Pressure spectra of hypersonic boundary layers on a cone at angle of attack*

The scaling of turbulent pressure spectra for Kulite sensor data collected at Mach 5 and Mach 8 in the Sandia hypersonic wind tunnel facility on the surface of a smooth seven-degree half-angle cone at angle of attack is explored. Data was collected on the windward, yaw, and leeward sides of the cone for angles of attack in the range of zero to ten degrees. In addition, temperature-sensitive paint measurements were performed to verify turbulence conditions and oil-flow visualization to capture the changing streamlines with angle of attack. Companion low-fidelity simulations at matched conditions to the experiments were also performed to obtain scaling quantities for the pressure spectra. Outer scaling of the spectra highlights the increase in the rms pressure fluctuations on the windward side, decrease on the leeward side, and constant behavior on the yaw side with increasing angle of attack. On the windward side, the spectra are seen to incline from a “universal” power law scaling of ω^-1 to ω^-7/3 and lower than expected frequencies. This is consistent with strong dissipation on the windward side, but the shift in the spectrum requires further investigation. Implications for pressure spectra modeling in hypersonic boundary layers will be discussed.