A Unique Test Facility for the Experimental Investigation of the Unsteady Aerodynamics of Wind Tunnel Models Under Pitching Motion at Large Amplitudes and High Reynolds Numbers in the High-Pressure Wind Tunnel

Kurzfassung

The influence of the Reynolds number is for certain aeroelastic and aerodynamic phenomena of high significance, in particular in case the flow is dominated by massive separation areas, like bluff body flows. These kind of flows are broadly represented in our daily life, e.g. in the aerospace industry (landing gear doors, propeller blades of single turboprops or piston twin aircrafts during start or landing), civil engineering (overhead transmission lines, bridge decks, pillars of semi-submerged offshore structures) or in wind engineering (blade-tower interactions and deep dynamic stall). The structures are subject to fluid-structure interactions, which in many cases lead to flow-induced vibrations like galloping or flutter and, in case of large amplitudes, even to damage of parts or failure of the complete construction. In order to minimize or even suppress those undesired flow-induced vibrations, it is of great concern to understand in detail the unsteady three-dimensional flow characteristics around these structures. For that purpose a new test section was designed and built to be implemented inside the High-Pressure Wind Tunnel Gottingen, a test facility in which the air pressure can be increased up to 100 bar to simulate realistic flow conditions at Reynolds numbers up to 10 million. The test section consists out of two torque motors that are used to either set and maintain a steady angle of incidence within 0 and 359deg or to let the two-dimensional wind tunnel model perform a forced pitching motion with amplitudes of up to +/- 15deg at maximum pitching frequencies of 15 Hz (i.e. reduced frequencies of k ~ 1) around a certain steady angle of incidence. A piezo-electric balance is placed at both ends of the model outside the test section in order to obtain the unsteady aerodynamic lift and drag forces and pitching moment The coupled fluid-structure responses of the wind tunnel models, having a span of 600 mm and a maximum chord length of 120 mm, can be obtained by a combination of the balances and up to 60 unsteady pressure sensors and accelerometers integrated in the model.