Impact of ground and wheel boundary conditions on numerical simulation of the high-speed train aerodynamic performance

In this paper, the aerodynamic performance of a high speed train with moving ground and rotating wheels (MG&RW) conditions has been investigated using Computational Fluid Dynamic (CFD). The numerical simulations under the condition of stationary ground and moving ground are also compared and discussed. To validate the accuracy of the mesh resolution and methodology, the CFD results are compared with the wind tunnel test results. The aerodynamic forces, unsteady and time average flow fields around the high-speed train are analyzed. The main aim of this study is to investigate how the moving ground and wheel conditions influence the numerical simulation results. The moving ground condition eliminates the effects of boundary layers of ground and rail track, which results in the velocity under the train being faster than in the stationary ground condition. As a result, the drag of every bogie and the pressure on the bottom surface calculated under moving ground conditions is found to be higher than that under the stationary ground condition. The wheel rotation boundary condition has little effect on the force distribution on the bottom surface of the train. However, at the bogie regions, it increases the velocity of airflow around and behind the wheel, causing a change of the pressure distribution and an increment of the wheels' drag. Consequently, the total drag of the train in moving ground with rotating wheel condition is nearly equal to that of condition with the moving ground considered. In addition, the total drag of bogies just takes up 10.4% in all in the stationary ground condition, and it accounts for 12.7% in the moving ground condition and 15.1% in the moving ground with rotating wheel condition.