Hypersonic wind-tunnel measurements of boundary-layer pressure fluctuations
Abstract
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 seven-degree sharp cone at zero angle of attack 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, depended on tunnel noise parameters. 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. A physics-based model of transitional fluctuations is sought by relating them to the development and growth of turbulent spots. Hot-film traces indicated the possible presence of turbulent spots. The kurtosis and skewness also peaked during transition, indicating impulsiveness of the flow. However, turbulent spots could not be easily identified in the pressure traces. More work is needed to characterize the pressure fluctuations in the transition region.
Degree
M.S.A.A.
Advisors
Schneider, Purdue University.
Subject Area
Aerospace engineering
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