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14.0Release
IntroductiontoANSYS
CFX
Workshop03MultiSpeciesFlowandPostprocessing
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In this workshop you will analyze the release of heat and combustion gases
from a single car with an engine fire in a ventilated parking garage. The
simulation will be run steady state assuming the fire has reached a stable
developed stage.
Simulation Physics & Boundary Conditions Mixture of N2, O2, CO2 and H20
0.1 kg/s combustion gases (H2O and CO2) at 1200 K
80 N/m3 momentum source in jets
Introduction
Fresh Air Inlet
velocity_inlet_fresh_air
Jet Fan
fluid_jet_fan
Heat and gas release from fire
mass_flow_inlet_car_fire_source
Air Outlet
pressure_outlet_all_air
Symmetry Planesymmetry
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ImportantNote
NOTE:
Thisworkshophasbeendesignedtobecompletedinoneoftwoways.Please
checkwith
your
trainer
on
whether
you
are
to
take
the
short
or
long
option.
[ShortOption] This workshopcanbeusedjusttodemonstratepostprocessinginCFDPost. Prepreparedresultsfilesaresupplied,sopleasejump
straightto
page
26
for
post
processing
[LongOption] Followalltheinstructions,whichwilldemonstratehowtosetupamultispeciessimulationofacarfire. Oncethemodelissetup,youcan
chooseto
wait
for
it
to
converge,
or
then
replace
your
results
with
the
suppliedprepreparedset.
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Ifdoing
the
short
version
(postprocessing only)
pleasejumptopage26now
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LearningAims:
Thefirstpartofthisworkshopwillshowhowtosetupamultispeciesproblem.
Thedomainwillcontainablendofseveraldifferentgases(nitrogen,oxygen,
carbondioxide,watervapour)
Othertopicsthatwillbeintroducedare:
Includinggravitational(buoyancy)effects
Settingamomentumsourcetermtoaccountforajetfan
LearningObjectives:
TounderstandhowCFXcanbeusedtosimulatemixturesoffluids,andaccount
forbuoyancyeffects. Notethatamultispeciesproblemlikethisassumesthat
thecomponentsaremixedatamolecularlevel(asnormallyhappenswithgases).
Thealternativeisamultiphaseproblemwherethereisanidentifiableboundary
betweenthe
components
(either
droplets
/particles
/bubbles,
or
afree
surface). MultiphaseworkshopsincludeWorkshop2(DPM)andWorkshop7
(TankFlush)
I Objectives(FlowSimulationPart)
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StartingWorkbench OpenWorkbench
Start>Programs>ANSYS14.0>Workbench14.0
DragaCFXAnalysisSystemintotheprojectschematic
RenamethesystemtoGarage(RMBoncellA1torenamethesystem)
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ImportingtheMesh
RightclickonMeshandselectImportMeshFile SetthemeshfiltertoFLUENTFiles(*.cas,*.msh)
Selectcar_and_garage.mshandclickOpen
RightclickSetupandselectEdittoopenCFXPre
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MaterialSpecification
IntheOutlinetree,rightclickMaterialsandselectInsert>Material
SettheNametoMixtureandclickOK
SetOptiontoVariableCompositionMixture
ForMaterialsList,clicktheicontotherightofthedropdownlist ,andthenclicktheImport
LibraryDataicon(asshownontheupperright)
UnderGasPhaseCombustion,holddownthe
key
as
you
select
the
following
materials:CO2,H2O,N2,O2
ClickOKtoimportthemandclosetheImportform
Now,selectthesameMaterialsundertheMaterialsListform
ClickOKtoclosetheMaterialsListform ClickOKtocompletespecifyingtheMixture
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DomainSpecification
DoubleclickDefaultDomain
SettheMaterialtoMixture
SettheReferencePressureto1[atm]
SetBuoyancyModeltoBuoyant SettheXandYdirectionsto0[m/s^2]
SettheZdirectiontotheexpression: g
YouneedtoclicktheEnterExpressionicon toenterthisexpression
SettheBuoyancyRef.Densityto1.1989[kg/m^3]
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OperatingConditionsNotes:
ANSYSCFX avoidstheproblemofroundofferrorbysubtractingtheoperatingpressure(generallya
largepressureroughlyequaltotheaverageabsolutepressureintheflow)fromtheabsolute
pressure,andusingtheresult(termedthegaugepressure).Theabsolutepressureissimplythesum
oftheoperatingpressureandthegaugepressure.
