Aeroacoustic and aerodynamic investigation of multicopter rotors with serrated trailing edges

Multicopters can be observed in many applications, e.g. video taking, mapping, construction, delivery, and rescue operations. In some circumstances, aerodynamic noise of multicopters is a significant concern and quiet rotors would be more competitive in the market. Inspired by owl wings and research of serrations on two-dimensional airfoils, trailing edge serrations are adopted for noise reduction of three-dimensional multicopter rotors. By choosing different parameters of serrations, i.e. height to wave-length ratio ( ) and retrofitted manner of add-on and cut-in, noise reduction and aerodynamic performance of different rotors are compared at forward flight conditions. The add-on serration rotors generate higher thrust than cut-in serration ones for the same rotation speed. The serration parameter of performs the best among different designs in terms of overall sound pressure level decrease at the same thrust. Broadband noise decrease in the middle to high frequency range is observed for all designs, but it is less significant in comparison with rotor tonal noise, and the rotor noise decrease is mainly a result of the improved aerodynamic performance.
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