Asymmetric airfoil selection for a small-scale vertical axis wind turbine: A numerical study

Vertical-axis wind turbine (VAWT) efficiency depends mainly on the aerodynamic properties of the airfoils used in their blades. During each rotation of the turbine, the blade experiences a range of angles of attack (AOAs) with respect to the relative wind, resulting in a variation of its contribution to the overall performance of the turbine. This paper leverages the capabilities of XFoil for preliminary performance analysis and ANSYS Fluent for detailed Computational Fluid Dynamics (CFD) simulations. The initial selection of airfoils is based on geometric characteristics and their potential for high tangential force coefficients. The asymmetric airfoils were selected by maximizing the average tangential force coefficient within the operational range of the AOAs through simple and computationally inexpensive 2D analysis. We then investigate the performance of the selected asymmetric airfoils in small-scale VAWTs for two rotor configurations, namely for two-bladed and three-bladed turbines. Using CFD, these configurations are compared with a baseline rotor utilizing a symmetric NACA 0018 airfoil. The rotors equipped with the asymmetric airfoils showed an increase in the power coefficient by 7.7% for the two-bladed rotors and 6.8% for the three-bladed rotors at the TSR of 4 and TSR of 3, respectively.