Integrated numerical method for the prediction of wind turbine noise and the long range propagation

Abstract

Characteristics of noise propagation from wind turbine have been studied by using the integrated numerical methods based on Ray theory. There are two numerical approaches in this paper. Those are constructing noise sources of wind turbine and computing the noise level on the ground. First of all, the flow fields around the wind turbine blade are calculated using Wind Turbine Flow, Aeroacoustics and Structure analysis (WINFAS). WINFAS is an unsteady vortex lattice methods based on potential flow. The results of flow analysis are used for predicting tonal noise, turbulence ingestion noise, and airfoil self noise. Tonal noise is induced by the displacement of fluid and loading fluctuation of the blade and those are predicted by Farassat 1A equation. Moreover, semi-empirical formulas are used for the prediction of broadband noise such as the airfoil self noise and turbulence ingestion noise. Before the beginning of the next step, the acoustic pressure is integrated at the each point of virtual acoustic sphere considering retarded time. It also represents the noise directivity on wind turbine. Then, the noise level on the ground has been predicted including the effects of air absorption, ground reflection and diffraction.