An Efficient Approach for the Simulation and On-Blade Control of Helicopter Noise and Vibration

A suite of computational tools capable of predicting in-plane low frequency rotorcraft noise and its control using active flaps operating in closed-loop mode is developed. A combined code, consisting of AVINOR, a comprehensive code for active control of vibration and noise, and an acoustic code called HELINOIR, is first validated against wind tunnel tests and subsequently verified against computational results. The in-plane noise reduction obtained with a single 20% chord plain trailing edge flap, for a rotor configuration resembling the MBB BO-105 during level flight at a moderate advance ratio is studied. A combination of various far-field and near-field feedback microphone locations was examined. A near-field microphone located on a hypothetical left boom position was found to be the best location and produced an in-plane noise reduction of up to 6 dB. However, this noise reduction was accompanied by an out-of-plane noise increase of 18 dB and a 60% increase in the vertical hub shear. These penalties can be partially alleviated by using a dual plain flap configuration.