Key points are not available for this paper at this time.
This paper investigates the potential of looped propeller blades to reduce aerodynamic noise through the diminution of blade tip-vortex interactions. Flow simulations were performed in ANSYS Fluent using high-fidelity LES combined with the Ffowcs William-Hawkings model to evaluate the acoustics. Experimental wind tunnel testing was conducted in static and forward flight conditions to validate the simulations and to assess the performance of the novel blades. The comparison between numerical and experimental results shows good agreement for the thrust trends and noise spectra. Two design variations were tested to investigate the effect of changing the plane in which the looping occurs. Results indicate that the in-plane looped propellers can reduce noise generation by up to 10dB (OSPL) albeit with a reduction in both thrust performance and propeller efficiency. Conversely, when the looping occurs out of plane, it was found to have a slight increase in noise generation along with a reduction in efficiency. Flow visualization showed that looped propeller design seems to reduce the strength of tip vortices in comparison with the conventional propeller which sheds a more concentrated tip-vortex. Findings from this study may have applications for UAVs operating in urban environments, particularly in the design of low-noise propellers.
plessis et al. (Thu,) studied this question.