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Spectral collocation method coupled with domain decomposition for exterior problems of the Fisher equation 费舍尔方程外部问题的谱配位法与域分解相结合
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-15 DOI: 10.1016/j.camwa.2024.10.003
Jia Tan, Tian-jun Wang
The spectral collocation method coupled with domain decomposition is developed for solving the exterior problems of the Fisher's equation with polygon obstacles. Some results on the composite Laguerre-Legendre interpolation, which is a set of piecewise mixed interpolations coupled with domain decomposition, are introduced. As an important application, the composite spectral collocation scheme based on the Legendre-Gauss-Lobatto and the Laguerre-Gauss-Radau nodes is provided for the exterior problems of the Fisher's equation. The convergence of the proposed scheme is proved. Efficient algorithm is implemented. Numerical results demonstrate the high accuracy in space of the proposed method and confirm the theoretical analysis well. The approximation results and some techniques developed in this paper are also very useful for other exterior nonlinear problems with complex geometry.
为解决有多边形障碍物的费雪方程的外部问题,提出了与域分解相结合的谱配位方法。介绍了关于复合 Laguerre-Legendre 插值的一些结果,它是一组与域分解耦合的片断混合插值。作为一个重要应用,为 Fisher 方程的外部问题提供了基于 Legendre-Gauss-Lobatto 和 Laguerre-Gauss-Radau 节点的复合谱配位方案。证明了所提方案的收敛性。实现了高效算法。数值结果证明了所提方法在空间上的高精度,并很好地证实了理论分析。本文中开发的近似结果和一些技术对于其他具有复杂几何形状的外部非线性问题也非常有用。
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引用次数: 0
A Krylov eigenvalue solver based on filtered time domain solutions 基于滤波时域解的克雷洛夫特征值求解器
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-15 DOI: 10.1016/j.camwa.2024.10.006
Lothar Nannen, Markus Wess
This paper introduces a method for computing eigenvalues and eigenvectors of a generalized Hermitian, matrix eigenvalue problem. The work is focused on large scale eigenvalue problems, where the application of a direct inverse is out of reach. Instead, an explicit time-domain integrator for the corresponding wave problem is combined with a proper filtering and a Krylov iteration in order to solve for eigenvalues within a given region of interest. We report results of small scale model problems to confirm the reliability of the method, as well as the computation of acoustic resonances in a three dimensional model of a hunting horn to demonstrate the efficiency.
本文介绍了一种计算广义赫尔墨斯矩阵特征值问题的特征值和特征向量的方法。这项工作的重点是大规模特征值问题,在这些问题中,直接逆运算的应用是遥不可及的。取而代之的是,相应波问题的显式时域积分器与适当的滤波和克雷洛夫迭代相结合,以求解给定相关区域内的特征值。我们报告了小规模模型问题的结果,以证实该方法的可靠性,并计算了狩猎号角三维模型中的声共振,以证明该方法的效率。
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引用次数: 0
Efficient coupled lattice Boltzmann and Discrete Element Method simulations of small particles in complex geometries 复杂几何形状中的小颗粒的高效耦合晶格玻尔兹曼和离散元素法模拟
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-15 DOI: 10.1016/j.camwa.2024.10.004
Tristan G. Vlogman, Kartik Jain
Many interesting particulate flow problems can only be studied using efficient numerical methods. We present a method based on a lattice Boltzmann fluid coupled to unresolved particles that interact with each other via the Discrete Element Method. Our method improves upon existing numerical schemes through the addition of a novel subcycling algorithm that guarantees momentum conservation during each DEM substep. The intended application is studying transport of solid particles in physiologic processes, although the method is generally applicable. We present in detail the development and (parallel) implementation of the model and show how intricacies of the coupling scheme must be considered to avoid unphysical behavior and instabilities. The scalability of the code is tested on two modern supercomputers. We demonstrate the method's applicability to biomedical applications by simulating the injection and distribution of particles in an idealized liver vasculature.
