cfx-intro_14.0_ws03_multi-species-postpro.pdf

7/29/2019 CFX-Intro_14.0_WS03_Multi-Species-Postpro.pdf

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2011ANSYS,Inc. January16,20121 Release14.0

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

Introduction part1:

long

version Setup Solving Proceed

to

Part

2.


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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.

Introduction part1:

long


to

Part

2.


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Ifdoing

the

short

version

(postprocessing only)

pleasejumptopage26now

Introduction part1:

long


to

Part

2.


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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)

Introduction part1:

long


to

Part

2.


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StartingWorkbench OpenWorkbench

Start>Programs>ANSYS14.0>Workbench14.0

DragaCFXAnalysisSystemintotheprojectschematic

RenamethesystemtoGarage(RMBoncellA1torenamethesystem)

Introduction part1:

long


to

Part

2.


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ImportingtheMesh

RightclickonMeshandselectImportMeshFile SetthemeshfiltertoFLUENTFiles(*.cas,*.msh)

Selectcar_and_garage.mshandclickOpen

RightclickSetupandselectEdittoopenCFXPre

Introduction part1:

long


to

Part

2.


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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

Introduction part1:

long


to

Part

2.


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DomainSpecification

DoubleclickDefaultDomain

SettheMaterialtoMixture

SettheReferencePressureto1[atm]

SetBuoyancyModeltoBuoyant SettheXandYdirectionsto0[m/s^2]

SettheZdirectiontotheexpression: g

YouneedtoclicktheEnterExpressionicon toenterthisexpression

SettheBuoyancyRef.Densityto1.1989[kg/m^3]

Introduction part1:

long


to

Part

2.


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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.

Introduction part1:

long


to

Part

2.


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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

Introduction part1:

long


to

Part

2.


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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.

Introduction part1:

long


to

Part

2.


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BoundaryConditions(FreshAir) SelectInsert>Boundary

SetNametoFreshAir

SettheLocationtovelocity_inlet_fresh_air

ClickBoundaryDetails(moresettingsonthenextpage)

Introduction part1:

long


to

Part

2.


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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

Introduction part1:

long


to

Part

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

Introduction part1:

long


to

Part

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)

Introduction part1:

long


to

Part

2.


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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

Introduction part1:

long


to

Part

2.


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BoundaryConditions(Symmetry)

Insert>Boundary SetNametoSymmetry

SetBoundaryTypetoSymmetry

SetLocationtosymmetry

ClickOK

Introduction part1:

long


to

Part

2.


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Initialization

Insert>GlobalInitialization

SetTemperaturetoAutomaticwithValue

SetTemperatureto300[K]

UnderComponentDetails,setO2toAutomaticwithValue

SetMassFractionforO2to0.23

Leaveallothersettingsattheirdefaultvalues

Thesolverwillcalculateautomaticvaluesfortheremainingvariables

Theflowisinitializedwithoutanyproductsofcombustionpresent

ClickOK

Introduction part1:

long


to

Part

2.


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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.

Introduction part1:

long


to

Part

2.


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MonitorQuantitiesNotesonmonitors:

Buoyancydrivenflowsoftenshowtransientbehavior.Forthisreason,theresidualswilloften

oscillate.Becauseofthis,convergenceshouldalwaysbejudgedbysolutionvariablemonitorsandflux

reports.Theresidualswillhowevergiveanindicationofoverallconvergencebehaviour andstability.

Incasesofanoscillatingsteadystatesolution,acommonapproachistocontinuethesimulationin

transientmode.Inmanycasestheoscillationswillreducesignificantlyafterafewtimesteps.

Theuseofsurface/volumemonitorscombinedwithresidualswillprovidethebestoveralljudgeof

solutionconvergence.

Introduction part

1:

long


to

Part

2.


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SolverControl

DoubleclickSolverControl

UnderConvergenceControl,setMax.Iterationsto250

SetTimescaleControltoPhysicalTimescale

SetaPhysicalTimescaleof5[s]

SetResidualTargetto1e5

EnableConservationTarget SetValueto0.01

ClickOK

Introduction part

1:

long


to

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

Introduction part

1:

long


to

Part

2.


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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

Introduction part

1:

long


to

Part

2.


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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.

Introduction part

1:

long


to

Part

2.


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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

Part2:Postprocessing Color Images LineGraphs ExpressionsandIntegrals Reports Summary

OR


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Postprocessing WallTemperature

AddaLocationrepresentingagroupofsurfaces

Thisletsyougroupaselectionofentitles(inthiscasewalls)andapplythesamepostprocessing

treatmenttoallitemsinthegroup.

SelectLocations>SurfaceGroup,andenterthenameGroupedWalls



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DefineLocation

details

Thedetailsofthenewlocationwillbedisplayed

inthebottomleftpane.

SelectLocations,andclickon

Expand

the

Regions

list

and

select

all

walls

EXCEPTwall_car (CTRLclicktomultipleselect).

ClickOKintheLocationSelector.



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ClicktheColorTab SetModetoVariable

SetVariabletoTemperature

SetRangetoLocal

ClickApply

ModifytheLegend DoubleclickDefaultLegend

View1

UnderAppearance:

SetPrecisionto1

ChangeScientifictoFixed

ClickApply


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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InCFDPost,clickthecameraicon

ForFormat,selectCFDViewerState(3D)

Clickthefoldericontotherightofthefilename.

Pickthedirectoryyouareworkingin(rememberthis!) Saveasfilename carstreamlines.cvf

ClickSaveinbothwindows.



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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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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


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


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


45/57


Postprocessing LineGraph

SelecttheChartIcon fromthetopToolbar

KeeptheDefaultnameChart1andclickOK UnderGeneral,settheTitleto

TemperatureProfile

UnderDataSeries SetlocationtoLine1

UnderXAxis,setvariabletoY

UnderYAxissetvariabletoTemperature

ClickApply



46/57


Postprocessing LineGraph

Notesonthegraph:

Thecomputationdomainexistsfrom

3m


47/57


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


1

2

3


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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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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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ClicktheVariablestab

RightclickanywhereinthewhitespaceundertheVariablestabandselectNew

EnteranameTemperatureC

Fromthepulldownlist,selecttheexpression

TemperatureConversioncreated

on

the

last

slide

ClickApply

Expressionscannotbeplotteddirectly:theyneedtobeassignedtoa

Variable


i i


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(TopLeft)selectOutlinethendoubleclickonChart1

UnderYAxischangethevariablebyclickingonthe...

icon

Selectthevariable

TemperatureC

ClickOKthenclickApply

Atthebottomofthescreenchangefrom3DViewerto

ChartViewer

Usethis

new

temperature

on

the

Chart

createdearlier


P i E i


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Thegraphnowshowstheresultoftheexpression


P t i R t


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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.


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.


State files and Optional Extra work


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StatefilesandOptionalExtrawork

TheReportsfeaturejustdemonstratedwillletyoucustomisetheformatofyourreport.

Ifyouhavefinishedthisexerciseaheadoftherestoftheclass,tryexperimentingwiththeReportoptionsinthelefthand

toolbar.

Youcanchoosewhichobjectsarevisible,addyourowncompanylogo,oraddlinesoftexttoexplainthecontentofthereport.


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.


cfx-intro_14.0_ws03_multi-species-postpro.pdf

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