Numerical study of novel multi-flapped-serration noise reduction mechanism of wind turbine airfoil
The application of trailing-edge serrated components to reduce turbulent boundary-layer trailing-edge noise is an effective way to reduce wind turbine blade noise.In the paper,the noise reduction mechanism of a novel multi-flapped-serration with curved shape designed on NACA643418 wind turbine airfoil is numerically studied.Large eddy simulation(LES)is employed to calculate the flow field of baseline airfoil and trailing-edge serrated airfoil with incoming wind speed of 20 m/s and 5° angle of attack.The aero-acoustic response near the trailing edge is analyzed based on FW-H acoustic analogy method.The results reveal that compared with airfoil without serration,airfoils with curved-shape and triangular multi-flapped-serrations can effectively optimize airfoil aerodynamic layout,and improve lift-drag ratio and lift with appropriate design parameters,where multi-flapped-serration with curved shape can obtain the better aerodynamic performance than triangular multi-flapped-serration.After the flap angle serration changes the trailing edge flow field,the horseshoe vortices at the serrated trailing edge flow field without flap angles are mixed into a single vortex,resulting in a positive impact on the suppression of medium and high frequency noise.Meanwhile,the noise reduction effect of multi-flapped-serration with curved shape proposed here is better than that of triangular multi-flapped-serration.
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