Experimental investigation of hypersonic boundary-layer stabilization on a cone by means of ultrasonically absorptive carbon-carbon material

Abstract

Hypersonic boundary-layer transition on a 7 half-angle cone using ultrasonically absorptive carbon-carbon material was investigated experimentally in the DLR High Enthalpy Shock Tunnel G�ottingen (HEG) at Mach 7.5. The cone model was tested at zero angle of attack with a nose radius of 2.5 mm and a total length of 1077 mm. One third of the model surface in circumferential direction was equipped with an in-house manufactured porous carbon-carbon material. The remaining model surface consisted of polished steel and served as reference surface. The model was equipped with co-axial thermocouples to determine the transition location by means of the surface heat flux distribution. Flush mounted piezoelectric fast-response pressure transducers were used to measure the pressure fluctuations in the boundary-layer associated with second-mode instabilities. The free-stream unit Reynolds number was varied over a range of Rem = 1.46 10^6 /m to Rem = 6.35 10^6 /m at a stagnation enthalpy of h0 = 3.2 MJ/kg and a temperature ration of Tw/T0= 0.1 . The present study revealed a signicant damping of the second-mode instabilities and an increase of the transition Reynolds number by means of an ultrasonically absorptive C/C material with random microstructure. Furthermore, the eect of small angle of attack variations on the transition location on the model was investigated.