AN IMPROVED CONVECTION SCHEME APPLIED TO RECOMBINING DIVERTOR PLASMA FLOWS

A high-order finite volume convection scheme, in conjunction with a mo notonicity preserving flux-limiter is applied to a combined tokamak ed ge plasma/Navier-Stokes neutral transport model. This is a highly nonl inear system of convection-diffusion-reaction equations which describe the partially ionized boundary layer plasma of a tokamak fusion react or. The solutions of interest contain a sharp ionization front. The im proved convective discretization is applied within the context of the existing matrix-free Newton-Krylov solution algorithm. More accurate c onvective differencing is shown to make a significant difference on a problem of current interest. It is demonstrated that a matrix-free New ton-Krylov implementation, where the preconditioner is derived using f irst-order upwind convective differencing, provides savings in both me mory requirements and CPU time. (C) 1998 Academic Press.