An Efficient Time-Domain Perfectly Matched Layers Formulation for Elastodynamics on Spherical Domains

Many practical applications require the analysis of elastic wave propagation in a homogeneous isotropic media in an unbounded domain. One widely used approach for truncating the infinite domain is the socalled method of Perfectly Matched Layers (PMLs). Most existing PML formulations are developed for finite difference methods based on the first-order velocity-stress form of the elastic equations and they are not straight-forward to implement using standard finite element methods on unstructured meshes. Some of the problems with these formulations include the application of boundary conditions in half-space problems and in the treatment of edges and/or corners for time-domain problems. Several PML formulations which do work with finite element methods have been proposed, although most of them still have some of these problems and/or they require a large number of auxiliary nodal history/memory variables. In this work we develop a new PML formulation for time-domain elastodynamics on a spherical domain, which reduces to a two-dimensional formulation under the assumption of axisymmetry. Our formulation is well-suited for implementation using finite element methods, where it requires lower memory than existing formulations and it allows for natural application of boundary conditions. We solve example problems on twoand three-dimensional domains using a high-order discontinuous Galerkin discretization on unstructured meshes and explicit time-stepping. We also study an approach for stabilization of the discrete equations and we show several practical applications for quality factor predictions of micromechanical resonators along with verifying the accuracy and versatility of our formulation. Copyright c © 0000 John Wiley & Sons, Ltd.