Numerical Simulation of Critical Velocity in Obstructed Tunnel

When highway tunnel is on fire, obstruction of vehicles in the tunnel have certain effects on the spread of fire smoke and critical velocity. This paper made CFD studies on the critical velocities when the blockage is located in the upstream flow of the fire smoke. The effect of the distance between fire source and blockage as well as the dimension ratio was analyzed. The numerical simulation results show that the critical velocity in upstream obstructed tunnel is smaller than that in empty tunnel and the critical velocity increases with the distance between the blockage and the fire source. The critical velocity increases with the heat release rate and decreases with the dimension ratio. The calculating model for critical velocity of empty tunnel was modified to adapt to obstructed tunnel.