Surface-Pressure Fluctuations from Separated Flow over an Axisymmetric Bump

Surf'zice-pressure fluctuations are measured (or the separated flow over a smoothly contoured axisymmet ric hump or hill with an approaching two-dimensional turbulent boundary-layer thickness that is half of the bump height and momentum thickness Reynolds number Reo = 7,300. Two piezoresislive pressure transducers were used to measure the pressure fluctuations and to remove the noise by the subtraction method. The flow over this bump shows highly unsteady saddle-focus separations on the leeside curved surface. The magnitude of surface-pressure fluctuations is higher on the leeside than the windward side. The power spectral levels of pressure fluctuations are high in the lowfrequency region, and they contribute dominantly to the resulting surface-pressure fluctuation on the leeside. In the separated region. large-scaled eddy structures associated with the streamwise vortices emanated front threedimensional separations are major sources for the pressure fluctuation generation, and the rapid spectral decay is observed. From the approximate analysis, the asymmetric negative skewed histogram of sUrface-pressure fluctuations appears in the separated region.