Computers & Fluids最新文献_第2页

High-order, refinement-based computation of the volume of an arbitrary polyhedron intersected by an implicitly defined fluid body

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-15 DOI: 10.1016/j.compfluid.2025.106556

Joaquín López

A high-order accurate, efficient and easy-to-implement method is presented for computing the fluid volume bounded by an arbitrary polyhedron, whether it is convex or non-convex, and an implicitly-defined fluid body. This method is an improved version of a previous one that used a recursive local grid refinement of the polyhedron and linear interpolations to determine the intersections of the interface that delimits the fluid body (or simply fluid-body interface) with the polyhedron boundaries. The proposed method first determines the volume of a polyhedral approximation of the bounded fluid region by using a general clipping-lookup and capping procedure valid for arbitrary polyhedra, where the points of intersection between the polyhedron and the fluid-body interface are obtained using a root-finding method rather than linear interpolations. The approximated polyhedral volume is subsequently corrected by using simple Gaussian quadrature rules over a triangulated approximation of the intersected fluid-body interface to achieve high-order accuracy. Recursive local grid refinement of the polyhedron also enables reductions in fluid volume errors. The proposed method requires no assumption of any particular local parametrization of the fluid-body interface, whether paraboloidal or of any other type, or deriving any complex analytical expressions to compute the volume of fluid contained within the polyhedron, thereby making the method easy to implement and generally applicable to any implicitly-defined function. A detailed assessment shows global fourth-order convergent accuracies on structured and unstructured grids even for complex fluid-body interfaces of a high degree. Speedups of several orders of magnitude with respect to the previous refinement method with linear interpolations are achieved even for relatively coarse grids. Comparisons with other methods are also presented, and the software with the implemented method and tests used for the assessment is freely available.

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引用次数: 0

Chemical timescale effects on detonation convergence

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-14 DOI: 10.1016/j.compfluid.2025.106550

Shivam Barwey , Michael Ullman , Ral Bielawski , Venkat Raman

Numerical simulations of detonation-containing flows have emerged as crucial tools for designing next-generation power and propulsion devices. As these tools mature, it is important for the combustion community to properly understand and isolate grid resolution effects when simulating detonations. To this end, the objective of this work is to provide a comprehensive analysis of the numerical convergence of unsteady detonation simulations, with focus on isolating the impacts of chemical timescale modifications on convergence characteristics in the context of operator splitting. With the aid of an AMReX-based adaptive mesh refinement flow solver (Sharma et al., 2024)—which enables resolutions up to

O (1000)

cells-per-induction length—the convergence analysis is conducted using two kinetics configurations: (1) the simplified three-step Arrhenius-based model mechanism of Short and Quirk (1997), where chemical timescales in the detonation are modified by adjusting activation energies in the initiation and branching reactions, and (2) a detailed hydrogen-air mechanism (Mével et al. (2009), Shepherd (2018)), where the chemical timescales are adjusted by varying the ambient pressure. The convergence of unsteady self-sustained detonations in one-dimensional channels is then analyzed with reference to steady-state theoretical baseline solutions using these mechanisms. The goal of the analysis is to provide a detailed comparison of the effects of grid resolution on both macroscopic (peak pressures and wave speeds) and microscopic (wave structure) quantities of interest, drawing connections between the deviations from steady-state baselines and minimum chemical timescales. In particular, chemical timescale reductions were found to have minimal impact on the convergence of macroscopic properties. However, analyses of microscopic convergence trends, particularly in the reaction front location, revealed a key insight: maintaining the induction time while eliminating prohibitive chemical timescales through mechanism simplifications and combustion modeling can significantly enhance detonation convergence properties. Ultimately, this work uncovers resolution-dependent unsteady detonation convergence regimes and highlights the important role played by not only the chemical timescales, but also the ratio between the chemical timescale and induction time on the numerical convergence of the detonation wave structure.

