Underfloor flow measurements of a 1:50 generic high-speed train-set by means of high-speed PIV in a water towing tank

Abstract

Two-component high-speed particle image velocimetry measurements of the underfloor flow field in the rail symmetry-line of three different 1:50 high-speed train configurations hauled over a smooth ground, a rough ground and a ground with sleepers were conducted in a water towing tank at a train speed of 4 m/s (Reynolds number=0.25•106). The high-speed train configurations were realised by changing the underfloor roughness of the 4-unit generic high-speed train model (two end-cars and two mid-cars). The reference train model represents a conventional non-articulated high-speed train with inter-car gaps and two bogies per car. A completely smooth underbelly was achieved by removing the bogies and covering all the gaps as the third train configuration without bogies and all gaps left open reflects a rough train underbelly. The results revealed that any underfloor irregularities such as bogies, bogie housings, inter-car gaps or cavities accelerates the underfloor flow concluding that a smooth train underfloor decreases the chance of ballast flight. Furthermore, the risk of ballast flight is lower for a trackbed with monoblock sleepers and a lowered ballast level than for a trackbed with bi-block sleepers.