Prediction and Measurement of Flow-Induced Wall-Pressure Fluctuations at Low Mach Numbers

Abstract

Flow-induced wall-pressure fluctuations, on a single panel, in a wind tunnel environment are measured and analyzed for Mach numbers between 0.06 and 0.12. The effects of two, flush-mounted microphone cap configurations on measured wall pressure spectra are investigated. A selection of semi-empirical single-point frequency spectrum models, are reviewed and compared to experimental wall-pressure spectra. The measured wall-pressure spectra are compared in dimensional and non-dimensional forms to investigate dependencies on Mach number and turbulent boundary layer scaling variables. The spectra captured with the pinhole microphone configuration are in better agreement with expected behaviour presented in the literature, compared to the grid cap configuration, but show a greater Mach number dependency when scaled with mixed inner and outer boundary layer variables. The models by Laganelli and Efimtsov are most suitable for predicting wall-pressure amplitudes over the low- and mid-frequency regimes whereas, the more recent models by Smol’yakov and Goody are most appropriate for predicting the decay rate in the overlap regime. The absence of a sizeable overlap region, caused by an under-developed logarithmic region in the boundary layer, is believed to be responsible for the disparities between measured and predicted spectra, and the Mach number dependence shown by the normalized spectra.