Computers & Fluids最新文献_第8页

A coupled immersed boundary method and wall modelling framework for high-Reynolds number flows over complex terrain 复杂地形上高雷诺数流动的沉浸边界法与壁面建模耦合框架

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

Computers & Fluids

Pub Date : 2024-10-23 DOI: 10.1016/j.compfluid.2024.106457

Jay A. Patel , Ankita Maity , Niranjan S. Ghaisas

We present the development and validation of an immersed boundary method (IBM) along with a wall model (WM) to simulate atmospheric boundary-layer flows over complex terrain. The framework presented here has two novel aspects over standard IBM implementations. First, the underlying schemes are global in nature and require specification of values throughout the solid region. Second, to enable high-Reynolds number simulations, a wall model is coupled to the IBM. The proposed numerical framework is shown to have second-order accuracy. The framework is validated by simulating flow over a 2D as well as 3D cosine-squared hill and comparing to previously published experimental results. The mean velocity and turbulence intensity are reproduced accurately by our LES. The flow over the Bolund hill, marked by steep slopes which makes this a challenging test case, is also simulated and results are compared to field observations showing good agreement. The framework also accurately reproduces the turbulent statistics in the wake of a turbine situated on a flat terrain, with the flat terrain modelled using the IBWM framework, thus demonstrating its applicability to high-Reynolds number atmospheric and wind farm flows over complex terrain.

我们介绍了沉浸边界法（IBM）和壁面模型（WM）的开发和验证情况，以模拟复杂地形上的大气边界层流动。与标准的 IBM 实现相比，这里介绍的框架有两个新颖之处。首先，基础方案是全局性的，需要指定整个固体区域的数值。其次，为实现高雷诺数模拟，壁面模型与 IBM 相耦合。研究表明，所提出的数值框架具有二阶精度。通过模拟二维和三维余弦平方山的流动，并与之前公布的实验结果进行比较，验证了该框架的有效性。我们的 LES 准确地再现了平均速度和湍流强度。博伦德山丘上有陡峭的斜坡，这使其成为一个具有挑战性的测试案例，我们也模拟了博伦德山丘上的气流，并将结果与现场观测结果进行了比较，结果显示两者吻合良好。该框架还精确再现了位于平坦地形上的涡轮机尾流中的湍流统计数据，平坦地形使用 IBWM 框架进行建模，从而证明了该框架适用于复杂地形上的高雷诺数大气和风电场气流。

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引用次数: 0

Resolving subgrid-scale structures for multiphase flows using a filament moment-of-fluid method 利用丝状流体力矩法解析多相流的亚网格尺度结构

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

Computers & Fluids

Pub Date : 2024-10-22 DOI: 10.1016/j.compfluid.2024.106455

Philippe Hergibo , Timothy N. Phillips , Zhihua Xie

Multiphase flows are present in many industrial and engineering applications as well as in some physical phenomena. Capturing the interface between the phases for complex flows is challenging and requires an accurate method, especially to resolve fine-scale structures. The moment-of-fluid (MOF) method improves drastically the accuracy of interface reconstruction compared to previous geometrical methods. Instead of refining the mesh to capture increased levels of detail, the MOF method, which uses zeroth and first moments as well as a conglomeration algorithm, enables subgrid structures such as filaments to be captured at a small extra cost. Coupled to a finite volume Navier–Stokes solver, the MOF method has been tested on a fixed grid and validated using well-known benchmark problems such as dam break flows, the Rayleigh–Taylor and Kelvin–Helmholtz instability problems, and a rising bubble. The ability of the novel filament MOF method to capture the filamentary structures that eventually form for the Rayleigh–Taylor instability and rising bubble problems is assessed. Good agreement has been found with other numerical results and experimental measurements available in the literature.

