The Smoke Flow Deflection Angles in Immersed Tunnel Fires with Multi-Point Concentrated Smoke Exhaust Mode: Representation Model and Influencing Mechanisms

The smoke flows from the tunnel to the exhaust vent, and then to the exhaust duct under the multi-point concentrated smoke exhaust mode of immersed tunnel fires. This will cause resistance and energy loss by forming smoke flow deflection angles, which is the angle between the direction of smoke flow velocity and the longitudinal direction. In this study, the correlations between the smoke flow deflection angles and mechanical characteristics are revealed. Specifically, the smoke exhaust processes are divided into "from the tunnel to the exhaust vent" and "from the exhaust vent to the exhaust duct". Based on the dimensionless analysis, the presentation model with influencing factors of smoke flow deflection angles is established. Through numerical simulation, the influencing mechanisms of longitudinal ventilation velocity, exhaust volume flow rate, and distance of multi-point exhaust vents on the smoke flow are analyzed in a three-lane immersed tunnel under 50 MW. The quantitative relationships between the smoke flow deflection angle and factors are obtained. The correlations between the smoke flow deflection angles and component forces are established. The results show that smoke flow deflection angles are affected by the transverse and longitudinal forces. Additionally, the influence of longitudinal ventilation velocity and exhaust volume flow rate is related to the distance of the exhaust vent group from the fire source. Furthermore, the increase in the smoke flow deflection angle is not determined by the distance of the exhaust vent group from the fire source, but rather by the distance of the multi-point exhaust vents.