Dynamic stall control of the wind turbine airfoil via single-row and double-row passive vortex generators

Abstract

Passive vortex generators (VGs) have been extensively used on wind turbine airfoils to delay the onset of static stall and improve the aerodynamic performance. Dynamic stall control via passive VGs, however, is still poorly understood. Therefore, this paper presents unsteady RANS simulations of the dynamic stall of the NREL S809 airfoil with and without rectangular VGs. The transitional SST k-ω model is used with VGs fully resolved. VGs are found to delay the onset of dynamic stall and greatly elevate the maximum lift coefficient by almost 40%. For single-row VGs, chordwise installation significantly changes the post-stall behavior and the flow reattachment. VGs at 15% c performs better concerning suppressing the separated flow and reducing the aerodynamic hysteresis. For double-row VGs, the second row of VGs strongly accelerates the near-wall flow and further eliminates the flow separation. This favorably leads to 57% and 39% decreases in the hysteresis intensities of lift and pitching moment coefficients, respectively. These findings suggest that passive VGs are highly promising in controlling the dynamic stall of the wind turbine airfoil.