多相流存在于许多工业和工程应用以及某些物理现象中。捕捉复杂流动中各相间的界面具有挑战性，需要一种精确的方法，尤其是解决细尺度结构的方法。与以前的几何方法相比，流体动量（MOF）方法大大提高了界面重建的精确度。MOF 方法使用零矩和一阶矩以及聚合算法，无需细化网格来捕捉更多细节，只需少量额外成本就能捕捉到细丝等亚网格结构。MOF 方法与有限体积纳维-斯托克斯求解器耦合，已在固定网格上进行了测试，并使用著名的基准问题进行了验证，如水坝断流、瑞利-泰勒和开尔文-赫尔姆霍兹不稳定性问题以及上升气泡。评估了新型丝状 MOF 方法捕捉雷利-泰勒不稳定性和上升气泡问题最终形成的丝状结构的能力。研究发现，该方法与其他数值结果和文献中的实验测量结果具有良好的一致性。

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引用次数: 0

An evaluation of the hybrid Fokker–Planck-DSMC approach for high-speed rarefied gas flows 高速稀薄气体流的福克-普朗克-DSMC 混合方法评估

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

Computers & Fluids

Pub Date : 2024-10-22 DOI: 10.1016/j.compfluid.2024.106456

Sanghun Kim, Eunji Jun

The Direct Simulation Monte Carlo (DSMC) method has been widely used for simulations of rarefied gas flows. It has been proven that the numerical solution of the DSMC method converges to the Boltzmann equation, providing a solid physical foundation for high Knudsen numbers. However, many aerospace engineering problems include both low and high-density regions in a single domain, making the DSMC method computationally expensive. Over the past decade, the particle Fokker–Planck (FP) method has been studied as a means to reduce computational costs near the continuum regime. While enhancing efficiency, the FP method loses physical accuracy at high Knudsen numbers. Aiming for universal accuracy and efficiency across the whole range of Knudsen numbers, the hybrid FP-DSMC method has been studied. Nevertheless, consistent comparisons among the DSMC, FP, and hybrid FP-DSMC methods have received limited attention so far. This paper presents a consistent comparative study of the DSMC, FP, and hybrid FP-DSMC methods to assess the accuracy and efficiency of the hybrid FP-DSMC method. The hybrid FP-DSMC solver is developed based on the open-source SPARTA framework. The benchmark problems include supersonic flow in a planar nozzle, hypersonic flow around a cylinder, and hypersonic flow around a THAAD-like missile. The results demonstrate that the hybrid FP-DSMC method can be more efficient than the DSMC method while being more accurate than the FP method. The speed-up achieved by the FP-DSMC method ranged from 1.5 to 14 times compared to the converged DSMC simulation.

直接模拟蒙特卡罗（DSMC）方法已被广泛用于稀薄气体流动的模拟。实践证明，DSMC 方法的数值解收敛于玻尔兹曼方程，为高努森数提供了坚实的物理基础。然而，许多航空航天工程问题包括单个域中的低密度和高密度区域，这使得 DSMC 方法的计算成本非常昂贵。在过去的十年中，粒子福克-普朗克（FP）方法一直被作为一种降低连续系统计算成本的方法来研究。在提高效率的同时，FP 方法在高 Knudsen 数时失去了物理精度。为了在整个 Knudsen 数范围内实现普遍的精度和效率，人们研究了 FP-DSMC 混合方法。然而，迄今为止，DSMC、FP 和 FP-DSMC 混合方法之间的一致性比较受到的关注还很有限。本文对 DSMC、FP 和混合 FP-DSMC 方法进行了一致的比较研究，以评估混合 FP-DSMC 方法的准确性和效率。混合 FP-DSMC 求解器是基于开源 SPARTA 框架开发的。基准问题包括平面喷嘴中的超音速流动、围绕圆柱体的高超声速流动以及围绕类似于 THAAD 导弹的高超声速流动。结果表明，FP-DSMC 混合方法比 DSMC 方法更高效，同时比 FP 方法更精确。与收敛后的 DSMC 仿真相比，FP-DSMC 方法的速度提高了 1.5 到 14 倍。

