Computers & Fluids最新文献_第8页

Characterizing drop morphology evolution in aerodynamic breakup with topological skeleton 用拓扑骨架表征气动破碎过程中液滴形态演化

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

Computers & Fluids

Pub Date : 2025-11-02 DOI: 10.1016/j.compfluid.2025.106894

S.G. Garcia, Y. Ling

In the atomization and spray formation process, liquid structures undergo transient and complex deformation, making it challenging to characterize their morphological evolution. In the present study, a novel skeletonization method is presented to extract the topological skeleton for 2D and 3D liquid structures resolved by the Volume-of-Fluid (VOF) method. The maximally inscribed balls (MIB) within the reconstructed VOF surface are identified, and their resulting centers and radii consist of the topological skeleton. Due to numerical errors inherent in VOF-represented surfaces, erroneous skeleton points may arise. A filtering method is proposed to remove these skeleton points based on geometric properties. The skeletonization method is first tested using synthetic drop shapes composed of a superposition of spherical harmonic modes with different amplitudes. The number of skeleton branches is related to the mode number. The method is then applied to characterize the shape evolution of a drop in aerodynamic breakup. Both 2D axisymmetric and full 3D simulations are performed. The obtained curve and surface skeletons are useful for analyzing the morphological evolution of the drop and, more importantly, the sheet thickness distribution in the complex liquid bag.

在雾化和喷雾形成过程中，液体结构经历了短暂而复杂的变形，这给表征其形态演变带来了挑战。本研究提出了一种新的骨架化方法，用于提取由流体体积（VOF）方法解析的二维和三维液体结构的拓扑骨架。在重构的VOF表面内识别出最大内切球（MIB），它们的中心和半径构成拓扑骨架。由于vof表示的曲面固有的数值误差，可能会出现错误的骨架点。提出了一种基于几何属性的滤波方法来去除这些骨架点。首先对骨架化方法进行了测试，使用由不同振幅的球谐模叠加组成的合成水滴形状。骨架分支的数量与模式号有关。然后将该方法应用于液滴在气动破碎过程中的形状演化特征。进行了二维轴对称和全三维模拟。所得的曲线和表面骨架有助于分析液滴的形态演变，更重要的是分析复杂液袋中的片厚分布。

{"title":"Characterizing drop morphology evolution in aerodynamic breakup with topological skeleton","authors":"S.G. Garcia, Y. Ling","doi":"10.1016/j.compfluid.2025.106894","DOIUrl":"10.1016/j.compfluid.2025.106894","url":null,"abstract":"<div><div>In the atomization and spray formation process, liquid structures undergo transient and complex deformation, making it challenging to characterize their morphological evolution. In the present study, a novel skeletonization method is presented to extract the topological skeleton for 2D and 3D liquid structures resolved by the Volume-of-Fluid (VOF) method. The maximally inscribed balls (MIB) within the reconstructed VOF surface are identified, and their resulting centers and radii consist of the topological skeleton. Due to numerical errors inherent in VOF-represented surfaces, erroneous skeleton points may arise. A filtering method is proposed to remove these skeleton points based on geometric properties. The skeletonization method is first tested using synthetic drop shapes composed of a superposition of spherical harmonic modes with different amplitudes. The number of skeleton branches is related to the mode number. The method is then applied to characterize the shape evolution of a drop in aerodynamic breakup. Both 2D axisymmetric and full 3D simulations are performed. The obtained curve and surface skeletons are useful for analyzing the morphological evolution of the drop and, more importantly, the sheet thickness distribution in the complex liquid bag.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106894"},"PeriodicalIF":3.0,"publicationDate":"2025-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145517554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Direct Poisson solver combining domain decomposition and influence matrix methods and its application to DNS of oscillating grid turbulence 结合域分解和影响矩阵法的直接泊松求解方法及其在振荡网格湍流DNS中的应用

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

Computers & Fluids

Pub Date : 2025-10-31 DOI: 10.1016/j.compfluid.2025.106891

Toru Yamada , Ryuga Sumi , Yohei Morinishi

This study presents the application of a direct Poisson solver combining domain decomposition and influence matrix methods to the direct numerical simulation (DNS) of oscillating grid turbulence (OGT). Solving the pressure Poisson equation is one of the major challenges in computational fluid dynamics. Traditional direct methods are accurate but difficult to be applied to large-scale problems, while iterative methods can suffer from slow convergence. The hybrid approach enables the use of the direct methods for the problem with complex computational geometry. The results show that this direct solver significantly reduces computation time compared to the iterative BiCGSTAB method. The DNS results are validated by comparison of experimental data, demonstrating good agreement in the vertical distribution of velocity fluctuation intensity. Therefore, the efficiency of this direct method for simulating the OGT turbulent flows is confirmed.

