Investigation of natural ventilation using shafts in tunnels has been receiving more attentions; however, analyses on how fire position influences the natural ventilation performance have rarely been addressed. This study investigated the influence of different fire positions between two shafts on natural ventilation effectiveness in a tunnel by large eddy simulation. The smoke movement characteristics were studied in detail, with systematically varying the fire position between two shafts and the longitudinal wind speed in the tunnel. The typical smoke characteristic parameters, such as temperature distribution, mass flow rate and CO concentration were emphatically investigated. Some special phenomena, such as plug-holing and smoke bifurcation, were also discussed.
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