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A compact difference method for the 2-D Kuramoto-Tsuzuki complex equation with Neumann boundary characterized by strong nonlinear effects 具有强非线性效应的二维具有Neumann边界的Kuramoto-Tsuzuki复方程的紧致差分法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-12-04 DOI: 10.1016/j.camwa.2025.11.013
Jinxiu Zhang , Xuehua Yang , Song Wang
This paper develops and analyzes a linearized compact three-levelfinite difference (CTLFD) scheme to solve the two-dimensional (2-D) Kuramoto-Tsuzuki dynamics dominated by strong nonlinear characteristics. This method combines the compact difference method (CDM) in space with the Crank-Nicolson (C-N) scheme in time, achieving an overall convergence rate of O(τ2+hx4+hy4), where τ, hx, and hy represent the time and space step sizes, respectively. Nonlinear terms are linearized in a semi-implicit manner to enhance stability and computational efficiency. A rigorous stability and error analysis is carried out using an energy technique together with mathematical induction, confirming boundedness, uniqueness, and the optimal convergence for the numerical solution under two discrete norms. Finally, three sets of numerical experiments are presented to verify the theoretical results and demonstrate the accuracy and robustness of the proposed scheme.
本文提出并分析了一种线性化紧致三能级有限差分(CTLFD)格式,用于求解具有强非线性特征的二维Kuramoto-Tsuzuki动力学问题。该方法将空间上的紧差分法(CDM)与时间上的Crank-Nicolson (C-N)格式相结合,总体收敛速度为O(τ2+hx4+hy4),其中τ、hx和hy分别表示时间和空间步长。非线性项以半隐式方式线性化,以提高稳定性和计算效率。利用能量技术结合数学归纳法,对两离散范数下数值解的有界性、唯一性和最优收敛性进行了严格的稳定性和误差分析。最后,通过三组数值实验对理论结果进行了验证,验证了所提方案的准确性和鲁棒性。
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引用次数: 0
Time discretization schemes for stochastic subdiffusion and fractional wave equations with integrated additive noise 具有积分加性噪声的随机次扩散和分数阶波动方程的时间离散化方法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-12-04 DOI: 10.1016/j.camwa.2025.11.012
Minghua Chen , Jiankang Shi , Zhen Song , Yubin Yan , Zhi Zhou
In this paper, we introduce a time discretization scheme for solving the stochastic subdiffusion equation based on the two-fold integral-differential and two step backward differentiation formula (ID2-BDF2). We prove that this scheme attains a convergence rate of O(τα+γ1/2) for 1/2<α+γ<2 with α ∈ (0, 1) and γ ∈ [0, 1]. Our approach regularizes the additive noise through a two-fold integral-differential (ID2) calculus and discretizes the equation using BDF2 convolution quadrature, achieving superlinear convergence in solving the stochastic subdiffusion. Furthermore, we extend the scheme to solve the stochastic fractional wave equation, proving that the scheme achieves a convergence rate of O(τmin{2,α+γ1/2}) for α ∈ (1, 2) and γ ∈ [0, 1]. Numerical examples are presented to validate the theoretical results for the linear problem. The numerical observations further indicate that the same convergence rates also apply to stochastic semilinear time-fractional equations.