许多有趣的粒子流问题只能通过高效的数值方法进行研究。我们提出了一种基于晶格玻尔兹曼流体的方法,该流体与未解决的颗粒通过离散元素法相互作用。我们的方法改进了现有的数值方案,增加了新颖的子循环算法,保证了每个 DEM 子步骤中的动量守恒。该方法的预期应用是研究生理过程中固体颗粒的传输,尽管该方法普遍适用。我们详细介绍了该模型的开发和(并行)实施,并展示了必须如何考虑耦合方案的复杂性,以避免非物理行为和不稳定性。代码的可扩展性在两台现代超级计算机上进行了测试。我们通过模拟粒子在理想化肝脏血管中的注入和分布,展示了该方法在生物医学应用中的适用性。
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引用次数: 0
Unconditionally energy stable ESAV-VEM schemes with variable time steps for the time fractional Allen-Cahn equation 针对时间分数艾伦-卡恩方程的具有可变时间步长的无条件能量稳定 ESAV-VEM 方案
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-15 DOI: 10.1016/j.camwa.2024.10.002
Yanping Chen , Qiling Gu , Jian Huang
For the time fractional Allen-Cahn equation, integration of the exponential scalar auxiliary variable (ESAV) time discretization with the virtual element method (VEM) spatial discretization leads to ESAV-VEM schemes on polygonal meshes. The resulting ESAV-VEM algorithms are linear and effective for the completely decoupled computations of the phase variable u and the auxiliary variable r. Based on the positive definiteness of variable-step discrete convolution kernels relevant to L1 and L1-CN time discretizations, the corresponding unconditionally energy boundedness results are proven on arbitrary nonuniform time meshes. By means of the discrete gradient structure of the temporal discretization operator, the discrete energy dissipation laws are developed via a unified framework. Moreover, the discrete energy decay nature coincides with the classical analogies as the fractional order tends to one. Finally, a series of numerical experiments are presented to verify the accuracy and efficiency of the proposed method.
对于时间分数 Allen-Cahn 方程,指数标量辅助变量(ESAV)时间离散化与虚拟元素法(VEM)空间离散化的整合导致了多边形网格上的 ESAV-VEM 方案。基于与 L1 和 L1-CN 时间离散化相关的变步离散卷积核的正定性,在任意非均匀时间网格上证明了相应的无条件能量有界性结果。通过时间离散化算子的离散梯度结构,离散能量耗散规律通过一个统一的框架得到了发展。此外,当分数阶数趋向于 1 时,离散能量衰减性质与经典类比相吻合。最后,通过一系列数值实验验证了所提方法的精度和效率。
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引用次数: 0
Two-level dynamic load-balanced p-adaptive discontinuous Galerkin methods for compressible CFD simulations 用于可压缩 CFD 模拟的两级动态负载平衡 p 自适应非连续伽勒金方法
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-14 DOI: 10.1016/j.camwa.2024.10.008
Yongseok Jang, Emeric Martin, Jean-Baptiste Chapelier, Vincent Couaillier
We present a novel approach utilizing two-level dynamic load balancing for p-adaptive discontinuous Galerkin (DG) methods in compressible Computational Fluid Dynamics (CFD) simulations. The high-order explicit first stage, specifically the singly diagonal implicit Runge–Kutta (ESDIRK) method, is employed for time integration, where the pseudo-transient continuation is integrated with the restarted generalized minimal residual (GMRES) method to handle the solution of nonlinear equations at each stage of ESDIRK, excluding the initial stage. Relying on smoothness indicators, we carry out the refinement/coarsening process for p-adaptation with dynamic load balancing. This approach involves a coarse level (distributed memory) decomposition based on MPI paradigm and a fine level (shared memory) decomposition based on OpenMP paradigm, enhancing parallel efficiency. Dynamic load balancing is achieved by computing weights based on degrees of freedom, ensuring balanced computational loads across processors. The parallel computing framework adopts either a graph-based type (ParMETIS and Zoltan) or space-filling curves type (GeMPa) for coarse level partitioning, and a graph-based type (METIS and Zoltan) for fine level partitioning. The effectiveness of the method is demonstrated through numerical examples, highlighting its potential to significantly improve the scalability and efficiency of compressible flow simulations. The numerical simulations were conducted using the CODA flow solver, a state-of-the-art tool developed collaboratively by the French National Aerospace Center (ONERA), the German Aerospace Center (DLR), and Airbus.
