arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2201.09721math.NAcs.NA
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Helmholtz边界元法是否存在污染效应?

Does the Helmholtz boundary element method suffer from the pollution effect?

Jeffrey Galkowski, Euan A. Spence

摘要:

在$d$维中,精确地近似以频率$\lesssim k$振荡的任意函数需要$\sim k^d$自由度。如果作为$k$,保持精度所需的自由度的总数增长得比该自然阈值(即,对于基于域的公式,例如有限元方法,比$k^d$快,对于基于边界的公式,例如边界元方法,比$k^{d-1}$快)。众所周知,有限元法(FEM)的$h$版本(其中通过减小网格宽度$h$并保持多项式次数$p$固定来提高精度)受到污染效应的影响,并且在过去$\sim$ 30年的研究已经导致了对自由度的数量必须以多快的速度随着$k$增长以保持精度的近乎完整的严格理解。与$h$-FEM相反,至少在经验上,$h$ -版本的边界元方法(BEM)使$\textit{not}$遭受污染效应(回想一下,在边界元方法中,散射问题被重新表述为散射体边界上的积分方程,然后使用有限元型近似空间数值求解该积分方程)。然而,目前文献中关于$h$-BEM的自由度的数量必须随着$k$增长以保持精度的最佳结果未能证明这一点。在本文中,我们证明了应用于标准第二类边界积分方程的Galerkin方法的PDMATHAMT-版本,用于求解Helmholtz外Dirichlet问题,当障碍物是非捕获的(即,不捕获几何光学射线)。

英文摘要:

In $d$ dimensions, accurately approximating an arbitrary function oscillating with frequency $\lesssim k$ requires $\sim k^d$ degrees of freedom. A numerical method for solving the Helmholtz equation (with wavenumber $k$ and in $d$ dimensions) suffers from the pollution effect if, as $k\to\infty$, the total number of degrees of freedom needed to maintain accuracy grows faster than this natural threshold (i.e., faster than $k^d$ for domain-based formulations, such as finite element methods, and $k^{d-1}$ for boundary-based formulations, such as boundary element methods). It is well known that the $h$-version of the finite element method (FEM) (where accuracy is increased by decreasing the meshwidth $h$ and keeping the polynomial degree $p$ fixed) suffers from the pollution effect, and research over the last $\sim$ 30 years has resulted in a near-complete rigorous understanding of how quickly the number of degrees of freedom must grow with $k$ to maintain accuracy. In contrast to the $h$-FEM, at least empirically, the $h$-version of the boundary element method (BEM) does $\textit{not}$ suffer from the pollution effect (recall that in the boundary element method the scattering problem is reformulated as an integral equation on the boundary of the scatterer, with this integral equation then solved numerically using a finite-element-type approximation space). However, the current best results in the literature on how quickly the number of degrees of freedom for the $h$-BEM must grow with $k$ to maintain accuracy fall short of proving this. In this paper, we prove that the $h$-version of the Galerkin method applied to the standard second-kind boundary integral equations for solving the Helmholtz exterior Dirichlet problem does not suffer from the pollution effect when the obstacle is nontrapping (i.e., does not trap geometric-optic rays).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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