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.

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.

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.

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.

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.

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.

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.