本文介绍了一种求解随机次扩散方程的时间离散化方案,该方案基于二阶积分-微分和两步后向微分公式(ID2-BDF2)。当α ∈ (0,1),γ ∈ [0,1]时,证明了该格式对于1/2<;α+γ<;2具有O(τα+γ−1/2)的收敛速率。我们的方法通过双重积分-微分(ID2)演算对加性噪声进行正则化,并使用BDF2卷积正交对方程进行离散化,从而在求解随机次扩散时实现超线性收敛。进一步,我们将该方案推广到求解随机分数阶波动方程,证明了对于α ∈ (1,2)和γ ∈ [0,1],该方案的收敛速率为O(τmin{2,α+γ−1/2})。通过数值算例验证了线性问题的理论结果。数值观测进一步表明,相同的收敛速率也适用于随机半线性时间分数方程。
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引用次数: 0
An RBF-FD method for solving elliptic interface problems with non-homogeneous jump conditions on curved surfaces 求解曲面上非齐次跳跃条件椭圆界面问题的RBF-FD方法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-12-01 DOI: 10.1016/j.camwa.2025.11.011
Shengye Zhang, Xufeng Xiao, Yuanyang Qiao, Xinlong Feng
A local meshless radial basis function-finite difference (RBF-FD) method, leveraging polyharmonic spline (PHSn) kernel, is introduced for solving elliptic interface problems with non-homogeneous jump conditions on curved surfaces. The design of the proposed method is based on the splitting of surface region according to the interface, and the quasi-uniformed meshless fitted nodes on the interface and surface. The meshless fitted setting ensures the efficiency of scattered node generation and the simplicity of discretization. Additionally, we ensure the positivity of the basis functions through polyharmonic spline-coupled polynomials, thus making the interpolation matrix invertible. By incorporating the shape parameter-free PHSn function within the RBF-FD framework, our method yields remarkable spatial accuracy, matrix sparsity, and high-order polynomial convergence of second-, third-, and fourth-order in discretizing the surface interface problem. In the numerical experiments section, we comprehensively demonstrate the superiority of our method in terms of accuracy through a series of rigorous tests. Additionally, we explore the influence of diverse factors, including stencil size, polynomial degree, polyharmonic spline exponent, quasi-uniformed scattering distance, and the diffusion coefficient, on the overall efficiency of our method.
提出了一种利用多谐样条核的局部无网格径向基函数有限差分(RBF-FD)方法,用于求解曲面上具有非齐次跳跃条件的椭圆界面问题。该方法的设计基于按界面划分曲面区域,并在界面和曲面上拟均匀无网格拟合节点。无网格拟合设置保证了分散节点生成的效率和离散化的简单性。此外,我们通过多谐样条耦合多项式保证了基函数的正性,从而使插值矩阵可逆。通过在RBF-FD框架内结合无形状参数的PHSn函数,我们的方法在离散表面界面问题时获得了显著的空间精度、矩阵稀疏性和二、三、四阶高阶多项式收敛性。在数值实验部分,我们通过一系列严格的测试,全面论证了我们的方法在精度方面的优越性。此外,我们还探讨了各种因素,包括模板尺寸、多项式度、多谐样条指数、准均匀散射距离和扩散系数,对我们方法的整体效率的影响。
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引用次数: 0
A dual reduced-order modeling method for nonlinear thermoelastic analysis of 3D honeycomb structure 三维蜂窝结构非线性热弹性分析的双降阶建模方法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-12-01 DOI: 10.1016/j.camwa.2025.11.010
Zhen Yin , Ke Liang
The in-plane stiffness of honeycomb structures is several orders of magnitude lower than the material itself, making them an ideal sandwich structure for flexible deformation mechanisms of high-speed aircrafts in a high-temperature environment. Finite element method is widely used to simulate the in-and-out-of-plane large deformation of honeycomb structures; however the high computational cost is still a major bottleneck for fast analysis and optimization design. The existing reduced-order methods are mainly applicable to buckling problems, rather than the in-plane and out-of-plane large deformation case of honeycomb structures. In this work, a geometrically nonlinear reduced-order method considering both the thermal expansion and temperature-dependent material properties is proposed for in-and-out-of-plane large deformation analysis of honeycomb structures subjected to a high temperature field. The dual reduced-order models with only one degree of freedom are constructed for the temperature rise and mechanical loading phases, respectively, based on the third-order equilibrium equations and perturbation method. The constructional efficiency of the reduced system is largely improved by zeroing the fourth-order strain energy variation using the two-field Hellinger-Reissner variational principle and three-dimensional (3D) solid element. The nonlinear predictor solved by the reduced-order model can be corrected when its numerical accuracy is not satisfactory in path-following analysis. Various numerical examples demonstrate that the proposed method has a superior path-following capability for 3D finite element analysis of honeycomb structures.
