CFD Simulation on Tunnel Fire Smoke Control in Beijing Metro the 4th Line

In this paper,CFD method was applied to simulate the effectiveness of longitudinal ventilation on controlling the tunnel fire smoke diffusion with geometrical model,which was established based on certain section with actual size in Beijing metro the 4th line.The relationships between the critical ventilation velocity and the heat release rate(HRR) under different heat source conditions were studied,and then the results were compared with the other reported equations.It was presented that critical ventilation velocity was proportional to one-third power of the rate of HRR to tunnel width,and the declination angle of the heat rising plume was a constant with critical ventilation velocity.Furthermore,when the length of heat source was changed with HRR proportionally,the critical ventilation velocity was steady under high HRR condition.It was concluded that the setting of heat source had great influences on simulation results when the CFD method was used to realize the ventilation design of tunnel fire.