| As the length of tunnel is no longer the mostly limiting factor because of the modern new ventilation development technology, longitudinal ventilation is more and more frequently used in large-long road tunnel ventilation. The expense on large-long road tunnel ventilation takes up about 50% in the whole management cost, which results in the tunnel major concerned personnel all around the world focus on the research on the airflow velocity, pressure distribution, contamination concentration, ventilation and fire-guard in large-long tunnel. It makes sense that using ventilation system in large-long tunnel properly and economically, controlling the contamination and smoke concentration, ensuring the normal ventilation and smoke-exhausting under fire disaster.Limited by lots of facts, the air distribution in tunnel is very difficult to be revealed the distributing law of the flow. In recent years, with the development and application of the computing technology, the level of numerical simulation is higher and higher. So it is available of directly simulating the air distribution with the hydrodynamics, CFD (Computational Fluid Dynamics) has grown a new subject following the development of computer.The thesis uses FLUENT and FDS software,based on computational fluid mechanics and heat transfer theory, to found the full two-dimensional and partial three-dimensional tunnel ventilation model. This paper is an application of Computational Fluid Dynamics in the turbulent flow of ventilated tunnel, Based on the theoretically analysis of physical and mathematical model, the K-εthere-equation turbulence model and method of SIMPLE are adopted to simulate the two-dimensional and three-dimensional air distribution of tunnel, effect of buoyant force on K-εmodel is considered and the wall function is used for the boundary condition. Governing equation discrete, solving of the conjugated algebraic set and SIMPLE method are also discussed in this paper.Taking the Xuefengshan tunnel as the numerical model in the two-dimensional simulation, gets the influence of the air flow distribution in tunnel when changing the rotate speed of the main jet fan in the tunnel and two group namely 4 intake and exhaust fan in the silo. In the three-dimensional simulation, this thesis focuses on the examination of integrating performance influencing factors of fan, educing the changing disciplinarian of air flow velocity in tunnel, jet fan air-outlet velocity, installation height, space between fans to the integrating performance influencing coefficient K. Introducing FDS(Fire Dynamics Simulator), the open for free software, to simulate and computer the temperature distribution and smoke flowing disciplinarian in fire disaster around the silos. The results indicate that, the inlet main jet fan influences every part of the tunnel remarkably than other fans, the pressure-rising effect of intake fan is larger than exhaust fan. The integrating performance influencing coefficient K grows up when the air flow velocity in the tunnel declines, when the jet fan outlet velocity or the space between jet fans in the same group or the installation height increases. Testify the critical velocity experiential formula even more. The contribution of intake and exhaust fan in silos under fire disaster to exhaust smoke is not large as the jet fan in tunnels.
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