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Proposing a general formula to calculate the critical velocities in tunnels with different cross-sectional shapes

Savalanpour, H ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.1016/j.tust.2020.103798
  3. Publisher: Elsevier Ltd , 2021
  4. Abstract:
  5. Among the parameters affecting the critical velocity in tunnel fires, the tunnel cross-sectional shape could significantly affect the tunnel fire characteristics, mainly due to the wall-bounded physics of the tunnel fire. Previously, the effects of the cross-sectional geometry of the tunnel were calculated using the non-dimensional analysis and hydraulic height of the tunnel. The dimensionless analysis using hydraulic height calculates only the effects of the tunnel sizes and does not capture the effects of the shape of the tunnel cross-section. Developing a 3D computational fluid dynamics tool using the body-fitted grids, the critical velocities are calculated for the 7 different cross-sectional shapes of tunnels, including the curved shape and the rectangular shape cross-sections, to precisely find the effects of the tunnel cross-sectional shape. The shape coefficient of the tunnel cross-section (area of the tunnel cross-section divided by the square of its height) is used as a tuning factor to correlate the results of the different cross-sectional shapes. Also, a modified formula is proposed to calculate the critical velocity of any arbitrary cross-sectional shape of the tunnel. Finally, the proposed formula is validated using the benchmark data. A series of recommendations in tunnel fires are provided using the proposed formula. © 2020 Elsevier Ltd
  6. Keywords:
  7. Computational fluid dynamics ; Fires ; Vehicular tunnels ; Critical velocities ; Cross-sectional shape ; Crosssectional geometry ; Dimensionless analysis ; Nondimensional analysis ; Rectangular shapes ; Shape coefficients ; Tunnel cross-section ; Velocity ; Computational fluid dynamics ; Fire behavior ; Geometry ; Model test ; Model validation ; Three-dimensional modeling ; Tunnel ; Tunnel design
  8. Source: Tunnelling and Underground Space Technology ; Volume 110 , 2021 ; 08867798 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0886779820307525