Fire Technology

, Volume 43, Issue 4, pp 255–284

Evaluation of FDS V.4: Upward Flame Spread

  • Jae-Wook Kwon
  • Nicholas A. Dembsey
  • Christopher W. Lautenberger
Article

DOI: 10.1007/s10694-007-0020-x

Cite this article as:
Kwon, JW., Dembsey, N.A. & Lautenberger, C.W. Fire Technol (2007) 43: 255. doi:10.1007/s10694-007-0020-x

Abstract

NIST’s Fire Dynamics Simulator (FDS) is a powerful tool for simulating the gas phase fire environment of scenarios involving realistic geometries. If the fire engineer is interested in simulating fire spread processes, FDS provides possible tools involving simulation of the decomposition of the condensed phase: gas burners and simplified pyrolysis models. Continuing to develop understanding of the capability and proper use of FDS related to fire spread will provide the practicing fire engineer with valuable information. In this work three simulations are conducted to evaluate FDS V.4’s capabilities for predicting upward flame spread. The FDS predictions are compared with empirical correlations and experimental data for upward flame spread on a 5 m PMMA panel. A simplified flame spread model is also applied to assess the FDS simulation results. Capabilities and limitations of FDS V.4 for upward flame spread predictions are addressed, and recommendations for improvements of FDS and practical use of FDS for fire spread are presented.

Keywords

flame spreadCFD fire modelFDSmodel evaluation

Nomenclature

a

Mean absorption coefficient [m−1]

A

Pre-exponential factor [m/s]

c

Constant pressure specific heat of solid [kJ/kg · K]

C

Constant for defining an effective stoichiometric value of mixture fraction [−]

D*

Plume characteristic length [m]

EA

Activation energy [J/mol]

Hf

Flame height [cm]

Hp

Pyrolysis height [cm]

i

Radiation intensity [W/m2]

k

Thermal conductivity of solid [W/m · K]

L

Thickness of solid

\({\dot{m}}^{\prime\prime}\)

Mass loss rate per unit area [kg/m2 · s]

\({\dot{m}}_{\rm critical}^{\prime\prime}\)

Critical mass loss rate [kg/m2 · s]

Po

Background pressure [Pa]

\(\dot{Q}\)

Total heat release rate [kW]

\({\dot{q}}^{\prime\prime\prime}\)

Heat release rate per unit volume [kW/m3]

\({\dot{q}}_c^{\prime\prime}\)

Convective heat flux [kW/m2]

\({\dot{q}}_r^{\prime\prime}\)

Radiative heat flux [kW/m2]

\({\dot{q}}_{\rm net}^{\prime\prime}\)

Net heat flux [kW/m2]

R

Universal gas constant [J/mol · K]

S

Coordinate along path of radiation [−]

T

Temperature [K]

To

Initial temperature [K]

Ts

Surface temperature [K]

Tig

Ignition temperature [K]

Vp

Pyrolysis spread rate [cm/s]

X

Distance from heated surface [m]

Zst

Ideal stoichiometric value of mixture fraction [−]

Zst,eff

Effective stoichiometric value of mixture fraction [−]

Greek Symbols

β

Constant for pyrolysis spread rate [−]

Hv

Heat of vaporization [kJ/kg]

dδ

Grid spacing [m]

μ

Dynamic viscosity [kg/m · s]

ρ

Density of solid [kg/m3]

σ

Stefan-Boltzmann constant [5.67 × 10−11 kW/m2 K4]

χrad

Radiative fraction [−]

Abbreviations

CFD

Computational Fluid Dynamics

DNS

Direct Numerical Simulation

FDS

Fire Dynamics Simulator

HRR

Heat release rate

HRRPUV

Heat release rate per unit volume

LES

Large Eddy Simulation

MLR

Mass loss rate

MMA

Methyl methacrylate

NIST

National Institute of Standards and Technology

PMMA

Polymethyl methacrylate

TC

Thermocouple

LFL

Lower flammable limit

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Jae-Wook Kwon
    • 1
  • Nicholas A. Dembsey
    • 2
  • Christopher W. Lautenberger
    • 3
  1. 1.ArupNew YorkUSA
  2. 2.WPIWorcesterUSA
  3. 3.UC BerkeleyBerkeleyUSA