Study of aerodynamic noise from UAV rotor in hover and forward flight

Abstract This study employed the Delayed Detached Eddy Simulation (DDES) turbulence model and the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method to investigate the flow field and acoustic characteristics of a 1045 Unmanned Aerial Vehicle (UAV) rotor in both hover and forward flight, considering both dipole noise and overall noise. Results showed that lift fluctuations during forward flight were significantly higher, and the tip vortex dissipation rate was much greater than in hover. A comparison of noise spectra and directivity between hover and forward flight revealed that the noise intensity of the rotor in forward flight was notably higher. Hover rotor noise was dominated by low-frequency noise below 100 Hz, while forward flight rotor noise concentrated near the blade passage frequency (BPF) fundamental. Analysis of the spectral relationship between dipole noise and overall noise indicated that dipole noise was the primary noise source in forward flight. Further investigation of the forward flight rotor under different rotor speeds and shaft angles suggested that reducing rotor speed, could effectively reduce noise, whereas adjusting shaft angle had limited impact on noise reduction. This research provides theoretical insights for noise assessment and reduction in rotorcraft UAV design.