Secondary Instabilities of Hypersonic Stationary Crossflow Waves

An experiment investigating the nonlinear breakdown of hypersonic stationary crossflow waves has been conducted in a Mach 6 quiet tunnel. Secondary instabilities of the stationary waves were measured on a sharp, 7 deg half-angle cone at a 6 deg angle of attack, from 110 to 160 deg from the windward ray. A secondary instability was measured as it grew over a range of amplitudes until the onset of turbulence. The initial linear growth rate of the secondary instability was about 50 m(-1), with a peak growth before breakdown of about e(3.8) from the sensor noise floor. At least two frequency bands of the secondary instability appeared to exist concurrently, with each spatially confined within a region of the stationary vortex. The instability wave speeds and frequencies were measured at several azimuthal locations. The wave group velocities were near the edge velocity, regardless of azimuthal location. The instability frequencies were between 140 and 300 kHz, and they generally decreased with the increasing azimuthal angle from the windward ray.