping than ribbon fairings. Under combined wave and current conditions, the response behavior of either suppression device was found to be insensitive to coverage densities. <![CDATA[ <p>Cables and various subsea product flow-lines are often subjected to flow-induced vibrations as a consequence of wave or wave and current flow excitation. An experimental study that explores the comparative suppression effectiveness of airfoil and ribbon fairings is presented. In the experimental investigation, an instrumented tensioned 29 m horizontal composite cylinder with a length to diameter ratio of 760 is subjected to a range of uniform current and combined current and regular wave conditions. In the analysis of the cross-flow response amplitude ratios, modal parameters, such as mode shape, damping ratio were extracted. The analytical procedures were performed using a modified time domain decomposition technique. The analysis illustrated the amplified response behavior for bare cylinders, and illustrated that full coverage by airfoil and ribbon fairings could effectively suppress flow-induced vibrations in current only conditions, but both fairings were ineffective when regular wave conditions were superimposed on the uniform current conditions, even though the airfoil provided larger damping than ribbon fairings. Under combined wave and current conditions, the response behavior of either suppression device was found to be insensitive to coverage densities.</p> ]]> Comparison of Airfoil and Ribbon Fairings for Suppression of Flow-Induced Vibrations s. m. fang j. m. niedzwecki doi: 10.2495/CMEM-V2-N1-30-45 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 30 10.2495/CMEM-V2-N1-30-45 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-30-45 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-14-29 In this study, the energy distributions of actively or passively controlled multistory nonlinear shear structures are investigated. Nonlinear differential equations of motion of the structure and the energy equations are derived for an uncontrolled and a controlled structure. A computer program which takes into account the nonlinearity of the material is developed and used for the dynamic analysis of the controlled and the uncontrolled structure. As numerical examples, two different structures are examined with six different control cases. These structures are a three-story and a twelve-story shear structure. In the dynamic analysis, the Erzincan and El Centro earthquakes are used. Active and passive controls are obtained by implementing base isolation and a mass damper into the structure. In addition, a hybrid structural control case is examined by implementing base isolation with an active mass damper to the structure. In total, six different passive and active control cases are investigated. An instantaneous optimal control algorithm, which minimizes the performance index defined as a time-dependent quadratic scalar functional instead of a quadratic integral functional and takes into account only the current state, is used as an active control algorithm. The results are given as force-displacement, acceleration, and energies in a comparative way for uncontrolled and controlled structures. The results show that the responses of the structure are reduced and the structural behavior is improved by using structural control. <![CDATA[ <p>In this study, the energy distributions of actively or passively controlled multistory nonlinear shear structures are investigated. Nonlinear differential equations of motion of the structure and the energy equations are derived for an uncontrolled and a controlled structure. A computer program which takes into account the nonlinearity of the material is developed and used for the dynamic analysis of the controlled and the uncontrolled structure. As numerical examples, two different structures are examined with six different control cases. These structures are a three-story and a twelve-story shear structure. In the dynamic analysis, the Erzincan and El Centro earthquakes are used. Active and passive controls are obtained by implementing base isolation and a mass damper into the structure. In addition, a hybrid structural control case is examined by implementing base isolation with an active mass damper to the structure. In total, six different passive and active control cases are investigated. An instantaneous optimal control algorithm, which minimizes the performance index defined as a time-dependent quadratic scalar functional instead of a quadratic integral functional and takes into account only the current state, is used as an active control algorithm. The results are given as force-displacement, acceleration, and energies in a comparative way for uncontrolled and controlled structures. The results show that the responses of the structure are reduced and the structural behavior is improved by using structural control.</p> ]]> Energy Distributions in Actively and Passively Controlled Nonlinear Structures a. yanik u. aldemir m. bakioglu doi: 10.2495/CMEM-V2-N1-14-29 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 14 10.2495/CMEM-V2-N1-14-29 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-14-29 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-107-125 In the design of the controllers of hybrid renewable energy system (HRES), the system dynamics and constraints need to be modelled and simulated in conjunction with the controller itself. This paper presents mathematical and equivalent electrical models taking into consideration all system dynamics and constraints for the solar branch of HRES. This branch consists of photovoltaic (PV) array, load and battery connected through a boost-type DC–DC converter. The probabilistic behaviour of the solar irradiance, which intrinsically includes the effect of cloud shading, and the dynamics of the battery are also modelled. The platform developed for dynamic simulation of the solar branch of HRES can be employed for design of DC–DC converter controllers as well as design of energy management systems. <![CDATA[ <p>In the design of the controllers of hybrid renewable energy system (HRES), the system dynamics and constraints need to be modelled and simulated in conjunction with the controller itself. This paper presents mathematical and equivalent electrical models taking into consideration all system dynamics and constraints for the solar branch of HRES. This branch consists of photovoltaic (PV) array, load and battery connected through a boost-type DC–DC converter. The probabilistic behaviour of the solar irradiance, which intrinsically includes the effect of cloud shading, and the dynamics of the battery are also modelled. The platform developed for dynamic simulation of the solar branch of HRES can be employed for design of DC–DC converter controllers as well as design of energy management systems.</p> ]]> Modelling and Simulation of Standalone Solar Power Systems a. m. dizqah a. maheri k. busawon a. kamjoo doi: 10.2495/CMEM-V2-N1-107-125 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 107 10.2495/CMEM-V2-N1-107-125 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-107-125 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-1-13 Vibrations caused by road or railway vehicles running on surface or underground roads or rail tracks spread through the subsoil into surrounding building structures. These vibrations usually pose no threat to the safety of the structures, but they may limit the use of devices sensitive to vibrations in the buildings. An elastic foundation for the whole structure on a compliant rubber layer inserted into the foundation structure is a solution that restricts the transfer of vibrations into the buildings. The reinforced concrete structure of a building is used as an example here to illustrate the efficiency of using a rubber layer in the footing bottom in order to reduce the propagation of vibrations into the building below the level observed in a non-isolated building structure when loaded by vibrations induced by traffic. <![CDATA[ <p>Vibrations caused by road or railway vehicles running on surface or underground roads or rail tracks spread through the subsoil into surrounding building structures. These vibrations usually pose no threat to the safety of the structures, but they may limit the use of devices sensitive to vibrations in the buildings. An elastic foundation for the whole structure on a compliant rubber layer inserted into the foundation structure is a solution that restricts the transfer of vibrations into the buildings. The reinforced concrete structure of a building is used as an example here to illustrate the efficiency of using a rubber layer in the footing bottom in order to reduce the propagation of vibrations into the building below the level observed in a non-isolated building structure when loaded by vibrations induced by traffic.</p> ]]> Structure Isolation in Order to Reduce Vibration Transfer from the Subsoil d. makovicka d. makovicka doi: 10.2495/CMEM-V2-N1-1-13 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2014 2 1 Article 1 10.2495/CMEM-V2-N1-1-13 https://www.acadlore.com/article/IJCMEM/2014_2_1/CMEM-V2-N1-1-13 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-385-397 Parametric accelerated life testing (ALT) with the reliability quantitative (RQ) specifications is recommended as reliability methodology to pinpoint design flaws and correct them in transit. It covers (1) cycles of an accumulated failure rate of X% (BX) lifetime with ALT strategy, (2) fatigue design, (3) ALTs with alterations, and (4) discernment if design(s) obtains targeted BX life. The quantum/transport-based (generalized) life-stress failure prototype and sample size formulation for generating RQ specifications were suggested. The equivalent elevated damage potential in parametric ALT was applied, represented by field power spectral density. A case study was used to evaluate a refrigerator fatigued during rail. In first ALT, for RQ specifications – 40 min, refrigerator tubes made of ethylene propylene diene monomer rubber fractured because of mount designs. The failed shape in first ALT was alike to those of the field refrigerator. After mounts and tubes were redesigned, there were no difficulties during second ALT. Refrigerator was assured to fulfill a B1 lifetime for travel distance. 11-28-2022 <![CDATA[ <p>Parametric accelerated life testing (ALT) with the reliability quantitative (RQ) specifications is recommended as reliability methodology to pinpoint design flaws and correct them in transit. It covers (1) cycles of an accumulated failure rate of X% (BX) lifetime with ALT strategy, (2) fatigue design, (3) ALTs with alterations, and (4) discernment if design(s) obtains targeted BX life. The quantum/transport-based (generalized) life-stress failure prototype and sample size formulation for generating RQ specifications were suggested. The equivalent elevated damage potential in parametric ALT was applied, represented by field power spectral density. A case study was used to evaluate a refrigerator fatigued during rail. In first ALT, for RQ specifications – 40 min, refrigerator tubes made of ethylene propylene diene monomer rubber fractured because of mount designs. The failed shape in first ALT was alike to those of the field refrigerator. After mounts and tubes were redesigned, there were no difficulties during second ALT. Refrigerator was assured to fulfill a B1 lifetime for travel distance.</p> ]]> Enhancing the Life of Mechanical Systems Such as Refrigerator in Rail Transit Based on Life-Stress Model and Sample Size Formulation seong-woo woo dennis l. o’neal yimer mohammed hassen gezae mebrahtu doi: 10.2495/CMEM-V10-N4-385-397 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 385 10.2495/CMEM-V10-N4-385-397 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-385-397 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-372-384 To make railway systems more autonomous and energy efficient, the suction phenomenon induced by virtual coupling (VC) can be considered as a beneficial source of energy saving since trains are very closely spaced. A minimum safe distance between railway systems must be defined and maintained to ensure the safety of the whole convoy. The purpose of this paper is to study and quantify the aerodynamic gain in case of VC of two modular and autonomous trains ‘Smart Cabins’ as designated in our project. Computational fluid dynamics simulations are investigated to analyze the aerodynamic effect under several scenarios by varying the inter-cabins distance. Some design simplifications have been made for each Smart Cabin to prepare simulations and reduce computation time. Simulation results confirm the interest of VC in the sense of reducing coefficient drag of the full convoy up to 27%, which reflects a power gain of about 4% of the total traction power required for a single Smart Cabin (~200 kW). 11-28-2022 <![CDATA[ <p>To make railway systems more autonomous and energy efficient, the suction phenomenon induced by virtual coupling (VC) can be considered as a beneficial source of energy saving since trains are very closely spaced. A minimum safe distance between railway systems must be defined and maintained to ensure the safety of the whole convoy. The purpose of this paper is to study and quantify the aerodynamic gain in case of VC of two modular and autonomous trains ‘Smart Cabins’ as designated in our project. Computational fluid dynamics simulations are investigated to analyze the aerodynamic effect under several scenarios by varying the inter-cabins distance. Some design simplifications have been made for each Smart Cabin to prepare simulations and reduce computation time. Simulation results confirm the interest of VC in the sense of reducing coefficient drag of the full convoy up to 27%, which reflects a power gain of about 4% of the total traction power required for a single Smart Cabin (~200 kW).</p> ]]> Quantification of the Aerodynamic Gain on Two Virtually Coupled Modular Trains siwar fadhel samuel fromont doi: 10.2495/CMEM-V10-N4-372-384 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 372 10.2495/CMEM-V10-N4-372-384 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-372-384 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-359-371 Monitoring systems are a key tool to improve the safety of railway vehicles and to support maintenance activities. Their on-board application on railway vehicles is currently well established on newly built passenger vehicles, while their use on freight vehicles is not yet sufficiently widespread. This is due to the complex management of the operating procedures of the freight wagons, to the substantial impact of the cost of these systems compared to the cost of the wagon and to the common lack of electrification on freight wagons.This work illustrates the characteristics of a monitoring system developed at Politecnico di Torino and previously installed on freight vehicles and operationally tested as regards the detection of accelerations and temperatures as diagnostic parameters. This system has been improved by adding diagnostics of the vehicle braking system, in order to detect anomalies during braking operations and to support maintenance procedures. The activity described in the present work aims to identify, beyond the specific diagnostic system that has been implemented, the basic characteristics that a modern monitoring system, intended to be installed on railway freight wagons, should feature. The new version of the monitoring system that has been developed at Politecnico di Torino has been preliminarily tested on a scaled roller-rig in order to monitor the braking system even in abnormal operating conditions, which would be difficult to reproduce safely on a real vehicle. The monitoring system is equipped with an axle generator capable of autonomously supporting its operation, and it is also provided with a diagnostic information processing system and communication protocols to send outside this information. 11-28-2022 <![CDATA[ <p>Monitoring systems are a key tool to improve the safety of railway vehicles and to support maintenance activities. Their on-board application on railway vehicles is currently well established on newly built passenger vehicles, while their use on freight vehicles is not yet sufficiently widespread. This is due to the complex management of the operating procedures of the freight wagons, to the substantial impact of the cost of these systems compared to the cost of the wagon and to the common lack of electrification on freight wagons.</p><p>This work illustrates the characteristics of a monitoring system developed at Politecnico di Torino and previously installed on freight vehicles and operationally tested as regards the detection of accelerations and temperatures as diagnostic parameters. This system has been improved by adding diagnostics of the vehicle braking system, in order to detect anomalies during braking operations and to support maintenance procedures. The activity described in the present work aims to identify, beyond the specific diagnostic system that has been implemented, the basic characteristics that a modern monitoring system, intended to be installed on railway freight wagons, should feature. The new version of the monitoring system that has been developed at Politecnico di Torino has been preliminarily tested on a scaled roller-rig in order to monitor the braking system even in abnormal operating conditions, which would be difficult to reproduce safely on a real vehicle. The monitoring system is equipped with an axle generator capable of autonomously supporting its operation, and it is also provided with a diagnostic information processing system and communication protocols to send outside this information.</p> ]]> Monitoring Systems for Railways Freight Vehicles nicola bosso matteo magelli nicolò zampieri doi: 10.2495/CMEM-V10-N4-359-371 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 359 10.2495/CMEM-V10-N4-359-371 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-359-371 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-345-358 As freight transportation demand increases worldwide, railway practitioners must carefully manage the capacity of existing facilities to ensure efficient and reliable operations. Railroad gravity hump classification (marshalling) yards, where individual railcars (wagons) are sorted into new trains to reach their destination, are an integral part of the freight rail network. Efficient operation of yard processes is critical to overall freight railway performance as individual carload shipments moving in manifest trains spend most of their transit time waiting for connections at intermediate yards, with more than half of this waiting time spent dwelling on classification bowl tracks. Previous research has developed optimal strategies to allocate bowl tracks to blocks for a given set of yard track lengths. However, these strategies make simple assumptions about the performance impact of over-length blocks due to a lack of basic analytical models to describe this relationship. To meet this need, this paper develops an original hump classification yard model using AnyLogic simulation software. A representative yard with accurate geometry and operating parameters reflecting real-world practice is constructed using AutoCAD and exported to AnyLogic. The AnyLogic discrete-event simulation model uses custom Java code to determine traffic flows and railcar movements in the yard, and output performance metrics. With complete flexibility to change track layout patterns, a series of simulation experiments quantify fundamental classification yard capacity relationships between performance metrics and the distribution of track lengths, as a function of the railcar throughput volume and size of outbound blocks created in the yard. The resulting relationships are expected to better inform railway yard operating strategies as traffic, train length, and block size increase but yard track lengths remain static. 11-28-2022 <![CDATA[ <p>As freight transportation demand increases worldwide, railway practitioners must carefully manage the capacity of existing facilities to ensure efficient and reliable operations. Railroad gravity hump classification (marshalling) yards, where individual railcars (wagons) are sorted into new trains to reach their destination, are an integral part of the freight rail network. Efficient operation of yard processes is critical to overall freight railway performance as individual carload shipments moving in manifest trains spend most of their transit time waiting for connections at intermediate yards, with more than half of this waiting time spent dwelling on classification bowl tracks. Previous research has developed optimal strategies to allocate bowl tracks to blocks for a given set of yard track lengths. However, these strategies make simple assumptions about the performance impact of over-length blocks due to a lack of basic analytical models to describe this relationship. To meet this need, this paper develops an original hump classification yard model using AnyLogic simulation software. A representative yard with accurate geometry and operating parameters reflecting real-world practice is constructed using AutoCAD and exported to AnyLogic. The AnyLogic discrete-event simulation model uses custom Java code to determine traffic flows and railcar movements in the yard, and output performance metrics. With complete flexibility to change track layout patterns, a series of simulation experiments quantify fundamental classification yard capacity relationships between performance metrics and the distribution of track lengths, as a function of the railcar throughput volume and size of outbound blocks created in the yard. The resulting relationships are expected to better inform railway yard operating strategies as traffic, train length, and block size increase but yard track lengths remain static.</p> ]]> Quantifying the Impact of Classification Track Length Constraints on Railway Gravity Hump Marshalling Yard Performance with Anylogic Simulation jiaxi zhao c. tyler dick doi: 10.2495/CMEM-V10-N4-345-358 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 345 10.2495/CMEM-V10-N4-345-358 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-345-358 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-329-344 In turning processes, cutting force is of great importance since many cutting force features are useful for predicting and detecting tool conditions. To precisely measure cutting forces, many commercial devices have been developed; however, they are costly, cumbersome, and some implementation restrictions could hinder their suitability in real applications. In this work, a simple, portable, and low-cost tool holder sensor was designed and developed to sense strain and measure cutting force applied during ultra-precision diamond turning. The device can assess cutting intensity up to 3 N with a high sensitivity of 4.592 mV/N or 0.004592 V/N, a calibration test variability of 99.6%, and a percentage error of 2.19, according to static calibration testing. 11-28-2022 <![CDATA[ <p>In turning processes, cutting force is of great importance since many cutting force features are useful for predicting and detecting tool conditions. To precisely measure cutting forces, many commercial devices have been developed; however, they are costly, cumbersome, and some implementation restrictions could hinder their suitability in real applications. In this work, a simple, portable, and low-cost tool holder sensor was designed and developed to sense strain and measure cutting force applied during ultra-precision diamond turning. The device can assess cutting intensity up to 3 N with a high sensitivity of 4.592 mV/N or 0.004592 V/N, a calibration test variability of 99.6%, and a percentage error of 2.19, according to static calibration testing.</p> ]]> Self-sensing Tool Holder for In-process Metrology of Cutting Force in Ultra-High- Precision Single-Point Diamond Turning Applications peter babatunde odedeyi khaled abou-el-hossein shahrokh hatefi funsho oyekunle doi: 10.2495/CMEM-V10-N4-329-344 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 329 10.2495/CMEM-V10-N4-329-344 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-329-344 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-314-328 Due to the climate crisis, extreme fluctuations in temperature are caused by the high sources of energy, and carbon consumption have a great impact on both construction and water resources management. Accordingly, the world today is paying attention to searching for cleaner energy resources. In Egypt, the extreme heat of the summer seasons causes constant air-conditioner (AC) usage in building to provide cooling, which produces outlet wastewater. The continuous flow of this outlet wastewater results in cracks and erosion among the facades that need maintenance.As a way to search for environmentally friendly material that can reuse this outlet water and reduce the solar radiation on the façade providing more cooler spaces, algae are suggested due to their availability in water from several sources in Egypt. This paper presents the assessment of an innovative façade element photobioreactors (PBR) made from algae on a real administrative building facade in Cairo. The aim is to evaluate digitally by simulation the solar radiation reduced from the façade that acts as a double green skin and self-watering system with an appealing aesthetic form preventing any erosion on the façade surfaces.The method of assessment is done using Ladybug plug-in simulation in Grasshopper plug-in in Rhino software based on the climatic data from EnergyPlus. Four main phases are followed: 1) the form generation of the façade using Rhinoceros software, 2) the simulation to assess the solar radiation before and after adding the PBR, 3) the evaluation phase to calculate the thermal conductivity and water temperature mathematically, and 4) fabrication of small-scale façade using the 3D-printed technique with algae filament.The results recorded a reduction in the solar radiation from 301 to 75 kWh/m2 comparing the current case of the building façade, while the thermal performance was 0.36 W/m2K, which is better than the most common materials used in arid climates such as rammed earth, fired brick, and concrete. The optimization of the algae tube length was based on the required outlet temperature that is suitable for plantation 15°C to help in reducing the water temperature.The finding addresses the significant role of using algae that can generate biomass to explore their benefits regarding their O2 production and CO2 absorption through 3D printing, which is considered a cleaner technology. 