Numerical research on effect of transition on aerodynamic performance of wind turbine blade with vortex generators

Abstract

In the inner part of a large wind turbine blade, a thick airfoil is commonly used to guarantee structural integrity and assists the blade to run more easily at high angles of attack in variable winds; its local Reynolds number is less than 3.0 × 106. Under these conditions, flow separation and transitions easily occur and exert great impact on blade performance. Vortex generators (VGs) are effective devices used to control flow separation and alter stalling conditions, and hence have been employed in the inner part of the blade in some wind turbines. To clearly understand the aerodynamic performance of a blade with VGs, a blade section employing the thick DU91-W2-250 airfoil and five pairs of VGs is modeled using the transition model. The results for both the coefficient of lift and drag–lift ratio predicted by the transition model are compared with those obtained from the k-ω shear stress transport model and experiment. The comparison demonstrates that the transition model has much higher accuracy. The effects of transition on the distributions of flow stream, shear stress, and vortices from the VGs are investigated and more useful rules are obtained through a comparison between the results of the transition model and the turbulence model at four angles of attack: 5°, 12°, 16°, and 20°.