Prediction of potential interaction noise in a generic rotor–strut arrangement
R. Zamponi, A. Beni, A. Zarri, J. Christophe
Abstract
The growing demand for quiet unmanned aerial vehicles (UAVs) calls for noise prediction tools capable of capturing the complex aerodynamic interactions occurring in rotor-airframe integrations at low computational cost. This paper presents an analytical framework to predict the potential-interaction tonal noise generated by a propeller operating upstream of its supporting strut, a dominant contributor to the acoustic signature of small UAVs. Aerodynamic sources of loading noise from the propeller and strut are modelled using potential-flow solutions, while a hypotrochoidal conformal mapping is employed to represent the inflow distortion induced by struts with arbitrary non-circular cross-sections. The method requires as input the spanwise distribution of steady loads from an isolated propeller, estimated through an unsteady panel solver that offers a favourable trade-off between computational efficiency and simulation fidelity. Analytical predictions are validated against experimental data for struts of varying cross-section diameters and shapes, different blade numbers, and multiple far-field observer locations. The results confirm that the models accurately capture the dominant physics of propeller-strut potential interaction, predicting sound pressure levels within 3 dB for most observer angles and blade-passing-frequency harmonics. The potential of the proposed methodology to support UAV noise optimisation is demonstrated by addressing the sound radiated by propellers with struts featuring spanwise-varying cross-sections.