Effect of geometrical features on the noise of propellers through time-domain and frequency-domain broadband noise predictions

Abstract

This study aims at investigating into the capability of reducing the broadband noise of a propeller, by means of sawtooth trailing edge and leading edge serrations. New analytical models for predicting noise from airfoils with serrated edges are implemented and applied to propellers using a blade strip approach. These models are assessed by comparison with spectra obtained from time-domain Lattice Boltzmann Method simulations.Obtained results showed that the analytical models are able to predict the noise from either straight or serrated propellers with a good accuracy. A parametric study was conducted to predict the noise emitted by propellers featuring sawtooth trailing edge or leading edge serrations with different parameters. The results of the serratedtrailing edge show that the use of serrations reduces the noise emitted by the propellers at low to mid frequencies but induces a noise increase at high frequencies. The sharpest serrations were found to achieve the better performance in terms of reducingnoise. For the serrated leading edge, the results show that the serrations are effective in reducing the noise emitted by the propellers at high frequencies. The noise reduction increases with the increased serration amplitude, while the variation of serration wavelength shows no significant effect on the noise reduction