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Aeroelastic Wind-tunnel experiments

Aeroelasticity deals with the interaction of elastic structures in an air stream and its aerodynamic loads as well as the impact of this interaction on the

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design of the structure. Aeroelastic phenomena do not only occur on aircraft and space vehicles but also on large buildings. Pertaining to all fields, the interaction of aerodynamic and structural forces may lead to critical static or dynamic phenomena.

This aeroelastic wind-tunnel-experiments group is committed to the planning, realisation and analysis of challenging experiments in wind tunnels in order to investigate the Fluid-Structure Interaction at the limit of aerodynamic areas with high transonic speeds and/or detached flows. The compiled results provide validation data in addition to physically reasonable indication of the problem-modeling of the observed phenomena.
An example are the experiments in the project "Aerostabil", which expanded the physical understanding of transonic flutter, particularly the nonlinear effects. The interaction of wing and engine nacelle was the subject of extensive experimental investigations as well as the dynamic separation (dynamic stall) at helicopters rotors.
The goal is always to derive innovative technical solutions from the gained physical understanding. Some work has already resulted in successful patent applications.
Many of our projects are examined in international co-operating teams.
Besides the scientific work, the group deals with the development of piezoelectric balances and the use of innovative optical measurement techniques.

The group has three different test setups for aeroelastic experiments at airspeeds up to the transonic regime available. The first setup is designed for investigating flutter of 2-D models which are symmetrically and elastically suspended on both sides from blade and cross-springs. The test setup allows fundamental experiments in the state of flutter or on active flutter control systems as well as on passive damper systems.
By use of the second test setup, the effects of forced pitch motions of a wind-tunnel model on its aerodynamics can be investigated. It has been successfully used for testing helicopter rotor blades equipped with piezo-electrically driven flaps for dynamic stall control. This test setup can be upgraded with a torsional degree of freedom in order to investigate free pitch oscillations of the model.
By means of the third test setup torsional vibration tests of rigid half-wing models as well as free oscillations of elastic half-wing models can be conducted.
For acquiring steady and unsteady experimental data, the group owns a special data acquisition system. This system is capable of sampling the signals

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of 640 channels simultaneously, up to 200kHz per channel, with a 24 bit resolution. Complementary time resolved optical deformation measurement techniques can be offered. These techniques can be applied time synchronized to the above mentioned data acquisition system.
The group is also experienced in providing complex aeroelastic wind tunnel models. Namely such which are scaled elastically and dynamically similar and are equipped with miniature pressure sensors and miniature accelerometers.