A Preliminary Large Eddy Simulation Research On The External Flow Of High-speed Train Inside Tunnel

External flow around bluff bodies is a classic subject of fluid mechanics. In terms of the external flow of the high-speed trains inside tunnels, it couples the complex shaped bluff bodies’external flow with the wall turbulence, which is different from the common external flows. When high-speed trains pass through the tunnel from the open air, the flow field will be affected, resulting in an intense variation of the aerodynamic characteristics and a lateral vibration of the train. This phenomenon can endanger the cruising safety, so the research of the external flow has a practical significance on it.Large eddy simulation is a new type of turbulence numerical simulation method, it has a relative higher solution precision while consuming less computing resources, and it has been widely used in the turbulence research.In this article, a research on the external flow characteristics of high-speed trains inside tunnels has been carried out, combining the CFD commercial code STAR-CD, the large eddy simulation method and the multi-block meshing technology.At first, the LES research on the flow field of Germany high-speed train ICE2cruising inside a double track tunnel was carried out with different numerical solution method. The solution result is coincided with the reference, validating the feasibility of our research method. The unsteady flow structure in the tunnel was clearly shown by the pressure contour and velocity vector plot of the typical cross-section. The transient characteristics of the flow field outside the train can be revealed from the instantaneous pressure coefficient Cp graph. From the longitudinal vorticity contour plot of the typical cross-section, the vortex can be seen generated on the conjunction part of the head and straight body, gradually developing along the straight body, until fully developed on the conjunction part of the tail and straight body. The flow separation nearby the tail can be shown by the pressure contour plot and iso-lines of longitudinal vorticity.After that, the research model was replaced by the domestic high-speed train CRH380A, and the large eddy simulation was carried out for the external flow characteristics. The total quantity of the computational grid is decreased by the multi-block meshing technology. The mechanics of lateral vibration was preliminarily revealed by the analysis of the aerodynamic force on the high-speed train.