Rotor–Rotor and Rotor–Airframe Aeroacoustic Interactions in a Full-Scale Lift-and-Cruise UAV: Noise Measurements and Hybrid Aeroacoustic Modeling

Abstract

This paper presents a computational aeroacoustic approach for investigating rotor--rotor and rotor--airframe aeroacoustic interactions in a lift-and-cruise UAV configuration representative of a full-scale vehicle, using wind-tunnel noise measurements and hybrid aeroacoustic modeling. The computational framework couples the lattice Boltzmann method with an actuator-line model to resolve aerodynamic interactions among lifting rotors, the airframe, and a pusher propeller. The acoustic field is predicted using stationary permeable data surfaces within a frequency-domain formulation of the convected Ffowcs Williams--Hawkings equation. The approach is evaluated using two configurations: a 35\%-scale isolated propeller, which establishes baseline aerodynamic and acoustic accuracy, and a lift-and-cruise aircraft representative of a full-scale vehicle, with a truncated wingspan, two lifting rotors, and a pusher propeller. The lift-and-cruise measurements and simulations are used to identify installation and interaction effects on the radiated noise. Results show that the airframe increases tonal noise and introduces additional interharmonic spectral components, particularly beyond the sixth blade-passing-frequency harmonic. These findings demonstrate the importance of resolving rotor--rotor and rotor--airframe interaction mechanisms in multi-rotor noise prediction. Overall, the developed framework provides an efficient and reliable predictive capability for assessing aerodynamic interaction mechanisms and their acoustic impact in advanced air mobility vehicle design.