Aeroelastic wind tunnel experiments at the DLR: from cylinder flows over laminar wings up to space

Abstract

Founded in 1957, the Institute of Aeroelasticity in Göttingen is one of the 17 institutes focusing mainly on aeronautical research within the German Aerospace Center DLR. In our institute we combine experimental and numerical methods to predict aeroelastic phenomena that are the result of the interaction between aerodynamic and structural forces in an airflow. These aeroelastic phenomena do not only occur in the aeronautical and space field, e.g. aircrafts and space vehicles; they are also highly important for the civil engineering (bridges, tall buildings) and the wind power branches. Pertaining to all fields, the consistently present fluid-structure interaction may lead to critical dynamic phenomena and even to the destruction of the complete structure. To experimentally investigate the fluid-structure interaction even at the critical limit, challenging aeroelastic wind tunnel experiments are conducted at high transonic Mach numbers, under high total air pressure and/or at very low temperatures. These experiments mainly take place in the Transonic wind tunnel and High-Pressure wind tunnel in Göttingen and in the Cryogenic wind tunnel and the European Transonic wind tunnel in Cologne. The compiled results provide useful validation data for state-of-the-art numerical simulations, also performed at our institute. Highlights of the major projects from the multifunctional Aeroelastic Wind Tunnel Experimental Group are presented. These include the extensive experimental investigation of the wing-pylon-nacelle interaction in transonic flow; the project „Aerostabil“, in which the flutter behavior of a laminar airfoil was investigated for better physical understanding of the transonic flutter phenomena; the gust response of a laminar airfoil was studied in the „iGREEN“-project; the „IWEX/MEPHISTO“-project, to model the unsteady behavior of the vortex generation on low aspect ratio wings and the project „Panel Flutter“ in which the flutter behavior of a panel of a launcher’s upper stage is analyzed. In the High-Pressure Wind tunnel in Göttingen the air can be pressurized up to 100 bars to simulate Reynolds numbers as high as 12 million - close to full-scale. Here, fundamental research is mostly performed to investigate for example the influence of the Reynolds number on smooth and rough circular cylinder flows (e.g. telecommunication towers, bridge cables, antennas, etc.) and on the flow behavior around a rectangular cylinder with 1:5 aspect ratio. The research in this wind tunnel now starts to shift more and more in the direction of wind energy, in particular the aerodynamic behavior of wind turbine blades as function of the free stream Reynolds number and angle of incidence as well as their dynamic stall behavior.