Fluent翼型算例——超级经典的算例

FlowoveranAirfoilRajeshBhaskaranProblemSpecificationConsiderairflowingoverthegivenairfoil.Thefreestreamvelocityis50m/sandtheangleofattackis5o.Assumestandardsea-levelvaluesforthefreestreamproperties:Pressure=101,325PaDensity=1.2250kg/m3Temperature=288.16KKinematicviscosityv=1.4607e-5m2/sDeterminetheliftanddragcoefficientsundertheseconditionsusingFLUENT.Step1:CreateGeometryinGAMBITThistutorialleadsyouthroughthestepsforgeneratingameshinGAMBITforanairfoilgeometry.ThismeshcanthenbereadintoFLUENTforfluidflowsimulation.Inanexternalflowsuchasthatoveranairfoil,wehavetodefineafarfieldboundaryandmeshtheregionbetweentheairfoilgeometryandthefarfieldboundary.Itisagoodideatoplacethefarfieldboundarywellawayfromtheairfoilsincewe'llusetheambientconditionstodefinetheboundaryconditionsatthefarfield.Thefartherwearefromtheairfoil,thelesseffectithasontheflowandsomoreaccurateisthefarfieldboundarycondition.Thefarfieldboundarywe'lluseisthelineABCDEFAinthefigureabove.cisthechordlength.StartGAMBITCreateanewdirectorycalledairfoilandstartGAMBITfromthatdirectorybytypinggambit-idairfoilatthecommandprompt.1UnderMainMenu,selectSolverFLUENT5/6sincethemeshtobecreatedistobeusedinFLUENT6.0.ImportEdgeTospecifytheairfoilgeometry,we'llimportafilecontainingalistofverticesalongthesurfaceandhaveGAMBITjointheseverticestocreatetwoedges,correspondingtotheupperandlowersurfacesoftheairfoil.We'llthensplittheseedgesinto4distinctedgestohelpuscontrolthemeshsizeatthesurface.Let'stakealookatthevertices.datfile:Thefirstlineofthefilerepresentsthenumberofpointsoneachedge(61)andthenumberofedges(2).Thefirst61setofverticesareconnectedtoformtheedgecorrespondingtotheuppersurface;thenext61areconnectedtoformtheedgeforthelowersurface.Thechordlengthcforthegeometryinvertices.datfileis1,soxvariesbetween0and1.Ifyouareusingadifferentairfoilgeometryspecificationfile,notetherangeofxvaluesinthefileanddeterminethechordlengthc.You'llneedthislateron.MainMenuFileImportICEMInput...ForFileName,browseandselectthevertices.datfile.SelectbothVerticesandEdgesunderGeometrytoCreate:sincethesearethegeometricentitiesweneedtocreate.DeselectFace.ClickAccept.SplitEdgesNext,wewillsplitthetopandbottomedgesintotwoedgeseachasshowninthefigurebelow.2Weneedtodothisbecauseanon-uniformgridspacingwillbeusedforx0.3candauniformgridspacingforx0.3c.TosplitthetopedgeintoHIandIG,selectMakesurePointisselectednexttoSplitWithintheSplitEdgewindow.SelectthetopedgeoftheairfoilbyShift-clickingonit.Youshouldseesomethingsimilartothepicturebelow:We'llusethepointatx=0.3contheuppersurfacetosplitthisedgeintoHIandIG.Todothis,enter0.3forx:underGlobal.Ifyourcisnotequaltoone,enterthevalueof0.3*cinsteadofjust0.3.Forinstance,ifc=4,enter1.2.Fromhereon,wheneveryou'reaskedtoenter(somefactor)*c,calculatetheappropriatevalueforyourcandenterit.Youshouldseethatthewhitecirclehasmovedtothecorrectlocationontheedge.ClickApply.Youwillseeamessagesaying``Edgeedge.1wassplit,andedgeedge.3created''intheTranscriptwindow.Notetheyellowmarkerinplaceofthewhitecircle,indicatingtheoriginaledgehasbeensplitintotwoedgeswiththeyellowmarkerasitsdividingpoint.RepeatthisprocedureforthelowersurfacetosplititintoHJandJG.Usethepointatx=0.3conthelowersurfacetosplitthisedge.CreateFarfieldBoundaryNextwe'llcreatethefarfieldboundarybycreatingverticesandjoiningthemappropriatelytoformedges.CreatethefollowingverticesbyenteringthecoordinatesunderGlobalandthelabelunderLabel:ClicktheFITTOWINDOWbuttontoscalethedisplaysothatyoucanseeallthevertices.Asyoucreatetheedgesforthefarfieldboundary,keepthepictureofthefarfieldnomenclaturegivenatthetopofthisstephandy.3CreatetheedgeABbyselectingthevertexAfollowedbyvertexB.EnterABforLabel.ClickApply.GAMBITwillcreatetheedge.YouwillseeamessagesayingsomethinglikeCreatededge:AB''intheTranscriptwindow.Similarly,createtheedgesBC,CD,DE,EG,GAandCG.NotethatyoumighthavetozoominontheairfoiltoselectvertexGcorrectly.Nextwe'llcreatethecirculararcAF.Right-clickontheCreateEdgebuttonandselectArc.4u,theboxnexttIntheCreateRealCircularArcmenoCenterwillbeyellow.Thatmeansthatthevertexyouselectwillbetakenasthecenterofthearc.SelectvertexGandclickApply.NowtheboxnexttoEndPointswillbehighlightedinyellow.Thismeansthatyoucannowselectthetwoverticesthatformtheendpointsofthearc.SelectvertexAandthenvertexF.EnterAFunderLabel.ClickApply.Ifyoudidthisright,thearcAFwillbecreated.Ifyoulookinthetranscriptwindow,you'llseeamessagesayingthatanedgehasbeencreated.Similarly,createanedgecorrespondingtoarcEF.CreateFacesTheedgescanbejoinedtogethertoformfaces(whichareplanarsurfacesin2D).We'llcreatethreefaces:ABCGA,EDCGEandGAFEG+airfoilsurface.Thenwe'llmesheachface.ThisbringsuptheCreateFaceFromWireframemenu.Recallthatwehadselectedverticesinordertocreateedges.Similarly,wewillselectedgesinordertoformaface.TocreatethefaceABCGA,selecttheedgesAB,BC,CG,andGAandclickApply.GAMBITwilltellyouthatithasCreatedface:face.1''inthetranscriptwindow.Similarly,createthefaceEDCGE.TocreatethefaceconsistingofGAFEG+airfoilsurface,selecttheedgesinthefollowingorder:AG,AF,EF,EG,andJG,HJ,HIandIG(aroundtheairfoilin