本文提出了结合域分解和影响矩阵法的直接泊松求解方法在振荡网格湍流直接数值模拟中的应用。求解压力泊松方程是计算流体力学的主要挑战之一。传统的直接法精度高，但难以应用于大规模问题，迭代法收敛速度慢。这种混合方法使直接求解复杂计算几何问题成为可能。结果表明，与迭代的BiCGSTAB方法相比，该直接求解器显著减少了计算时间。通过与实验数据的对比，验证了DNS计算结果的正确性，表明速度波动强度的垂直分布具有较好的一致性。从而验证了该直接方法模拟OGT湍流的有效性。

引用次数: 0

High order global flux schemes for general steady state preservation of shallow water moment equations with non-conservative products 具有非保守积的浅水力矩方程一般稳态保持的高阶全局通量格式

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

Computers & Fluids

Pub Date : 2025-10-30 DOI: 10.1016/j.compfluid.2025.106887

Mirco Ciallella , Julian Koellermeier

Shallow water moment equations are reduced-order models for free-surface flows that allow to represent vertical variations of the velocity profile at the expense of additional evolution equations for a number of additional variables, so called moments. This introduces non-linear non-conservative products in the system, which make the analytical characterization of steady states much harder if not impossible. The lack of analytical steady states poses a challenge for the design of well-balanced schemes, which aim at preserving such steady states as crucial in many applications.

In this work, we present a family of fully approximately well-balanced, high-order WENO finite volume methods for general hyperbolic balance laws with non-conservative products like the shallow water moment equations, for which no analytical steady states are available. The schemes are based on the flux globalization approach, in which both source terms and non-conservative products are integrated with a tailored high order quadrature in the divergence term. The resulting global flux is then reconstructed instead of the conservative variables to preserve all steady states. Numerical tests show the optimal convergence of the method and a significant error reduction for steady state solutions. Furthermore, we provide a numerical comparison of perturbed steady states for different families of shallow water moment equations, which illustrates the flexibility of our method that is valid for general equations without prior knowledge of steady states.

浅水力矩方程是自由水面流动的降阶模型，它可以表示速度剖面的垂直变化，但要牺牲一些附加变量的附加演化方程，即所谓的力矩。这在系统中引入了非线性非保守积，这使得稳态的分析表征更加困难，如果不是不可能的话。分析稳态的缺乏对平衡方案的设计提出了挑战，平衡方案旨在保持在许多应用中至关重要的稳定状态。在这项工作中，我们提出了一组完全近似良好平衡的高阶WENO有限体积方法，用于一般双曲平衡律的非保守乘积，如浅水力矩方程，其中没有可用的解析稳态。该方案基于通量全球化方法，其中源项和非保守积都与散度项中的定制高阶正交相结合。然后重建得到的全局通量，而不是保守变量，以保持所有稳态。数值试验表明，该方法具有最优的收敛性，并显著减小了稳态解的误差。此外，我们提供了不同类型的浅水力矩方程的扰动稳态的数值比较，这说明了我们的方法的灵活性，适用于没有稳态先验知识的一般方程。

{"title":"High order global flux schemes for general steady state preservation of shallow water moment equations with non-conservative products","authors":"Mirco Ciallella , Julian Koellermeier","doi":"10.1016/j.compfluid.2025.106887","DOIUrl":"10.1016/j.compfluid.2025.106887","url":null,"abstract":"<div><div>Shallow water moment equations are reduced-order models for free-surface flows that allow to represent vertical variations of the velocity profile at the expense of additional evolution equations for a number of additional variables, so called moments. This introduces non-linear non-conservative products in the system, which make the analytical characterization of steady states much harder if not impossible. The lack of analytical steady states poses a challenge for the design of well-balanced schemes, which aim at preserving such steady states as crucial in many applications.</div><div>In this work, we present a family of fully approximately well-balanced, high-order WENO finite volume methods for general hyperbolic balance laws with non-conservative products like the shallow water moment equations, for which no analytical steady states are available. The schemes are based on the flux globalization approach, in which both source terms and non-conservative products are integrated with a tailored high order quadrature in the divergence term. The resulting global flux is then reconstructed instead of the conservative variables to preserve all steady states. Numerical tests show the optimal convergence of the method and a significant error reduction for steady state solutions. Furthermore, we provide a numerical comparison of perturbed steady states for different families of shallow water moment equations, which illustrates the flexibility of our method that is valid for general equations without prior knowledge of steady states.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"305 ","pages":"Article 106887"},"PeriodicalIF":3.0,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A semi-implicit, second-order time-integration scheme for surface tension modeling in two-dimensional capillary-dominated two-phase flows 二维毛细管主导两相流表面张力建模的半隐式二阶时间积分格式

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

Computers & Fluids

Pub Date : 2025-10-26 DOI: 10.1016/j.compfluid.2025.106889

Adil Fahsi , Azzeddine Soulaïmani

We present a second-order semi-implicit time integration scheme for modeling surface tension in capillary-dominated two-phase flows, implemented within a two-dimensional XFEM/level set framework. Traditional explicit methods are constrained by the capillary time-step, requiring prohibitively small increments and leading to long simulations and error accumulation. Semi-implicit strategies relax this limitation by introducing a Laplace-Beltrami operator that acts as a numerical interface viscosity, damping high-frequency interfacial modes and thereby improving stability. While this stabilizing dissipation enables larger time-steps and suppresses spurious currents, it also introduces artificial damping that may distort interfacial dynamics. Our proposed BDF2 formulation reduces this dissipation by a factor of two-thirds compared with the classical first-order variant, thus enhancing fidelity without sacrificing stability. The method is validated on three two-dimensional benchmarks: a static bubble, a rising bubble, and an oscillating bubble demonstrating robust convergence to theoretical and reference solutions. Results confirm that the second-order semi-implicit scheme achieves genuine second-order temporal accuracy with improved efficiency, making it suitable for high-fidelity simulations of capillary-driven two-phase flows.

