EFFECT OF ANGLE-OF-ATTACK ON HYPERSONIC BOUNDARY-LAYER STABILITY

An experimental investigation of the effects of angle of attack on hyp ersonic boundary-layer stability on a flared-cone model was conducted in the low-disturbance Mach-6 Nozzle-Test-Chamber Facility at NASA Lan gley Research Center, Hot-wire anemometry diagnostics were applied to identify the boundary-layer instability mechanisms that lead to transi tion, The present results show that the boundary layer becomes more st able on the windward ray and less stable on the leeward ray relative t o the zero-degree angle-of-attack case, The second-mode instability do minates the transition process at a 0-deg angle of attack; however, on the windward meridian at an angle of attack this mode was stabilized, On the leeward meridian the frequency of the dominant instability was higher than the estimated frequency of the second-mode disturbance; t hus the dominant transition mechanism may be other than a second-mode disturbance. Nonlinear effects, such as growth saturation, harmonic ge neration, and spectral broadening, were observed in the transitional a nd turbulent flow regimes.