Effects of Different Train Speeds on the Dynamics of Wake Flow of a Full-Scaled High-Speed Train

Abstract

The wake flow of high-speed train is an extremely complicated three-dimensional unsteady flow due to the vortices generated and shed from the trailing car periodically, which has great influence on the aerodynamic performance of the trailing car, such as comfortable performance and safety. In this paper, the dynamic characteristics of trailing vortices of a full-scaled model of CRH380A high-speed trains, consisting of a locomotive, a middle car and a trailing car, at different speeds is studied with delayed-detached eddy simulation (DDES). Two large helical vortices exist in the wake flow field and move sinusoidally and anti-symmetrically. As the speed increases, the ground effect on the wake flow is more obvious, the cores’ height of the trailing vortices from the ground become much higher, and the intensity of the trailing vortices becomes much greater. In addition, the unsteady wake flow field is decomposed by proportional orthogonal decomposition method (POD). It is found that the vertex positions in the same mode shift at different speeds, but the overall spatial structure is similar. The periodicity and corresponding frequencies of different POD modes at different speeds are