Dispersion and Deposition of Smoke Plumes Generated in Massive Fires.
Dispersion and Deposition of Smoke Plumes Generated in
Massive Fires.
(1183 K)
Ghoniem, A. F.; Zhang, X.; Knio, O.; Baum, H. R.; Rehm,
R. G.
Journal of Hazardous Materials, Vol. 33, 275-293, 1993.
Keywords:
plumes; dispersion; smoke
Abstract:
Massive fires resulting from the uncontrolled burning of
crude oil from spills or industrial accidents produce
large smoke-laden buoyant plumes which rise in the wind
direction before they equilibrate within a stably
stratified atmosphere. Beyond this point, the plume
material cools by entrainment and the plume becomes
negatively buoyant due to the heavy smoke loading. The
trajectory of the descending plume, which determines the
ground distribution of smoke, is the subject of this
paper. A computational model for the simulation of
large-scale smoke plumes resulting from such fires is
developed and applied to investigate the effects of the
plume initial properties on its trajectory and smoke
deposition patterns. Attention is focused on the
descent and dispersion of wind-driven plumes in a
homogeneous atmosphere, and the smoke deposition on flat
terrain. Results show that the plume dynamics in the
cross-wind direction are dominated by two buoyantly
generated, coherent, streamwise vortices which distort
the plume cross section into a kidney-shaped structure.
The strength of the two vortices and their separation
increase as the plume falls. The plume width grows
under the action of these vortices at a rate which
increases as the plume falls. The plume width grows
under the action of these vortices at a rate which
increases as the plume settles on the ground, leading to
a smoke footprint which does not resemble the prediction
of Gaussian dispersion models. The effects of the
injection altitude and the initial shape of the plume
cross section on the transport and dispersion of the
negatively buoyant smoke plume are investigated. Plumes
falling from higher elevations disperse more in the
vertical direction while those falling from lower
elevations disperse further in the horizontal cross-wind
direction. Plumes with circular cross-sections reach
the ground faster and disperse horizontally further than
plumes with elliptical cross-sections with the minor
axes in the vertical direction. Vertical plume
dispersion is weakly dependent on the shape of its
initial cross-section.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899