A Nonconforming Arbitrary Quadrilateral Finite Element Method for Approximating Maxwell's Equations

The main aim of this paper is to provide convergence analysis of Quasi-Wilson nonconforming finite element to Maxwell's equations under arbitrary quadrilateral meshes.The error estimates are derived,which are the same as those for conforming elements under conventional regular meshes.     

A Nonconforming Arbitrary Quadrilateral Finite Element Method for Approximating Maxwell＇s Equations

The main aim of this paper is to provide convergence analysis of Quasi-Wilson nonconforming finite element to Maxwell's equations under arbitrary quadrilateral meshes. The error estimates are derived, which are the same as those for conforming elements under conventional regular meshes.     

Zienkiewicz元插值的非各向异性估计

本文证明著名的用于四阶椭圆问题尤其是板弯曲问题的Zienkiewicz元的插值误差在各向异性网格下不收敛, 从而表明, 发展各向异性有限元的理论和单元构造是必要的.     

CONVERGENCE ANALYSIS FOR A NONCONFORMING MEMBRANE ELEMENT ON ANISOTROPIC MESHES

Regular assumption of finite element meshes is a basic condition of most analysis offinite element approximations both for conventional conforming elements and nonconform-ing elements.The aim of this paper is to present a novel approach of dealing with theapproximation of a four-degree nonconforming finite element for the second order ellipticproblems on the anisotropic meshes.The optimal error estimates of energy norm and L~2-norm without the regular assumption or quasi-uniform assumption are obtained based onsome new special features of this element discovered herein.Numerical results are givento demonstrate validity of our theoretical analysis.     

Anisotropic Superconvergence Analysis for the Wilson Nonconforming Element

1 Introduction The Wilson nonconforming element has been widely used in computational mechanics and struc- tural engineering because of its good convergence. In many practical cases, it seems better than the bilinear conforming finite element. This phenomenon causes the great interest of many people who study finite elements. Some papers about the Wilson element have been published which deal with superconvergence. In [6], the superclose property and the global superconvergence are obtained …     

Stokes问题的各向异性误差分析

对二维空间Stokes问题提出了各向异性平行四边形混合有限元逼近格式,证明了其在不要求满足正则性和拟一致条件下的收敛性以及在各向异性条件下对相容误差部分的超收敛估计.     

Stokes问题的各向异性平行四边形有限元逼近

1 引言 Stokes问题是标准的混合问题,速度与压力同时计算,关于该问题有限元求解的文章很多(见文献[1-5])但大多都是基于对区域的正则剖分或拟一致剖分,即要求网格剖分满足hk/pK≤C,(A)K∈Jh,其中C>0为一常数,hk,pK分别为单元K的直径及内切园直径,在实际应用问题中,由于边界层或区域的拐角处需考虑物质的各向异性特征,此时对空间区域Q的剖分不再满足正则性或拟一致条件,而需要用各向异性网格剖分,才能更贴切地描述其真实情形.     

Darcy-Stokes问题的统一稳定化有限体积法分析

本文对Darcy-Stokes问题提出了一种统一的稳定化有限体积法.在离散问题中,采用两种剖分,一种为三角形剖分,一种为其对偶四边形剖分.速度及压力分别采用非协调线性元及分片常数元来做逼近.经证明,文中的统一格式,具有稳定性及最优误差估计.最后用数值算例验证了本文的理论结果.     

特征值问题的Lagrange型各向异性有限元方法

在各向异性网格下首先研究了二阶椭圆特征值问题算子谱逼近的若干抽象结果.然后将这些结果具体应用于线性和双线性Lagrange型协调有限元,得到了与传统有限元网格剖分下相同的最优误差估计,从而拓宽了已有的成果.     

Raviart-Thomas混合元的超收敛

考虑二阶椭圆方程Dirichlet边值问题在正则矩形网格上k阶RaviartThomas混合有限元的超收敛.对有限元解经插值处理后,与通常的有限元最优误差估计相比,收敛速度提高了两阶.     

ON THE SELECTION OF SHAPE FUNCTION SPACES OF TRIANGULAR PLATE ELEMENTS

ＯＮＴＨＥＳＥＬＥＣＴＩＯＮＯＦＳＨＡＰＥＦＵＮＣＴＩＯＮＳＰＡＣＥＳＯＦＴＲＩＡＮＧＵＬＡＲＰＬＡＴＥＥＬＥＭＥＮＴＳＣｈｅｎＳｈａｏｃｈｕｎ；ＳｈｉＤｏｎｇｙａｎｇ（Ｄｅｐｔ．ｏｆＳｙｓ．Ｓｃｉ．＆Ｍａｔｈ．，ＺｈｅｎｇｚｈｏｕＵｎｉｖ．，Ｚｈｅ...     

