Experimental characterization of vortex generators induced noise of wind turbines

The wind energy industry is progressively aiming towards larger wind turbine size as a means of increasing energy production efficiency. Wind turbine rotor blades are becoming significantly more flexible and have an increased risk of structural failure. Thicker airfoil profiles can be used to increase the structural strength. However, thicker airfoils are more prone to flow separation with adverse effect on power generation. Vortex generators (VGs) are an effective solution to delay flow separation. However, VGs significantly increase radiated noise levels. This presented research experimentally investigates the effect of VGs on blade noise production. Specifically, the influence of the VG geometric shape is evaluated while keeping the dimensions constant. Wind tunnel tests have been carried out on a NACA 0018 that is equipped with triangular vane-type VGs specifically designed for the test conditions. A microphone phased array is used to assess the radiated noise using the beamforming technique. The results show that the VGs significantly contribute to increase the blade noise production with having a predominant role at high-frequencies where the VG acts as a non-compact aeroacoustic source.