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On the scale size of the aerodynamic characteristics of a high-speed train
Author(s): Cheng Chang, Tian Li, Deng Qin, J.Y. Zhang
Keywords: computational fluid dynamics, scale size, high-speed train, aerodynamics
In the wind tunnel tests of trains, the scale size changes the Reynolds number of trains, which may affect the aerodynamic characteristics of the train. Based on computational fluid dynamics (CFD), numerical models of train aerodynamics with five different scale sizes are established. 5 different scale sizes are λ=1/1, 1/2, 1/8, 1/16 and 1/25, respectively, and the aerodynamic characteristics of trains running in the open-air with different scale sizes are numerically simulated. The results show that the pressure drag coefficient and pressure lift coefficient of trains tend to decrease with the decrease of the scale size. Compared with the full-size train, the pressure drag coefficient of the 1/25th scaled train is less by 14.4%, and the pressure lift coefficients of head, middle and tail cars are less by 22.2%, 16.4% and 4.5%, respectively. Meanwhile, the pressure lift coefficients are barely affected by the scale size. The scale size affects the velocity gradient near the train surface as well as the location of flow separation changes. The decrease of the scale size leads to the decrease of Reynolds number and the increase of viscous drag coefficient. When the scale size is 1/25, the viscous drag coefficient of the train is 0.186, which is 48.6% larger than the one of full-size train. In the range of scale size λ between 1/1 and 1/25, the aerodynamic drag coefficient of the head car, middle car and tail car increase with the decrease of scale size, and the difference in the aerodynamic drag coefficient of the train is 12.9%. In addition, the train’s aerodynamic lift coefficient shows an increasing trend with the decrease of scale size.

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.