Uses of Fire Dynamics Simulator V4 Uses of Fire Dynamics Simulator V4 for Large Scale/Industrial Incidentsfor Large Scale/Industrial Incidents

HUGHES ASSOCIATES, INCFIRE SCIENCE & ENGINEERING

Jason E. FloydJason E. Floyd

2004 Loss Prevention Symposium2004 Loss Prevention SymposiumAIChEAIChE 2004 Spring Meeting2004 Spring Meeting

New Orleans, LANew Orleans, LAApril 25 April 25 –– April 29, 2004April 29, 2004

Fire Dynamics Simulator (FDS)Fire Dynamics Simulator (FDS)Developed by NIST Building and Fire Developed by NIST Building and Fire Research LaboratoryResearch LaboratoryCompanion software called Companion software called SmokeviewSmokeview for for viewing/animating FDS outputviewing/animating FDS outputLarge eddy simulation (LES)Large eddy simulation (LES)Single parameter mixture fractionSingle parameter mixture fractionGray gas, finite volume radiation heat transferGray gas, finite volume radiation heat transfer1D temperature dependent heat conduction 1D temperature dependent heat conduction through surfacesthrough surfaces

Additional FDS CapabilitiesAdditional FDS CapabilitiesMultiMulti--block grids (single processor or MPI)block grids (single processor or MPI)Ignition of remote objectsIgnition of remote objectsPool fires with calculated heat release ratesPool fires with calculated heat release rates**Fire spread and growth over solid fuels Fire spread and growth over solid fuels (charring and thermoplastic)(charring and thermoplastic)**DropletsDroplets* * -- fuel spray fires, sprinklers fuel spray fires, sprinklers (convention and mist)(convention and mist)Fire suppression by oxygen depletion and Fire suppression by oxygen depletion and fuel cooling or delivered waterfuel cooling or delivered water**

**Level of physical detail in Level of physical detail in submodelssubmodels may not support its use for all applicationsmay not support its use for all applications

AcknowledgementsAcknowledgementsKevin Kevin McGrattanMcGrattan (NIST) (NIST) –– Lead software developerLead software developerGlenn Forney (NIST) Glenn Forney (NIST) –– SmokeviewSmokeview developerdeveloperHoward Baum (NIST) Howard Baum (NIST) –– Radiation and combustion Radiation and combustion theorytheoryRonald Ronald RehmRehm (NIST) (NIST) –– Large outdoor fires, windLarge outdoor fires, windDave Sheppard (ATF) Dave Sheppard (ATF) –– SprinkerSprinker spray spray measurementsmeasurementsUri Uri Vandsburger(VTVandsburger(VT), Chris ), Chris WieczorekWieczorek (FM)(FM)––UnderventilatedUnderventilated fires, validation datafires, validation dataSimoSimo HostikkaHostikka (VTT) (VTT) –– Radiation heat transferRadiation heat transferMarino Marino didi MarzoMarzo (UMD) (UMD) –– Droplet heat transferDroplet heat transfer

Fire vs. Combustion Fire vs. Combustion SimulationSimulation

Combustion simulation Combustion simulation –– Numerical modeling Numerical modeling of the physical and chemical processes of the physical and chemical processes related to combustion at highly resolved related to combustion at highly resolved temporal and spatial scales.temporal and spatial scales.Fire simulation Fire simulation –– Large scale numerical Large scale numerical modeling of combustion and transport modeling of combustion and transport processes at the dominant hydrodynamic processes at the dominant hydrodynamic length and time scales.length and time scales.