我们提出了一种二阶半隐式时间积分方案，用于模拟毛细管主导的两相流中的表面张力，该方案在二维XFEM/水平集框架内实现。传统的显式方法受到毛细管时间步长的限制，需要非常小的增量，导致长时间的模拟和误差积累。半隐式策略通过引入Laplace-Beltrami算子来缓解这一限制，该算子作为数值界面粘度，抑制高频界面模式，从而提高稳定性。虽然这种稳定耗散可以实现更大的时间步长并抑制伪电流，但它也引入了可能扭曲界面动力学的人为阻尼。我们提出的BDF2公式与经典的一阶变体相比，将这种耗散减少了三分之二，从而在不牺牲稳定性的情况下提高了保真度。该方法在三个二维基准上进行了验证：静态气泡，上升气泡和振荡气泡，证明了理论和参考解决方案的鲁棒收敛性。结果表明，二阶半隐式格式在提高效率的同时获得了真正的二阶时间精度，适用于毛细管驱动两相流的高保真模拟。

{"title":"A semi-implicit, second-order time-integration scheme for surface tension modeling in two-dimensional capillary-dominated two-phase flows","authors":"Adil Fahsi , Azzeddine Soulaïmani","doi":"10.1016/j.compfluid.2025.106889","DOIUrl":"10.1016/j.compfluid.2025.106889","url":null,"abstract":"<div><div>We present a second-order semi-implicit time integration scheme for modeling surface tension in capillary-dominated two-phase flows, implemented within a two-dimensional XFEM/level set framework. Traditional explicit methods are constrained by the capillary time-step, requiring prohibitively small increments and leading to long simulations and error accumulation. Semi-implicit strategies relax this limitation by introducing a Laplace-Beltrami operator that acts as a numerical interface viscosity, damping high-frequency interfacial modes and thereby improving stability. While this stabilizing dissipation enables larger time-steps and suppresses spurious currents, it also introduces artificial damping that may distort interfacial dynamics. Our proposed BDF2 formulation reduces this dissipation by a factor of two-thirds compared with the classical first-order variant, thus enhancing fidelity without sacrificing stability. The method is validated on three two-dimensional benchmarks: a static bubble, a rising bubble, and an oscillating bubble demonstrating robust convergence to theoretical and reference solutions. Results confirm that the second-order semi-implicit scheme achieves genuine second-order temporal accuracy with improved efficiency, making it suitable for high-fidelity simulations of capillary-driven two-phase flows.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106889"},"PeriodicalIF":3.0,"publicationDate":"2025-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Calibration of Manning’s roughness coefficients for shallow-water flows on complex bathymetries using optimization algorithms and surrogate neural network models 使用优化算法和代理神经网络模型校准复杂水深下浅水流的曼宁粗糙度系数

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

Computers & Fluids

Pub Date : 2025-10-25 DOI: 10.1016/j.compfluid.2025.106884

Igor Gildas Metcheka Kengne , Vincent Delmas , Azzeddine Soulaïmani

This paper presents an effective methodology for the automatic calibration of Manning’s roughness coefficients, which are crucial parameters for modeling shallow free-surface flows. Traditionally determined through empirical methods, these coefficients are subject to significant variability, making their determination challenging, especially in flow areas with complex bathymetry. The conventional trial-and-error approach, widely used to select these coefficients, is often tedious and time-consuming, particularly in applications constrained by time and data availability. The proposed methodology aims to determine the optimal values of Manning’s coefficients distributed over the flow domain while minimizing global discrepancies between simulations and field measurements. The calibration approach is formulated as an inverse optimization problem and addressed using metaheuristic optimization algorithms such as the Genetic Algorithm or Particle Swarm Optimization, combined with an ensemble model of deep neural networks. The database for training the neural networks is obtained using a newly developed finite volume-based shallow-water equations solver, parallelized on multiple GPUs, to generate large datasets of solutions for machine learning purposes. The performance of this approach is evaluated through various flow scenarios. Compared to conventional techniques, this methodology stands out for its simplicity, computational efficiency, and robustness. Additionally, Hybrid Particle Swarm Optimization (HPSO) proves to be particularly effective, notably for its speed. The developed codes are available at: https://github.com/ETS-GRANIT/CuteFlow.

