An experimental and numerical investigation of sound produced by low-speed flow over a cavity with a leading edge overhang

An experimental and numerical investigation is conducted on low-speed flow over a cavity. The production of discrete tones and development of complex flow structures are studied for deep cavities with leading edge overhangs. Experimental results indicate that multiple discrete frequency tones are produced simultaneously or intermittently. The frequency characteristics and maximum sound pressure level depend on the leading edge overhang geometry. The onset of instability and production of multiple tones appear to be affected by boundary layer thickness. Numerical studies show a complex periodic vortex structure in the cavity mouth region, with a period equal to that measured for the dominant tone in the experiments. The vortex structure is affected by the leading edge overhang geometry. Mass addition and extraction from the cavity appear to be controlled by the vortex structure in the cavity mouth, which may explain the effect of lip geometry on peak sound pressure levels in the cavity.