Comparative analysis of the slipstream of different nose lengths on two trains passing each other

Abstract

The scenario of high-speed trains (HSTs) passing each other is usually encountered, which causes aerodynamic effects such as high slipstream velocity and strong aerodynamic loads, leading to trackside worker injuries, equipment fatigue damage, and snake-like train motions. This study used a three-dimensional, compressible, improved delayed detached eddy simulation (IDDES) method based on an SST k-ω turbulence model to research the turbulent flow around the train bodies generated by two trains passing each other in the open air. An overset grid method was utilised to tackle the moving boundary problem. The numerical results were firstly verified by comparison with the results of a moving model test. Then, temporal and spatial evolution of the flow field was analysed in detail based on a 4 ​m nose length model. The results show that the process of intersecting has a pronounced effect on the vortices as well as the boundary layer at the bottom of train side. The peaks of three slipstream velocity component profiles decrease as the distances from the centre of the track (COT) and the top of the rail (TOR) increase. Finally, considering three different nose lengths (4 ​m, 7 ​m, and 9 ​m), the differences in the instantaneous flow structures, slipstream profiles, and aerodynamic coefficients were elucidated. The longer nose lengths were found to reduce the scale and strength of the counter-rotating vortices, thereby lowering the maximum slipstream peaks in the wake. The slipstream resultant velocity at trackside height for the 7 ​m nose length case is 22.2% lower and 9.2% higher than the corresponding values for the 4 ​m and 9 ​m nose length cases, respectively. The side force coefficient is also influenced by the nose length, with the stronger effect being exerted on the head car and tail car than on the middle car.