Experimental investigation of boundary layer instabilities and transition on sharp and blunt cones in Oxford’s High-Density Tunnel

Boundary layer instabilities and transition to turbulence on a 7-degree half-angle cone with varying nose-tip radii in Mach 6 and 7 flow are investigated using a combination of surface heat transfer measurements, surface pressure measurements, and high speed schlieren images. The experiments are performed at unit-Reynolds numbers ranging from [22-44]*10^6/m in University of Oxford’s High-Density Tunnel (HDT). The transition Reynolds number, Re_{X_T}, increases with increasing nose tip Reynolds number, Re_{R_N}, for Re_{R_N}<10^5. In this range, evidence of second-mode wave instabilities are observed in both schlieren images and surface pressure measurements. For 10^5