EDGE-LOCALIZED MODE SIMULATIONS IN DIVERTOR TOKAMAKS

The three-dimensional nonlinear evolution of moderate wavelength press ure-driven edge-localized instabilities is calculated in divertor toka maks. The evolution consists of several stages: linear growth, nonline ar saturation and turbulence, shear flow generation, pressure outflow to the outboard divertor, and finally, outflow to the inboard divertor . The shear how generation appears to be an important factor in transp orting pressure perturbations to the inboard side, and in causing pres sure loss to the inboard divertor. The physical model consists of diss ipative compressional reduced magnetohydrodynamics which includes the important effect of sound wave propagation. A novel numerical discreti zation, using a poloidal unstructured mesh and a staggered toroidal me sh, has been implemented on a parallel, distributed memory computer. N onlinear, three-dimensional numerical computations include a separatri x X-point in the computational domain. (C) 1996 American Institute of Physics.