Guiding Development Guiding Development PrinciplesPrinciples

Target user is the practicing FPE/AHJTarget user is the practicing FPE/AHJCode must be Code must be ““easyeasy”” to useto use

•• Creation of input filesCreation of input files•• Usability of output filesUsability of output files

Code must be low cost (hardware+software)Code must be low cost (hardware+software)Code must be fastCode must be fast

Keep Keep submodelssubmodels of similar relative accuracyof similar relative accuracy

HydrodynamicsHydrodynamicsConservation of MassConservation of Mass

Conservation of SpeciesConservation of Species

Conservation of MomentumConservation of Momentum

Divergence (Conservation of Energy)Divergence (Conservation of Energy)

uut

rr⋅∇−=∇⋅+

∂∂ ρρρ

iiiii WYDuYYu

tY ′′′+∇⋅∇+⋅∇−=∇⋅+

∂∂ &rr ρρρρ

( )( )τρρρ

ϖ ⋅∇++−=∇+×+∂∂

∞ fgutu rrvrrr 1H

⎟⎟⎠

⎞⎜⎜⎝

⎛−

−∇⋅∇+∇⋅∇+⋅∇−′′′−

=⋅∇ ∑ dtdpYDTcTkqq

pu

iiipr

0,

0 111

γρ

γγ

&r

HydrodynamicsHydrodynamicsPressure TermPressure Term

Viscosity Term

~2 121 pu ∇+∇=∇

ρrv

H

Viscosity Term

( ) ( ) ( ) ( )22

322 uudefudefCsLES

rrr⋅∇−⋅∆= ρµ

DiscretizationDiscretizationSimple Cartesian or cylindrical, Simple Cartesian or cylindrical, multiblockmultiblock grid (No body fitting)grid (No body fitting)Scalar quantities (temperature, density, Scalar quantities (temperature, density, etc.) defined at cell centersetc.) defined at cell centersVector quantities (velocity) defined at Vector quantities (velocity) defined at cell edgescell edgesDifferences 2Differences 2ndnd order in spaceorder in space

SubmodelsSubmodels

Mixture Fraction CombustionMixture Fraction CombustionFinite Volume RadiationFinite Volume RadiationSolid phaseSolid phaseLiquid phaseLiquid phase

Mixture Fraction DefinitionMixture Fraction Definition

Conserved scalar quantity: ZConserved scalar quantity: Z

Z = 0 = ambient air, Z = 1 = pure fuelZ = 0 = ambient air, Z = 1 = pure fuelIf YIf YF F and Yand YO O = 0, then Z = Z= 0, then Z = ZFF = flame = flame sheetsheet

OO

O

FF

OO

OO

FF

F

MY

M

MYY

MY

Z

υυ

υυ∞

∞

−

−−

=1

ImplementationImplementationCombine the equations for Combine the equations for conservation of oxygen and mixture conservation of oxygen and mixture fractionfraction

Apply Apply HuggetHugget’’ss relationship.relationship.

( )FZZ

OO nZD

dZdY

m=

⋅∇=′′− ˆ2

2ρ&

( )FZZ

OOO nZD

dZdY

Hq=

⋅∇∆−=′′′ ˆ2

22ρ&

State RelationshipState RelationshipStart with generic combustion equation Start with generic combustion equation for a fuelfor a fuel

Modify to allow for nonModify to allow for non--stoichiometricstoichiometricstatestate

222222222

22

22

22

22 NMYMY

OHCONMYMY

OFNO

ONOOHCO

NO

ONOF ∞

∞

∞

∞

++⎯→⎯⎟⎟⎠

⎞⎜⎜⎝

⎛++ υυυυυ

[ ]

[ ] [ ] 2222

22222

22

22

22

2

2

22

22

,1,1

2,01,0

NMYMY

xOHxMinCOxMin

OxMaxFxMaxNMYMY

OxF

NO

ONOOHCO

OHCOOF

NO

ONOF

∞

∞

∞

∞

×++

⎥⎦

⎤⎢⎣

⎡−−×+−⎯→⎯⎟

⎟⎠

⎞⎜⎜⎝

⎛+×+

υυυ

υυυυυυ

State RelationshipState RelationshipCombustion Takes Place At ZCombustion Takes Place At ZFF

For Coarse Grids, ZFor Coarse Grids, ZFF Surface Will Not Be ResolvedSurface Will Not Be Resolved

