Study on smoke flow characteristics in immersed tunnel fires with lateral centralized exhaust: Considering the effect of the slope

Abstract

In the case of fires in inclined immersed tunnels, smoke flow patterns differ from those of horizontal tunnels, and require a unique approach to lateral centralized smoke exhaust. In this study, we propose a prediction model for the exhausted mass flow rate near each vent and use Fire Dynamics Simulator (FDS) to analyze the flow field and components. Our findings indicate that temperature and smoke velocity distributions follow exponential decay with varying slopes, with exhaust efficiency and entrainment coefficient first increasing then decreasing at 1% and 2% slopes, and continuously decreasing at 3%, 4%, and 5% slopes. Only at a 6% slope can the smoke reach the nearest vent. Exhausted mass flow rate and exhaust volume have a positive correlation, and calculated values and simulated results agree well. This study can guide the design and management of lateral centralized smoke exhaust systems for inclined tunnels.