LOW-DENSITY STAGNATION-POINT HEAT TRANSFER IN HYPERSONIC AIR FLOW

Stagnation-point heat transfer to two- and three-dimensional bodies at low Reynolds numbers was studied to obtain hypersonic low-density data and to demonstrate the suitability of the hypersonic shock tunnel as a facility for research in rarefied gasdynamics. Low-density experiments on a transverse cylinder and a hemisphere cylinder were made in air at Mach numbers from 8.4 to 11.6 in the CAL 11- by 15-inch hypersonic shock tunnel. The stagnation pressure and temperature, as well as model diameter, were varied to obtain a range of Reynolds numbers from 11 to 1000, based on flow conditions behind the bow shock wave and model radius. The experimental heat-transfer rates are presented and compared with theoretical predictions. The data obtained with the transverse cylinders are in good agreement with continuum boundary-layer theory at all but the lowest Reynolds numbers and highest Knudsen numbers. The hemisphere-cylinder data indicated the presence of a significant vorticity-interaction effect. Good agreement with the theoretical analysis of H.K. Cheng accounting for this effect is indicated.