A numerical investigation of the aerodynamic and aeroacoustic interactions between components of a multi-rotor vehicle for urban air mobility

In this work, we conduct a numerical investigation of a hexacopter for urban air mobility, emphasizing the interactional effect between different components of the vehicle on the aerodynamic and aeroacoustic performance. The nearfield turbulent flow fields are resolved by delayed detached eddy simulations, and the acoustic waves at far-field observers are computed using an integral solution of the Ffowcs-Williams and Hawkings equation. The results show that the close placement of rotors can lead to remarkable thrust fluctuations and slightly reduce the average thrust. Consequently, the sound pressure level for the tonal components is considerably increased over a wide frequency range, especially at the observers in the upstream and downstream directions. The rotor–rotor interaction also results in a contracted wake geometry towards the vehicle centre and intensifies the dissipation of the vortices in the downstream wake. The presence of connecting arms can cause significant thrust fluctuations on the surfaces of both rotor blades and arms, which produces additional tonal noise at high-order harmonics of the blade passing frequency. In contrast, for current configuration, the existence of the fuselage only slightly reduces the total thrust and contributes little to noise generation.