Reducing Noise Generated from a Wind Turbine Blade by Pitch Angle Control using CFD and Acoustic Analogy

Investigation of the effects blade pitch angle on noise emission from a horizontal axis wind turbine is the goal of this paper. To understand the flow around blade wind turbine, and to reduce noise emission in order to respect noise regulation, especially a residential area, three different pitch angles 0 degrees, 3 degrees, and 6 degrees are tested, using computational aerodynamic and aero acoustic methods. Three dimensional flow simulations are carried out with two unsteady CFD simulations URANS, DES used to calculate the near-field flow around a HAWT of NREL Phase VI small scale. The far field noise is predicted from the simulated sources by the Ffowcs William and Hawkings analogy, and compared and validated with available test data for a small-scaled model of the NREL Phase VI. The comparison demonstrates a generally good agreement between DES predicted and measured noise levels. It can be seen that the noise emission increases by decreasing pitch angle. Moreover, the pitch angle control has a significant effect on the noise emission especially in the intermediate frequency range. We show that it is possible to reduce the noise level by control pitch angle without losing too much the power.