Investigation of Reynolds Number Effects in High-Speed Train Wind Tunnel Testing using Temperature-Sensitive Paint

Abstract

The method of Temperature-Sensitive Paint (TSP) is used to visualize wall shear-stress patterns of high-speed train models subject to crosswind in the Göttingen cross-wind facility SWG and the kryo wind tunnel Cologne (KKK). An ICE3- and a NGT2-model (Next Generation Train) is investigated with respect to laminar-turbulent boundary layer transition, separation lines and vortex signatures on the leeward side of the train's nose. It is shown, that in low-speed wind tunnel testing as given in SWG and KKK (Re range: 0.3 Mio < Re < 1 Mio for a 1:25 train model) laminar regions exist, which are not to be expected on a real train. Thus, laminar-turbulent transition occurs and the extend of laminar regions or appearance of separation bubbles is dependant on Reynolds number, yaw angle, body shape and sharpness of edges. The influence of these Reynolds number effects on the results of force measurements in different wind tunnels and/or for different Reynolds numbers in one and the same wind tunnel is discussed.