Experimental and numerical investigation of an optimized airfoil for vertical axis wind turbines

The present study addresses the experimental and numerical verification of the performance of a new airfoil design for lift driven vertical-axis wind-turbines (VAWT). The airfoil is obtained by a genetic algorithm optimization of the objective function proposed by Simão Ferreira and Geurts [19], which optimizes the aerodynamic performance of airfoils having a relatively larger thickness, providing with better structural stiffness compared to more slender NACA design. The work presents an experimental analysis of such improved performance of a 26% thick VAWT-optimized airfoil (DU12W262). The 2D flow velocity, pressure and aerodynamic loads are measured by combined use of Particle Image Velocimetry, wall-pressure sensors and wake rakes. Additionally, the airfoil surface pressure is determined by integrating the pressure equation from the experimental velocity field. Results are initially obtained with the airfoil in steady conditions, at Reynolds 3.5 ∗ 10, 7.0 ∗ 10 and 1.0 ∗ 10 with both free and forced (1%c) boundary layer transition. Xfoil simulations are employed for comparison to the experimental results, showing a good agreement in the linear range of angle of attack and a consistent lift/drag overestimation in the separated one. The experimental data are used as input for a numerical simulation of a 2D VAWT. CFD simulations of the airfoil are performed and validated against the experimental data. NOTE: This is a draft and incomplete version of the paper, as the CFD simulations are yet not available. The full updated version of the paper will be available upon the conference.