Effects of leading edge serrations on noise reduction and aerodynamic performance of multi-copter rotors during forward flight

Inspired by the silent flight of owl wings, leading edge (LE) serrations are adopted for noise reduction of multi-copter rotors. By choosing different parameters of serrations, i.e. height and wavelength, aerodynamic and aeroacoustic performance of isolated multi-copter rotors are analyzed at the forward flight condition. Rotors with add-on LE serrations generate lower thrust than the Baseline (BL) rotor at the same rotational speed. In order to investigate the noise reduction of different designs from the application perspective, comparison of rotor noise emission is conducted at the same thrust. All serrated rotors considered in this study show lower broadband noise and Overall Sound Pressure Level (OASPL) than the BL rotor. It has been observed that the noise reduction generally increases with increasing frequency in the mid-high frequency. In addition, the directivity of the rotor noise reduction is also shown using a circular microphone array.