Numerical computation of multi-phase flows

The low-velocity impact response of A6N01S-T5 hollow extruded aluminum alloy corrugated sandwich beams used for the carbody of high-speed trains, under drop-weight impact was investigated in this study. A failure mechanism map of the corrugated sandwich beam under low-velocity impact was obtained by theoretical analysis, which was verified by experimental and finite element simulation results. Typical deformation mode, load-displacement response, and energy absorption of dynamically-loaded corrugated sandwich beams were discussed, and the effects of initial impact energy and impact angle on the impact response of specimens were also explored. The results indicate that there are three initial failure modes of corrugated sandwich beams under the drop-weight impact, namely face-sheet yield, face-sheet buckling, and core buckling, and both initial failure mode and critical load of sandwich specimens are sensitive to the face-sheet thickness and core thickness. The shear deformation of the corrugated core and gradually loading load-displacement response were observed for the case of forward impact, while the compression deformation of the corrugated core and load-displacement response with a larger initial peak were found for the case of reverse impact. Regardless of forward impact or reverse impact, the increase of initial impact energy will lead to the increase of maximum displacement response and structural resistance of sandwich beams. The increase in impact angle leads to the larger values of peak load, deformation resistance, and energy absorption efficiency of specimens for an impact angle less than 60 degrees, while the dynamic response of specimens is not sensitive to the increased impact angle within 75 to 90 degrees. 

Low-velocity impact response of aluminum alloy corrugated sandwich beams used for high-speed trains

Could the accident of “Ever Given” have been avoided in the Suez Canal?

The dynamic response of high-speed trains under meteorological hazards concerns operation safety and serviceability. This paper investigates the dynamic response of high-speed train-track-bridge coupled system subject to combined wind and snow. A numerical model integrating a computational fluid dynamics model and a multi-body dynamics model was established to predict the dynamic response of the couple system. The computational fluid dynamics model was used to analyze the aerodynamic loads applied to the coupled systems. The multi-body dynamics model was used to analyze the dynamic response of the coupled system under the aerodynamic loads. The effects of train speed, wind speed, and snow depth on the dynamic response were evaluated. A law was formulated to specify the speed limits for safe operation of high-speed trains. The results showed that combining wind and snow aggravated the dynamic response of high-speed trains via altering the aerodynamic loads applied to the coupled system. This research will promote practical operation and management of high-speed trains. 

Dynamic response of high-speed train-track-bridge coupled system under combined wind and snow

In this paper, the aerodynamic performance of the head car of a CRH2 train running in sandstorms was investigated. A numerical simulation method based on Realizable k-ε turbulence model was used to explore the flow features around the high-speed train. The accuracy of mesh resolution and methodology of CFD was validated by wind tunnel tests. A discrete phase model (DPM) was adopted to investigate the effects of sand particle properties (diameter and restitution coefficient) on the aerodynamic performance of the head car. Yaw angle effects with the sand-laden flow on the aerodynamic coefficient were also discussed. The results show that the drag force, lift force, lateral force, and overturning moment of the head car increase significantly due to the sand, and the sand particle properties have dominant effects on the aerodynamic performance of the head car. The impact probability of sand particles on the vehicle increases with the sand particle diameter and the yaw angle increasing. Larger restitution coefficients lead to lager forces of the head car, resulting in more contribution to the aerodynamic coefficients. Owing to the sand collision, a larger yaw angle causes more contribution to the aerodynamic performance of the head car, and the influence of sand properties on the drag force, lateral force and overturning moment are enhanced with the increase of the yaw angle. Using appropriate coatings around the high-speed train can not only reduce the energy consumption, but also improve the lateral stability and the critical operational speed of the high-speed train in the sandstorms.

https://jafmonline.net/JournalArchive/download?file_ID=48401&issue_ID=255

D. Liu

Papers

Numerical Investigation of the Effects of Sand Collision on the Aerodynamic Behaviour of a High-Speed Train Subjected to Yaw Angles