Accelerating the solution of a physics model inside a tokamak using the (Inverse) Column Updating Method

• R. Haelterman ^[1] ; D. Van Eester ^[2] ; D. Verleyen ^[1]
  1. [1] Royal Military Academy

     Royal Military Academy

     Arrondissement Brussel-Hoofdstad, Bélgica

     
  2. [2] Laboratorium voor Plasmafysica - Laboratoire de Physique des Plasmas, Association “EURATOM - Belgian State”, Trilateral Euregio Cluster (Belgium)
• Localización: Journal of computational and applied mathematics, ISSN 0377-0427, Vol. 279, Nº 1 ((1 May 2015)), 2015, págs. 133-144
• Idioma: inglés
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• Resumen

  • Many physics problems can only be studied by coupling various numerical codes, each modeling a subaspect of the physics problem that is addressed. In most cases, the “brute force” technique of running the codes one after the other in a loop until convergence is reached requires excessive CPU time. The present paper illustrates that re-writing the coupling as a root-finding problem, to which a quasi-Newton method–here the (Inverse) Column Updating Method–can be applied, is useful to push down the computation time, at the expense of a very modest amount of supplementary programming. A simplified version of the set of codes commonly used to describe plasma heating by radio frequency waves in a tokamak plasma is adopted for illustrating the potential of the speed-up method. It consists of a wave equation as well as a Fokker–Planck velocity space diffusion and a radial energy diffusion model. It is shown that with this approach a substantial reduction in CPU time needed for convergence can be obtained.