Publications Details

Unsteady pressure sensitive paint measurements of resonance properties in complex cavities

Casper, Katya M.; Wagner, Justin W.; Beresh, Steven J.; Spillers, Russell W.; Henfling, John F.

In previous studies, complex cavity geometries showed higher amplitude and more three- dimensional pressure fields than simple rectangular cavities. However, those studies relied on twenty point measurements within the cavity. To further understand the development of the pressure field within complex bays, high-frequency pressure-sensitive paint (PSP) was applied to the floor of an L/D = 7 complex cavity at Mach 0.9; unsteady pressure measurements were obtained at 10 kHz. Power spectra of the PSP measurements have a spatial distribution at each cavity resonance frequency with an oscillatory pattern; additional maxima and minima appear as the mode number is increased. This behavior was tied to the superposition of a downstream propagating shear-layer disturbance and an upstream propagating acoustic wave of different amplitudes, consistent with the classical Rossiter model. Complex geometries added spanwise asymmetries to the spatial pattern and amplified specific modes. These spatially dependent features of the pressure field might be missed by point measurements of the pressure field.