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

Abstract

The 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. ARTICLE HISTORY

The effect of moving train on the aerodynamic performances of train-bridge system with a crosswind

“…When the train body passes the monitored segment at a constant speed, the forces keep relatively stable regardless of a little fluctuation. Referring to previous studies (Niu et al, 2018;Wang et al, 2018a), the variation trend is similar to that of the pressure wave induced by the moving train. When the train travels with a high speed, the air in the front of the head car will be compressed and diffuses around, but the bridge deck can block the diffusing air to change the pressure distribution on the surface.…”

“…There have been many pieces of research to estimate the aerodynamic behaviors of the train under a crosswind environment using the full-scale experiments, scaled wind tunnel tests and CFD simulations CONTACT Nan Zhang nzhang@bjtu.edu.cn (Alonso-Estébanez, Del Coz Díaz, Álvarez Rabanal, & Pascual-Muñoz, 2017;Baker, Jones, Lopez-Calleja, & Munday, 2004;Gallagher et al, 2018;Niu, Zhou, & Liang, 2018;Suzuki, Tanemoto, & Maeda, 2003). In these investigations, usually the train runs on the flat ground or embankment, and the movement of the train is created by means of the resultant velocity V r imposed on a static vehicle, as seen in Figure 1, depending on the train speed V t and incoming wind speed V w with a wind angle of α.…”

“…Besides, for the train-bridge system with a moving vehicle, it is not easy to measure the aerodynamic forces on the bridge. At the same time, with the rapid development of computer technology, the CFD approach is also widely approved and adopted in the studies (Alonso-Estébanez et al, 2017;Mosavi, Shamshirband, Salwana, Chau, & Tah, 2019;Niu et al, 2018;Sun, Song, & An, 2012;Yao, Guo, Sun, & Yang, 2015;Zhang, Yu, Zhang, Wu, & Li, 2019), which can better capture the flow characteristics around train-bridge system and easily obtain the aerodynamics affiliated to the train and bridge, compared with a moving vehicle wind tunnel test and full-scale experiment. At present, the dynamic mesh and sliding mesh method are usually used to present the movement of the train in the simulation.…”

Study on the key structure parameters of a gravity settling chamber based on a flow field simulation

“…In addition, in order to fully solve the airflow near the wall and to capture the separation position of the airflow, eight layers of boundary layer mesh are applied by means of inflation layer, and the growth factor of the mesh height is set as 1.1. For all test cases, the values of y + at the first layer mesh near the wall of are within the range from 30 to 100 (Chen, Liu, Jiang, Guo, & Zhang, 2018;Chen, Liu, Zhou, & Niu, 2017;Guo, Liu, Chen, Xie, & Jiang, 2018;Niu, Liang, Xiong, & Liu, 2016;Niu, Zhou, & Liang, 2018). Figure 3 shows the medium mesh of the test case 3 when the dust is accumulated on the floor of the box.…”

Time-resolved aerodynamic loads on high-speed trains during running on a tunnel–bridge–tunnel infrastructure under crosswind

“…For example, Chen, Gao, and Zhu (2016) investigated the transient flow field and aerodynamic coefficients when an HST runs on the bridge under crosswinds. Niu, Zhou, and Liang (2018) investigated the transient aerodynamic characteristics of HSTS when running on flat ground with or without windbreaks. Meanwhile, Chen, Liu, Zhou, and Niu (2017) investigated the effects of ambient wind on transient aerodynamic coefficients when the train runs inside a tunnel.…”