A stable discontinuous Galerkin method for the perfectly matched layer for elastodynamics in first order form
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Numerische Mathematik
A stable discontinuous Galerkin method for the perfectly matched layer for elastodynamics in first order form Kenneth Duru1 · Leonhard Rannabauer2 · Alice-Agnes Gabriel3 · Gunilla Kreiss4 · Michael Bader2 Received: 26 October 2019 / Revised: 27 September 2020 / Accepted: 17 October 2020 / Published online: 16 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We present a stable discontinuous Galerkin (DG) method with a perfectly matched layer (PML) for three and two space dimensional linear elastodynamics, in velocitystress formulation, subject to well-posed linear boundary conditions. First, we consider the elastodynamics equation, in a cuboidal domain, and derive an unsplit PML truncating the domain using complex coordinate stretching. The hyperbolic structure of the underlying system enables the construction of continuous energy estimates, in the time domain for the elastic wave equation, and in the Laplace space for a sequence of PML model problems, with variations in one, two and three space dimensions, respectively. They correspond to PMLs normal to boundary faces, along edges and in corners. Second, we develop a DG numerical method for the linear elastodynamics equation using physically motivated numerical flux and penalty parameters, which are compatible with all well-posed, internal and external, boundary conditions. When the PML damping vanishes in all directions, by construction, our choice of penalty parameters yield an upwind scheme and a discrete energy estimate analogous to the continuous energy estimate. Third, to ensure numerical stability of the discretization when PML damping is present, it is necessary to extend the numerical DG fluxes, and the numerical inter-element and boundary procedures, to the PML auxiliary differential equations. This is crucial for deriving discrete energy estimates analogous to the continuous energy estimates. Numerical solutions are evolved in time using the high order arbitrary derivative (ADER) time stepping scheme of the same order of accuracy with the spatial discretization. By combining the DG spatial approximation with the high order ADER time stepping scheme and the accuracy of the PML we obtain an arbitrarily high-order accurate wave propagation solver in the time domain. Numerical experiments are presented in two and three space dimensions corroborating the theoretical results.
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Keywords Elastic waves · First order systems · Perfectly Matched layer · Laplace transforms · Boundary and interface conditions · Stability · High order accuracy · Discontinuous Galerkin method Mathematics Subject Classification 35F55 · 35F46 · 65M60 · 65M70 · 65M12 · 65M15
1 Introduction Computational strategies based on the discontinuous Galerkin method (DG method) are desirable for large scale numerical simulation of wave phenomena occurring in many applications [10,18,24,32,39]. However, one of the main features of propagating wa
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