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Title: Temperature and Velocity Distributions within a Ceiling-jet along a Flat-ceilinged Horizontal Tunnel with Natural Ventilation // Proceedings of the Ninth International Seminar on Fire and Explosion Hazards. Vol. 1: 21-26 April 2019, Saint Petersburg, Russia
Creators: Oka Y.; Oka H.
Organization: Yokohama National University; National Maritime Research Institute
Imprint: Saint Petersburg, 2019
Collection: Общая коллекция
Document type: Article, report
File type: PDF
Language: English
DOI: 10.18720/SPBPU/2/k19-61
Rights: Свободный доступ из сети Интернет (чтение, печать, копирование)

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The properties of a ceiling-jet propagating along a tunnel axis are fundamentally different from those under an unconfined ceiling because the ceiling-jet in a tunnel receives the effects of sidewall, ventilation and so on. A series of fire tests was conducted using a small-scale tunnel with rectangular cross-sectional shape, the dimensions of which are 10.0 m (L) × 0.45 m (W) × 0.75 m (H). Detailed measurements of the temperature and velocity within a steady fire-driven ceiling-jet running along the centre of the ceiling were conducted. Temperature and velocity distributions from the tunnel ceiling in the perpendicular direction showed different shapes in accordance with the distance from the fire source in a tranquil flow region. To clarify the characteristic of the distribution shape, the measured data and distance from the ceiling surface were normalised by dividing them by the maximum value and the ceiling-jet thickness, respectively, at each point where distributions were obtained. The normalised distributions were found to coalesce onto the same line, independent of the distance from the fire source. Correlations, which are easy-to-use and can be depicted with one graph, were proposed. The temperature rise at an arbitrary distance from the fire source in the tranquil flow region was calculated based on the correlation of temperature attenuation, considering the heat loss from not only the tunnel ceiling but also sidewalls. The value of the Stanton number was determined on the basis of the Reynolds analogy. For a coefficient of wall friction, a law of the wall was applied to the ceiling on the assumption of a smooth flat plate. Correlations for representing the variations of Richardson number and the ceiling-jet thickness along the tunnel axis in the tranquil flow region were also determined semi-empirically. Velocity was obtained with Richardson number, temperature rise and ceiling-jet thickness. The values of the coefficients included in the developed correlations for the temperature and velocity attenuation were determined using experimental results conducted in the small-scale tunnel.

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