11-28-2022 <![CDATA[ <p>Due to the climate crisis, extreme fluctuations in temperature are caused by the high sources of energy, and carbon consumption have a great impact on both construction and water resources management. Accordingly, the world today is paying attention to searching for cleaner energy resources. In Egypt, the extreme heat of the summer seasons causes constant air-conditioner (AC) usage in building to provide cooling, which produces outlet wastewater. The continuous flow of this outlet wastewater results in cracks and erosion among the facades that need maintenance.</p><p>As a way to search for environmentally friendly material that can reuse this outlet water and reduce the solar radiation on the façade providing more cooler spaces, algae are suggested due to their availability in water from several sources in Egypt. This paper presents the assessment of an innovative façade element photobioreactors (PBR) made from algae on a real administrative building facade in Cairo. The aim is to evaluate digitally by simulation the solar radiation reduced from the façade that acts as a double green skin and self-watering system with an appealing aesthetic form preventing any erosion on the façade surfaces.</p><p>The method of assessment is done using Ladybug plug-in simulation in Grasshopper plug-in in Rhino software based on the climatic data from EnergyPlus. Four main phases are followed: 1) the form generation of the façade using Rhinoceros software, 2) the simulation to assess the solar radiation before and after adding the PBR, 3) the evaluation phase to calculate the thermal conductivity and water temperature mathematically, and 4) fabrication of small-scale façade using the 3D-printed technique with algae filament.</p><p>The results recorded a reduction in the solar radiation from 301 to 75 kWh/m² comparing the current case of the building façade, while the thermal performance was 0.36 W/m²K, which is better than the most common materials used in arid climates such as rammed earth, fired brick, and concrete. The optimization of the algae tube length was based on the required outlet temperature that is suitable for plantation 15°C to help in reducing the water temperature.</p><p>The finding addresses the significant role of using algae that can generate biomass to explore their benefits regarding their O₂ production and CO₂ absorption through 3D printing, which is considered a cleaner technology.</p> ]]> Optimization of an Adaptive Algae Façade Based on Solar Radiation Simulation deena el-mahdy ahmed khaled youssef doi: 10.2495/CMEM-V10-N4-314-328 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 314 10.2495/CMEM-V10-N4-314-328 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-314-328 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-303-313 Computer-aided engineering (CAE) refers to software applications aimed at helping solve technological problems through numerical methods. Exploiting CAE, it is possible to evaluate determined systems through virtual models rather than physical prototypes. By doing so, useful information on the system’s performance can be gathered at the beginning of the design phase, when the modifications to the project cost less. In the field of lubrication and efficiency, computational fluid dynamics (CFD) has been applied to geared transmissions, leading to an important step forward in the understanding of multiphase physics and the optimization of the systems’ layout. Being the simulations of gears non-stationary, the topological changes of the domain require the adoption of mesh-handling strategies capable of accomplishing the boundaries’ rotation. In this analysis, the Global Remeshing Algorithm with Mesh Clustering (GRAMC), previously developed by the authors to reduce the computational time associated with the remeshing process, is applied to study dip and injection lubrication in helical and spur gearboxes. The results suggest that this methodology is an effective and efficient solution to analyse the lubrication and the efficiency even for complex kinematics. The investigation was conducted in the OpenFOAM framework. 11-28-2022 <![CDATA[ <p>Computer-aided engineering (CAE) refers to software applications aimed at helping solve technological problems through numerical methods. Exploiting CAE, it is possible to evaluate determined systems through virtual models rather than physical prototypes. By doing so, useful information on the system’s performance can be gathered at the beginning of the design phase, when the modifications to the project cost less. In the field of lubrication and efficiency, computational fluid dynamics (CFD) has been applied to geared transmissions, leading to an important step forward in the understanding of multiphase physics and the optimization of the systems’ layout. Being the simulations of gears non-stationary, the topological changes of the domain require the adoption of mesh-handling strategies capable of accomplishing the boundaries’ rotation. In this analysis, the Global Remeshing Algorithm with Mesh Clustering (GRAMC), previously developed by the authors to reduce the computational time associated with the remeshing process, is applied to study dip and injection lubrication in helical and spur gearboxes. The results suggest that this methodology is an effective and efficient solution to analyse the lubrication and the efficiency even for complex kinematics. The investigation was conducted in the OpenFOAM framework.</p> ]]> Application of the $\mathrm{GRA}^{\mathrm{MC}}$ Mesh-handling Strategy for the Simulation of Dip and Injection Lubrication in Gearboxes marco nicola mastrone franco concli doi: 10.2495/CMEM-V10-N4-303-313 International Journal of Computational Methods and Experimental Measurements 11-28-2022 International Journal of Computational Methods and Experimental Measurements 11-28-2022 2022 10 4 Article 303 10.2495/CMEM-V10-N4-303-313 https://www.acadlore.com/article/IJCMEM/2022_10_4/CMEM-V10-N4-303-313 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-282-294 This paper presents a novel hydrochemical and radiometric data of groundwater sampled from Serra Negra spa town, São Paulo State, Brazil. Every year, many visitors travel to the municipality, thus, recurrent analyses are recommended and necessary, as the local water is heavily consumed. However, gaps exist in this regard, especially for the groundwater selected for sampling in this paper, since there is no analytical data on its chemical composition. The results obtained were compared with the drinking water standards in relation to the analyzed parameters. The radioactivity of all analyzed samples was below the values established by the World Health Organization of 0.5 and 1 Bq. L−1 for gross alpha and beta activities, respectively. In general, the hydrochemical parameters analyzed did not exceed the reference limits established by Brazilian and international legislation, with the exception of pH for one water sample and nitrate for another. The use of Pearson’s correlation coefficient reinforced the proportionality between electrical conductivity and dissolved salts. In the chemical aspect, the dominant anion in the waters was bicarbonate, agreeing with the observed pH, while the predominant cation was sodium, possibly suggesting a slightly more evolved hydrogeochemical context. Although the Brazilian legislation does not mention a reference value for the ingestion of silicon in water, in this paper some comments were made about its presence in the analyzed groundwaters. 09-26-2022 <![CDATA[ <p>This paper presents a novel hydrochemical and radiometric data of groundwater sampled from Serra Negra spa town, São Paulo State, Brazil. Every year, many visitors travel to the municipality, thus, recurrent analyses are recommended and necessary, as the local water is heavily consumed. However, gaps exist in this regard, especially for the groundwater selected for sampling in this paper, since there is no analytical data on its chemical composition. The results obtained were compared with the drinking water standards in relation to the analyzed parameters. The radioactivity of all analyzed samples was below the values established by the World Health Organization of 0.5 and 1 Bq. L⁻¹ for gross alpha and beta activities, respectively. In general, the hydrochemical parameters analyzed did not exceed the reference limits established by Brazilian and international legislation, with the exception of pH for one water sample and nitrate for another. The use of Pearson’s correlation coefficient reinforced the proportionality between electrical conductivity and dissolved salts. In the chemical aspect, the dominant anion in the waters was bicarbonate, agreeing with the observed pH, while the predominant cation was sodium, possibly suggesting a slightly more evolved hydrogeochemical context. Although the Brazilian legislation does not mention a reference value for the ingestion of silicon in water, in this paper some comments were made about its presence in the analyzed groundwaters.</p> ]]> Hydrochemical and Radiometric Study of Groundwaters from Serra Negra Spa, São Paulo State, Brazil pietro d. avona daniel m. bonotto doi: 10.2495/CMEM-V10-N3-282-294 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 282 10.2495/CMEM-V10-N3-282-294 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-282-294 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-271-281 The purpose of this study is to investigate the effect of the addition of sub-micron glass fiber (sGF) into the matrix of carbon fiber reinforced plastics (CFRP) on the impact energy absorption and Compressive after impact (CAI) strength of it. The unidirectional (UD)-CFRP was fabricated with UD-carbon fiber fabric and thermoset epoxy resin modified by adding 0.3wt% of sGF. For comparison, UD-CFRP made with the neat epoxy resin was also prepared. The impact energy absorption under out-of-plane impact was measured by using falling-type impact testing equipment. In this study, the applied impact energy was 3, 5, 7, 10, and 20 J by changing the mass of the drop weight. After the tests, a compressive load was also applied to the specimen to investigate the CAI strength of UD-CFRP. Test results showed that when the applied impact energy was relatively low (3 and 5 J), the energy absorption of the modified UD-CFRP was slightly improved, compared to that of the neat UD-CFRP. The projection areas of internal damages of UD-CFRP after the drop weight test were also decreased by the sGF addition. However, when the applied impact energy exceeds 7 J, there were no differences in the energy absorption of UD-CFRP even if the sGF was added to the matrix. The scanning electron microscope (SEM) observations of the fractured surface of UD-CFRP after the drop weight test suggested that the adhesion between carbon fiber and matrix resin was improved by the addition of sGF when the low impact energy was applied. The interlaminar shear strength of the modified UD-CFRP was also improved. The CAI strength of modified UD-CFRP was improved when the applied impact energy was relatively low. However, when the applied impact energy exceeds 7 J, the CAI strength of UD-CFRP was degraded by adding sGF. Therefore, when low impact loading was applied, the addition of sGF into UD-CFRP was effective to improve CAI strength. 09-26-2022 <![CDATA[ <p>The purpose of this study is to investigate the effect of the addition of sub-micron glass fiber (sGF) into the matrix of carbon fiber reinforced plastics (CFRP) on the impact energy absorption and Compressive after impact (CAI) strength of it. The unidirectional (UD)-CFRP was fabricated with UD-carbon fiber fabric and thermoset epoxy resin modified by adding 0.3wt% of sGF. For comparison, UD-CFRP made with the neat epoxy resin was also prepared. The impact energy absorption under out-of-plane impact was measured by using falling-type impact testing equipment. In this study, the applied impact energy was 3, 5, 7, 10, and 20 J by changing the mass of the drop weight. After the tests, a compressive load was also applied to the specimen to investigate the CAI strength of UD-CFRP. Test results showed that when the applied impact energy was relatively low (3 and 5 J), the energy absorption of the modified UD-CFRP was slightly improved, compared to that of the neat UD-CFRP. The projection areas of internal damages of UD-CFRP after the drop weight test were also decreased by the sGF addition. However, when the applied impact energy exceeds 7 J, there were no differences in the energy absorption of UD-CFRP even if the sGF was added to the matrix. The scanning electron microscope (SEM) observations of the fractured surface of UD-CFRP after the drop weight test suggested that the adhesion between carbon fiber and matrix resin was improved by the addition of sGF when the low impact energy was applied. The interlaminar shear strength of the modified UD-CFRP was also improved. The CAI strength of modified UD-CFRP was improved when the applied impact energy was relatively low. However, when the applied impact energy exceeds 7 J, the CAI strength of UD-CFRP was degraded by adding sGF. Therefore, when low impact loading was applied, the addition of sGF into UD-CFRP was effective to improve CAI strength.</p> ]]> Effect of Sub-micron Glass Fiber Addition on CAI Strength Of UD-CFRP ryotaro murayama kiyotaka obunai kazuya okubo doi: 10.2495/CMEM-V10-N3-271-281 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 271 10.2495/CMEM-V10-N3-271-281 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-271-281 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-260-270 Human health risk assessment for off-site receptors located in the proximity of a contaminated site is based on the application of pollutant atmospheric dispersion models. In the standard ASTM Risk-Based Corrective Action (RBCA-ASTM) procedure, this evaluation is carried out by coupling a one-dimensional Gaussian dispersion model to a simple dilution box model. In this work, the accuracy of this approach is examined by comparing the output obtained by the standard Gaussian box model with the results obtained with the non-steady-state Lagrangian puff dispersion model CALPUFF. A case study was considered, assuming the emission of benzene from a contaminated area of 200 × 200 m on flat terrain. The comparison of concentration profiles as a function of the distance from the source showed that the standard procedure overestimated concentrations by more than one order of magnitude. Two possible refinements to the standard RBCA-ASTM procedure were suggested. The first is the introduction of an equivalent mixing height for the application of the box model, calculated on the basis of the atmospheric stability class, land use typology, and dimension of the source. The second is the consideration of the wind distribution of the area. The introduction of these modifications allowed to reduce the discrepancy between the Gaussian box model and CALPUFF. This study also showed that the use of advanced dispersion models integrated with the risk calculation methodologies, allowed a detailed characterization of the risk in the area under examination, highlighting the most critical areas and comparing them with the presence of any sensitive receptors. 09-26-2022 <![CDATA[ <p>Human health risk assessment for off-site receptors located in the proximity of a contaminated site is based on the application of pollutant atmospheric dispersion models. In the standard ASTM Risk-Based Corrective Action (RBCA-ASTM) procedure, this evaluation is carried out by coupling a one-dimensional Gaussian dispersion model to a simple dilution box model. In this work, the accuracy of this approach is examined by comparing the output obtained by the standard Gaussian box model with the results obtained with the non-steady-state Lagrangian puff dispersion model CALPUFF. A case study was considered, assuming the emission of benzene from a contaminated area of 200 × 200 m on flat terrain. The comparison of concentration profiles as a function of the distance from the source showed that the standard procedure overestimated concentrations by more than one order of magnitude. Two possible refinements to the standard RBCA-ASTM procedure were suggested. The first is the introduction of an equivalent mixing height for the application of the box model, calculated on the basis of the atmospheric stability class, land use typology, and dimension of the source. The second is the consideration of the wind distribution of the area. The introduction of these modifications allowed to reduce the discrepancy between the Gaussian box model and CALPUFF. This study also showed that the use of advanced dispersion models integrated with the risk calculation methodologies, allowed a detailed characterization of the risk in the area under examination, highlighting the most critical areas and comparing them with the presence of any sensitive receptors.</p> ]]> Comparison of Gaussian and Lagrangian Puff Dispersion Models for the Risk Assessment of Receptors Nearby a Contaminated Site marco ravina iason verginelli renato baciocchi mariachiara zanetti doi: 10.2495/CMEM-V10-N3-260-270 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 260 10.2495/CMEM-V10-N3-260-270 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-260-270 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-237-259 Two approaches for formulating a computational Complex Variable Boundary Element Method (CVBEM) model are examined. In particular, this paper considers a collocation approach as well as a least squares approach. Both techniques are used to fit the CVBEM approximation function to given boundary conditions of benchmark boundary value problems (BVPs). Both modeling techniques provide satisfactory computational results, when applied to the demonstration problems, but differ in specific outcomes depending on the number of nodes used and the type of BVP being examined. Historically, the CVBEM has been implemented using the collocation approach. Therefore, the novelty of this work is in formulating the least squares approach and applying the least squares formulation to a Dirichlet BVP as well as a mixed BVP. This work does not claim that one technique should always be used over the other, but rather it seeks to demonstrate the viability of the least squares approach and assert that both techniques for determining the coefficients of the CVBEM approximation function should be considered during the modeling process. 09-26-2022 <![CDATA[ <p>Two approaches for formulating a computational Complex Variable Boundary Element Method (CVBEM) model are examined. In particular, this paper considers a collocation approach as well as a least squares approach. Both techniques are used to fit the CVBEM approximation function to given boundary conditions of benchmark boundary value problems (BVPs). Both modeling techniques provide satisfactory computational results, when applied to the demonstration problems, but differ in specific outcomes depending on the number of nodes used and the type of BVP being examined. Historically, the CVBEM has been implemented using the collocation approach. Therefore, the novelty of this work is in formulating the least squares approach and applying the least squares formulation to a Dirichlet BVP as well as a mixed BVP. This work does not claim that one technique should always be used over the other, but rather it seeks to demonstrate the viability of the least squares approach and assert that both techniques for determining the coefficients of the CVBEM approximation function should be considered during the modeling process.</p> ]]> A Least Squares Approach for Determining the Coefficients of the CVBEM Approximation Function bryce d. wilkins theodore v. hromadka ii doi: 10.2495/CMEM-V10-N3-237-259 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 237 10.2495/CMEM-V10-N3-237-259 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-237-259 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-224-236 Smoothing sequences in smoothed particle hydrodynamics (SPH) contain numerous discontinuities. In general, in science, discontinuities are well known to cause inaccuracy if smoothing is performed without taking the discontinuity into consideration, most commonly referred to as the Gibbs phenomenon. We found that $24 \%-27 \%$ of the fluid particles at any given time step have sequences containing one or more discontinuities in typical benchmark fluid problems. The effect of taking the discontinuities into consideration for the fluid particles that show coherent vorticity resulted typically in a $50 \%$ of change in particle movement compared to that particle's movement from its current time step to the next. First and second generation wavelets were used for discontinuity identification and vorticity analysis, respectively. Results of a sloshing tank case simulated by the SPH method were used for the analysis. 09-26-2022 <![CDATA[ <p>Smoothing sequences in smoothed particle hydrodynamics (SPH) contain numerous discontinuities. In general, in science, discontinuities are well known to cause inaccuracy if smoothing is performed without taking the discontinuity into consideration, most commonly referred to as the Gibbs phenomenon. We found that $24 \%-27 \%$ of the fluid particles at any given time step have sequences containing one or more discontinuities in typical benchmark fluid problems. The effect of taking the discontinuities into consideration for the fluid particles that show coherent vorticity resulted typically in a $50 \%$ of change in particle movement compared to that particle's movement from its current time step to the next. First and second generation wavelets were used for discontinuity identification and vorticity analysis, respectively. Results of a sloshing tank case simulated by the SPH method were used for the analysis.</p> ]]> Coherent Vorticity and Discontinuous Flow in Particle-Based Sph Modeling oddny h. brun joseph t. kider, jr. r. paul wiegand doi: 10.2495/CMEM-V10-N3-224-236 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 24 10.2495/CMEM-V10-N3-224-236 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-224-236 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-211-223 According to standards, a fundamental gear design parameter, which heavily influences the sizing of these mechanical components, is the gear tooth root bending strength. To establish this parameter in a reliable way, tests should be performed on running gears (RG) manufactured with the same material and heat treatments under investigation. However, it is common practice in industry and in academia to perform single tooth bending fatigue (STBF) tests, which, on the one hand, are simpler and cheaper to perform, on the other hand, the stress history $(\overline{\bar{\sigma}}(t))$ they induce is not identical to that obtained during RG meshing. Therefore, it is necessary to apply a correction coefficient ( $f_{\text {korr }}$ ) to translate data obtained via STBF in RG design data. In recent studies, a method to estimate $f_{\text {korr }}$ through the combination of finite element (FE) simulations and the implementation of multiaxial fatigue criteria (MFC) based on the critical plane concept has been proposed. This method consists of simulating through FE a gear geometry both in the RG load case and in the equivalent STBF condition. Through the load histories recorded on the nodes belonging to the critical area, it is possible, by implementing different MFC, to identify the most critical node and the relative Damage Parameter (DP). The ratio between the obtained critical DP of the STBF case and RG provides the value of $f_{\text {korr }}$. However, different MFC can lead to different results in terms of $f_{\text {korr }}$. This is because different MFC differs in the definition of the DP. More specifically, DPs are both functions of material properties, such as the fatigue limit of the material related to symmetric sinusoidal bending stresses $\left(\sigma_f\right)$ and the fatigue limit at sinusoidal cyclic torsional stresses $\left(\tau_f\right)$, and load-dependent characteristics. The goal of this paper is to investigate the effect of different material properties, i.e. $\sigma_f$ and $\tau_f$, on the estimation of $f_{\text {korr }}$ highlighting differences between the various MFC implemented, i.e. Findley, Matake, Papadopoulos, and Susmel et al. To this respect, the above-mentioned numerical method has been applied to a specific gear geometry whose material properties have been systematically varied. Results show that the criteria of Findley and Papadopoulus lead to very similar results and a monotonically increasing relationship between $f_{\text {korr }}$ and $\tau_f / \sigma_f$. A similar trend is observed for the Susmel et al. criterion but with higher value of $f_{\text {korr }}$ Differently, the criterion of Matake leads to a monotonic decreasing relationship between $f_{\text {korr }}$ and $\tau_f / \sigma_f$. 