fluent中多孔介質(zhì)設(shè)置問題和算例

經(jīng)過難過的一段經(jīng)歷，終于將局部問題實(shí)情大白，為了使保位同仁不再經(jīng)過我之難過，此刻將自己多孔介質(zhì)經(jīng)驗(yàn)宣告以下，希望各位能加精：1。Gambit中區(qū)分網(wǎng)格以后，定義需要做為多孔介質(zhì)的地區(qū)為fluid,與缺省的fluid分別開來，再定義其名稱，我習(xí)慣將名稱定義為porous;2。在

fluent

中定義界限條件

define-boundarycondition-porous(

剛定義的名稱

)，將其設(shè)置界限條件為

fluid,

點(diǎn)擊

set

按鈕即彈出與

fluid

界限條件相同的對話框，選中

porouszone

與

laminar

復(fù)選框,再點(diǎn)擊

porouszone

標(biāo)簽即出現(xiàn)一個(gè)帶有轉(zhuǎn)動(dòng)條的界面；3。porouszone設(shè)置方法：1）定義矢量：二維定義一個(gè)矢量，第二個(gè)矢量方向不用定義，是與第一個(gè)矢量方向正交的；三維定義二個(gè)矢量，第三個(gè)矢量方向不用定義，是與第一、二個(gè)矢量方向正交的；（如何知道矢量的方向：翻開grid圖，看看X,Y,Z的方向，假如是X向，矢量為1,0,0,同理Y向?yàn)?,1,0，Z向?yàn)?,0,1,假如所需要的方向與坐標(biāo)軸正向相反，則定義矢量為負(fù)）圓錐坐標(biāo)與球坐標(biāo)請參照fluent幫助。2）定義粘性阻力1/a與內(nèi)部阻力C2：請參看自己上一篇博文“終于搞清fluent中多孔粘性阻力與內(nèi)部阻力的計(jì)算方法”，此處不贅述；3）假如了定義粘性阻力1/a與內(nèi)部阻力C2,就不用定義C1與C0，由于這是兩種不一樣的定義方法，C1與C0只在冪率模型中出現(xiàn)，該處保持默認(rèn)就行了；4）定義孔隙率porousity，默認(rèn)值1表示全開放，此值按實(shí)驗(yàn)測值填寫即可。完了，其余設(shè)置與一般k-e或RSM相同?？偨Y(jié)一下，與君共享!Tutorial7.ModelingFlowThroughPorousMediaIntroductionManyindustrialapplicationsinvolvethemodelingofflowthroughporousmedia,suchasfilters,catalystbeds,andpacking.Thistutorialillustrateshowtosetupandsolveaprobleminvolvinggasflowthroughporousmedia.Theindustrialproblemsolvedhereinvolvesgasflowthroughacatalyticconverter.Catalyticconvertersarecommonlyusedtopurifyemissionsfromgasolineanddieselenginesbyconvertingenvironmentallyhazardousexhaustemissionstoacceptablesubstances.Examplesofsuchemissionsincludecarbonmonoxide(CO),nitrogenoxides(NOx),andunburnedhydrocarbonfuels.Theseexhaustgasemissionsareforcedthroughasubstrate,whichisaceramicstructurecoatedwithametalcatalystsuchasplatinumorpalladium.Thenatureoftheexhaustgasflowisaveryimportantfactorindeterminingtheperformanceofthecatalyticconverter.Ofparticularimportanceisthepressuregradientandvelocitydistributionthroughthesubstrate.HenceCFDanalysisisusedtodesignefficientcatalyticconverters:bymodelingtheexhaustgasflow,thepressuredropandtheuniformityofflowthroughthesubstratecanbedetermined.Inthistutorial,FLUENTisusedtomodeltheflowofnitrogengasthroughacatalyticconvertergeometry,sothattheflowfieldstructuremaybeanalyzed.Thistutorialdemonstrateshowtodothefollowing:_Setupaporouszoneforthesubstratewithappropriateresistances._Calculateasolutionforgasflowthroughthecatalyticconverterusingthepressurebasedsolver._Plotpressureandvelocitydistributiononspecifiedplanesofthegeometry._Determinethepressuredropthroughthesubstrateandthedegreeofnon-uniformityofflowthroughcrosssectionsofthegeometryusingX-Yplotsandnumericalreports.ProblemDescriptionThecatalyticconvertermodeledhereisshowninFigure.Thenitrogenflowsinthroughtheinletwithauniformvelocityofm/s,passesthroughaceramicmonolithsubstratewithsquareshapedchannels,andthenexitsthroughtheoutlet.Whiletheflowintheinletandoutletsectionsisturbulent,theflowthroughthesubstrateislaminarandischaracterizedbyinertialandviscouslosscoefficientsintheflow(X)direction.Thesubstrateisimpermeableinotherdirections,whichismodeledusinglosscoefficientswhosevaluesarethreeordersofmagnitudehigherthanintheXdirection.SetupandSolutionStep1:GridReadthemeshfile(catalytic.File/Read/Case...Checkthegrid.Grid/CheckFLUENTwillperformvariouschecksonthemeshandreporttheprogressintheconsole.Makesurethattheminimumvolumereportedisapositivenumber.3.Scalethegrid.Grid!Scale...SelectmmfromtheGridWasCreatedIndrop-downlist.ClicktheChangeLengthUnitsbutton.Alldimensionswillnowbeshowninmillimeters.ClickScaleandclosetheScaleGridpanel.4.Displaythemesh.Display/Grid...(a)Makesurethatinlet,outlet,substrate-wall,andwallareselectedintheSurfacesselectionlist.ClickDisplay.RotatetheviewandzoomintogetthedisplayshowninFigure.ClosetheGridDisplaypanel.Thehexmeshonthegeometrycontainsatotalof34,580cells.Step2:Models2.Selectthestandardk-εturbulencemodel.Define/Models/Viscous...Step3:Materials1.AddnitrogentothelistoffluidmaterialsbycopyingitfromtheFluentDatabaseformaterials.Define/Materials...