Dynamic Analysis of Moving Train Wake Vortex Under Different Infrastructure Scenarios Based on Modal Decomposition

Vortex shedding at the tail of a high-speed train changes the aerodynamic characteristics of the train, which affects the safety and stability of train operation. This paper takes CR400AF as the research object, and uses dynamic monitoring points to realize the whole process monitoring of the flow field at the tail of the train running in open air and in tunnel for the first time. The wake of the train in different infrastructure scenarios is analyzed by the proper orthogonal decomposition method. The study found that the wake vortex structure is quite different when the train runs in different scenarios, and the turbulent kinetic energy intensity of the wake in tunnel is higher than that of the open air running. Modal decomposition method can identify flow structures that have a large impact on train aerodynamics. Through frequency analysis, it is found that the modal frequency obtained from the decomposition is higher when running in open air than when running in tunnel. With the increase of train speed, the modal strouhal number increases when the train is running in open air, and decreases when the train runs in tunnel. After the train enters the tunnel, the reverse movement of the air around the train body suppresses the development and separation of the boundary layer, which is the main reason for the low frequency of wake vortex shedding in tunnel. The stability of the train running in tunnel is worse than that when running in open air, which is closely related to the more complex flow structure around the car body and the drastic change of aerodynamic force when running in the tunnel.

Automated summary

This paper investigates the effect of vortex shedding on the aerodynamic characteristics of a high-speed train, which in turn affects its safety and stability. The flow field at the tail of the train running in open air and in tunnel is monitored using dynamic monitoring points. Proper orthogonal decomposition analysis is performed to analyze the wake vortex structure under different infrastructure scenarios. The study finds that the wake vortex structure is significantly different between different scenarios, with higher turbulent kinetic energy intensity in the tunnel. Modal decomposition method can identify important flow structures affecting train aerodynamics. Frequency analysis reveals that the modal frequency is higher when running in open air and increases with train speed, while it decreases when running in the tunnel. The stability of the train running in tunnel is worse than that in open air, mainly due to the more complex flow structure around the car body and the drastic change of aerodynamic force in the tunnel.