FLAPS FOR WIND TURBINE APPLICATIONS: RESULTS OF AN ACOUSTIC STUDY

摘要

Wind speed varies substantially over time. These unsteady wind conditions lead to high dynamic loads on the wind turbine blades. The most common pitch system is too inertial to control these dynamic loads. Plain flaps at the rotor trailing edge have been proven to be an effective load reduction concept. The plain flap's acoustics are presented in this paper. The acoustics are studied with an experimental set-up. The advanced acoustic method beamforming is used to localize the sound source at the plain flap, such as side edge noise. This investigation shows that the flap noise is correlated with the flap deflection angle, and the angle of attack of the entire airfoil. The flap noise of a deflection towards the suction side is limited to a high frequency band. In contrast, a deflection towards the pressure side leads to broadband flap noise. The localization of the side edge noise at the plain flap proves that these differences are not caused by the side edge. The side edge noise in the flap acoustics is limited to the high frequency band. The broadband noise of a deflection towards the pressure side must therefore originate from another source. Flow separation is assumed.