Aeroacoustic investigation of side-by-side urban air mobility aircraft in full configuration with ground effect

Urban air mobility (UAM) aircraft has emerged as the solution to the growing traffic congestion problems and increasing demand for efficient air mobility. However, noise pollution is one of the major concerns for gaining social acceptance as UAM is being designed for future transport in highly populated urban areas at low altitudes. The noise generated by UAM aircraft can exceed the acceptable noise level due to the ground effect when it approaches a vertiport. This study investigates the ground effects on the aerodynamic and noise performance of side-by-side UAM aircraft in full configuration by utilizing coupled vortex methods and acoustic analogy, respectively. The simulation results show that fuselage and ground directly influence the aerodynamic loads of the rotor blade, wake structure, acoustic signature, and noise directivity. As the aircraft approaches the ground, the sound pressure level (SPL) increases, and the impact of the fuselage becomes more noticeable, especially above the rotor system, due to the stronger upwash wake by the airframe and the ground. Moreover, the most pronounced ground effect on the noise characteristics of the UAM aircraft is the high-frequency tonal noise, and the overall sound pressure level (OASPL) in the aft quadrant of the UAM aircraft is higher than the forward quadrant due to the higher loading in the rear of the rotor plane. The results of the noise hemisphere analysis show that the maximum OASPL increases by more than 3 dBA as the altitude of UAM aircraft gets closer to the ground.