Numerical Analysis and Aeroacoustic Simulation of Noise from Wind Turbines

Abstract

Noise disturbance is one of the major factors considered in the development of wind farms near urban areas, and therefore an accurate estimate of the noise levels generated by wind turbines is required before production and installation. Horizontal-axis wind turbines are the most popular type of turbines and the aeroacoustic noise generated by their rotating blades is known to be their most significant source of noise. The region of the turbine blade that produces the strongest acoustic sources has been identified in published acoustic camera measurements and is the 75% - 95% region of blade span. In the present work, a Large Eddy Simulation (LES) of this region is carried out using an annular computational domain, which leads to a significant reduction of computational expense compared to full blade simulations. The Ffowcs Williams and Hawkings (FWH) acoustic analogy is then used to predict the far field sound. Numerical results for a simulation of the CART-2 wind turbine show good agreement with the available experimental data. Studies show that trailing edge noise is the major noise source from an aerofoil. However, in a highly turbulent environment, leading edge sources could contribute to the far field noise significantly. A geometric improvement to the blade shapes could lead to reduction in noise generation. In present thesis, a geometric modification is based on the leading edge hook structures of owl wings. The modified wind turbine blade was simulated using the previously validated model. Far field noise results are presented showing a noise reduction for the modified blade.