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Analysis of Numerical Simulation Database for Acoustic Radiation from High-Speed Turbulent Boundary Layers

Direct numerical simulations (DNS) of Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Reτ ≈ 460 are conducted at two wall temperatures (Tw/Tr = 0.25, 0.76) to investigate the generated pressure fluctuations and their dependence on wall temperature. It is shown that the mean flow predictions and computed frequency spectrum of wall-pressure fluctuations are in good agreement with the measurements in the Boeing/AFOSR Mach 6 Quiet Tunnel at Purdue University. Simulations indicate that the influence of wall temperature on pressure fluctuations is largely limited to the near-wall region, with the characteristics of wall-pressure fluctuations showing a strong temperature dependence. Wall temperature has little influence on the propagation speed of the freestream pressure signal. The freestream radiation intensity compares well between wall-temperature cases when normalized by the local wall shear; the propagation speed of the freestream pressure signal and the orientation of the radiation wave front show little dependence on the wall temperature.