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arXiv 1802.01896math.NAcs.NA
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利用非一致元素的高精度椭圆算子本征值方法

High accuracy methods for eigenvalues of elliptic operators by nonconforming elements

LMAM and School of Mathematical Sciences, Peking University(北京大学数学科学学院)

Jun Hu, Limin Ma

AI总结:

本文提出三种高精度方法,通过非一致Crouzeix-Raviart元素和非一致增强Crouzeix-Raviart元素计算椭圆算子的本征值,利用RT元素的一阶超收敛性改进了现有结果。

摘要:

本文提出三种高精度方法,通过非一致Crouzeix-Raviart(CR)元素和非一致增强Crouzeix-Raviart(ECR)元素计算第二阶椭圆算子的本征值。这些方法基于一阶混合Raviart-Thomas(RT)元素的一阶完全超收敛性。超收敛分析的关键在于利用RT元素解与标准插值之间的差值的离散霍尔姆霍兹分解。特别地,这种分解允许某些关键边界项中的项之间产生重要抵消。因此,CR元素与RT元素之间的特殊关系以及ECR元素与RT元素之间的等价性导致了一阶完全超收敛性。这些超收敛结果将RT元素、CR元素和ECR元素的超收敛性从半阶提升到一阶。基于RT元素的上述超收敛性,建立了本征值的渐近展开,并用于实现这两种非一致元素的高精度外推方法。与文献中的经典分析不同,本文的创新之处在于不仅使用这些非一致元素的标准插值,还使用RT元素的插值来分析渐近展开。基于这些非一致元素的超收敛性,构建并分析了这些元素的渐近精确后验误差估计器。最后,提出两种后处理方法,通过使用这些后验误差估计器提高近似本征值的精度。提供了数值测试以验证和比较上述方法的性能。

英文摘要:

In this paper, three high-accuracy methods for eigenvalues of second order elliptic operators are proposed by using the nonconforming Crouzeix-Raviart(CR for short) element and the nonconforming enriched Crouzeix-Raviart(ECR for short) element. They are based on a crucial full one order superconvergence of the first order mixed Raviart-Thomas(RT for short) element. The main ingredient of such a superconvergence analysis is to employ a discrete Helmholtz decomposition of the difference between the canonical interpolation and the finite element solution of the RT element. In particular, it allows for some vital cancellation between terms in one key sum of boundary terms. Consequently, a full one order superconvergence follows from a special relation between the CR element and the RT element, and the equivalence between the ECR element and the RT element for these two nonconforming elements. These superconvergence results improve those in literature from a half order to a full one order for the RT element, the CR element and the ECR element. Based on the aforementioned superconvergence of the RT element, asymptotic expansions of eigenvalues are established and employed to achieve high accuracy extrapolation methods for these two nonconforming elements. In contrast to a classic analysis in literature, the novelty herein is to use not only the canonical interpolations of these nonconforming elements but also that of the RT element to analyze such asymptotic expansions. Based on the superconvergence of these nonconforming elements, asymptotically exact a posteriori error estimators of eigenvalues are constructed and analyzed for them. Finally, two post-processing methods are proposed to improve accuracy of approximate eigenvalues by employing these a posteriori error estimators.Numerical tests are provided to justify and compare the performance of the aforementioned methods.

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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