0.00.10.20.30.40.50.60.70.80.91.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Mixture Fraction (Z)

Mas

s Fr

actio

n

Methane Oxygen NitrogenCarbon Dioxide Water Vapor

ZF

Mixture Fraction SurfaceMixture Fraction SurfaceVirginia Tech Fire Compartment FDS v2 Simulation

400 kW propane fire in a 50%-scaled ISO-9705 Compartment

Radiation Heat TransferRadiation Heat Transfer

Start with gray gas radiation transport Start with gray gas radiation transport equationequation

Divide path vector over a number of Divide path vector over a number of discrete angles and apply to each grid discrete angles and apply to each grid cellcell

( ) ( ) ( ) ( )[ ]s,xIs,xIxs,xIs brrrr

−=∇⋅ κ

( ) Lijk

Lijkijk,bijkm

m

Lmm dVIIdnsIA

L

Ω−=Ω⋅∫∑Ω=

κ6

1

Radiation Heat TransferRadiation Heat Transfer

κκijkijk is is precalculatedprecalculated as a function of as a function of temperature and mixture fraction using temperature and mixture fraction using RADCAL.RADCAL.

The radiant source term, The radiant source term, IIb,ijkb,ijk, for a grid , for a grid cell is the larger of cell is the larger of σσTT44 or the radiant or the radiant fraction of the cells heat release.fraction of the cells heat release.

MultiblockMultiblock GridsGridsMultiple computational gridsMultiple computational gridsCan have different node sizesCan have different node sizesReduction of active grid cells at the expense Reduction of active grid cells at the expense of more complex boundary conditionsof more complex boundary conditions

DropletsDroplets

LaGrangianLaGrangian superdropsuperdrop..RosinRosin--RammlerRammler size distribution for spray size distribution for spray nozzles with user defined angular dependent nozzles with user defined angular dependent spray pattern (velocity and mass flux)spray pattern (velocity and mass flux)Evaporation governed by droplet heat Evaporation governed by droplet heat transfer and local equilibrium vapor mass transfer and local equilibrium vapor mass fraction (fraction (ClausiusClausius--ClapeyronClapeyron ))Droplet absorption scattering added to Droplet absorption scattering added to radiation transport equationradiation transport equation

Droplets + RadiationDroplets + RadiationRight Wall Hot, Cold SprayRight Wall Hot, Cold Spray

ExamplesExamples

Sprinkler effectivenessSprinkler effectivenessLarge outdoor fireLarge outdoor fireImpinging spray fireImpinging spray fire

Sprinkler ActivationSprinkler Activation((McGrattanMcGrattan and Stroup, 1997)and Stroup, 1997)

6767’’11””

SprinklersSprinklersw/10w/10’’ Spacing

Draft CurtainDraft CurtainSpacing

44’’x8x8’’ Roof VentRoof Vent

7171’’22””

FDS v1Test

Time to ActivateTime to Activate 1:091:28

1:111:12

2:362:52

2:343:58

DNO6:52

2:112:06

2:163:30

1:111:28

1:121:20

2:222:38

2:264:20

2:455:48

2:442:40

~4.5 MW Heptane~4.5 MW HeptaneSpray FireSpray Fire

Sprinkler EffectivenessSprinkler Effectiveness

Sprinkler

Fire Origin

Sprinkler

Fire Origin

Time (s)

Hea

tRel

ease

Rat

e(k

W)

Link

Tem

pera

ture

(°C

)

0 100 200 300 400 500 6000

200

400

600

800

1000

1200

1400

1600

0

20

40

60

80

HRR w/o SprinklersHRR w/ SprinklersLink Temp FirstLink Temp Second

Sprinkler EffectivenessSprinkler Effectiveness

Tank FarmTank Farm

Tank Farm Fire w/ and w/o Tank Farm Fire w/ and w/o WindWind

Heptane Spray FireHeptane Spray Fire

Impinging Spray FireImpinging Spray Fire