The Impact of Bogie Sections on the Wake Dynamics of a High-Speed Train

The impact of bogie sections on the wake dynamics of a high-speed train (HST) is numerically explored using the improved delayed detached eddy simulation (IDDES). Time-averaged and instantaneous wake flow topology are compared for two underbody configurations: the complex train model (CTM) with bogie sections and the simplified train (STM) with a flat underbody. For both underbody configurations, a pair of counter-rotating half-loop vortices dominates the unsteady wake. Each member of the vortex pair is shed alternately in the wake of the CTM, which is attributed to vortex shedding from the bogie sections. While for the STM, the members of this vortex pair couple and appear simultaneously. The dynamic characteristics of the wake are clarified by using proper orthogonal decomposition (POD) analysis for the IDDES results. The first four POD modes, corresponding to the dominant vortex structures, are analysed in detail, which confirms the significant impact of bogie sections on the wake dynamics of a HST.