本文提出了一种自动标定曼宁粗糙度系数的有效方法。曼宁粗糙度系数是模拟浅层自由流的关键参数。传统上，这些系数是通过经验方法确定的，这些系数受到显著变化的影响，使得它们的确定具有挑战性，特别是在具有复杂水深测量的流动区域。传统的试错法被广泛用于选择这些系数，但这种方法通常既繁琐又耗时，特别是在受时间和数据可用性限制的应用程序中。提出的方法旨在确定曼宁系数分布在流域上的最佳值，同时最小化模拟和现场测量之间的全局差异。校准方法被制定为一个逆优化问题，并使用元启发式优化算法，如遗传算法或粒子群优化，结合深度神经网络的集成模型来解决。训练神经网络的数据库使用新开发的基于有限体积的浅水方程求解器获得，在多个gpu上并行化，以生成用于机器学习目的的解决方案的大型数据集。通过各种流场景对该方法的性能进行了评估。与传统技术相比，该方法以其简单性、计算效率和鲁棒性而突出。此外，混合粒子群优化（HPSO）被证明是特别有效的，特别是它的速度。开发的代码可在https://github.com/ETS-GRANIT/CuteFlow上获得。

{"title":"Calibration of Manning’s roughness coefficients for shallow-water flows on complex bathymetries using optimization algorithms and surrogate neural network models","authors":"Igor Gildas Metcheka Kengne , Vincent Delmas , Azzeddine Soulaïmani","doi":"10.1016/j.compfluid.2025.106884","DOIUrl":"10.1016/j.compfluid.2025.106884","url":null,"abstract":"<div><div>This paper presents an effective methodology for the automatic calibration of Manning’s roughness coefficients, which are crucial parameters for modeling shallow free-surface flows. Traditionally determined through empirical methods, these coefficients are subject to significant variability, making their determination challenging, especially in flow areas with complex bathymetry. The conventional trial-and-error approach, widely used to select these coefficients, is often tedious and time-consuming, particularly in applications constrained by time and data availability. The proposed methodology aims to determine the optimal values of Manning’s coefficients distributed over the flow domain while minimizing global discrepancies between simulations and field measurements. The calibration approach is formulated as an inverse optimization problem and addressed using metaheuristic optimization algorithms such as the Genetic Algorithm or Particle Swarm Optimization, combined with an ensemble model of deep neural networks. The database for training the neural networks is obtained using a newly developed finite volume-based shallow-water equations solver, parallelized on multiple GPUs, to generate large datasets of solutions for machine learning purposes. The performance of this approach is evaluated through various flow scenarios. Compared to conventional techniques, this methodology stands out for its simplicity, computational efficiency, and robustness. Additionally, Hybrid Particle Swarm Optimization (HPSO) proves to be particularly effective, notably for its speed. The developed codes are available at: <span><span>https://github.com/ETS-GRANIT/CuteFlow</span><svg><path></path></svg></span>.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106884"},"PeriodicalIF":3.0,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Lax–Wendroff theorem for Patankar-type methods applied to hyperbolic conservation laws 帕坦卡型方法的Lax-Wendroff定理在双曲守恒律中的应用

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

Computers & Fluids

Pub Date : 2025-10-25 DOI: 10.1016/j.compfluid.2025.106885

Janina Bender , Thomas Izgin , Philipp Öffner , Davide Torlo

For hyperbolic conservation laws, the famous Lax–Wendroff theorem delivers sufficient conditions for the limit of a convergent numerical method to be a weak (entropy) solution. This theorem is a fundamental result, and many investigations have been done to verify its validity for finite difference, finite volume, and finite element schemes, using either explicit or implicit linear time-integration methods.

Recently, the use of modified Patankar (MP) schemes as time-integration methods for the discretization of hyperbolic conservation laws has gained increasing interest. These schemes are unconditionally conservative and positivity-preserving and only require the solution of a linear system. However, MP schemes are by construction nonlinear, which is why the theoretical investigation of these schemes is more involved. We prove an extension of the Lax–Wendroff theorem for the class of MP methods. This is the first extension of the Lax–Wendroff theorem to nonlinear time integration methods with just an additional hypothesis on the total time variation boundedness of the numerical solutions. We provide some numerical simulations that validate the theoretical observations.

对于双曲守恒定律，著名的Lax-Wendroff定理给出了收敛数值方法极限为弱（熵）解的充分条件。这个定理是一个基本结果，许多研究已经完成，以验证其有效性有限差分，有限体积，和有限元方案，使用显式或隐式线性时间积分方法。近年来，利用改进的Patankar （MP）格式作为双曲守恒律离散化的时间积分方法得到了越来越多的关注。这些格式是无条件保守的、保正的，并且只要求线性系统的解。然而，mps格式在结构上是非线性的，这就是为什么这些格式的理论研究更加复杂的原因。我们证明了一类MP方法的Lax-Wendroff定理的推广。这是第一次将Lax-Wendroff定理推广到非线性时间积分方法中，只增加了一个关于数值解的总时变有界性的假设。我们提供了一些数值模拟来验证理论观测。

