Efficient prediction of propeller noise at incidence

This paper investigates the prediction accuracy and time efficiency of two distinct

low-order methods, Opty∂B and LOPNOR, for predicting tonal and broadband noise of

a drone rotor in axial and non-axial flow conditions. These are both derived from an aerodynamic

rotor model based on the blade element momentum theory, respectively coupled

with a time- (Opty∂B ) and frequency-domain (LOPNOR) solution of the Ffowcs Williams-

Hawkings (FW-H) integral equation applied to a radial distribution of acoustically compact

and non-compact sources. Experimental data and scale-resolving lattice-Boltzmann/verylarge

eddy simulation (LB/VLES) results for a two-bladed small unmanned aerial system

(sUAS) in transitional boundary layer conditions are used to validate the low-order approaches.

Comparison between low-order, high-fidelity and experimental results reveal that

the underlying sound generation mechanisms are accurately modelled by the low-fidelity

methods, which therefore constitute a valid tool for preliminary design of quiet drone rotors

or to estimate the noise impact of drone operations.