蜂窝结构的面内刚度比材料本身低几个数量级,是高温环境下高速飞机柔性变形机构的理想夹层结构。有限元法被广泛应用于蜂窝结构面内外大变形的模拟;然而,高计算成本仍然是快速分析和优化设计的主要瓶颈。现有的降阶方法主要适用于屈曲问题,而不适用于蜂窝结构的面内面外大变形情况。在这项工作中,提出了一种考虑热膨胀和温度相关材料特性的几何非线性降阶方法,用于高温场下蜂窝结构的面内外大变形分析。基于三阶平衡方程和微扰法,分别建立了温升阶段和机械加载阶段的单自由度双降阶模型。利用双场Hellinger-Reissner变分原理和三维实体单元将四阶应变能变化归零,大大提高了简化系统的构造效率。用降阶模型求解的非线性预测器在路径跟踪分析中,当其数值精度不能令人满意时,可以进行修正。数值算例表明,该方法对蜂窝结构的三维有限元分析具有良好的路径跟踪能力。
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引用次数: 0
Three-dimensional narrow volume reconstruction method with unconditional stability based on a phase-field lagrange multiplier approach 基于相场拉格朗日乘子法的无条件稳定三维窄体重构方法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-25 DOI: 10.1016/j.camwa.2025.11.009
Renjun Gao, Xiangjie Kong, Dongting Cai, Boyi Fu, Junxiang Yang
Reconstruction of an object from points cloud is essential in prosthetics, medical imaging, computer vision, etc. We present an effective algorithm for an Allen–Cahn-type model of reconstruction, employing the Lagrange multiplier approach. Utilizing scattered data points from an object, we reconstruct a narrow shell by solving the governing equation enhanced with an edge detection function derived from the unsigned distance function. The specifically designed edge detection function ensures the energy stability. By reformulating the governing equation through the Lagrange multiplier technique and implementing a Crank–Nicolson time discretization, we can update the solutions in a stable and decoupled manner. The spatial operations are approximated using the finite difference method, and we analytically demonstrate the unconditional stability of the fully discrete scheme. Comprehensive numerical experiments, including reconstructions of complex 3D volumes such as characters from Star Wars, validate the algorithm’s accuracy, stability, and effectiveness. Additionally, we analyze how specific parameter selections influence the level of detail and refinement in the reconstructed volumes. To facilitate the interested readers to understand our algorithm, we share the computational codes and data in https://github.com/cfdyang521/C-3PO/tree/main.
从点云中重建物体在假肢、医学成像、计算机视觉等领域是必不可少的。本文采用拉格朗日乘子方法,提出了一种有效的allen - cahn型重构模型算法。利用物体上分散的数据点,我们通过求解控制方程,利用无符号距离函数衍生的边缘检测函数来重建窄壳。特别设计的边缘检测功能保证了能量的稳定性。通过拉格朗日乘子技术重新表述控制方程并实现Crank-Nicolson时间离散化,我们可以以稳定和解耦的方式更新解。利用有限差分法对空间运算进行近似,并解析地证明了完全离散格式的无条件稳定性。全面的数值实验,包括重建复杂的三维体,如《星球大战》中的人物,验证了算法的准确性、稳定性和有效性。此外,我们分析了具体的参数选择如何影响重建体的细节和细化水平。为了方便有兴趣的读者理解我们的算法,我们在https://github.com/cfdyang521/C-3PO/tree/main中分享了计算代码和数据。
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引用次数: 0
A second order accurate, and structure-preserving numerical scheme for the thermodynamical consistent Keller–Segel–Navier–Stokes model 热力学一致Keller-Segel-Navier-Stokes模型的二阶精确且保持结构的数值格式
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-24 DOI: 10.1016/j.camwa.2025.11.005
Rui Wang , Cheng Wang , Yuzhe Qin , Zhengru Zhang
In this work, we propose a Keller–Segel–Navier–Stokes (KSNS) model for describing chemotactic phenomena, formulated within the framework of the Energetic Variational Approach (EnVarA). A second-order accurate numerical scheme is developed that rigorously preserves three fundamental properties in discrete sense: the positivity of cell density, mass conservation of cell density, and total energy dissipation. The Keller–Segel subsystem is reformulated as a coupling between an H1 gradient flow with non-constant mobility and an L2 gradient flow, enabling the effective treatment of the nonlinear and singular logarithmic energy potential via a modified Crank-Nicolson scheme. Artificial regularization terms are introduced to enforce positivity preservation. For the fluid dynamics component, we adopt a second-order semi-implicit time discretization. The marker-and-cell (MAC) finite difference approximation is used as the spatial discretization, which ensures a discretely divergence-free velocity field. The proposed numerical method guarantees unique solvability, mass conservation, and total energy stability. Furthermore, through detailed asymptotic expansions and rigorous error analysis, we establish optimal convergence rates. A series of numerical experiments are presented to validate the effectiveness and robustness of both the physical model and the numerical scheme.
