LAUSR

A controlled, laser-generated perturbation was created in the freestream of the Boeing/U.S. Air Force Office of Scientific Research Mach 6 Quiet Tunnel. The freestream perturbation convected downstream in the wind tunnel to interact with a flared cone model. The model is a body of revolution bounded by a circular arc with a 3.0 m radius. Two different nose tips were used in this experiment: a 1.0 mm nose tip and a 0.16 mm nose tip. Fourteen fast pressure transducers were used to measure a wave packet generated in the cone boundary layer by the freestream perturbation. This wave packet grew large and became nonlinear before experiencing natural transition in quiet flow. Breakdown of this wave packet occurred when the amplitude of the pressure fluctuations at the most unstable second-mode frequency was approximately 10% of the surface pressure for a nominally sharp nose tip. The amplitude of the second-mode instability at the neutral point on the flared cone is estimated to be on the order of 10−7 times the...