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Two-level stabilized nonconforming finite element method for the Stokes equations

Haiyan Su, Pengzhan Huang, Xinlong Feng (2013)

Applications of Mathematics

In this article, we present a new two-level stabilized nonconforming finite elements method for the two dimensional Stokes problem. This method is based on a local Gauss integration technique and the mixed nonconforming finite element of the N C P 1 - P 1 pair (nonconforming linear element for the velocity, conforming linear element for the pressure). The two-level stabilized finite element method involves solving a small stabilized Stokes problem on a coarse mesh with mesh size H and a large stabilized Stokes...

Two-sided a posteriori error estimates for linear elliptic problems with mixed boundary conditions

Sergey Korotov (2007)

Applications of Mathematics

The paper is devoted to verification of accuracy of approximate solutions obtained in computer simulations. This problem is strongly related to a posteriori error estimates, giving computable bounds for computational errors and detecting zones in the solution domain where such errors are too large and certain mesh refinements should be performed. A mathematical model consisting of a linear elliptic (reaction-diffusion) equation with a mixed Dirichlet/Neumann/Robin boundary condition is considered...

Two-sided bounds of the discretization error for finite elements

Michal Křížek, Hans-Goerg Roos, Wei Chen (2011)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

We derive an optimal lower bound of the interpolation error for linear finite elements on a bounded two-dimensional domain. Using the supercloseness between the linear interpolant of the true solution of an elliptic problem and its finite element solution on uniform partitions, we further obtain two-sided a priori bounds of the discretization error by means of the interpolation error. Two-sided bounds for bilinear finite elements are given as well. Numerical tests illustrate our theoretical analysis....

Two-sided bounds of the discretization error for finite elements

Michal Křížek, Hans-Goerg Roos, Wei Chen (2011)

ESAIM: Mathematical Modelling and Numerical Analysis

We derive an optimal lower bound of the interpolation error for linear finite elements on a bounded two-dimensional domain. Using the supercloseness between the linear interpolant of the true solution of an elliptic problem and its finite element solution on uniform partitions, we further obtain two-sided a priori bounds of the discretization error by means of the interpolation error. Two-sided bounds for bilinear finite elements are given as well. Numerical tests illustrate our theoretical analysis. ...

Une méthode nodale appliquée à un problème de diffusion à coefficients généralisés

Abdelkader Laazizi, Nagib Guessous (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

In this paper, we consider second order neutrons diffusion problem with coefficients in L∞(Ω). Nodal method of the lowest order is applied to approximate the problem's solution. The approximation uses special basis functions [1] in which the coefficients appear. The rate of convergence obtained is O(h2) in L2(Ω), with a free rectangular triangulation.

What is the smallest possible constant in Céa's lemma?

Wei Chen, Michal Křížek (2006)

Applications of Mathematics

We consider finite element approximations of a second order elliptic problem on a bounded polytopic domain in ℝ d with d ∈ { 1 , 2 , 3 , ... } . The constant C ≥ 1 appearing in Céa’s lemma and coming from its standard proof can be very large when the coefficients of an elliptic operator attain considerably different values. We restrict ourselves to regular families of uniform partitions and linear simplicial elements. Using a lower bound of the interpolation error and the supercloseness between the finite element solution and...

Zienkiewicz–Zhu error estimators on anisotropic tetrahedral and triangular finite element meshes

Gerd Kunert, Serge Nicaise (2003)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

We consider a posteriori error estimators that can be applied to anisotropic tetrahedral finite element meshes, i.e. meshes where the aspect ratio of the elements can be arbitrarily large. Two kinds of Zienkiewicz–Zhu (ZZ) type error estimators are derived which originate from different backgrounds. In the course of the analysis, the first estimator turns out to be a special case of the second one, and both estimators can be expressed using some recovered gradient. The advantage of keeping two different...

Zienkiewicz–Zhu error estimators on anisotropic tetrahedral and triangular finite element meshes

Gerd Kunert, Serge Nicaise (2010)

ESAIM: Mathematical Modelling and Numerical Analysis

We consider a posteriori error estimators that can be applied to anisotropic tetrahedral finite element meshes, i.e. meshes where the aspect ratio of the elements can be arbitrarily large. Two kinds of Zienkiewicz–Zhu (ZZ) type error estimators are derived which originate from different backgrounds. In the course of the analysis, the first estimator turns out to be a special case of the second one, and both estimators can be expressed using some recovered gradient. The advantage of keeping two...

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