Polynomial robust stability analysis for H(div)-conforming finite elements for the Stokes equations

Abstract

In this work we consider a discontinuous Galerkin method for the discretization of the Stokes problem. We use H(div)-conforming finite elements as they provide major benefits such as exact mass conservation and pressure-independent error estimates. The main aspect of this work lies in the analysis of high order approximations. We show that the considered method is uniformly stable with respect to the polynomial order k and provides optimal error estimates ∥u−uh∥1h+∥ΠQhp−ph∥≤c(h/k)s∥u∥s+1. To derive those estimates, we prove a k-robust LBB condition. This proof is based on a polynomial H2-stable extension operator. This extension operator itself is of interest for the numerical analysis of C0-continuous discontinuous Galerkin methods for 4th order problems.