Parametric Effect of Blade Surface Blowing on the Reduction of Rotor Blade-Vortex Interaction Noise

Reducing rotor blade-vortex interaction (BVI) noise is a major challenge in rotorcraft research. This paper presents a high-resolution numerical study of the effects of blade surface blowing on BVI noise reduction. Using the improved fifth-order weighted essentially non-oscillatory (WENO-Z) scheme and high-resolution grid system, BVI noise is accurately predicted in the nonblowing baseline case. Four slot locations are examined to study the effects of jet slot location on the control of BVI noise. Additionally, the parametric effects of jet velocity and jet slot area are analyzed. Blowing near the trailing edge on the upper surface is effective for weakening BVI. The optimal jet velocity for reducing BVI noise is 20% of the rotor tip speed, which is 45.2 m/s in the case study. Compared with the baseline case, the sound pressure level is reduced by 3.6 dB. By adjusting the jet slot area, surface blowing can effectively reduce the rotor BVI noise by over 3 dB with minimal thrust penalties. (C) 2021 American Society of Civil Engineers.