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引用次数: 0

An improved pressure gradient method for viscous incompressible flows 粘性不可压缩流的改进压力梯度法

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

Computers & Fluids

Pub Date : 2024-10-22 DOI: 10.1016/j.compfluid.2024.106448

Zhisong Li , Ye Li

The pressure gradient method solves the viscous incompressible flow with the pressure gradients, rather than the pressure, as unknown variables. Two variants of the pressure gradient method have been developed in the past but have not received much attention due to their unsatisfactory performance or implementation complexity. Based on the artificial compressibility concept, this study proposes an improved pressure gradient method. One distinct feature of this method is that it requires no pressure/pressure gradient boundary condition or special treatment on wall boundaries. An auxiliary variable is introduced to represent the velocity dilatation, greatly simplifying the spatial discretization and computational procedure. The mathematical formulations are elaborated and compared with the previous pressure gradient methods, followed by discussions of compatibility relationships, boundary condition setup, and an extension to a pressure Poisson-like equation. Four validation examples are performed for various flow scenarios, and the solutions and domain solenoidity are examined for each case. The study also compares associated computational methods, different pressure boundary conditions, and flow characteristics, demonstrating the benefits of the present method.

压力梯度法以压力梯度而非压力作为未知变量来求解粘性不可压缩流动。压力梯度法的两个变体在过去已被开发出来，但由于其性能不理想或实施复杂，并未受到广泛关注。基于人工可压缩性概念，本研究提出了一种改进的压力梯度法。该方法的一个显著特点是不需要压力/压力梯度边界条件，也不需要对壁面边界进行特殊处理。引入了一个辅助变量来表示速度扩张，从而大大简化了空间离散和计算过程。详细阐述了数学公式，并与之前的压力梯度方法进行了比较，随后讨论了兼容性关系、边界条件设置以及压力泊松方程的扩展。针对不同的流动情况进行了四次验证，并检查了每种情况下的解决方案和域电磁性。研究还比较了相关的计算方法、不同的压力边界条件和流动特性，展示了本方法的优势。

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引用次数: 0

Boundary conditions for SPH through energy conservation 通过能量守恒实现 SPH 的边界条件

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

Computers & Fluids

Pub Date : 2024-10-18 DOI: 10.1016/j.compfluid.2024.106454

Jose Luis Cercos-Pita , Daniel Duque , Pablo Eleazar Merino-Alonso , Javier Calderon-Sanchez

Dealing with boundary conditions in Smoothed Particle Hydrodynamics (SPH) poses significant difficulties, indeed being one of the SPHERIC Grand Challenges. In particular, wall boundary conditions have been pivotal in SPH model development since it evolved from astrophysics to more generic fluid dynamics simulations. Despite considerable attention from researchers and numerous publications dedicated to formulating and assessing wall boundary conditions, few of them have addressed the crucial aspect of energy conservation. This work introduces a novel boundary condition designed with energy conservation as a primary consideration, effectively extending the unconditional stability of SPH to problems involving wall boundary conditions. The result is formulated within the framework of the Boundary Integrals technique. The proposal is tested on a number of cases: normal impact against a wall, adiabatic oscillations of a piston, dam break, and the water landing of a spacecraft.

处理平滑粒子流体力学（SPH）中的边界条件是一个重大难题，实际上也是 SPHERIC 大挑战之一。特别是，自从平滑粒子流体力学（SPH）从天体物理学发展到更通用的流体动力学模拟以来，壁面边界条件一直是 SPH 模型发展的关键。尽管研究人员对制定和评估壁边界条件给予了极大关注，并发表了大量相关论文，但很少有论文涉及能量守恒这一关键问题。这项研究引入了一种以能量守恒为主要考虑因素的新型边界条件，有效地将 SPH 的无条件稳定性扩展到涉及壁边界条件的问题。这一结果是在边界积分技术的框架内提出的。该提议在多种情况下进行了测试：对墙壁的正常撞击、活塞的绝热振荡、水坝破裂以及航天器的水上着陆。

