fluent 学习资料 Laminar Pipe Flow.docx

fluent 学习资料 Laminar Pipe Flow.docx

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fluent学习资料LaminarPipeFlow

ProblemSpecification

1.CreateGeometryinGAMBIT

2.MeshGeometryinGAMBIT

3.SpecifyBoundaryTypesinGAMBIT

4.SetUpProbleminFLUENT

5.Solve!

6.AnalyzeResults

7.RefineMesh

Problem1

Problem2

LaminarPipeFlow

ProblemSpecification

Considerfluidflowingthroughacircularpipeofcontantcross-section.ThepipediameterD=0.2mandlengthL=8m.TheinletvelocityVin=1m/s.Considerthevelocitytobeconstantovertheinletcross-section.Thefluidexhaustsintotheambientatmospherewhichisatapressureof1atm.Takedensityρ=1kg/m3andcoefficientofviscosityµ=2x10-3kg/（ms）.TheReynoldsnumberRebasedonthepipediameteris

whereVavgistheaveragevelocityattheinlet,whichis1m/sinthiscase.

SolvethisproblemusingFLUENT.Plotthecenterlinevelocity,wallskin-frictioncoefficient,andvelocityprofileattheoutlet.Validateyourresults.

Note:

Thevaluesusedfortheinletvelocityandflowpropertiesarechosenforconvenienceratherthantoreflectreality.ThekeyparametervaluetofocusonistheReynoldsno.

PreliminaryAnalysis

Weexpecttheviscousboundarylayertogrowalongthepipestartingattheinlet.Itwilleventuallygrowtofillthepipecompletely（providedthatthepipeislongenough）.Whenthishappens,theflowbecomesfully-developedandthereisnovariationofthevelocityprofileintheaxialdirection,x（seefigurebelow）.Onecanobtainaclosed-formsolutiontothegoverningequationsinthefully-developedregion.YoushouldhaveseenthisintheIntroductiontoFluidMechanicscourse.Wewillcomparethenumericalresultsinthefully-developedregionwiththecorrespondinganalyticalresults.Soit'sagoodideaforyoutogobacktoyourtextbookintheIntrocourseandreviewthefully-developedflowanalysis.Whatarethevaluesofcenterlinevelocityandfrictionfactoryouexpectinthefully-developedregionbasedontheanalyticalsolution?

Whatisthesolutionforthevelocityprofile?

We'llcreatethegeometryandmeshinGAMBITwhichisthepreprocessorforFLUENT,andthenreadthemeshintoFLUENTandsolvefortheflowsolution.

GotoStep1:

CreateGeometryinGAMBIT

Step1:

CreateGeometryinGAMBIT

StrategyforCreatingGeometry

Inordertocreatetherectangle,wewillfirstcreatetheverticesatthefourcorners.We'llthenjoinadjacentverticesbystraightlinestoformthe"edges"oftherectangle.Lastly,we'llcreatea"face"correspondingtotheareaenclosedbytheedges.InStep2,we'llmeshthefacei.e.therectangle.Notethatin3Dproblems,you'llhavetoforma"volume"fromfaces.SothehierarchyofgeometricobjectsinGAMBITisvertices->edges->faces->volumes.

CreateaWorkingDirectory

Createafoldercalledpipeinaconvenientlocation.We'llusethisastheworkingfolderinwhichfilescreatedduringthesessionwillbestored.

NoteforACCELcomputerlabusers:

Eachusergetshis/herown100MBofdiskspaceunderS:

atACCEL.YoucanputyourfilesinS:

andit'llbeaccessiblefromanycomputer.Thisiswhereyoushouldputfilesthatyouwanttokeepandaccesslateron.

StartGAMBIT

Startyourcommandprompt.

Start>Run

InWindowsNT/2000/XP:

Typecmdandpressenter.

InWindows95/98/ME:

Typecommandandpressenter.

Navigateyourwaytoyourworkingfolder.Forexample,ifyoucreatedafoldernamedfluentondriveS:

inWindows,typecdS:

\fluentatthecommandpromptandpressEnter.

StartGAMBITbytypinggambit-idpipeatthecommandpromptandpressingEnter.

Ifthisdoesn'twork,trytypingthefullpathnametotheGAMBITexecutable:

c:

\fluent.inc\ntbin\ntx86\gambit-idpipe

ThisbringsuptheGAMBITinterfaceandtellsGAMBITtousepipeasthedefaultprefixforallfilescreatedduringthesession.InWindows,theExceedX-serverstartsupbeforetheGAMBITinterfacecomesup.Exceedisathird-partyapplicationneededtorendertheinterfaceinWindows（GAMBITwasoriginallydevelopedunderUnix）.Tomakebestuseofscreenrealestate,movethewindowsandresizethemsothatyouapproximatethisscreenarrangement.ThiswayyoucanreadinstructionsinthebrowserwindowandimplementtheminGAMBIT.

Youcanresizethetextinthebrowserwindowtoyourtasteandcomfort:

InInternetExplorer:

Menubar>View>TextSize,thenchoosetheappropriatefontsize.

InNetscape:

Menubar>View>IncreaseFontorMenubar>View>DecreaseFont.

TheGAMBITInterfaceconsistsofthefollowing:

∙MainMenuBar:

NotethatthejobnamepipeappearsafterID:

inthetitlebaroftheUtilityMenu.

∙OperationToolpad:

We'llmoreorlessworkourwayacrosstheOperationToolpadaswegothroughthesolutionsteps.Noticethataseachofthetopbuttonsisselected,adifferent"sub-pad"appears.TheGeometrysub-padisshownintheabovesnaphot.

