Numerical study of critical re-entrainment velocity of fire smoke within the street canyons with different building height ratios

  • Quanli Wang
  • TaoTao Zhou
  • Qin Liu
  • Peixiang He
  • Changfa TaoEmail author
  • Qin ShiEmail author
Research Article


Traffic accident may bring vehicle fire in the street canyons. With its high temperature and numerous hazardous materials, the smoke produced by the vehicle fire may cause serious damage to the human body and the properties nearby, such as the glass curtain walls of buildings. The influence of the ambient air flow speed and street aspect ratio on the dispersion of fire smoke in street canyon has been analyzed by FDS software and theoretical analysis in this study. The impact of different windward building heights and different ambient air flow speeds u0 on the fire smoke were investigated. The results show that the fire smoke tilts towards the opposing direction of the ambient air flow within the street canyon, while the ambient air flow is perpendicular to the windward building. The results indicate that the critical re-entrainment velocity decreases at first, and then increases until it attains a constant with the building height ratio H1/H2. Finally, a predictive model of the critical re-entrainment velocity was developed under different building height ratios H1/H2.


Critical re-entrainment velocity Building height Street canyon Fire smoke 



The height at an arbitrary point


Windward building height


Leeward building height

\( \dot{Q} \)

Heat release rate


Move time of fire smoke in vertical direction


Move time of fire smoke in horizontal direction


Air flow speed


The width of street canyon


The vertical distance from building top edge to arbitrary point


The aerodynamic roughness length of the area

Greek symbols






The speed of fire smoke in vertical direction







The x axis



The work in this study was supported by China Postdoctoral Science Foundation (Grant No. 2018M640582), and the National Natural Science Foundation of China (Grant No. 51408181).

Authors’ contribution

All authors contributed equally in the preparation of this manuscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Automotive and Transportation EngineeringHefei University of TechnologyHefeiChina
  2. 2.School of Civil EngineeringHefei University of TechnologyHefeiChina

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