Attenuation of Vortex Noise Generated by UAV Propellers at Low Reynolds Numbers

摘要

The increased demand for commercial UAVs has raised concerns about their noise pollution. UAV propeller blades were designed and tested to minimize the noise signature of the propellers while maintaining their thrust. Noise reduction was achieved through a reduction in tip vortices and trailing edge wake with the use of serrated trailing edges and proplets. Proplet and serrated trailing edges were tested against a base APC 9x6E propeller at a constant RPM and a Reynolds Number of 97,000±4,000. The use of proplets showed little to no benefit in noise reduction. Increasing serration depth showed a maximum 28% decrease in propeller noise while maintaining thrust within ±5% of the base APC 9x6E propeller. However, diminishing returns were seen with increased serration depth past 35% MAC serration depth. Power spectra of the propellers' noise showed that an increase in serration depth correlated with a decrease in strength of the trailing edge wake.