BuoyancyReferenceDensityisalsoavalueforavoidingroundoff errors.Forsimulationswhere
pressureboundaryconditionsarepresentitisimportanttosetthevaluecorrectlyotherwisethe
pressureattheboundarywillbeincorrectandmayleadtounphysicalflowconditions.Hereyouhave
toset
it
to
the
density
that
will
exist
at
the
opening
boundary
condition
(set
later)
agas
at
293.15
K
with23%O2 and77%N2.
Bydefault,CFXwillenforcethisdensityatnodenumber1inthemesh,whichissufficientforthis
workshop.Othercasesmayrequiresettingthereferencedensityataspecificlocation.Thiscanbe
doneby
specifying
the
option
Cartesian
Coordinates.
SearchthehelpdocumentationusingthekeywordBuoyancy formoredetails.
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FluidModels
OntheFluidModelstab: SetHeatTransfertoTotalEnergy
Thisenablesthefullbuoyancymodel
Other
settings
on
the
form
can
be
left
at
their
defaults
Thekepsilonturbulencemodelisselectedbydefault
Turbulencemodelling,aswithallphysics
modelling,is
acomplex
area.
There
are
many
applicationspecificoptions.Thekepsilonmodelis
asimplebutrobustmodel.Thedocumentation
providesfurtherguidanceonwhichmodelstouse
forspecificapplications.
ClickOKtocompletethespecificationofthedomain
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ForcedconvectionmodellingaFan
RightclickDefaultDomainandselectInsert>Subdomain
SetNametoFanandclickOK
SetLocationtofluid_jet_fan ClicktheSourcestab
EnableSources,MomentumSource/PorousLoss,thenGeneral
MomentumSource
SettheYComponentto80[kgm^2s^2]
Setothercomponentsto0[kgm^2s^2]
ClickOKWe
need
to
account
for
the
air
movement
produced
by
the
ceiling
jet
fan.
Here
we
have
done
this
byaddingmomentumtothesubdomain whichislocaltothejet. Theadvantageofthistechnique
(overusingapairofvelocityboundaryconditions)isthatwepreservethespecies(smoke)
concentrationthroughthefan. Ifwehadusedvelocityboundaryconditions,wewouldhaveneeded
touseexpressionsattheintaketothejetfan,andapplythemtothejetfandischarge.
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BoundaryConditions(FreshAir) SelectInsert>Boundary
SetNametoFreshAir
SettheLocationtovelocity_inlet_fresh_air
ClickBoundaryDetails(moresettingsonthenextpage)
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BoundaryConditions(FreshAir) OntheBoundaryDetailstab:
SetMassandMomentumtoNormalSpeed
SetNormalSpeedto0.8[m/s]
SetHeatTransfertoStaticTemperature
SetStaticTemperatureto20[C]
Notetheunitsfortemperature
SetthefollowingComponentMassFractions:
CO2: 0.0
H2O:
0.0
O2: 0.23
ClickOK
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2.
Themixturespeciescontains4components (h2o,o2,co2,
andn2).
Youdonotneedtoenteramassfractionforn2. Itwill
automaticallyaccountfortheremainingfractionnotusedby
thefirstthree(inthiscase0.77)
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BoundaryConditions(AirOutlet) Insert>Boundary
SetNametoAirOutlet
SetBoundaryTypetoOpening
SetLocationtopressure_outlet_all_air
ClickBoundaryDetails
SetMassandMomentumtoOpeningPres.AndDirn
SetRelativePressureto0[Pa]
SetHeatTransfertoOpeningTemperature
SetTemperatureto20[C] (asforpreviousBC)
SetthefollowingComponentMassFractions:
SetO2 to0.23
Settheothercomponentmassfractionsto0
ClickOK
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2.
Solongasthereisonlyflowoutofthedomainhere,thesevaluesforturbulence,temperature
andspecieswillnotbeneeded. Howeverduringthesolutionprocesstheremaybesomeinflow
thoughthisboundary,andthereforeCFXneedstoknowwhatvaluestoapply.
