基于POD分解的高速列车尾流动力学特性研究

Study of Dynamic Characteristics in Wake Flow of High-speed Train Based on POD

高速列车尾流场是复杂的湍流区域,强度不同的旋涡迅速地生成和脱落,对乘客乘坐舒适性和列车运行稳定性、安全性造成重大影响。以CRH380A三编组列车为研究对象,采用IDDES方法对200~450 km/h速度范围内高速列车尾涡的动力学特性进行了研究;通过POD方法对尾流区的强非定常流动进行了降阶分析,基于能量排序得到了流场演化过程中的重要相干结构和主要规律,并分析了各阶POD模态在尾流场演化中的物理内涵。通过对不同速度下的模态结构数量、模态频率等特性的对比分析发现,尾涡脱落的无量纲频率St≈0.15,这确立了高速列车尾涡脱落频率与运行速度的线性关系。研究结果证明了POD方法在列车复杂尾流场研究中的有效性,并为尾车气动外形优化设计提供了参考依据。

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 CRH380 A 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.