Development of Microstructured Low Noise Propeller for Aerial Acoustic Surveillance

The multi-rotor drone market is expected to rapidly expand in the next few years. Drones have huge potential for various missions such as delivery and surveillance, and they will likely be operated in the urban areas, close to human. In this situation, drones are expected to cause noise pollution and the solutions are required immediately for preventing that. In this study, we developed a method to reduce the noise that utilizes the attachment at trailing edge of the propellers. The effect of the attachment on the aerodynamic and acoustic performance is investigated experimentally and numerically. From the single propeller experiments and simulations, we found that the trailing-edge attachment can reduce the rotation speed, and the microstructure of the trailing-edge is crucial to prevent the large-scale flow separations that greatly increases the noise level at high frequency. By appropriately designing, the attachment can reduce the noise level even down to the level lower than the basic one. Our results point out that the simple trailing-edge attachment may improve the acoustic performance of the propellers and it will be useful for the acoustic surveillance.