The effect of Reynolds number on the unsteady wake of a high-speed train

Abstract

Detached Eddy Simulation (DES) has been used to investigate the effect of the Reynolds number on the wake of a high-speed train in the range from 5.2 ​× ​105 to 2.2 ​× ​107. Then, the characteristics of vortex structure, streamlines distribution, velocity characteristics, and pressure characteristics in the wake region of the high-speed train at five Reynolds numbers are studied. The results show that with the increase of the Reynolds number, some small-scale vortices emerge in the wake region of the high-speed train, which increases the complexity of the wake vortex structure, but the large-scale vortex structure has not changed significantly. The separation lines and vortices distributed on the train surface, and the characteristics of the pressure distribution in the wake region do not change considerably at different Reynolds numbers. The frequency of the vortex shedding from the train based on Strouhal number is approximately a constant at five Reynolds numbers, and the phenomenon and mechanism of the flow in the wake region are almost the same within the range of Reynolds number selected in this study. With the increase of the Reynolds number, the fluctuation degree of the velocity and pressure, and the vorticity in the wake region increase substantially.