Numerical Simulation and Analysis of Critical Velocity in Tunnel Fires Based on FDS

Abstract:

Critical velocity is a very important parameter in smoke control of tunnel fires and the variation of critical velocity against fire heat release rate is also one of the most important issues in tunnel fire researches. In this paper, a simplified physical model of a tunnel was established and the predictions of critical velocity for fire sizes in the 5-100MW range were carried out by FDS simulations. The FDS-predicted dimensionless critical velocities were compared with the values calculated by Wu and Bakar’s model. The result indicated that when the heat release rate was relatively small, Q≤30MW, the critical velocity increased with the increasing of heat release rate and varied as the one-third power of the heat release rate; when Q≥40MW, the growth rate of critical velocity became very small; after Q reach to 60MW, the critical velocity was almost unchanged with the increasing of heat release rate. In addition, the values of critical velocity calculated by Wu and Bakar’model which was derived from small-scale gas fire tests were underestimated. Therefore, the model suggested by Wu and Bakar is not suitable for critical velocity prediction in tunnel fires.

• Periodical: Advanced Materials Research (Volume 831)
• Pages: 455-459
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.831.455
• Online since: December 2013
• Authors: Shu Hui Xu*, Ling Fei Cui, Lei Ning, Zi Ye Wang
• Keywords: Critical Velocity, FDS, Heat Release Rate, Numerical Simulation, Tunnel Fire

References

[1] Y. Wu, M.Z.A. BaKar: Fire Safety Journal Vol. 35 (2000), pp.363-390.

[2] Y. Oka , G. T. Atkinson: Fire Safety Journal Vol. 25 (1995), pp.305-322.

[3] Huanhuan Li, Guoqing Zhu, Shaosong Chen, Lei Zhang, Juan Zhang: Fire Science and Technology Vol. 30 (2011), pp.198-201, in Chinese.

[4] Mc Caffrey BJ: National Bureau of Standards (1979), NBSIR 79-(1910).

[5] Jianping Yuan, Zheng Fang, Haifeng Huang, Zhi Tang: Journal of Civil, Architectural & Environmental Engineering Vol. 31 (2009), pp.66-70, in Chinese.

[6] Jae S, Hong S, Dong H: Tunnelling and Underground Space Technology Vol. 22 (2007), pp.262-271.

[7] Jae S, Hong S, Dong H, et al.: Building and Environment Vol. 43 (2008), pp.1225-1231.

[8] Longhua Hu: Studies on thermal physics of smoke movement in tunnel fires (University of Science and Technology of China, Hefei 2006), in Chinese.