Numerical Simulation And Optimization Of Aerodynamic Noise On Horizontal Axis Wind Turbine

The environmental problem of wind energy using has been catching a lot of attention because of the wind resources development and utilization recent ten years. Despite the destruction of vegetation, landscape, cultivated land and pasture caused during the wind farm instruction, the noise caused during wind turbine operation has been the key environmental problem, which becomes the primary problem complained by the people located near the ranch. The noise caused by wind turbine can be divided into two aspects: the machine noise and the aerodynamic noise, which the latter shares the majority of the total noise. It is difficult to reduce the aerodynamic noise by common reduction measures performed on machine noise, such as vibration isolation, closed cabin and sound-absorbing material, which is because of the aerodynamic noise is usually produced on the rotated blade and the unsteady fluid field around the blade. In recent years, with the diameter becomes huger and the higher blade tip speed ratio, the aerodynamic noise becomes more seriously.In this paper, two noise reduction measures are applied to study the optimization effect and the flow feature and then get to the access of wind turbine noise reduction, especially for the large-scale wind turbine. In chapter 3, the numerical simulation model and two modified geometry(wavy leading edge and openings on surfaces) is applied to explore the aerodynamic performance and noise via distinguishing the overall sound pressure level, the coefficient of lift and drag force and the distribution of quadrupole. The results shows that the two modified geometry(wavy leading edge and openings on surfaces) both can reduce the overall sound pressure level, and the openings on surfaces one has the better reduction effect. The wavy leading edge model is easily installed due to the simple blade structure, and the model can make a larger impact on lift and drag force, while does the little impact on the noise reduction compared with the openings on surfaces model. The structure of openings on surfaces model is difficult to install, and it can reduce more noise with rational speed control, at the same time it can maintain high aero efficiency. In chapter 4, the numerical simulation is performed on NREL Phase VI wind turbine at the incoming speed of 7m/s with unsteady RANS/LES model. From the results of the aerodynamic noise and flow feature, the quadrupole becomes more obviously at the larger rotor, which is the key to reduce the total noise. Taking the chapter 3 and 4 into account, the openings on surface is applied to reducing the blade tip noise, while the wavy leading edge and blunt trailing edge measure is applied to the middle of the blade and the blade root maintaining the structural efficiency.