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Insert>Boundary
SetNametoExhaust
SetLocationto
mass_flow_inlet_car_fire_source
ClickBoundaryDetails
SetMassandMomentumtoMassFlow
Rate
SetMassFlowRateto0.1[kgs^1]
Set
Heat
Transfer
to
Static
Temperature
SetStaticTemperatureto1200[K]
SetthefollowingComponentMass
Fractions:
CO2:
0.568
H2O: 0.432
O2: 0
ClickOK
BoundaryConditions(Exhaust)
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BoundaryConditions(Walls) Insert>Boundary
SetNametoWalls
SetBoundaryTypetoWall
SetLocationtowalls_outer,wall_floorandwall_ceiling
Usethekeytoselectmultipleboundaries
ClickBoundaryDetails SetHeatTransfertoHeatTransferCoefficient
SetHeatTrans.Coeff to5[Wm^2K^1]
SetOutsideTemperatureto300[K]
Thisboundary
condition
is
intended
to
simulatetheeffectofasolidmaterialbetween
theCFDdomainandtheairoutsidethegarage,
forexample,aconcretewall.
ClickOK
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BoundaryConditions(Symmetry)
Insert>Boundary SetNametoSymmetry
SetBoundaryTypetoSymmetry
SetLocationtosymmetry
ClickOK
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Initialization
Insert>GlobalInitialization
SetTemperaturetoAutomaticwithValue
SetTemperatureto300[K]
UnderComponentDetails,setO2toAutomaticwithValue
SetMassFractionforO2to0.23
Leaveallothersettingsattheirdefaultvalues
Thesolverwillcalculateautomaticvaluesfortheremainingvariables
Theflowisinitializedwithoutanyproductsofcombustionpresent
ClickOK
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MonitorQuantities
Insert>Solver>OutputControl
CreateanewMonitor SetNametoAverageTemperature
SetOptiontoExpression SetExpressionValueto
volumeAve(T)@DefaultDomain Createtwonewmonitorsinthesame
way: Name:HeatFlowthroughFloor
Expression:areaInt(WallHeatFlux)@REGION:wall_floor
Name:FanIntakeMassFlowRate
Expression:massFlow()@REGION:Primitive 2DB
ClickOK
Themonitorpointswilltrackaverage
temperatureinthedomain,totalheatflux
throughthefloorregion,andmassflowthrough
thesimulated
fan
region
Theregionwheremassflowismonitoredwas
nottaggedasaNamedSelection,sothemesh
regionoftheprimitiveCADsurfacethat
representsitwaschosenhere.
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MonitorQuantitiesNotesonmonitors:
Buoyancydrivenflowsoftenshowtransientbehavior.Forthisreason,theresidualswilloften
oscillate.Becauseofthis,convergenceshouldalwaysbejudgedbysolutionvariablemonitorsandflux
reports.Theresidualswillhowevergiveanindicationofoverallconvergencebehaviour andstability.
Incasesofanoscillatingsteadystatesolution,acommonapproachistocontinuethesimulationin
transientmode.Inmanycasestheoscillationswillreducesignificantlyafterafewtimesteps.
Theuseofsurface/volumemonitorscombinedwithresidualswillprovidethebestoveralljudgeof
solutionconvergence.
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SolverControl
DoubleclickSolverControl
UnderConvergenceControl,setMax.Iterationsto250
SetTimescaleControltoPhysicalTimescale
SetaPhysicalTimescaleof5[s]
SetResidualTargetto1e5
EnableConservationTarget SetValueto0.01
ClickOK
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1:
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version Setup Solving Proceed
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Part
2.
Theconservation
target
sets
aminimum
level
of
imbalanceinformationforthesolvedquantities.
Inthiscase,thesolverisaimingfor1%
imbalance.
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Solution(Optional)
CloseCFXPre
Thesolutionmaytake3060minutestocomplete
Aresultsfileisprovidedinthisworkshopifyoudonotwishtosolve
thecase.Tousetheprovidedresults
file,gotothenextpage
Tosolvethecasemanually: RightclickSolutionandselectEdit.
WhentheSolverManageropens,clickStartRun
Skip
the
next
page
of
instructions
and
continuefromMonitoringtheSolution
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UsingProvidedResults(Optional)
Tousetheprovidedresultsfile: Browsetotheresultsfilegarage_001.res
usingWindowsExplorer
Draggarage_001.resintoANSYSWorkbench.The
system
will
appear
as
aseparate
componentintheProject
Inthenewsystem,rightclickSolutionandselectDisplayMonitors
TheSolverManagerwindowwillopentoshowthediagnosticinfoassociatedwiththe
suppliedresultsfile
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MonitoringtheSolution
ClicktheUserPointstabLookingattheheatflowthroughthefloor,
itisclearthattherearesometransient
characteristicstotheflow.Thisworkshop
hasassumed
that
the
flow
can
be
treated
assteadystate,butforahigherfidelity
solution,atransientstudywouldlikelybe
necessary
ViewtheResiduals
Althoughconvergence
is
below
1e
4,
oscillationscanbeseenintheRMS
residualswhichhelptoaffirmpossible
transientsolutionbehaviour
Thesolutioninthiscaseterminated
becausethemaximumnumberof
iterations,250,
was
reached,
not
because
thesolutionconvergedtotherequired
level.
