Active twist smart rotor technology for blade-vortex interaction noise reduction

The results of this feasibility study suggest that active blade twist technology is a viable means to reduce blade-vortex interaction (BVI) noise in rotorcraft systems. A linearized unsteady aerodynamics analysis was formulated and successfully validated with computation fluid dynamics (CFD) analysis. A simple control scheme with three control points was found to be effective for active BVI noise reduction. Based on current-day actuation technology where 1 to 2 degrees of twist per blade activation span is expected, measurable noise reductions of 2 to 4 dB were predicted for the relatively strong, close vortex interactions. For weaker vortex interactions, reductions of 7 to 10 dB were predicted. The required twist actuation per blade span for complete unsteady loading cancellation, however, may be infeasible because of the large stroke and high frequency activation requirements.