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The traditional discrete vapor cavity model (DVCM) is widely used in water hammer simulation. Water column separation in pipelines is usually predicted with this model. Nevertheless, the main weaknesses of this model consist of numerical instability and nonconvergence. Regarding the weaknesses of the traditional model, this paper discusses an improved method. The new method uses a new water hammer velocity formula, a new cavity model, and a floating grid method. Through simulations to test the effects of the new model, an experimental platform can be established to realize a water hammer with multipoint collapsing. The numerical simulation was programmed in C++ and the test was carried out with an actual pipeline model built in the laboratory. After certain modelling and calibration, the parameters in the simulation calculation were consistent with the measured parameters in the test. The numerical simulation results were compared with the experimental results. For the hydraulic transient system with multipoint collapsing, the superposition effect of the wave crest of the pseudo-water hammer in the traditional calculation model was obvious. The pressure of the water hammer in the simulation calculation was significantly higher than the actual value and the convergence effect of the water hammer wave was not good. Compared with the results of the traditional model, the simulation results of the new model were closer to the measured values. Therefore, the new model has better numerical solution accuracy, stability, and convergence, which is worth further study and promotion.

Train icing may cause a series of problems to the safety of railway transportation in high and cold regions. Some important technologies on solving this issue are discussed in this paper, with the latest research landscape provided and the future development opportunities suggested. The hazards and principles of train icing are explained firstly, followed by a summary of several available methods of snow melting and de-icing, with their application and shortcomings indicated. The research progress of some basic issues such as the snow conditions of bogie parts and the optimal design of snow protection are discussed and analysed in detail. However, the problem of snow and ice accumulation during train operation has not been completely solved with the existing methods. At the end of this pager, suggestions on snow-resistance technology for trains are proposed for future study and development.