Investigation of Riblets on the Aerodynamic Performance of Wind Turbine Blades

Effective control of turbulent flow over airfoil surface is important for air vehicles to increase flight efficiency and improve the performance of wind turbines. During the recent decades, extensive studies have demonstrated that engineered surface, such as riblets, can effectively modify the structure of near wall turbulence and reduce the skin-friction over a flat surface. This study seeks to quantify the effects of riblets on improving the aerodynamic performance of a DU-91-W2-250 airfoil with a 0.4 m chord length and 0.8 m span. With the riblet design optimized based on the tested Reynolds number and flow statistics over the suction side of the airfoil, the results highlight that the riblet surface treatment can effectively reduce drag across a wide range of angle of attack, as well as enhancing the lift coefficient under high angle of attacks. Additional measurements for the flow statistics over the riblet surface using micro particle image velocimetry revealed that these microstructures can modify the near-wall turbulent statistics and mitigate the shear stress.