Aerofoil tones produced by a streamlined plate with cavity

Abstract

A streamlined plate containing a rectangular cavity on one side was found to produce aerofoil tones. In the considered chord-based Reynolds number range of 1.0 X 105 to 1.8 x 105, cavity oscillation modes did not occur due to insufficient cavity length (being 5% of chord). The discrete tonal frequencies showed good collapse with a U0.085 scaling, suggesting that the tonal mechanism behaves similarly to that reported for smooth aerofoils. In this instance, the results suggest that an aeroacoustic feedback loop exists between the aerofoil trailing edge, where the noise is thought to be generated, and a highly receptive point in the boundary layer located at the cavity trailing edge. A region of separation near the aerofoil trailing edge is also believed to play a role in the amplification of the tones.