Comparison of different ground simulation systems on the flow around a high-speed train

Abstract

The influence of different ground simulation systems on the air flow around a high-speed train with zero yaw angle is investigated. Force values, force development graphs, surface pressures, the underbody flow and the wake are studied in detail with Computational Fluid Dynamics, which is initially validated by wind tunnel testing. It shows that the stationary ground has severe deviations from the full moving ground on the aerodynamic performance due to the inaccurate pressure distribution on the underbody. This is mainly attributed to the high level of interaction between the underbody and the boundary layer development. In addition, a ground boundary layer separation bubble can be observed under the tail end of the train for the stationary ground on account of insufficient energy to overcome the increasing adverse pressure gradient. In order to guarantee a correct underbody flow, a partially moving ground is proposed, including the ''3-moving ground'' and the ''1-moving ground''. Such ground simulation systems are well compatible with the fixed rail tracks and the bottom support struts compared to the full moving ground. As a conceivable method to reduce the influence of the boundary layer, raising the high-speed train model with different ground clearances is also studied. Overall, the 3-moving ground is suggested to be the best choice for the ground simulation systems in high speed train wind tunnel testing.

Unsteady Aerodynamic Performance of a Maglev Train: The Effect of the Ground Condition

“…In the flow structure development area, due to the action of the boundary layer, the value under static ground conditions is larger, and the value under the two ground conditions is smaller and does not significantly differ case-to-case. In the track side position of the wake area, the slipstream peak value is large and directed forwards under moving ground conditions, which differs from the trend found by Xia et al using a CRH3 model based on a flat ground configuration [30] . This is due to the interaction between the tail vortex structure and the track during backwards flow development and the interaction between the main vortices on each side of the train: this makes the vortex structure in the wake area stronger, thus generating a stronger slipstream.…”

Aerodynamic effects of the gap spacing between adjacent vehicles on wind tunnel train models

“…Currently, the RANS, DES (detached eddy simulation), and LES (large-eddy simulations) are the main methods used for the study of train aerodynamics. Compared with the LES and DES, RANS can better balance the numerical predication accuracy and computational cost (He et al, 2019;Morden et al, 2015;Munoz-Paniagua et al, 2017), and has been successfully applied in the studies of the aerodynamic performances of HSTs and cars (Gao et al, 2019;Kurec, Remer, Mayer, et al, 2019;Liu et al, 2019;Xia et al, 2016). Meanwhile, considering that the main concerns of this study is the time-averaged properties of the aerodynamic quantities and surrounding flow field of the train model, thus the RANS was selected in this study.…”

Aerodynamics of High-Speed Trains with Respect to Ground Simulation

“…Thus, for a wind speed of 50 m/s the accuracy of the measured pressure coefficients is around ±0.005. The differences at most pressure taps are small, but three areas with larger differences are highlighted as (1) to (3). Their locations are marked in Figure 10.…”

“…In [3], Xia et al used CFD to investigate a three car train model with different ground simulations. While the drag of the first car decreased by only four drag counts (one drag count: ∆c D = 0.001) when switching from a full moving ground to a static ground, the total drag of the three car train dropped by 6.4%.…”