Computational Fluid Dynamics Study of Wind Turbine Blade Profiles at Low Reynolds Numbers for Various Angles of Attack

Airfoil data are rarely available for Angles Of Attack (AOA) over the entire range of +/- 180 degrees. This is unfortunate for the wind turbine designers, because wind turbine airfoils do operate over this entire range. In this paper, an attempt is made to study the lift and drag forces on a wind turbine blade at various sections and the effect of angle of attack on these forces. Aerodynamic simulations of the steady flow past two-dimensional wind-turbine blade-profiles, developed by the National Renewable Energy Laboratory (NREL) at low Reynolds number, will be performed. The aerodynamic simulation will be performed using Computational Fluid Dynamics (CFD) techniques. The governing equations used in the simulations are the Reynolds-Average-Navier-Stokes (RANS) equations. The simulations at different wind speeds will be performed on the S809 and the S826 blade profiles. The S826 blade profile is considered in this study because it is the most suitable blade profile for the wind conditions in Egypt in the site of Gulf El-Zayt on the red sea. Lift and drag forces along with the angle of attack are the important parameters in a wind turbine system. These parameters determine the efficiency of the wind turbine. The lift and drag forces are computed over the entire range of AOA of +/- 180 degrees at low Reynolds numbers. The results of the analysis showed that the AOA between 3 degrees and 8 degrees have high Lift/Drag ratio regardless of the wind speed and the blade profile. The numerical results are compared with wind tunnel measurements at the available limited range of the angle of attack. In addition, the numerical results are compared with the results obtained from the equations developed by Viterna and Janetzke for deep stall. The comparisons showed that the used CFD code can accurately predict the aerodynamic loads on the wind-turbine blades.