(a)ClicktheFluentDatabase...buttontoopentheFluentDatabaseMaterialspanel.i.Selectnitrogen(n2)fromthelistofFluentFluidMaterials.ii.ClickCopytocopytheinformationfornitrogentoyourlistoffluidmaterials.ClosetheFluentDatabaseMaterialspanel.(b)ClosetheMaterialspanel.Step4:BoundaryConditions.Define/BoundaryConditions...1.Settheboundaryconditionsforthefluid(fluid).SelectnitrogenfromtheMaterialNamedrop-downlist.ClickOKtoclosetheFluidpanel.2.Settheboundaryconditionsforthesubstrate(substrate).SelectnitrogenfromtheMaterialNamedrop-downlist.EnablethePorousZoneoptiontoactivatetheporouszonemodel.EnabletheLaminarZoneoptiontosolvetheflowintheporouszonewithoutturbulence.ClickthePorousZonetab.i.Makesurethattheprincipaldirectionvectorsaresetasshownin.Usethescrollbartoaccessthefieldsthatarenotinitiallyvisibleinthepanel.ii.EnterthevaluesinTablefortheViscousResistanceandInertialResistance.Scrolldowntoaccessthefieldsthatarenotinitiallyvisibleinthepanel.(e)ClickOKtoclosetheFluidpanel.3.Setthevelocityandturbulenceboundaryconditionsattheinlet(inlet).(a)Enterm/sfortheVelocityMagnitude.(b)SelectIntensityandHydraulicDiameterfromtheSpecificationMethoddropdownlistintheTurbulencegroupbox.Retainthedefaultvalueof10%fortheTurbulentIntensity.Enter42mmfortheHydraulicDiameter.ClickOKtoclosetheVelocityInletpanel.4.Settheboundaryconditionsattheoutlet(outlet).(a)Retainthedefaultsettingof0forGaugePressure.(b)SelectIntensityandHydraulicDiameterfromtheSpecificationMethoddropdownlistintheTurbulencegroupbox.Enter5%fortheBackflowTurbulentIntensity.Enter42mmfortheBackflowHydraulicDiameter.ClickOKtoclosethePressureOutletpanel.Retainthedefaultboundaryconditionsforthewalls(substrate-wallandwall)andclosetheBoundaryConditionspanel.Step5:Solution(a)RetainthedefaultsettingsforUnder-RelaxationFactors.(b)SelectSecondOrderUpwindfromtheMomentumdrop-downlistintheDiscretizationgroupbox.(c)ClickOKtoclosetheSolutionControlspanel.EnablePlotintheOptionsgroupbox.ClickOKtoclosetheResidualMonitorspanel.Enabletheplottingofthemassflowrateattheoutlet.Solve/Monitors/Surface...(a)SettheSurfaceMonitorsto1.(b)EnablethePlotandWriteoptionsformonitor-1,andclicktheDefine...buttontoopentheDefineSurfaceMonitorpanel.i.SelectMassFlowRatefromtheReportTypedrop-downlist.SelectoutletfromtheSurfacesselectionlist.ClickOKtoclosetheDefineSurfaceMonitorspanel.(c)ClickOKtoclosetheSurfaceMonitorspanel.4.Initializethesolutionfromtheinlet.Solve/Initialize/Initialize...SelectinletfromtheComputeFromdrop-downlist.ClickInitandclosetheSolutionInitializationpanel.5.Savethecasefile(catalytic.File/Write/Case...6.Runthecalculationbyrequesting100iterations.Solve/Iterate...Enter100fortheNumberofIterations.ClickIterate.TheFLUENTcalculationwillconvergeinapproximately70iterations.Bythispointthemassflowratemonitorhasattendedout,asseeninFigure.(c)ClosetheIteratepanel.7.Savethecaseanddatafiles(catalyticandcatalytic.File/Write/Case&Data...Note:Ifyouchooseafilenamethatalreadyexistsinthecurrentfolder,FLUENTwillpromptyouforconfirmationtooverwritethefile.Step6:Post-processingCreateasurfacepassingthroughthecenterlineforpost-processingpurposes.Surface/Iso-Surface...SelectGrid...andY-CoordinatefromtheSurfaceofConstantdrop-downlists.ClickComputetocalculatetheMinandMaxvalues.Retainthedefaultvalueof0fortheIso-Values.Entery=0fortheNewSurfaceName.ClickCreate.Createcross-sectionalsurfacesatlocationsoneithersideofthesubstrate,aswellasatitscenter.Surface/Iso-Surface...SelectGrid...andX-CoordinatefromtheSurfaceofConstantdrop-downlists.ClickComputetocalculatetheMinandMaxvalues.Enter95forIso-Values.Enterx=95fortheNewSurfaceName.ClickCreate.Inasimilarmanner,createsurfacesnamedx=130andx=165withIso-Valuesof130and165,respectively.ClosetheIso-Surfacepanelafterallthesurfacesbeencreated.

