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International Journal on Engineering Performance-Based Fire
Codes, Volume 9, Number 1, p.7-30, 2007
7
FURTHER VALIDATION OF FIRE DYNAMICS SIMULATOR USING
SMOKE MANAGEMENT STUDIES
P. Coyle and V. NovozhilovThe Institute for Fire Safety
Engineering Research and Technology, Faculty of Engineering
University of Ulster, United Kingdom
(Received 7 July 2006; Accepted 13 December 2006)
ABSTRACT
Further validation of Fire Dynamics Simulator (FDS) developed by
NIST (USA) is performed using four smoke
filling scenarios reported in the literature. Careful comparison
is made to experimental data available for those
scenarios.
Performance of the code was found to vary considerably with
complexity of scenario (e.g. geometry). While
giving very reasonable results for a number of cases, average
deviation from experimental values in smoke-
filling rates and temperature predictions were above limits
claimed by developers.
The study emphasizes need for further development and extensive
validation of CFD codes used by fire
engineering practitioners.
1. INTRODUCTION
Fire Dynamics Simulator is an increasingly popular
CFD model choice for fire engineers and academia
researchers[e.g. 1,2]. The code has been developed
at the National Institute of Standards and
Technology, USA.
The underlying motivation for the present study is
assessment of accuracy of currently available
computer models for the purpose of their
integration into Engineering Performance-Based
Fire Codes (EPBFC). The importance of ongoing
validation and standardization work in fire-related
CFD is well recognised [3].
The most interesting property of the FDS code is
that it uses Large Eddy Simulation (LES) approach,
as opposed to many other (primarily commercial)
codes used by fire safety consultants. The latter use
Reynolds-averaged (RANS) governing equations.Use of LES is still
a hot topic in CFD community,
and many important fundamental issues related to
this approach are not completely resolved. As
examples, one could point out to importance of
different filtering procedures, influence of mesh
refinement on solution, etc. Since this innovative
technology is penetrating into practical design, it isimportant
that practitioners in the area are kept
informed of possible limitations and shortcomings
of the methods. It should be kept in mind that many
of those using modern CFD software may not have
sufficient background in CFD or combustion
fundamentals, therefore they need be warned ofpotential misuse
of computational tools.
The objective of the present study is to validate the
FDS code further using a number of well-
documented scenarios for comparison.
Fire Dynamics Simulator (FDS) Version 4.0.5 [4]
is used for the study.
2. RESULTS AND DISCUSSION
This section is segmented into four sub-sections,
namely scenarios A, B, C and D, which correspond
respectively to each selected physical experiment
under investigation.
For comparison with the experiments, some
technical features of FDS 4.0.5 should be noted.
The first one refers to smoke layer thickness
calculation in FDS. Relatively simple zone models
compute this quantity directly, along with theaverage
temperature of the upper and lower layers.
In a computational fluid dynamics (CFD) model
like FDS, there are generally no distinct zones, but
rather a continuous profile of temperature.
Nevertheless, the methods can be developed to
estimate layer height and average temperatures
from a continuous vertical profile of temperature.
The method employed by FDS is as follows.
Consider a continuous function T(z) defining
temperature T as a function of height above the
floor z, where z = 0 is the floor and z = H is the
ceiling. Define Tuas the upper layer temperature, Tlas the lower
layer temperature, and zint as the
