## Mathematics and Statistics Faculty Publications and Presentations

#### Title

Analysis of HDG Methods for Stokes Flow

#### Published In

Mathematics of Computation

Article

2011

#### Subjects

Galerkin methods, Stokes flow, Discontinuous functions, Numerical analysis, Approximation theory, Polynomials

#### Abstract

In this paper, we analyze a hybridizable discontinuous Galerkin method for numerically solving the Stokes equations. The method uses polynomials of degree $k$ for all the components of the approximate solution of the gradient-velocity-pressure formulation. The novelty of the analysis is the use of a new projection tailored to the very structure of the numerical traces of the method. It renders the analysis of the projection of the errors very concise and allows us to see that the projection of the error in the velocity superconverges. As a consequence, we prove that the approximations of the velocity gradient, the velocity and the pressure converge with the optimal order of convergence of $k+1$ in $L[superscript 2]$ for any $k [greater than or equal to] 0$. Moreover, taking advantage of the superconvergence properties of the velocity, we introduce a new element-by-element postprocessing to obtain a new velocity approximation which is exactly divergence-free, $\mathbf{H}($div$)$-conforming, and converges with order $k+2$ for $k[greater than or equal to]1$ and with order $1$ for $k=0$. Numerical experiments are presented which validate the theoretical results.

#### DOI

10.1090/S0025-5718-2010-02410-X

#### Persistent Identifier

http://archives.pdx.edu/ds/psu/10628

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