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Theoretical studies on buoyancy-driven ceiling jets of tunnel fires with natural ventilation
RISE Research Institutes of Sweden. Tongji University, China.
RISE Research Institutes of Sweden, Safety and Transport, Safety Research.ORCID iD: 0000-0001-7744-2390
RISE Research Institutes of Sweden, Safety and Transport, Safety Research.ORCID iD: 0000-0002-9340-6768
Tongji University, China.
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2020 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 119, article id 103228Article in journal (Refereed) Published
Abstract [en]

The paper presents a theoretical study on the ceiling jets induced by small fires in tunnels. The ceiling jet thickness, temperature rise and velocity are analyzed theoretically with Non-Boussinesq approximation. The study focuses on the radial and one-dimensional ceiling jets. Numerical solutions in the radial region and one-dimensional shooting region are obtained and new analytical solutions in the critical flow region are achieved. Analytical solutions indicate that the ceiling jet thickness increases with distance away from the fire source, which largely differs from the existing models implying that the ceiling jet thickness in the one-dimensional critical flow remains constant. Additionally, impacts of the air entrainment, friction and heat transfer on the ceiling jet are analyzed. It is found that in the radial and one-dimensional shooting flow regions, the air entrainment has a much more significant effect than the friction and heat transfer. However, in the one-dimensional critical flow region, the impact of air entrainment seems to be negligible and the flow is dominated by the friction and heat transfer. Further, validation of the present theory is made by comparing with previous theories, semi-empirical models, and experiments. The results show that the present theory provides a good prediction of the ceiling jet properties with natural ventilation for a small fire. © 2020 The Authors

Place, publisher, year, edition, pages
Elsevier Ltd , 2020. Vol. 119, article id 103228
Keywords [en]
Ceiling jet, Ceiling jet thickness, Gas temperature, Tunnel fire, Velocity, Air entrainment, Fires, Friction, Heat transfer, Ventilation, Boussinesq approximations, Buoyancy-driven, Critical flow, Natural ventilation, Numerical solution, Semiempirical models, Temperature rise, Theoretical study, Ceilings
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-51210DOI: 10.1016/j.firesaf.2020.103228Scopus ID: 2-s2.0-85096837881OAI: oai:DiVA.org:ri-51210DiVA, id: diva2:1514206
Note

Funding details: China Scholarship Council, CSC; Funding text 1: The authors would like to acknowledge the Tunnel and Underground Safety Center (TUSC) at Research Institutes of Sweden (RISE) for the financial support. Qinghua Guo is also funded by the China Scholarship Council , which is gratefully acknowledged. Thanks also to Dr Francine Amon at RISE for the valuable comments.

Available from: 2021-01-04 Created: 2021-01-04 Last updated: 2023-06-08Bibliographically approved

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Li, Ying ZhenIngason, Haukur

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