Seyed Mostafa Hosseinalipoor - Associate Professor, Iran University of Science & Technology
Feraydoon Mohammadi - M.Sc, Islamic Azad University, Ghorveh Branch
Kamran Mobini - Assistant Proessor, Shahid Rajaee University

In case of a tunnel fire, toxic gas and smoke particles released are the most fatal contaminations. When a fire occurs in a long tunnel, smoke control is crucial for obvious reasons of safety. The main objective of this model is to represent, as well as make possible, the duality between inertial forces (due to ventilation) and buoyant forces. In recent years Computational Fluid Dynamics has been used as a tool to evaluate the performance of emergency ventilation systems. In this paper, Computational Fluid Dynamics technique is used to simulate a small scale tunnel model (scale reduction is 1:20) to study the fireinduced smoke control by longitudinal ventilation systems. The Numerical model is non-thermal and a buoyant release is used to represent the fire smoke plume. Radiation and heat losses at the walls are not taken into account in this model. The influence of tunnel width (for a given tunnel height) on critical velocity (minimum longitudinal velocity needed to prevent smoke back flow when a fire occurs in a tunnel) are evaluated. Finally, Numerical simulation results are compared with former experimental results. The predicted critical velocity appears to be in good agreement with the measured critical velocity.

Tunnel fire; Buoyant jet; Criticalventilation velocity; CFD simulation