Application of parallel implicit methods to edge-plasma numerical simulations

  • Authors:
  • T. D. Rognlien;X. Q. Xu;A. C. Hindmarsh

  • Affiliations:
  • Lawrence Livermore National Laboratory, L-630, P.O.Box 808, Livermore, California 94551;Lawrence Livermore National Laboratory, L-630, P.O.Box 808, Livermore, California 94551;Lawrence Livermore National Laboratory, L-630, P.O.Box 808, Livermore, California 94551

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2002

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Abstract

A description is given of the parallelization algorithms and results for two codes used extensively to model edge plasmas in magnetic fusion energy devices. The codes are UEDGE, which calculates two-dimensional plasma and neutral gas profiles over long equilibrium time scales, and BOUT, which calculates three-dimensional plasma turbulence using experimental or UEDGE profiles. Both codes describe the plasma behavior using fluid equations. A domain decomposition model is used for parallelization by dividing the global spatial simulation region into a set of domains. This approach allows the use of a recently developed Newton-Krylov numerical solver, PVODE. Results show nearly an order of magnitude speedup in execution time for the plasma transport equations with UEDGE when the time-dependent system is integrated to steady state. A limitation that is identified for UEDGE is the inclusion of the (unmagnetized) fluid gas equations on a highly anisotropic mesh. The speedup of BOUT scales nearly linearly up to 64 processors and gets an additional speedup factor of 3-6 by using the fully implicit Newton-Krylov solver compared to an Adams predictor corrector. The turbulent transport coefficients obtained from BOUT guide the use of anomalous transport models within UEDGE, with the eventual goal of a self-consistent coupling.