haveCreatealinesurfaceforthecenterlineoftheporousmedia.Surface/Line/Rake...(a)EnterthecoordinatesofthelineunderEndPoints,usingthestartingcoordinateof(95,0,0)andanendingcoordinateof(165,0,0),asshown.Enterporous-clfortheNewSurfaceName.ClickCreatetocreatethesurface.ClosetheLine/RakeSurfacepanel.4.Displaythetwowallzones(substrate-wallandwall).Display/Grid...DisabletheEdgesoption.EnabletheFacesoption.DeselectinletandoutletinthelistunderSurfaces,andmakesurethatonlysubstrate-wallandwallareselected.ClickDisplayandclosetheGridDisplaypanel.EnabletheLightsOnoptionintheLightingAttributesgroupbox.RetainthedefaultselectionofGourandintheLightingdrop-downlist.ClickApplyandclosetheDisplayOptionspanel.Setthetransparencyparameterforthewallzones(substrate-wallandwall).Display/Scene...Selectsubstrate-wallandwallintheNamesselectionlist.ClicktheDisplay...buttonunderGeometryAttributestoopentheDisplayPropertiespanel.i.SettheTransparencysliderto70.ii.ClickApplyandclosetheDisplayPropertiespanel.ClickApplyandthenclosetheSceneDescriptionpanel.7.Displayvelocityvectorsonthey=0surface.Display/Vectors...(a)EnabletheDrawGridoption.TheGridDisplaypanelwillopen.i.Makesurethatsubstrate-wallandwallareselectedinthelistunderSurfaces.ClickDisplayandclosetheDisplayGridpanel.(b)Enter5fortheScale.(c)SetSkipto1.(d)Selecty=0fromtheSurfacesselectionlist.(e)ClickDisplayandclosetheVectorspanel.Theflowpatternshowsthattheflowentersthecatalyticconverterasajet,withrecirculationoneithersideofthejet.Asitpassesthroughtheporoussubstrate,itdeceleratesandstraightensout,andexhibitsamoreuniformvelocitydistribution.Thisallowsthemetalcatalystpresentinthesubstratetobemoreeffective.Figure:VelocityVectorsonthey=0PlaneDisplayfilledcontoursofstaticpressureonthey=0plane.Display/Contours...EnabletheFilledoption.EnabletheDrawGridoptiontoopentheDisplayGridpanel.i.Makesurethatsubstrate-wallandwallareselectedinthelistunderSurfaces.ii.ClickDisplayandclosetheDisplayGridpanel.MakesurethatPressure...andStaticPressureareselectedfromtheContoursofdrop-downlists.Selecty=0fromtheSurfacesselectionlist.ClickDisplayandclosetheContourspanel.Figure:ContoursoftheStaticPressureonthey=0planeThepressurechangesrapidlyinthemiddlesection,wherethefluidvelocitychangesasitpassesthroughtheporoussubstrate.Thepressuredropcanbehigh,duetotheinertialandviscousresistanceoftheporousmedia.DeterminingthispressuredropisagoalofCFDanalysis.Inthenextstep,youwilllearnhowtoplotthepressuredropalongthecenterlineofthesubstrate.Plotthestaticpressureacrossthelinesurfaceporous-cl.Plot/XYPlot...(a)MakesurethatthePressure...andStaticFunctiondrop-downlists.

