THE MATHEMATICAL-THEORY OF THERMAL CHOKING IN NOZZLE FLOWS

The mathematical theory of sub- and supercritical nozzle flows is pres ented by a unified description of integro-algebraic and differential f ormulations of the flow equations. The critical amount of heat necessa ry for a thermally choked flow is defined and models which approximate this critical amount of heat are constructed for nozzle flows with bo th given internal heat source distributions and nonequilibrium condens ation. In particular a cubic equation for an estimate of the limiting condensate mass fraction for shock free condensing flows is derived an d a criterion for the existence of supercritical condensing flows base d on this estimate is established. The necessary and sufficient condit ions for thermal choking are then stated. It is shown that the commonl y accepted view, which asserts that the flow Mach number reaches unity at thermal choking (known to be not always true in condensing flows), only exhibits a necessary condition for a thermally choked flow.