The Große Wasserkanal Braunschweig (Large Watertunnel Braunschweig) is a joint project of the ISM and the Institute of Jet Propulsion and Turbomachinery. Designed as a closed-circuit tunnel it is used for research on high-lift configurations, fan-intakes, aircraft configurations (incl. wake vortices) and interior fan flows. The calculated weigth is 120 tons including 60 tons of water. In combination with the low viscosity of water (factor 15 in comparison to air), which can be further controlled by heating, Reynolds-numbers of up to 2.5x106 on typical airfoils (c=0.4m) are possible. To avoid cavitation on tested models and in the pump the tunnel can be pressurized to twice the atmospheric pressure. The low flow velocity is a major advantage for precise time-resolved field-measuring techniques (especially PIV) at these high Reynolds numbers.
The test section is completely made from stainless steel. The main frame contains several different wall segments, all interchangeable. In the basic layout one third of the segments is made of security glass to allow the use of optical measurement techniques, especially PIV. One sidewindow is designed as door for easy access to the testsection.
The basic instrumentation of the tunnel contains sensors to measure the flow velocity in the test section, several temperature sensors to detect layering and fill level detectors to control filling and dumping. The tunnel will be prepared for automated speed and Reynolds number control. A modular pressurelogger with 64 channels has been built for scanning pressure distributions of airfoil models. Further extensions of the measuring equipment will be installed according to planned projects. For easy visualization of the flow a constant laser is available.