My student presented his MS thesis on the aerodynamics and aeroacoustics of rotors.
Abstract: Electric vertical take-off and landing (eVTOL) aircraft are characterized by their unconventional wing and electric rotor configurations, which involve both side-by-side and tandem rotor configurations. These configurations create unique aerodynamic and aeroacoustic flow-fields. We numerically investigate the interaction effects between rotor pairs as well as their individual and combined acoustic radiation. We examine horizontal rotor spacing, rotor tilt angles, and forward flight effects. Performance is characterized by thrust coefficient, sound pressure level (SPL) at the blade passage frequency (BPF), and overall sound pressure level (OASPL). This study is performed with a mid-fidelity aerodynamic solver, DUST, which is used to predict the aerodynamic flow-field. The tonal acoustic pressure at observer positions is predicted via the Farassat F-1A formulation of the Ffowcs-Williams and Hawkings equation utilizing the aerodynamic flow-field. The configurations studied show strong aerodynamic interaction effects in thrust, as well as out-of-plane acoustic radiation from the aft rotor. Predictions of thrust and noise are validated via experimental measurement. As rotor separation decreases, we observe that aft rotor thrust decreases and BPF SPL increases. The most forward rotor, however, is marginally impacted by the interactions.