The design of rotor blades is based on information about aerodynamic phenomena. An important one is fluid-structure interaction (FSI) which describes the interaction between a flexible object (rotor blade) and the surrounding fluid (wind). However, the acquisition of FSI is complex, and only a few practical concepts are known. This paper presents a measurement setup to acquire real information about the FSI of rotating wind turbines in wind tunnel experiments. The setup consists of two optical measurement systems to simultaneously record fluid (PIV system) and deformation (photogrammetry system) information in one global coordinate system. Techniques to combine both systems temporally and spatially are discussed in this paper. Furthermore, the successful application is shown by several experiments. Here, different wind conditions are applied. The experiments show that the new setup can acquire high-quality area-based information about fluid and deformation.

Wind turbines face harsh inflow conditions when operating in the atmospheric boundary layer or in the wake of other wind turbines. The incoming velocity field can change within seconds due to the turbulent structures it contains, resulting in a rapid change of several degrees in the angle of attack for the rotating blade. Aerodynamics are hence rapidly altered, leading to changes of the occurring forces on the rotor. Such dynamic forces cause the blades to twist and bend, accelerating fatigue and reducing the lifetime of a turbine Spinato et al. (2009).