Three‐dimensional quadratic nonconforming brick element

A new nonconforming brick element with quadratic convergence for the energy norm is introduced. The nonconforming element consists of on a cube [?1,1]³, and 14 degree of freedom (DOF). Two types of DOF are introduced. One consists of the value at the eight vertices and six face‐centroids and the other consists of the value at the eight vertices and the integration value of six faces. Error estimates of optimal order are derived in both broken energy and norms for second‐order elliptic problems. If a genuine hexahedron, which is not a parallelepiped, is included in the partition, the proposed element is also convergent, but with a lower order. Copyright © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 158–174, 2014     

一个新的非常规Hermite型各向异性矩形元的超收敛分析及外推

本文对二阶椭圆问题构造了一个新的非常规Hermite型矩形单元并用各向异性插值基本定理证明了其各向异性特征,从而可用于任意的矩形剖分.同时还得到了与网格的正则性假设和拟一致假设无关的超逼近和超收敛性质以及外推.数值结果表明该单元确实是一个具有很好应用价值的单元且与理论分析是相吻合的.     

流线扩散有限元方法在分层网格上的收敛性分析

本文在分层网格上分析了采用线性元的流线扩散有限元方法求解一维对流扩散型奇异摄动问题的一致收敛性.在ε≤N~(-1)的前提下,可以证明在SD范数下的一致误差估计为O(N~(-1)(log 1/ε)~2)在数值算例部分对理论结果进行了验证.     

Polynomial preserving recovery for quadratic elements on anisotropic meshes

Polynomial preserving gradient recovery technique under anisotropic meshes is further studied for quadratic elements. The analysis is performed for highly anisotropic meshes where the aspect ratios of element sides are unbounded. When the mesh is adapted to the solution that has significant changes in one direction but very little, if any, in another direction, the recovered gradient can be superconvergent. The results further explain why recovery type error estimator is robust even under nonstandard and highly distorted meshes. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011     

Low order Crouzeix-Raviart type nonconforming finite element methods for the 3D time-dependent Maxwell’s equations

Two Crouzeix-Raviart type nonconforming elements are used in a finite element scheme as well in a mixed finite element scheme for time-dependent Maxwell’s equations in three dimensions. The error estimates are obtained under anisotropic meshes, which are the same as those for conforming elements under regular meshes.     

本征值问题有限元近似解的外推方法

§1.引言利用外推算法提高有限元近似解的精度,我们曾对二阶椭圆型问题进行研究,本文中将继[1]之后,讨论本征值问题有限元解的外推方法.不失一般性,仅讨论下述模型问题,但本文方法和结论可以推广到一般二阶椭圆型偏微分算子上.考虑     

CONVERGENCE ANALYSIS OF MORLEY ELEMENT ON ANISOTROPIC MESHES

The main aim of this paper is to study tile convergence of a nonconforming triangular plate element-Morley element under anisotropic meshes. By a novel approach, an explicit bound for the interpolation error is derived for arbitrary triangular meshes （which even need not satisfy the maximal angle condition and the coordinate system condition ）, the optimal consistency error is obtained for a family of anisotropically graded finite element meshes.     

A finite element method for the axisymmetric three‐field Stokes system with a discontinuous pressure

A quadrilateral based velocity‐pressure‐extrastress tensor mixed finite element method for solving the three‐field Stokes system in the axisymmetric case is studied. The method derived from Fortin's Q₂ − P₁ velocity‐pressure element is to be used in connection with the standard Galerkin formulation. This makes it particularly suitable for the numerical simulation of viscoelastic flow. It is proven to be second‐order convergent in the natural weighted Sobolev norms, for the system under consideration. The crucial result that the method is uniformly stable is proven for the case of rectangular meshes. © 1999 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 15: 739–763, 1999     

二阶椭圆方程Dirichlet边值问题混合元的超收敛

关于二阶椭圆方程Dirichlet边值问题混合元的超收敛,在正则矩形网格上,林群和林甲富在文[1]中,采用一阶Raviart-Thomas混合元空间,对有限元解经后处理后,其收敛于精确解的速度从二阶提高到四阶.本文拟将这一结果进行推广,讨论二阶椭圆方程Dirichlet边值问题的k阶Raviart-Thomas混合元的超收敛,得到了以k 3阶速度收敛于精确解的有限元解.