Multi-fidelity assessment of eVTOL propeller noise in ground-effect conditions

Abstract

The aeroacoustic impact of ground proximity on an eVTOL propeller in hover and edgewise flight is examined using a multi-fidelity framework. Delayed-Detached Eddy Simulations (DDES) in OpenFOAM, coupled with PSU-WOPWOP, for high-fidelity acoustic predictions, and CDI-CHARM, a free-vortex panel-method code, as a lower fidelity approach. Extensive validation of the numerical simulations against experiments was performed. Performance metrics and flow-field analyses were examined prior to conducting the acoustic analysis. In-ground-effect (IGE) conditions, here defined as rotor operation within a few radii of a rigid ground plane, modify wake dynamics and alter tonal and overall sound levels, producing around $\sim$ 5 dB SPL increases beneath the rotor. CHARM reproduces the main tonal trends observed in DDES cannot predict broadband content. We also evaluate approaches for treating ground reflections, including the Method of Images (MOI), and introduce a permeable “upside-down T” acoustic surface that captures reflected waves without requiring MOI. These findings clarify rotor–ground acoustics and offer practical guidance for permeable acoustic surface selection in high-fidelity simulations.