Pitch test rig for the transonic wind tunnel Göttingen (TWG)
The Institute operates a pitch test rig (NVS) to demonstrate forced motion. It consists of a symmetrical arrangement of a two-sided hydraulic drive. A 2-D aerofoil model can be clamped between the sections and excited to perform harmonic pitching oscillation. The actuators operate with extreme precision to achieve very exact, harmonic movements with pitch amplitudes of just 0.05 degrees. These low amplitudes are necessary, for instance to determine dynamic derivatives during transonic angle of attack velocities in such a way that they are rendered comparable with the results of linear models in simulation.
Simple 2-D aerofoil models and more complex aerofoil models with trailing edge flaps are analysed in the NVS. Helicopter rotor segments can even be measured in a scale of 1:1, and simulations can be performed with realistic frequencies on cyclic pitch motions through to dynamic stall.
Further development for 3D half models clamped on one side
An upgrade of the setup also permits analysis of 3-D half models clamped in on one side – for instance UAV structures and helicopter blade tips. What makes this system special is that a large section of the wind tunnel wall can also be moved similar to a turntable, thus ensuring that, despite external drive and shaft, there is no gap between the wall of the wind tunnel and the model. The modular structure ensures that vital parts of the NVS, such as hydraulics, bearings and piezoelectric sensors, can be used in both configurations.
Pitch test rig with an UAV modell
Schematic representation of the pitching test rig with an UAV model clamped on one side.
Pitch test rig for the Göttingen high-pressure wind tunnel (HDG)
The questions of unsteady aerodynamics are also becoming more and more important when it comes to the flow around buildings and wind turbines: In recent years, we have seen increased research and industrial interest in such measurements on the pillars of oil drilling platforms and wind turbines. Since research in these subject areas has been very successful in the HDG with realistic Reynolds numbers for decades, it made sense to develop and implement a corresponding experimental setup for harmonic forced pitching oscillations.
Pitch test rig for the Göttingen high-pressure wind tunnel (HDG)
