Enhancing the noise reduction capability of the trailing edge serration at incidence using serration extension

Abstract

This paper presents an experimental study to enhance the noise reduction capability of the trailing edge serration by shifting the serration root downstream of the trailing edge. The distance between the serration root and the trailing edge is referred to as extension length in this study. Three different extension lengths of 5 mm, 10 mm, and 15 mm are employed. Experiments were performed on a 100 mm chord NACA 0012 wing model with sawtooth trailing edge serration. The acoustic beamforming was performed for various angles of attack and flow speeds between 20 m/s and 50 m/s corresponding to chord-based Reynolds number of 1.4 × 10^5 and 3.5 × 10^5 respectively. Results show that the extension can improve the noise reduction capability of the trailing edge serration, especially for the flapped serration it can reduce the broadband noise by up to 15 dB at 8.5 deg. angle of attack. To understand the observed noise reduction, we employ the particle image velocimetry measurements of the wall-normal plane along the serration root. With extension a gradual reduction in the turbulent kinetic energy is observed for the flapped serration. Overall, the serration extension proves to be effective in reducing the trailing edge noise without aerodynamic penalty.