Research On CFD Simulation Of Natural Ventilation In The Large Scale Diversion Tunnel In Overhaulpreiod

In recent years, as the improvement of diversion tunnel's design level and the construction technology, the length of tunnel is more longer and the buried depth of tunnel is more larger too. As the large scale diversion tunnel, ventilation is more difficulty, and the ventilation in overhaulpreiod is very important. As the energy conservation and emission reduction are continuously pushed, natural ventilation gets gradually attention of scholars both at home and abroad with its advantages of low investment, low energy consumption. Ventilation design, should first consider the possibility of natural ventilation. Therefore, this article will research the natural ventilation in the large scale diversion tunnel in overhaulpreiod, and discuss the feasibility of natural ventilation in the application of ventilation in the large scale diversion tunnel in overhaulpreiod.There are many influence factors of natural ventilation, and the influence by environmental factors are more bigger, which make the physical process of natural ventilation very complex, so the research methods of tunnel natural ventilation are still based on the theoretical analysis method and the experimental method, and the application of numerical simulation method is very little, especially hardly any to natural ventilation in the large scale diversion tunnel. But the numerical simulation method has the advantages of high efficiency and intuitive, which are incomparable with the other two methods, and the most widely used numerical simulation method is CFD. Therefore, this arcticle using the CFD simulation technology researches the simulation of natural ventilation in large scale diversion tunnel.The past articles researching the natural ventilation of underground engineering, when using CFD simulate the natural ventilation of underground engineering, their wind inlet boundary condition used velocity inlet condition. When the structure of group caverns is implex, then we cannot judge the flow's inlet and outlet, and the amount and velocity of wind aren't been known, using this boundary condition will lead to a wrong result, and cannot simulate the natural ventilation induced only by thermal efficiency and by combination of wind force and thermal efficiency. This article discusses the physical model and governing equation and boundary condition that are appropriate for the simulation of natural ventilation in large scale diversion tunnel, and builds 3D numerical model of natural ventilation, which can simulate the natural ventilation induced only by wind force or thermal efficiency and by combination of them.Directing at the feature of the tunnel natural ventilation, that the influence by environmental factors are more bigger, this arcticle using 3D numerical simulation of natural ventilation, and basing on specific engineering project, researches the influence degree to tunnel ventilation process of the main influencing factors of tunnel natural ventilation, which are temperature outside and temperature of the tunnel walls and natural wind speed outside. Finally, towards this project, make feasibility evaluation of design scheme of natural ventilation, based on this, research ventilation engineering measures in the large scale diversion tunnel in overhaulpreiod, and put forward reasonable ventilation engineering measures.