A numerical study on the aerodynamic performance of wind turbine airfoils and their modifications has been carried out to\nunderstand the effects of maximum relative thickness and its position on the lift enhancement of blunt trailing-edge modification.\nFirst, the airfoils (NACA4409, NACA4412, NACA4415, and NACA4418) with different relative thickness are modified to be\nsymmetrical blunt trailing-edge airfoils with the software of XFOIL. Then, the lift and drag coefficients of NACA4412 airfoil are\ncalculated using S-A and K-? SST turbulence models, respectively. By comparing the numerical results with the experimental data,\nit is proved that the accuracy of K-? SST model is higher than that of S-A model. Finally, the aerodynamic performance of the\noriginal and modified airfoils, based on the K-? SST turbulence model, is investigated to analyze the increments of lift coefficient,\ndrag coefficient, and lift-drag ratio. Results indicate that the increments of lift coefficient and lift-drag ratio increase first and then\ndecrease with the increasing ofmaximum relative thickness. Furthermore, as the relative thickness position is gradually close to the\nleading-edge, the lift coefficient increment decreases, and the lift-drag ratio increment becomes almost negative.The investigated\nresults can provide a reference for designing blunt trailing-edge airfoil of a wind turbine blade.
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