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引用次数: 0

A generalized correction scheme for two-way coupled particle-laden Euler–Lagrange simulations

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-14 DOI: 10.1016/j.compfluid.2025.106554

Thota Srinivas, Gaurav Tomar

A two-way coupled,

3 D

, Euler–Lagrange point particle formulation is proposed that takes into consideration the disturbance in the flow caused by the dispersed particles to obtain the undisturbed fluid flow field essential for the accurate computation of force closure models. Specifically, an advection–diffusion–reaction (ADR) equation for Stokes flow developed by Pakseresht and Apte (Pakseresht and Apte, 2021) for obtaining the disturbance flow field created by the particle is extended to non-Stokesian flow conditions. Using the solution for flow over a cylinder, an ADR equation for obtaining the disturbance flow field created by a particle in pseudo-

2 D

flows is derived. The present technique for non-Stokesian flows performs significantly better than the existing Stokesian correction scheme, especially for higher particle Stokes numbers and particle-to-grid spacing ratios. The extension of the present technique to the porous particles is examined using two test cases, namely, the settling of porous particles under gravity in a quiescent fluid and porous particles subjected to the oscillating body force field. The present technique is straightforward to implement in all existing Euler–Lagrange solvers based on either ADR or zonal-advection–diffusion–reaction (Zonal-ADR) model.

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引用次数: 0

Mixed subfilter-scale models for large-eddy simulation of decaying isotropic turbulence using an artificial neural network

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-13 DOI: 10.1016/j.compfluid.2025.106557

Dong Li , Lei Yang , Kai Zhang , Kun Luo , Jianren Fan

This study is concerned with the development of a new subfilter-scale (SFS) stress model for large-eddy simulation (LES) of decaying isotropic turbulence using an artificial neural network (ANN). Both a priori and a posteriori tests are performed to investigate the effect of input variables on the performance of ANN-based SFS models. Within the range of parameters and flow types considered, the ANN-based model with filtered strain-rate tensor as input is found to show excellent predictions of the resolved statistics in a posteriori test, although it provides low correlation coefficients between the true and predicted SFS stresses in a priori test. However, this model performs poorly in the predictions of the SFS statistics and backscatter. On the other hand, the predictive accuracy of ANN-based models is significantly improved by using a combination of the strain-rate tensor and the modified Leonard stress tensor as input variables. The proposed ANN-based mixed SFS model not only can predict the backscatter, but also exhibits better performance in predicting the resolved and SFS statistics than the traditional dynamic models. In particular, the ANN-based mixed model shows an advantage over the dynamic two-parameter mixed model in terms of the accuracy and computational efficiency.

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引用次数: 0

Modeling plant canopy through numerical simulation of cylindrical array

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-11 DOI: 10.1016/j.compfluid.2025.106551

Ning Huang, Jialiang Sun, Yuhao Zhao, Jie Zhang, Binbin Pei

Vegetation is frequently utilized in windbreak engineering, yet the flow characteristics in the wake region and its interactions with airflow remain unresolved due to the heterogeneous geometry of canopy. By simplifying the canopy structure geometry as an array of cylinders with varying porosity, this works aims to reveal the flow characteristics and turbulence in the wake region of canopy flow using Large-Eddy Simulation. Meanwhile, the cylinder array is simplified using a porous-media model simulated by the k-epsilon turbulence model. A comparison of the two numerical methods reveals that employing the porous media model yields a better computational efficiency without much effect on the accuracy of the simulated steady flow region. More specifically, the RANS coupled with porous media model improves the computational efficiency by four times, while the maximal deviation in the steady flow region approaches 11%. We also analyze the dynamic mechanisms of turbulence structures in the wake region of the cylindrical array, and how vorticity fields vary with porosity. It is found that the increase in canopy porosity enlarge its protected area. Finally, an empirical model suitable for canopy vegetation is presented by analyzing the relationship between porosity and resistance coefficient.

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引用次数: 0

Three-dimensional optimization of a 1.5-stage axial compressor based on a novel local adaptive ensemble surrogate model

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-10 DOI: 10.1016/j.compfluid.2025.106553

Yitong Liu , Wuqi Gong , Lu Liang , Ya Li , Qi Wang

Accurately predicting the performance of a compressor is of utmost importance when utilizing intelligent optimization algorithms. To improve the prediction accuracy, a novel local adaptive ensemble surrogate model (LAESM) is proposed. In this model, independent individual surrogate model screening and weight calculation are carried out for each point to be predicted according to a unique local performance index, with the purpose of giving full play to the local advantages of different individual surrogate models. 24 numerical functions are used to test the LAESM and some other surrogate models, and it is observed that the LAESM demonstrated better accuracy and stability when compared to other surrogate models. Meanwhile, a simulation failure processing method based on SVM classification model (FP-SVM) is proposed, and a one-dimensional function is used to show the feasibility of this method. Combining the LAESM and FP-SVM, a 1.5-stage axial compressor is optimized. A total of 18 design variables and 6 objective functions are considered in the optimization, and 626 samples are calculated using the RANS method for the training. The results show that after optimization, the efficiency, pressure ratio, and stable operating range of the axial compressor are improved. By observing the flow field, it is found that the flow loss inside the compressor is obviously reduced as a result of adjusting the rotor blade profile. The method proposed in this study has the potential to serve as a reference for optimization problems in the field of turbomachinery.

