Noise of a shrouded propeller due to ingestion of grid-generated turbulence

Abstract

An experimental investigation of the noise produced by a shrouded propeller interacting with grid-generated turbulence in an anechoic wind tunnel is presented. Inflow turbulence statistics and the far-field noise directivity were measured. Measured inflow turbulence statistics and propeller operating parameters were used in a theoretical model to predict the turbulent inflow noise spectra and directivity. The theoretical model uses rapid distortion theory to calculate the distorted turbulent field at the propeller plane. The unsteady loading on the rotating blades is calculated using isolated blade response functions. The noise radiated to the far-field is then evaluated using a tailored Green's function approach which accounts for the acoustic scattering effect of the shroud. The theoretical model is able to capture the shape of the directivity pattern of the turbulent inflow noise produced by the shrouded propeller. The agreement between the measured and predicted spectra is reasonable, however the high frequency broadband levels tend to be underpredicted.