引用次数: 0

Effects of two-dimensional reed oscillation on airflow and sound generation in a single-reed instrument 二维哨片振荡对单簧乐器气流和发声的影响

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

Computers & Fluids

Pub Date : 2024-10-17 DOI: 10.1016/j.compfluid.2024.106452

Tsukasa Yoshinaga , Reo Baba , Hiroshi Yokoyama , Tetsuro Shoji , Akira Miki , Akiyoshi Iida

While two-dimensional (2D) reed oscillation modes of single-reed woodwind instruments have been reported in previous studies, little is known about their effects on airflow and sound generation. In this study, we conducted aeroacoustic simulations of a clarinet mouthpiece and resonator coupled with one-dimensional (1D) and 2D reed deformation models and investigated the changes in flow and sound generation due to the 2D reed vibration. The 1D and 2D reeds were modeled using 1D beam and thin plate theories, respectively, whereas the three-dimensional airflow was simulated by solving the compressible Navier–Stokes equations. The self-sustained oscillations of the 2D reed model mainly exhibited a flexural mode at the fundamental frequency, which is consistent with previous observations. Complex torsional modes were observed only at higher harmonic frequencies. A comparison between the 1D and 2D reed models demonstrated that the 2D reed opened later at the side face of the mouthpiece than the 1D reed owing to the torsional mode, which changed the time variation of the flow rate into the mouthpiece and the far-field sound in the high-frequency range. These results suggest the importance of the torsional deformation characteristics of reeds on the timbre of single-reed instruments.

尽管之前的研究已经报道了单簧木管乐器的二维（2D）哨片振荡模式，但对其对气流和发声的影响却知之甚少。在这项研究中，我们对单簧管吹嘴和共鸣器进行了气动声学模拟，并结合一维（1D）和二维簧片变形模型，研究了二维簧片振动对气流和声音产生的影响。一维和二维簧片分别使用一维梁和薄板理论建模，而三维气流则通过求解可压缩纳维-斯托克斯方程进行模拟。二维苇片模型的自持振荡主要表现为基频处的挠曲模式，这与之前的观察结果一致。只有在较高的谐波频率下才能观察到复杂的扭转模式。一维和二维哨片模型之间的比较表明，二维哨片在吹嘴侧面的打开时间晚于一维哨片，原因是扭转模式改变了吹嘴流量的时间变化和高频范围内的远场声。这些结果表明，哨片的扭转变形特性对单簧乐器的音色具有重要影响。

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引用次数: 0

Momentum exchange method for quantum Boltzmann methods 量子波尔兹曼方法的动量交换法

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

Computers & Fluids

Pub Date : 2024-10-16 DOI: 10.1016/j.compfluid.2024.106453

Merel A. Schalkers, Matthias Möller

The past years have seen a surge in quantum algorithms for computational fluid dynamics (CFD). These algorithms have in common that whilst promising a speed-up in the performance of the algorithm, no specific method of measurement has been suggested. This means that while the algorithms presented in the literature may be promising methods for creating the quantum state that represents the final flow field, an efficient measurement strategy is not available. This paper marks the first quantum method proposed to efficiently calculate quantities of interest (QoIs) from a state vector representing the flow field. In particular, we propose a method to calculate the force acting on an object immersed in the fluid using a quantum version of the momentum exchange method (MEM) that is commonly used in lattice Boltzmann methods to determine the drag and lift coefficients. In order to achieve this we furthermore give a scheme that implements bounce back boundary conditions on a quantum computer, as those are the boundary conditions the momentum exchange method is designed for.

