A computational study on effects of fire location on smoke movement in a road tunnel. (January 2016)

• Record Type: Journal Article
• Authors: Wang, Feng; Wang, Mingnian
• Is Part Of: Tunnelling and underground space technology. Volume 51(2016)
• Page Start: 405
• Page End: 413
• Publication Date: 2016-01
• Subjects: Tunnel fire -- Fire location -- Critical velocity -- Smoke flow -- CFD; Tunneling -- Periodicals; Underground construction -- Periodicals; Tunnels -- Periodicals; Underground areas -- Periodicals; 624.193
• DOI: 10.1016/j.tust.2015.09.008
• Languages: English
• ISSNs: 0886-7798

Abstract

Highlights: This study is focused on effects of cross-sectional fire location in a road tunnel. Significant differences in smoke movement are found. A modified model of critical velocity is proposed for a fire next to the wall. The likely cause of this phenomenon is explained in this study. Abstract: In this work, a numerical model of tunnel fire is developed and aimed to investigate the influence of cross-sectional fire locations on critical velocity and smoke flow characteristic. It is shown that the critical velocity for a fire next to the wall is obviously higher than that for a fire in the middle or on the left/right lane. The ratio is estimated to be 1.12. The predictions of critical velocity from 'small-fire' models show a good agreement with that for a fire in the middle or on the left/right lane from CFD. The tunnel height at the fire location is proposed to be instead of the hydraulic tunnel height in the 'big-fire' model of Wu and Bakar for a fire next to the wall. The smoke moves backward in a tongue like form as the ventilation velocity is lower than the critical velocity. The back-layering length of a fire in the middle is shown to be approximate twice than that on the left/right lane under the same ventilation velocity, although they share the same critical velocity. Whereas a relatively short back-layering length for a fire next to the wall under the velocity of 2.6 and 2.7 m/s. In addition, a snaky high-temperature profile on the top wall at the initial downstream is observed for a fire on the left lane and next to the wall, and finally a steady and layered smoke flow. The likely cause of this phenomenon is subsequently explained in this study.