K-EPSILON COMPRESSIBLE 3D NEUTRAL FLUID TURBULENCE MODELING OF THE EFFECT OF TOROIDAL CAVITIES ON FLAME-FRONT PROPAGATION IN THE GAS-BLANKET REGIME FOR TOKAMAK DIVERTORS

Recent experiments and 2D laminar plasma-fluid simulations have indica ted that plasma. detachment from the divertor plate is strongly tied t o plasma recombination. With plasma recombination, a neutral gas blank et, will form between the divertor plate and the plasma frame front. B ecause of plasma-neutral coupling, the plasma flow along the field lin es will drive neutral gas flow with Mach number greater than or equal to 1 and Reynolds number greater than or equal to 1000. A compressible set of conservation and transport equations are solved with 2D mean t oroidal flow and 3D turbulence effects over various toroidal cavity ge ometries. The radial structure of the temperature profile is determine d for both turbulent and laminar flow as the flame front propagates do wn the toroidal cavity. Quantitative results are obtained for the incr eased heat, transfer to the toroidal walls due to turbulence as well a s radial profiles for the transport coefficients. It is found that, he at loads to the toroidal walls can be increased by factors of 5-20 ove r that for laminar flow for the cavity geometries studied here. This i ncreased heat transfer to the toroidal walls will lead to decreased le vels of heat flux impinging on the divertor plate.