二维泊松方程的收敛自适应算法

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"这篇文章是关于在二维空间中解决泊松方程的一种收敛自适应算法的研究。作者Willy Dörfler在1996年发表于《SIAM Journal on Numerical Analysis》上,该算法针对线性元素,具有收敛性质。文章受到了583次引用,并有209次阅读,作者还参与了与之相关的Lattice Boltzmann Methods和Wave phenomena项目。" 泊松方程是偏微分方程中的一个基础问题,常用于描述各种物理现象,如电势、流体流动和热传导等。在数值计算中,泊松方程的解通常需要通过离散化方法,如有限元法或有限差分法来求解。而自适应算法则是在这些离散化方法的基础上,根据解的特性动态调整网格,以提高计算效率和精度。 Willy Dörfler提出的方法首先从宏观三角剖分开始,基于先验信息构建初始的三角剖分网络。这种方法允许算法根据问题的复杂性和解的特性,自动细化或粗化网格。这样的自适应策略可以确保在需要更高精度的区域(例如边界层或奇异点附近)增加网格密度,而在其他相对平滑的区域保持较低的网格密度,从而节省计算资源。 自适应算法的关键在于其收敛性,即经过一定次数的迭代,算法能收敛到问题的真实解。在这篇文章中,Dörfler证明了所提出的算法具有收敛性,这对于保证算法的有效性和可靠性至关重要。此外,他还可能探讨了误差估计和标记策略,这些是自适应算法的核心组成部分,它们帮助决定何时以及在哪部分网格上进行细化或粗化。 在实际应用中,这种自适应算法对于处理复杂几何形状或具有非均匀特性的物理问题尤其有用。例如,在处理具有尖锐边界或局部变化的流体动力学问题时,自适应算法可以提供更精确的结果,同时减少不必要的计算负担。 这篇论文对数值分析和科学计算领域有着重要的贡献,它提供了泊松方程求解的一个高效且收敛的自适应算法,这为后续研究和工程实践提供了理论基础和技术手段。

For macroscopically anisotropic media in which the variations in the phase stiffness tensor are small, formal solutions to the boundary-value problem have been developed in the form of perturbation series (Dederichs and Zeller, 1973; Gubernatis and Krumhansl, 1975 ; Willis, 1981). Due to the nature of the integral operator, one must contend with conditionally convergent integrals. One approach to this problem is to carry out a “renormalization” procedure which amounts to identifying physically what the conditionally convergent terms ought to contribute and replacing them by convergent terms that make this contribution (McCoy, 1979). For the special case of macroscopically isotropic media, the first few terms of this perturbation expansion have been explicitly given in terms of certain statistical correlation functions for both three-dimensional media (Beran and Molyneux, 1966 ; Milton and Phan-Thien, 1982) and two-dimensional media (Silnutzer, 1972 ; Milton, 1982). A drawback of all of these classical perturbation expansions is that they are only valid for media in which the moduli of the phases are nearly the same, albeit applicable for arbitrary volume fractions. In this paper we develop new, exact perturbation expansions for the effective stiffness tensor of macroscopically anisotropic composite media consisting of two isotropic phases by introducing an integral equation for the so-called “cavity” strain field. The expansions are not formal but rather the nth-order tensor coefficients are given explicitly in terms of integrals over products of certain tensor fields and a determinant involving n-point statistical correlation functions that render the integrals absolutely convergent in the infinite-volume limit. Thus, no renormalization analysis is required because the procedure used to solve the integral equation systematically leads to absolutely convergent integrals. Another useful feature of the expansions is that they converge rapidly for a class of dispersions for all volume fractions, even when the phase moduli differ significantly.

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