过去几年中，计算流体动力学（CFD）的量子算法激增。这些算法的共同点是，虽然有望加快算法性能，但没有提出具体的测量方法。这意味着，虽然文献中介绍的算法可能是创建代表最终流场的量子态的有前途的方法，但却没有有效的测量策略。本文首次提出了一种量子方法，可从代表流场的状态矢量中有效计算出感兴趣的量子量（QoIs）。特别是，我们提出了一种使用量子版动量交换法（MEM）计算浸入流体中物体所受作用力的方法，该方法常用于确定阻力和升力系数的晶格玻尔兹曼方法。为了实现这一目标，我们进一步给出了一种在量子计算机上实现反弹边界条件的方案，因为这些正是动量交换法设计的边界条件。

引用次数: 0

A numerical method for simulating variable density flows in membrane desalination systems 模拟膜脱盐系统中变密度流动的数值方法

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

Computers & Fluids

Pub Date : 2024-10-11 DOI: 10.1016/j.compfluid.2024.106449

Federico Municchi , Yiming Liu , Jingbo Wang , Tzahi Y. Cath , Craig S. Turchi , Michael B. Heeley , Eric M.V. Hoek , David Jassby , Nils Tilton

We present a novel method for simulating unsteady, variable density, fluid flows in membrane desalination systems. By assuming the density varies only with concentration and temperature, the scheme decouples the solution of the governing equations into two sequential blocks. The first solves the governing equations for the temperature and concentration fields, which are used to compute all thermophysical properties. The second block solves the conservation of mass and momentum equations for the velocity and pressure. We show that this is computationally more efficient than schemes that iterate over the full coupled equations in one block. We verify that the method achieves second-order spatial–temporal accuracy, and we use the method to investigate buoyancy-driven convection in a desalination process called vacuum membrane distillation. Specifically, we show that with gravity properly oriented, variations in temperature and concentration can trigger a double-diffusive instability that enhances mixing and improves water recovery. We also show that the instability can be strengthened by providing external heating.

我们提出了一种新方法，用于模拟膜脱盐系统中的非稳态、变密度流体流动。通过假设密度仅随浓度和温度变化，该方案将调节方程的求解分解为两个连续的模块。第一块求解温度场和浓度场的控制方程，用于计算所有热物理特性。第二个区块求解速度和压力的质量和动量守恒方程。我们证明，与在一个区块中遍历全部耦合方程的方案相比，这种方法的计算效率更高。我们验证了该方法达到了二阶时空精度，并使用该方法研究了真空膜蒸馏海水淡化过程中的浮力驱动对流。具体来说，我们表明，在重力方向正确的情况下，温度和浓度的变化会引发双扩散不稳定性，从而加强混合并提高水回收率。我们还表明，通过提供外部加热可以加强这种不稳定性。

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引用次数: 0

Error assessment of reconstructed 3D Digital Replica Models: From Computed Tomography data to pore-scale simulations 重建三维数字副本模型的误差评估：从计算机断层扫描数据到孔隙尺度模拟

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

Computers & Fluids

Pub Date : 2024-10-11 DOI: 10.1016/j.compfluid.2024.106450

Abdelkader Hammouti , Fatna Oukaili , Damien Pham Van Bang

The application of flow simulations on porous media, reconstructed through Computerized Tomography (CT) scans, has emerged as a prevalent methodology for the computation of rock permeability. However, constructing a proper 3D model of a rock sample is a real challenge, mainly due to the lack of a unified procedure. Indeed, to ensure precise outcomes, specific prerequisites must be fulfilled. This paper proposes a methodology to assess the convergence and accuracy of computed solutions from CT data to pore-scale simulations. Starting from 3D volume data obtained by X-ray CT, we develop a workflow to investigate the effects of the reconstructed shape on the permeability of a granular porous medium composed of glass beads. Indeed, the choices of CT scan resolution and digital rock discretization can compromise the quality and computational cost of numerical results. Especially in configurations of porous media with high solid volume fractions and very narrow porous spaces, as observed in solid/solid contact zones, which can be either under or over-resolved depending on the numerical tools used. Highly resolved Direct Numerical Simulations (DNS) are conducted to solve incompressible Navier–Stokes equations through porous media. Body-fitted meshes are employed to resolve irregular shapes accurately, ensuring precise results even with coarser meshes. The methodology is validated with challenging simulations of flows through simple cubic close packing of particles, incorporating various geometric surface modeling techniques. A convergence of the results with respect to grid resolution is obtained for low- to moderate-Reynolds-number flows. The numerical results indicate that permeability calculation strongly depends on surface processing. Finally, we apply these recommendations to construct accurate digital replica models generated from CT data of our assembly of randomly arranged glass beads in a tube. The study of the pressure drop convergence demonstrates an excellent agreement with the empirical correlation.

