Time step restrictions for Runge-Kutta discontinuous Galerkin methods on triangular grids

  • Authors:
  • Ethan J. Kubatko;Clint Dawson;Joannes J. Westerink

  • Affiliations:
  • Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, OH 43210, United States;Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712, United States;Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, United States

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2008

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Abstract

We derive CFL conditions for the linear stability of the so-called Runge-Kutta discontinuous Galerkin (RKDG) methods on triangular grids. Semidiscrete DG approximations using polynomials spaces of degree p=0,1,2, and 3 are considered and discretized in time using a number of different strong-stability-preserving (SSP) Runge-Kutta time discretization methods. Two structured triangular grid configurations are analyzed for wave propagation in different directions. Approximate relations between the two-dimensional CFL conditions derived here and previously established one-dimensional conditions can be observed after defining an appropriate triangular grid parameter h and a constant that is dependent on the polynomial degree p of the DG spatial approximation. Numerical results verify the CFL conditions that are obtained, and ''optimal'', in terms of computational efficiency, two-dimensional RKDG methods of a given order are identified.