基于POD分解的高速列车尾流动力学特性研究

The wake field of high-speed train is a complicated turbulent area characterized by periodical generation and shedding of vortices with different intensities, which causes ride discomfort, instability and unsafety of the train. In this paper, based on the 1:1 train model of CRH380A with three carriage consist, the dynamic characteristics of trailing vortices at different speeds from 200 to 450 km/h were studied by the IDDES method. In addition, the strong unsteady wake flows of the train were order-reduced and decomposed by the energy-based POD method to extract the important coherent structures and their main laws in the temporal evolution processes. The physical meaning of some important POD modes of each order in the wake flow was analyzed as well. Through the comparative analysis of the characteristics of the flow field, including POD modal structures and modal frequencies at different train speed. It is found that the dimensionless frequencies of vortex shedding are equal to St≈0.15 at different train speeds, which leads to the conclusion that the frequencies of vortex shedding are proportional to the train speeds in the wake flows of high-speed trains. The POD method is proved to be effective in the analysis of the complex wake flows, and the research results in this paper provide references for the aerodynamic optimization design of the trailing car.