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Postprocessing inCFD_POST
Part
2:
Postprocessing Color Images Line
Graphs Expressions
and
Integrals Reports Summary
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LearningAims:
Thisworkshopisdesignedtoteacharangeofskillsinpostprocessing resultsfilesusingCFD
Post. Topicstobecoveredinclude:
Creatingsurfacegroups Creatinglinegraphs
Creatingisosurfaces
Creating
expressions
(CEL)
Creatingportable(.cvf)images Performingintegrals
Creatingautomaticreports Volumerendering
LearningObjectives:
TounderstandthewaysinwhichCFDPostcanbeusedbothforhighqualityimages,aswell
asproducingquantitativedatafromvolume/surfaceintegrals,andwritingcustom
functions.
I Objectives(Postprocessing)
Part
2:
Postprocessing Color Images Line
Graphs Expressions
and
Integrals Reports Summary
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ResultsPreparation
Ifyouhavesetuptheproblemmanually,theresultsfilewillalreadybeavailable.
IfyouareonlyperformingPostprocessing inthis
workshop Browsetotheresultsfilegarage_001.resusing
WindowsExplorer
Draggarage_001.resintoANSYSWorkbench.The
systemwillappearasanewcomponentofthe
Project
RightclickResultsandselectEdit
CFDPostwillopenandloadtheresultsfile
Dependingonthepathchosen,youwillbeloadingresults
fromacomplete
analysis
system
(top
right)
or
asolution
component(bottomright).ToensureResultsarevalid,
checktoseethatSolutionhasagreencheckbox
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Postprocessing WallTemperature
AddaLocationrepresentingagroupofsurfaces
Thisletsyougroupaselectionofentitles(inthiscasewalls)andapplythesamepostprocessing
treatmenttoallitemsinthegroup.
SelectLocations>SurfaceGroup,andenterthenameGroupedWalls
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Postprocessing WallTemperature
DefineLocation
details
Thedetailsofthenewlocationwillbedisplayed
inthebottomleftpane.
SelectLocations,andclickon
Expand
the
Regions
list
and
select
all
walls
EXCEPTwall_car (CTRLclicktomultipleselect).
ClickOKintheLocationSelector.
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Postprocessing WallTemperature
ClicktheColorTab SetModetoVariable
SetVariabletoTemperature
SetRangetoLocal
ClickApply
ModifytheLegend DoubleclickDefaultLegend
View1
UnderAppearance:
SetPrecisionto1
ChangeScientifictoFixed
ClickApply
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Thisoptionhasallowedustoproduceatemperature
contourplotofidenticalcolourrangeonagroupofsurfaces.
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Postprocessing GeneratingaFigure
Generateafigureforuselaterinareport.
ClicktheFigureicon
EnternameFigure1Wall
Temperature OKtotheInsertFigurepanel.
Rememberwherethisoptionis(youwill
beaskedtouseitseveraltimeson
subsequentslides).
Wewillbecreatingseveralfiguresaswe
progressthroughthisworkshop.
Lateronwewilldemonstratehowtouse
thesefigures
to
automate
report
writing.
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Postprocessing SectionPlane
FirstdeselectthecheckboxnexttoGroupedWallstoturn
offvisibilityfortheobject
AddaLocationrepresentinga
sectionplane
SelectLocation>Isosurface
SetNameto xzplaneandclick
OK.
Under
Geometry
tab
set
DefinitionVariabletoY
Valueto9[m]
ClickApply
Continuedonnextslide..
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Postprocessing SectionPlane
Onthe Colortab,setModetoVariable
SettheVariableto
Temperature UnderRenderdisable
Lighting
ClickApplytodisplay
GenerateanewFigure,andnameit Figure2
TemperatureSlice
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Postprocessing QuickAnimation
ClicktheAnimationbuttoninthetoptoolbar
SelectQuickAnimation
Highlightxzplane
PressthePlaybutton ,andwatchthedisplay.
