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CFD simulation of train fire in the İstanbul metro tunnel

Bilge, Mahir İlter
Underground metro networks are expanding rapidly in all around the world and during the last few decades, tunnel fire accidents with severe casualties occurred in various countries. The frequency of the tunnel fire incidents will be increasing due to the increased amount of underground transportation routes in the upcoming years. In order to prevent the loss of lives in tunnel fires, accurate design of Tunnel Ventilation Systems is crucial. This research thesis presents the simulation of a mid-train fire scenario in the tunnel of the Marmaray Metro Line by the use of Fire Dynamics Simulator (FDS) Computational Fluid Dynamics (CFD) Software. The main goal of the simulation is to determine the efficiency of the emergency ventilation system in case of a mid-train fire in the metro tunnels and investigate the ways to increase the safety degrees in underground metro tunnels. Since mid-train fires are not widely studied, one purpose of this thesis is to attract attention to the risks associated with tunnel ventilation system activation in case of a mid-tunnel fire. In order to determine the boundary conditions of the CFD Simulation, on site measurements are carried out for the selected fire scenarios in the tunnel network. Full scale three dimensional tunnel geometry is modeled along with the five car train and the growth of fire is modeled by making use of appropriate approximations. Contour plots of temperature and visibility are obtained for the cases with and without the activation of Tunnel Ventilation Systems (TVS) and the tenability criterion in the tunnel was examined by making use of widely accepted standards. By making a comparison of results with and without the TVS activation, it is concluded that during the mid-train tunnel fire, fan operation adversely effects the tenability conditions for the passengers at the downstream side of the fire. Therefore, for the studied fire scenario, it is safer to disable the ventilation fans and allow the passengers self-evacuate and activate the fans after evacuation to assist the fire-fighters.