Airfoil–Vortex Interaction Noise Control Mechanism Based on Active Flap Control

Blade-vortex interaction (BVI) noise is a significant source of rotor noise. In recent years, active flap control (AFC) has been used successfully to control BVI by adding a trailing edge flap to the blade. However, due to the rotor’s complex shape and motion in AFC, the accurate simulation of the motion and unsteady flow field is challenging. Therefore, studies of noise control by AFC have mostly focused on experimental methods. Few numerical simulations were conducted on the noise reduction mechanism. In order to understand the noise reduction mechanism of the AFC clearly, this paper establishes a computational fluid dynamics (CFD) method based on an overset grid and tries to simulate the AFC airfoil flow field with the artificial vortex interaction. The noise characteristics are obtained from an acoustic analogy method based on the Farassat 1A (F1A) equation. By parameter analysis study and by testing the airfoil load and vertical interference distance, the results show that the proposed active control method exactly reduces the airfoil-vortex interaction noise. A maximum noise reduction of 1.56 dB is observed, and the most critical control parameter is the deflection phase of the trailing edge. When the vortex core passes over the airfoil, the load fluctuation and the interaction noise can be reduced by an upward deflection of the trailing edge. The flapping of the trailing edge significantly changes the vortex core’s path, which can further control the downstream airfoil-vortex interaction and achieve noise reduction.