Paper Info
Title
Rehabilitation of the Lowest-Order Raviart-Thomas Element on Quadrilateral Grids
Abstract
A recent study [D. N. Arnold, D. Boffi, and R. S. Falk, SIAM J. Numer. Anal., 42 (2005), pp. 2429-2451] reveals that convergence of finite element methods using $H(\mathrm{div}\,,\Omega)$-compatible finite element spaces deteriorates on nonaffine quadrilateral grids. This phenomena is particularly troublesome for the lowest-order Raviart-Thomas elements, because it implies loss of convergence in some norms for finite element solutions of mixed and least-squares methods. In this paper we propose reformulation of finite element methods, based on the natural mimetic divergence operator [M. Shashkov, Conservative Finite Difference Methods on General Grids, CRC Press, Boca Raton, FL, 1996], which restores the order of convergence. Reformulations of mixed Galerkin and least-squares methods for the Darcy equation illustrate our approach. We prove that reformulated methods converge optimally with respect to a norm involving the mimetic divergence operator. Furthermore, we prove that standard and reformulated versions of the mixed Galerkin method lead to identical linear systems, but the two versions of the least-squares method are veritably different. The surprising conclusion is that the degradation of convergence in the mixed method on nonaffine quadrilateral grids is superficial, and that the lowest-order Raviart-Thomas elements are safe to use in this method. However, the breakdown in the least-squares method is real, and there one should use our proposed reformulation.
Year
DOI
Venue
2008
10.1137/070704265
SIAM J. Numerical Analysis
Keywords
Field
DocType
finite element solution,finite element method,least-squares method,lowest-order raviart-thomas element,nonaffine quadrilateral grid,compatible finite element space,mixed method,methods converge optimally,mixed galerkin method lead,mixed galerkin,quadrilateral grids,quadrilateral,mixed methods
Applied mathematics,Mathematical analysis,Galerkin method,Finite element method,Rate of convergence,Quadrilateral,Finite difference method,Numerical analysis,Mathematics,Numerical linear algebra,Calculus,Mixed finite element method
Journal
Volume
Issue
ISSN
47
1
0036-1429
Citations 
PageRank 
References 
7
0.57
6
Authors
2
Name
Order
Citations
PageRank
Pavel B. Bochev138267.69
Denis Ridzal2759.99