High Temperature Rarefied Hypersonic Flow Over a Flat Plate

Abstract

Aerodynamic investigations were conducted on the flow over a flat plate with a sharp leading edge in a hypersonic shock tunnel . The flow Mach number ranged from 7.95 to 25.1 with stagnation temperatures of approximately 2300 and 7000 R. For these flow conditions, the static pressure in the test section varied from 3.2 n to 0.95 m m of mercury and the Knudsen number, based on the ratio of the free stream mean free path and the leading edge thickness, varied from approximately 0.4 to 86. Schlieren photographs taken at these conditions indicated the presence of slip flow at the sharp leading edge, in tha t the formation of the strong shock wave and the boundary layer was delayed. The induced pressures measured on the surface of the plate indicated the existence of slip flow in the vicinity of the leading edge. The slip flow region increased with the free stream flow Mach and Knudsen numbers. In the strong shock wave-boundary layer interaction region near the leading edge, the viscous region extended from the plate surface to the shock wave, and there was no apparent inviscid region between the shock wave and the boundary layer. The induced pressure on the surface of the flat plate varied inversely as the square root of the distance from the leading edge for all cases except at the highest Mach number of 25.1. At this Mach number, the maximum induced pressure on the surface near the leading edge was 28 times the free stream static pressure. For a reflected stagnation temperature of 7000 R with real gas effects, the leading edge slip phenomenon and the shock wave-boundary layer interaction were present. The strong interaction parameter % = M i V v ^ varied from 2.5 to 756. The experimental induced pressures are compared with the insulated and noninsulated interaction theories of Li and Nagamatsu.