Whenfinished,usethestopbutton thenClose.
Ifrequired,thisanimationcouldbesavedtodiskinMPEG/
AVIformats.
ThealternativetoQuickAnimationisKeyframe Animation. Tousethisyousetaseriesofkeyanimationframes. Thesemighthavedifferentobjectsvisible,differentpointsina
transientsimulation,ormighthavethemodelrotatedatadifferentviewingangle. The
animationwillprogresssmoothlybetweenthesestates.
Theslicethroughthemodelgivesusausefulindicationofwhatis
happeninginthemiddleofthedomain. Aquickanimationwill
transversethisslicethroughthemodelsowecanseewhatis
happeningelsewhere.
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Postprocessing 3DIsosurface
First,changethelookofthedisplay: Hidetheplanexzplanepreviously
createdbyuncheckingitinthemodel
tree
Expandthetopofthemodeltree,expanding MeshRegions
Doubleclickonwall_car
Ensurethatthedetailsboxshows
wall_car!
ForColorselectconstant,andpickyellow
ClickApply
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Postprocessing 3DIsosurface
Adda3DIsosurface representinggases SelectLocation>Isosurface
KeepthedefaultnameIsosurface 1
SettheVariabletoCO2.Mass.Fractionandthevalueto0.001
SetColortobeconstant(usethedefaultgreycolour),thenClickApply
GenerateanewFigure:
Figure
3
CO2
Isosurface
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Postprocessing Streamlines
Add3DStreamlinestovisualizeflow HidetheIsosurface createdinthepreviousstep(uncheckinmodeltree)
ClicktheStreamlinebutton andkeepdefaultname(Streamline1)
StartFrom:FreshAir
#ofPoints: 100
UnderColorset
Mode:UsePlotVariable
Range: Local
ClickApply
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Postprocessing PortableCVFFiles
NotonlycanCFDPostexportregularimageformats(jpg/png),butinaddition3Dimagescanbesaved.
Theseimageshavethefileextension.cvf
TheycanbeviewedusingafreeCFDviewerthatcanbedownloadedfromtheANSYSwebsite. (Goto
www.ansys.com,and
search
for
CFD
Post
Viewer)
Nolicenseisrequiredtousetheviewer,soyoucaninstallthisonanycomputer(e.g. laptopusedfor
presentations,oraskyourclient/customer toalsodownloadandinstallacopy).
The3D
image
can
be
viewed
using
rotate
/pan
/zoom
functionality
just
as
in
CFD
Post,
and
can
also
be
embeddedinMSPowerpoint. Howevertheusercannotmodifytheimage,theycannotadd/removeobjectsfromtheimage,oraltercolour ranges.Thisisareallypowerfultoolforwhenyoucometopresentyourprojectwork. Inmanycasesa2Djpeg
imagecannot
explain
3D
flow
features.
However
rotating
the
model
live
in
front
of
your
audience
will
helpconveyyourfindings.
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Postprocessing PortableCVFFiles
InCFDPost,clickthecameraicon
ForFormat,selectCFDViewerState(3D)
Clickthefoldericontotherightofthefilename.
Pickthedirectoryyouareworkingin(rememberthis!) Saveasfilename carstreamlines.cvf
ClickSaveinbothwindows.
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Postprocessing PortableCVFFiles
Minimise CFDPost,anduseWindowsExplorertobrowsetothefolderusedonthelastslide.
Notehowthisfile(carstreamlines.cvf)isquitesmall(inthiscaseabout170kB(butitwillvarydependingonzoomlevel),and
thereforeeasy
to
email
to
your
client
or
manager).
Doubleclicktoopenthisfile (itwilltakeafewmomentstolaunchtheviewerapplication)
If
you
have
ANSYS
R14
installed
on
your
machine,
your
computer
will
already
have
theviewer,andwillrecognizethisfileextension. Youonlyneedtodoaseparate
installationofCFDPostViewer(fromtheANSYSwebsite)onmachinesthatdonot
haveWorkbenchinstalled.
