Fire Dynamics and Smoke Control in Tunnel Environments
Summary
Tunnel fires present a complex challenge due to the confined geometry and the strong coupling between fire development, smoke movement and ventilation strategies. Heat release rates within a tunnel dictate the intensity of buoyant flows and ceiling jets, while the longitudinal orientation drives plume propagation towards portals or shafts. Thermal stratification often leads to a distinct smoke layer beneath the tunnel crown, which can compromise visibility and tenability for evacuation and rescue. Both natural and mechanical ventilation can be harnessed to control smoke movement, yet their effectiveness depends on shaft configuration, flow rates and fire location. Computational fluid dynamics and physical scale models have deepened our understanding of transient phenomena such as vortex formation at shaft intersections, the decay of temperature and pollutant concentration along the tunnel axis, and the impact of barrier installations on layer stability. Practical applications range from optimising shaft geometry to the design of smoke barriers and exhaust systems, all aimed at limiting smoke spread, reducing toxic gas exposure and enhancing occupant safety in diverse tunnel environments worldwide.
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Fire Dynamics and Smoke Control in Tunnel Environments publication trend
The graph below shows the total number of articles in fire dynamics and smoke control in tunnel environments across all publications each year (not limited to Nature Index journals).
Technical terms
Heat release rate (HRR): The rate at which a fire releases thermal energy, typically expressed in megawatts, which determines buoyant flow strength and smoke production.
Thermal stratification: The formation of distinct temperature layers within a tunnel due to the accumulation of hot gases beneath the ceiling and cooler air below.
Ceiling jet: A high‐velocity, thin flow of hot gases that spreads along the tunnel roof immediately above a fire source, influencing smoke layer height.
Longitudinal ventilation: The flow of air or exhaust along the length of a tunnel, either induced naturally by buoyancy and wind or mechanically by fans, used to control smoke movement.
Smoke barrier: A physical obstruction, often installed under the tunnel crown, designed to impede the downstream advance of the smoke layer and maintain clearer zones.
References
- Effects of vertical shaft geometry on natural ventilation in urban road tunnel fires. Journal of Civil Engineering and Management (2014).
- A study on longitudinal distribution of temperature rise and carbon monoxide concentration in tunnel fires with one opening portal. Case Studies in Thermal Engineering (2021).
- Fire-smoke control strategies in road tunnels: The effectiveness of solid barriers. Case Studies in Thermal Engineering (2021).
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