Study on the critical velocity in a sloping tunnel fire under longitudinal ventilation

Abstract The critical velocity and the backlayering length of smoke in tunnel fires are the two most important parameters in longitudinal ventilation design. This paper deduced the dimensionless expression of backlayering length and critical velocity of smoke in tunnel fires using the dimensional analysis method. The sectional coefficient ζ (ζ = A/H2) was introduced to describe the geometrical characteristic of the tunnel section, and the characteristic hydraulic diameter of the tunnel H ¯ replaced the tunnel height H. Then, CFD simulations were conducted in nine tunnels with different cross sectional shapes using the proprietary software Fire Dynamic Simulator (FDS), version 5.5. With the FDS simulations, prediction models for backlayering length and critical velocity modified by the sectional coefficient ζ and the tunnel slope were proposed. Meanwhile, complementary experiments were carried out in a 1/10 scale tunnel in order to provide a verification. The experimental results show a good agreement with the numerical simulations. Moreover, the prediction models for critical velocity on different slopes were compared with the prediction models proposed by others.

[1]  Yasushi Oka,et al.  Control of smoke flow in tunnel fires , 1995 .

[2]  Kevin B. McGrattan,et al.  Fire Dynamics Simulator (Version 5): User's Guide , 2007 .

[3]  G. I. Barenblatt.  Scaling, Self-similarity, and Intermediate Asymptotics: Dimensional Analysis and Intermediate Asymptotics , 1996 .

[4]  Qiqi Xu,et al.  An experimental study on critical velocity in sloping tunnel with longitudinal ventilation under fire , 2014 .

[5]  Fang Liu,et al.  Prediction of backlayering length and critical velocity in metro tunnel fires , 2015 .

[6]  Cao Li-ying.  Preparatory study on scenario design for subway fire , 2006 .

[7]  J. P. Vantelon,et al.  Investigation Of Fire-Induced Smoke Movement In Tunnels And Stations: An Application To The Paris Metro , 1991 .

[8]  Haukur Ingason,et al.  Study of critical velocity and backlayering length in longitudinally ventilated tunnel fires , 2010 .

[9]  Graham T. Atkinson,et al.  Smoke control in sloping tunnels , 1996 .

[10]  Hong Sun Ryou,et al.  An Experimental Study on the Effect of Slope on the Critical Velocity in Tunnel Fires , 2010 .

[11]  P. H. Thomas,et al.  THE MOVEMENT OF SMOKE IN HORIZONTAL PASSAGES AGAINST AN AIR FLOW , 1968 .

[12]  P. H. Thomas,et al.  THE MOVEMENT OF BUOYANT FLUID AGAINST A STREAM AND THE VENTING OF UNDERGROUND FIRES , 1958 .

[13]  Haukur Ingason,et al.  Model scale tunnel fire tests with longitudinal ventilation , 2010 .

[14]  Haukur Ingason,et al.  Model scale railcar fire tests , 2007 .

[15]  Cheuk Lun Chow,et al.  Smoke movement in tilted tunnel fires with longitudinal ventilation , 2015 .

[16]  Peter V. Nielsen,et al.  Full-scale experiment and CFD simulation on smoke movement and smoke control in a metro tunnel with one opening portal , 2014 .

[17]  Y. Wu,et al.  Control of smoke flow in tunnel fires using longitudinal ventilation systems - a study of the critical velocity , 2000 .

[18]  Javier Trelles,et al.  CFD Investigation of Large Scale Pallet Stack Fires in Tunnels Protected by Water Mist Systems , 2010 .

[19]  Dong Hyeon Kim,et al.  Critical velocity and burning rate in pool fire during longitudinal ventilation , 2007 .

[20]  Bart Merci.  One-dimensional analysis of the global chimney effect in the case of fire in an inclined tunnel , 2008 .

[21]  Mei Xiu-juan.  Study on fire scenarios characteristic for subway trunk arson simulation test , 2011 .