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Postprocessing PortableCVFFiles
CFDPostViewerwilllookjustlikethegraphicalwindowofCFDPost
Useleftmousebuttontorotate
Middlemousebutton(orwheel)tozoom
Rightmousebuttontotranslate
Typequestionmark?foralistofhotkeys
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Postprocessing VolumeRendering
ClosethestandaloneviewerandreturntoCFDPost
Hidethestreamlinesplotbyuncheckinginmodelview
SelectInsert>VolumeRenderingandsetNametoGasCloud
UnderGeometry,setCO2.MassFraction KeeprangeasGlobal,thenclickApply
Tomakeiteasiertoseetheimage,changethescreenbackgroundcolour to
white: Edit>Options>CFDPost>Viewer
SetColorTypetoSolid
SetColortowhite
ClickOK
Part2:Postprocessing Color Images LineGraphs ExpressionsandIntegrals Reports Summary
Thisoptionappliesavariablecolourandtransparencyto
eachgridcelldependingontheplotvariable. For
applicationslikethisinvolvingsmokemovementitmakesit
easyfortheeyetoassesswherethecloudisconcentrated.
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Postprocessing Quantitative
CreateaLinethroughthemodel HidetheGasCloudvolumerenderingobject
Location>Line andkeepdefaultnameLine1.
SetMethodtoTwoPoints
From
X=18
Y=3
Z=2
From X=18 Y=18 Z=2
SetSamplesto40
ClickApply
Part2:Postprocessing Color Images LineGraphs ExpressionsandIntegrals Reports Summary
Untilnow
we
have
used
CFD
Post
to
create
colour
images
to
help
interpret
the
CFD
results
Nextwewilllookatsomequantitativetechniquesforextractingnumericaldata(volume
integrals),andproducinglinegraphs.
Itisalsopossibletowriteyourownarithmeticexpressionsforcustompostprocessing.
Thishas
created
ahorizontal
line
through
the
model,
passing
abovethefrontofthecar
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Postprocessing LineGraph
SelecttheChartIcon fromthetopToolbar
KeeptheDefaultnameChart1andclickOK UnderGeneral,settheTitleto
TemperatureProfile
UnderDataSeries SetlocationtoLine1
UnderXAxis,setvariabletoY
UnderYAxissetvariabletoTemperature
ClickApply
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Postprocessing LineGraph
Notesonthegraph:
Thecomputationdomainexistsfrom
3m
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Postprocessing VolumeIntegrals
SelectCalculatorstab
SelectFunctionCalculator Function: volumeInt (forVolume
Integral)
Location: DefaultDomain
Variable: CO2.Mass.Fraction ClickCalculate
Theresultisabout1.15m^3ofCO2
Theonlysourceofcarbondioxide(CO2)inthemodelisfromthecarfiresource(theinletjustcomprisesoxygenandnitrogen). Wewillperformavolumeintegraltofind
outhowmuchco2ispresentinthemodel.
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Postprocessing Expressions
SelecttheExpressionstab
RightclickinthewindowandselectNew EnternamePressureDropthenclickOK
Enterthefollowingexpression,thenclickApply ave(Pressure)@FreshAir
Note:rightclickmenuusageshownbelow
Theanswerisapproximately31Pa.
Itis
possible
to
write
your
own
arithmetic
functions
for
post
processing,
making
use
of
the
data
exportedbythesolver. Theresultingexpressionmayeitherreturnasinglevalue(firstexample,
below),orproduceaquantitythatvariesspatiallyforuseinacontourplot/linegraph
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1
2
3
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Postprocessing Expressions
Part2:Postprocessing ColourImages LineGraphs ExpressionsandIntegrals Reports Summary
Notehow
Pressure
turns
to
italicsassoonasyoutypeit.
Itisimportanttomakethefirst
letteracapitalP
Forafulllistofavailable
variables,
right
click
in
this
windowandselectVariables
ave returnsthe
average
at
the
locationspecifiedbythe@
Foralistoffunctionsavailable,
rightclickinthewindowand
selectFunctions>CFDPost
Thisisthenameoftheboundarythatyouareperforming
theaveragefunctionon.
For
a
full
list
of
locations,
right
click
and
select
Locations
Notethattocomputethepressuredrop,wedidnotneed
toaddtheoutletboundary ... ave(Pressure)@AirOutlet
TheoutletboundarywassettobeapressureoutletinCFX
withapressureof0Pa. Thistermwouldreturnazero
value tryitifyoulike!
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Postprocessing Expressions
Asasimpleexample,letsconverttemperaturefromKtoCandplotthisonagraph
Expressions>New SetNameto TemperatureConversion
Enterthisexpression: Temperature/1[K] 273.15 ClickApply
Theprocedure
to
create
an
expression
that
can
be
plotted
spatially
is
verysimilar,thereisjustoneadditionalsteptoassignittoavariable
Note:
InitialcapitalsforTemperature. Itwillturntoitalicsifcorrect.
