Effect of Rotor Blade Deflections on Blade-Vortex Interaction Noise Prediction

摘要

Blade-vortex interaction (BVI) noise is a main noise source from a rotorcraft and has been a barrier to wide acceptance for applications of rotorcrafts. In order to predict the noise accurately, it is required to consider characteristics of rotor blades having high aspect ratio as well as flow-unsteadiness around blades. Therefore a numerical analysis of BVI needs a prediction method using an aerodynamic and structural coupling, and it is required to investigate the effect of blade deflections on BVI noise prediction as a preliminary study for development of the coupled method. In this study, deflections of rotor blades were divided into flapping, lead-lag and torsional deflections and the effect of variations of those deflections on the noise prediction was investigated. In order to predict the noise, Farassat's Formulation 1A and free-wake panel method using CVC (Constant Vorticity Contour) and VLM (Vortex Lattice Method) were used. For the validation of the noise prediction, the predicted result was compared with the experimental result of HART II (Higher Harmonic Control Aeroacoustics Rotor Test) rotor. The result demonstrated that the blade air-load, acoustic pressure time history and noise contour were well predicted. Based on the validation, noise predictions through variations of the blade deflections were performed, and the effect of each blade deflection on the noise prediction was analyzed.