Acoustic Predictions for the Side-by-Side Air Taxi Rotor in Hover

In this paper, acoustic predictions are performed for the rotors of NASA’s side-by-side Urban Air Mobility (UAM) aircraft in hover. Investigations of the acoustics are performed on four overlap configurations, 0%, 5%, 15%, and 25%, in hover via high-fidelity Computational Fluid Dynamics (CFD) simulations. CFD simulations are carried out using the HPCMP CREATETM-AV Helios and acoustics calculations are conducted using PSUWOPWOP. Blade airloads and performance of the rotors are computed for this study. Predictions on the rotor airloads and wake geometry are compared for all overlap configurations at a collective pitch angle of 8°. It is shown that the 25% overlap configuration yields a higher overall sound pressure level (OASPL) than for the other overlap configurations, mainly due to stronger blade-vortex-interactions at the entrance and exit locations of the overlap region. It is found that the OASPL difference in hover is above 62 dB at an altitude of 500 ft (152.4 m), which is the UAM aircraft noise guideline suggested by Uber. Additionally, noise for all overlap cases are compared against various background noise levels. Results show that noise from the side-by-side rotor could not be fully concealed by the various background noise at an altitude of 500 ft (152.4 m).