Influence of self-oscillating trailing edge flaplets on turbulent boundary layer - Trailing edge noise

Abstract

The aeroacoustics of a tripped NACA0012 aerofoil with an array of self-oscillating flexible flaplets attached to the trailing edge at low to moderate Reynolds number and at geometric angles of attack ag = 0? - 20? is investigated. A low frequency noise reduction occurs at a chord based Strouhal number of 2 - 3 across all Reynolds number and angles of attack. With maximum reductions reaching up to 8 dB within the Strouhal number range. This reduction is proposed to be due to a modification of the instabilities in the shear layer by the self-oscillating flaplets. A slight increase in noise level is seen at higher frequencies, however once the overall sound pressure level is calculated there is still a net overall reduction.