An experimental investigation of wall pressure fluctuations beneath nonequilibrium turbulent flows

Abstract

Abstract : Wall pressure fluctuations beneath a non-equilibrium turbulent boundary layer were studied experimentally. The objective of the investigation was to better understand the process by which turbulent boundary layers flows produce wall pressure fluctuations. The approach was to study the statistics of both the wall pressure field and velocity field for a non-equilibrium turbulent boundary layers, produced by passing a flow over a backward-facing step, and then to identify turbulent structures in the flow that contribute to the source terms of the wall pressure field. Detailed velocity and wall pressure measurements were also obtained for an equilibrium flow to provide a basis of comparison for the perturbed flow results. The wall pressure statistics for the perturbed flow are characterized by the presence of the disturbance layers variables. Hence, the source of the low frequency excess in the wall pressure fluctuations is the disturbance layer. The high frequency wall pressures were found to scale on inner variables, and as such, recovered to an equilibrium flow condition quite rapidly. This places the perturbed source of high frequency wall pressures in the inner layer of the boundary layer.