在这项工作中,我们提出了一个Keller-Segel-Navier-Stokes (KSNS)模型来描述化学趋化现象,该模型是在能量变分方法(EnVarA)的框架内制定的。建立了一种二阶精确的数值格式,该格式严格地保留了三个基本性质:细胞密度的正性、细胞密度的质量守恒和总能量耗散。Keller-Segel子系统被重新表述为具有非恒定迁移率的H - 1梯度流和L2梯度流之间的耦合,从而能够通过改进的Crank-Nicolson格式有效地处理非线性和奇异对数能量势。引入人工正则化项来加强正性保持。对于流体力学分量,采用二阶半隐式时间离散。采用标记单元有限差分近似作为空间离散化,保证了离散的无发散速度场。所提出的数值方法保证了独特的可解性、质量守恒性和总能量稳定性。此外,通过详细的渐近展开和严格的误差分析,我们建立了最优收敛速率。通过一系列数值实验验证了物理模型和数值方案的有效性和鲁棒性。
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引用次数: 0
Pre-classification based stochastic reduced-order model for time-dependent complex system 基于预分类的时变复杂系统随机降阶模型
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-22 DOI: 10.1016/j.camwa.2025.11.006
Meixin Xiong , Liuhong Chen , Yulan Ning , Ju Ming , Zhiwen Zhang
We propose a novel stochastic reduced-order model (SROM) for complex systems by combining statistical analysis tools. Based on the generalizability of distance in the centroidal Voronoi tessellation (CVT) method and the minimization of projection error in proper orthogonal decomposition (POD), we define a time-dependent generalized CVT clustering. Each generalized centroid corresponds to a set of cluster-based POD (CPOD) basis functions. Then, using the clustering results as the training dataset, the classification mechanism of the system input can be obtained by applying the naive Bayesian method. For a given input sample, the predicted label obtained by the classifier is used to determine a set of CPOD basis functions for model reduction. Rigorous error analysis is shown, and a discussion of the Navier-Stokes equation with random parameters is given to provide a context for the application of this SROM. Numerical experiments verify that the accuracy of our SROM is improved compared with the standard POD method.
结合统计分析工具,提出了一种复杂系统的随机降阶模型。基于质心Voronoi镶嵌法(CVT)中距离的可泛化性和适当正交分解(POD)中投影误差的最小化,定义了一种时变广义CVT聚类。每个广义质心对应一组基于聚类的POD (CPOD)基函数。然后,将聚类结果作为训练数据集,应用朴素贝叶斯方法得到系统输入的分类机制。对于给定的输入样本,使用分类器获得的预测标签来确定一组CPOD基函数,用于模型约简。给出了严格的误差分析,并讨论了带有随机参数的Navier-Stokes方程,为该存储器的应用提供了一个背景。数值实验表明,与标准的POD方法相比,该方法的精度得到了提高。
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引用次数: 0
Prediction-correction method for nonlinear partial differential equations based on sparse grid interpolation techniques 基于稀疏网格插值技术的非线性偏微分方程预测校正方法
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-20 DOI: 10.1016/j.camwa.2025.11.007
Chenglong Xu , Yining Qiu , Keyan Wang , Bihao Su
This article proposes a prediction-correction method for solving nonlinear partial differential equations (PDEs) in complex multidimensional domains. Our approach employs the Feynman-Kac formula, which establishes a connection between stochastic differential equations and PDEs, along with multidimensional function interpolation and corresponding integration methods based on sparse grid nodes. First, we derive the relationship between solutions of discrete-time PDEs using the Feynman-Kac formula. Next, we establish a discretization scheme through integration over sparse grid points and then construct the expression of each time-layer solution via interpolation on these points. Prediction-correction techniques are applied to address the integration of nonlinear unknown functions. While deriving a prediction-correction numerical method, this paper also presents a rigorous theoretical error analysis of the method. The effectiveness and convergence of the proposed method are validated through two types of examples. Compared with traditional numerical methods, our method enables efficient handling of more complex and multidimensional regions.
