An Improved Convection Scheme Applied to Recombining Divertor Plasma Flows

A high-order finite volume convection scheme, in conjunction with a monotonicity preserving flux-limiter is applied to a combined tokamak edge plasma/Navier?Stokes neutral transport model. This is a highly nonlinear system of convection?diffusion?reaction equations which describe the partially ionized boundary layer plasma of a tokamak fusion reactor. The solutions of interest contain a sharp ionization front. The improved convective discretization is applied within the context of the existing matrix-free Newton?Krylov solution algorithm. More accurate convective differencing is shown to make a significant difference on a problem of current interest. It is demonstrated that a matrix-free Newton?Krylov implementation, where the preconditioner is derived using first-order upwind convective differencing, provides savings in both memory requirements and CPU time.

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