Publications Details

Hypersonic wind-tunnel measurements of boundary-layer pressure fluctuations

Casper, Katya M.; Beresh, Steven J.; Henfling, John F.; Spillers, Russell

During atmospheric reentry, hypersonic vehicles are subjected to high levels of boundary-layer pressure fluctuations. To improve understanding and prediction of these fluctuations, measurements of surface pressure fluctuations on a 7° sharp cone were conducted in Sandia's Hypersonic Wind Tunnel under noisy flow and in Purdue University's Boeing/AFOSR Mach-6 Quiet Tunnel under noisy and quiet flow. Fluctuations under laminar boundary layers reflected tunnel noise levels. Laminar boundary-layer measurements under quiet flow were an order of magnitude lower than under noisy flow. Transition on the model only occurred under noisy flow, and fluctuations peaked during transition. The transition location, marked by the peak, was predicted using tunnel noise parameters (Pate's correlation). Turbulent boundary-layer fluctuations were lower than transitional fluctuations and also reflected tunnel noise levels. Measurements of second-mode waves showed the waves started to grow under a laminar boundary layer, saturated, and then broke down near the peak in transitional pressure fluctuations.