09-26-2022 <![CDATA[ <p><span style="font-family: Times New Roman, serif">According to standards, a fundamental gear design parameter, which heavily influences the sizing of these mechanical components, is the gear tooth root bending strength. To establish this parameter in a reliable way, tests should be performed on running gears (RG) manufactured with the same material and heat treatments under investigation. However, it is common practice in industry and in academia to perform single tooth bending fatigue (STBF) tests, which, on the one hand, are simpler and cheaper to perform, on the other hand, the stress history $(\overline{\bar{\sigma}}(t))$ they induce is not identical to that obtained during RG meshing. Therefore, it is necessary to apply a correction coefficient ( $f_{\text {korr }}$ ) to translate data obtained via STBF in RG design data. In recent studies, a method to estimate $f_{\text {korr }}$ through the combination of finite element (FE) simulations and the implementation of multiaxial fatigue criteria (MFC) based on the critical plane concept has been proposed. This method consists of simulating through FE a gear geometry both in the RG load case and in the equivalent STBF condition. Through the load histories recorded on the nodes belonging to the critical area, it is possible, by implementing different MFC, to identify the most critical node and the relative Damage Parameter (DP). The ratio between the obtained critical DP of the STBF case and RG provides the value of $f_{\text {korr }}$. However, different MFC can lead to different results in terms of $f_{\text {korr }}$. This is because different MFC differs in the definition of the DP. More specifically, DPs are both functions of material properties, such as the fatigue limit of the material related to symmetric sinusoidal bending stresses $\left(\sigma_f\right)$ and the fatigue limit at sinusoidal cyclic torsional stresses $\left(\tau_f\right)$, and load-dependent characteristics. The goal of this paper is to investigate the effect of different material properties, i.e. $\sigma_f$ and $\tau_f$, on the estimation of $f_{\text {korr }}$ highlighting differences between the various MFC implemented, i.e. Findley, Matake, Papadopoulos, and Susmel et al. To this respect, the above-mentioned numerical method has been applied to a specific gear geometry whose material properties have been systematically varied. Results show that the criteria of Findley and Papadopoulus lead to very similar results and a monotonically increasing relationship between $f_{\text {korr }}$ and $\tau_f / \sigma_f$. A similar trend is observed for the Susmel et al. criterion but with higher value of $f_{\text {korr }}$ Differently, the criterion of Matake leads to a monotonic decreasing relationship between $f_{\text {korr }}$ and $\tau_f / \sigma_f$.</span></p> ]]> Exploiting a Numerical Method to Translate Single Tooth Bending Fatigue Results into Meshing Gears Design Data: The Influence of Material Properties f. concli l. maccioni l. fraccaroli doi: 10.2495/CMEM-V10-N3-211-223 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 11 10.2495/CMEM-V10-N3-211-223 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-211-223 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-195-210 A very efficient method of condensing the steam in various industrial applications is the steam direct discharge into pools with subcooled water. This kind of condensation is known as Direct Contact Condensation (DCC), by providing high heat transfer and mass exchange capacity, the steam condenses quickly. In the past few decades, many experiments have been carried out on the submerged jets of non-condensable gases and pure steam in pools, supplying much information of interest, but efforts are still being made to obtain more information. In particular, the research of steam and non-condensable gas mixtures is of great interest to the chemical, energy, and nuclear industry. Consequently, this study investigates the discharge behavior of air-steam mixtures in a pool with subcooled water by direct visualization techniques using a high-speed camera. To know the behavior of the dimensionless momentum length, tests were carried out considering several initial discharge conditions such as nozzle diameter, percentage of mixture, and flow rates. After image acquisition, a series of complex processing, filtering, and post-processing procedures are applied using a subroutine in MATLAB. The momentum length of the jet was measured and found to be heavily influenced by the nozzle diameter, the jet velocity, and the mixture percentage. A correlation is obtained for the dimensionless momentum length of the horizontal jet that depends on the Froude and Mach numbers. 09-26-2022 <![CDATA[ <p>A very efficient method of condensing the steam in various industrial applications is the steam direct discharge into pools with subcooled water. This kind of condensation is known as Direct Contact Condensation (DCC), by providing high heat transfer and mass exchange capacity, the steam condenses quickly. In the past few decades, many experiments have been carried out on the submerged jets of non-condensable gases and pure steam in pools, supplying much information of interest, but efforts are still being made to obtain more information. In particular, the research of steam and non-condensable gas mixtures is of great interest to the chemical, energy, and nuclear industry. Consequently, this study investigates the discharge behavior of air-steam mixtures in a pool with subcooled water by direct visualization techniques using a high-speed camera. To know the behavior of the dimensionless momentum length, tests were carried out considering several initial discharge conditions such as nozzle diameter, percentage of mixture, and flow rates. After image acquisition, a series of complex processing, filtering, and post-processing procedures are applied using a subroutine in MATLAB. The momentum length of the jet was measured and found to be heavily influenced by the nozzle diameter, the jet velocity, and the mixture percentage. A correlation is obtained for the dimensionless momentum length of the horizontal jet that depends on the Froude and Mach numbers.</p> ]]> Experimental Characterization of the Dimensionless Momentum Length for Submerged Jet Discharges of Air-Steam Mixtures into Stagnant Water y. córdova d. blanco c. berna j. l. muñoz-cobo a. escrivá y. rivera doi: 10.2495/CMEM-V10-N3-195-210 International Journal of Computational Methods and Experimental Measurements 09-26-2022 International Journal of Computational Methods and Experimental Measurements 09-26-2022 2022 10 3 Article 195 10.2495/CMEM-V10-N3-195-210 https://www.acadlore.com/article/IJCMEM/2022_10_3/CMEM-V10-N3-195-210 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-93-103 Annular gas–liquid flows have been extensively studied over the years. However, the nonlinear behavior of the interface is still currently the subject of study by multiple researchers worldwide. The appearance of a liquid layer on the wall and its turbulent behavior support the heat exchange of multiple systems in the industrial field. Research in this area allows the optimization of these instal- lations as well as the analysis of possible safety problems if the liquid film disappears. This study first shows some of the most important findings obtained in the GEPELON experimental facility (GEneración de PElícula ONdulatoria or Wavy Film Generator). The facility was built in order to analyze the behavior of the liquid film in annular downward air–water flow. The experimental range of the inlet conditions is 800–8000 for the ReL and 0–110,000 for the Reg. Measurements for the meanfilm thickness show a fairly good agreement with the empirical correlations and the measurements ofother authors. One of the most demanded applications of this type of measurements is the validation of computational dynamics or CFD codes. Therefore, the experiment has been modeled using Ansys CFX software, and the simulation results have been compared with the experimental ones. This article outlines some of the reasons why two-phase flow simulations are currently challenging and how the codes are able to overcome them. Simulation predictions are fairly close to the experimental measurements, and the mean film thickness evolution when changing the boundary conditions also shows a good agreement. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Annular gas–liquid flows have been extensively studied over the years. However, the nonlinear behavior of the interface is still currently the subject of study by multiple researchers worldwide.</span><span> </span>The appearance of a liquid layer on the wall and its turbulent behavior support the heat exchange of multiple systems in the industrial field. Research in this area allows the optimization of these instal- lations as well as the analysis of possible safety problems if the liquid film disappears. This study<span> </span>first shows some of the most important findings obtained in the GEPELON experimental facility (GEneración de PElícula ONdulatoria or Wavy Film Generator). The facility was built in order to analyze the behavior of the liquid film in annular downward air–water flow. The experimental range of the inlet conditions is 800–8000 for the <em>Re<span style="color: rgb(35, 31, 32)">L </span></em><span style="color: rgb(35, 31, 32)">and 0–110,000 for the </span><em><span style="color: rgb(35, 31, 32)">Reg</span></em><span style="color: rgb(35, 31, 32)">. Measurements for the</span><span> </span>mean</p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">film thickness show a fairly good agreement with the empirical correlations and the measurements</span><span> </span>of</p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">other authors. One of the most demanded applications of this type of measurements is the validation of computational dynamics or CFD codes. Therefore, the experiment has been modeled using Ansys CFX software, and the simulation results have been compared with the experimental ones. This</span><span> </span>article outlines some of the reasons why two-phase flow simulations are currently challenging and how the codes are able to overcome them. Simulation predictions are fairly close to the experimental measurements, and the mean film thickness evolution when changing the boundary conditions also shows a good<span> </span>agreement.</p> ]]> Experimental Measurements and CFD Results of Liquid Film Thickness in Vertical Downward Air–Water Annular Flow y. rivera j.l. muñoz-cobo a. escrivá c. berna y. córdova doi: 10.2495/CMEM-V10-N2-93-103 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 2 Article 93 10.2495/CMEM-V10-N2-93-103 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-93-103 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-172-186 In this work, oblique wave scattering by a rectangular porous breakwater with slotted screens floating over a sill-type seabed is examined within the frame of linear wave-structure interaction theory. The Sollitt and Cross model is used to analyze the fluid motion inside the rectangular porous breakwater. In addition, a quadratic pressure jump condition on the slotted screens is adopted to include the effect of wave height on wave attenuation by the slotted screens. The associated physical problem is handled using an iterative boundary element method. Finally, the scattering coefficients such as the reflection, transmission, energy loss coefficients, and wave forces acting on the rectangular porous structure are analyzed for different wave conditions. The time-dependent displacement profiles for the various instants of time are provided. Further, the influence of different geometries of sill-type bottoms on wave scattering is analyzed. The study concludes that the wave forces on the rectangular structure attain their maximum when the distance between the slotted screen and the porous structure is an integral multiple of the wavelength associated with the incident wave for different submergence drafts. 05-17-2022 <![CDATA[ <p>In this work, oblique wave scattering by a rectangular porous breakwater with slotted screens floating over a sill-type seabed is examined within the frame of linear wave-structure interaction theory. The Sollitt and Cross model is used to analyze the fluid motion inside the rectangular porous breakwater. In addition, a quadratic pressure jump condition on the slotted screens is adopted to include the effect of wave height on wave attenuation by the slotted screens. The associated physical problem is handled using an iterative boundary element method. Finally, the scattering coefficients such as the reflection, transmission, energy loss coefficients, and wave forces acting on the rectangular porous structure are analyzed for different wave conditions. The time-dependent displacement profiles for the various instants of time are provided. Further, the influence of different geometries of sill-type bottoms on wave scattering is analyzed. The study concludes that the wave forces on the rectangular structure attain their maximum when the distance between the slotted screen and the porous structure is an integral multiple of the wavelength associated with the incident wave for different submergence drafts.</p> ]]> Oblique Wave Scattering by a Rectangular Porous Floating Breakwater with Slotted Screens Over a Sill-Type Seabed kottala panduranga santanu koley doi: 10.2495/CMEM-V10-N2-172-186 International Journal of Computational Methods and Experimental Measurements 05-17-2022 International Journal of Computational Methods and Experimental Measurements 05-17-2022 2022 10 2 Article 172 10.2495/CMEM-V10-N2-172-186 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-172-186 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-158-171 The process of developing a virtual replica of a physical asset usually involves using the best available values of the material and environment-related parameters essential to run the predictive simulation. The parameter values are further updated as necessary over time in response to the behaviour/conditions of physical assets and/or environment. This parametric calibration of the simulation models is usually made manually with trial-and-error using data obtained from sensors/manual survey readings of designated parts of the physical asset. Digital twining (DT) has provided a means by which validating data from the physical asset can be obtained in near real time. However, the process of calibration is time-consuming as it is manual, and as with each parameter guess during the trial, a simulation run is required. This is even more so when the running time of a single simulation is high enough, like hours or even days, and the model involves a significantly high number of parameters. To address these shortcomings, an experimental platform implemented with the integration of a simulator and scientific software is proposed. The scientific software within the platform also offers surrogate building support, where surrogates assist in the estimation/update of design parameters as an alternative to time-consuming predictive models. The proposed platform is demonstrated using BEASY, a simulator designed to predict protection provided by a cathodic protection (CP) system to an asset, with MATLAB as the scientific software. The developed setup facilitates the task of model validation and adaptation of the CP model by automating the process within a DT ecosystem and also offers surrogate-assisted optimisation for parameter estimation/updating. 05-17-2022 <![CDATA[ <p>The process of developing a virtual replica of a physical asset usually involves using the best available values of the material and environment-related parameters essential to run the predictive simulation. The parameter values are further updated as necessary over time in response to the behaviour/conditions of physical assets and/or environment. This parametric calibration of the simulation models is usually made manually with trial-and-error using data obtained from sensors/manual survey readings of designated parts of the physical asset. Digital twining (DT) has provided a means by which validating data from the physical asset can be obtained in near real time. However, the process of calibration is time-consuming as it is manual, and as with each parameter guess during the trial, a simulation run is required. This is even more so when the running time of a single simulation is high enough, like hours or even days, and the model involves a significantly high number of parameters. To address these shortcomings, an experimental platform implemented with the integration of a simulator and scientific software is proposed. The scientific software within the platform also offers surrogate building support, where surrogates assist in the estimation/update of design parameters as an alternative to time-consuming predictive models. The proposed platform is demonstrated using BEASY, a simulator designed to predict protection provided by a cathodic protection (CP) system to an asset, with MATLAB as the scientific software. The developed setup facilitates the task of model validation and adaptation of the CP model by automating the process within a DT ecosystem and also offers surrogate-assisted optimisation for parameter estimation/updating.</p> ]]> Surrogate-Assisted Parametric Calibration Using Design of Experiment Platform Within Digital Twinning madhu sudan sapkota edward apeh mark hadfield roya haratian robert adey john baynham doi: 10.2495/CMEM-V10-N2-158-171 International Journal of Computational Methods and Experimental Measurements 05-17-2022 International Journal of Computational Methods and Experimental Measurements 05-17-2022 2022 10 2 Article 158 10.2495/CMEM-V10-N2-158-171 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-158-171 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-146-157 Additive manufacturing (AM) is a more and more appreciated manufacturing technology. This growing interest is related to the high flexibility of this approach and its capability to produce any geometry, opening new possibilities. An example is the improvement of the system performances exploiting lattice and reticular in substitution to the traditional solid design. Despite this premise, in real applications, part of the benefits is lost due to the inferior performances of the AM steels and the higher costs of additive manufacturing. In this scenario, the mechanical properties of a 17-4 PH SS produced via additive technology were characterized with experimental tests. The results were compared with data concerning the cast material. In this way, it was possible to execute a quantitative evaluation of the performance reduction. Three components, such as a hip prosthesis, a blow plastic bottle die, and an automotive gear, were chosen as representative examples. These three mechanical components are typically produced in quite different batch sizes. The hip prosthesis, the blow plastic bottle die, and the automotive gear were redesigned (design for AM) via a finite element (FE) approach. The new designs fulfill the original requirements in terms of strength showing however improved inertial properties. The original and new designs were exploited to quantify the benefits of introducing AM in different applications. 05-17-2022 <![CDATA[ <p><span style="color: rgb(35, 31, 32); font-family: Times New Roman, serif">Additive manufacturing (AM) is a more and more appreciated manufacturing technology. This growing</span><span> </span>interest<span> </span>is<span> </span>related<span> </span>to<span> </span>the<span> </span>high<span> </span>flexibility<span> </span>of<span> </span>this<span> </span>approach<span> </span>and<span> </span>its<span> </span>capability<span> </span>to<span> </span>produce<span> </span>any<span> </span>geometry, opening new possibilities. An example is the improvement of the system performances exploiting lattice and reticular in substitution to the traditional solid design. Despite this premise, in real applications, part of the benefits is lost due to the inferior performances of the AM steels and the higher costs of additive manufacturing. In this scenario, the mechanical properties of a 17-4 PH SS produced via additive technology were characterized with experimental tests. The results were compared with data concerning the cast material. In this way, it was possible to execute a quantitative evaluation of the performance reduction. Three components, such as a hip prosthesis, a blow plastic bottle die, and an automotive gear, were chosen as representative examples. These three mechanical components are typically<span> </span>produced<span> </span>in<span> </span>quite<span> </span>different<span> </span>batch<span> </span>sizes.<span> </span>The<span> </span>hip<span> </span>prosthesis,<span> </span>the<span> </span>blow<span> </span>plastic<span> </span>bottle<span> </span>die,<span> </span>and<span> </span>the automotive<span> </span>gear<span> </span>were<span> </span>redesigned<span> </span>(design<span> </span>for<span> </span>AM)<span> </span>via<span> </span>a<span> </span>finite<span> </span>element<span> </span>(FE)<span> </span>approach.<span> </span>The<span> </span>new<span> </span>designs fulfill the original requirements in terms of strength showing however improved inertial properties. The original and new designs were exploited to quantify the benefits of introducing AM in different applications.</p> ]]> Design for Additive Manufacturing – Material Characterization and Geometrical Optimization franco concli margherita molinaro doi: 10.2495/CMEM-V10-N2-146-157 International Journal of Computational Methods and Experimental Measurements 05-17-2022 International Journal of Computational Methods and Experimental Measurements 05-17-2022 2022 10 2 Article 146 10.2495/CMEM-V10-N2-146-157 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-146-157 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-131-145 This paper explores the practical possibility of using a magnetic field to orient steel fibres in a fresh concrete matrix. This process leads to preferential orientation, which increases the desired mechanical properties of the hardened material. In general, this paper focuses on the technical aspects of the orientation process and identifies key areas, such as the strength and shape of the magnetic field, velocity of the sample's passage through the magnetic field and viscosity of the materials. A prototype orienting apparatus was constructed with different permanent magnet systems to evaluate their performance. An ultrasound gel and a cementitious matrix were used as a medium for the fibres. Numerical simulations were created to further understand the effects of the magnetic field's strength and shape. The final orientation of the fibres in hardened concrete was evaluated using Q factor measurements, X-ray scans and bending tests. A sufficiently strong magnetic field can be used to orient fibres in fresh concrete. 05-17-2022 <![CDATA[ <p>This paper explores the practical possibility of using a magnetic field to orient steel fibres in a fresh concrete matrix. This process leads to preferential orientation, which increases the desired mechanical properties of the hardened material. In general, this paper focuses on the technical aspects of the orientation process and identifies key areas, such as the strength and shape of the magnetic field, velocity of the sample's passage through the magnetic field and viscosity of the materials. A prototype orienting apparatus was constructed with different permanent magnet systems to evaluate their performance. An ultrasound gel and a cementitious matrix were used as a medium for the fibres. Numerical simulations were created to further understand the effects of the magnetic field's strength and shape. The final orientation of the fibres in hardened concrete was evaluated using Q factor measurements, X-ray scans and bending tests. A sufficiently strong magnetic field can be used to orient fibres in fresh concrete.</p> ]]> Applicability of Magnetic Field for Directed Orientation of Steel Fibres in High-Performing Cementitious Composites kristýna takáčová karel künzel václav papež petr konrád michal mára jindřich fornŭsek přemysl kheml radoslav sovják doi: 10.2495/CMEM-V10-N2-131-145 International Journal of Computational Methods and Experimental Measurements 05-17-2022 International Journal of Computational Methods and Experimental Measurements 05-17-2022 2022 10 2 Article 131 10.2495/CMEM-V10-N2-131-145 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-131-145 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-117-130 The finite element method is used for numerical simulation analysis to explore the settlement characteristics of widened subgrade under the influence of different working conditions and factors. The research results show that at the end of the construction period, the maximum total settlement of the subgrade surface of the project of simultaneous widening and raising of the original subgrade is 1.97 cm , the maximum differential settlement of the subgrade surface is 0.21 cm , and the cross slope of the road arch increases by 1.4%. The maximum total settlement of the subgrade surface of the project of only widening of the original subgrade is 2.35 cm , which is an increase of 19.3% compared with the maximum total settlement of the subgrade surface of the project of simultaneous widening and raising of the original subgrade. The total settlement of the subgrade surface under the two working conditions varies with the change of filling materials and increases with the width, height, and slope ratio. When the width increases from 3.5 to 14 m , the maximum uncoordinated deformation of the subgrade surface of the project of simultaneous widening and raising of the original subgrade is increased from 0.54 to 1.31 cm , and the value of the subgrade surface settlement curvature of the splicing area for the project of only widening of the original subgrade is increased from 0.13 to 0.97 . The obtained results can provide a reference for subgrade widening projects in the future. 05-17-2022 <![CDATA[ <p>The finite element method is used for numerical simulation analysis to explore the settlement characteristics of widened subgrade under the influence of different working conditions and factors. The research results show that at the end of the construction period, the maximum total settlement of the subgrade surface of the project of simultaneous widening and raising of the original subgrade is 1.97 cm , the maximum differential settlement of the subgrade surface is 0.21 cm , and the cross slope of the road arch increases by 1.4%. The maximum total settlement of the subgrade surface of the project of only widening of the original subgrade is 2.35 cm , which is an increase of 19.3% compared with the maximum total settlement of the subgrade surface of the project of simultaneous widening and raising of the original subgrade. The total settlement of the subgrade surface under the two working conditions varies with the change of filling materials and increases with the width, height, and slope ratio. When the width increases from 3.5 to 14 m , the maximum uncoordinated deformation of the subgrade surface of the project of simultaneous widening and raising of the original subgrade is increased from 0.54 to 1.31 cm , and the value of the subgrade surface settlement curvature of the splicing area for the project of only widening of the original subgrade is increased from 0.13 to 0.97 . The obtained results can provide a reference for subgrade widening projects in the future.