通过计算机断层扫描（CT）重建多孔介质的流动模拟，已成为计算岩石渗透性的常用方法。然而，主要由于缺乏统一的程序，为岩石样本构建合适的三维模型确实是一项挑战。事实上，要确保精确的结果，必须满足特定的先决条件。本文提出了一种方法，用于评估从 CT 数据到孔隙尺度模拟的计算解决方案的收敛性和准确性。从 X 射线 CT 获得的三维体积数据出发，我们开发了一套工作流程，用于研究重建形状对由玻璃珠组成的颗粒多孔介质渗透性的影响。事实上，CT 扫描分辨率和数字岩石离散度的选择会影响数值结果的质量和计算成本。特别是在多孔介质的配置中，固体体积分数高，多孔空间非常狭窄，如在固体/固体接触区观察到的情况，根据所使用的数值工具，可能会出现分辨率不足或分辨率过高的情况。高分辨率直接数值模拟（DNS）用于求解通过多孔介质的不可压缩纳维-斯托克斯方程。采用体拟合网格来精确解析不规则形状，确保即使使用较粗网格也能获得精确结果。该方法结合各种几何表面建模技术，对通过简单立方紧密堆积颗粒的流动进行了高难度模拟验证。对于低到中等雷诺数的流动，结果与网格分辨率趋同。数值结果表明，渗透率计算在很大程度上取决于表面处理。最后，我们将这些建议应用于构建精确的数字复制模型，该模型是由管中随机排列的玻璃珠组件的 CT 数据生成的。对压降收敛性的研究表明，该模型与经验相关性非常吻合。

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引用次数: 0

Formulation of hybrid nodal solver based on directional effect of wave propagation in a cell-centered Lagrangian scheme 基于以单元为中心的拉格朗日方案中波传播的方向性效应的混合节点求解器的计算公式

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

Computers & Fluids

Pub Date : 2024-10-10 DOI: 10.1016/j.compfluid.2024.106451

Chunyuan Xu, Zhijun Shen, Qinghong Zeng

In this work, a hybrid nodal solver is constructed to incorporate the directional effect of wave propagation in a cell-centered Lagrangian scheme. First, the direction of wave is determined via an assumption based on the Rankine–Hugoniot condition. Next, two different approximation methods are used to calculate the velocity jump and numerical fluxes. Correspondingly, a hybridization strategy is proposed to formulate a hybrid nodal solver. It is shown that the developed nodal solver can replicate two well-known ones, and its effectiveness is shown in numerical experiments. Finally, an adaptive hybridization method based on vorticity is proposed. The accuracy and robustness of the adaptive method is assessed in various tests.

本研究构建了一种混合节点求解器，将波传播的方向效应纳入以单元为中心的拉格朗日方案中。首先，通过基于 Rankine-Hugoniot 条件的假设确定波的方向。然后，使用两种不同的近似方法计算速度跃迁和数值通量。相应地，提出了一种混合策略来制定混合节点求解器。结果表明，所开发的节点求解器可以复制两种著名的求解器，并在数值实验中证明了其有效性。最后，提出了一种基于涡度的自适应混合方法。在各种测试中评估了自适应方法的准确性和稳健性。

引用次数: 0