Numerical investigation of the aerodynamic characteristics of high-speed trains of different lengths under crosswind with or without windbreaks

Jiqiang Niu,Dan Zhou,Xifeng Liang

doi:10.1080/19942060.2017.1390786

Abstract

ABSTRACTThe focus of this study was the influence of the length of a train on its aerodynamic performance, with and without wind break walls, under a crosswind. The improvement in the train’s aerodynamic performance due to a wind break wall was also analyzed. Aerodynamic coefficients such as the drag force and lateral force were obtained for trains of different lengths using a numerical simulation. A delayed detached eddy simulation based on the shear-stress transport κ–ω turbulent model was used in Fluent 14.0 to simulate the unsteady aerodynamic performances of trains of different lengths under a crosswind. Through a comparison and analysis of the simulation results, the effects of the train length on the forces, pressure, and flow structure around the train were studied, along with the influence of a wind break wall on trains of different lengths. The results showed that the effects on the forces, pressure, and flow structure were focused in the region around the train tail. Furthermore, it was found that a wind break wall could improve the aerodynamic characteristics of a train under a crosswind, but amplified the influence of the train length on the aerodynamic performance of the train tail. These research results provide useful guidance for train operations under a crosswind.

Highlights

The flow around a high-speed train is in a highly unsteady state, and vortex shedding from the train often occurs (Zhang, Li, Tian, Gao, & Sheridan, 2016)
The windbreaks increased the Standard deviation (SD) values of Cd and Cl for most parts of the train, which meant the windbreaks exacerbated the fluctuations of Cd and Cl for most parts of the train, especially for the train’s tail
Without the wind break wall, increasing the train length increased the drag on the tail car but decreased the lateral force

Summary

Introduction

The flow around a high-speed train is in a highly unsteady state, and vortex shedding from the train often occurs (Zhang, Li, Tian, Gao, & Sheridan, 2016). This phenomenon is especially significant under a crosswind (Hemida, Krajnovic, & Davidson, 2005). With the rapid development of computers, some researchers, including Xi, Mao, Gao, and Yang (2014), Hemida and Krajnović (2010), Östh and Krajnović (2014), and Ashton and Revell (2015), have studied the unsteady aerodynamic performance of a train under a crosswind using large eddy simulation (LES), detached eddy simulation (DES), and delayed detached eddy simulation (DDES)

Methods

Results

Conclusion