Airfoil-shaped vortex generators for separation control and drag reduction on wind turbine blades

A passive flow control device, Clark-Y airfoil-shaped vortex generator (VG) on NREL Phase VI turbine blade, which has s809 airfoil section, is investigated. Both qualitative oil flow visualization from wind tunnel experiments and quantitative measures of aerodynamic coefficients using steady-state CFD with OpenFOAM are reported. Airfoil-shaped VGs are proposed and compared with traditional rectangular and triangular VGs. The use of airfoil-shaped VGs to delay separation, improving aerodynamic efficiency, inducing local pressure peaks and augmenting vorticity in the flow field are reported in detail. Results show that blades equipped with airfoil-shaped VGs provide a \(5\%\) $5\%$ lift coefficient increase and a \(27.68\%\) $27.68\%$ drag coefficient reduction compared to clean blades at a stall angle of \(\alpha = 11^\circ \) $\alpha ={11}^{\circ }$ . Airfoil-shaped VGs also generate more vorticity downstream compared to conventional VGs, contributing to maximum increase in peak vorticity inducing an additional momentum to the flow to delay separation without significant drag penalty. Thus, airfoil-shaped VGs offer a promising alternative to traditional VG designs.