{"title":"The Lax–Wendroff theorem for Patankar-type methods applied to hyperbolic conservation laws","authors":"Janina Bender , Thomas Izgin , Philipp Öffner , Davide Torlo","doi":"10.1016/j.compfluid.2025.106885","DOIUrl":"10.1016/j.compfluid.2025.106885","url":null,"abstract":"<div><div>For hyperbolic conservation laws, the famous Lax–Wendroff theorem delivers sufficient conditions for the limit of a convergent numerical method to be a weak (entropy) solution. This theorem is a fundamental result, and many investigations have been done to verify its validity for finite difference, finite volume, and finite element schemes, using either explicit or implicit linear time-integration methods.</div><div>Recently, the use of modified Patankar (MP) schemes as time-integration methods for the discretization of hyperbolic conservation laws has gained increasing interest. These schemes are unconditionally conservative and positivity-preserving and only require the solution of a linear system. However, MP schemes are by construction nonlinear, which is why the theoretical investigation of these schemes is more involved. We prove an extension of the Lax–Wendroff theorem for the class of MP methods. This is the first extension of the Lax–Wendroff theorem to nonlinear time integration methods with just an additional hypothesis on the total time variation boundedness of the numerical solutions. We provide some numerical simulations that validate the theoretical observations.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106885"},"PeriodicalIF":3.0,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Fast integration method for averaging polydisperse bubble population dynamics 多分散气泡种群动态平均的快速积分方法

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

Computers & Fluids

Pub Date : 2025-10-24 DOI: 10.1016/j.compfluid.2025.106877

Spencer H. Bryngelson

Ensemble-averaged polydisperse bubbly flow models require statistical moments of the evolving bubble size distribution. Under step forcing, these moments reach statistical equilibrium in finite time. However, the transitional phase before equilibrium and cases with time-dependent forcing are required to predict flow in engineering applications. Computing these moments is expensive because the integrands are highly oscillatory, even when the bubble dynamics are linear. Ensemble-averaged models compute these moments at each grid point and time step, making cost reduction important for large-scale bubbly flow simulations. Traditional methods evaluate the integrals via traditional quadrature rules. This approach requires a large number of quadrature nodes in the equilibrium bubble size, each equipped with its own advection partial differential equation (PDE), resulting in significant computational expense. We formulate a Levin collocation method to reduce this cost. Given the differential equation associated with the integrand, or moment, the method approximates it by evaluating its derivative via polynomial collocation. The differential matrix and amplitude function are well-suited to numerical differentiation via collocation, and so the computation is comparatively cheap. For an example excited polydisperse bubble population, the first moment is computed with the presented method at

10^{- 3}

relative error with 100 times fewer quadrature nodes than the trapezoidal rule. The gap increases for smaller target relative errors: the Levin method requires

10^{4}

times fewer points for a relative error of

10^{- 8}

. The formulated method maintains constant cost as the integrands become more oscillatory with time, making it particularly attractive for long-time simulations. Mechanistically, the transient behavior of the moments is set by two effects: resonance detuning across bubble sizes, which causes phase mixing of oscillations, and viscous damping, which removes radial kinetic energy. The proposed formulation isolates the oscillations while keeping the remaining terms smooth, so accuracy does not deteriorate at late times.

集合平均多分散气泡流模型需要气泡尺寸分布演化的统计矩。在阶跃强迫下，这些力矩在有限时间内达到统计平衡。然而，在工程应用中，需要平衡前的过渡阶段和具有时间依赖力的情况来预测流动。计算这些矩是昂贵的，因为积分是高度振荡的，即使当气泡动力学是线性的。集合平均模型在每个网格点和时间步计算这些矩，这对于大规模气泡流模拟来说降低成本很重要。传统的方法是通过传统的求积分规则来求积分。这种方法需要大量的平衡气泡大小的正交节点，每个节点都有自己的平流偏微分方程（PDE），导致大量的计算费用。为了降低这一成本，我们提出了Levin配置法。给定与被积函数或矩相关的微分方程，该方法通过多项式搭配评估其导数来逼近它。微分矩阵和振幅函数都适合于配点法的数值微分，因此计算量相对较少。对于一个受激多分散气泡群的例子，用该方法计算了第一矩，相对误差为10−3，其正交节点比梯形规则少100倍。目标相对误差越小，差距越大：Levin方法在相对误差为10−8时需要的点数减少104倍。当被积函数随着时间的推移变得更加振荡时，该方法保持恒定的代价，使其对长时间模拟特别有吸引力。从力学上讲，力矩的瞬态行为是由两种效应决定的：共振失谐，这导致了振荡的相位混合；粘滞阻尼，这消除了径向动能。提出的公式隔离振荡，同时保持其余项平滑，因此精度不会在后期恶化。

