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Interpretation of flow fields induced by water spray systems in reduced-scale tunnel fire experiments by means of CFD simulations

Jiayun Sun (UGent) , Zheng Fang, Tarek Beji (UGent) and Bart Merci (UGent)
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Abstract
Computational Fluid Dynamics (CFD) simulation results, obtained with FDS 6.0.1 (McGrattan et al., 2013), are presented of reduced-scale tunnel fire tests. In (Sun et al., 2016), an extensive data set has been discussed in terms of temperature measurements in a reduced-scale tunnel, involving longitudinal ventilation and a variety of water supply through nozzles, in the context of potential smoke blockage. In (Sun et al., 2016), 10 different scenarios have been discussed, for different numbers of nozzles and different nozzle configurations. Given the limitation of the experimental instrumentation, as a series of thermocouple trees, a full interpretation of the flow field was impossible. Nevertheless, a detailed characterization and interpretation of this turbulent flow field under different circumstances is essential in the discussion of potential smoke blockage. To that purpose, CFD can be a very useful tool. In this paper, as a first step, results are presented for 2 cases, without mechanical longitudinal ventilation, in order to illustrate the validity and potential of the CFD simulations, with and without the water system (4 nozzles) activated. The validity of the CFD results, using the default FDS settings for turbulence and combustion modeling, is illustrated first through comparison of the temperature profiles with the experimental data. A comprehensive sensitivity study on the computational mesh and model settings for the water sprays is included. Subsequently, the mean flow and temperature fields are analyzed, providing significant additional insight into the impact of the water system. The entrainment, induced by the water sprays, is illustrated. This causes downward motion of the smoke in the sprays. By bumping onto each other, the impinging flows onto the floor in their turn create an upward flow in between the water spray envelopes that impinges onto the ceiling in the absence of longitudinal ventilation. The global effect is smoke blockage by the water system.

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Chicago
Sun, Jiayun, Zheng Fang, Tarek Beji, and Bart Merci. 2018. “Interpretation of Flow Fields Induced by Water Spray Systems in Reduced-scale Tunnel Fire Experiments by Means of CFD Simulations.” Tunnelling and Underground Space Technology 81: 94–102.
APA
Sun, Jiayun, Fang, Z., Beji, T., & Merci, B. (2018). Interpretation of flow fields induced by water spray systems in reduced-scale tunnel fire experiments by means of CFD simulations. TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY, 81, 94–102.
Vancouver
1.
Sun J, Fang Z, Beji T, Merci B. Interpretation of flow fields induced by water spray systems in reduced-scale tunnel fire experiments by means of CFD simulations. TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY. Elsevier ; 2018;81:94–102.
MLA
Sun, Jiayun et al. “Interpretation of Flow Fields Induced by Water Spray Systems in Reduced-scale Tunnel Fire Experiments by Means of CFD Simulations.” TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 81 (2018): 94–102. Print.
@article{8570217,
  abstract     = {Computational Fluid Dynamics (CFD) simulation results, obtained with FDS 6.0.1 (McGrattan et al., 2013), are presented of reduced-scale tunnel fire tests. In (Sun et al., 2016), an extensive data set has been discussed in terms of temperature measurements in a reduced-scale tunnel, involving longitudinal ventilation and a variety of water supply through nozzles, in the context of potential smoke blockage. In (Sun et al., 2016), 10 different scenarios have been discussed, for different numbers of nozzles and different nozzle configurations. Given the limitation of the experimental instrumentation, as a series of thermocouple trees, a full interpretation of the flow field was impossible. Nevertheless, a detailed characterization and interpretation of this turbulent flow field under different circumstances is essential in the discussion of potential smoke blockage. To that purpose, CFD can be a very useful tool. In this paper, as a first step, results are presented for 2 cases, without mechanical longitudinal ventilation, in order to illustrate the validity and potential of the CFD simulations, with and without the water system (4 nozzles) activated. The validity of the CFD results, using the default FDS settings for turbulence and combustion modeling, is illustrated first through comparison of the temperature profiles with the experimental data. A comprehensive sensitivity study on the computational mesh and model settings for the water sprays is included. Subsequently, the mean flow and temperature fields are analyzed, providing significant additional insight into the impact of the water system. The entrainment, induced by the water sprays, is illustrated. This causes downward motion of the smoke in the sprays. By bumping onto each other, the impinging flows onto the floor in their turn create an upward flow in between the water spray envelopes that impinges onto the ceiling in the absence of longitudinal ventilation. The global effect is smoke blockage by the water system.},
  author       = {Sun, Jiayun and Fang, Zheng and Beji, Tarek and Merci, Bart},
  issn         = {0886-7798},
  journal      = {TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY},
  language     = {eng},
  pages        = {94--102},
  publisher    = {Elsevier },
  title        = {Interpretation of flow fields induced by water spray systems in reduced-scale tunnel fire experiments by means of CFD simulations},
  url          = {http://dx.doi.org/10.1016/j.tust.2018.07.004},
  volume       = {81},
  year         = {2018},
}

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