Community-Scale Fire Spread.
Community-Scale Fire Spread.
(329 K)
Rehm, R. G.; Hamins, A.; Baum, H. R.; McGrattan, K. B.;
Evans, D. D.
NISTIR 6891; 16 p. July 2002.
Order number: PB2002-107932
Keywords:
fire spread; wildland fires; large scale fire tests;
wildland urban interface; mathematical models;
computational fluid dynamics; fuel loads
Abstract:
This paper addresses community-scale fires, which have
also been called urban/wildland interface or intermix
fires. These fires arise when wildland fires invade the
built environment and attack structures as well as
wildland fuels. The prediction of the spread of wildland
fires, such as those occurring out West this past
summer, has been accomplished through "operational"
mathematical models. These models are based on empirical
correlations for wildland fuels and have generally
performed well. They fail, however, when the fire
spreads to the built environment where the empirical
correlations no longer apply and where there is greatly
increased potential for property damage, injury and
death. The Oakland and Berkeley Hills fire of October
21, 1991, and the Los Alamos fires of May 2000 are
examples of community-scale fires. The potential fuel
loadings for various land uses demonstrates that
structures generally provide much higher loadings than
wildlands do. While this comparison is useful, it could
also be misleading since generally, not all of the
potential fuel in either the wildland or the built
environment will burn. Furthermore, often the time
scales for ignition and the heat release rates for the
wildland fuel and the fuel in the structures will be
widely disparate, and these differences will influence
both the spread rate of the fire and its persistence.
Although the NIST computational model known as the Fire
Dynamic Simulator (FDS) was developed to study building
fires, it is now being extended to study community-scale
fires. These extensions require much higher resolution
data on local topography, buildings, vegetation, and
meteorological conditions. They also require additional
research on the mechanisms by which fires spread in the
built environment between discrete elements, such as
structures or structures and trees.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899