Recovery of lost performance due to premature transition using active flow control

This paper describes an experimental study aimed at recovering lost performance of a thick, turbine blade airfoil due to degraded surface quality. Since wind turbines are designed to operate for decades, it is expected that the blades' surface will be damaged due to environmental effects. This process will promote early transition to turbulent flow leading to premature boundary layer separation. The effects on the turbine performance could be devastating. Active flow control of boundary layer separation is a known remedy to boundary layer separation. Here we use up to three rows of "synthetic jets" coupled with an array of time resolved hot film and pressure sensors to estimate the flow state and recover the clean turbine blade performance. The energetic aspects of the overall system efficiency are also considered. It was found that the AFC actuators significantly increase the net energy harvesting capability of the contaminated wind turbine blade.