</p> ]]> Analysis of Influencing Factors on Settlement of Widened Subgrade Based on Differences in Working Conditions yang liang xu wenyuan li keke doi: 10.2495/CMEM-V10-N2-117-130 International Journal of Computational Methods and Experimental Measurements 05-17-2022 International Journal of Computational Methods and Experimental Measurements 05-17-2022 2022 10 2 Article 117 10.2495/CMEM-V10-N2-117-130 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-117-130 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-104-116 Precise prediction of air quality in a street canyon under diverse conditions could be established through the comprehensive validation of velocity of wind profiles and the concentration distribu- tion of pollutants. In this study, a two-step approach was developed using Computational Fluid Dynamics simulations. The first step involved the validation of wind velocity profiles obtained using wind tunnel experimental measurements of an isolated street canyon discussed in ref. [1], while the second step focused on the validation of dispersion of pollutants from wind tunnel mea- surements discussed in ref. [2] conducted on isolated and urban street canyons. The wind velocity profiles obtained at five distinct vertical planes between the leeward and windward walls in the wind tunnel study [1] were validated by simulating the 2D cross-section of the entire wind tunnel domain with high accuracies; R2 values of 0.931–0.986 were obtained across the canyon depth. The concentration distribution of the pollutant in the wind tunnel study [2] were validated for a range of velocities (0.5, 1, 2 and 4 m/s) using both 2D and 3D models. A verification of the Reyn- olds independent nature of the flow was performed by comparing the wind tunnel and street scale models and suitability of employing K-e turbulence model with Enhanced Wall Treatment and K-ε Low Reynolds Number Model for the wind tunnel scale, and Standard Wall Functions for the street scale were observed. A 2D simulation of urban street canyon flow representing the whole wind tunnel cross-section in the flow direction was also studied to observe repetitive flow nature and thereby a potential to employ fully developed flow conditions for the same. The urban street canyon flow is established through the means of fully developed periodic flow profiles, which inherently restricts the additional mass sources in the flow domain. The emission scenario in the fully developed flow was captured by means of flow profile mapping at the upwind edge of the leeward building. To estimate the minimum number of downwind canyons required to keep up the fully developed flow profile at the target street canyon, a parameterization of the same was per- formed. Finally, the validation of the concentration profiles was obtained with parameterization of the Schmidt number, and an optimal Schmidt number was obtained in the case of using Realizable K-e turbulence model. The developed and validated methodology provides a robust and efficient means of modelling air pollution dispersion in the isolated and urban street canyons for future research investigations. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">Precise prediction of air </span><span>quality </span>in a <span>street </span>canyon <span>under </span>diverse <span>conditions could </span>be <span>established through </span>the <span>comprehensive validation </span>of <span>velocity </span>of <span>wind profiles </span>and the <span>concentration distribu- tion </span>of <span>pollutants. </span>In <span>this </span>study, a <span>two-step approach </span>was developed <span>using Computational Fluid Dynamics simulations. </span>The first <span>step </span>involved the <span>validation </span>of <span>wind velocity profiles obtained using wind tunnel experimental measurements </span>of an <span>isolated street </span>canyon <span>discussed </span>in <span>ref. [1], while </span>the <span>second step focused </span>on the <span>validation </span>of <span>dispersion </span>of <span>pollutants from wind tunnel mea- surements discussed </span>in <span>ref. </span>[2] <span>conducted </span>on <span>isolated </span>and <span>urban street canyons. </span>The <span>wind velocity profiles obtained </span>at five <span>distinct vertical planes between </span>the leeward and <span>windward </span>walls in <span>the wind tunnel study </span>[1] <span>were validated </span>by <span>simulating </span>the 2D <span>cross-section </span>of the <span>entire wind tunnel domain with high accuracies; </span>R<span style="color: rgb(35, 31, 32)">2 values of </span><span>0.931–0.986 were obtained across </span>the canyon<span> depth. </span>The <span>concentration distribution </span>of the <span>pollutant </span>in the <span>wind tunnel study </span>[2] <span>were validated </span>for a <span>range </span>of <span>velocities (0.5, </span>1, 2 and 4 <span>m/s) using both </span>2D and 3D <span>models. </span>A <span>verification </span>of the Reyn- <span>olds independent nature </span>of the flow was <span>performed </span>by <span>comparing </span>the <span>wind tunnel </span>and <span>street scale models </span>and <span>suitability </span>of <span>employing </span>K-<span style="color: rgb(35, 31, 32); font-family: Symbol">e</span><span> turbulence model with Enhanced </span>Wall Treatment<span> and </span>K-ε Low <span>Reynolds Number Model </span>for the <span>wind tunnel scale, </span>and <span>Standard </span>Wall <span>Functions </span>for <span>the street scale were observed. </span>A 2D <span>simulation </span>of <span>urban street </span>canyon flow <span>representing </span>the <span>whole wind tunnel cross-section </span>in the flow <span>direction </span>was <span>also studied </span>to <span>observe </span>repetitive flow <span>nature </span>and <span>thereby </span>a <span>potential </span>to <span>employ fully </span>developed flow <span>conditions </span>for the <span>same. </span>The <span>urban street </span>canyon flow is <span>established through </span>the <span>means </span>of <span>fully </span>developed <span>periodic </span>flow <span>profiles, which inherently restricts </span>the <span>additional mass sources </span>in the flow <span>domain. </span>The <span>emission scenario </span>in <span>the fully </span>developed flow was <span>captured </span>by <span>means </span>of flow profile <span>mapping </span>at the <span>upwind edge </span>of <span>the </span>leeward <span>building. To estimate </span>the <span>minimum number </span>of <span>downwind canyons required </span>to keep up <span>the fully </span>developed flow profile at the target <span>street canyon, </span>a <span>parameterization </span>of the <span>same </span>was per- <span>formed. </span>Finally, the <span>validation </span>of the <span>concentration profiles </span>was <span>obtained with parameterization of </span>the <span>Schmidt </span>number, and an <span>optimal Schmidt number </span>was <span>obtained </span>in the <span>case </span>of <span>using Realizable </span>K-<span style="color: rgb(35, 31, 32); font-family: Symbol">e</span><span style="color: rgb(35, 31, 32)"> </span><span>turbulence model. </span>The developed and <span>validated methodology provides </span>a robust and <span>efficient means </span>of <span>modelling </span>air <span>pollution dispersion </span>in the <span>isolated </span>and <span>urban street canyons </span>for <span>future research investigations.</span></p> ]]> Development And Validation of a Computational Fluid Dynamics Modelling Methodology for Isolated and Urban Street Canyon Configurations Using Wind Tunnel Measurements madhavan vasudevan bidroha basu francesco pilla aonghus mcnabola doi: 10.2495/CMEM-V10-N2-104-116 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 2 Article 104 10.2495/CMEM-V10-N2-104-116 https://www.acadlore.com/article/IJCMEM/2022_10_2/CMEM-V10-N2-104-116 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-74-84 Today, the assessment of the safety of long-span bridges relies on wind tunnel testing, although CFD methods are steadily penetrating in research and industrial practice. The evaluation of force coefficients and flutter derivatives presents multiple uncertainties, related with inflow boundary conditions, mechanical and mathematical models or parameter choices. In this work, we focus on one single uncertainty parameter that is the wind angle of incidence, which has been studied for instance in building aerodynamics. The assumed input probability density function adopted for the angle of incidence has been uniform in the range of angles considered. Uncertainty quantification tools, such as the stochastic collocation method, are used to propagate the uncertainty in the wind angle of attack for the force coefficients and flutter derivatives of a twin-box bridge deck. To this end, 5 2D URANS static simulations have been completed to quantify the uncertainty in the force coefficients, and 70 2D URANS forced oscillation simulations have been required to obtain the stochastic mean and standard deviation of the flutter derivatives, applying nested Clenshaw–Curtis quadrature points at level 3. It has been found that for the force coefficients, the stochastic standard deviation has been up to 0.032 for the lift coefficient. Furthermore, for the aeroelastic response, the flutter derivatives H1*, A1*, H2* and A2* show important stochastic standard deviations relative to the stochastic mean value for reduced velocities above 10. <![CDATA[ <p>Today, the assessment of the safety of long-span bridges relies on wind tunnel testing, although CFD methods are steadily penetrating in research and industrial practice. The evaluation of force coefficients and flutter derivatives presents multiple uncertainties, related with inflow boundary conditions, mechanical and mathematical models or parameter choices. In this work, we focus on one single uncertainty parameter that is the wind angle of incidence, which has been studied for instance in building aerodynamics. The assumed input probability density function adopted for the angle of incidence has been uniform in the range of angles considered. Uncertainty quantification tools, such as the stochastic collocation method, are used to propagate the uncertainty in the wind angle of attack for the force coefficients and flutter derivatives of a twin-box bridge deck. To this end, 5 2D URANS static simulations have been completed to quantify the uncertainty in the force coefficients, and 70 2D URANS forced oscillation simulations have been required to obtain the stochastic mean and standard deviation of the flutter derivatives, applying nested Clenshaw–Curtis quadrature points at level 3. It has been found that for the force coefficients, the stochastic standard deviation has been up to 0.032 for the lift coefficient. Furthermore, for the aeroelastic response, the flutter derivatives H1*, A1*, H2* and A2* show important stochastic standard deviations relative to the stochastic mean value for reduced velocities above 10.</p> ]]> Uncertainty Quantification of Aerodynamic and Aeroelastic Responses of a Short-Gap Twin-Box Deck Depending on the Wind Angle of Attack giuseppe g. lobriglio antonio j. álvarez felix nieto santiago hernández josé á. jurado doi: 10.2495/CMEM-V10-N1-74-84 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 74 10.2495/CMEM-V10-N1-74-84 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-74-84 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-62-73 Generally, droplet velocity in liquid-liquid two-phase flow in microchannel is obtained via droplet displacement and time interval precise determination in sequential photos/videos. The precision is tightly related to shutter speed of the camera. In this paper, a novel method called direct image method is proposed to predict the droplet velocity. The droplet velocity can be easily obtained in one snapshot by this method. In order to validate the accuracy of this novel method, experiments are carried out in water-butanol, water-hexane and water-oil (Mogul Trafo CZ-A Paramo) systems. The droplet velocity predicted by this direct image method shows a good agreement with the experimental data. Although the assumptions which has been used to determine the droplet velocity still need to be improved, this method can be useful in industrial application. <![CDATA[ <p>Generally, droplet velocity in liquid-liquid two-phase flow in microchannel is obtained via droplet displacement and time interval precise determination in sequential photos/videos. The precision is tightly related to shutter speed of the camera. In this paper, a novel method called direct image method is proposed to predict the droplet velocity. The droplet velocity can be easily obtained in one snapshot by this method. In order to validate the accuracy of this novel method, experiments are carried out in water-butanol, water-hexane and water-oil (Mogul Trafo CZ-A Paramo) systems. The droplet velocity predicted by this direct image method shows a good agreement with the experimental data. Although the assumptions which has been used to determine the droplet velocity still need to be improved, this method can be useful in industrial application.</p> ]]> Determination of Droplet Velocity in Square Microchannel jin-yuan qian xiao-juan li zan wu zhen cao bengt sunden doi: 10.2495/CMEM-V10-N1-62-73 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 62 10.2495/CMEM-V10-N1-62-73 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-62-73 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-50-61 During coagulation, particles with a flocculent shape and an irregular structure are formed in water. In the model sedimentation water presented in this study, three fractions of particles were distinguished and the method of calculating the sedimentation rate presented. Each fraction sediments in a different way due to different forces acting on particles of different shapes. The particles of fraction I are similar in shape to spherical particles, the particles of fraction II are non-spherical particles, and the particles of fraction III are porous agglomerates, for which the formula for liquid flow through a porous bed has been adopted. For the proposed theoretical sinking model for three types of suspensions composed of particles of each fraction, experimental tests were carried out, which confirmed the model predictions. The results for the sedimentation velocity of the monodisperse suspension of fractions I, II, and III are very similar to predictions: for fraction I, the discrepancy between theoretical and experimental results was 9%; for fraction II, 11%; and for fraction III, 17%. This proves a correctly selected methodology, and the proposed model can be used to calculate the sedimentation velocity of monodisperse suspen- sions of various shapes. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">During coagulation, particles with a flocculent shape and an irregular structure are formed in water. </span><span>In </span>the model sedimentation water presented in this study, three fractions of particles were distinguished and the method of calculating the sedimentation rate presented. Each fraction sediments in a different way<span> </span>due<span> </span>to<span> </span>different<span> </span>forces<span> </span>acting<span> </span>on<span> </span>particles<span> </span>of<span> </span>different<span> </span>shapes.<span> </span>The<span> </span>particles<span> </span>of<span> </span>fraction<span> </span>I<span> </span>are<span> </span>similar in shape to spherical particles, the particles of fraction II are non-spherical particles, and the particles of<span> </span>fraction<span> </span>III<span> </span>are<span> </span>porous<span> </span>agglomerates,<span> </span>for<span> </span>which<span> </span>the<span> </span>formula<span> </span>for<span> </span>liquid<span> </span>flow<span> </span>through<span> </span>a<span> </span>porous<span> </span>bed<span> </span>has been adopted. For the proposed theoretical sinking model for three types of suspensions composed of particles of each fraction, experimental tests were carried out, which confirmed the model predictions. The results for the sedimentation velocity of the monodisperse suspension of fractions I, II, and III are very similar to predictions: for fraction I, the discrepancy between theoretical and experimental results was 9%; for fraction II, 11%; and for fraction III, 17%. This proves a correctly selected methodology, and the proposed model can be used to calculate the sedimentation velocity of monodisperse suspen- sions of various shapes.</p> ]]> Modeling of the Sedimentation Process of Monodisperse Suspension rząsa mariusz łukasiewicz ewelina doi: 10.2495/CMEM-V10-N1-50-61 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 50 10.2495/CMEM-V10-N1-50-61 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-50-61 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-38-49 The numerical treatment of industrial and environmental problems, involving multiphase flows with particles, has gained significant interest of researchers over the recent years. For large-scale problems, involving an increased number of particles, authors mostly rely on the Lagrangian particle tracking approach, where particle-fluid interaction is generally unresolved and has to be modelled. Significant research efforts have already been made in developing various models to predict particle-fluid interac- tion, where applications involving complex particle shapes are especially intriguing. In the majority of encountered problems, particle dynamics is primarily governed by drag forces exerted on the particle by the carrier fluid. Following from that it is unsurprising that precise particle trajectories can only be established from accurate particle drag prediction model. In this context, we present a steady-state particle-resolved numerical model, based on OpenFOAM, for numerical drag prediction of superel- lipsoidal particles in Stokesian flow regime. The idea behind particle-resolved model is to benefit from multi parameter drag prediction, which considers not only the flow regime and particle size but also detailed geometric features (expressed by four independent parameters) and particle orientation. The proposed numerical model will also benefit from a parametric geometry formulation, which will allow to evaluate the drag force for the entire range of particle shapes, offered by the superellipsoidal param- etrization. For a vast amount of non-spherical particles, this significantly improves the accuracy of the predicted drag force in comparison to traditional drag models, which do not account for the entire range of influencing factors. The numerical model is further supported by an automated parametric mesh generation algorithm, which makes it possible to autonomously address the full range of particle orientations in parallel. The parametric algorithm also enables the specification of various flow regimes, which are captured in the analysis. Thus, with a single set of input parameters, one can quickly obtain the drag function for given particle shape, with respect to the entire range of orientations and flow regimes. The authors believe that the proposed solution will significantly reduce the effort to obtain an accurate drag model for a vast amount of non-spherical particle shapes. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The numerical treatment of industrial and environmental problems, involving multiphase flows with particles, has gained significant interest of researchers over the recent years. For large-scale problems, involving an increased number of particles, authors mostly rely on the Lagrangian particle tracking approach, where particle-fluid interaction is generally unresolved and has to be modelled. Significant research efforts have already been made in developing various models to predict particle-fluid interac- tion, where applications involving complex particle shapes are especially intriguing. In the majority of encountered problems, particle dynamics is primarily governed by drag forces exerted on the particle by the carrier fluid. Following from that it is unsurprising that precise particle trajectories can only</span><span> </span>be established from accurate particle drag prediction model. In this context, we present a steady-state particle-resolved numerical model, based on OpenFOAM, for numerical drag prediction of superel- lipsoidal<span> </span>particles<span> </span>in<span> </span>Stokesian<span> </span>flow<span> </span>regime.<span> </span>The<span> </span>idea<span> </span>behind<span> </span>particle-resolved<span> </span>model<span> </span>is<span> </span>to<span> </span>benefit<span> from </span>multi parameter drag prediction, which considers not only the flow regime and particle size but also detailed geometric features (expressed by four independent parameters) and particle orientation. <span>The </span>proposed numerical model will also benefit from a parametric geometry formulation, which will <span>allow </span>to evaluate the drag force for the entire range of particle shapes, offered by the superellipsoidal<span> </span>param- etrization. For a vast amount of non-spherical particles, this significantly improves the accuracy of<span> </span>the predicted drag force in comparison to traditional drag models, which do not account for the entire range of influencing factors. The numerical model is further supported by an automated parametric mesh generation algorithm, which makes it possible to autonomously address the full range of particle orientations<span> </span>in<span> </span>parallel.<span> </span>The<span> </span>parametric<span> </span>algorithm<span> </span>also<span> </span>enables<span> </span>the<span> </span>specification<span> </span>of<span> </span>various<span> </span>flow<span> </span>regimes, which are captured in the analysis. Thus, with a single set of input parameters, one can quickly <span>obtain </span>the drag function for given particle shape, with respect to the entire range of orientations and flow regimes. The authors believe that the proposed solution will significantly reduce the effort to obtain<span> </span>an accurate drag model for a vast amount of non-spherical particle shapes.</p> ]]> Numerical Drag and Lift Prediction Framework for Superellipsoidal Particles in Multiphase Flows mitja štrakl jana wedel paul steinmann matjaž hriberšek jure ravnik doi: 10.2495/CMEM-V10-N1-38-49 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 38 10.2495/CMEM-V10-N1-38-49 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-38-49 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-26-37 The presence of intermittent flow regime such as slug flow could cause issues to oil-gas well pipe- line-riser structures due to large fluctuations in pressure, leading to the production rate reduction and damage in the pipe structure. Monitoring multiphase flow regimes in production pipe systems is thus important. There are nowadays increasing use of multiphase flowmeter (MPFM) for well production flowrate metering. The associated phase fraction and flowrate measurement sensors in MPFMs could be potentially employed for multiphase-flow regime detection with no additional component required. In this study, a machine learning model is proposed to infer multiphase-flow regime from the measure- ments of a vertically installed gamma-ray and Venturi-based MPFM. Flow loop tests have been carried out at Singapore Well Testing Center with flows of various flow regimes observed at the horizontal inlet pipe section, such as dispersed bubbly, stratified, intermittent (slug) and annular flow regimes. The flow regime has been determined by visualization from a side glass in the flow loop pipe section and from real-time images reconstructed by an electrical-capacitance tomography system. The MPFM real-time measurements and derived or calculated data (such as Venturi differential pressure and gamma-ray mixture density) are then used as machine learning training data, with the flow regimes to be the train- ing target. Various machine learning methods have been experimented, such as convolutional neural network (CNN), long short-term memory (LSTM) and CNN-LSTM. It has been found that LSTM method with regularization, balancing and logarithmic normalization of the calculated parameters can achieve the highest accuracy on flow regime prediction (99.6%). This study is the first attempt to pre- dict flow regime at horizontal entrance section upstream of an MPFM with measurements made at a vertical Venturi throat section. The study also proves that flow regime could be accurately predicted by a gamma-ray and Venturi-based MPFM. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The presence of intermittent flow regime such as slug flow could cause issues to oil-gas well </span><span>pipe- </span>line-riser structures due to large fluctuations in pressure, leading to the production rate reduction <span>and </span>damage in the pipe structure. Monitoring multiphase flow regimes in production pipe systems is <span>thus </span>important. There are nowadays increasing use of multiphase flowmeter (MPFM) for well production flowrate metering. The associated phase fraction and flowrate measurement sensors in MPFMs <span>could </span>be potentially employed for multiphase-flow regime detection with no additional component required. In<span> </span>this<span> </span>study,<span> </span>a<span> </span>machine<span> </span>learning<span> </span>model<span> </span>is<span> </span>proposed<span> </span>to<span> </span>infer<span> </span>multiphase-flow<span> </span>regime<span> </span>from<span> </span>the<span> </span>measure- ments<span> </span>of<span> </span>a<span> </span>vertically<span> </span>installed<span> </span>gamma-ray<span> </span>and<span> </span>Venturi-based<span> </span>MPFM.