Influences of Near-Wall and Induced Irrotational Motion in a Turbulent Boundary Layer on Wall Pressure Fluctuations

While many studies have investigated the influence of flow structure in a turbulent boundary layer on the wall pressure signature, the conclusions of these studies have often been limited due to their reliance on a single observation. These single observations include investigations using one signal processing method over a range of locations, or a variety of signal processing techniques at a single location in the boundary layer. Hence, the conclusions often include conjecture on the impact of the flow structure at other physical locations, as well as predictions on the observable effect of flow structure should the turbulence be examined with a different signal processing perspective. In the current study, experimental data of simultaneous wall pressure and velocity fluctuations across the boundary layer have been obtained in a low-noise flow facility. These data have been examined using a variety of signal processing techniques, including probability distributions and spectral analysis. The distinct features of the Reynolds stress within the boundary layer and the observed irrotational motion at the outer edge of the boundary layer were evident in the results from each signal processing method. The influence of these two flow patterns on the wall pressure spectrum was identified and support conjectures made on the correlation between turbulence source locations and frequency bands in the wall pressure spectrum. The investigation demonstrates the necessity and utility of multiple perspectives over a range of spatial locations to study turbulence.