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The purpose of this study is to investigate the accuracy and applicability of the Flowfield Dependent Variation (FDV) method for large-eddy simulations (LES) of decaying isotropic turbulence.

In an earlier paper, the FDV method was successfully demonstrated for simulations of laminar flows with speeds varying from low subsonic to high supersonic Mach numbers. In the current study, the FDV method, implemented in a finite element framework, is used to perform LESs of decaying isotropic turbulence. The FDV method is fundamentally derived from the Lax–Wendroff Scheme (LWS) by replacing the explicit time derivatives in LWS with a weighted combination of explicit and implicit time derivatives. The increased implicitness and the inherent numerical dissipation of FDV contribute to the scheme’s numerical stability and monotonicity. Understanding the role of numerical dissipation that is inherent to the FDV method is essential for the maturation of FDV into a robust scheme for LES of turbulent flows. Accordingly, three types of LES of decaying isotropic turbulence were performed. The first two types of LES utilized explicit subgrid scale (SGS) models, namely, the constant-coefficient Smagorinsky and dynamic Smagorinsky models. In the third, no explicit SGS model was employed; instead, the numerical dissipation inherent to FDV was used to emulate the role played by explicit SGS models. Such an approach is commonly known as Implicit LES (ILES). A new formulation was also developed for quantifying the FDV numerical viscosity that principally arises from the convective terms of the filtered Navier–Stokes equations.

The temporal variation of the turbulent kinetic energy and enstrophy and the energy spectra are presented and analyzed. At all grid resolutions, the temporal profiles of kinetic energy showed good agreement with t^(−1.43) theoretical scaling in the fully developed turbulent flow regime, where t represents time. The energy spectra also showed reasonable agreement with the Kolmogorov’s k^(−5/3) power law in the inertial subrange, with the spectra moving closer to the Kolmogorov scaling at higher-grid resolutions. The intrinsic numerical viscosity and the dissipation rate of the FDV scheme are quantified, both in physical and spectral spaces, and compared with those of the two SGS LES runs. Furthermore, at a finite number of flow realizations, the numerical viscosities of FDV and of the Streamline Upwind/Petrov–Galerkin (SUPG) finite element method are compared. In the initial stages of turbulence development, all three LES cases have similar viscosities. But, once the turbulence is fully developed, implicit LES is less dissipative compared to the two SGS LES runs. It was also observed that the SUPG method is significantly more dissipative than the three LES approaches.

Just as any computational method, the limitations are based on the available computational resources.

Solving problems involving turbulent flows is by far the biggest challenge facing engineers and scientists in the twenty-first century, this is the road that the authors have embarked upon in this paper and the road ahead of is very long.

Understanding turbulence is a very lofty goal and a challenging one as well; however, if the authors succeed, the rewards are limitless.

The derivation of an explicit expression for the numerical viscosity tensor of FDV is an important contribution of this study, and is a crucial step forward in elucidating the fundamental properties of the FDV method. The comparison of viscosities for the three LES cases and the SUPG method has important implications for the application of ILES approach for turbulent flow simulations.

It has been verified that the WBZ‐α method of Wood, Bossak and Zienkiewicz can have unconditional stability and numerical dissipation for linear elastic systems. However, it is still unclear about its performance in the solution of nonlinear systems analytically. Hence, this study proposes to analytically investigate its numerical characteristics for solving nonlinear systems.

Two parameters are introduced to facilitate the basic analysis for nonlinear systems. One is the step degree of nonlinearity, which describes the stiffness change within a time step, and the other is the step degree of convergence, which describes the convergence error due to an iteration procedure.

It is theoretically proved that the sub‐family of WBZ‐α method of −1≤α<0, β=(1/4)(1−α)² and γ=(1/2)−α is unconditionally stable and has desired numerical dissipation for any nonlinear systems even with the presence of convergence error. These theoretical results are confirmed by numerical examples.

This analytical study reveals that the performance of the WBZ‐α method for nonlinear systems is in general the same as that for linear elastic systems.

