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Experimental and Numerical Studies on Two-Dimensional Gravity Currents in a Horizontal Channel.


pdf icon Experimental and Numerical Studies on Two-Dimensional Gravity Currents in a Horizontal Channel. (13585 K)
Chan, W. R.; Zukoski, E. E.; Kubota, T.

NIST GCR 93-630; 261 p. July 1993.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB94-165941

Keywords:

compartment fires; fire models; fire research; gravity current; inclined tests; room fires; smoke

Abstract:

The objective of this investigation is to examine the behavior of two-dimensional gravity currents, especially as applied to the spreading of smoke, generated from a room fire, along a long corridor. Both experimental and numerical techniques were used to provide a model that can adequately explain and predict the behavior of a gravity current under certain boundary conditions. A series of experiments was carried out to study the effects of Reynolds number on gravity currents in a horizontal water channel. Measurements of the time varying front position, velocity profile of the following current, and the depth of a gravity current were made using either dyed liquids or hydrogen bubble technique. Quantitative results were shown to agree with previously published results. A model was put forth to bridge the gap between the existing models for an inertia-buoyancy dominated gravity current and a viscous-buoyancy dominated one. Comparison between the experimental results and numerical results obtained from the model proved that the model can adequately explain the behavior of the phenomenon. A second series of experiments was conducted to investigate the behavior of gravity currents in an inclined channel. The quantitative results obtained were less scattered than those obtained in previous research. The gravity current was found to be unsteady in a horizontal channel, while a channel with an angle of inclination of one degree was found to produce a steady flow behind the front of the gravity current. The change of the gravity currents from an unsteady to a steady nature due to the change in the inclination of the channel was found to be gradual and much less abrupt than assumed in previous studies.