{"title":"Fast integration method for averaging polydisperse bubble population dynamics","authors":"Spencer H. Bryngelson","doi":"10.1016/j.compfluid.2025.106877","DOIUrl":"10.1016/j.compfluid.2025.106877","url":null,"abstract":"<div><div>Ensemble-averaged polydisperse bubbly flow models require statistical moments of the evolving bubble size distribution. Under step forcing, these moments reach statistical equilibrium in finite time. However, the transitional phase before equilibrium and cases with time-dependent forcing are required to predict flow in engineering applications. Computing these moments is expensive because the integrands are highly oscillatory, even when the bubble dynamics are linear. Ensemble-averaged models compute these moments at each grid point and time step, making cost reduction important for large-scale bubbly flow simulations. Traditional methods evaluate the integrals via traditional quadrature rules. This approach requires a large number of quadrature nodes in the equilibrium bubble size, each equipped with its own advection partial differential equation (PDE), resulting in significant computational expense. We formulate a Levin collocation method to reduce this cost. Given the differential equation associated with the integrand, or moment, the method approximates it by evaluating its derivative via polynomial collocation. The differential matrix and amplitude function are well-suited to numerical differentiation via collocation, and so the computation is comparatively cheap. For an example excited polydisperse bubble population, the first moment is computed with the presented method at <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math></span> relative error with 100 times fewer quadrature nodes than the trapezoidal rule. The gap increases for smaller target relative errors: the Levin method requires <span><math><msup><mn>10</mn><mn>4</mn></msup></math></span> times fewer points for a relative error of <span><math><msup><mn>10</mn><mrow><mo>−</mo><mn>8</mn></mrow></msup></math></span>. The formulated method maintains constant cost as the integrands become more oscillatory with time, making it particularly attractive for long-time simulations. Mechanistically, the transient behavior of the moments is set by two effects: resonance detuning across bubble sizes, which causes phase mixing of oscillations, and viscous damping, which removes radial kinetic energy. The proposed formulation isolates the oscillations while keeping the remaining terms smooth, so accuracy does not deteriorate at late times.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106877"},"PeriodicalIF":3.0,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Aircraft wake vortex encounters with residential structures 飞机尾流涡与住宅结构的碰撞

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

Computers & Fluids

Pub Date : 2025-10-24 DOI: 10.1016/j.compfluid.2025.106883

S. Bennie , M. Fossati

Presented in the following work is a comprehensive analysis of wake vortex encounters with residential structures. From the results of high fidelity LES simulations, the dynamics and underlying flow structures which govern these potentially damaging encounters have been identified. Through evaluation of the pressure loads transmitted to the roof surface, the potential for damage to occur to a residential structure as a result of wake vortex exposure has been evaluated for a variety of cases. Regarding the building’s design, structures possessing larger pitch angles and thus steeper roofs have been found to sustain the largest peak loads for their encounter with an identical wake vortex system as compared to their flatter roofed counterparts. Similarly, upon assessing the effect of the environmental conditions it was observed that for increasingly turbulent atmospheres, the wake vortex encounter would occur sooner and with a reduced intensity compared to more neutral conditions. These behaviours have been attributed to the effects of secondary flow structures formed from the shedding of vorticity from the building surface or from wake vortex interactions with the eddies that comprise the atmospheric environment. These secondary flow structures energise wake vortex instability mechanisms thus leading to the variations in pressure loads sustained by the roof. With respect to the impact orientation, we note that there exists a minimal difference on the pressure loads generated during a wake vortex encounter for small angular offsets up to

20^{\circ}

.

在接下来的工作中，将对尾流与住宅结构的接触进行全面的分析。根据高保真LES模拟的结果，已经确定了控制这些潜在破坏性碰撞的动力学和潜在流动结构。通过对传递到屋顶表面的压力载荷的评估，对各种情况下尾流暴露对住宅结构造成的潜在损害进行了评估。关于建筑的设计，与平顶结构相比，具有更大俯仰角和更陡屋顶的结构在遇到相同的尾流涡系统时能够承受最大的峰值载荷。同样，在评估环境条件的影响时，我们观察到，在日益湍流的大气中，尾流涡旋遭遇会比更中性的条件发生得更快，强度也会降低。这些行为归因于二次流结构的影响，这些二次流结构是由建筑物表面涡度的脱落或尾流涡与构成大气环境的涡流相互作用形成的。这些二次流结构激发了尾流涡不稳定机制，从而导致了顶板承受压力载荷的变化。关于撞击方向，我们注意到，在20°以下的小角偏移中，尾流遭遇时产生的压力载荷差异很小。