<span> </span>Flow<span> </span>loop<span> </span>tests<span> </span>have<span> </span>been<span> </span>carried out<span> </span>at<span> </span>Singapore<span> </span>Well<span> </span>Testing<span> </span>Center<span> </span>with<span> </span>flows<span> </span>of<span> </span>various<span> </span>flow<span> </span>regimes<span> </span>observed<span> </span>at<span> </span>the<span> </span>horizontal<span> inlet </span>pipe<span> </span>section,<span> </span>such<span> </span>as<span> </span>dispersed<span> </span>bubbly,<span> </span>stratified,<span> </span>intermittent<span> </span>(slug)<span> </span>and<span> </span>annular<span> </span>flow<span> </span>regimes.<span> </span>The<span> </span>flow regime has been determined by visualization from a side glass in the flow loop pipe section and <span>from </span>real-time images reconstructed by an electrical-capacitance tomography system. The MPFM real-time measurements and derived or calculated data (such as Venturi differential pressure and gamma-ray mixture density) are then used as machine learning training data, with the flow regimes to be the <span>train- </span>ing target. Various machine learning methods have been experimented, such as convolutional neural network (CNN), long short-term memory (LSTM) and CNN-LSTM. It has been found that LSTM method with regularization, balancing and logarithmic normalization of the calculated parameters can achieve the highest accuracy on flow regime prediction (99.6%). This study is the first attempt to pre- dict flow regime at horizontal entrance section upstream of an MPFM with measurements made at a vertical<span> </span>Venturi<span> </span>throat<span> </span>section.<span> </span>The<span> </span>study<span> </span>also<span> </span>proves<span> </span>that<span> </span>flow<span> </span>regime<span> </span>could<span> </span>be<span> </span>accurately<span> </span>predicted<span> by </span>a gamma-ray and Venturi-based MPFM.</p> ]]> Flow Regime Detection Using Gamma-Ray-Based Multiphase Flowmeter: A Machine Learning Approach jian hua zhu ritesh munjal ani sivaram santhiyapillai rajeevan paul jing tian guillaume jolivet doi: 10.2495/CMEM-V10-N1-26-37 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 26 10.2495/CMEM-V10-N1-26-37 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-26-37 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-13-25 In recent decades, green roofs are encouraged as effective tools of sustainable urban drainage system for stormwater management. They contribute to the reduction of runoff peak flows and volume dis- charges to sewer systems. Green roof reliability in stormwater control is mainly a function of storage capacity, given by the growing medium and the drainage layers. While the thickness of this last layer is usually defined by standards, the growing medium thickness strictly depends on vegetation type and rainfall regime. This paper presents an analytical probabilistic approach to evaluate this thickness as a function of the reliability of green roofs in term of runoff reduction. The possibility of pre-filling from previous events was also considered, by mean of chained rainfall events. The proposed model has the advantage to combine the simplicity of design methods with the accuracy of continuous simulation.The proposed equations were validated by an application to a case study in Milano, Italy. Monthly analyses were carried out to highlight monthly differences in roof operation due to rainfall distribution and evapotranspiration rate all along the year. Results showed a good agreement with those obtained by the continuous simulation. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">In recent decades, green roofs are encouraged as effective tools of sustainable urban drainage system for stormwater management. They contribute to the reduction of runoff peak flows and volume dis- charges to sewer systems. Green roof reliability in stormwater control is mainly a function of storage capacity, given by the growing medium and the drainage layers. While the thickness of this last layer is usually defined by standards, the growing medium thickness strictly depends on vegetation type</span><span> </span>and rainfall regime. This paper presents an analytical probabilistic approach to evaluate this thickness as a function of the reliability of green roofs in term of runoff reduction. The possibility of pre-filling <span>from </span>previous events was also considered, by mean of chained rainfall events. The proposed model has the advantage to combine the simplicity of design methods with the accuracy of continuous simulation.</p><p style="text-align: justify"><span style="color: rgb(35, 31, 32)">The proposed equations were validated by an application to a case study in Milano, Italy. Monthly analyses were carried out to highlight monthly differences in roof operation due to rainfall distribution and evapotranspiration rate all along the year. Results showed a good agreement with those obtained by the continuous simulation.</span></p> ]]> Probabilistic Estimation of Runoff from Green Roofs anita raimondi mariana marchioni umberto sanfilippo fernando ferreira stroppa gianfranco becciu doi: 10.2495/CMEM-V10-N1-13-25 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 13 10.2495/CMEM-V10-N1-13-25 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-13-25 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-1-12 The preservation of the cultural heritage is a current and challenging issue for the sustainable devel- opment of countries, such is the case in the European Union. Seville is a Spanish city located in the southern Iberian Peninsula, and it is well-known for the importance of its cultural heritage. It is one of the main sources for its economic growth, employment and cultural development. The Giralda tower of the Cathedral of Seville is its most representative building. It has been declared as World Heritage Site by the UNESCO due to its patrimonial value. The Giralda was constructed in 1384 as the Aljama of the major mosque of Seville. However, it has undergone different construction phases over time. One of the most relevant modifications was the addition of the bell tower designed by the architect Hernán Ruíz in the Renaissance. Moreover, the tower has been affected by several historic earthquakes. The goal of this study is to define the geotechnical profile of the soil under the tower and to analyse its settlements. This study will focus on the several modifications that the building has suffered throughout its history. Moreover, it will properly and exhaustively characterise the foundation, which has not been carried out to date. To do so, the geotechnical profile has been defined accurately with the information of the boreholes drilled at its base. Then, finite elements have been used to model the different load phases, which correspond to the different construction phases. Finally, this analysis has shown a great agree- ment between the settlements of the tower and its real top displacements. <![CDATA[ <p><span style="color: rgb(35, 31, 32)">The preservation of the cultural heritage is a current and challenging issue for the sustainable devel- opment of countries, such is the case in the European Union. Seville is a Spanish city located in </span><span>the </span>southern Iberian Peninsula, and it is well-known for the importance of its cultural heritage. It is one of the<span> </span>main<span> </span>sources<span> </span>for<span> </span>its<span> </span>economic<span> </span>growth,<span> </span>employment<span> </span>and<span> </span>cultural<span> </span>development.<span> </span>The<span> </span>Giralda<span> </span>tower<span> of </span>the Cathedral of Seville is its most representative building. It has been declared as World Heritage<span> </span>Site by<span> </span>the<span> </span>UNESCO<span> </span>due<span> </span>to<span> </span>its<span> </span>patrimonial<span> </span>value.<span> </span>The<span> </span>Giralda<span> </span>was<span> </span>constructed<span> </span>in<span> </span>1384<span> </span>as<span> </span>the<span> </span><em>Aljama<span> </span></em>of<span> </span>the major<span> </span>mosque<span> </span>of<span> </span>Seville.<span> </span>However,<span> </span>it<span> </span>has<span> </span>undergone<span> </span>different<span> </span>construction<span> </span>phases<span> </span>over<span> </span>time.<span> </span>One<span> </span>of<span> </span>the most relevant modifications was the addition of the bell tower designed by the architect Hernán Ruíz in the Renaissance. Moreover, the tower has been affected by several historic earthquakes. The goal<span> </span>of this<span> </span>study<span> </span>is<span> </span>to<span> </span>define<span> </span>the<span> </span>geotechnical<span> </span>profile<span> </span>of<span> </span>the<span> </span>soil<span> </span>under<span> </span>the<span> </span>tower<span> </span>and<span> </span>to<span> </span>analyse<span> </span>its<span> </span>settlements. This study will focus on the several modifications that the building has suffered throughout its history. Moreover, it will properly and exhaustively characterise the foundation, which has not been carried out to date. To do so, the geotechnical profile has been defined accurately with the information of the boreholes drilled at its base. Then, finite elements have been used to model the different load phases, which correspond to the different construction phases. Finally, this analysis has shown a great agree- ment between the settlements of the tower and its real top displacements.</p> ]]> Analysis of the Giralda Tower Geotechnical Profile and Its Settlements emilio romero sánchez antonio morales esteban maría victoria requena garcía de la cruz jaime navarro casas doi: 10.2495/CMEM-V10-N1-1-12 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2022 10 1 Article 1 10.2495/CMEM-V10-N1-1-12 https://www.acadlore.com/article/IJCMEM/2022_10_1/CMEM-V10-N1-1-12 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-456-465 This article considers the questions connected with creation of optimum algorithms using the laws of thermodynamics as applied to a computing process. Ideas and methods of phenomenological and statistic thermodynamics are used to estimate the amount of calculations or volume of the neural network. Introduction of the other thermodynamic functions, besides entropy, and also defi nition of the three thermodynamic origins in the context of calculations allow to study stability, organize the parameters according their information weights, carry out the decomposition of the complex systems, construct the rapid algorithms. The way of creation of the neural network structure is offered, consisting in use of the pre-trained fragments. <![CDATA[ <p>This article considers the questions connected with creation of optimum algorithms using the laws of thermodynamics as applied to a computing process. Ideas and methods of phenomenological and statistic thermodynamics are used to estimate the amount of calculations or volume of the neural network. Introduction of the other thermodynamic functions, besides entropy, and also defi nition of the three thermodynamic origins in the context of calculations allow to study stability, organize the parameters according their information weights, carry out the decomposition of the complex systems, construct the rapid algorithms. The way of creation of the neural network structure is offered, consisting in use of the pre-trained fragments.</p> ]]> Thermodynamic Formalism for the Study and Formation of Algorithms and Neural Networks i. f. yasinskiy f. n. yasinskiy doi: 10.2495/CMEM-V1-N4-456-465 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 456 10.2495/CMEM-V1-N4-456-465 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-456-465 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-440-455 Small scale solid particles with fl uid-fi lled pores are applied in various porous structures in energy systems, such as fuel cells, for the objectives to enhance the catalytic reaction activities and improve the fuel utilization effi ciency or/and reduce the pollutants. In addition to the catalytic reactions, heat transfer processes in fuel cell porous electrodes are strongly affected by the small scale and complex porous structures. In this paper, the thermal energy equation commonly used for continuum models at porous-averaging level is highlighted, with the purpose to provide a general overview of the validity and limiting conditions for its application. Models for effective thermal conductivity are reviewed and discussed. It is found that both the rarefaction and tortuosity effects on reduction of effective thermal conductivity may be signifi cant, and these should be evaluated based on detailed information of operating parameters, pore size distributions and topologic structures. Comments and suggestions are presented for the better understanding and implementation of the continuum heat transfer models for fuel cell electrodes. <![CDATA[ <p>Small scale solid particles with fl uid-fi lled pores are applied in various porous structures in energy systems, such as fuel cells, for the objectives to enhance the catalytic reaction activities and improve the fuel utilization effi ciency or/and reduce the pollutants. In addition to the catalytic reactions, heat transfer processes in fuel cell porous electrodes are strongly affected by the small scale and complex porous structures. In this paper, the thermal energy equation commonly used for continuum models at porous-averaging level is highlighted, with the purpose to provide a general overview of the validity and limiting conditions for its application. Models for effective thermal conductivity are reviewed and discussed. It is found that both the rarefaction and tortuosity effects on reduction of effective thermal conductivity may be signifi cant, and these should be evaluated based on detailed information of operating parameters, pore size distributions and topologic structures. Comments and suggestions are presented for the better understanding and implementation of the continuum heat transfer models for fuel cell electrodes.</p> ]]> Evaluation of Models of the Effective Thermal Conductivity of Porous Materials Relevant to Fuel Cell Electrodes b. sundén j. yuan doi: 10.2495/CMEM-V1-N4-440-455 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 440 10.2495/CMEM-V1-N4-440-455 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-440-455 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-416-439 Electronic components, which are widely used in modern projectiles, are subjected to high acceleration during launch. These accelerations may result in failure of the components, which affects the performance of the projectile. The objective of this research is to better understand how shocks are transmitted to electronic boards within a projectile and also to investigate ways of mitigating these shocks. To achieve these goals, a projectile prototype, composed of threaded components, was created. The effect of the tightening preload torque on the accelerations and the frequencies of the components on an electronic board were explored. An approach to mitigate transmitted accelerations to the board using a polyurethane rubber mount is presented. Suggestions for ensuring an accurate fi nite element model of the experimental setup are included. <![CDATA[ <p>Electronic components, which are widely used in modern projectiles, are subjected to high acceleration during launch. These accelerations may result in failure of the components, which affects the performance of the projectile. The objective of this research is to better understand how shocks are transmitted to electronic boards within a projectile and also to investigate ways of mitigating these shocks. To achieve these goals, a projectile prototype, composed of threaded components, was created. The effect of the tightening preload torque on the accelerations and the frequencies of the components on an electronic board were explored. An approach to mitigate transmitted accelerations to the board using a polyurethane rubber mount is presented. Suggestions for ensuring an accurate fi nite element model of the experimental setup are included.</p> ]]> Shock Mitigation for Electronic Boards within a Projectile d. s. somasundaram m. b. trabia b. o’toole q. liu doi: 10.2495/CMEM-V1-N4-416-439 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 416 10.2495/CMEM-V1-N4-416-439 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-416-439 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-406-415 The problem of the reliability of capillary-barriers’ modelling is studied making use of tipping trough measurements. In its first part, the article describes laboratory measurements of saturated hydraulic conductivities and retention curves of four materials of two different capillary barriers. Both the main branches of the retention curves were measured, and the unsaturated hydraulic conductivities and capacity functions were determined. The second part of the article describes numerical modelling of two tipping trough experiments. The obtained results are compared with the measured data. The comparison shows a good agreement that is presented and discussed. It is concluded that, in the case of capillary barrier materials, the laboratory measurements made on samples and the subsequent math- ematical modelling can substitute for the tipping trough experiments. <![CDATA[ <p>The problem of the reliability of capillary-barriers’ modelling is studied making use of tipping trough measurements. In its first part, the article describes laboratory measurements of saturated hydraulic conductivities and retention curves of four materials of two different capillary barriers. Both the main branches of the retention curves were measured, and the unsaturated hydraulic conductivities and capacity functions were determined. The second part of the article describes numerical modelling of two tipping trough experiments. The obtained results are compared with the measured data. The comparison shows a good agreement that is presented and discussed. It is concluded that, in the case of capillary barrier materials, the laboratory measurements made on samples and the subsequent math- ematical modelling can substitute for the tipping trough experiments.</p> ]]> On the Reliability of Mathematical Modelling of Capillary Barriers jiri mls dagmar trpkosova doi: 10.2495/CMEM-V1-N4-406-415 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 406 10.2495/CMEM-V1-N4-406-415 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-406-415 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-395-405 An experimental study was conducted to investigate the ability of ribbon fairings to suppress flow-induced vibrations on a long flexible horizontal cylinder. The test matrix included towing the cylinder at various speeds, towing the cylinder in regular waves, and investigating the influence of partial coverage on the response behavior. The test cylinder was 29 m long with a length to diameter (L/D) ratio of ~760. Interior to the tensioned cylinder model were six sets of unequally spaced biaxial accelerometers in a lightly pressurized environment keeping the interior dry. A string potentiometer was externally attached at the center of the model to provide a reference for later displacement estimates based on integration of the acceleration data. The time domain decomposition method (TDD) was used to recover mode shapes, damping characteristics, and modal contribution factors. For the uniform current cases, the findings illustrate that ribbon fairings are effective and provide increased damping when compared with bare cylinders. Partial coverage demonstrates that localized suppression becomes increasingly less effective as the percentage coverage is reduced. The introduction of regular waves to the towed cylinder cases illustrates the ineffectiveness of ribbon fairing to suppress the orbital motions induced by the waves, which is preferable to the amplification typically observed for airfoil fairings. <![CDATA[ <p>An experimental study was conducted to investigate the ability of ribbon fairings to suppress flow-induced vibrations on a long flexible horizontal cylinder. The test matrix included towing the cylinder at various speeds, towing the cylinder in regular waves, and investigating the influence of partial coverage on the response behavior. The test cylinder was 29 m long with a length to diameter (L/D) ratio of ~760. Interior to the tensioned cylinder model were six sets of unequally spaced biaxial accelerometers in a lightly pressurized environment keeping the interior dry. A string potentiometer was externally attached at the center of the model to provide a reference for later displacement estimates based on integration of the acceleration data. The time domain decomposition method (TDD) was used to recover mode shapes, damping characteristics, and modal contribution factors. For the uniform current cases, the findings illustrate that ribbon fairings are effective and provide increased damping when compared with bare cylinders. Partial coverage demonstrates that localized suppression becomes increasingly less effective as the percentage coverage is reduced. The introduction of regular waves to the towed cylinder cases illustrates the ineffectiveness of ribbon fairing to suppress the orbital motions induced by the waves, which is preferable to the amplification typically observed for airfoil fairings.</p> ]]> Suppression of Flow-Induced Vibrations Using Ribbon Fairings john m. niedzwecki sam m. fang doi: 10.2495/CMEM-V1-N4-395-405 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 395 10.2495/CMEM-V1-N4-395-405 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-395-405 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-381-394 The subject of interest is the validation of a 3-D numerical computer model of a hypersonic flow around double cone geometry. The double cone geometry represents a generic space vehicle which enters the atmosphere at extremely high velocity. This leads to complex flow phenomena around the space vehicle. In this paper the flow-field around the space vehicle is investigated. Experimental data is obtained for different double-cone geometries mounted inside a hypersonic wind-tunnel. During the experiments the Mach number is equal to 9. Three different geometries and four different operating conditions are the subject of this study. Because of the short test period of less than 200 ms a measurement of temperatures and local velocities is not possible during test. Therefore, the computational model is used. The numerical solver is based on the compressible Navier–Stokes equations and implements an adaptive meshing tool. This solver is used for flow-field simulations of re-entry phenomena. The cell refinement tool adapts the local cell length to the density gradient. In this way, all shock-waves receive higher resolution than the remaining mesh and the solver shows good agreement with the experimental results while minimizing computational cost and time. For this purpose of this study a basic open source solver is used and modified and solutions are validated on experimental data. The aim of this paper is to show a good agreement of experimental pressure measurements and numerical results and to estimate results of the temperature field, the velocity field and the local Mach number using the numerical model. <![CDATA[ <p>The subject of interest is the validation of a 3-D numerical computer model of a hypersonic flow around double cone geometry. The double cone geometry represents a generic space vehicle which enters the atmosphere at extremely high velocity. This leads to complex flow phenomena around the space vehicle. In this paper the flow-field around the space vehicle is investigated. Experimental data is obtained for different double-cone geometries mounted inside a hypersonic wind-tunnel. During the experiments the Mach number is equal to 9. Three different geometries and four different operating conditions are the subject of this study. Because of the short test period of less than 200 ms a measurement of temperatures and local velocities is not possible during test. Therefore, the computational model is used. The numerical solver is based on the compressible Navier–Stokes equations and implements an adaptive meshing tool. This solver is used for flow-field simulations of re-entry phenomena. The cell refinement tool adapts the local cell length to the density gradient. In this way, all shock-waves receive higher resolution than the remaining mesh and the solver shows good agreement with the experimental results while minimizing computational cost and time. For this purpose of this study a basic open source solver is used and modified and solutions are validated on experimental data. The aim of this paper is to show a good agreement of experimental pressure measurements and numerical results and to estimate results of the temperature field, the velocity field and the local Mach number using the numerical model.