Numerical Investigation on the Flow underneath a High-Speed Train of Six Coaches Marshalled with Different Bogies

The turbulent flow developed underneath a scaled high-speed train of six coaches featured with both conventional and articulated bogies is investigated based on computational fluid dynamics to establish a contribution to train aerodynamics. The numerical simulations are verified against the experimental measurements. It is found that strong unsteady flow develops around the train, particularly at the regions of nose car, leading bogie, articulated bogies, inter-carriage gaps and tail car, due to flow separations and vortex interactions generated around the geometries. High intensity turbulence appears around the nose, bogies, inter-carriage gaps and tail. Strong vortices and high degree of unsteadiness are produced within the flow between the train underbody and the ground, making the flow developed around the bogie regions of high turbulence. Interaction from the inter-car gap leads to a particularly strong vortical flow around the articulated bogie, causing a large slipstream in the regions close to the airspring and a larger drag. Thus the bogie configuration has a noticeable influence on the train underbody flow.