Effects of buoyancy induced roof ventilation systems for smoke removal in tunnel fires

• Smoke removal in tunnel fire is significant with multiple ceiling vents.
• Significant change in tunnel flow characteristics by varying heat source and ceiling vent locations.
• As distance from fire source and ceiling vent increases smoke venting efficiency decreases.
• Tunnel temperature distribution increases with decrease in vent size.

The present article highlights the performance of natural roof ventilation systems and its effects on tunnel fire flow characteristics. Numerical analysis is performed using Large Eddy Simulations (LES) to predict fire growth rate and smoke movement in tunnel with single and multiple roof openings. The smoke venting performance of ceiling vents are investigated by varying the vent size and fire source locations. The critical parameters such as mass flow rate through ceiling openings, smoke traveling time and fire growth patterns are presented. The ceiling openings are effective in transferring hot gases and reduces the longitudinal smoke velocity. The heat source and ceiling vent locations significantly affects the vent performance and smoke behavior in tunnel. The present results are in good agreement with the experimental results available in literature.