我们提出了一种在可压缩计算流体动力学(CFD)模拟中利用两级动态负载平衡来实现 p 自适应非连续伽勒金(DG)方法的新方法。采用高阶显式第一阶段,特别是单对角隐式 Runge-Kutta (ESDIRK) 方法进行时间积分,其中伪瞬态延续采用重启广义最小残差 (GMRES) 方法进行积分,以处理 ESDIRK 每个阶段(不包括初始阶段)的非线性方程求解。根据平滑度指标,我们对具有动态负载平衡功能的 p 适应性进行了细化/粗化处理。这种方法包括基于 MPI 模式的粗级(分布式内存)分解和基于 OpenMP 模式的细级(共享内存)分解,从而提高了并行效率。动态负载平衡是通过计算基于自由度的权重来实现的,从而确保各处理器之间的计算负载平衡。并行计算框架采用基于图的类型(ParMETIS 和 Zoltan)或空间填充曲线类型(GeMPa)进行粗分区,采用基于图的类型(METIS 和 Zoltan)进行细分区。通过数值示例证明了该方法的有效性,突出了其显著提高可压缩流模拟的可扩展性和效率的潜力。数值模拟使用 CODA 流动求解器进行,这是法国国家航空航天中心(ONERA)、德国航空航天中心(DLR)和空中客车公司合作开发的最先进工具。
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引用次数: 0
A new strategy for a faster matrix assembly in the boundary element method 在边界元法中加快矩阵组装的新策略
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-10 DOI: 10.1016/j.camwa.2024.10.001
Lucas Silveira Campos, Carlos Friedrich Loeffler
This study introduces a new modelling approach that leads to a more efficient process for constructing the matrix system arising from the discretization of integral equations by the boundary element method. This method uses the matrix structure employed in the direct interpolation technique, yielding computational efficiency while maintaining precise outcomes and ensuring convergence as the mesh is refined. To demonstrate the effectiveness of this novel numerical technique, it is applied to solve two-dimensional problems governed by the Laplace equation.
本研究介绍了一种新的建模方法,它能更高效地构建由边界元法离散积分方程产生的矩阵系统。该方法采用了直接插值技术中使用的矩阵结构,在保持精确结果的同时提高了计算效率,并确保了网格细化过程中的收敛性。为了证明这种新型数值技术的有效性,我们将其用于解决由拉普拉斯方程控制的二维问题。
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引用次数: 0
Mixed virtual element methods for the poro-elastodynamics model on polygonal grids 多边形网格上孔隙-弹性力学模型的混合虚拟元素方法
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-08 DOI: 10.1016/j.camwa.2024.09.025
Yanli Chen , Xin Liu , Wenhui Zhang , Yufeng Nie
This work introduces and analyzes the mixed virtual element method on polygonal meshes for the numerical discretization of poro-elastodynamics models. For spatial discretization, we employ the mixed virtual element method on polygonal meshes, coupled with Newmark-β integration schemes for time discretization. We present a stability analysis for both the continuous and semi-discrete problems and derive error estimates for the energy norm in the semi-discrete case. Numerical experiments are conducted to verify the theoretical analysis, and the results on Voronoi meshes demonstrate that the algorithm effectively handles various dynamic viscosities.
本研究介绍并分析了多边形网格上的混合虚拟元素法,用于孔-弹性力学模型的数值离散化。在空间离散化方面,我们采用多边形网格上的混合虚拟元素法,并结合 Newmark-β 积分方案进行时间离散化。我们对连续和半离散问题进行了稳定性分析,并得出了半离散情况下能量规范的误差估计值。我们进行了数值实验来验证理论分析,在 Voronoi 网格上的结果表明,该算法能有效处理各种动态粘度。
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引用次数: 0
Elastic bending total variation model for image inpainting with operator splitting method 用算子分割法绘制图像的弹性弯曲总变化模型
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-08 DOI: 10.1016/j.camwa.2024.09.023
Caixia Nan , Qian Zhang
The elastic bending energy model is commonly used to describe the shape transformation of biological lipid vesicles, making it a classical phase field model. In this paper, by coupling the elastic bending energy with the total variation (TV) regularization, we develop an elastic bending-TV model for image inpainting. By solving the energy minimization problem of this model, we obtain the results for image processing. We adopt an operator splitting method for the model and the numerical scheme involves the introduction of two vector- and scalar-valued functions to reconstruct this functional. The energy minimization problem is transformed into finding the steady state solution of artificial time-dependent PDE systems. At each fractional step, we can find either a closed-form solution or being solved by an efficient algorithm, which is a very robust and stable algorithm. Experimental results validate the superiority of our model and the effectiveness of the scheme for image inpainting.
