Road Vehicle Testing at High Reynolds Numbers in the Cryogenic Wind Tunnel Cologne DNW-KKK

To address the aerodynamic problems of new generation high speed trains, force measurement and PIV tests were performed on a high speed train model in the Cryogenic Wind Tunnel Cologne (DNW-KKK) at high Reynolds numbers. The Cryogenic Wind Tunnel Cologne is a low speed wind tunnel. By cooling the test gas down to 100K the Reynolds number can be raised by a factor of 5.5. The train model is connected to the support via girth gears, isolation plates, balance and angle of attack drive. A separate splitter plate is used to reduce the influence of the tunnel boundary layer. Test results showed that the repeatability of the force measuring system in DNW-KKK is high both at ambient and cryogenic operational mode. A PIV setup was used to investigate the vortex formed at the lee side of the train. The laser light sheet can be adjusted by means of a movable mirror and traversing equipment, so that the vortices at different sections and different yawing angles of the model can be measured. The PIV camera is located in a heated box and can be focused remotely. With these steps the PIV measurement can be performed down to 100K.