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Given the small wavelengths and wide range of frequencies of the acoustic waves involved in Aeroacoustics problems, the use of very accurate, low-dissipative numerical schemes is the only valid option to accurately capture these phenomena. However, as the order of the scheme increases, the computational time also increases. In this work, we propose a new high-order flux reconstruction in the framework of finite volume (FV) schemes for linear problems. In particular, it is applied to solve the Linearized Euler Equations, which are widely used in the field of Computational Aeroacoustics. This new reconstruction is very efficient and well suited in the context of very high-order FV schemes, where the computation of high-order flux integrals are needed at cell edges/faces. Different benchmark test cases are carried out to analyze the accuracy and the efficiency of the proposed flux reconstruction. The proposed methodology preserves the accuracy while the computational time relatively reduces drastically as the order increases.

This study outlines the performances of finite-length journal bearing with textured liner, shear-thinning Rabinowitsch lubricants, and considers the elastic deformation of the bearing liner. The yielded nonlinear Rabinowitsch-Reynolds PDE system has been solved using the finite difference method combined with Elrod’s algorithm for the case of cylindrical textures. The static performance of hydrodynamic lubrication, in this case, involves different parameters such as depth of texture, eccentricity ratio, elastic deformation factor, rheological index, etc. Results showed that, at a fixed eccentricity ratio, texturing of the bearing’s converging area enhances significantly the load-carrying capacity and reduces the friction coefficient compared to the smooth bearing surface (up to 22%in load capacity and 17%in friction coefficient). On the other hand, using a lubricant with more pronounced shear-thinning behavior and/or elastic liner reduces the journal bearing performances (up to 25%in load capacity and 30%in pressure). By applying the optimization technique (particle swarm optimization), an optimal arrangement of textures that can compensate for these losses in performance even at high eccentricity has been found. This optimal texture with dimensionless dimple’s depth set to 1 (ry=40μm)improves the load capacity with 10%for a lubricant with a rheological index α¯=0.6and elastic bearing liner with deformation parameter C0=0.05.

In this paper, an optimized design method of PCB integrated common-mode chokes (CMCs) for electromagnetic interferences filters is presented. These CMCs are integrated with custom-shaped ferrite plate cores O, UI, and EI to help realize various low-profile devices. The design of the PCB CMC is based on a dedicated optimization algorithm implemented to characterize compact CMCs with effective common-mode (CM) and differential-mode (DM) inductances taking into account their structures’ geometric parameters and saturation issues of their magnetic plate cores. The algorithm suggests a variety of optimal CMCs configurations using a low computational task. 3D finite element method simulations and analytical modeling of the optimized PCB CMCs are conducted to assess their electromagnetic performances and characterize their high-frequency behavior. The proposed optimization method greatly improves the size compactness of integrated PCB CMCs while effectively controlling the CM and DM saturation levels of their magnetic plate cores. It also enhances the filter’s effectiveness in DM while ensuring CM filtering performance comparable to filters with traditional CMCs.

Flows carrying bottom materials have a wide range of possible applications, especially in the technological and natural fields (Benaissa, Eléments de mécanique des sols. OPU, 1993). These flows that are loaded with granular materials are transport phenomena with diverse and complex mechanisms. They are characterized by the suspension of particles by turbulence, vertical density and velocity profiles, and deposition/erosion processes on the bottom of natural channels as the flow passes. The objective of this research is to experiment with the effects of the rough bottom (Recking, Etude expérimentale de l'influence du tri granulométrique sur le transport solide par charriage, 2006) on the dynamic behaviour of flows carrying solid particles of varying size, to study the behaviour of solid transport under the influence of certain easily accessible parameters, and, finally, to describe, as far as possible, the interactions between the solid particles and the water flow. These flows, responsible for sediment transits, are generally described by: Reynolds number (turbulence intensity), Stokes number (particle inertia), Rouse number, and Froude number (gravity effects). The equations governing the dynamics of particles in turbulence are complex (Gatignol, Journal De Mécanique Théorique Et Appliquée 2:42, 1983; Maxey and Riley, Phys Fluids 26:883, 1983). Most models rely on many simplifications and empirical corrections when the particle Reynolds Rep=Uf-Updνis very high. Experimental studies are therefore always necessary to get around this pitfall. This study is part of a project which consists in evaluating the effects of a rough bottom on the dynamic behaviour of flows carrying solid particles of variable size on a reduced model of a tiltable channel at the Hydraulics Laboratory of the University of Batna 2. The particles are entrained by a fast, turbulent, and supercritical liquid flow. It also consists in numerically simulating the flow of a mixture of fluid and solid particles in a rectangular channel to understand the interactions between the particles and the carrier phase. The study on the laws of friction in river beds aims at evaluating the impact of flows on the materials constituting the bottom of natural channels. The results obtained by simulation using the CLIPPER.5 program and PCA (Principal Component Analysis) are compared with the experimental results from the University of Batna 2. A good agreement is observed between the experimental values and those calculated during the simulation for high Re numbers.

