Unsteady flow over offshore wind turbine airfoils and aerodynamic loads with computational fluid dynamic simulations

The first notable megawatt class wind turbine, which was the pioneer of improvement in the blade performance in large wind turbines, appeared in Vermont. Nowadays, modern wind turbines are using blades with multi-airfoils at different sections. In this study, in order to indicate the best airfoil profile for the optimum performance in different sections of a blade, five popular airfoils, including S8xx, FFA and AH series, were studied. On the large-scale profile, shear stress transport K-omega model was applied for the simulation of horizontal axis wind turbines for different wind speeds. The aerodynamic simulation was accomplished using computational fluid dynamic method, which in turn is based on the finite volume method, and semi-implicit method for pressure-linked equations algorithm is used for pressure-velocity coupling. The governing equations applied in this simulation are the unsteady Reynolds-averaged Navier-Stokes equations. The aerodynamic coefficients of lift and drag were calculated at different angle of attacks and different wind speeds. The results were validated by EPPLER code, XFOIL and experimental data of the US National Renewable Energy Laboratory. The results showed that S818 profile is the best profile in terms of gaining the highest lift coefficient with the lowest angle of attack at the root of the blades. The findings also indicated that the selected model can predict the exact geometry with a high precision.