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引用次数: 0

A robust monolithic nonlinear Newton method for the compressible Reynolds averaged Navier–Stokes Equations

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-09 DOI: 10.1016/j.compfluid.2025.106549

Hulya Sukas, Mehmet Sahin

The goal of this work is the development of a fully monolithic nonlinear Newton algorithm for the unstructured vertex-based finite volume algorithm presented in [Akkurt and Sahin, An efficient edge based data structure for the compressible RANS equations on hybrid unstructured meshes. International Journal for Numerical Methods in Fluids, 94:13-31, (2022)]. A special attention is paid for the highly accurate construction of the first- and second-order Jacobian matrices for the Navier–Stokes equations and the one-equation negative Spalart–Allmaras turbulence model. The inviscid flux Jacobian matrices are evaluated exactly using the source code transformations provided by the INRIA Tapenade library. The implementation of the nonlinear Newton method is carried out using the PETSc Scalable Nonlinear Equations Solvers (SNES) with a line search technique. The method can utilize both the Jacobian-free finite difference and direct approaches for the Jacobian vector product. The INRIA pyAMG anisotropic mesh adaptation library has been integrated in order to further improve its numerical accuracy at a lower computational cost. The algorithm has been applied to the two- and three-dimensional mesh convergence test cases from the 4th AIAA CFD High Lift Prediction Workshop in order to demonstrate its robustness in achieving machine precision for a realistic high-lift system. The highly accurate Jacobian evaluation process and high CFL numbers are found to be very critical for achieving machine precision. The mesh adaptation is also proven to be very robust in refining regions with high gradients, which is especially important for the simulations at high angles of attack, where it is rather difficult to determine refinement regions a priori. The anisotropic mesh adaptation studies are carried out for up to 92,993,470 vertices in three-dimensions, and the numerical results indicate very good agreement with the committee’s experimental data.

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引用次数: 0

Perturbed polynomial reconstructed seventh-order hybrid WENO scheme with improved accuracy and resolution

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-06 DOI: 10.1016/j.compfluid.2025.106548

Tao Yang, Dazhi Sun, Qijun Zhao, Guoqing Zhao, Xi Chen

Non-polynomial reconstructions can be employed to enhance the performance of the WENO-type schemes by optimizing the inherent hyper-parameter. In contrast to the non-polynomial RBF-based and the Gauss-Kriging reconstructions, the perturbed polynomial reconstruction exhibits good portability and expandability. In this work, a novel seventh-order WENO scheme, denoted as the HPWENO7 scheme, is proposed by incorporating the concept of the perturbed polynomial reconstructions into the standard seventh-order WENO7-JS scheme (Jiang and Shu, 1996, [6]). Firstly, a refined troubled cell indicator is developed to categorize the global stencils as either smooth or non-smooth. Subsequently, perturbed polynomial reconstruction with double free-parameters, the values of which can be adjusted automatically according to the features of local regions, is developed to optimize the fluxes within the four-point candidate stencils. Adaptive optimization of the free-parameter values enables a minimum one-order improvement in accuracy. Finally, the novel HPWENO7 scheme is proposed by combining the seventh-order upstream central scheme for smooth stencils with the perturbed polynomial reconstruction optimized candidate fluxes for non-smooth stencils. Numerical examples show that the HPWENO7 scheme achieves fifth-order of accuracy in the four-point candidate stencils, providing sharper solutions for discontinuities and significantly higher resolution for small-scale vortex structures around the discontinuities.

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引用次数: 0

Analysis of the central-moments-based lattice Boltzmann method for the numerical modelling of the one-dimensional advection-diffusion equation: Equivalent finite difference and partial differential equations

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-02 DOI: 10.1016/j.compfluid.2024.106535