The purpose of this study is to present and demonstrate a numerical method for solving chemically reacting flows. These are important for energy conversion devices, which rely on chemical reactions as their operational mechanism, with heat generated from the combustion of the fuel, often gases, being converted to work.

The numerical study of such flows requires the set of Navier-Stokes equations to be extended to include multiple species and the chemical reactions between them. The numerical method implemented in this study also accounts for changes in the material properties because of temperature variations and the process to handle steep spatial fronts and stiff source terms without incurring any numerical instabilities. An all-speed numerical framework is used through simple low-dissipation advection upwind splitting (SLAU) convective scheme, and it has been extended in a multi-component species framework on the in-house density-based flow solver. The capability of solving turbulent combustion is also implemented using the Eddy Dissipation Concept (EDC) framework and the recent k-kl turbulence model.

The numerical implementation has been demonstrated for several stiff problems in laminar and turbulent combustion. The laminar combustion results are compared from the corresponding results from the Cantera library, and the turbulent combustion computations are found to be consistent with the experimental results.

This paper has extended the single gas density-based framework to handle multi-component gaseous mixtures. This paper has demonstrated the capability of the numerical framework for solving non-reacting/reacting laminar and turbulent flow problems. The all-speed SLAU convective scheme has been extended in the multi-component species framework, and the turbulent model k-kl is used for turbulent combustion, which has not been done previously. While the former method provides the capability of solving for low-speed flows using the density-based method, the later is a length-scale-based method that includes scale-adaptive simulation characteristics in the turbulence modeling. The SLAU scheme has proven to work well for unsteady flows while the k-kL model works well in non-stationary turbulent flows. As both these flow features are commonly found in industrially important reacting flows, the convection scheme and the turbulence model together will enhance the numerical predictions of such flows.

A flux‐upwind finite element method is developed for the carrier transport equations in semiconductor device modeling. Our approach is motivated by the streamline upwind methods that have proven effective in fluid mechanics. The procedure reduces precisely to the Scharfetter‐Gummel approach in one dimension. In higher‐dimensions, however, it differs from this classical technique and is shown here to generate more accurate solutions with less numerical dissipation. Numerical results are presented for representative MOSFET and p‐n junction devices to illustrate this point. Both upwind techniques have been implemented in conjunction with an adaptive finite element refinement procedure for better layer resolution and yield a more stable algorithm.

The paper aims to assess the feasibility of locally turbulence-resolving flow simulations for a high-lift aircraft configuration near maximum lift. It addresses the aspects of proper grid design and explores the ability of the hybrid turbulence model and the numerical scheme to automatically select adequate modes in different flow regions. By comparison with experimental and numerical reference data, the study aims to provide insights into the predictive potential of the method for high-lift flows.

The paper applies numerical flow simulations using well-established tools such as DLR's (German Aerospace Center) TAU solver and the SOLAR grid generator to study “Improved Detached Delayed Eddy Simulations” of the Japan Aerospace Exploration Agency (JAXA) Standard Model at two angles of attack near maximum lift. The simulations apply a hybrid low-dissipation low-dispersion scheme and implicit time stepping with adequate temporal resolution. The simulation results, including pressure distributions and near-wall flow patterns, are assessed by comparison with experimental wind-tunnel data.

Apart from demonstrating the general feasibility of the numerical approach for complex high-lift flows, the results indicate somewhat improved maximum lift predictions compared to the Spalart–Allmaras model, which is consistent with a slightly closer agreement with measured pressure distributions and oil-flow pictures. However, the expected lift breakdown caused by an increasing inboard separation in the experiment is not well captured.

The study not only provides new insight into the feasibility and promising potential of hybrid turbulence-resolving methods for relevant high-lift aircraft flows but also indicates the need for further research on the numerical sensitivities, such as grid resolution or flow initialization.

The purpose of this paper is to report a novel formulation of convective heat transfer source term for the case of flow through porous medium.

The novel formulation is obtained by analytical solution of an idealized dual problem. Computations are performed by dedicated tool for fixed bed combustion named GRATECAL and developed by the authors. However, the proposed method can also be applied to other porous media flow problems.

