Experimental investigation into the aerodynamic and aeroacoustic performance of bioinspired small-scale propeller planforms

Abstract

The multi-rotors have a limited operational period and generate too much noise, which is insufficient for complex tasks and adversely affects humans’ and animals’ health. Nevertheless, their market has become increasingly popular. Therefore, low-noise products are more competitive, and aerodynamic and acoustic improvements are critical. This investigation aims to design a small bioinspired propeller with the same power input as a conventional propeller to achieve the same or better aerodynamic performance while decreasing noise. Accordingly, an experiment investigated the impacts of operation conditions and varied geometric parameters on six small propellers' aeroacoustic performances with a unique planform shape inspired by five insects and one plant seed, such as Blattodea, Hemiptera, Hymenoptera, Neuroptera, Odonata, and maple seed. Each propeller was operated at eleven rotational speeds ranging from 3000 to 8000 RPM with no freestream velocity for simulating hover conditions. Compared to the baseline propeller, the results demonstrate that all bioinspired propellers produce more thrust for the same power supply, reduce harmonic and broadband noise, and provide a better noise level. Also, their rotational speed is lower and their figure of merit is higher than the baseline propeller at hover flight with 3N thrust. They all outperform the baseline propeller in terms of hover efficiency at all thrust values considered. Besides, the Neuroptera propeller is more efficient than other propellers, decreasing 5.5 W of power and reducing 7.9 dBA at hover flight with 3N thrust and 1.5 meters distance, compared to the baseline propeller.