Smoke movement and control in longitudinal ventilated tunnel fires with cross-passages

This paper studies the characteristics of smoke movement and control in longitudinal ventilated tunnel fires with cross-passages through numerical modeling. Previous reports mainly focused on fires in single-hole tunnel, however, tunnels with cross-passages have been widely applied in real life, the cross-passages between main tunnels provide additional path for air and fire smoke, and significantly affect smoke temperature and back-layering length, which has not been studied in the past. Hence, full-scale simulations were conducted considering different heat release rates, fire locations, longitudinal ventilation velocities, and cross-passage intervals in this study. It shows that the smoke temperature distribution with or without cross-passages is almost the same under natural ventilation condition, while the temperature gradually increases with the decrease of interval of cross-passages under longitudinal ventilation condition. Due to the more air leakage, the smoke back-layering length increases with decreasing interval of cross-passage. The air leakage mass through the cross-passage was then characterized by the interval of cross-passages and fire location. Considering fire position and interval of cross-passages, the actual ventilation velocity is used to establish a new smoke back-layering length model. A basic understanding was provided by new findings in this study for smoke movement and control in tunnel fires with cross-passages.