The new source term formulation is unconditionally stable and it respects exponential decay of temperature difference between the fluid and porous solid medium.

The results of this work are applicable in the simulation of convective heat transfer between the fluid and porous medium. Applications include e.g. fixed bed combustion, catalytic reactors and lime kilns.

The reported solution is believed to be original. It will be useful to all involved in numerical simulations of fluid flow in porous media with convective heat transfer.

The purpose of this paper is to study turbulent flow separation at the airfoil trailing edge. This work aims to improve the knowledge of stall phenomenon by creating a QDNS database for the NACA412 airfoil.

Quasi-DNS simulations of the NACA 4412 airfoil in pre-stall conditions have been completed. The Reynolds number based on airfoil chord and freestream velocity is equal to 0.35 million, and the freestream Mach number to 0.117. Transition is triggered on both surfaces for avoiding the occurrence of laminar separation bubbles and to ensure turbulent mixing in the wake. Four incidences have been considered, 5, 8 10 and 11 degrees.

The results obtained show a reasonably good correlation of the present simulations with classical MSES airfoil simulations and with RANS computations, both in terms of pressure and skin-friction distribution, with an earlier and more extended flow separation in the QDNS. The database thus generated will be deeply analysed and enriched for larger incidences in the future.

No experimental or HPC numerical database at reasonable Reynolds number exists in the literature. The current work is the first step in that direction.

Presents three non‐isothermal, time dependent, three dimensional examples having cylindrical geometries to show the significant effort of numerical precision and dissipation on rotating flow predictions. The examples are relevant to turbomachinery design and geophysical studies. Discusses the relationship between numerical precision, numerical dissipation and co‐ordinate system angular velocity. Compares predictions made in stationary and rotating co‐ordinate systems, using contour plots of dimensionless stream function and temperature. Shows that wrong, axisymmetric solutions are predicted if the co‐ordinate system is not selected to minimize relative tangential velocities/Peclet numbers, thereby increasing numerical precision and reducing dissipation.

Aiming at the characteristics of large stiffness, low ductility, and poor energy dissipation capacity of cross-laminated timber (CLT) shear wall, a method of opening vertical joints and adding low-yield dampers in CLT shear wall is proposed to improve its energy dissipation capacity and ductility.

The finite element model of CLT shear walls with low-yield dampers and dampers assembly was established by ABAQUS. The structural shape of low-yield dampers that meet the requirements of vertical joints in CLT shear walls is studied by numerical analysis. The influence of the number and position of low-yield dampers on the energy dissipation of the shear wall system is studied.

The results show that the low-yield damper with diamond openings should be used in the CLT shear wall, and the energy dissipation effect is the best when the CLT shear wall is uniformly covered with low-yield dampers. After the uniform arrangement of four groups of low-yield steel dampers, the energy consumption of the CLT shear wall increases by 75.38%, and the ductility increases by 13.22%.

There are few studies on replacing connectors between shear walls with low-yield steel dampers, and rectangular soft steel dampers are prone to stress concentration and poor deformation capacity. Therefore, this paper establishes the model of perforated low-yield damper and CLT and makes numerical analysis to determine the opening form, geometric parameters of low-yield damper, and the optimal layout scheme in CLT shear wall.

Isotropic artificial dissipation is added to the Navier‐Stokes equations along with a correction term which cancels the artificial dissipation term in the limit when the mesh size is zero. For a finite mesh size, the correction term replaces the artificial viscosity terms with hyperviscosity terms, i.e., with an artificial dissipation which depends on the fourth derivatives of the velocity. Hyperviscosity more effectively suppresses the higher wave number modes and has a smaller effect on the inertial modes of the flow field than does artificial viscosity. This scheme is implemented using the finite element method and therefore the required amount of dissipation is determined by analysing the discretization on a finite element. The scheme is used to simulate the flow in a driven cavity and over a backward facing step and the results are compared to existing results for these cases.