</p> ]]> Numerical Simulation and Experimental Validation of a Hypersonic Flow for s. reichel r. groll doi: 10.2495/CMEM-V1-N4-381-394 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 381 10.2495/CMEM-V1-N4-381-394 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-381-394 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-367-380 Physical insight into the frictional behaviour of surfaces in contact with vacuum and other special environments is important for the accuracy of positioning mechanisms operating in these environments. The positioning accuracy and drift in these mechanisms are strongly influenced by the frictional behaviour of the mating materials. The cause for both drift and positioning accuracy is stick-to-slip and slip-to-stick transitions at asperity level, resulting in a displacement at macrolevel. Adhesion as well as friction experiments were performed for single asperity and multi-asperity contacts both in ambient and high vacuum conditions on a novel designed vacuum-based adhesion and friction tester. This paper discusses the experimental setup designed and manufactured to investigate the adhesion and friction behaviour of a single asperity contact. The intrinsic roughness of the ball and the flat will form a multiasperity contact. Pull-off and friction force measurements can be performed with the resolution better than 5 μN. The maximum normal load that can be applied with this system is 100 mN. The setup is capable of working at 10-6 mbar vacuum level as well as in ambient conditions. Experimental results show that the surrounding environment and roughness play an important role both in the adhesion force and friction force measurements. The friction force measurements show good agreement with the basic theories of contact mechanics. <![CDATA[ <p>Physical insight into the frictional behaviour of surfaces in contact with vacuum and other special environments is important for the accuracy of positioning mechanisms operating in these environments. The positioning accuracy and drift in these mechanisms are strongly influenced by the frictional behaviour of the mating materials. The cause for both drift and positioning accuracy is stick-to-slip and slip-to-stick transitions at asperity level, resulting in a displacement at macrolevel. Adhesion as well as friction experiments were performed for single asperity and multi-asperity contacts both in ambient and high vacuum conditions on a novel designed vacuum-based adhesion and friction tester. This paper discusses the experimental setup designed and manufactured to investigate the adhesion and friction behaviour of a single asperity contact. The intrinsic roughness of the ball and the flat will form a multiasperity contact. Pull-off and friction force measurements can be performed with the resolution better than 5 μN. The maximum normal load that can be applied with this system is 100 mN. The setup is capable of working at 10-6 mbar vacuum level as well as in ambient conditions. Experimental results show that the surrounding environment and roughness play an important role both in the adhesion force and friction force measurements. The friction force measurements show good agreement with the basic theories of contact mechanics.</p> ]]> Adhesion and Friction Force Measurements in Ambient and High Vacuum Conditions m.a. yaqoob m.b. de rooij d.j. schipper doi: 10.2495/CMEM-V1-N4-367-380 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 367 10.2495/CMEM-V1-N4-367-380 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-367-380 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-353-366 Planetary speed reducers are applied in a wide range of applications. Their main advantages are the compact design and high power density. For this reason, the demand for high efficiency gearboxes is continuously increasing and this is also why models to predict the additional churning loss, characteristic of this kind of gearing, are required. The particular configuration of the planetary speed reducers, in fact, entails an additional motion with a circular path around the gearbox axis of the planetary gears due to the rotation of the planet carrier on which they are mounted and this induces an additional source of loss. Having efficiency prediction models allows, in fact, comparison of different solutions during the design step. Literature provides some prediction models for ordinary gears but no models are still available for planetary gears. This report introduces a computational and experimental analysis of this kind of loss. Many simulations have been performed and the influence of many operating conditions like lubricant level and temperature and the rotational speed of the planet carrier have been studied. More- over, the results of an experimental testing campaign on a specially designed gearbox are presented and compared with the computational ones to validate the model. The two approaches give results in good agreement. <![CDATA[ <p>Planetary speed reducers are applied in a wide range of applications. Their main advantages are the compact design and high power density. For this reason, the demand for high efficiency gearboxes is continuously increasing and this is also why models to predict the additional churning loss, characteristic of this kind of gearing, are required. The particular configuration of the planetary speed reducers, in fact, entails an additional motion with a circular path around the gearbox axis of the planetary gears due to the rotation of the planet carrier on which they are mounted and this induces an additional source of loss. Having efficiency prediction models allows, in fact, comparison of different solutions during the design step. Literature provides some prediction models for ordinary gears but no models are still available for planetary gears. This report introduces a computational and experimental analysis of this kind of loss. Many simulations have been performed and the influence of many operating conditions like lubricant level and temperature and the rotational speed of the planet carrier have been studied. More- over, the results of an experimental testing campaign on a specially designed gearbox are presented and compared with the computational ones to validate the model. The two approaches give results in good agreement.</p> ]]> Influence of Lubricant Temperature, Lubricant Level and Rotational Speed on The Churning Power Loss in an Industrial Planetary Speed Reducer: Computational and Experimental Study franco concli carlo gorla doi: 10.2495/CMEM-V1-N4-353-366 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 4 Article 353 10.2495/CMEM-V1-N4-353-366 https://www.acadlore.com/article/IJCMEM/2013_1_4/CMEM-V1-N4-353-366 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-321-343 A series of five full-scale, nearly conventional, curtain wall specimens was tested in the UNC Charlotte Structures Laboratory. Specimens were subjected to quasi-static, uniform, out-of-plane loading to failure under displacement control. The tests were performed to obtain complete resistance curves, including the nonlinear behavior of the specimens up to ‘ultimate failure’. Ultimate failure was defined as mullion fracture or significant breach of the curtain wall system when viewed as the protective barrier between building occupants and the external blast load. Representative load-deflection and loadstrain resistance curves are presented. The energy absorbed by the curtain wall system up to three different limit states – first cracking of glass, first yield of mullions, and fracture/breach of the system (ultimate failure) – and maximum mullion end rotations are computed from the experimental results. Ultimate energy absorption capacity – the recoverable linear strain energy plus the nonlinear energy due to formation of damage mechanisms – and maximum mullion end rotations are essential for reliable and economical design of blast resistant curtain walls. To this end, a simplified methodology is presented for analytically approximating curtain wall resistance functions that can be input to an energy expression that models nonlinear structural dynamic behavior due to an ‘impulsive’ loading. The blast resistance of a curtain wall can then be approximated using this procedure. It is shown that a nearly conventional curtain wall, a conventional system with two modifi cations – use of laminated glass lites that are structurally glazed (wet-glazed) to a conventional framing system with structural silicone sealant – had nearly 14 times the ultimate energy absorption capacity and nearly four times the blast resistance as the fully conventional system. <![CDATA[ <p>A series of five full-scale, nearly conventional, curtain wall specimens was tested in the UNC Charlotte Structures Laboratory. Specimens were subjected to quasi-static, uniform, out-of-plane loading to failure under displacement control. The tests were performed to obtain complete resistance curves, including the nonlinear behavior of the specimens up to ‘ultimate failure’. Ultimate failure was defined as mullion fracture or significant breach of the curtain wall system when viewed as the protective barrier between building occupants and the external blast load. Representative load-deflection and loadstrain resistance curves are presented. The energy absorbed by the curtain wall system up to three different limit states – first cracking of glass, first yield of mullions, and fracture/breach of the system (ultimate failure) – and maximum mullion end rotations are computed from the experimental results. Ultimate energy absorption capacity – the recoverable linear strain energy plus the nonlinear energy due to formation of damage mechanisms – and maximum mullion end rotations are essential for reliable and economical design of blast resistant curtain walls. To this end, a simplified methodology is presented for analytically approximating curtain wall resistance functions that can be input to an energy expression that models nonlinear structural dynamic behavior due to an ‘impulsive’ loading. The blast resistance of a curtain wall can then be approximated using this procedure. It is shown that a nearly conventional curtain wall, a conventional system with two modifi cations – use of laminated glass lites that are structurally glazed (wet-glazed) to a conventional framing system with structural silicone sealant – had nearly 14 times the ultimate energy absorption capacity and nearly four times the blast resistance as the fully conventional system.</p> ]]> Experimental Program and Simplified Nonlinear Design Expression for Glass Curtain Walls with Low-Level Blast Resistance benjamin t. kennedy david c. weggel r. g. keanini doi: 10.2495/CMEM-V1-N3-321-343 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 321 10.2495/CMEM-V1-N3-321-343 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-321-343 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-298-320 The search for icephobic external surface materials in aircraf ticing applications has been ongoing since the early days of aviation. Given the recognized superlative properties of carbon nanotubes (CNTs) across many different disciplines, the implementation of CNTs in polymer matrix composites has sparked a great interest in their mechanical/electrical properties and wetting character, in addition to their suitability for aircraft icing applications. Within this framework, a new developed methodology capable of determining the nature of wettability, consequent to CNT implementation is desired. Thus, this article presents a novel methodology – henceforth referred to as the dynamic and static wettability scheme for advanced materials – which examines the wettability of materials reinforced with CNTs, for potential utilization within the aerospace industry. The described methodology herein can be employed in order to numerically examine empirically acquired results with an extended possibility to include alternative materials outside the scope of the considered ones. Results are shown for a decision matrix that discriminates between hydrophobic and hydrophilic surfaces based on their static and dynamic wettability properties. Moreover, idealized wetting character representations of the different considered aerospace materials are presented. <![CDATA[ <p>The search for icephobic external surface materials in aircraf ticing applications has been ongoing since the early days of aviation. Given the recognized superlative properties of carbon nanotubes (CNTs) across many different disciplines, the implementation of CNTs in polymer matrix composites has sparked a great interest in their mechanical/electrical properties and wetting character, in addition to their suitability for aircraft icing applications. Within this framework, a new developed methodology capable of determining the nature of wettability, consequent to CNT implementation is desired. Thus, this article presents a novel methodology – henceforth referred to as the dynamic and static wettability scheme for advanced materials – which examines the wettability of materials reinforced with CNTs, for potential utilization within the aerospace industry. The described methodology herein can be employed in order to numerically examine empirically acquired results with an extended possibility to include alternative materials outside the scope of the considered ones. Results are shown for a decision matrix that discriminates between hydrophobic and hydrophilic surfaces based on their static and dynamic wettability properties. Moreover, idealized wetting character representations of the different considered aerospace materials are presented.</p> ]]> Dynamic and Static Wettability of Advanced Materials Used in Aeronautical Applications omid gohardani david w. hammond doi: 10.2495/CMEM-V1-N3-298-320 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 298 10.2495/CMEM-V1-N3-298-320 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-298-320 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-283-297 The paper is focused on the assessment of laser-treated cementitious surfaces. It forms part of the larger study on laser cleaning process and its effect on modification of geometrical microstructure of cementitious composites. The great variation in absorptivity of highly developed surfaces of cementitious materials results in substantial differences in their responses to laser irradiation. Even though lasers can be successfully used to remove dirt from mortar surfaces, there are always some residual surface alterations associated with the removal of mortar, formation of cracks and glazing (melted mortar). Comprehensive understanding of surface processes resulting from laser interaction with substrate is essential in further industrial commercialisation of the technology. In order to address the problem a wide range of laser-treated samples with different internal microstructures, surface roughness and moisture content were studied. The characteristic features of all laser-cleaned areas included removal of mortar, formation of cracks and glassy patches. Systematic analysis of surface modifications resulting from laser cleaning confirmed a strong relationship between initial roughness of surfaces and their end conditions. An increase in initial surface roughness leads to more pronounced alterations in roughness and reduced tendency towards crack formation. <![CDATA[ <p>The paper is focused on the assessment of laser-treated cementitious surfaces. It forms part of the larger study on laser cleaning process and its effect on modification of geometrical microstructure of cementitious composites. The great variation in absorptivity of highly developed surfaces of cementitious materials results in substantial differences in their responses to laser irradiation. Even though lasers can be successfully used to remove dirt from mortar surfaces, there are always some residual surface alterations associated with the removal of mortar, formation of cracks and glazing (melted mortar). Comprehensive understanding of surface processes resulting from laser interaction with substrate is essential in further industrial commercialisation of the technology. In order to address the problem a wide range of laser-treated samples with different internal microstructures, surface roughness and moisture content were studied. The characteristic features of all laser-cleaned areas included removal of mortar, formation of cracks and glassy patches. Systematic analysis of surface modifications resulting from laser cleaning confirmed a strong relationship between initial roughness of surfaces and their end conditions. An increase in initial surface roughness leads to more pronounced alterations in roughness and reduced tendency towards crack formation.</p> ]]> Assessment of Surface Condition of Cementitious Materials Subjected to Laser Radiation a.j. klemm p. sanjeevan k. rozniakowski doi: 10.2495/CMEM-V1-N3-283-297 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 283 10.2495/CMEM-V1-N3-283-297 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-283-297 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-265-282 Application of CFRP composite materials is a popular method of strengthening reinforced concrete members. Wrapping columns with these materials is used in seismic retrofits because of the increase in the strength and ductility of concrete, and therefore, of the column itself. This is particularly beneficial for compression-controlled columns that fail by concrete crushing due to the fact that ductility and strength of the member is significantly improved. For the design of columns, interaction diagrams are used which define the maximum capacity of compression members that are subjected to axial force and bending moments. This work includes the development of interaction diagrams for circular compression members confined with CFRP composites. The concrete confinement can be light (low confinement pressure) or heavy (high confinement pressure). In this paper, three levels of confinement are evaluated: (a) zero confinement, (b) light confinement with the use of a CFRP composite grid, and (c) heavy confinement with the use of CFRP composite wraps with two different thicknesses of the wrap. A comparison of the unconfined section to the light and heavily confined sections shows a considerable difference primarily in the compression-controlled region where the axial compression and bending moment are significantly enhanced. The balance point for both light and heavy confinement has moved higher up on the interaction diagram, which changes the range of the compression and tension zones. This is evident for both light and heavy confinement. Also, the failure mode of compression-controlled columns is more ductile because of the change in the behavior of concrete due to confinement. <![CDATA[ <p>Application of CFRP composite materials is a popular method of strengthening reinforced concrete members. Wrapping columns with these materials is used in seismic retrofits because of the increase in the strength and ductility of concrete, and therefore, of the column itself. This is particularly beneficial for compression-controlled columns that fail by concrete crushing due to the fact that ductility and strength of the member is significantly improved. For the design of columns, interaction diagrams are used which define the maximum capacity of compression members that are subjected to axial force and bending moments. This work includes the development of interaction diagrams for circular compression members confined with CFRP composites. The concrete confinement can be light (low confinement pressure) or heavy (high confinement pressure). In this paper, three levels of confinement are evaluated: (a) zero confinement, (b) light confinement with the use of a CFRP composite grid, and (c) heavy confinement with the use of CFRP composite wraps with two different thicknesses of the wrap. A comparison of the unconfined section to the light and heavily confined sections shows a considerable difference primarily in the compression-controlled region where the axial compression and bending moment are significantly enhanced. The balance point for both light and heavy confinement has moved higher up on the interaction diagram, which changes the range of the compression and tension zones. This is evident for both light and heavy confinement. Also, the failure mode of compression-controlled columns is more ductile because of the change in the behavior of concrete due to confinement.</p> ]]> Effect of Confinement on the Interaction Diagrams for RC Sections with CFRP Grids and Wraps p. christou a. michael c. anastasiou d. nicolaides doi: 10.2495/CMEM-V1-N3-265-282 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 265 10.2495/CMEM-V1-N3-265-282 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-265-282 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-249-264 Microstructural fatigue initiation in Al-Sn-Si-Cu-Ni bearing lining alloys is reported and investigated. The secondary phases of such alloys comprise fine and relatively few Sn and Si particles as well as a large number of hard AlNi3-type intermetallics, frequently encapsulated within soft Sn layers. During fatigue tests, these particles were observed to initiate short fatigue cracks. Through elasto-plastic finite element analysis of ideal microstructures but with realistic geometric and mechanical property data, critical values of key stress and strain components within the matrix, the Sn layers, and the particles were predicted and linked to microstructural features associated with observed fatigue initiation. These modelling results indicate the extent to which either the hydrostatic stresses or plastic shear strains may be responsible for fatigue crack initiation in the Sn layers, as well as the optimum microstructural characteristics that would minimise tensile stresses, which are responsible for brittle particle fracture. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Microstructural fatigue initiation in Al-Sn-Si-Cu-Ni bearing lining alloys is reported and investigated. The secondary phases of such alloys comprise fine and relatively few Sn and Si particles as well as a large number of hard AlNi3-type intermetallics, frequently encapsulated within soft Sn layers. During fatigue tests, these particles were observed to initiate short fatigue cracks. Through elasto-plastic finite element analysis of ideal microstructures but with realistic geometric and mechanical property data, critical values of key stress and strain components within the matrix, the Sn layers, and the particles were predicted and linked to microstructural features associated with observed fatigue initiation. These modelling results indicate the extent to which either the hydrostatic stresses or plastic shear strains may be responsible for fatigue crack initiation in the Sn layers, as well as the optimum microstructural characteristics that would minimise tensile stresses, which are responsible for brittle particle fracture.</span></p> ]]> Microstructural Modelling of Fatigue Initiation in Aluminium-Bearing Alloys s. syngellakis m.s. ali p.a.s. reed doi: 10.2495/CMEM-V1-N3-249-264 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 249 10.2495/CMEM-V1-N3-249-264 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-249-264 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-238-248 Internal pressure as a loading mode concerns numerous engineering applications and technological processes. The present account deals with the material, the continuum, and the structural level. In addition to the stressing aspect, internal pressure is considered as the driving force in certain metal forming operations. The presentation of the subject bases on established solutions, less known results and technological applications. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Internal pressure as a loading mode concerns numerous engineering applications and technological processes. The present account deals with the material, the continuum, and the structural level. In addition to the stressing aspect, internal pressure is considered as the driving force in certain metal forming operations. The presentation of the subject bases on established solutions, less known results and technological applications.</span></p> ]]> Internal Pressure-Stressing and Forming i. doltsinis doi: 10.2495/CMEM-V1-N3-238-248 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 238 10.2495/CMEM-V1-N3-238-248 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-238-248 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-221-237 An investigation is presented that studies the response of a two-degree-of-freedom dynamic sliding system; that is a single-degree-of-freedom oscillator being fixed on top of a rigid block that can slide on its supporting shaking table along a horizontal axis when subjected to unidirectional dynamic or earthquake excitations along this horizontal axis. This problem appears to be of interest in predicting the dynamic and earthquake response of superstructures supported on a large foundation block capable of horizontal sliding by means of seismic sliding isolators. Special mock-ups are tested at the shaking table of Aristotle University for this purpose utilizing horizontal simulated earthquake excitations based on prototype earthquake ground motion recordings. The numerical results, which were obtained by a computer software developed for this purpose, are compared with the corresponding experimental measurements. The measured acceleration and displacement responses of the mock-ups appear to be, in all the examined cases, in reasonably good agreement with the numerical predictions. However, in certain cases, the numerically predicted sliding displacement of the rigid block appears to have an offset that differs from the sliding response that was observed during the experiments. This is more pronounced when there is no spring linking the rigid block with the shaking table and must be attributed to manufacturing tolerances of the mock-ups. It is demonstrated that the developed software, although it tries to represent such a rather complex problem in a simplified manner, can be useful at the preliminary design stage of structural systems resting on sliding isolators. Results from various experimental and numerical tests demonstrate that the oscillator’s response is generally made smaller by the sliding of the rigid block. This is true for a wide range of frequencies; however, there is a relatively narrow frequency window in which the oscillator’s response is amplified. This frequency window has a peak value that is slightly higher than the oscillator’s eigen-frequency when it is considered to be a single-degree-offreedom system fixed at its base. