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.