Efficient discontinuous Galerkin implementations and preconditioners for implicit unsteady compressible flow simulations
Abstract
This work presents and compares efficient implementations of high-order discontinuous Galerkin methods: a modal matrix-free discontinuous Galerkin (DG) method, a hybridizable discontinuous Galerkin (HDG) method, and a primal formulation of HDG, applied to the implicit solution of unsteady compressible flows. The matrix-free implementation allows for a reduction of the memory footprint of the solver when dealing with implicit time-accurate discretizations. HDG reduces the number of globally-coupled degrees of freedom relative to DG, at high order, by statically condensing element-interior degrees of freedom from the system in favor of face unknowns. The primal formulation further reduces the element-interior degrees of freedom by eliminating the gradient as a separate unknown. This paper introduces a -multigrid preconditioner implementation for these discretizations and presents results for various flow problems. Benefits of the -multigrid strategy relative to simpler, less expensive, preconditioners are observed for stiff systems, such as those arising from low-Mach number flows at high-order approximation. The -multigrid preconditioner also shows excellent scalability for parallel computations. Additional savings in both speed and memory occur with a matrix-free/reduced version of the preconditioner.
Cite
@article{arxiv.1812.04789,
title = {Efficient discontinuous Galerkin implementations and preconditioners for implicit unsteady compressible flow simulations},
author = {Matteo Franciolini and Krzysztof Fidkowski and Andrea Crivellini},
journal= {arXiv preprint arXiv:1812.04789},
year = {2018}
}