An experimental investigation of aerodynamic and aeroacoustic performance of a wind turbine airfoil with trailing edge serrations.

Trailing edge (TE) serrations are widely used as an effective passive control method to reduce the turbulent TE noise from wind turbine blades. Other than the acoustic effects, the aerodynamic performance of serrations is also an important issue that should be considered, since it determines the power output of the blade. To this end, the far-field sound pressure level, flow field, and aerodynamic force of the serrated airfoil were measured in an anechoic wind tunnel, and the lift increase and noise reduction effects of the TE serrations were comprehensively evaluated. The result showed that the presence of TE serrations could achieve noise reduction by about 2 dB at the low-to-moderate frequency range at small angles of attack, and meanwhile it could suppress the fluctuation of aerodynamic forces. In addition, the proper orthogonal decomposition method was deployed to decompose the wake flow into various vortex structures with different portions of turbulent kinetic energy so as to reveal the noise reduction mechanism of the serrated TE. The result suggested that TE serrations could effectively inhibit large-scale vortex structures that shed from the boundary layer on the suction side, thereby achieving noise reduction around the vortex shedding frequency.