Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal...Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal of the tunnel follows aW-shaped distribution.The congestion situation does not allowfor immediate longitudinal smoke exhaust at the early stage of the fire,and the natural spread of smoke is complicated.An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident,employing the fire dynamics software FDS,considering five slopes and four fire locations.The simulation results reveal that the layer of high-temperature smoke becomes thicker as one gets closer to the fire source.The thermal pressure difference significantly impacts the temperature distribution within the tunnel and the distance of smoke spread.The value of the thermal pressure difference is significantly affected by changes in slope.It reaches a maximum of 157 Pa at a 5%slope,while it is only 41 Pa at a 1%slope when the fire occurs at the V-point.Fire hazards vary across locations within the W-shaped tunnel,necessitating separate consideration of the V-point and inverted V-point fire characteristics.The mass flow rate in small and large slope tunnels shows different decay rates due to variations in the main forces acting on the movement.Hence,two equations have been developed to predict the smoke mass flow rate,indicating a nonlinear relationship with the tunnel slope and the distance fromthe fire source.The tunnel slope inversely affects the smoke mass flowrate at the same location.The results can be utilized as a reference for conducting evacuation operations and aiding rescues during aW-shaped tunnel fire.展开更多
Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy induced smoke flow characteristics of pool fres,involving smoke movement behaviour and longitudinal te...Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy induced smoke flow characteristics of pool fres,involving smoke movement behaviour and longitudinal temperature distribution of smoke layer.The canyon wind speed,longitudinal fre location and fre size were varied.Results show that there are two special smoke behaviours with the fre source positioned at different flow feld zones.When the fire source is positioned at the negative pressure zone,with increasing canyon wind speed,the smoke always exists upstream mainly due to the vortex,and the smoke temperature near the fire source increases frst and then decreases.However,when the fre source is located in the transition zone and the unidirectional flow zone,there is no smoke appearing upstream with a certain canyon wind speed.Meanwhile,the smoke temperature near the fre sources are decreases with increasing canyon wind speed.The dimensionless temperature rise of the smoke layer OT:*along the longitudinal direction of the tunnel follows a good exponential decay.As the canyon wind speed increases,the longitudinal decay rate of△T.*decreases.The longitudinal decay rate of AT*downstream of the fire is related to the fre location and canyon wind speed,and independent of the fire size.The empirical correlations for predicting the longitudinal decay of OT:*downstream of the fre are established.For a relatively large-scale fre,the longitudinal decay rate of AT:*upstream of the fire increases as the distance between the fire source and the upstream portal increases,especially for larger canyon wind speeds.展开更多
文摘Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal of the tunnel follows aW-shaped distribution.The congestion situation does not allowfor immediate longitudinal smoke exhaust at the early stage of the fire,and the natural spread of smoke is complicated.An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident,employing the fire dynamics software FDS,considering five slopes and four fire locations.The simulation results reveal that the layer of high-temperature smoke becomes thicker as one gets closer to the fire source.The thermal pressure difference significantly impacts the temperature distribution within the tunnel and the distance of smoke spread.The value of the thermal pressure difference is significantly affected by changes in slope.It reaches a maximum of 157 Pa at a 5%slope,while it is only 41 Pa at a 1%slope when the fire occurs at the V-point.Fire hazards vary across locations within the W-shaped tunnel,necessitating separate consideration of the V-point and inverted V-point fire characteristics.The mass flow rate in small and large slope tunnels shows different decay rates due to variations in the main forces acting on the movement.Hence,two equations have been developed to predict the smoke mass flow rate,indicating a nonlinear relationship with the tunnel slope and the distance fromthe fire source.The tunnel slope inversely affects the smoke mass flowrate at the same location.The results can be utilized as a reference for conducting evacuation operations and aiding rescues during aW-shaped tunnel fire.
基金supported by National Natural Science Founda-tion of China (Grant No.51974361)Natural Science Foundation of Hunan Province of China (No.2020JJ3046)the Fundamen-tal Research Funds for the Central Universities of Central South University (Grant Nos.2021zzts0762,502501004 and 502045009).
文摘Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy induced smoke flow characteristics of pool fres,involving smoke movement behaviour and longitudinal temperature distribution of smoke layer.The canyon wind speed,longitudinal fre location and fre size were varied.Results show that there are two special smoke behaviours with the fre source positioned at different flow feld zones.When the fire source is positioned at the negative pressure zone,with increasing canyon wind speed,the smoke always exists upstream mainly due to the vortex,and the smoke temperature near the fire source increases frst and then decreases.However,when the fre source is located in the transition zone and the unidirectional flow zone,there is no smoke appearing upstream with a certain canyon wind speed.Meanwhile,the smoke temperature near the fre sources are decreases with increasing canyon wind speed.The dimensionless temperature rise of the smoke layer OT:*along the longitudinal direction of the tunnel follows a good exponential decay.As the canyon wind speed increases,the longitudinal decay rate of△T.*decreases.The longitudinal decay rate of AT*downstream of the fire is related to the fre location and canyon wind speed,and independent of the fire size.The empirical correlations for predicting the longitudinal decay of OT:*downstream of the fre are established.For a relatively large-scale fre,the longitudinal decay rate of AT:*upstream of the fire increases as the distance between the fire source and the upstream portal increases,especially for larger canyon wind speeds.
