1、ModelingUniformFluidizationin2DFluidizedBed cFluentInc.November22,2006 cFluentInc.November22,2006 cFluentInc.November22,2006Tutorial:ModelingUniformFluidizationin2DFluidizedBedIntroductionThepurposeofthistutorialistostudythehydrodynamicsandbubbleformationinafluidizedbedoveraperiodoftime.Italsodemons

2、trateshowtocustomizeadraglawforgranulargas-solidflow.ThedefaultdraglawinFLUENTistheSyamlal-OBriendraglaw.Thislawworksforalargevarietyofproblems,buthastobetunedproperlyforpredictingtheminimumfluidizationconditionsaccurately.Thistutorialdemonstrateshowtodothefollowing:Customizeadraglawforgranulargas-s

3、olidflow.UsetheEularianmodelstopredictthepressuredropinanuniformlyfluidizedbed.Solvethecaseusingappropriatesolversettings.Postprocesstheresultingdata.PrerequisitesThistutorialassumesthatyouarefamiliarwiththeFLUENTinterface,andhaveagoodunderstandingofbasicsetupandsolutionprocedures.Thistutorialwillno

4、tcoverthemechanicsofusingtheEularianmodels.Itwillfocusontheapplicationofthesemodels.IfyouhavenotusedthesemodelsbeforeFLUENT6.3TutorialGuidewillprovideyouwiththenecessaryexperience.ProblemDescriptionThepredictionofpressuredropinanuniformlyfluidizedbedisaproblemoflongstandinginterestintheprocessindust

5、ry.TheEulerianmodelsinFLUENTprovideanimportantmodelingtoolforstudyingdensephaseparticulateflowinvolvingcomplexinter-phasemomentumtransfer.Despiterigorousmathematicalmodelingoftheassociatedphysics,thedraglawsusedinthemodelcontinuetobesemi-empiricalinnature.Therefore,itiscrucialtouseadraglawthatcorrec

6、tlypredictstheincipientorminimumfluidizationconditionswherethebedofparticlesisessentiallyinastateofsuspensionasaresultofthebalancebetweeninterfacialdragandbodyforces.ThedefaultSyamlal-Obrienisasfollows:Thefluid-solidexchangecoefficientis蔦1P1CD/非可1r,ssr,swherev2r,sistheterminalvelocitycoefficientfort

7、hesolidphase.vr,s=0.5A-0.06Res+(0.06Res)2+0.12Res(2B-A)+A2r,sssswithA=414andB=0.8128for,0.85lllllThedefaultconstantsof0.8and2.65predictaminimumfluidizationof21cm/s.Theexperimentallyobservedminimumfluidizationforthisparticularcaseis8cm/s.Therefore,bychangingtheconstantswecantunethedraglawtopredictmin

8、imumfluidizationat8cm/s.Aftersomemathematicalmanipulation,theseconstanstscomeouttobe0.281632and9.07696respectively.Therefore,thesevalueshavetobeusedtopredictthecorrectbedbehaviorandarepassedtothecodethroughuser-definedfunctions.Theproblemconsideredisa1mx0.15mfluidizedbedasshowninFigure1.Theinletaire

9、ntersinat0.25m/sandthetopismodeledasapressureoutlet.Thebedispackedwithgranularsolidsat0.55volumefraction(closetopacking).Figure1:ProblemSpecificationPreparationCopythefilesbp.msh.gzandbpdrag.ctotheworkingfolder.Startthe2ddp(2ddp)versionofFLUENT.SetupandSolutionNote:Allentriesinsettingupthiscasearein

10、SIunits,unlessotherwisespecied.Step1:GridReadthegridfilebp.msh.gz.Checkthegrid.Grid-CheckDisplaythegrid.Display-Grid.w!FIT!翻*卜+H+IBrltiFLUENT6.32d,dp.pHrr=：,lam)Figure2:GraphicsDisplayoftheGridStep2:ModelsSelectPressureBasedsolverwith2DspaceandUnsteadytimecondition.Define-Models-Solver.SelecttheEule

11、rianmultiphasemodel.Dene-tModels-Multiphase.Step3:MaterialsDeine-tMaterials.Modifythepropertiesforair.Enter1.2kg/m3forDensityand1.8e-05kg/m-sforViscosity.Defineamaterialcalledsolids.Enter2600kg/m3forDensityand1.7894e-05kg/m-sforViscosity.ClickChange/CreateandclosetheMaterialspanel.Step4:CompiletheUD

12、FTheUDFcontainstwoargumentsscolandfcol.Theserefertotheindicesofthephasesappearinginthesecondandfirstcolumnsofthetableintheinteractionpanelrespectively.Thereforeinthiscasescolreferstotheindexofgasphasewhichis0andfcolreferstotheindexforsolidswhichisequalto1.Deine-tUser-Deined-tFunctions-tCompiled.Clic

13、ktheAdd.buttonintheSourceFilessectiontoopentheSelectFiledialog.Selectthefilebpdrag.c.EnterlibdragforLibraryName.ClickBuild.AWarningdialogboxwillappear,warningyoutomakesurethattheUDFsourcefilesareinthesamefolderthatcontainsthecaseanddatafiles.ClickOKtoclosetheWarningdialogbox.Youcanviewthecompilation

14、historyinthelogfilethatissavedinyourworkingfolder.ClickLoadtoloadthelibrary.Step5:PhasesDene-Phases.Selectphase-1fromthePhaseselectionlistandclicktheSet.buttontoopenthePrimaryPhasepanel.SelectairfromthePhaseMaterialdrop-downlist.EntergasforName.ClickOKtoclosethePrimaryPhasepanel.Selectphase-2fromthe

