Outer-flow effects on turbulent boundary layer wall pressure fluctuations

The outer-flow contribution to the pressure fluctuations occurring at the w all beneath a turbulent boundary layer was studied experimentally. A moving wall wind-tunnel facility was developed for the work. A flat test plate wa s suspended at various heights over the movable tunnel wall such that inter acting and noninteracting turbulent boundary layers were developed in the r esultant channel. Mean and fluctuating velocity components were measured fo r 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 th e outer flow, even over the range of frequencies dominated by outer-flow tu rbulence structures. (C) 1999 Acoustical Society of America. [S0001-4966(99 )02904-5].