Response of a plate with piezoelectric elements to turbulent pressure fluctuation in supersonic flow

The aeroelastic response of a plate with supersonic freestream flow on one side and a shallow cavity on the other to turbulent pressure fluctuations is investigated computationally and experimentally. An empirical model is developed for the pressure fluctuations in a turbulent boundary layer that accounts for spatial and spectral variations in the pressure field. Supersonic wind tunnel tests were conducted in a Mach 2.5 flow with and without an impinging shock at the plate surface. In both cases the boundary layer was turbulent. The impinging shock creates shock-wave boundary-layer interaction, which alters the characteristics of the pressure fluctuations. Pressure-sensitive paint was used to measure the unsteady pressure on the surface of a rigid plate and characterize the pressure field (local mean, rms, and the spatial coherence length) and piezoelectric patches were used as sensors to measure the response of an elastic plate. The extracted pressure parameters were used to simulate the fluid–structure response and correlate with experiments. The computed pressure perturbation due to plate motion is found to be small relative to the natural pressure fluctuation for the fluid/structural configuration studied. Computed and measured power spectra of the piezoelectric element voltage show good agreement over a wide range of structural natural frequencies. Aeroelastic response sensitivity to pressure fluctuation coherence length was also investigated computationally. It is found that with small fluid elements, which represent small-scale uncorrelated noise, the structural response is relatively small because the excitation is filtered by the plate dynamics. Experimental results suggest that the effective excitation spatial scale is on the order of the boundary layer thickness.