Goncalo Silva

This work presents a detailed theoretical analysis of the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM), formulated on central moment (CM) space, for the numerical modelling of the one-dimensional advection-diffusion equation (ADE) with a constant velocity and diffusion coefficient, based on the D1Q3 lattice. Other LBM collision operators, such as single-relaxation-time Bhatnagar–Gross–Krook (BGK), regularized (REG) and MRT in raw moment (RM) space are also considered in this study. Without recurring to asymptotic analyses, such as the Chapman–Enskog expansion, we investigate the approximation of the MRT-CM with respect to the ADE by deriving its equivalent finite difference (EFD) scheme, which obeys an explicit four-level finite difference scheme at discrete level. Its steady-state limit follows a standard central differencing scheme for the steady ADE, yet with possible artefacts in the effective diffusion coefficient. Then, through the Taylor expansion of the EFD scheme, a detailed accuracy analysis, based on the equivalent partial differential (EPD) equation, reveals the leading order truncation errors associated with each collision model under study. Although MRT-CM and MRT-RM models have similar error structures, the former has a much reduced and simpler form, particularly in the dispersion error term, which might explain the improved Galilean invariance of the CM model. Through a suitable combination of the MRT free parameters (either in RM or CM bases), it is possible to improve its accuracy from second- to fourth-order. After that, we study the necessary and sufficient stability conditions of the MRT-CM, and its relation with other collision operators, based on the von Neumann stability analysis of the derived EFD schemes. Unexpectedly, the MRT-CM appears to support a narrower stability domain than the MRT-RM model, particularly at higher advection velocities, which can be tracked down to the inclusion of additional terms in the stability condition of the former that scale with higher order polynomials of the advection velocity. Finally, some numerical tests for the ADE on 1D unbounded domains are conducted, which confirm this work theoretical conclusions on the MRT-CM performance.

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引用次数: 0

New higher-order super-compact scheme to study the uniform and non-uniform wall heating effect on 3D MHD natural convection and entropy generation

IF 2.5 3区工程技术 Q3 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS

Computers & Fluids

Pub Date : 2025-01-01 DOI: 10.1016/j.compfluid.2024.106538

Ashwani Punia, Rajendra K. Ray

<div><div>This research introduces a new higher-order super-compact (HOSC) finite difference scheme to study magnetohydrodynamic (MHD) natural convection within a 3D cubic cavity filled with molten lithium. The HOSC scheme, implemented for the first time in this context, provides an advanced analysis of the thermal behavior under various wall heating conditions, including uniform and non-uniform heating. The study comprehensively explores the effects of different Hartmann numbers (<span><math><mrow><mi>H</mi><mi>a</mi><mo>=</mo><mn>25</mn><mo>,</mo><mn>50</mn><mo>,</mo><mn>100</mn><mo>,</mo><mn>150</mn></mrow></math></span>) and Rayleigh numbers (<span><math><mrow><mi>R</mi><mi>a</mi><mo>=</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>3</mn></mrow></msup><mo>,</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup><mo>,</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>), with a fixed Prandtl number (<span><math><mrow><mi>P</mi><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>065</mn></mrow></math></span>) for molten lithium. Three distinct heating scenarios on the left wall (<span><math><mrow><mi>x</mi><mo>=</mo><mn>0</mn></mrow></math></span>) of the cubic cavity are investigated: uniform heating (<span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>θ</mi></mrow></msub><mo>=</mo><mn>1</mn></mrow></math></span>), <span><math><mi>y</mi></math></span>-dependent non-uniform heating (<span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>θ</mi></mrow></msub><mo>=</mo><mo>sin</mo><mrow><mo>(</mo><mi>π</mi><mi>y</mi><mo>)</mo></mrow></mrow></math></span>), and combined <span><math><mi>y</mi></math></span> and <span><math><mi>z</mi></math></span>-dependent non-uniform heating (<span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>θ</mi></mrow></msub><mo>=</mo><mo>sin</mo><mrow><mo>(</mo><mi>π</mi><mi>y</mi><mo>)</mo></mrow><mo>sin</mo><mrow><mo>(</mo><mi>π</mi><mi>z</mi><mo>)</mo></mrow></mrow></math></span>). The results show that the HOSC scheme effectively captures the impact of varying <span><math><mrow><mi>H</mi><mi>a</mi></mrow></math></span> and <span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span> on the temperature distribution and flow field, revealing that increased <span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span> enhances heat transfer due to stronger convection, while higher <span><math><mrow><mi>H</mi><mi>a</mi></mrow></math></span> reduces heat transfer by slowing fluid motion. Notably, as <span><math><mrow><mi>R</mi><mi>a</mi></mrow></math></span> increases from <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>3</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span> at a fixed <span><math><mrow><mi>H</mi><mi>a</mi><mo>=</mo><mn>25</mn></mrow></math></span>, the maximum Nusselt number (<span><math><mrow><mi>N</mi><msub><mrow><mi>u</mi><

引用次数: 0