Influence of airfoil maximum thickness on aerodynamic performance of vertical axis wind turbines

Airfoil shape can significantly influence the aerodynamic performance of vertical axis wind turbines (VAWTs). However, while the symmetric NACA airfoil series are widely used for VAWTs, the effect of parameters, which define the shape of an airfoil, on the aerodynamic performance of VAWTs has not yet been extensively studied. The current study, therefore, intends to systematically investigate the effect of airfoil maximum thickness tm on the aerodynamic performance of VAWTs for different tip speed ratios (λ). Unsteady Reynolds-Averaged Navier-Stokes (URANS) calculations are performed on high-resolution gird. The results show that the optimum tm decreases from 24%c (airfoil chord) to 12%c when λ increases from 2.5 to 5.5. As higher λ corresponds to lower variations of angle of attack (α) of the blades, the better performance of thinner airfoils at such λ is associated to their higher Cl/Cd at such α. Higher stall angle could explain the higher CP of thicker airfoils at low λ. The current findings could support the optimization of airfoils for VAWTs.