##
Fire Dynamics Simulator: Technical Reference Guide.

Fire Dynamics Simulator: Technical Reference Guide.
(800 K)

McGrattan, K. B.; Baum, H. R.; Rehm, R. G.; Hamins, A.;
Forney, G. P.

NISTIR 6467; 40 p. January 2000.

### Available from:

National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.

Telephone:
1-800-553-6847 or 703-605-6000;

Fax: 703-605-6900.

Website: http://www.ntis.gov

Order number: PB2000-104811

### Keywords:

fire models; computational fluid dynamics; sprinkler
activation; fire plumes; flame spread; simulation;
ignition

### Abstract:

*
The idea that the dynamics of a fire might be studied
numerically dates back to the beginning of the computer
age. Indeed, the fundamental conservation equations
governing fluid dynamics, heat transfer, and combustion
were first written down over a century ago. Despite
this, practical mathematical models of fire (as distinct
from controlled combustion) are relatively recent due to
the inherent complexity of the problem. Indeed, in his
brief history of the early days of fire research, Hoyt
Hottel noted "A case can be made for fire being, next to
the life processes, the most complex of phenomena to
understand". The difficulties revolve about three
issues: First, there are an enormous number of possible
fire scenarios to consider due to their accidental
nature. Second, the physical insight and computing power
necessary to perform all the necessary calculations for
most fire scenarios are limited. Any fundamentally based
study of fires must consider at least some aspects of
bluff body aerodynamics, multi-phase flow, turbulent
mixing and combustion, radiative transport, and
conjugate heat transfer; all of which are active
research areas in their own right. Finally, the "fuel"
in most fires was never intended as such. Thus, the
mathematical models and the data needed to characterize
the degradation of the condensed phase materials that
supply the fuel may not be available. Indeed, the
mathematical modeling of the physical and chemical
transformations of real materials as they burn is still
in its infancy. In order to make progress, the questions
that are asked have to be greatly simplified. To begin
with, instead of seeking a methodology that can be
applied to all fire problems, we begin by looking at a
few scenarios that seem to be most amenable to analysis.
Hopefully, the methods developed to study these "simple"
problems can be generalized over time so that more
complex scenarios can be analyzed. Second, we must learn
to live with idealized descriptions of fires and
approximate solutions to our idealized equations.
Finally, the methods should be capable of systematic
improvement. As our physical insight and computing power
grow more powerful, the methods of analysis can grow
with them. To date, three distinct approaches to the
simulation of fires have emerged. Each of these treats
the fire as an inherently three dimensional process
evolving in time. The first to reach maturity, the
"zone" models, describe compartment fires. Each
compartment is divided into two spatially homogeneous
volumes, a hot upper layer and a cool lower layer. Mass
and energy balances are enforced for each layer, with
additional models describing other physical processes
appended as differential or algebraic equations as
appropriate. Examples of such phenomena include fire
plumes, flows through doors, windows and other vents,
radiative and convective heat transfer, and solid fuel
pyrolysis. An excellent description of the physical and
mathematical assumptions behind the zone modeling
concept is given by Quintiere, who chronicles
developments through 1983. Model development since then
has progressed to the point where documented and
supported software implementing these models are widely
available.
*