Numerical Simulation Study On Ventilation And Smoke Extraction In Urban Multi-ramp Tunnel Fires

With development of social economy and improvement of people’s living standard,the road transportation network in China has developed rapidly.Both the number and length of highway tunnels are increasing constantly which cause increasing trend of tunnel fires as well as expandable fire scale.Many studies aimed at tunnel fires have been done by researchers at home and abroad,and the problem of ventilation control in the tunnel has become an important part of the study.The numerical simulation method is an important method of the characteristics and organization of ventilation in tunnel fire.A large urban multi-ramp tunnel fire was taken as an example based on the existing tunnel fire ventilation network theory(1D)and computational fluid dynamics method(3D),the numerical simulation of urban multi-ramp tunnel fire is carried out in this paper.The following results are obtained:(1)Simulation study of local resistance coefficient of urban ramp was carried out based on FLUENT software with the use of three-dimensional analysis method in computational fluid dynamics.The flow field characteristics under different air volume/confluence conditions are analyzed,and the local resistance coefficients under different air flow conditions are obtained,which provides the basic parameters for macro network ventilation calculation in tunnel fire.(2)FLUENT software was used to simulate the three-dimensional urban ramp fire.The critical velocity,smoke flow and temperature field characteristics of the tunnel were analyzed.(3)An indirect coupling calculation method of simulation on computational fluid dynamics(3D)and simulation on network ventilation(1D)in tunnel fire is proposed.The coupling simulation of urban multi-ramp tunnel fire was carried out by using UDF of FLUENT and network ventilation software of tunnel fire.The three dimensional analysis of tunnel fire and study on ventilation and smoke extraction system of the whole tunnel were realized.The fan control strategies in tunnel fire were obtained.This paper has further study on the method of ventilation control in tunnel fire through the above study,which provides a reference for future research on ventilation control of tunnel fire.