Localized Individual Blade Root Pitch Control for Helicopter Blade-Vortex Interaction Noise Reduction

摘要

A numerical study was conducted on a four-bladed model rotor to investigate the potential of individual blade root pitch control (IBC) in reducing blade-vortex interaction (BVI) noise. Localized IBC inputs in the second quadrant were considered for weakening the advancing side interacting vortices, and similar inputs in the third quadrant were considered for weakening the retreating side interacting vortices. Second-quadrant IBC inputs were highly effective in reducing advancing side BVI noise, with 2° and 3° amplitude inputs practically eliminating advancing side BVI noise. Third-quadrant IBC inputs had a limited effect on reducing retreating side BVI noise due to the higher baseline interacting vortex strengths on the retreating side and detrimental changes in interaction geometry. A combination of 3° amplitude second-and third-quadrant IBC inputs were most effective, resulting in the practical elimination of advancing side BVI noise and a 4.6-dB overall reduction in peak BVI noise.