Numerical investigation on the aerodynamic characteristics of high-speed train under turbulent crosswind

Abstract

Increasing velocity combined with decreasing mass of modern high-speed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of highspeed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE-2 high-speed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incompressible form of the unsteady Reynolds-averaged NavierStokes (RANS) equations combined with the realizable k-epsilon turbulence model. Important aerodynamic coefficients such as the side force and rolling moment coefficients were calculated for yaw angles ranging from -30°to 60°and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train's cross-section were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at different locations along its length was computed for yaw angles of 30°and 60°. The computed aerodynamic coefficient outcomes using the realizable k-epsilon turbulence model were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coefficients increase steadily with yaw angle till about 50°before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different crosssections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which leads to the creation of a low-pressure region in the lee ward side of the train causing high side force and roll moment. Generally, this study shows that unsteady CFD-RANS methods combined with an appropriate turbulence model can present an important means of assessing the crucial aerodynamic forces and moments of a high-speed train under strong crosswind conditions.

Effect of the inter-car gap length on the aerodynamic characteristics of a high-speed train

“…As the inter-car gap length affects the flow field and pressure distribution, the train models with several different lengths are established. Ten different lengths are 5,8,10,15,20,30,40,50,60, and 80 mm. Figure 16 shows four inter-car gaps with different lengths.…”

“…The inter-car gap shown in Figure 1(e) was used in several numerical simulations. [18][19][20][21] It is concluded from the works of Watkins et al, 3 Wilmenson, 4 Kwon et al, 5 and Paul et al 6 that the inter-car gap has a significant effect on the aerodynamic drag of a train. A proper design of the intercar gap can be superior to the modification of the nose shape.…”

Numerical optimisation and experimental validation of divided rail freight brake disc crown

“…The application of CAE in virtual environment is widespread in engineering and includes railway optimisation [2,[5][6][7][8]. A study on the use of CFD to determine aerodynamic forces showed that CFD simulations are very useful for prediction of real properties [9]. Despite the fact that CAE simulations have become widespread, there has been relatively little research on brake discs in rail vehicles.…”

Computational investigation of effects of crosswinds on detailed locomotive geometry with rotating wheels and moving ground plane

“…Most of the work on trains going down the tracks have been done on high speed trains (HST), for example, bullet trains or maglev trains. Some of this computational analysis has been done without rotating wheels (Asress and Svorcan 2014). Some simulations describing the shape of the slipstream use detached eddy simulation or large eddy simulation (Baker 2014;Flynn et al 2014).…”

“…Another issue with how trains have been studied is most of the CFD simulations are done on highly defeatured models, i.e., the bogies have been simplified to a rectangle with cylindrical wheels (Asress and Svorcan 2014;Flynn et al 2014;Östh and Krajnović 2014).…”