LDV Measurements of the Unsteady Shear Layer Above a Resonant Cavity

Flow past a wall mounted cavity can excite strong acoustic resonance in the cavity. The acoustic field in the cavity is coupled to the unstable shear layer at the mouth of the cavity. Flow visualization revealed that the flow in the shear layer is characterized by periodic formation of large-scale vortices and convection of these vortices downstream to the trailing edge. A LDV system was utilized to measure the periodic changes in the shear layer flow. A two step data analysis process was used to reconstruct the velocity field. The process consisted of phase conditioned averaging and a Fourier series approximation