Fluent_tutorial

FluenttutorialsGabrielW»ecel30thMarch2009Contents0.1Airheater...............................20.1.1Buildinggeometry......................30.1.2Settingboundaryconditiontypes..............70.1.3SettingFluentparameters..................80.1.4Performingcalculations...................90.1.5Finalremarks.........................100.2Cyclone.................................110.2.1Buildinggeometry......................110.2.2Settingboundaryconditiontypes..............150.2.3Meshinggeometry......................160.2.4SettingFluentparameters..................170.2.5Performingcalculations...................1910.1AirheaterThisexampleshowshowtosimplify3Dgeometryoftherealobjectandperformcalculationin2Dspace.AirheatergeometryisgiveninFigure1.Theairstream°owsfromlefttotheright.Thereareonlytwoopeningintheheater,inlet(left)andoutlet(right).Theothersides(front,back,top,bottom)areinsulatedwalls.Insidetheheater3cylindricalpipesarepositionedperpendiculartothe°ow.DataoftheoperationoftheheateraregiveninTable1.The°owpaterninsuchcon¯gurationoftheheaterinanycrosssection(alignedwith°owdirection)isalmostthesame.Thewidthoftheheaterishighenoughtoneglectin°uenceofthesidewalls(frontandback)onthe°owinthemiddlepartoftheheater.Hencewecansimulate°owintheheaterwithgoodaccuracyassuming2Dgeometry(seetheheatercrosssectionintheFigure2,wedonotutilizesymmetryofthecrosssectiongeometrysincewewantlatertoanalyzedi®erentcylinderalignments).Evenforsimpli¯edgeometry°owovercylindersemergetobecomplex,withstagnationzonesandrevers°owclosetothecylin-ders.Thatfeaturerequirepropertreatmentofthemesh.Firstofallitneedstobesymmetricasthe°owissymmetric.Thebestistotrygeneratefullystructuredmeshandifpossiblewithcellsedgesalignedwiththedirectionofthe°ow.Thisisnotpossibleinallareaofthe°ow,butatleastatthecylinderboundariescellsalignmentshouldfollow°owdirection.heatersinletoutflowFigure1:Airheater.air°ow5m=sairinlettemperature300Kthermalinputateachheater1.6kWwallsthermalcondition0kW(isolation)Table1:Airheatersetupparameter21m0.04m0.1m0.1m0.2moutflowinletinsulatedwallsheaters0.2mFigure2:Airheatercrosssection-dimensions.0.1.1BuildinggeometryAsalreadymentionedwerequirestructuredmeshmadeofQuadtypeelements.InordertouseQuadelementsweneedearliertoplanhowtodividegeometryintopologicalfaceswhichlaterareeasytomesh.Figure3showspropositionoftopologicaldivisionoftheairheatergeometry.Onecanrecognizethatallfacesposses4edgeswhatallowstomeshthemeasilywithQuadelements.Figure3:Airheatertopologicaldivisionofthegeometry.Seebelowlistingofthegeometrycreationprocedure.Geometry!Edge!CreateEdge!ArcSelectmethod:Radius,StartAngle,EndAngleEnterRadius=0.02,StartAngle=-45,EndAngle=45PressApplyEnterRadius=0.02,StartAngle=45,EndAngle=135PressApplyEnterRadius=0.02,StartAngle=135,EndAngle=225PressApply3EnterRadius=0.02,StartAngle=225,EndAngle=315PressApplyGeometry!Vertex!CreateVertexEnterX=0.05,Y=-0.05,Z=0PressApplyEnterX=0.05,Y=0.05,Z=0PressApplyEnterX=-0.05,Y=0.05,Z=0PressApplyEnterX=-0.05,Y=-0.05,Z=0PressApplycreateedgesaroundtubeGeometry!Edge!CreateEdge!StraightSelectwithmouse(holdingShiftbutton)createdVertices(only2atthesametime)PressApplyRepeatoperation(8times)inordertogete®ectshowninFigure4.Figure4:Edgesaroundthetube.createfacesaroundtubeGeometry!Face!FormFace!WireframeSelectwithmouse(holdingShiftbutton)createdEdges(only4atthesametime)PressApplyRepeatoperation(4times)inordertogete®ectshowninFigure5.4Face1Face3Face4Face2Figure5:Facesaroundthetube.meshfacesaroundtube,¯rstsetdistributionofthenodesontheedgesMesh!Edge!MeshEdgesSelectwithmouse(holdingShiftbutton)edgescreatingtubeDeselectGradingSelectSpacingandenterIntervalsize=0.001SelectOptionMeshPressApplysetdistributionofthenodesontheedgesradiallyconnectedwithtubeSelectwithmouse(holdingShiftbutton)radialedgesSelectGradingSelectTypeFirstLengthandenterLength=0.001SelectSpacingandenterIntervalcount=20SelectOptionMeshPressApplymeshfacesaroundtubeMesh!Face!MeshFacesSelectwithmouse(holdingShiftbutton)all4facesSelectSchemeSelectElements!QuadSelectType!MapPressApplyThemeshgeneratedshouldhavesimilarformofthatshowninFigure6,howevernumberofelementsisdi®erent.make2copiesofmesharoundthetubesGeometry!Face!Move/Copy/AlignSelectwithmouseallfacesSelectCopyandenter2(thisisnumberofcopies)SelectOperation!TranslateEnterX=0.1,Y=0,Z=05Figure6:Mesharoundthetube.PressApplyThee®ectofoperationisshowninFigure7,(numberofelementsisdi®erent).Figure7:Copiedmesharoundthetubes.CopingofthefacesinthewaypresentedaboveresultindoubleEdgeslyingatthesamepositionbetweencopiedmeshes.IfwedidnotsetthemasinterfacesFluentwilltreatthemaswalls(no°owbetweenthesepartofmesh).Simplesolutiontothisproblemisconnectingthisedges.Geometry!Edge!ConnectEdgesSelectwithmousealldoublefaces(lyingatthesameposition)SelectRealPressApplyAstheresultthedoubleedgeswillbeconnectedandoneofthembedeleted.Remainingpartofthemeshisgeneratedbysimplycreatingrectangularfaces.SinceprocedureisverysimpleonlypictureshowingconsequentstepsisgiveninFigure8.6Figure8:Stepsofcreatingairheatergeometry.0.1.2SettingboundaryconditiontypesThelaststepin