Flat Plate Turbulent Boundary Layers Subject to Large Pressure Fluctuations

In transonic wind tunnel experiments in which the roof of the test section served as the model boundary layer, the influence of pressure fluctuations on attached subsonic and transonic turbulent boundary layers in the presence of small pressure gradients was investigated. Momentum thickness Reynolds number varied between 3000 and 16,000 and the pressure fluctuation level varied between 0.003 and 0.026. A small influence of pressure fluctuations on the boundary layer shape factor H and on the skin friction coefficient was noted. An increase in pressure fluctuation level from 0.0055 to 0.0226 produced a significant increase in the velocity and density fluctuations in the boundary layer.