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 mean

film thickness show a fairly good agreement with the empirical correlations and the measurements of

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 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.

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.

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.

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.

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.

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.

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.