Abstract
We consider the numerical approximation of acoustic wave propagation problems by mixed \(\text {BDM}_{k+1}\)–\(\text {P}_k\) finite elements on unstructured meshes. Optimal convergence of the discrete velocity and super-convergence of the pressure are established. Based on these results, we propose a post-processing strategy that allows us to construct an improved pressure approximation from the numerical solution. Corresponding results are well-known for mixed finite element approximations of elliptic problems and we extend these analyses here to the hyperbolic problem under consideration. We also consider the subsequent time discretization by the Crank–Nicolson method and show that the analysis and the post-processing strategy can be generalized to the fully discrete schemes. Our proofs do not rely on duality arguments or inverse inequalities and the results therefore also apply for non-convex domains and non-uniform meshes.
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Acknowledgements
The authors are grateful for financial support by the German Research Foundation (DFG) via Grants IRTG 1529 and TRR 154 project C4, and by the “Excellence Initiative” of the German Federal and State Governments via the Graduate School of Computational Engineering GSC 233 at Technische Universität Darmstadt.
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Egger, H., Radu, B. Super-convergence and post-processing for mixed finite element approximations of the wave equation. Numer. Math. 140, 427–447 (2018). https://doi.org/10.1007/s00211-018-0966-2
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DOI: https://doi.org/10.1007/s00211-018-0966-2