**1. Introduction**

The aerodynamic behaviour caused by the effect of crosswinds is one of the most serious challenges concerning the safety of high-speed trains [1–3]. The existence of crosswind would lead to the high-speed train being accompanied by a rather complicated flow field, that fluctuates both temporally and spatially. As a consequence, the train's aerodynamic properties are affected, and the running safety would be imperilled, especially when the train is through a bridge, the crosswinds become more complicated due to the bridge structure [4, 5]. Thus, the effects of crosswinds on aerodynamic behaviour are crucial.

With the fast growth of high-speed trains, the effect of crosswinds has become more and more prominent [6, 7]. To reduce the effects of crosswind, the typical windproof is widely used. It includes wind barriers and anti-wind open-cut tunnels. Wind barriers are simple and convenient devices, that are utilized in high-speed

tracks at strong crosswinds conditions. In recent years, many researchers have investigated the impact of wind barriers on the aerodynamic characteristics of a high-speed train. Deng et al. [8] numerically studied the windproof performance of wind barriers in the wind-vehicle-bridge system. They found that the wind barrier is exceedingly important and significantly affects the aerodynamic coefficient, flow structure, and traveling safety. Guo et al. [9] assessed the impact of wind barriers on the traveling safety of a high-speed train to crosswinds. They determined that the existence of the wind barriers causes negative effects on the bridge. Gu et al. [10] experimentally and numerically studied the aerodynamic characteristics of a train with various lengths of vertical wind barriers. They found that when the wind barrier length varies, the impact on the train's head is more obvious than on the tail.

Liu et al. [11] numerically studied the aerodynamic behaviour of a high-speed train running through a windbreak region while being buffeted by crosswinds. They found that when the train entered the region under the crosswind, the aerodynamic coefficients change suddenly. Zou et al. [12] performed a numerical simulation to evaluate the effect of wind barriers of a high-speed train on a bridge. In their work, two vertical wind barriers were placed on either sides of the railway. Xiang et al. [13] executed a wind tunnel testing to evaluate the aerodynamic load of a high-speed train. Their findings revealed that a wind barrier of a specific height increases lift. However, it is still indistinct how the inclined angle of the barriers affects the flow pattern around the train and barriers, which benefits the development of high-speed trains. Therefore, the present work seeks to explore the mechanisms of the impacts of barriers inclined angles on the high-speed train and explain the relationships between the barriers with different inclined angles and the train.

For investigating the effects of barriers on the train aerodynamic mechanism, there are four approaches, including analytical method, numerical simulation, field measurement, and wind tunnel test. In the work of Yang et al. [14], the Finite Volume Method (FVM) in ANSYS FLUENT software was used to solve the 3D unstable incompressible Navier-Stokes equations. Catanzaro et al. [15] compared the CFD results and wind-tunnel tests of a high-speed train in a crosswind. They found that the results of the stationary model become more different from the moving model and the environment has a major impact on the train's incoming flow. Wang et al. [16] conducted an experiment work to study the influences of crosswinds on the aerodynamic properties of a high-speed train.

As a recognized and powerful numerical method, the Lattice Boltzmann approach has been widely utilised to simulate fluid flow and heat transfer problems [17, 18]. The Lattice Boltzmann equation was created and developed as a computational alternative to the solving the Navier-Stokes equations of continuum fluid physics [19]. Due to the advantages of LBM, such as its ability to dealing with complicated boundaries, parallelize the algorithm, and incorporating microscopic interactions, it has also been used to model the aerodynamic behaviours of the high-speed train. Mohebbi and Rezvani [20] utilized LBM to investigate the consequences of windbreaks geometry on two-dimensional airflow past a high-speed train. They determined that the performance of windbreak is significantly dependent on its height and edge angle. The LBM was also used by Wang et al. [21] to predict the aerodynamic behaviour of a highspeed train. They concluded that LBM has many advantages compared with the traditional CFD method. In the previous work, the authors [22] assessed the impact of porous shelters alongside a high-speed track on the vehicle's aerodynamic behaviour and the modelling was conducted utilizing the lattice Boltzmann method. The authors *The Influence of Inclined Barriers on Airflow Over a High Speed Train under Crosswind… DOI: http://dx.doi.org/10.5772/intechopen.112751*

have proved that the LBM codes with smaller lattices can provide a reasonable accuracy result.

To the best of the authors' knowledge, the effects of two inclined barriers on the aerodynamic mechanism of a train have never been studied. In the present work, the German Intercity Express (ICE3) high-speed train was focused and a threedimensional numerical model of the train-barrier-crosswind system is adopted to investigate the effect of two inclined barriers on the train's aerodynamic mechanism through the Lattice Boltzmann method. The effect of barrier inclined angle and direction on the velocity, pressure, turbulence intensity, streamlines, and aerodynamic coefficients are investigated.
