Aerodynamic and aeroacoustic characteristics of a multicopter propeller during forward flight

During the forward flight of multicopters, the propeller has an inclination angle and the inflow of the propeller is not axisymmetric. The propeller experiences cyclic loading, which may have an impact on the vibration, structural fatigue, and additional noise generation of the propeller. In order to quantify the aerodynamic and aeroacoustic features of the propeller during the forward flight, i.e. a typical condition of flight speed of 20 m/s and inclination angle of 10°, numerical simulations and experimental measurements on an isolated propeller are conducted. Results of the time-averaged loading, dynamic loading, flow structures, and aerodynamic noise of the propeller are presented. Both the thrust coefficient and torque coefficient increase when the advance ratio increases. The maximum thrust of the propeller occurs at the phase angle of 18° and the minimum thrust occurs at 108°. It is noted that at phase angles of (formula presented) and, 108° the blade tip loss decreases because the blade tip vortex is blown downstream by the free stream. Due to vortex impingement underneath the blade, a separation region appears on the 0.75 radial position at (formula presented). The acoustic results show that the tonal noise occurs at the blade passing frequency (BPF) and its harmonics. The sound pressure level at 1 BPF near the phase angle of is higher than that near (formula presented), The characteristics of the overall sound pressure level is the same as that at 1 BPF, which implies the tonal noise is the dominant source of propeller noise.