Tip-Vortex Noise Reduction of a Wind Turbine Using a Winglet

Abstract

The present study investigates the feasibility of using winglet as a novel approach to reduce aero-acoustic noise of wind turbine blades. For this purpose, the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is used as the baseline case. The flow field is simulated by computational fluid dynamics and SST k-ω turbulence model. Further, the Ffowcs Williams and Hawkings (FW-H) acoustic analogy is implemented for noise prediction. The aero-acoustic simulations are performed for different wind speeds and distances from the base of the tower. The results indicated that the aerodynamic sound pressure level (SPL) is intensified in all frequencies by increasing the wind speed; however, its production rate is decreased in high wind speeds. Moreover, the SPL at the downstream of the tower is higher than the upstream due to the disturbances emerged in the flow field. Furthermore, the SPL for the baseline and the modified blade shows a little difference in low frequencies; however, in high-frequencies, differences become noticeable. Introducing winglet at the blade tip is effective in high frequencies and can lead to a significant decrease in noise emission especially near the tower, but it has no perceptible effect on noise emission in low frequencies.