Calculating Surface Pressure Fluctuations From PIV Data Using Poisson's Equation

Subsonic flow at Mach 0.19, 0.29, 0.39, 0.58 & 0.73 over a shallow, open cavity with a length-to-depth ratio of 6 was measured using wall-mounted pressure transducers and two-component particle image velocimetry (PIV). Next, the modified Quadratic Stochastic Estimation (mQSE) was used to yield time-resolved velocity data from the PIV and pressure measurements. Finally, a formulation of Poisson’s equation was applied to the estimated velocity field to yield a time-resolved estimate of the surface pressure fluctuations. The use of Poisson’s equation allowed the contribution of the mean-shear and non-linear velocity sources of the surface pressure loads to be evaluated independently. The study reveals that the resonant features of the cavity flow (Rossiter modes) are associated with the mean-shear sources in the shear layer and not with the non-linear sources.

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