Flat plate self-noise reduction at low-to-moderate Reynolds number with trailing edge serrations

Abstract

This paper explores the noise reduction potential of sawtooth trailing edge serrations on a flat plate at low-to moderate Reynolds number. The noise radiated by a flat plate with both sharp and serrated trailing edges has been measured in an anechoic wind tunnel at the University of Adelaide. The noise measurements have been taken at a range of flow speeds (Reynolds numbers of Rec < 4.5 × 105, based on chord) for two different sawtooth geometries. Trailing edge serrations are found to achieve an average attenuation of up to 7 dB over a large frequency range. The measured noise reductions show a linear dependence on Strouhal number, St = fδ/U∞, where f is the frequency, δ is the boundary layer thickness and U∞ is the free stream velocity. The results of this study are compared with theoretical noise reduction predictions showing that significant differences exist between measurements and theory.