Flow analysis of the deep dynamic stall of wind turbine airfoil with single-row and double-row passive vortex generators

Abstract

This paper aims to understand the influence of vortex generators (VGs) on deep dynamic stall of the NREL S809 airfoil. The fully-resolved URANS method is used to predict aerodynamic responses of the airfoil with both single-row and double-row VGs. On one hand, single-row and double-row VGs are found to attenuate the force fluctuation and postpone the extension of flow separation when the airfoil pitches up. The onset of deep dynamic stall is therefore significantly delayed with the maximum lift coefficient increased beyond 40%. This indicates that VGs are effective in controlling deep dynamic-stall behavior. On the other hand, single-row and double-row VGs are found to make a great difference in aerodynamic responses when the airfoil pitches down. Single-row VGs undermine the torsional aeroelastic stability and have the potential risk of making the airfoil flutter. Double-row VGs can accelerate the flow reattachment effectively, and quickly restore the decreased aerodynamic force near the maximum angle of attack. These findings also imply that deep dynamic stall with VGs becomes highly complicated, because VGs can be fully submerged in separation vortices. In general, double-row VGs perform better than single-row VGs to control deep dynamic stall. This study is believed to assess the VG performance in controlling highly unsteady aerodynamic loads on wind turbines.