GPU-Accelerated CABARET Simulations of Distributed Propulsion for UAM

Urban Air Mobility (UAM) vehicles rely on distributed propulsion (DP) to achieve efficiency, control authority, and compact integration with lifting surfaces. The close spacing of multiple rotors, however, intensifies installation effects that elevate tonal and broadband noise. This work presents a high-fidelity Large Eddy Simulation (LES) study using the CABARET method on rotating meshes to quantify aeroacoustic and aerodynamic sensitivities of a three-propeller DP configuration. The campaign varies: (i) central-rotor axial position (∆ = {−0.2, 0, +0.2}), (ii) inter-rotor phase angle (0°, 45°, 90°, 135°), and(iii) blade trailing-edge geometry (baseline vs. sawtooth serrations). Band-limited overall sound pressure level (BL OASPL) is evaluated on a probe plane under the array between the 1st and 6th blade-passing frequencies. Key findings are: (a) serrations consistently reduce area-averaged and maximum BL OASPL by up to 2.4 dB, most notably around 90◦ phase; (b) moving the central rotor closer to the wing increases thrust coefficient by ≈ 7.8%, indicating a beneficial rotor–wing interaction akin to ground effect; (c) the aerodynamic penalty of serrations is modest and attributable to effective area loss near the tip. Flow visualizations show serrations disrupt spanwise coherence and trailing-edge vortex organization, explaining the observed acoustic benefits. The results highlight the importance of joint optimization of geometry and phasing to deliver quieter, efficient DP systems for UAM.