Measuring drag on an airfoil section in atmospheric flow with a wake rake

During the last years, DTU Wind Energy has developed an outdoor rotating test rig in order to bridge the gap between steady wind tunnel testing and full-scale turbine measurements. The rotating test rig makes it possible to test airfoil sections in a rotating reference frame with turbulent inflow. In a number of projects the rotating test rig has also proven to be a good tool in testing and validating new concepts, such as active flaps.

In the Induflap 2 project it was decided to upgrade the rotating test rig with a wake rake in order to measure the viscous drag together with the pressure drag. A detailed comparison of the airfoil polars in atmospheric inflow and in low turbulent steady wind tunnel flow can then be carried out.