The Fire Simulation in a Road Tunnel

Fire behaviour, especially its interaction with ventilation system in tunnels, is still a challenging issue for road tunnel designers .This paper presents the results of a study investigating the influence of a road tunnel ventilation system, on conventional fires. For this purpose, a 25 MW fire corresponding to a conventional fire in a road tunnel was simulated using 2D numerical modelling, for transient viscous multi-component gas at low Mach numbers to study smoke and heat propagation within a road tunnel under fire .Complete Navier-Stocks and Reynolds equations were solved using developed algorithm of numerical modelling .The results from a series of calculations were compared with results of experimental researches to examine the accuracy and stability of the calculations .The comparisons showed that the algorithm provided a good description of physical processes in selected class of flow. It was also concluded that calculation accuracy is not lower than those obtained from established simulation software programs . The stability and good convergence of the algorithm was confirmed by separate calculations with different grid patterns for the tunnel under consideration .The results revealed that the temperature at tunnel wall may rise up to 900oC. The concentration of smoke may also increase up to 95 %with a burning truck .Results were applied to assess the ventilation system designed for a new long road tunnel in case of fire .The results from the study along with other information were applied to assess the designed ventilation system and to establish the suitable fire fighting and rescue plan

The Study of Aerodynamics in Special Parts of a Road Tunnel Using Physical Model

Background and Aims: Ventilation of road tunnels, using jet fans possess a number of featuresresulting from pattern of air flow distribution near solid walls as well as mutual effect of jet fans,dependence of jet momentum (thrust of jet fans) on air flow velocity in the tunnel and otherfactors.Method: In present work, large - scale experimental studies of turbulent jets in stable air mediumor in co - current flow near the solid boundary were performed. Experimental studies wereconducted with two physical models of ventilation system. The hydraulic similarity of physicalmodel and the real system were fulfilled. Measurements were performed with acceptable accuracyand there was shown that distance of jet adherence to the solid surface is specified by relativedistance between jet axis and a wall as well as velocity ratio (ratio of flow velocity to jet velocityof air).Results: Present study provided optimizing the location of jet fans in relation to tunnel walls.These experimental studies likewise theoretical researches proved that turbulent jetcharacteristics created by jet fan scarcely depend on Reynolds number. Thus, physical modelingof such jets can be fulfilled with small Reynolds numbers, corresponding to model flow mode.Conclusion: In particular, with flow velocities close to real value. In this case, apart fromgeometric similarity, there must be provided velocity equality in the model and in the real tunnel(co - current flow velocity) as well as jet velocity behind a fan. In present paper it is intended toillustrate more details of this study