Turbulent flows are characterised by the presence of 'fluctuating scales', or 'structures' of varying magnitude whose effects on mixing, heat transfer and energy dissipation are prominent. The main objective of the study is to explore and exploit two-equation models capable of numerically analysing the dynamic and thermal behaviour of unsteady turbulent incompressible flows, focusing on the variation of temperatures and the rate of turbulent dissipation in a hydraulic structure of complex geometry with its obstacles, erected along the axis of the open channel. The complexity of the physical phenomena taking place in the circular tunnel and the trapezoidal open channel was also emphasised. The work also includes the various numerical simulations that we were able to carry out using the FUENT software, which allowed us to visualise the vortex structures and the energy dissipation. The simulations were carried out using the Reynolds-averaged Navier–Stokes (RANS) model using the closure models: k-ε, RNG k-ε, SST k-ω and K-ω. This model was chosen because it is less expensive in terms of computational time than Direct numerical simulation and large-scale simulations have a very wide range of applications, including heat transfer. The resolution of the incompressible Navier–Stokes equations governing these flows is carried out with the finite volume method, the use of which is particularly motivated by its ability to handle complex geometries. All the simulations were carried out using the FLUENT software, which allowed us to explore, among other things, the turbulent kinetic energy and the temperature distribution in the set-up.

The tribological characteristic of journal bearing systems can be enhanced with the integrating of textures in the contact interfaces, or using the lubricating effect of non-Newtonian fluids. In this study, the combined effects of bearing surface texturing and non-Newtonian lubricants behavior, using micropolar fluid model, on static characteristics of hydrodynamic circular journal bearings of finite length are highlighted. The modified Reynolds equation of micropolar lubrication theory is solved using finite differences scheme and Elrod's mass conservation algorithm, taking into account the presence of the cylindrical texture shape on full and optimum bearing surfaces. The optimization textured area is carried out through particle swarm optimization algorithm, in order to increase the load lifting capacity. Preliminary results are in good agreement with the reference ones, and present an enhancement in the performances of micro-textured journal bearings (load carrying capacity and friction). The results suggest that texturing the bearing convergent zone significantly increases the load carrying capacity and reduce friction coefficient, while fully texturing causes bad performances. It is also shown that the micropolar fluids exhibit better performances for smooth journal bearings than a Newtonian fluid depending on the size of material characteristic length and the coupling number. The combined effects of fully surface textured with micropolar fluids reduce the performance of journal bearing, especially at lower eccentricity ratios. Considering the optimal arrangement of textures on the contact surface, a significant improvement in terms of load capacity and friction can be achieved, particularly at high eccentricity ratios, high material characteristic lengths and high values of the coupling numbers of micropolar fluids.

In Low Pressure Casting (LPC), the counter gravity filling at low velocity and the protective gas atmosphere above the metal can potentially reduce gas and oxides entrapment in the metal. However, the relationship between the imposed gas pressure evolution and the melt filling dynamics cannot be analytically determined as it is geometry-dependent. This issue is the missing link to master and automate the filling step in LPC process. In this work, the filling dynamics is numerically investigated for different mold geometries and pressure ramps. The simulation, carried out using ANSYS Fluent® simulation software, is combined with an analytical model. As the results are quantitatively predictive of the filling flow, it permits to develop a numerical study, considering different sudden or progressive section changes and pressure ramps. The impact of the different process parameters on the flow dynamics is analyzed, particularly the transition smoothing impact.

•High accuracy schemes were employed to solve two-dimensional Navier-Stokes equations.•This study provides a more detailed analysis about the evolution of finger structures.•The density inversion affects the flow pattern, and its motions became asymmetric as nonlinear parameter increase.•The density inversion acts a significant role in the transport of salt/heat and in the mixing process.

•This study offers a comprehensive examination of the resin-bonded sand gravity casting process, focusing on filling, cooling, and solidification, which is crucial for improving casting efficiency and quality.•The research combines 3D numerical simulations and experimental validation, demonstrating the potential of the Smoothed Particle Hydrodynamics (SPH) approach in accurately modeling the filling, cooling, and solidification of the gravity casting process.•Introduction of an experimental test case using two molds, one with transparent glass and one without, enables real-time observation and validation of the filling stage, effectively showcasing the practicality of this methodology.•The study validates the SPH method's reliability in effectively modeling key aspects of fluid dynamics during the filling process, such as filling time, liquid level height, and morphology, as well as the cooling and solidification procedures, in comparison to widely-used software like ProCAST.

This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe. The particles are spherical and are large with respect to the diameter of the pipe (8%, 10%, 16% and 25%). Experiments were done to test the important parameters in solid transport (pressure, velocity, etc.). As a result, the relationship between the pressure gradient forces and the mixture velocity was substantially different from the pure liquid flow. However, in a single-phase flow a monotonous behavior of the pressure drop curve is observed, and the curve of the solid particle flow attains its minimum at the critical velocity. The regimes are characterized with differential pressure measurements and visualizations.

