Particle Image Velocimetry of the underfloor flow of generic high-speed train models in a water towing tank

Abstract

The underfloor flow field of three different 1:50 generic high-speed train models hauled through a water towing tank at a speed of 4 m/s (Reynolds number = 0.24 Mio) over a smooth, rough and a ground with sleepers were measured by means of two component Particle Image Velocimetry. The reference train model consisting of four cars, features inter-car gaps and two bogies per car. These features are removed and all gaps are closed for the smooth train configuration, while the rough train configuration reflects all gaps but no bogies. The lowest underfloor flow velocities and velocity gradients at the ground are observed for the smooth train model on the ground with sleepers. Further the measurements reveal that any additional irregularity of the underbody leads to accelerated flow regions in the otherwise Couette-like flow which increase the possibility of ballast flight. Therefore it is concluded that a smooth underbody can lower the risk of ballast flight. The results obtained for the reference train model are compared to those of a full scale measurement. It is shown that the results of the water towing tank experiments with the down-scaled train model reflect the main characteristics of the underfloor flow of the full scale measurements.