提出了一种求解复杂多维域非线性偏微分方程的预测-修正方法。我们的方法采用费曼-卡茨公式,该公式建立了随机微分方程与偏微分方程之间的联系,以及基于稀疏网格节点的多维函数插值和相应的积分方法。首先,我们利用费曼-卡茨公式推导了离散时间偏微分方程解之间的关系。其次,通过对稀疏网格点的积分建立离散化方案,然后在这些点上通过插值构造每个时间层解的表达式。应用预测校正技术解决非线性未知函数的积分问题。本文在推导预测校正数值方法的同时,对该方法进行了严格的理论误差分析。通过两类算例验证了该方法的有效性和收敛性。与传统的数值方法相比,该方法能够有效地处理更复杂和多维的区域。
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引用次数: 0
Convergence and numerical simulations of the continuous data assimilation for Biot's poroelasticity system Biot孔隙弹性系统连续数据同化的收敛性与数值模拟
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-20 DOI: 10.1016/j.camwa.2025.11.008
Seungmin Lee, Sanghyun Lee
Real-world applications often suffer from incomplete or uncertain data, which can undermine the accuracy of physical models. In our work, we tackle this challenge by applying continuous data assimilation (CDA) to Biot's poroelasticity system, a model that captures how fluid-saturated porous materials, such as soils or biological tissues, deform under stress. We utilize a nudging term in the conservation of mass equation to integrate sparse observational data directly into the pressure field. We then use an iterative fixed-stress method to decouple the pressure and displacement problem, making the process both stable and efficient. Our approach employs finite element methods along with an interpolation strategy that adapts to different data resolutions. Several numerical tests illustrate that the proposed method reliably drives the model's predictions towards the true state, even in complex scenarios involving heterogeneous permeability or nonlinear permeability, and including a three dimensional setup. This study is the first to rigorously apply CDA to Biot's poroelasticity system, offering a promising avenue for more accurate predictive modeling in fields ranging from geomechanics to biomechanics.
现实世界的应用经常受到不完整或不确定数据的影响,这可能会破坏物理模型的准确性。在我们的工作中,我们通过将连续数据同化(CDA)应用于Biot的孔隙弹性系统来解决这一挑战,该系统是一个捕获流体饱和多孔材料(如土壤或生物组织)在应力下如何变形的模型。我们利用质量守恒方程中的轻推项将稀疏观测数据直接积分到压力场中。然后,我们使用迭代固定应力方法来解耦压力和位移问题,使过程既稳定又高效。我们的方法采用有限元方法以及适应不同数据分辨率的插值策略。几个数值试验表明,即使在涉及非均质渗透率或非线性渗透率的复杂场景中,包括三维设置,所提出的方法也能可靠地将模型的预测推向真实状态。该研究首次将CDA严格应用于Biot的孔隙弹性系统,为从地质力学到生物力学等领域更准确的预测建模提供了一条有希望的途径。
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引用次数: 0
Meshless and FEM approximations for mixed polytopal elements 混合多面体单元的无网格和有限元逼近
IF 2.5 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2025-11-19 DOI: 10.1016/j.camwa.2025.11.003
Witold Cecot , Marta Oleksy , Mateusz Dryzek
This paper presents a comparison of various approaches to approximating the unknown functions within the mixed ultra-weak formulation, using Voronoi polygon discretization and stabilization via the Discontinuous Petrov–Galerkin (DPG) methodology. The primary objective is to identify the basis functions that offer the best approximability. We consider meshless functions, which have not previously been applied to fully mixed formulations (stress–displacement in mechanics), and compare several of their variants with polynomial approximations. Numerical tests are conducted for the Laplace equation on both square and L-shaped domains, for regular as well as singular solutions. Our study reveals that, with one exception, the polynomial approximation—particularly the orthogonal Legendre type—exhibits faster convergence, most likely due to its superior interpolation properties in the two-field formulation. The findings of this study can be extended to other elliptic problems, including those in solid mechanics, where mixed formulations and polygonal finite elements offer significant advantages.
本文介绍了利用Voronoi多边形离散化和不连续Petrov-Galerkin (DPG)方法稳定混合超弱公式中未知函数的各种近似方法的比较。主要目标是确定提供最佳逼近性的基函数。我们考虑无网格函数,它以前没有被应用于完全混合的公式(力学中的应力-位移),并将它们的几种变体与多项式近似进行比较。对拉普拉斯方程在正方形和l形域、正则解和奇异解上进行了数值试验。我们的研究表明,除了一个例外,多项式近似-特别是正交Legendre型-表现出更快的收敛,很可能是由于其在双场公式中的优越插值特性。本研究的发现可以推广到其他椭圆问题,包括固体力学中的混合公式和多边形有限元提供显著优势的问题。
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引用次数: 0
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