Numerical Investigation of the Deposition Characteristics of Snow on the Bogie of a High-Speed Train

To investigate the deposition distribution of snow particles in the bogie surfaces of a high-speed train,a snow particle deposition model,based on the critical capture velocity and the critical shear velocity,was elaborated.Simulations based on the unsteady Reynolds-Averaged Navier-Stokes(RANS)approach coupled with Discrete Phase Model(DPM)were used to analyze the motion of snow particles.The results show that the cross beam of the bogie frame,the anti-snake damper,the intermediate brake clamps in the rear wheels,the traction rod and the anti-rolling torsion bar are prone to accumulate snow.The accumulation mass relating to the vertical surface in the rear region,horizontal surface in the front region and the corner area of the bogie is high.The average snow accumulation mass for each component ordered from high to low is as follow:traction rod,frame,bolster,brake clamp 2,anti-rolling torsion bar,brake clamp 1,transverse damper,axle box 2,axle box 1,air spring,anti-snake damper,tread cleaning device.The snow accumulation mass on the front components of the bogie is more significant than that relating to the rear components.Particularly,the average snow accumulation mass of rear brake clamp 2 and axle box 2 is about twice as high as that of the front brake clamp 1 and axle box 1.

Influence of combination forms of intact sub-layer and tectonically deformed sub-layer of coal on the gas drainage performance of boreholes: a numerical study

High concentration and large flow flux of gas drainage from underground coal seams is the precondition of reducing emission and large-scale use of gas.However,the layered occurrence of coal seams with tectonically deformed sub-layers and intact sub-layers makes it difficult to effectively drain gas through commonly designed boreholes.In this study,the gas drainage performance in coal seams with different combinations of tectonically deformed sub-layers and intact sub-layers was numerically analyzed.The analysis results show that the gas drainage curve changes from a single-stage line to a dual-stage curve as the permeability ratios of Zone II(kII)and Zone I(kI)increase,raising the difficulty in gas drainage.Furthermore,a dual-system pressure decay model based on the first-order kinetic model was developed to describe the dual-stage characteristics of pressure decay curves with different permeability ratios.In the end,the simulation results were verified with reference to in-situ drainage data from literature.The research results are helpful for mines,especially those with layered coal seams comprising tectonically deformed sub-layers and intact sub-layers,to choose appropriate gas drainage methods and develop the original drainage designs for achieving better gas drainage performance.