∙GlobalControlToolpad:

TheGlobalControlToolpadhasoptionssuchasFittoScreen

andUndo

thatareveryhandyduringthecourseofgeometryandmeshcreation.

∙GAMBITGraphics:

Thisisthewindowwherethegraphicalresultsofoperationsaredisplayed.

∙GAMBITDescriptionPanel:

TheDescriptionPanelcontainsdescriptionsofbuttonsorobjectsthatthemouseispointingto.MoveyourmouseoversomebuttonsandnoticethecorrespondingtextintheDescriptionPanel.

∙GAMBITTranscriptWindow:

ThisisthewindowtowhichoutputfromGAMBITcommandsiswrittenandwhichprovidesfeedbackontheactionstakenbyGAMBITasyouperformoperations.If,atsomepoint,youarenotsureyouclickedtherightbuttonorenteredavaluecorrectly,thisiswheretolooktofigureoutwhatyoujustdid.YoucanclickonthearrowbuttonintheupperrighthandcornertomaketheTranscriptwindowfull-sized.Youcanclickonthearrowagaintoreturnthewindowtoitsoriginalsize.Goahead,givethisatry.

SelectSolver

SpecifythatthemeshtobecreatedisforusewithFLUENT6.0:

MainMenu>Solver>FLUENT5/6

VerifythishasbeendonebylookingintheTranscriptWindowwhereyoushouldsee:

Theboundarytypesthatyou'llbeabletoselectinthethirdstepdependsonthesolverselected.

Wecanassumethattheflowisaxisymmetric.Theproblemdomainis:

whererandxaretheradialandaxialcoordinates,respectively.

Strategyforcreatinggeometry

Wewillputtheoriginofthecoordinatesystematthelowerleftcorneroftherectangle.Thecoordinatesofthecornersareshowninthefigurebelow:

Wewillfirstcreatefourverticesatthefourcornersandjoinadjacentverticestogettheedgesoftherectangle.Wewillthenformafacethatcoverstheareaoftherectangle.

CreateVertices

FindthebuttonsdescribedbelowbypointingthemouseateachofthebuttonsandreadingtheDescriptionWindow.

OperationToolpad>GeometryCommandButton

>VertexCommandButton

>CreateVertex

NoticethattheCreateVertexbuttonhasalreadybeenselectedbydefault.Afteryouselectabuttonunderasub-pad,itbecomesthedefaultwhenyougotoadifferentsub-padandthencomebacktothesub-pad.

Createthevertexatthelower-leftcorneroftherectangle:

Nexttox:

entervalue0.Nexttoy:

entervalue0.Nexttoz:

entervalue0（thesevaluesshouldbedefaults）.ClickApply.Thiscreatesthevertex（0,0,0）whichisdisplayedinthegraphicswindow.

IntheTranscriptwindow,GAMBITreportsthatit"Createdvertex:

vertex.1".Theverticesarenumberedvertex.1,vertex.2etc.intheorderinwhichtheyarecreated.

Repeatthisprocesstocreatethreemorevertices:

Vertex2:

（0,0.1,0）

Vertex3:

（8,0.1,0）

Vertex4:

（8,0,0）

Notethatfora2Dproblem,thez-coordinatecanalwaysbelefttothedefaultvalueof0.

OperationToolpad>GlobalControl>FittoWindowButton

ThisfitsthefourverticesoftherectanglewehavecreatedtothesizeoftheGraphicsWindow.

（Clickpictureforlargerimage）

CreateEdges

We'llnowconnectappropriatepairsofverticestoformedges.ToselectanyentityinGAMBIT,holddowntheShiftkeyandclickontheentity.

OperationToolpad>GeometryCommandButton

>EdgeCommandButton

>CreateEdge

SelecttwoverticesthatmakeupanedgeofthisrectanglebyholdingdowntheShiftbuttonandclickingonthecorrespondingvertices.Aseachvertexispicked,itwillappearredintheGraphicsWindow.ThenletgooftheShiftbutton.Wecanchecktheselectedverticesbyclickingontheup-arrownexttoVertices:

.

Thiswillbringupawindowcontainingtheverticesthathavebeenselected.VerticescanbemovedfromtheAvailableandPickedlistsbyselectingthemandthenpressingtheleftorrightarrowbuttons.

Afterthecorrectverticeshavebeenselected,clickClose,thenclickApplyintheCreateStraightEdgewindow.

Repeatthisprocesstocreatearectangle.

（Clickpictureforlargerimage）

CreateFace

OperationToolpad>GeometryCommandButton

>FaceCommandButton

>FormFace

Toformafaceoutoftheareaenclosedbythefourlines,weneedtoselectthefourledgesthatenclosethisarea.ThiscanbedonebyholdingdowntheShiftkey,clickingoneachline（noticethatthecurrentlyselectedlineappearsred）,andthenreleasingtheShiftkeyafterallfourlineshavebeenselected.

Alternatively,aneasierwaytodothiswouldbetoclickontheuparrownexttoedges:

ThiswillbringuptheEdgeListwindow.ClickonAll->toselectalloftheedgesatonce.ClickClose.

ClickApplytocreatetheface.

GotoStep2:

MeshGeometryinGAMBIT

Step2:

MeshGeometryinGAMBIT

We'llnowcreateameshontherectangularfacewith100divisionsintheaxialdirectionand5divisionsintheradialdirection.We'llfirstmeshthefouredgesandthentheface.Thedesiredgridspa