不同转向架构型对高速列车列车风及非定常尾迹的影响

Impact of different bogie configuations on slipstream and unsteady wake of a high-speed train

随着高速列车速度的不断提升,列车尾部非定常尾迹引起的列车风安全问题越来越凸显。为探究转向架构型对列车风和非定常尾迹的影响,以CRH3两节编组的高速列车缩比模型为研究对象,采用增强型延迟分离涡模拟对三种不同转向架构型,即不对称转向架、对称转向架和无转向架,进行列车非定常流动的数值模拟研究。通过对比分析列车风时均和脉动速度分布以及尾迹流场结构,同时采用SPOD (Spectral Proper Orthogonal Decomposition)方法对非定常尾迹进行模态分解和流场重构。研究结果表明:三种转向架构型的列车尾迹均是由一对反向旋转的半环形流向交替涡脱落主导;相对于对称转向架构型,不对称转向架底部带来的扰动与尾迹流向涡对的相互作用更强,增加流向交替涡脱落的强度,继而诱导出更高的列车风脉动速度;无转向架的转向架舱及其后缘流动分离产生的大尺度涡脱落导致尾迹流向涡对展向范围更宽,列车风时均速度最大;SPOD方法通过增强相关矩阵的对角相似性,使得提取的主导模态配对性增强,模态峰值频率更加凸显,模态空间分布更加清晰。以上研究结果对高速列车转向架的设计优化有一定参考意义,显示了SPOD方法在高速列车非定常尾迹分析中的优势。

With the increasing speed of the high-speed train(HST), the safety problem associated with the slipstream caused by the unsteady wake of HST is becoming more and more prominent. In order to explore the impact of bogie configurations on the slipstream and unsteady wake of HST, a scaled two-car HST model CRH3with three different bogie configurations i.e. asymmetric bogies(AB), symmetric bogies(SB) and without bogies but empty cavities(WoB) is numerically simulated using the improved delayed detached eddy simulation(IDDES). Profiles of the time-averaged and root mean square of the slipstream velocity as well as the unsteady wake structures are comparatively analyzed. In addition, the spectral proper orthogonal decomposition(SPOD)method is used for the mode decomposition and the wake flow reconstruction. The results show that a pair of counter-rotating half-loop streamwise vortices shedding alternatively dominates the unsteady wake for all the three bogie configurations. Compared to the SB configuration, disturbances induced by the AB configuration can interact more strongly with the streamwise vortex pair in the wake region, increasing the intensity of alternative vortex shedding and inducing a larger fluctuation of the slipstream velocity. For the WoB configuration, largescale vortices separated from the bogie cavity and trailing edge result in a wider wake in the spanwise direction and the largest time-averaged slipstream velocity. Furthermore, by enhancing the diagonal similarity of the correlation matrix, SPOD can enhance the pairing of dominant modes, highlight modal peak frequencies and make modal spatial distribution clearer. The above research findings have a certain significance for the optimal design of bogies for HST, and show the advantages of SPOD in analyzing the unsteady wake of HST.