On the aerodynamic properties of slotted-flap flow-control devices for wind turbine applications

Wind energy is growing at a fast pace and utility-scale wind turbines growing in size with increasing rotor diameters. To sustain development of up-scaled wind turbines of tomorrow there is a need for innovation in load control methodologies. This thesis research targets an assessment of the aerodynamic properties of airfoil sections specifically intended for wind turbine applications, featuring them with flow-control devices. The use of fractional-chord trailing-edge flaps as slotted-flap devices on aerodynamically active parts of a turbine blade were studied. As modular devices attached externally on existing blade designs, they comfortably form a cost-effective means for active load control with low energy actuation. They also have advantages such as minimal design modifications to the original blade, relatively light-weight device, and lack of retooling of the manufacturing process.;The basis for an aerodynamic study was the NREL-5MW Reference Wind Turbine, which is a well-studied benchmark for large utility-scale wind turbines of today. This dissertation presents numerical results for the aerodynamic properties of two modified airfoil sections used on the blades designed for this turbine, NACA 643-618 and DU 93-W-210. These airfoils in their original configuration are used on the aerodynamically active parts of many contemporary wind turbines. A new set of coefficients defining the aerodynamic characteristics of these airfoils equipped with a fractional-chord trailing-edge flap of Clark Y profile are presented here. Defining the effects of flaps on airfoil sections specifically intended for wind turbine applications will suffice as a repository of useful aerodynamic data for a wider research community to develop new blade designs and load mitigation approaches for wind turbine rotors.