{"title":"Aircraft wake vortex encounters with residential structures","authors":"S. Bennie , M. Fossati","doi":"10.1016/j.compfluid.2025.106883","DOIUrl":"10.1016/j.compfluid.2025.106883","url":null,"abstract":"<div><div>Presented in the following work is a comprehensive analysis of wake vortex encounters with residential structures. From the results of high fidelity LES simulations, the dynamics and underlying flow structures which govern these potentially damaging encounters have been identified. Through evaluation of the pressure loads transmitted to the roof surface, the potential for damage to occur to a residential structure as a result of wake vortex exposure has been evaluated for a variety of cases. Regarding the building’s design, structures possessing larger pitch angles and thus steeper roofs have been found to sustain the largest peak loads for their encounter with an identical wake vortex system as compared to their flatter roofed counterparts. Similarly, upon assessing the effect of the environmental conditions it was observed that for increasingly turbulent atmospheres, the wake vortex encounter would occur sooner and with a reduced intensity compared to more neutral conditions. These behaviours have been attributed to the effects of secondary flow structures formed from the shedding of vorticity from the building surface or from wake vortex interactions with the eddies that comprise the atmospheric environment. These secondary flow structures energise wake vortex instability mechanisms thus leading to the variations in pressure loads sustained by the roof. With respect to the impact orientation, we note that there exists a minimal difference on the pressure loads generated during a wake vortex encounter for small angular offsets up to <span><math><msup><mn>20</mn><mo>∘</mo></msup></math></span>.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106883"},"PeriodicalIF":3.0,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Solving high Reynolds number flows on Cartesian cut-cell meshes using an ODE wall function with momentum balance 利用具有动量平衡的ODE壁函数求解笛卡尔切割网格上的高雷诺数流

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

Computers & Fluids

Pub Date : 2025-10-22 DOI: 10.1016/j.compfluid.2025.106882

Alex Kleb, Krzysztof J. Fidkowski, Joaquim R.R.A. Martins

Computational fluid dynamics is essential for designing aircraft, turbines, and other engineering systems. However, generating suitable computational meshes for complex geometries remains the primary bottleneck in analysis workflows, often requiring days of manual effort. Traditional boundary-conforming meshes excel at capturing near-wall physics in viscous flows but demand specialized expertise and extensive preprocessing time. Cartesian cut-cell methods provide automatic mesh generation for complex geometries in minutes, yet they struggle with high Reynolds number viscous flows where boundary layers exhibit rapid velocity changes that require prohibitively fine resolution for isotropic elements. The fundamental challenge is accurately modeling boundary layer physics on automatically generated meshes without sacrificing the computational efficiency that makes such methods attractive. In this work, we show that an ordinary differential equation (ODE) wall function incorporating pressure-momentum balance enables accurate high Reynolds number viscous flow predictions on coarse Cartesian cut-cell meshes. Our approach solves a one-dimensional boundary value problem at each wall boundary face that accounts for the transition from the viscous dominated near-wall region to the inviscid wake region, allowing forcing points to operate effectively at

y^{+} > 600

. Unlike traditional wall functions, the ODE is not limited to the logarithmic layer and maintains accuracy in strong pressure gradient environments typical of aerodynamic applications. The ODE can achieve correct skin friction predictions on meshes more than four times coarser than analytical wall functions require. The ODE wall functions are solved with a robust Newton–Krylov implementation that utilizes adaptive mesh refinement. It converges reliably across diverse flow conditions while solving hundreds of degrees of freedom in fewer than ten linear iterations. These results demonstrate that automatic high-fidelity viscous flow analysis is achievable without manual mesh generation expertise.

计算流体动力学对于设计飞机、涡轮机和其他工程系统至关重要。然而，为复杂几何图形生成合适的计算网格仍然是分析工作流程中的主要瓶颈，通常需要数天的手工工作。传统的符合边界的网格擅长于捕获粘性流动中的近壁物理，但需要专门的技术和大量的预处理时间。笛卡尔切割单元方法可以在几分钟内自动生成复杂几何形状的网格，但它们难以处理高雷诺数粘性流动，其中边界层表现出快速的速度变化，这需要对各向同性元素进行极高的分辨率。最基本的挑战是在不牺牲计算效率的情况下，在自动生成的网格上准确地建模边界层物理，这使得这些方法具有吸引力。在这项工作中，我们证明了包含压力-动量平衡的常微分方程（ODE）壁函数可以在粗笛卡尔切割网格上精确地预测高雷诺数粘性流动。我们的方法解决了每个壁面边界面上的一维边值问题，该问题解释了从粘性占主导地位的近壁面区域到无粘性尾迹区域的过渡，允许强迫点在y+>；600有效地运行。与传统的壁面函数不同，ODE不局限于对数层，在气动应用的典型强压力梯度环境中也能保持精度。ODE可以在比解析壁函数所需的网格粗四倍以上的网格上实现正确的皮肤摩擦预测。ODE壁函数用鲁棒Newton-Krylov实现求解，该实现利用自适应网格细化。它可以可靠地收敛在不同的流动条件下，同时在不到10次的线性迭代中求解数百个自由度。这些结果表明，无需手动网格生成专业知识，就可以实现自动高保真粘性流动分析。

