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Combined Buoyancy- and Pressure-Driven Flow Through a Horizontal Vent: Theoretical Considerations.

Combined Buoyancy- and Pressure-Driven Flow Through a
Horizontal Vent: Theoretical Considerations.
(720 K)

Cooper, L. Y.

NISTIR 5252; 17 p. September 1993.

Combustion Institute/Eastern States Section. Chemical
and Physical Processes in Combustion. Technical
Meeting, 1993. October 25-27, 1993, Princeton, NJ,
315-318 pp, 1993 AND Fire-and-Explosion Hazard of
Substances and Venting of Deflagrations. 1st
International Seminar Proceedings. July 17-21, 1995,
Moscow, Russia, Molkov, V., Editor, 1-11 pp, 1995, 1993.

### Available from:

National Technical Information Service

Order number: PB94-103694

### Keywords:

vents; building fires; compartment fires; computer
models; fire models; mathematical models; zone models

### Abstract:

*
Flow through a horizontal vent is considered where the
vent-connected spaces near the elevation of the vent are
filled with fluids of different density in an unstable
configuration, with the density of the top space larger
than that of the bottom space. With zero-to-moderate
cross-vent pressure difference the instability leads to
a bi-directional exchange flow between the two spaces.
For relatively large cross-vent pressure difference the
flow through the vent is unidirectional, from the high-
to the low-pressure space. For arbitrary specified
cross-vent pressure difference, boundary value problems
for the flow are formulated for cases where the fluid
media in the two spaces are the same perfect gas, with
relatively high and low temperature (corresponding to
low and high density) in the lower and upper spaces,
respectively. Two separate classes of problem are
distinguished. In the first, the higher pressure is in
the space above the vent. This enhances the downward
component of the flow from the top to the bottom space,
and diminishes, or reduces to zero, the upward flow. In
the second, the higher pressure is in the lower space
leading to enhancement of the upward flow, etc.
Relationships between the two boundary value problems
and their solutions are identified. These are useful
for extending an available solution for one class of
problem to that of the other and for unified
understanding and correlation of experiment data for the
two flow configurations.
*