Aerodynamic and acoustic measurements of dual small-scale propellers

Multiple propellers are usually used in unmanned aerial vehicles. This work studies the aerodynamic and acoustic properties of dual propellers in close vicinity. Aerodynamic and acoustic tests of the side-by-side propellers were conducted in an anechoic chamber, and the flow recirculation effect was considered in the analysis to reduce uncertainties in the results. We mainly focused on the influence of the propeller separation distance for various propellers at different rotational speeds and rotational directions. For the cases studied, the results indicate that there is a negligible interactional effect on the mean thrust, tonal noise at the blade passing frequency (BPF) and the overall sound pressure level (OASPL) at most observation angles. For the observers apart from the wake region, the noise radiated from the dual propellers could be approximatively assessed by simple superimposition of different propellers. Numerical simulations are also conducted to investigate the flow field of the dual-propeller configuration. It is found that the unsteady wake flow from each propeller is contractive, leading to little mutual effect. The study might be beneficial to simplification of relevant acoustic modeling process and noise prediction of drone propellers.