Abstract: This paper proposes an investigation of some important properties of a high-order finite-volume moving least-squares based method (FV-MLSs) for the solution of two-dimensional Euler and Navier–Stokes equations on unstructured grids. A particular attention is paid to the computation of derivatives of shape functions by means of diffuse or full discretization. Furthermore, we introduce the semi-diffuse approach, which is a compromise in terms of accuracy and computational cost. In addition, we investigate the influence of the curvature of wall boundary conditions on the proposed numerical scheme. As expected, we found an improvement when the walls’ curvature is taken into account. However, and differently as in discontinuous Galerkin schemes, the use of a straight representation of the wall normals does not induce a substantial loss of accuracy. Numerical simulations show the accuracy and the robustness of the numerical approach for both inviscid and viscous flows. [Copyright &y& Elsevier]

It is evident that the flow kinematic parameters play a considerable role in the generation of secondary flows within complex geometries and that they affect the hydrodynamic behavior of fluid mixing. The intensity of these parameters has remarkable effects on the mixing performance improvement in passive micromixers. Helicity density, rotation rate, strain rate, and vortex intensity are presented as indispensable tools for the graphical representation of three-dimensional flow fields containing vortex zones. The use of these quantities shows the regions of the flow field with low and strong vorticity regions. In this work, the fluid mixing performances using a short two-layer crossing channel micromixer were analyzed. Navier–Stokes equation, continuity equation, and species transport equation are solved numerically using a CFD code with Reynolds number values between 0.2 and 70. Moreover, the physical model used to assess the mixing quality is the species transport model. The results show that the micromixer with l/W= 1 has a high potential of secondary flows, which promote the enhancement of the hydrodynamic mixing efficiency, where the mixing index exceeded 90% from Re= 20 and reached 99.78% at Re= 70. Moreover, the maximum value of MEC obtained for Re= 70 is equal to 111.48 μW, which represents a low value.

The unsteady aerodynamics computational fluid dynamics simulations of the flow-field around a three-bladed Rutland 503 horizontal axis wind turbine rotor have been conducted in this paper to provide information needed to predict the three-dimensional aerodynamics behavior. In the CFD analysis, the variation of wind velocity between 9.3m/s and 15m/s is investigated. The Detached Eddy Simulation method is used with the turbulence model SST. A multiblock structured mesh is used for the discretization of the study domain. The solutions are obtained by using the Solver Fluent 6.3 which uses the method of finites volumes. The results of simulations obtained are compared with the experimental data [1] obtained in Wind Tunnel Laboratory LMA Arts and Métiers Paris-Tech in order to validate these results. Results of the numerical simulation in three dimensions of the unsteady field of flow around the blade are presented.

In this contribution we present the application of a numerical method based on a mesh free interpolation technique (Moving Least-Squares (MLS)) in a finite volume framework to the computation of turbulent flows. Our approach is based on the monotonically implicit Large Eddy Simulation (MILES). The main idea of MILES methodology is the absence of any explicit subgrid scale (SGS) model in the numerical algorithm to solve turbulent flows. As MLS approximations are used to compute the gradients and higher-order derivatives, the parameters of the kernel function plays a crucial role on the properties of the numerical scheme, particularly on the dispersion and dissipation of the method. This allows us to define an implicit filter that acts as a SGS model in turbulence computations. We present the results for the decay of compressible isotropic turbulence, which are very promising, and the our first results computing turbulence flows in presence of walls.

This paper presents a new sliding mesh technique for the computation of unsteady viscous flows in the presence of rotating bodies. The compressible Euler and incompressible Navier–Stokes equations are solved using a higher-order (>2) finite volume method on unstructured grids. A sliding mesh approach is employed at the interface between computational grids in relative motion. In order to prevent loss of accuracy, two distinct families of higher-order sliding mesh interfaces are developed. These approaches fit naturally in a high-order finite volume framework. To this end, Moving Least Squares (MLS) approximants are used for the transmission of the information from one grid to another. A particular attention is paid for the study of the accuracy and conservation properties of the numerical scheme for static and rotating grids. The capabilities of the present solver to compute complex unsteady vortical flow motions created by rotating geometries are illustrated on a cross-flow configuration. [ABSTRACT FROM AUTHOR]

• A high-order finite volume scheme with adaptive dissipation is presented for the computation of compressible turbulent flows. • The dissipation added by the numerical flux is modified to act as an implicit SGS term. • The a posteriori detection paradigm is used to preserve the stability of the scheme. • Compared with the regular FV scheme we obtain important gains in accuracy. In this work we present an a posteriori high-order finite volume scheme for the computation of compressible turbulent flows. An automatic dissipation adjustment (ADA) method is combined with the a posteriori paradigm, in order to obtain an implicit subgrid scale model and preserve the stability of the numerical method. Thus, the numerical scheme is designed to increase the dissipation in the control volumes where the flow is under-resolved, and to decrease the dissipation in those cells where there is excessive dissipation. This is achieved by adding a multiplicative factor to the dissipative part of the numerical flux. In order to keep the stability of the numerical scheme, the a posteriori approach is used. It allows to increase the dissipation quickly in cells near shocks if required, ensuring the stability of the scheme. Some numerical tests are performed to highlight the accuracy and robustness of the proposed numerical scheme. [ABSTRACT FROM AUTHOR]