Study On Aerodynamic Characteristics Of High Speed Trains Passing By Each Other

Nowadays, the development of railway industry is already running peak levels in our country, with the increase of the train speed, the problems caused by the train aerodynamics are becoming more and more prominent. Especially the pressure transients generated by the intersection of two vehicles shock, which causing a serious impact on the safety and comfort of the train. Although we have got some research achievements on the aerodynamic characteristics, however, the study on train aerodynamic force, especially the cause of the aerodynamic moment is still not in depth. In addition, the research on aerodynamic characteristics while in cutting and semi cutting conditions is blank too. In order to achieve the comfortable, high-speed and safe operation of the train, it is necessary to do more detailed research on the aerodynamic characteristics of the trains passing by each other.According to the aerodynamic problems caused by trains passing, the CRH2 train was taken as an example in this paper, the software ICEM was used to create a grid for the existing model of the train. Based on the three-dimensional unsteady incompressible Navier-Stokes equation and k-ε two equation turbulence model, the finite volume method and moving mesh was used to simulate the aerodynamic characteristics and pressure distribution by the large fluid analysis software Fluent, in addition, the aerodynamic characteristics of trains passing by each other in the embankment, cutting and semi cutting and under crosswind conditions were also studied.Calculation results show that:(1) While there is no crosswind affects, the trains’ maximum positive pressure area is located at the tip of nose; if affected by the crosswind, the maximum positive pressure area will locate in the tip to the location of the windward side.(2) The alteration of aerodynamic force and aerodynamic moment, are mainly affected by the positive and negative pressure zone, and the aerodynamic characteristics of the train will be deteriorated when in crosswind.(3) The longitudinal pressure gradient of the train growing with the axis increases; and the transverse pressure distribution along the train is pass side>car bottom>car roof> non-pass side.(4) In the process of train passing by each other with different speed, the slowly car will get a greater impact, and the changes of aerodynamic force mainly influenced by the speed of opposite direction and overlying speed of the two cars.(5) While the trains passing each other in the embankment, cutting and semi cutting, the aerodynamic characteristics generated is significantly different to vehicles passing by each other on the ground.