Investigation of High-Speed Train Drag with Towing Tank Experiments and CFD

Engineering Applications of Computational Fluid Mechanics

et al. 2020

End of vehicle streamlined head was selected as the installation location, and aerodynamic behavior of trains with and without braking plates was compared to analyze the formation of the braking force and the evolution of the flow field. An IDDES method based on the SST κ-ω turbulence model was used to investigate the unsteady flow, and the numerical algorithm was validated. Results show that the train aerodynamic drag was significantly increased by opening the braking plates, especially when several braking plates were arranged separately in series on each train car. Furthermore, the effect of the plate installed on the tail car was superior to that of the braking plate on the head car, when only a single braking plate was used. It was also found that both the maximum value of the slipstream and negative pressure close to the braking plate depend on the position and size of the braking plate. The flow field around the lower part of the train was only slightly affected by opening the braking plates, and pairs of vortices over the train appeared when the braking plates were opened, significantly affected both size and position of vortices in the train wake.

Section: Methodsmentioning

confidence: 99%

“…A hexahedral-dominated mesh, widely used in previous studies (Gao et al, 2019;Guo et al, 2020;Salati et al, 2019;Tschepe et al, 2019), was used in grid generation. A refinement box with dimensions of 54 H tr × 1.5 H tr × 1.5 H tr surrounding the train was set to ensure the accurate simulation of the flow field around the train.…”

Section: Grid Generationmentioning

confidence: 99%

Comparison of different configurations of aerodynamic braking plate on the flow around a high-speed train

Engineering Applications of Computational Fluid Mechanics

et al. 2020

“…The gradients are computed with a least-squares approach in control volumes surrounding the cells, the momentum equation is dealt with by bounded central differencing, and other flow equations are dispersed by the second-order upwind. 36–38 The semi-implicit method for pressure-linked equations-consistent (SIMPLEC) was selected to deal with pressure–velocity coupling. 23,39,40 A dual time-stepping format with second-order accuracy was used for time discretization.…”

Section: Methodsmentioning

confidence: 99%

Numerical study on the effect of damaged windows on aerodynamic characteristics of passenger trains under strong crosswind

Proceedings of the Institution of Mechanical Engineers, Part C:

Liu

2020

Sand and gravel blown up by strong wind will cause damage to windows. Following up, it will cause the change in the flow field around a train immediately, which has a significant impact on the aerodynamic performance of the train. Delayed detached-eddy simulation based on the shear stress transport κ-ω turbulence model was used to investigate the aerodynamic characteristics of passenger vehicles under crosswind, and the effect of damaged windows on the train aerodynamic performance and flow field around the train was analyzed and compared. The grid generation and numerical method are verified in the previous studies. Results show that the aerodynamic performance of a passenger vehicle is significantly affected by damaged windows on both sides of the passenger vehicle, both the aerodynamic lateral force and overturning moment of the passenger vehicle were decreased, and this has a small effect on the aerodynamic performance of the downstream passenger vehicle. Fluctuation of the aerodynamic lift, lateral force, and overturning moment of a vehicle with damaged windows on both sides of the vehicle is significantly increased. Damaged windows do not change the existence of the main vortices around vehicles, but the size, location, and strength of the main vortices are obviously changed, especially when windows on both sides of the vehicle are damaged. Therefore, when windows on the windward side of the vehicles are damaged, opening or broking windows on the leeward side of the vehicles will help reduce the risk of vehicles overturning and derailment.

“…In previous studies, 35,36,[45][46][47][48][49][50] OpenFOAM 4.1 was used to divide the computational domain under the control of the snappyHexMeshDict file, which generated a hexahedral dominated mesh. This method has been successfully applied to the simulation of the train aerodynamic characteristics.…”

Section: Grid Generationmentioning

confidence: 99%

Aerodynamic behavior of a high-speed train with a braking plate mounted in the region of inter-car gap or uniform-car body: A comparative numerical study

Proceedings of the Institution of Mechanical Engineers, Part F:

Liu

et al. 2020

The continuous increase in train speed has brought serious challenges to train braking safety. Aerodynamic braking technology can effectively improve the braking effect of trains at high speeds. In this study, an aerodynamic braking device installed in the inter-car gap region (ICG) of a high-speed train is proposed and the aerodynamic performance of the high-speed train with an aerodynamic braking device is assessed by improved delayed detached eddy simulation (IDDES) based on the κ-ω turbulence model. The results show that the opening of the plate significantly changes the aerodynamic performance of the train, thereby greatly increasing the aerodynamic forces of the train and their fluctuation degree. The effect of the opening of the plate increases the turbulence of the downstream flow field around the tail car. The affected area is mainly concentrated in the flow field around the location of the plate for the pressure field and the whole flow field behind the plate for the velocity field. The effect of the plate mounted on the uniform-car body region (UCG) on increasing the aerodynamic drag is better than that at the ICG, though the aerodynamic fluctuation and the influence on the surrounding flow field will also be great.