Numerical and Experimental Gravity Currents Related to Backdrafts.
Numerical and Experimental Gravity Currents Related to
Backdrafts.
(1201 K)
Fleischmann, C. M.; McGrattan, K. B.
Fire Safety Journal, Vol. 33, No. 1, 21-34, July 1999.
Keywords:
backdraft; gravity current; salt water; experiments
Abstract:
In order to clarify the mixing that occurs in a gravity
current which precedes a backdraft, a two-dimensional
simulation, a series of salt water experiments, and
backdraft experiments were performed. A compartment in
a ratio width/height/length of l/1/2 is used in the
experiments and computations. Two different openings
were used in the salt water experiments and numerical
computations: a fully open end wall and a h1/3
horizontal slot centred in an end wall, where h1 is the
compartment height. For the backdraft experiments only
the h1/3 horizontal slot was used. The visual
observations from the salt water experiments compare
well with the numerical simulation. Both show a small
mixed region at the gravity current shear interface for
the fully open wall and mixing throughout the entire
current for the h1/3 horizontal slot. Quantitative
comparisons are made in terms of the normalised density
differences. The transit time results, i.e., time
between opening the compartment and the time the gravity
current reaches the wall opposite the opening, for the
computations compared favourably with the transit times
from the salt water experiments. Velocity measurements
from the opening of the backdraft compartment, prior to
ignition, also are favourablc with the numerical
simulation.