{"title":"Solving high Reynolds number flows on Cartesian cut-cell meshes using an ODE wall function with momentum balance","authors":"Alex Kleb, Krzysztof J. Fidkowski, Joaquim R.R.A. Martins","doi":"10.1016/j.compfluid.2025.106882","DOIUrl":"10.1016/j.compfluid.2025.106882","url":null,"abstract":"<div><div>Computational fluid dynamics is essential for designing aircraft, turbines, and other engineering systems. However, generating suitable computational meshes for complex geometries remains the primary bottleneck in analysis workflows, often requiring days of manual effort. Traditional boundary-conforming meshes excel at capturing near-wall physics in viscous flows but demand specialized expertise and extensive preprocessing time. Cartesian cut-cell methods provide automatic mesh generation for complex geometries in minutes, yet they struggle with high Reynolds number viscous flows where boundary layers exhibit rapid velocity changes that require prohibitively fine resolution for isotropic elements. The fundamental challenge is accurately modeling boundary layer physics on automatically generated meshes without sacrificing the computational efficiency that makes such methods attractive. In this work, we show that an ordinary differential equation (ODE) wall function incorporating pressure-momentum balance enables accurate high Reynolds number viscous flow predictions on coarse Cartesian cut-cell meshes. Our approach solves a one-dimensional boundary value problem at each wall boundary face that accounts for the transition from the viscous dominated near-wall region to the inviscid wake region, allowing forcing points to operate effectively at <span><math><mrow><msup><mi>y</mi><mo>+</mo></msup><mo>></mo><mn>600</mn></mrow></math></span>. Unlike traditional wall functions, the ODE is not limited to the logarithmic layer and maintains accuracy in strong pressure gradient environments typical of aerodynamic applications. The ODE can achieve correct skin friction predictions on meshes more than four times coarser than analytical wall functions require. The ODE wall functions are solved with a robust Newton–Krylov implementation that utilizes adaptive mesh refinement. It converges reliably across diverse flow conditions while solving hundreds of degrees of freedom in fewer than ten linear iterations. These results demonstrate that automatic high-fidelity viscous flow analysis is achievable without manual mesh generation expertise.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106882"},"PeriodicalIF":3.0,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Extension of a spectral difference method for the diffused-interface five-equation model 扩散界面五方程模型的谱差法推广

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

Computers & Fluids

Pub Date : 2025-10-20 DOI: 10.1016/j.compfluid.2025.106880

Niccolò Tonicello , Guido Lodato , Matthias Ihme

The present work focuses on the extension of the Spectral Difference (SD) scheme to the five-equation Baer-Nunziato model for the simulation of immiscible compressible fluids. This five-equation model is augmented with the Allen-Cahn regularisation to avoid both over-diffusion and over-thinning of the phase field representing the interface. In order to preserve contact discontinuities, in the reconstruction step of the SD scheme, a change of variables from conservative to primitive is used. This approach is shown to be beneficial in avoiding pressure oscillations at material interfaces. An extensive series of numerical tests, considering both two- and three-dimensional problems, are performed to assess accuracy and robustness of the present method. Specifically, both laminar and turbulent flows, as well as low-Mach and highly compressible flows, are considered, including cases with and without surface tension. The proposed change of variables is shown to improve the stability of the scheme, significantly reducing pressure oscillations at the material interfaces. This improved robustness enables the method to achieve accurate and stable solutions across a broad range of flow conditions.

本文将谱差（SD）格式推广到五方程Baer-Nunziato模型中，用于非混相可压缩流体的模拟。该五方程模型用Allen-Cahn正则化进行了扩充，以避免代表界面的相场的过度扩散和过度稀释。为了保持接触不连续，在SD格式的重建步骤中，使用了从保守到原始的变量变化。这种方法被证明有利于避免材料界面的压力振荡。考虑到二维和三维问题，进行了一系列广泛的数值试验，以评估本方法的准确性和鲁棒性。具体来说，层流和湍流，以及低马赫和高可压缩流，包括有和没有表面张力的情况，都被考虑在内。结果表明，所提出的变量变化提高了方案的稳定性，显著减少了材料界面处的压力振荡。这种增强的鲁棒性使该方法能够在广泛的流动条件下获得准确和稳定的解决方案。

{"title":"Extension of a spectral difference method for the diffused-interface five-equation model","authors":"Niccolò Tonicello , Guido Lodato , Matthias Ihme","doi":"10.1016/j.compfluid.2025.106880","DOIUrl":"10.1016/j.compfluid.2025.106880","url":null,"abstract":"<div><div>The present work focuses on the extension of the Spectral Difference (SD) scheme to the five-equation Baer-Nunziato model for the simulation of immiscible compressible fluids. This five-equation model is augmented with the Allen-Cahn regularisation to avoid both over-diffusion and over-thinning of the phase field representing the interface. In order to preserve contact discontinuities, in the reconstruction step of the SD scheme, a change of variables from conservative to primitive is used. This approach is shown to be beneficial in avoiding pressure oscillations at material interfaces. An extensive series of numerical tests, considering both two- and three-dimensional problems, are performed to assess accuracy and robustness of the present method. Specifically, both laminar and turbulent flows, as well as low-Mach and highly compressible flows, are considered, including cases with and without surface tension. The proposed change of variables is shown to improve the stability of the scheme, significantly reducing pressure oscillations at the material interfaces. This improved robustness enables the method to achieve accurate and stable solutions across a broad range of flow conditions.</div></div>","PeriodicalId":287,"journal":{"name":"Computers & Fluids","volume":"304 ","pages":"Article 106880"},"PeriodicalIF":3.0,"publicationDate":"2025-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0