Pressure

areselected

fromtheYAxisSelectporous-clfromtheSurfacesselectionlist.ClickPlotandclosetheSolutionXYPlotpanel.Figure:PlotoftheStaticPressureontheporous-clLineSurfaceInFigure,thepressuredropacrosstheporoussubstratecanbeseentoberoughly300Pa.DisplayfilledcontoursofthevelocityintheXdirectiononthex=95,x=130andx=165surfaces.Display/Contours...DisabletheGlobalRangeoption.SelectVelocity...andXVelocityfromtheContoursofdrop-downlists.Selectx=130,x=165,andx=95fromtheSurfacesselectionlist,anddeselecty=0.(d)ClickDisplayandclosetheContourspanel.Thevelocityprofilebecomesmoreuniformasthefluidpassesthroughtheporousmedia.Thevelocityisveryhighatthecenter(theareainred)justbeforethenitrogenentersthesubstrateandthendecreasesasitpassesthroughandexitsthesubstrate.Theareaingreen,whichcorrespondstoamoderatevelocity,increasesinextent.Figure:ContoursoftheXVelocityonthex=95,x=130,andx=165SurfacesUsenumericalreportstodeterminetheaverage,minimum,andmaximumofthevelocitydistributionbeforeandaftertheporoussubstrate.Report/SurfaceIntegrals...SelectMass-WeightedAveragefromtheReportTypedrop-downlist.SelectVelocityandXVelocityfromtheFieldVariabledrop-downlists.Selectx=165andx=95fromtheSurfacesselectionlist.ClickCompute.(e)SelectFacetMinimumfromtheReportTypedrop-downlistandclick(f)SelectF