Characterization of buoyant flow stratification behaviors by Richardson (Froude) number in a tunnel fire with complex combination of longitudinal ventilation and ceiling extraction

Abstract A series of experiments were carried out in a model-scale tunnel [72 m (length) × 1.5 m (width) × 1.3 m (height)] to investigate the buoyant flow stratification behaviors in a tunnel fire with complexity of combination of longitudinal ventilation and ceiling extraction, which had not been studied before. The horizontal traveling velocity and vertical temperature profile were measured. The buoyant flow stratification conditions were visualized by a laser-sheet, as well as determined objectively by the vertical temperature profile measured. Buoyancy and inertial force are the two important factors influencing the buoyancy stratification. The interaction between them can be expressed by the Froude number or Richardson number. It was found that the buoyant stratification pattern was divided into three regimes. At regime I (Ri > 2.0 or Fr   0.8), a strong mixing existed between the upper buoyant flow and the lower air flow, that the buoyant flow stratification became unstable.

[1]  Wan Ki Chow,et al.  On the maximum smoke temperature under the ceiling in tunnel fires , 2006 .

[2]  Haukur Ingason,et al.  The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires , 2011 .

[3]  L. Y. Cooper,et al.  An Experimental Study of Upper Hot Layer Stratification in Full-Scale Multiroom Fire Scenarios , 1982 .

[4]  James G. Quintiere,et al.  An Assessment of Fire Induced Flows in Compartments , 1984 .

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

[6]  Haukur Ingason.  Correlation between temperatures and oxygen measurements in a tunnel flow , 2007 .

[7]  Longhua Hu,et al.  Studies on buoyancy driven two-directional smoke flow layering length with combination of point extraction and longitudinal ventilation in tunnel fires , 2013 .

[8]  J. Turner,et al.  Turbulent entrainment in stratified flows , 1959, Journal of Fluid Mechanics.

[9]  Olivier Vauquelin,et al.  Smoke extraction experiments in case of fire in a tunnel , 2002 .

[10]  Lizhong Yang,et al.  Thermal buoyant smoke back-layering flow length in a longitudinal ventilated tunnel with ceiling extraction at difference distance from heat source , 2015 .

[11]  Gary F. Bennett,et al.  The SFPE handbook of fire protection engineering : By P.J. DiNenno, C.L. Beyler, R.L.P. Custer, W.D. Walton and J.M. Watts, Jr., National Fire Protection Association, Quincy, MA and Society of Fire Prot , 1990 .

[12]  Longhua Hu,et al.  An experimental investigation and correlation on buoyant gas temperature below ceiling in a slopping tunnel fire , 2013 .

[13]  S. Hassid,et al.  Density jumps in smoke flow along horizontal ceilings , 2004 .

[14]  A. E. Holdø,et al.  An experimental study of stratified flow in enclosures , 2008 .

[15]  Haukur Ingason,et al.  Temperature stratification in tunnels , 2012 .

[16]  Kai Zhu,et al.  An experimental investigation on blockage effect of metro train on the smoke back-layering in subway tunnel fires , 2016 .

[17]  Tony Lemaire,et al.  Large Scale Fire Tests in the Second Benelux Tunnel , 2006 .

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

[19]  Yan Fu Wang,et al.  Thermal buoyant smoke back-layering length in a naturally ventilated tunnel with vertical shafts , 2016 .

[20]  Q. Zhang,et al.  The critical condition of longitudinal emergency tunnel ventilation – Comparison of theoretical prediction with experimental data , 2012 .

[21]  F. Vuilleumier,et al.  Safety aspects of railway and road tunnel: example of the Lötschberg railway tunnel and Mont-Blanc road tunnel , 2002 .

[22]  P. F. Hartman,et al.  Tunnel ventilation and safety in escape routes , 2006 .

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

[24]  Richard W. Bukowski,et al.  Verification of a Model of Fire and Smoke Transport , 1993 .

[25]  R. Huo,et al.  Experimental study on buoyant flow stratification induced by a fire in a horizontal channel , 2010 .

[26]  Longhua Hu,et al.  Effect of blockage-fire distance on buoyancy driven back-layering length and critical velocity in a tunnel: An experimental investigation and global correlations , 2013 .

[27]  J. S. Newman,et al.  Experimental evaluation of fire-induced stratification , 1984 .

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

[29]  Yasushi Oka,et al.  Ceiling-jet thickness and vertical distribution along flat-ceilinged horizontal tunnel with natural ventilation , 2016 .

[30]  Richard Carvel,et al.  A History of Fire Incidents in Tunnels , 2005 .

[31]  Longhua Hu,et al.  A global model on temperature profile of buoyant ceiling gas flow in a channel with combining mass and heat loss due to ceiling extraction and longitudinal forced air flow , 2014 .

[32]  Michael Poreh,et al.  Entrainment by adhered two-dimensional plumes , 2008 .

[33]  Yaping He,et al.  Determination of interface height from measured parameter profile in enclosure fire experiment , 1998 .

[34]  Wan Ki Chow,et al.  Studies on buoyancy-driven back-layering flow in tunnel fires , 2008 .