fluent中多孔介質(zhì)設(shè)置問(wèn)題和算例

經(jīng)過(guò)痛苦的一段經(jīng)歷,終于將局部問(wèn)題真相年夜白，為了使保位同仁不再經(jīng)過(guò)我之痛苦，現(xiàn)在將自己多孔介質(zhì)經(jīng)驗(yàn)公布如下，希望各位能加精：之勘阻及廣創(chuàng)作時(shí)間：二O二一年七月二十九日Gambit中劃分網(wǎng)格之后，界說(shuō)需要做為多孔介質(zhì)的區(qū)域?yàn)閒luid,與缺省的fluid分別開(kāi)來(lái)，再界說(shuō)其名稱,我習(xí)慣將名稱界說(shuō)為porous;在fluent中界說(shuō)鴻溝條件define-boundarycondition-porous（剛界說(shuō)的名稱），將其設(shè)置鴻溝條件為fluid,點(diǎn)擊set按鈕即彈出與fluid鴻溝條件一樣的對(duì)話框，選中porouszone與laminar復(fù)選框，再點(diǎn)擊porouszone標(biāo)簽即呈現(xiàn)一個(gè)帶有滾動(dòng)條的界面；porouszone設(shè)置方法：1）界說(shuō)矢量：二維界說(shuō)一個(gè)矢量，第二個(gè)矢量方向不肯界說(shuō)，是與第一個(gè)矢量方向正交的；三維界說(shuō)二個(gè)矢量，第三個(gè)矢量方向不肯界說(shuō)，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(kāi)grid圖,看看X,Y,Z的方向，如果是X向,矢量為1,0,0,同理Y向?yàn)?,1,0,Z向?yàn)?,0,1,如果所需要的方向與坐標(biāo)軸正向相反，則界說(shuō)矢量為負(fù)）圓錐坐標(biāo)與球坐標(biāo)請(qǐng)參考fluent幫手.2） 界說(shuō)粘性阻力1/a與內(nèi)部阻力C2：請(qǐng)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） 如果了界說(shuō)粘性阻力1/a與內(nèi)部阻力C2,就不肯界說(shuō)C1與C0,因?yàn)檫@是兩種分歧的界說(shuō)方法,C1與C0只在幕率模型中呈現(xiàn)，該處堅(jiān)持默認(rèn)就行了；4） 界說(shuō)孔隙率porousity,默認(rèn)值1暗示全開(kāi)放，此值按實(shí)驗(yàn)測(cè)值填寫即可.完了，其他設(shè)置與普通k-e或RSM相同.總結(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.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