ECCOMAS 2024

A Riemann-solver-free Spacetime Discontinuous Galerkin Cell Vertex Scheme for General Conservation Laws

  • Tu, Shuang (Jackson State University)
  • Pang, Qing (Jackson State University)
  • Jiang, Chao (Jackson State University)

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This talk presents a Riemann-solver-free spacetime discontinuous Galerkin method developed for general conservation laws. The method integrates the best features of the spacetime Conservation Element/Solution Element (CE/SE) method and the discontinuous Galerkin (DG) method. The core idea is to construct a staggered spacetime mesh through alternate cell-centered CEs and vertex-centered CEs within each time step. Inside each SE, the solution is approximated using high-order spacetime DG basis polynomials. The spacetime flux conservation is enforced inside each CE using the DG concept. The unknowns are stored at both vertices and cell centroids of the spatial mesh. However, the solutions at vertices and cell centroids are updated at different time levels within each time step in an alternate fashion. The alternate solution updating at cells and vertices gives the method the name as DG Cell-Vertex Scheme (DG-CVS). Thanks to the staggered spacetime formulation, there is no left and right states for the solution at the spacetime interface. Instead, the solution available to evaluate the flux is continuous across the interface. Therefore, no (approximate) Riemann solvers are needed to provide a unique numerical flux. The current method can be used to solve arbitrary conservation laws including the compressible Euler equations, shallow water equations and magnetohydrodynamics (MHD) equations without the need of any form of Riemann solvers. In addition, the diffusive fluxes can be handled in similar way without the need of special treatment as required by other DG methods. A set of benchmark problems of various conservation laws will be presented to demonstrate the accuracy and effectiveness of the method.