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\(hp\)-approximation theory for BDFM and RT finite elements on quadrilaterals. (English) Zbl 1035.65119

Summary: We study approximation properties of \(hp\)-finite element subspaces of \({\mathbf H}(\text{div},\Omega)\) and \({\mathbf H}(\text{rot},\Omega)\) on a polygonal domain \(\Omega\) using Brezzi-Douglas-Fortin-Marini (BDFM) or Raviart-Thomas (RT) elements. Approximation theoretic results are derived for the \(hp\)-version finite element method on non-quasi-uniform meshes of quadrilateral elements with hanging nodes for functions belonging to weighted Sobolev spaces \({\mathbf H}_{\omega}^{s,\ell}(\Omega)\) and the countably normed spaces \({\mathcal B}_{w}^{\ell}(\Omega)\). These results culminate in a proof of the characteristic exponential convergence property of the \(hp\)-version finite element method on suitably designed meshes under similar conditions needed for the analysis of the \({\mathbf H}^{1}(\Omega)\) case. By way of illustration, exponential convergence rates are deduced for mixed \(hp\)-approximation of flow in porous media.

MSC:

65N30 Finite element, Rayleigh-Ritz and Galerkin methods for boundary value problems involving PDEs
76S05 Flows in porous media; filtration; seepage
76M10 Finite element methods applied to problems in fluid mechanics
35J25 Boundary value problems for second-order elliptic equations
65N12 Stability and convergence of numerical methods for boundary value problems involving PDEs
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