HIGH ENTHALPY NOZZLE-FLOW SENSITIVITY STUDY AND EFFECTS ON HEAT-TRANSFER

The sensitivity of the flow along the nozzle and in the test section o f high enthalpy wind tunnels to the thermochemical response of the noz zle expansion process, as well as effects on the pressure and heat tra nsfer distributions over the Electre blunt cone standard test model, a re examined in the framework of properly characterizing the test secti on flow field in such facilities. Particularly sensitive to the thermo chemical behaviour of the nozzle Bow, in the facilities under consider ation, are the static pressure, static temperature and Mach number, wh ereas stagnation point (pitot) pressure and heat transfer data or free stream velocity are inadequate for the characterization of the thermoc hemical state of the flow. The Electre and nozzle wall pressure data i n the F4 are jet wind tunnel suggest, in contrast to nonequilibrium co mputations, that the flow in the F4 nozzle is close to equilibrium. In the KEG and, to some extent, the T5 piston-driven shock tunnels, ther e are indications that significant heat losses occur in the reservoir. Lastly, sim pie semi-empirical formulations for stagnation point heat ing are shown to perform reasonably well in high enthalpy flow conditi ons.