弹性弯曲能模型常用于描述生物脂质囊泡的形状变化,是一种经典的相场模型。在本文中,通过将弹性弯曲能与总变异(TV)正则化耦合,我们开发了一种用于图像着色的弹性弯曲-TV 模型。通过求解该模型的能量最小化问题,我们获得了图像处理的结果。我们为该模型采用了算子分割法,数值方案包括引入两个矢量和标量值函数来重构该函数。能量最小化问题被转化为寻找人工时变 PDE 系统的稳态解。在每个分步中,我们都能找到闭式解,或通过高效算法求解,这是一种非常稳健和稳定的算法。实验结果验证了我们模型的优越性以及该方案在图像内绘中的有效性。
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引用次数: 0
Theoretical analysis and numerical scheme of local conservative characteristic finite difference for 2-d advection diffusion equations 二维平流扩散方程的局部保守特性有限差分理论分析与数值方案
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-08 DOI: 10.1016/j.camwa.2024.09.032
Yiyang Wang, Zhongguo Zhou
In this paper, the mass conservative characteristic finite difference scheme for 2-d advection diffusion equations is analyzed. Firstly, along x-direction, we obtain the solutions {U˜i,jn} by applying the piecewise parabolic method (PPM) on the Lagrangian grid where x¯ is solved using the first-order Runge Kutta scheme. Secondly, the mass M¯i,jn over Ω¯i,j(tn) are solved by the PPM scheme along y-direction. Finally, the local conservative characteristic finite difference scheme is constructed. By some auxiliary lemmas, we prove our scheme is stable and obtain the optimal error estimate. Our scheme is proved to be of second order convergence in space and of first order in time. Numerical experiments are used to verify the theoretical analysis.
本文分析了二维平流扩散方程的质量守恒特征有限差分方案。首先,沿 x 方向,在拉格朗日网格上应用片断抛物线法(PPM)得到解 {U˜i,jn},其中 x¯ 采用一阶 Runge Kutta 方案求解。其次,采用 PPM 方案沿 y 方向求解 Ω¯i,j(tn)上的质量 M¯i,jn。最后,构建局部保守特征有限差分方案。通过一些辅助定理,我们证明了我们的方案是稳定的,并得到了最优误差估计。我们的方案在空间上具有二阶收敛性,在时间上具有一阶收敛性。数值实验用于验证理论分析。
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引用次数: 0
A posteriori error estimates of Darcy flows with Robin-type jump interface conditions 具有罗宾型跃迁界面条件的达西流的后验误差估计
IF 2.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-10-08 DOI: 10.1016/j.camwa.2024.09.031
Jeonghun J. Lee
In this work we develop an a posteriori error estimator for mixed finite element methods of Darcy flow problems with Robin-type jump interface conditions. We construct an energy-norm type a posteriori error estimator using the Stenberg post-processing. The reliability of the estimator is proved using an interface-adapted Helmholtz-type decomposition and an interface-adapted Scott–Zhang type interpolation operator. A local efficiency and the reliability of post-processed pressure are also proved. Numerical results illustrating adaptivity algorithms using our estimator are included.
在这项研究中,我们开发了一种后验误差估算器,适用于具有罗宾型跃迁界面条件的达西流问题的混合有限元方法。我们利用斯腾伯格后处理方法构建了一个能量正态类型的后验误差估计器。利用界面适应的 Helmholtz 型分解和界面适应的 Scott-Zhang 型插值算子证明了估计器的可靠性。此外,还证明了后处理压力的局部效率和可靠性。还包括使用我们的估算器说明自适应算法的数值结果。
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引用次数: 0
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Computers & Mathematics with Applications
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