Expressionsmustbalancedimensionally.
WecannotjustenterTemperature 273.15 sinceTemperaturehasaunit[K]
Bydividing
by
1[K]
we
remove
the
temperature
unit.
WecouldinsteadenterTemperature 273.15[K]
Thisexpressionisvalid,but wouldreturnavaluewithunits[K]whichwouldbemisleading.
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Postprocessing Expressions
ClicktheVariablestab
RightclickanywhereinthewhitespaceundertheVariablestabandselectNew
EnteranameTemperatureC
Fromthepulldownlist,selecttheexpression
TemperatureConversioncreated
on
the
last
slide
ClickApply
Expressionscannotbeplotteddirectly:theyneedtobeassignedtoa
Variable
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Postprocessing Expressions
(TopLeft)selectOutlinethendoubleclickonChart1
UnderYAxischangethevariablebyclickingonthe...
icon
Selectthevariable
TemperatureC
ClickOKthenclickApply
Atthebottomofthescreenchangefrom3DViewerto
ChartViewer
Usethis
new
temperature
on
the
Chart
createdearlier
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Postprocessing Expressions
Thegraphnowshowstheresultoftheexpression
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Postprocessing Reports
Intheoptionsbelowthegraphicwindow,selectReportViewer
SelectRefresh
Reviewwhatisshowninthereportwindow. Youcansee: Nameoftheresultsfile
Meshsummary
ListofBoundaryconditions
AlltheFiguresandChartsproducedduringthisworkshop
Ifyou
select
Publish
this
will
be
written
outinhtmlformat,alongwithcopiesof
alltheresultsimages.
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St t fil d O ti l E t k
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StatefilesandOptionalExtrawork
UseFile>Savestateas... andsavetoyourworkingdirectory.
Thisstatefilestoresallthepostprocessingsettingsyouhavecreated.
Ifyouhavedonethelongversionofthisworkshop,youwillrecallthatweranforafixednumber
ofiterations,
and
wanted
to
examine
the
results
to
help
us
determine
ifthe
model
had
converged
ornot. (Theresidualswerestuckandfurtheriterationswouldnotlowertheresiduals). Itmight
bebe necessarytorevisitthemodelsetup,bymovingtoatransientscheme,ormodifyingthe
modellingsettings. Ausefulassessmentofconvergenceistoseeiftheresultsofinterestremain
unchangedasthesolversettingsareenhanced.
Thebigadvantageofhavingthisstatefileisthatifyouchoosetomodifythesolversettingsand
rerunthismodel,youcanquicklyreproducetheequivalentpostprocessingimages. Simplyload
thenewresultsfile,thenloadthisstatefile.
Likewise,itiscommoninprojectworktohaverunaseriesofmodelstotestthedifferent
operatingconditions.
This
technique
will
let
you
generate
equivalent
images
so
as
to
produce
agoodlikeforlikecomparisoninyourpresentation/report.
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State files and Optional Extra work
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StatefilesandOptionalExtrawork
TheReportsfeaturejustdemonstratedwillletyoucustomisetheformatofyourreport.
Ifyouhavefinishedthisexerciseaheadoftherestoftheclass,tryexperimentingwiththeReportoptionsinthelefthand
toolbar.
Youcanchoosewhichobjectsarevisible,addyourowncompanylogo,oraddlinesoftexttoexplainthecontentofthereport.
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Wrap up
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Wrapup
CFDPostisaverypowerfulpostprocessingtool,andcapableofproducinghighqualityimagesquicklyandeasily.
Inthisworkshopwehaveshownhowtoproducecontourplots,streamlines,andisosurfaces (asseeninsomeotherworkshops
forthis
course)
InadditionyouhaveusedCFDPosttoperformvolumeintegrals,createlinegraphs,andtocreateyourownarithmeticexpressions
forpostprocessing.
3Dimagescanbesavedtodisk,andviewedinafreewareviewer.Thisaddsmuchimpacttopresentations,andcanberunonany
computer(nolicenseneeded).
CFD
Post
can
also
automate
the
report
generation
process. Postprocessing isbestlearnedbypractice. Ifyouhavetimenow,
tryexploringtheotherbuttonsintheinterface.
Part2:Postprocessing ColourImages LineGraphs ExpressionsandIntegrals Reports Summary