Outer-flow effects on turbulent boundary layer wall pressure fluctuations

The outer-flow contribution to the pressure fluctuations occurring at the wall beneath a turbulent boundary layer was studied experimentally. A moving wall wind-tunnel facility was developed for the work. A flat test plate was suspended at various heights over the movable tunnel wall such that interacting and noninteracting turbulent boundary layers were developed in the resultant channel. Mean and fluctuating velocity components were measured for cases with and without wall motion. Pressure fluctuations were measured, with pinhole microphones on the surface of the test plate forming the upper- channel boundary, at corresponding test conditions. The data show that the wall-pressure fluctuations are relatively insensitive to the details of the outer flow, even over the range of frequencies dominated by outer-flow turbulence structures.