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">An investigation is presented that studies the response of a two-degree-of-freedom dynamic sliding system; that is a single-degree-of-freedom oscillator being fixed on top of a rigid block that can slide on its supporting shaking table along a horizontal axis when subjected to unidirectional dynamic or earthquake excitations along this horizontal axis. This problem appears to be of interest in predicting the dynamic and earthquake response of superstructures supported on a large foundation block capable of horizontal sliding by means of seismic sliding isolators. Special mock-ups are tested at the shaking table of Aristotle University for this purpose utilizing horizontal simulated earthquake excitations based on prototype earthquake ground motion recordings. The numerical results, which were obtained by a computer software developed for this purpose, are compared with the corresponding experimental measurements. The measured acceleration and displacement responses of the mock-ups appear to be, in all the examined cases, in reasonably good agreement with the numerical predictions. However, in certain cases, the numerically predicted sliding displacement of the rigid block appears to have an offset that differs from the sliding response that was observed during the experiments. This is more pronounced when there is no spring linking the rigid block with the shaking table and must be attributed to manufacturing tolerances of the mock-ups. It is demonstrated that the developed software, although it tries to represent such a rather complex problem in a simplified manner, can be useful at the preliminary design stage of structural systems resting on sliding isolators. Results from various experimental and numerical tests demonstrate that the oscillator’s response is generally made smaller by the sliding of the rigid block. This is true for a wide range of frequencies; however, there is a relatively narrow frequency window in which the oscillator’s response is amplified. This frequency window has a peak value that is slightly higher than the oscillator’s eigen-frequency when it is considered to be a single-degree-offreedom system fixed at its base.</span></p> ]]> The Response of a Two-Degree-of-Freedom Dynamic Sliding System Subjected to Uni-Directional Horizontal Dynamic and Seismic Excitations g.c. manos m. demosthenous doi: 10.2495/CMEM-V1-N3-221-237 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 3 Article 221 10.2495/CMEM-V1-N3-221-237 https://www.acadlore.com/article/IJCMEM/2013_1_3/CMEM-V1-N3-221-237 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-199-211 A computational approach based on electron backscatter diffraction (EBSD) measurement was proposed to estimate the effects of crystal morphology on the overall response of polycrystalline piezoelectric ceramics. EBSD-measured crystal orientations of a polycrystalline piezoelectric ceramic, barium titanate, were applied to a multiscale finite element simulation based on asymptotic homogenization theory. First, the orientation dependence of material properties, such as elastic compliance constants, dielectric and piezoelectric strain constants, was discussed for a single-domain crystal of tetragonal perovskite structure. The computation indicated that piezoelectric strain constants are more sensitive to crystal orientation compared with other properties. Then the single-crystalline material properties were introduced into multidirectionally oriented grains in the polycrystalline microstructure, the multiscale finite element analysis between macrostructure and EBSD-measured microstructure was performed. In this paper emphasis was placed on the diminution of microstructure. The authors discussed about the adverse effect on each component of macrostructural homogenized material properties, which is useful for micromechanics approaches. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A computational approach based on electron backscatter diffraction (EBSD) measurement was proposed to estimate the effects of crystal morphology on the overall response of polycrystalline piezoelectric ceramics. EBSD-measured crystal orientations of a polycrystalline piezoelectric ceramic, barium titanate, were applied to a multiscale finite element simulation based on asymptotic homogenization theory. First, the orientation dependence of material properties, such as elastic compliance constants, dielectric and piezoelectric strain constants, was discussed for a single-domain crystal of tetragonal perovskite structure. The computation indicated that piezoelectric strain constants are more sensitive to crystal orientation compared with other properties. Then the single-crystalline material properties were introduced into multidirectionally oriented grains in the polycrystalline microstructure, the multiscale finite element analysis between macrostructure and EBSD-measured microstructure was performed. In this paper emphasis was placed on the diminution of microstructure. The authors discussed about the adverse effect on each component of macrostructural homogenized material properties, which is useful for micromechanics approaches.</span></p> ]]> Electron Backscatter Diffraction Crystal Morphology Analysis and Multiscale Simulation of Piezoelectric Materials y. uetsuji h. kuramae k. tsuchiya m. kamlah doi: 10.2495/CMEM-V1-N2-199-211 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 199 10.2495/CMEM-V1-N2-199-211 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-199-211 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-173-198 Infrared thermography is becoming ever more popular and is being used in an ever-increasing number of applications mainly due to its accuracy as well as non-contact and two-dimensional characters. In particular, the thermal signatures, which are visualized over a body surface through the use of a remote infrared imaging device, may be exploited to gain information in both the body and the fluid surrounding it. In fact, thermal images may contain either information about the body’s material conditions at a given instant (e.g. material integrity or presence of defects), or its behaviour under mechanical load (e.g. during bending or impact) or about the ability of the fluid flow passing over the body surface to convey heat (i.e. cooling or heating it). Of course, what is important is the choice of the technique and of the procedure used in taking thermographic images, as well of the computational method applied in reducing data for a correct representation and interpretation of the thermal phenomena under study. The specific intention of this work is to highlight the usefulness of infrared thermography within two main tasks of materials inspection and thermo-fl uid dynamics. With regard to the first one, the different thermographic techniques, which can be used for non-destructive testing, are described with the data processing procedures; then some key examples, mainly involving composite materials, are reported and discussed. The second topic is illustrated through different flow configurations, such as impinging jets, which are encountered in the industrial context for heating or cooling purposes, a free stream flowing over a body to assess separation and/or reattachment location and a disk rotating in still air. However, a part is spent in the description of theoretical approaches and standard procedures for acquisition of thermographic images, as well of methods for data reduction and computation of the required quantities. <![CDATA[ <p>Infrared thermography is becoming ever more popular and is being used in an ever-increasing number of applications mainly due to its accuracy as well as non-contact and two-dimensional characters. In particular, the thermal signatures, which are visualized over a body surface through the use of a remote infrared imaging device, may be exploited to gain information in both the body and the fluid surrounding it. In fact, thermal images may contain either information about the body’s material conditions at a given instant (e.g. material integrity or presence of defects), or its behaviour under mechanical load (e.g. during bending or impact) or about the ability of the fluid flow passing over the body surface to convey heat (i.e. cooling or heating it). Of course, what is important is the choice of the technique and of the procedure used in taking thermographic images, as well of the computational method applied in reducing data for a correct representation and interpretation of the thermal phenomena under study. The specific intention of this work is to highlight the usefulness of infrared thermography within two main tasks of materials inspection and thermo-fl uid dynamics. With regard to the first one, the different thermographic techniques, which can be used for non-destructive testing, are described with the data processing procedures; then some key examples, mainly involving composite materials, are reported and discussed. The second topic is illustrated through different flow configurations, such as impinging jets, which are encountered in the industrial context for heating or cooling purposes, a free stream flowing over a body to assess separation and/or reattachment location and a disk rotating in still air. However, a part is spent in the description of theoretical approaches and standard procedures for acquisition of thermographic images, as well of methods for data reduction and computation of the required quantities.</p> ]]> Infrared Thermography in Materials Inspection and Thermo-Fluid Dynamics giovanni maria carlomagno carosena meola doi: 10.2495/CMEM-V1-N2-173-198 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 173 10.2495/CMEM-V1-N2-173-198 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-173-198 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-164-172 One of the most challenging modelling problems in modern engineering is that of a particle crossing a continuous phase (air). In sprinkler irrigation practice this may refer to a water droplet travelling in air from the nozzle to the ground. The challenge mainly refers to the difficulty in designing and solving the system of governing equations for that very complicate process, where many non-linearities occur when describing the relations and dependences among the parameters that rule the phenomenon. The problem becomes even more complicated when not just a single droplet alone is assessed but a multi-droplet system is accounted for. In addition to the inter-parameter dependencies, an inter-droplet reciprocal connection is also observed, mainly due to electrical interactions between the hydrogen and the oxygen atoms of the different water molecules. An alternative to traditional classic approaches to analyse water droplet dynamics in sprinkler irrigation has been recently proposed in the form of a quantum approach, but the whole classic-quantum and single-droplet versus multi-droplet alternatives need to be discussed and pinpointed which are among the main aims of the present paper which focuses on the theoretical part of the issue, thus highlighting the new perspectives of a deeper comprehension in the spray flow related phenomena. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">One of the most challenging modelling problems in modern engineering is that of a particle crossing a continuous phase (air). In sprinkler irrigation practice this may refer to a water droplet travelling in air from the nozzle to the ground. The challenge mainly refers to the difficulty in designing and solving the system of governing equations for that very complicate process, where many non-linearities occur when describing the relations and dependences among the parameters that rule the phenomenon. The problem becomes even more complicated when not just a single droplet alone is assessed but a multi-droplet system is accounted for. In addition to the inter-parameter dependencies, an inter-droplet reciprocal connection is also observed, mainly due to electrical interactions between the hydrogen and the oxygen atoms of the different water molecules. An alternative to traditional classic approaches to analyse water droplet dynamics in sprinkler irrigation has been recently proposed in the form of a quantum approach, but the whole classic-quantum and single-droplet versus multi-droplet alternatives need to be discussed and pinpointed which are among the main aims of the present paper which focuses on the theoretical part of the issue, thus highlighting the new perspectives of a deeper comprehension in the spray flow related phenomena.</span></p> ]]> Water Droplet Trajectories in a Sprinkler Spray Flow: The Classic Versus Quantum and Single Versus Multi-Droplet Pictures daniele de wrachien giulio lorenzini stefano mambretti doi: 10.2495/CMEM-V1-N2-164-172 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 164 10.2495/CMEM-V1-N2-164-172 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-164-172 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-142-163 The paper deals with two different approaches for the analysis of electromagnetic field coupling to arbitrary wire configurations buried in a lossy medium: the wire antenna theory and the transmission line method. The wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model is based on the telegrapher's equations. The set of Pocklington equations is solved via the Galerkin–Bubnov scheme of the indirect boundary element method, while the telegrapher's equations are treated using the chain matrix method and finite difference technique, respectively. A number of illustrative computational examples pertaining to buried multiple lines and grounding systems is given in the paper. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">The paper deals with two different approaches for the analysis of electromagnetic field coupling to arbitrary wire configurations buried in a lossy medium: the wire antenna theory and the transmission line method. The wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model is based on the telegrapher's equations. The set of Pocklington equations is solved via the Galerkin–Bubnov scheme of the indirect boundary element method, while the telegrapher's equations are treated using the chain matrix method and finite difference technique, respectively. A number of illustrative computational examples pertaining to buried multiple lines and grounding systems is given in the paper.</span></p> ]]> Electromagnetic Field Coupling to Arbitrary Wire Configurations Buried in a Lossy Ground: A Review of Antenna Model and Transmission Line Approach dragan poljak khalil el-khamlichi drissi bachir nekhoul doi: 10.2495/CMEM-V1-N2-142-163 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 142 10.2495/CMEM-V1-N2-142-163 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-142-163 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-132-141 Residence time and local mean age of fluid are important parameters of the fluid flow, with which we are able to detect the functioning and non-functioning zones. It is a novel approach to estimate the effect of dead-zones on chemical and biological processes. In this paper, we introduce a numerical tracer study, which is calibrated by field measurements and which is applied in different cases such as settling tank and aeration tank of wastewater treatment. Using an advective-diffusive passive scalar transport equation, the age of the fluid can be calculated. It also shows the short-circuits and dead-zones of the fluid and this corresponds with our observations. This method helps eliminate potential hydraulic problems at the early stage of design. <![CDATA[ <p>Residence time and local mean age of fluid are important parameters of the fluid flow, with which we are able to detect the functioning and non-functioning zones. It is a novel approach to estimate the effect of dead-zones on chemical and biological processes. In this paper, we introduce a numerical tracer study, which is calibrated by field measurements and which is applied in different cases such as settling tank and aeration tank of wastewater treatment. Using an advective-diffusive passive scalar transport equation, the age of the fluid can be calculated. It also shows the short-circuits and dead-zones of the fluid and this corresponds with our observations. This method helps eliminate potential hydraulic problems at the early stage of design.</p> ]]> nvestigation of Residence Time Distribution and Local Mean Age of Fluid to Determine Dead-Zones in Flow Field t. karches k. buzas doi: 10.2495/CMEM-V1-N2-132-141 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 132 10.2495/CMEM-V1-N2-132-141 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-132-141 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-116-131 Transition process in separated–reattached flows plays a key role in many practical engineering applications. Hence, accurately predicting transition is crucial since the transition location has a significant impact on the aerodynamic performance and a fundamental understanding of the instability mechanisms involved in transition process is required in order to make significant advances in engineering design and transition control, for example, to delay the turbulent phase where laminar flow characteristics are desirable (low friction drag) or to accelerate it where high mixing of turbulent flow are of interest (in a combustor). The current understanding of instabilities involved in the transition process in separated–reattached flows is far from complete and it is usually very difficult to theoretically and experimentally study the transition process since theoretical studies suffer from the limitation imposed by nonlinearity of the transition process at later stages and experimental studies are limited by temporal and spatial resolution; hence, a thorough description of the transition process is lacking. Nevertheless, significant progress has been made with the simulation tools, such as large eddy simulation (LES), which has shown improved predictive capabilities and can predict transition process accurately. This paper will first briefly present LES formalism followed by its applications to study the transition process in separated–reattached flows, reviewing our current understanding of several important phenomena associated with the transition process and focusing on the instabilities in particular. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Transition process in separated–reattached flows plays a key role in many practical engineering applications. Hence, accurately predicting transition is crucial since the transition location has a significant impact on the aerodynamic performance and a fundamental understanding of the instability mechanisms involved in transition process is required in order to make significant advances in engineering design and transition control, for example, to delay the turbulent phase where laminar flow characteristics are desirable (low friction drag) or to accelerate it where high mixing of turbulent flow are of interest (in a combustor). The current understanding of instabilities involved in the transition process in separated–reattached flows is far from complete and it is usually very difficult to theoretically and experimentally study the transition process since theoretical studies suffer from the limitation imposed by nonlinearity of the transition process at later stages and experimental studies are limited by temporal and spatial resolution; hence, a thorough description of the transition process is lacking. Nevertheless, significant progress has been made with the simulation tools, such as large eddy simulation (LES), which has shown improved predictive capabilities and can predict transition process accurately. This paper will first briefly present LES formalism followed by its applications to study the transition process in separated–reattached flows, reviewing our current understanding of several important phenomena associated with the transition process and focusing on the instabilities in particular.</span></p> ]]> Numerical Study of Instabilities in Separated-Reattached Flows z. yang doi: 10.2495/CMEM-V1-N2-116-131 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 116 10.2495/CMEM-V1-N2-116-131 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-116-131 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-103-115 A three-dimensional double-diffusive natural convection with opposing buoyancy effects in a cubic enclosure filled with fluid saturated porous media is studied numerically using the boundary element method (BEM). The mathematical model is based on the space-averaged Navier–Stokes equations, which are coupled with the energy and species equations. The simulation of coupled laminar viscous flow, heat and solute transfer is performed using a combination of single-domain BEM and subdomain BEM, which solves the velocity-vorticity formulation of governing equations. The numerical simulations for a case of negative values of buoyancy coefficient are presented, focusing on the situations where the flow field becomes three-dimensional. The results are analyzed in terms of the average heat and mass transfer at the walls of the enclosure. When possible, the results are compared with previous existing numerical data published in literature. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A three-dimensional double-diffusive natural convection with opposing buoyancy effects in a cubic enclosure filled with fluid saturated porous media is studied numerically using the boundary element method (BEM). The mathematical model is based on the space-averaged Navier–Stokes equations, which are coupled with the energy and species equations. The simulation of coupled laminar viscous flow, heat and solute transfer is performed using a combination of single-domain BEM and subdomain BEM, which solves the velocity-vorticity formulation of governing equations. The numerical simulations for a case of negative values of buoyancy coefficient are presented, focusing on the situations where the flow field becomes three-dimensional. The results are analyzed in terms of the average heat and mass transfer at the walls of the enclosure. When possible, the results are compared with previous existing numerical data published in literature.</span></p> ]]> Three-Dimensional Double-Diffusive Natural Convection with Opposing Buoyancy Effects in Porous Enclosure by Boundary Element Method j. kramer j. ravnik r. jecl l. škerget doi: 10.2495/CMEM-V1-N2-103-115 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2013 1 2 Article 103 10.2495/CMEM-V1-N2-103-115 https://www.acadlore.com/article/IJCMEM/2013_1_2/CMEM-V1-N2-103-115 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-80-92 Accurate estimation of discharge in any open channel depends on the suitable accounting of the resistance coefficients. The energy loss is influenced by the channel geometry and flow parameters, which are assumed to be lumped into a single value manifested in the form of resistance coefficients in terms of Manning's n, Chezy's C, and Darcy–Weisbach f. The flow structure for meandering channels is more complex as compared to that of straight channels due to its three-dimensional motion. Consequently, the use of design methods based on straight channels is inappropriate when applied to meandering channels and results in large errors when estimating the discharge. A series of experimental results are presented concerning stage–discharge–resistance relationships for meandering channels with rigid and smooth boundaries. Investigation concerning the loss of energy of flows for meandering channels in terms of variation of Chezy's C due to variation of sinuosity, geometry, and longitudinal slope are studied.A discharge predictive method for meandering channel is proposed that accounts for the variation of roughness with depth of flow in the channel. The performance of the model is evaluated and is found to compare well with other available models. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Accurate estimation of discharge in any open channel depends on the suitable accounting of the resistance coefficients. The energy loss is influenced by the channel geometry and flow parameters, which are assumed to be lumped into a single value manifested in the form of resistance coefficients in terms of Manning's n, Chezy's C, and Darcy–Weisbach f. The flow structure for meandering channels is more complex as compared to that of straight channels due to its three-dimensional motion. Consequently, the use of design methods based on straight channels is inappropriate when applied to meandering channels and results in large errors when estimating the discharge. A series of experimental results are presented concerning stage–discharge–resistance relationships for meandering channels with rigid and smooth boundaries. Investigation concerning the loss of energy of flows for meandering channels in terms of variation of Chezy's C due to variation of sinuosity, geometry, and longitudinal slope are studied.A discharge predictive method for meandering channel is proposed that accounts for the variation of roughness with depth of flow in the channel. The performance of the model is evaluated and is found to compare well with other available models.