Simultaneous Infrared And Pressure Measurements Of Crossflow Instability Modes For HIFiRE 5 (POSTPRINT)

A 2:1 elliptic cone model was tested in a Mach-6 quiet wind tunnel with both low and elevated freestream noise levels. Simultaneous measurements were made using an infrared camera and 22 pressure sensors mounted flush with the model surface. Infrared measurements confirmed the presence of stationary crossflow vortices in quiet flow. This is the first time infrared imaging has identified stationary crossflow vortices in a quiet wind tunnel. Power spectral densities of the signals from the pressure transducers also revealed the presence of traveling crossflow waves much farther upstream than had previously been measured. Stationary crossflow wavelengths and traveling crossflow wave properties matched those measured on a previous model of the same geometry. Neither stationary nor traveling crossflow vortices were observed in noisy flow, even though the boundary layer was seen to transition from laminar to turbulent as the freestream Reynolds number was increased. The primary transition mechanism in noisy flow is unknown.