Cavity flow tones

Measurements of tones generated by flow over cavities were conducted in the ARL Penn State 12-in. water tunnel. The dependence of the frequency of cavity tones on the flow velocity and the size of the cavity opening in the streamwise direction are presented and discussed. Measurement results are given for cavity tones with and without obstructions in the boundary layer at the leading edge of the cavity and with and without air trapped in the cavity. Measured cavity wall vibration levels, unsteady pressure levels inside the cavity, and flow visualization are used to analyze generating mechanisms for shear-cavity tones and Helmholtz resonances.