Mechanical Properties Research Of Ballast Flying Based On Computational Fluid Dynamics

ABSTRACT:Railway is an important national infrastructure and environmentally efficient transport, which plays an important role in the integrated transport system, also be conductive in economic and social coordinated comprehensive and sustainable development. Train speed is an important sign of measuring a country’s level of modernization of railways, because high-speed railway with fast, safe, comfortable, environmental protection and other advantages, that has become the trend of the development of rail transportation.With the increasing speed of the train, the train aerodynamic effect highlights, resulting in a series of aerodynamic problems such as a sharp increase in train air resistance, a sharp increase in energy consumption and ballast particle on ballasted track surface splash. Ballast-flying not only damaging for trains, track structure and the surrounding environment, but also endangering traffic safety, seriously restricts the development of high-speed railway. According to flying ballast, researchers inland and abroad mainly using experimental and numerical analysis to study the train-wind velocity, pressure and aerodynamics and mechanical mechanism of ballast particles, linear train, track bed structure etc. This paper mainly relys on aerodynamic characteristics of ballast and the track bed structure analyzing the phenomenon of ballast-flying:For aerodynamic characteristics of discrete ballast particles, Studying ballast particles moving critical condition and the quality parameters of the particles by wind tunnel tests, after that designing numerical simulation of the wind tunnel tests; For aerodynamic characteristics of track bed structure, According to continuum fluid dynamics theory, We analysis the aero dynamically optimized and comparison of ballasted track bed shoulder height and shoulder form based on computational fluid dynamics (CFD). Aerodynamic-sleeper is aerodynamically geometry optimized on basis of III type sleepers, then comparatively analyzing the track bed surface aerodynamics of III type sleeper and optimized aerodynamic-sleeper in factors that the height of sleeper trough and sleeper spacing.Single ballast particle shape, mass have a significant impact on ballast-flying, the spherical and half-spherical shape of ballast whose mass are less than100g is easy to move, when wind tunnel test speed is approaching18m/s-25m/s the majority of the experimental ballast particles start moving; The wind pressure on ballast shoulder of the flat form is smaller than that the same shoulder height of tip shoulder forms, Simulation results shows that flat ballasted shoulder form of height100mm shoulder has better aerodynamic performance advantages in the prevention of ballast flying. Because of the smoother upper surface of optimized sleeper, the excitation of turbulence immunity of sleeper tank wind field decreases, which helps to reduce the chance of ballast flying.