Thick Airfoils With Blunt Trailing Edge for Wind Turbine Blades

This paper addresses the primary concerns regarding the aerodynamic performance characteristics of thick airfoils with blunt trailing edges (or so-called flatback airfoils) and the utilization of these section shapes in the design of rotor blades for utility-scale wind turbines. Results from wind tunnel and computational fluid dynamic studies demonstrate the favorable impact of the blunt trailing edge on the aerodynamic performance characteristics including higher maximum lift coefficient and reduced sensitivity of lift to premature boundary layer transition. The negative effect of the blunt trailing edge on drag can be partially mitigated through simple trailing edge treatments such as splitter plates. Studies on the effect of these section shapes on wind turbine rotor performance show that at attached flow conditions this inboard blade modification does not adversely affect rotor torque output. Blade system design studies involving the collective optimization of aerodynamic performance, structural strength and weight, and manufacturing complexity demonstrate the overall favorable impact of the flatback concept.