Multi-Fidelity Assessment of eVTOL Propeller Noise in Ground-Effect Conditions

This study examines the aeroacoustic effects of ground proximity on an eVTOL propeller in hover and edgewise flight using a multi-fidelity simulation framework. High-fidelity DDES simulations in OpenFOAM, coupled with PSU-WOPWOP for FW-H acoustic predictions, and mid-fidelity CHARM simulations were used. In both cases, the Method of Images (MOI) was applied to account for ground reflections. Results show that ground effect strongly influences both thrust and noise. In hover, thrust increases near the ground due to more uniform loading. Tonal noise is amplified below the propeller and attenuated above due to destructive interference, trends captured by both CHARM and DDES. However, CHARM overpredicts broadband noise due to modeling limitations. High-fidelity results highlight the importance of permeable FW-H surface placement for accurately resolving wake–ground interactions. In both flight conditions, the in-ground effect (IGE) increases tonal noise by up to 10~dB beneath the propeller, while broadband noise is elevated farther from the ground. Edgewise flight reveals a potential critical clearance near one propeller radius, where broadband noise peaks, possibly due to resonance or intensified blade–wake interaction. An extended grid study further demonstrates that refining the near-ground region enables MOI-free permeable surfaces for ground-effect simulations, yielding more symmetric beamforming maps and improved far-field acoustic accuracy. These findings support the use of MOI across fidelity levels and emphasize the need for permeable surfaces and refined grids in high-fidelity ground-effect simulations.