A new configuration of the rotor blade for BVI (blade vortex interaction) noise reduction has been developed and validated in wind tunnel at Fuji Heavy Industries Ltd. (FHI). The tip of this rotor blade has two small lifting surfaces, a canard-like front wing and a rear wing. Employing two lifting surfaces, the tip vortex is divided into two vortices, which interact mutually and merge into a vortex with lower swirl velocity. Furthermore, the canard incidence is controlled to avoid the degradation of aerodynamic performance. The canard tip showed a reduction of almost 50% in the swirl velocity of the tip vortex compared to the baseline rectangular tip in a non-rotating blade tip wind tunnel test. The results in a rotating rotor wind tunnel test revealed that a reduction of 2.5 dBA in the SPL (sound pressure level) could be achieved. The performance penalty of the canard tip at high-speed flight could be minimized with proper control of the canard incidence. The aerodynamics design and control law of the canard tip will be presented as well.
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