Reducing Rotor-Airframe Interaction Noise in Drones Using a Curved Support Rod

What is it about?

Rotor-airframe interaction noise is a noise source that commonly occurs on multi-rotor vehicles. Each time the rotor blade passes the stationary support (rod), pressure fluctuations occur on the rotor and rod. This interaction excites tones at the harmonics of the blade passing frequency by as much as 20 dB. For the conventional design, the blade approaches the rod, and pressure fluctuations are generated across the span of the rotor, simultaneously, from root to tip. By curving the rod, the interaction does not occur simultaneously but gradually, as only a small segment experiences pressure fluctuations at any moment. Experimental results showed that curving the rod significantly reduced the interaction noise to the point where the curved rod configuration nearly matched that of the isolated rotor, where no rod was near the rotor.

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