15、PhaseselectionlistandclicktheSet.buttontoopentheSecondaryPhasepanel.SelectsolidsfromthePhaseMaterialdrop-downlist.EntersolidforNameandenableGranular.Enter0.0003mforDiameter,andselectsyamlal-obrienfromtheGranularViscositydrop-downlist.Retainthedefaultvaluesfortheotherparameters.ClickOKtoclosetheSecon

16、daryPhasepanel.CheckthecolumnnumberswherethetwophasesappearinthePhaseInteractionpanel.Inthiscasesolidandgasappearinthefirstandsecondcolumnsrespectively.ThesecolumnsareusedtospecifythephaseindicesintheargumentlistfortheUDF.Setthedragcoefficient.SelectgasfromthePhaseselectionlistandclicktheInteraction

17、.buttontoopenthePhaseInteractionpanel.Selectuser-deinedandcustomdragsyam:libdragintheDragCoefficientgroupbox.ClickOKtoclosethePhaseInteractionpanel.Similarlyselecttheuser-definedfunctionforsolid(customdragsyam:libdrag).ClickOKtoclosethePhasespanel.Step6:OperatingConditionsDeine-OperatingConditions.E

18、nableGravityandenter-9.81m/s2forGravitationalAccelerationintheYdirection.EnableSpeciiedOperatingDensity,andenter1.2kg/m3forOperatingDensity.ClickOKtoclosetheOperatingConditionspanel.Step7:BoundaryConditionsDene-BoundaryConditions.Settheboundaryconditionsforvintletzone.SelectvinletfromtheZoneselectio

19、nlist,andgasfromthePhasedrop-downlist.ClicktheSet.buttontoopentheVelocityInletpanel.SelectComponentsfromtheVelocitySpeciicationMethoddrop-downlistandenter0.25m/sforY-Velocity.ClickOKtoclosetheVelocityInletpanel.SelectsolidfromthePhasedrop-downlistandclicktheSet.buttontoopentheVelocityInletpanel.Clic

20、ktheMultiphasetabandenter0forVolumeFraction.ClickOKtoclosetheVelocityInletpanel.ClosetheBoundaryConditionspanel.Step8:SolutionMarkaregionforadaption.Adapt-Region.Enter0forXMinandYMin,and0.15mforXMaxandYMaxrespectivelyintheInputCoordinatesgroupbox.ClickMarktomarkthecellsforrefinement.Note:ClickAdaptt

21、operformtherefinementimmediately.ClosetheRegionAdaptionpanel.Initializetheflowwithdefaultvalues.Solve-Initialize-Initialize.Patchthesolidsvolumefractionforhexahedron-r0.Solve-Initialize-Patch.SelectsolidfromthePhasedrop-downlistandselectVolumeFractionfromtheVariableselectionlist.Enter0.55forValueand

22、selecthexahedron-r0fromtheRegisterstoPatchselectionlist.Ifyouwishtopatchaconstantvalue,enterthatvalueintheValuefield.Ifyouwanttopatchapreviously-definedfieldfunction,enabletheUseFieldFunctionoptionandselecttheappropriatefunctionintheFieldFunctionlist.ClickPatchandclosethePatchpanel.Setthesolutioncon

23、trolparameters.Solve-Controls-Solution.RetainthedefaultselectionfromtheEquationsselectionlist.Enter0.5forPressure,0.2forMomentum,and0.4forVolumeFractionintheUnder-RelaxationFactorsgroupbox.Retainthedefaultvaluesforotherparameters.ClickOKtoclosetheSolutionControlspanel.Enableautosavingofthedatafilesf

24、orevery100timesteps.File-Write-Autosave.Setupcommandsforanimation.Solve-ExecuteCommands.F蟲ExecuteCommdQds岡DefinedCommands：2OnNameCommandTimeStepIterationIterationIteration17con)mand-1CDiniiand-Zcoininand-3con)mand-4cunniidiid-5CancelHelpDefineMacro.EveryWhen自自勻自|/display/cnntour/solid/uoFJ|Setthegra

25、phicshardcopyformat.File-Hardcopy.SelectTIFFfromtheFomatlist,andColorfromtheColoringlist.ClickApplyandclosetheGraphicsHardcopypanel.Setupthecontoursdisplay.Display-Contours.EnableFilledfromtheOptionsgroupbox.SelectsolidfromthePhasedrop-downlist.SelectPhases.andVolumeFractionfromtheContoursofdrop-dow

26、nlists.ClickDisplayandclosetheContourspanel.Startthecalculationbyrequesting1400iterationsandsettheTimeStepSizeto0.001sec.Solve-Iterate.Step9:Postprocessing1.Displaycontoursofvolumefractionforsolidat0.2sec(Figure3),0.9sec(Figure4),and1.4sec(Figure5).Display-Contours.Viewtheanimationforthefluidization

27、processusingthe.tifffilesandthecommand,animate*.tiff5.70r-O1I5.42o01f占棚亠49tC14.-5Bq4.2813.3Qt-C1fr01：-：.-|4o01|2j8Mh1Z.37r-OiI2：2B-I1IE.CWE44I1.14M1I合檔于NQI5.7De-02ZStOZO.a0eHConiDuraarvaiumeffacnah(i；olld)仃面】oae-01)FLUENT6.3(2d,dp.pbns,eulerian,lam,unEleadFigure3:ContoursofVolumeFractionofsolid(t=0.2s)I5.-3n-01I5J?4*01313135Be-0iSJlfrO!4uQ13.1BCrO12.Q2tO1|2白呂IZ.-394-012.-i2-ll1.354-01I1.5DtO1i.ontoiII6