Smoke spread characteristics inside a tunnel with natural ventilation under a strong environmental wind

In order to investigate the effect of strong environmental wind on a tunnel fire under natural ventilation, a series of numerical simulations were conducted using large eddy simulation method in this study. A tunnel model was established by a numerical simulation software, Fire Dynamics Simulator, to investigate the smoke movement under the stack effect induced inside a shaft. Four environmental wind speeds (39 m/s) and three heat release rates (3-20 MW) were considered. The smoke spread velocity inside the tunnel, downdraught phenomenon at the early stage of fire, smoke exhaust characteristics at the steady period of fire, temperature distribution in the tunnel and shaft, and occurrence of plug-holing were studied in detail, based on some typical characteristic parameters, such as mass flow rate, temperature and velocity vector. The results can be considered as a reference for the fire protection design of a tunnel with natural ventilation.