Aeroacoustic investigation of multirotor unmanned aircraft system (UAS) propellers and the effect of support structure

The use of unmanned aircraft systems (UAS) or drones is growing, particularly for applications which must be performed near people, such as real-estate aerial photography. Urban UAS operations have led to noise is becoming an increasing concern for the community. The noise generated by a single typical multirotor UAS arm; including propeller and support structure, is investigated. Part of the measured noise arises from the propeller flow field and its interaction with the airframe support structure (arm). We have experimentally determined the acoustic emissions and wake of a typical UAS propeller in isolation, including 3-component velocity measurements at frequencies up to 2000 Hz. We also investigated the effect of the (highly 3D) flow field as it impinges on a typical airframe support structure. The results give guidelines for minimising this component of the aeroacoustically generated noise and recommendations are made for additional noise reduction.