Contributions of turbulence to subsonic cavity flow wall pressures

Poisson-type pressure sources in the flow over open cavities were examined for several subsonic free stream conditions. Wall-mounted pressure transducers and two-component particle image-velocimetry (Ply) were employed synchronously to obtain data at Mach 0.19, 0.29, 0.39, 0.58, and 0.73 for a rectangular cavity with a length-to-depth ratio of 6. The modified quadratic stochastic estimation was used to yield a time-resolved, low-dimensional representation of the velocity field using the PIV and pressure measurements. A conformal transformation was applied to the cavity geometry to allow the integration of Poisson's equation giving a time-resolved estimate of the surface pressure fluctuations. The use of Poisson's equation allowed the contribution of the mean-shear and nonlinear velocity sources of the surface pressure loads to be evaluated independently, showing that the resonant features of the cavity flow (Rossiter modes) are dominant in the mean-shear contribution and that nonlinear interactions become increasingly significant above Mach 0.4. (c) 2011 American Institute of Physics. [doi:10.1063/1.3540682]