fluent中多孔介质设置问题和算例

经过痛苦的一段经历,终于将局部问题真相年夜白，为了使保位同仁不再经过我之痛苦，现在将自己多孔介质经验公布如下，希望各位能加精：之勘阻及广创作时间：二O二一年七月二十九日Gambit中划分网格之后，界说需要做为多孔介质的区域为fluid,与缺省的fluid分别开来，再界说其名称,我习惯将名称界说为porous;在fluent中界说鸿沟条件define-boundarycondition-porous（刚界说的名称），将其设置鸿沟条件为fluid,点击set按钮即弹出与fluid鸿沟条件一样的对话框，选中porouszone与laminar复选框，再点击porouszone标签即呈现一个带有滚动条的界面；porouszone设置方法：1）界说矢量：二维界说一个矢量，第二个矢量方向不肯界说，是与第一个矢量方向正交的；三维界说二个矢量，第三个矢量方向不肯界说，是与第一、二个矢量方向正交的；（如何知道矢量的方向：翻开grid图,看看X,Y,Z的方向，如果是X向,矢量为1,0,0,同理Y向为0,1,0,Z向为0,0,1,如果所需要的方向与坐标轴正向相反，则界说矢量为负）圆锥坐标与球坐标请参考fluent帮手.2） 界说粘性阻力1/a与内部阻力C2：请参看自己上一篇博文“终于搞清fluent中多孔粘性阻力与内部阻力的计算方法”，此处不赘述；3） 如果了界说粘性阻力1/a与内部阻力C2,就不肯界说C1与C0,因为这是两种分歧的界说方法,C1与C0只在幕率模型中呈现，该处坚持默认就行了；4） 界说孔隙率porousity,默认值1暗示全开放，此值按实验测值填写即可.完了，其他设置与普通k-e或RSM相同.总结一下，与君共享！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.ProblemDescriptionThecatalyticconvertermodeledhereisshowninFigure7.1.Thenitrogenflowsinthroughtheinletwithauniformvelocityof22.6m/s,passesthroughaceramicmonolithsubstratewithsquareshapedchannels,andthenexitsthroughtheoutlet.Whiletheflowintheinletandoutletsectionsisturbulent,theflowthroughthesubstrateislaminarandischaracterizedbyinertialandviscouslosscoefficientsintheflow(X)direction.Thesubstrateisimpermeableinotherdirections,whichismodeledusinglosscoefficientswhosevaluesarethreeordersofmagnitudehigherthanintheXdirection.SetupandSolutionStep1:GridReadthemeshfile(catalyticconverter.msh).File/Read/Case...Checkthegrid.Grid/CheckFLUENTwillperformvariouschecksonthemeshandreporttheprogressintheconsole.Makesurethattheminimumvolumereportedisapositivenumber.Scalethegrid.Grid!Scale...Grid!Scale...SelectmmfromtheGridWasCreatedIndrop-downlist.ClicktheChangeLengthUnitsbutton.Alldimensionswillnowbeshowninmillimeters.ClickScaleandclosetheScaleGridpanel.Displaythemesh.Display/Grid...Makesurethatinlet,outlet,substrate-wall,andwallareselectedintheSurfacesselectionlist.ClickDisplay.RotatetheviewandzoomintogetthedisplayshowninFigure7.2.ClosetheGridDisplaypanel.Thehexmeshonthegeometrycontainsatotalof34,580cells.Step2:ModelsRetainthedefaultsolversettings.Define/Models/Solver...Step3:Materials1.AddnitrogentothelistoffluidmaterialsbycopyingitfromtheFluentDatabaseformaterials.Define/Materials...ClicktheFluentDatabase...buttontoopentheFluentDatabaseMaterialspanel.Selectnitrogen(n2)fromthelistofFluentFluidMaterials.ClickCopytocopytheinformationfornitrogentoyourlistoffluidmaterials.ClosetheFluentDatabaseMaterialspanel.ClosetheMaterialspanel.Step4:BoundaryConditions.Define/BoundaryConditions...1.Settheboundaryconditionsforthefluid(fluid).SelectnitrogenfromtheMaterialNamedrop-downlist.ClickOKtoclosetheFluidpanel.Settheboundaryconditionsforthesubstrate(substrate).SelectnitrogenfromtheMaterialNamedrop-downlist.EnablethePorousZoneoptiontoactivatetheporouszonemodel.EnabletheLaminarZoneoptiontosolvetheflowintheporouszonewithoutturbulence.ClickthePorousZonetab.MakesurethattheprincipaldirectionvectorsaresetasshowninTable7.1.Usethescrollbartoaccessthefieldsthatarenotinitiallyvisibleinthepanel.EnterthevaluesinTable7.2fortheViscousResistanceandInertialResistance.Scrolldowntoaccessthefieldsthatarenotinitiallyvisibleinthepanel.ClickOKtoclosetheFluidpanel.Setthevelocityandturbulenceboundaryconditionsattheinlet(inlet).Enter22.6m/sfortheVelocityMagnitude.SelectIntensityandHydraulicDiameterfromtheSpecificationMethoddropdownlistintheTurbulencegroupbox.Retainthedefaultvalueof10%fortheTurbulentIntensity.Enter42mmfortheHydraulicDiameter.ClickOKtoclosetheVelocityInletpanel.Settheboundaryconditionsattheoutlet(outlet).Retainthedefaultsettingof0forGaugePressure.SelectIntensityandHydraulicDiameterfromtheSpecificationMethoddropdownlistintheTurbulencegroupbox.Enter5%fortheBackflowTurbulentIntensity.Enter42mmfortheBackflowHydraulicDiameter.ClickOKtoclosethePressureOutletpanel.Retainthedefaultboundaryconditionsforthewalls(substrate-wallandwall)andclosetheBoundaryConditionspanel.Step5:Solution1.Setthesolutionparameters.Solve/Controls/Solution...RetainthedefaultsettingsforUnder-RelaxationFactors.SelectSecondOrderUpwindfromtheMomentumdropdownlistintheDiscretizationgroupbox.ClickOKtoclosetheSolutionControlspanel.EnablePlotintheOptionsgroupbox.ClickOKtoclosetheResidualMonitorspanel.Enabletheplottingofthemassflowrateattheoutlet.Solve/Monitors/Surface...SettheSurfaceMonitorsto1.EnablethePlotandWriteoptionsformonitor-1,andclicktheDefine...buttontoopentheDefineSurfaceMonitorpanel.SelectMassFlowRatefromtheReportTypedrop-downlist.SelectoutletfromtheSurfacesselectionlist.ClickOKtoclosetheDefineSurfaceMonitorspanel.ClickOKtoclosetheSurfaceMonitorspanel.Initializethesolutionfromtheinlet.Solve/Initialize/Initialize...SelectinletfromtheComputeFromdrop-downlist.ClickInitandclosetheSolutionInitializationpanel.Savethecasefile(catalyticconverter.cas).File/Write/Case...Runthecalculationbyrequesting100iterations.Solve/Iterate...Enter100fortheNumberofIterations.ClickIterate.TheFLUENTcalculationwillconvergeinapproximately70iterations.Bythispointthemassflowratemonitorhasattendedout,asseeninFigure7.3.ClosetheIteratepanel.Savethecaseanddatafiles(catalyticconverter.casandcatalyticconverter.dat).File/Write/Case&Data...Note:Ifyouchooseafilenamethatalreadyexistsinthecurrentfolder,FLUENTwillpromptyouforconfirmationtooverwritethefile.Step6:Post-processing1.Createasurfacepassingthroughthecenterlineforpost-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-Surfacepanelafterallthesurfaceshavebeencreated.Createalinesurfaceforthecenterlineoftheporousmedia.Surface/Line/Rake...EnterthecoordinatesofthelineunderEndPoints,usingthestartingcoordinateof(95,0,0)andanendingcoordinateof(165,0,0),asshown.Enterporous-clfortheNewSurfaceName.ClickCreatetocreatethesurface.ClosetheLine/RakeSurfacepanel.Displaythetwowallzones(substrate-wallandwall).Display/Grid...DisabletheEdgesoption.EnabletheFacesoption.DeselectinletandoutletinthelistunderSurfaces,andmakesurethatonlysubstrate-wallandwallareselected.ClickDisplayandclosetheGridDisplaypanel.RotatetheviewandzoomsothatthedisplayissimilartoFigure7.2.Setthelightingforthedisplay.Display/Options...EnabletheLightsOnoptionintheLightingAttributesgroupbox.RetainthedefaultselectionofGourandintheLightingdrop-downlist.ClickApplyandclosetheDisplayOptionspanel.Setthetransparencyparameterforthewallzones(substrate-wallandwall).Display/Scene...Selectsubstrate-wallandwallintheNamesselectionlist.ClicktheDisplay...buttonunderGeometryAttributestoopentheDisplayPropertiespanel.SettheTransparencysliderto70.ClickApplyandclosetheDisplayPropertiespanel.ClickApplyandthenclosetheSceneDescriptionpanel.Displayvelocityvectorsonthey=0surface.Display/Vectors...EnabletheDrawGridoption.TheGridDisplaypanelwillopen.Makesurethatsubstrate-wallandwallareselectedinthelistunderSurfaces.ClickDisplayandclosetheDisplayGridpanel.Enter5fortheScale.SetSkipto1.Selecty=0fromtheSurfacesselectionlist.ClickDisplayandclosetheVectorspanel.Theflowpatternshowsthattheflowentersthecatalyticconverterasajet,withrecirculationoneithersideofthejet.Asitpassesthroughtheporoussubstrate,itdeceleratesandstraightensout,andexhibitsamoreuniformvelocitydistribution.Thisallowsthemetalcatalystpresentinthesubstratetobemoreeffective.Figure7.4:VelocityVectorsonthey=0PlaneDisplayfilledcontoursofstaticpressureonthey=0plane.Display/Contours...EnabletheFilledoption.EnabletheDrawGridoptiontoopentheDisplayGridpanel.Makesurethatsubstrate-wallandwallareselectedinthelistunderSurfaces.ClickDisplayandclosetheDisplayGridpanel.MakesurethatPressure...andStaticPressureareselectedfromtheContoursofdrop-downlists.Selecty=0fromtheSurfacesselectionlist.ClickDisplayandclosetheContourspanel.Figure7.5:ContoursoftheStaticPressureonthey=0planeThepressurechangesrapidlyinthemiddlesection,wherethefluidvelocitychangesasitpassesthroughtheporoussubstrate.Thepressuredropcanbehigh,duetotheinertialandviscousresistanceoftheporousmedia.DeterminingthispressuredropisagoalofCFDanalysis.Inthenextstep,youwilllearnhowtoplotthepressuredropalongthecenterlineofthesubstrate.Plotthestaticpressureacrossthelinesurfaceporous-cl.Plot/XYPlot...MakesurethatthePressure...andStaticPressureareselectedfromtheYAxisFunctiondrop-downlists.Selectporous-clfromtheSurfacesselectionlist.ClickPlotandclosetheSolutionXYPlotpanel.Figure7.6:PlotoftheStaticPressureontheporous-clLineSurfaceInFigure7.6,thepressuredropacrosstheporoussubstratecanbeseentoberoughly300Pa.DisplayfilledcontoursofthevelocityintheXdirectiononthex=95,x=130andx=165surfaces.Display/Contours...DisabletheGlobalRangeoption.SelectVelocity...andXVelocityfromtheContoursofdrop-downlists.Selectx=130,x=165,andx=95fromtheSurfacesselectionlist,anddeselecty=0.ClickDisplayandclosetheContourspanel.Thevelocityprofilebecomesmoreuniformasthefluidpassesthroughtheporousmedia.Thevelocityisveryhighatthecenter(theareainred)justbeforethenitrogenentersthesubstrateandthendecreasesasitpassesthroughandexitsthesubstrate.Theareaingreen,whichcorrespondstoamoderatevelocity,increasesinextent.Figure7.7:ContoursoftheXVelocityonthex=95,x=130,andx=165SurfacesUsenumericalreportstodeterminetheaverage,minimum,andmaximumofthevelocitydistributionbeforeandaftertheporoussubstrate.Report/SurfaceIntegrals...SelectMass-WeightedAveragefromtheReportTypedrop-downlist.SelectVelocityandXVelocityfromtheFieldVariabledrop-downlists.Selectx=165andx=95fromtheSurfacesselectionlist.ClickCompute.SelectFacetMinimumfromtheReportTypedrop-downlistandclickComputeagain.SelectFacet