Experimental and Numerical Studies of Active Flow Control Technique for the Reduction of Helicopter BVI Noise

A novel technique regarding the reduction of helicopter blade-vortex interaction noise is proposed. The proposed technique is based on the idea of injecting air at the leading edge of the blade to alter the vortex characteristics (strength and core size). The numerical investigations are performed using the large-eddy simulation (LES) approach. The simulations were performed for a Reynolds number, Re=1.3x10^6, based on the NACA0012 airfoil chord and free-stream velocity. Two measurement techniques: laser sheeting photography and velocity measurements utilizing a hot-wire anemometer, were conducted in a low-speed wind tunnel environment. The present study shows that by injecting air at the leading edge of the blade, the influence of blade-vortex interaction on the aerodynamic coefficients and aeroacoustic noise is significantly reduced.