Efficient Aerodynamic Shape Optimization of VAWT Airfoil and Its Validation

Abstract

In this paper, an efficient aerodynamic shape optimization of VAWT airfoil is performed with a Kriging response surface model approach. Numerical evaluations of various airfoil shapes are treated inexpensively by considering the apparent flow velocity magnitudes and apparent angles of attack at multiple positions of VAWT airfoil, which includes some assumptions as two dimensional steady flows, no consideration about flow interactions between blade airfoils and so on. An optimal VAWT airfoil is obtained by the minimization of a proposed objective function. Since our objective function for this design optimization of VAWT airfoil can be primary decomposed into the terms of thrust force and pitching moment, another multi-objective optimization of thrust/pitching moment coefficients is also performed for detailed discussions about the obtained optimal airfoil. The obtained optimal airfoil achieves a significant improvement in the aerodynamic performance compared with an existing airfoil. ANOVA analysis is also performed on the Kriging model to extract more engineering design information of the VAWT airfoil. Finally, expensive unsteady CFD simulations are performed for the obtained airfoils, that take into account unsteady flow interactions between three blade airfoils. The results of the unsteady CFD simulations validate the effectiveness of the proposed aerodynamic shape optimization approach of VAWT airfoil.