Investigations of Cavity Noise Generation on a Cylinder

Abstract

Cavity noise generation is of particular interest for e.g. the aeronautical and automotive industry where a lot of different shaped cavities occur on curved surfaces. In this work the flow over a small rectangular cavity (L/D ≈ 1) on a cylinder at velocity ramps up to 45 m/s was investigated in an acoustic wind tunnel. Acoustical and PIV measurements indicate a sudden transition of the circulating flow to a turbulent boundary layer at the typical Reynolds number leading to cavity noise. The onset of the acoustic radiation is contemporaneous with this transition and shows a strong hysteresis. Pressure measurements directly on the cylinder surface reveal a hydrodynamics and acoustics coupling point in front of the cavity.