Flow-induced instability of wind turbine blades

Abstract

With the increasing size of offshore wind turbine rotors, the design criteria used for the blades may also evolve. Current offshore technology utilizes three relatively stiff blades in an upwind configuration. With the goal of minimizing mass, there is an interest in lightweight rotors that instead utilize two flexible blades oriented downwind. These design possibilities necessitate a better understating of the fundamental behavior of such flexible blades. In the current work, the dynamic instability of flexible wind turbine blades is studied using experimental studies and supported by numerical stability analysis. For the experimental component of the work, the blades are designed using relatively thin, low Reynolds number airfoils and built using rapid-prototyping methods with a flexible material. A numerical model is also derived to predict the onset of dynamic flow-induced instability for the designed blades. The experimental and numerical findings are then compared.