Cross-Flow Instability Experiments on a Swept Fin-Cone with Variable Nose Bluntness in Mach 6 Flow

An experiment has been designed and executed by the author with the support of a University of Notre Dame based research group to study boundary layer transition over a 7° half-angle right circular cone coupled to a 70° swept fin in Mach 6 flow. Particular interest was given to the swept fin portion of the model which creates a boundary layer conducive to the crossflow instability. Infrared thermography was used to assess surface heating caused by stationary boundary layer disturbances. Pressure transducers were embedded in the surface of the fin to capture non-stationary boundary layer disturbance. The model was tested over a range of Reynolds numbers and cone nose tip bluntness. Strong evidence of the stationary crossflow instability was found at the highest tested Reynolds number with the most blunt nose tip applied. Discrete roughness elements were then used to delay the onset of boundary layer transition by forcing a less amplified stationary mode. Pressure sensors were able to pick up on non-stationary boundary layer disturbances of several frequencies. A 117 kHz disturbance was found to have characteristics consistent with the travelling crossflow instability. Finally these experiments were conducted concurrently with computations performed by the Computational Stability and Transition (CST) lab at Texas A&M University and comparisons were made between experimental and computational results.