</span></p> ]]> Stage-Discharge Prediction for Meandering Channels k. k. khatua k.c. patra p. nayak n. sahoo doi: 10.2495/CMEM-V1-N1-80-92 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 80 10.2495/CMEM-V1-N1-80-92 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-80-92 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-72-79 This project offers the opportunity to investigate oscillatory phenomena that can jeopardize the safety of structures of particular importance, using the accelerometers installed on small electromechanical (MEMS) devices known as Motes, which are devices that transmit data remotely without the need of using cable connections. The term ‘Motes’ usually indicates the single node in a Wireless Sensor Network (WSN). Using the accelerometer sensor installed on these tools, it is possible to program a network with numerous sensors to monitor the behavior of the system being tested. The present state of research has made it possible to obtain a prototype sensor by means of which data can be compared with those measured using traditional systems to detect accelerations ( piezoelectric accelerometers). The first step was that of defi ning the calibration procedure. Once the calibration curve has been completed in the laboratory, the single node (Mote) can be programmed for the acquisition of a single physical quantity and can also be scheduled to transmit these values to create a WSN, comprising numerous sensors connected to a central node that acts as a receiver. All programming is done using the nesC language, and it is finally loaded onto the sensor using the TinyOS operating system for the management of the nodes. During the measurements, one of the main problems manifested by these devices was the discharge of the batteries after a prolonged use. This is highly interesting because the ‘offset value’ characteristic of the sensor is influenced by the energy possessed by the batteries. Another problem highlighted by the tests conducted is the low sensitivity of the accelerometers, compared to that of a seismic accelerometer, a feature causing the loss of events with an intensity below a certain threshold. Nevertheless, these systems make it possible to monitor, with very low costs, critical structures that are subject to physical events of particular intensity to prevent disaster <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">This project offers the opportunity to investigate oscillatory phenomena that can jeopardize the safety of structures of particular importance, using the accelerometers installed on small electromechanical (MEMS) devices known as Motes, which are devices that transmit data remotely without the need of using cable connections. The term ‘Motes’ usually indicates the single node in a Wireless Sensor Network (WSN). Using the accelerometer sensor installed on these tools, it is possible to program a network with numerous sensors to monitor the behavior of the system being tested. The present state of research has made it possible to obtain a prototype sensor by means of which data can be compared with those measured using traditional systems to detect accelerations ( piezoelectric accelerometers). The first step was that of defi ning the calibration procedure. Once the calibration curve has been completed in the laboratory, the single node (Mote) can be programmed for the acquisition of a single physical quantity and can also be scheduled to transmit these values to create a WSN, comprising numerous sensors connected to a central node that acts as a receiver. All programming is done using the nesC language, and it is finally loaded onto the sensor using the TinyOS operating system for the management of the nodes. During the measurements, one of the main problems manifested by these devices was the discharge of the batteries after a prolonged use. This is highly interesting because the ‘offset value’ characteristic of the sensor is influenced by the energy possessed by the batteries. Another problem highlighted by the tests conducted is the low sensitivity of the accelerometers, compared to that of a seismic accelerometer, a feature causing the loss of events with an intensity below a certain threshold. Nevertheless, these systems make it possible to monitor, with very low costs, critical structures that are subject to physical events of particular intensity to prevent disaster</span></p> ]]> Construction and Validation of Small Electro-Mechanical Vibration Sensors adolfo sabato alessandro sabato doi: 10.2495/CMEM-V1-N1-72-79 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 72 10.2495/CMEM-V1-N1-72-79 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-72-79 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-55-71 A simplified approach is proposed and used to study the TiO2 nanoparticle transport and diffusion in an exposure chamber. This exposure chamber is used to assess lung toxicity in rats resulting from the inhalation of airborne nanoparticles. The simplified approach uses computational fluid dynamics (CFD) commercial software. The mathematical model for airflow is based on the three-dimensional Reynoldsaveraged Navier–Stokes equations with turbulence modeling. The mathematical model for airborne nanoparticles transport is based on assumptions such that their motions are similar to those of a singlesized diameter distribution of a passive contaminant. This model is valid as long as the nanoparticle concentration is low and the particle diameter is small enough that settling is negligible, which is the case for the exposure chamber studied. With this model, the diffusion coefficient is a property that plays a significant role in the transport of airborne nanoparticles. The particle diffusion coefficient can be expressed in terms of a friction coefficient, and three possible relationships to model particle diffusion are presented. Their influences on the friction and diffusion coefficients are considered for the particular case of TiO2 nanoparticles. Although all the models studied here predict a decrease in the value of the diffusion coefficient with increasing particle diameter, some significant variations can be observed between the models. A specific diffusion model is selected and then used with the simplified approach. The simplified approach is first validated against available correlations for particle deposition on walls. Correlation for deposition loss rate in the case of a room agrees with numerical prediction for particle diameter between 10 and 200 nm. Particle mass concentration distribution inside the exposure chamber is also studied. The computed concentration distribution is quite uniform inside the exposure chamber and corresponds to single point measurements. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">A simplified approach is proposed and used to study the TiO2 nanoparticle transport and diffusion in an exposure chamber. This exposure chamber is used to assess lung toxicity in rats resulting from the inhalation of airborne nanoparticles. The simplified approach uses computational fluid dynamics (CFD) commercial software. The mathematical model for airflow is based on the three-dimensional Reynoldsaveraged Navier–Stokes equations with turbulence modeling. The mathematical model for airborne nanoparticles transport is based on assumptions such that their motions are similar to those of a singlesized diameter distribution of a passive contaminant. This model is valid as long as the nanoparticle concentration is low and the particle diameter is small enough that settling is negligible, which is the case for the exposure chamber studied. With this model, the diffusion coefficient is a property that plays a significant role in the transport of airborne nanoparticles. The particle diffusion coefficient can be expressed in terms of a friction coefficient, and three possible relationships to model particle diffusion are presented. Their influences on the friction and diffusion coefficients are considered for the particular case of TiO2 nanoparticles. Although all the models studied here predict a decrease in the value of the diffusion coefficient with increasing particle diameter, some significant variations can be observed between the models. A specific diffusion model is selected and then used with the simplified approach. The simplified approach is first validated against available correlations for particle deposition on walls. Correlation for deposition loss rate in the case of a room agrees with numerical prediction for particle diameter between 10 and 200 nm. Particle mass concentration distribution inside the exposure chamber is also studied. The computed concentration distribution is quite uniform inside the exposure chamber and corresponds to single point measurements.</span></p> ]]> A Simplified Approach for Modelling Airborne Nanoparticules Transport and Diffusion françois morency stéphane hallé doi: 10.2495/CMEM-V1-N1-55-71 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 55 10.2495/CMEM-V1-N1-55-71 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-55-71 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-37-54 Base-isolated buildings experience large horizontal relative displacements during strong earthquakes due to the excessive flexibility that is purposely incorporated, through seismic bearings, at their bases. When the available clearance around a base-isolated building is limited, there is a possibility of the building pounding against the surrounding moat wall or adjacent structures. Considering the nonlinearities involved in this structural impact problem, it is evident that the effects of potential pounding on the overall seismic response of base-isolated buildings during earthquake excitations should be investigated numerically through appropriate simulations. Object-oriented programming (OOP), design patterns (DPs), and the Java programming language have been utilized in order to design and implement a flexible and extendable software application that can be effectively used to perform the necessary numerical simulations and parametric studies of base-isolated buildings that may experience structural poundings during earthquake excitations. The aim of this paper is twofold: (i) to explain the significant advantages of utilizing OOP, DPs, and Java in structural analysis software and (ii) to use the developed software to study earthquake-induced poundings of base-isolated buildings. <![CDATA[ <p><span style="color: rgb(30, 30, 30); font-family: Lato, Helvetica Neue, Arial, sans-serif">Base-isolated buildings experience large horizontal relative displacements during strong earthquakes due to the excessive flexibility that is purposely incorporated, through seismic bearings, at their bases. When the available clearance around a base-isolated building is limited, there is a possibility of the building pounding against the surrounding moat wall or adjacent structures. Considering the nonlinearities involved in this structural impact problem, it is evident that the effects of potential pounding on the overall seismic response of base-isolated buildings during earthquake excitations should be investigated numerically through appropriate simulations. Object-oriented programming (OOP), design patterns (DPs), and the Java programming language have been utilized in order to design and implement a flexible and extendable software application that can be effectively used to perform the necessary numerical simulations and parametric studies of base-isolated buildings that may experience structural poundings during earthquake excitations. The aim of this paper is twofold: (i) to explain the significant advantages of utilizing OOP, DPs, and Java in structural analysis software and (ii) to use the developed software to study earthquake-induced poundings of base-isolated buildings.</span></p> ]]> Utilization of Object-Oriented Programming, Design Patterns and Java for Simulating Earthquake-Induced Poundings of Base-Isolated Buildings p. komodromos p. polycarpou doi: 10.2495/CMEM-V1-N1-37-54 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 37 10.2495/CMEM-V1-N1-37-54 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-37-54 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-17-36 Military operations performed by UN and NATO forces within the framework of stabilization missions revealed the weak points of the equipment utilized by these organizations. It turned out that one of the most dangerous threats is posed by partisan missiles equipped with cumulative heads. These missiles are mostly based on a Soviet solution and allow the penetration up to 300 mm of reinforced steel. This fact results in a serious problem which concerns the relevant protection against such a type of weapon. One of protection methods against cumulative missiles is the application of rod armours.The present paper concentrates on the analysis of the impact of a missile with a cumulative head (type PG-G7) into armour made of rods with a circular cross-section. Four options of rods arrangements were considered. A short characteristic of an analysed object was presented. A principle of operations of a missile with the specifi cation of its sensitive elements was described from the perspective of origi-nating of a cumulative stream. The stages of constructing a numerical model as well as the applied simplifi cations of geometry and initial boundary conditions were presented. On the basis of the obtained results, a degree of destruction of key elements of the missile was estimated. The fi gures revealing defor-mation of the missile and the maps of stresses in these elements were presented. In the summary section, an infl uence of a degree of the impact of a missile type PG-G7 into an armour made of rods with circular cross-section on weakening of operation effectiveness of such type of ammunition was determined.The calculations were realized in LS-Dyna system which is purposed, among others, for fast chang-ing analyses with the use of a fi nite element method. To solve an equation of motion, an explicit integration method included in this system was applied. <![CDATA[ <p>Military operations performed by UN and NATO forces within the framework of stabilization missions revealed the weak points of the equipment utilized by these organizations. It turned out that one of the most dangerous threats is posed by partisan missiles equipped with cumulative heads. These missiles are mostly based on a Soviet solution and allow the penetration up to 300 mm of reinforced steel. This fact results in a serious problem which concerns the relevant protection against such a type of weapon. One of protection methods against cumulative missiles is the application of rod armours.</p><p>The present paper concentrates on the analysis of the impact of a missile with a cumulative head (type PG-G7) into armour made of rods with a circular cross-section. Four options of rods arrangements were considered. A short characteristic of an analysed object was presented. A principle of operations of a missile with the specifi cation of its sensitive elements was described from the perspective of origi-nating of a cumulative stream. The stages of constructing a numerical model as well as the applied simplifi cations of geometry and initial boundary conditions were presented. On the basis of the obtained results, a degree of destruction of key elements of the missile was estimated. The fi gures revealing defor-mation of the missile and the maps of stresses in these elements were presented. In the summary section, an infl uence of a degree of the impact of a missile type PG-G7 into an armour made of rods with circular cross-section on weakening of operation effectiveness of such type of ammunition was determined.</p><p>The calculations were realized in LS-Dyna system which is purposed, among others, for fast chang-ing analyses with the use of a fi nite element method. To solve an equation of motion, an explicit integration method included in this system was applied.</p> ]]> Estimation of Destruction of Missile with Cumulative Head During Contact with Chosen Type of Rod Armour k. sybilski r. panowicz t. niezgoda w. barnat doi: 10.2495/CMEM-V1-N1-17-36 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 17 10.2495/CMEM-V1-N1-17-36 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-17-36 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-1-16 The paper presents an experimental investigation into the internal blast loading of open-ended, seamless, mild steel cylinders. A series of 10 trials were conducted on explosively loaded vessels using increasing masses of PE4 explosive. The objective of these trials was to determine the maximum circumferential strain induced in the cylinder wall as a result of the blast loading and also to determine the minimum amount of explosive required to cause wall failure in the cylinder. A cylindrical-shaped charge was detonated at the centre of the cylinder as this was more likely to produce a symmetrical blast wave than a spherical-shaped charge. The response of the cylinder with increasing charge size goes from large plastic deformation to failure by propagation of longitudinal cracks in the region of localized wall thinning. It is thought that the localized wall thinning is a result of unstable modal vibration and this is confi rmed by instability analysis. This investigation has allowed insight into the failure process of these structures not previously examined under the given loading conditions. The data generated in these trials has been used successfully to validate numerical and theoretical models of the cylinder response to impulsive loading. <![CDATA[ <p>The paper presents an experimental investigation into the internal blast loading of open-ended, seamless, mild steel cylinders. A series of 10 trials were conducted on explosively loaded vessels using increasing masses of PE4 explosive. The objective of these trials was to determine the maximum circumferential strain induced in the cylinder wall as a result of the blast loading and also to determine the minimum amount of explosive required to cause wall failure in the cylinder. A cylindrical-shaped charge was detonated at the centre of the cylinder as this was more likely to produce a symmetrical blast wave than a spherical-shaped charge. The response of the cylinder with increasing charge size goes from large plastic deformation to failure by propagation of longitudinal cracks in the region of localized wall thinning. It is thought that the localized wall thinning is a result of unstable modal vibration and this is confi rmed by instability analysis. This investigation has allowed insight into the failure process of these structures not previously examined under the given loading conditions. The data generated in these trials has been used successfully to validate numerical and theoretical models of the cylinder response to impulsive loading.</p> ]]> Experimental Investigation of Large Plastic Deformation and Fracture in Explosively Loaded Open-Ended Steel Cylinders g.k. schleyer n.j. rushton doi: 10.2495/CMEM-V1-N1-1-16 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 1 10.2495/CMEM-V1-N1-1-16 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-1-16 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-0 Experiments and computational approaches are of great importance in all scientific and engineering disciplines. To enable continued progress and further development, more work on experimental methods and computational procedures is needed.Scientific and technological developments were in ancient times mainly based on observations of natural occurrences. Later on, basically during the last five hundred years or so, theoretical analysis using powerful mathematical principles started to occur, culminating in the progress made during the first half of the last century. These resulted in the emergence of numerical methods that nowadays permeate all ranges of science and technology. At the same time, experimental techniques underwent remarkable improvements, becoming more sophisticated and refined, while liable to handle accurately and reliably large amounts of data. It can be seen that because of their increasing improvements, experimental techniques are becoming more and more multifaceted and complex so that both the operation of the apparatus as well as the collection of the data can only be achieved with the assistance of computers. The huge amount of data obtained needs to be processed by means of computational methods.Accurate experimental tests are more important than ever because of the increasing sophistication of numerical schemes developed for highly non-linear problems. The reliability of experimental data in these cases is vital for the validation of those schemes and to inspire confidence in the experimental data. Numerical methods play an increasingly important role in experiments, not only to process and interpret the data, but also to assist in the design of a programme to reduce the number of tests, for instance.The combined use of a computer simulated experiment aimed at the identification of system parameters through an optimisation procedure is a major development which emerged due to the dramatic evolution of computer hardware and simulation software codes. Computer simulation can indeed provide powerful insight into the behaviour of systems and processes as well as many other scientific and engineering problems. The use of simulation software for instance has led to the emergence of “virtual prototyping” which is widely used in the manufacturing industry to reduce expensive and time-consuming hardware models.Nowadays, even the evolution of some parameters can be followed up; the experiment itself continuously analysing the measurements obtained. This allows the monitoring of different types of components and gives useful information about preventative maintenance of complex systems.The main objective of the International Journal of Computational Methods and Experimental Measurements is to provide a forum to the scientific and engineering communities for the presentation and discussion of the interaction and complementary factors of Computational Methods and Experiments, with emphasis on their reciprocal and mutually beneficial integration. The Journal will also focus on the following areas:a) Experimental measurement techniques which have gradually become very sophisticatedb) Computer software, able to simulate very complex behaviourc) Optimization procedures applied to the interaction between experimental and numerical dataThe Journal has evolved from a series of very successful initiatives taken by the Wessex Institute of Technology over the last 30 years or so, which include several major conferences; including one with the same title as the Journal and others on materials, structural and mechanical systems. Most of the papers submitted at those meetings can be seen in WIT’s eLibrary (http://library.witpress.com). The Journal attempts to provide room for further development of these ideas in a more comprehensive way.The Editors, 2013 <![CDATA[ <p>Experiments and computational approaches are of great importance in all scientific and engineering disciplines. To enable continued progress and further development, more work on experimental methods and computational procedures is needed.</p><p>Scientific and technological developments were in ancient times mainly based on observations of natural occurrences. Later on, basically during the last five hundred years or so, theoretical analysis using powerful mathematical principles started to occur, culminating in the progress made during the first half of the last century. These resulted in the emergence of numerical methods that nowadays permeate all ranges of science and technology. At the same time, experimental techniques underwent remarkable improvements, becoming more sophisticated and refined, while liable to handle accurately and reliably large amounts of data. It can be seen that because of their increasing improvements, experimental techniques are becoming more and more multifaceted and complex so that both the operation of the apparatus as well as the collection of the data can only be achieved with the assistance of computers. The huge amount of data obtained needs to be processed by means of computational methods.</p><p>Accurate experimental tests are more important than ever because of the increasing sophistication of numerical schemes developed for highly non-linear problems. The reliability of experimental data in these cases is vital for the validation of those schemes and to inspire confidence in the experimental data. Numerical methods play an increasingly important role in experiments, not only to process and interpret the data, but also to assist in the design of a programme to reduce the number of tests, for instance.</p><p>The combined use of a computer simulated experiment aimed at the identification of system parameters through an optimisation procedure is a major development which emerged due to the dramatic evolution of computer hardware and simulation software codes. Computer simulation can indeed provide powerful insight into the behaviour of systems and processes as well as many other scientific and engineering problems. The use of simulation software for instance has led to the emergence of “virtual prototyping” which is widely used in the manufacturing industry to reduce expensive and time-consuming hardware models.</p><p>Nowadays, even the evolution of some parameters can be followed up; the experiment itself continuously analysing the measurements obtained. This allows the monitoring of different types of components and gives useful information about preventative maintenance of complex systems.</p><p>The main objective of the International Journal of Computational Methods and Experimental Measurements is to provide a forum to the scientific and engineering communities for the presentation and discussion of the interaction and complementary factors of Computational Methods and Experiments, with emphasis on their reciprocal and mutually beneficial integration. The Journal will also focus on the following areas:</p><p>a) Experimental measurement techniques which have gradually become very sophisticated</p><p>b) Computer software, able to simulate very complex behaviour</p><p>c) Optimization procedures applied to the interaction between experimental and numerical data</p><p>The Journal has evolved from a series of very successful initiatives taken by the Wessex Institute of Technology over the last 30 years or so, which include several major conferences; including one with the same title as the Journal and others on materials, structural and mechanical systems. Most of the papers submitted at those meetings can be seen in WIT’s eLibrary (<a target="_blank" rel="noopener noreferrer nofollow" href="http://library.witpress.com">http://library.witpress.com</a>). The Journal attempts to provide room for further development of these ideas in a more comprehensive way.</p><p></p><p>The Editors, 2013</p> ]]> Foreword giovanni carlomagno carlos a. brebbia patrick de wilde jeff de hosson norman jones bengt sundén doi: 10.2495/CMEM-V1-N1-0 International Journal of Computational Methods and Experimental Measurements International Journal of Computational Methods and Experimental Measurements 2012 1 1 Article 0 10.2495/CMEM-V1-N1-0 https://www.acadlore.com/article/IJCMEM/2012_1_1/CMEM-V1-N1-0