3D4 CFD Mesh文档格式.docx

3D4 CFD Mesh文档格式.docx

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Specify/identifyboundaryregionsforCFDsimulations

ExportameshwithboundaryregionsforFLUENT

ImportthemodelintoFLUENT

Exercise

Step1:

Opentheexercisefile.

1.

Fromthetoolbar,clickopen.hm（

）.

2.

Selectthemanifold_surf_mesh.hmfilefromthetutorialdirectory.

3.

ClickOpentoloadthis.hmfilecontainingthesurfacemesh.

Step2:

LoadtheCFDuserprofile.

FromthetopMenuBar,selectPreferences,thenUserProfiles….

SelecttheradiobuttonCFD.

ClickOK.

4.

Inspectthesurfaceelementsthatwillbeusedtogeneratethevolumemesh.

Theboundarymeshcanhaveanycombinationoftria/quadelements.Youwillgenerateboundarylayersonallthesurfaceelementscontainedincollector,wall.

Step3:

Checkthatalltheelementsincollectorswall,inlet,andoutletsdefineaclosedvolume.

FromtheToolpage,clickedges,thenselectcollectorswall,inletandoutlets.

Clickfindedges.

Amessageindicatingthatnoedgeswerefoundwillappearonthestatusbar.

TogglethefreeedgestoT-connections.

Thestatusbarwilldisplay:

"

NoT-connectededgeswerefound."

Step4:

CreatetheCFDMesh.

FromtheMeshmenu,clickCreate,thentetrameshtoopentheTetrameshpanel.

ClicktheCFDmeshsub-panel.

LeavethedefaultsmoothBLoptionunchanged.

Thisoptionisstronglyrecommendedformostcasesbecauseitproducesboundarylayerswithmoreuniformthicknessandbetterelementquality.

Selecttheoptionstospecifytheboundarylayerandtetrahedralcore:

numberoflayers=5

firstlayerthickness=0.5

growthrate=1.1（Thisnon-dimensionalfactorcontrolsthechangeinlayerthicknessfromonelayertothenext）.

simpletransition:

ratio=0.8（Thisisanon-dimensionalscalingfactorthatcontrolstherelativeheightofthepyramidsgeneratedontopofthelastquadfaceofallhexahedralBLelements）.

Thelasttwooptionscontrolthetetrahedralcoremesh.Optimizemeshqualityisthetetrahedralmeshgenerationalgorithm,andthegrowthratespecifiedisinterpolate（thisinterpolatesthetetrahedralelementsizefromthesizeonthesurfacemesh（boundaryofthetetrahedralcorevolume））.

ThedefaultsimpletransitionusesonepyramidelementtotransitionfromaBLhexahedral’squadfacetothetetrahedralcoremesh.Theratioistherelativethicknessofthetransitionlayerascomparedwiththeaveragesizeoftheelements.Thelargerthisratiothethickeristhetransitionlayer.Ingeneralavalueintherange0.3-0.8workswell.

5.

Selectthetypeoftetrameshingalgorithm.

Therearefouroptionsavailable;

thefirstthreeoptionsaredescribedinthetetrameshpaneldocumentation.

tetrameshnormally

optimizemeshspeed

optimizemeshquality

boundarylayeronly

Thelastoptionboundarylayeronly,isavailabletogeneratetheboundarylayeraloneandstopbeforegeneratingthetetrahedralcore.Thisoptionmodifiesadjacentsurfacemeshestoreflectchangesintroducedbytheboundarylayerthickness,andcreatesacollectornamed^CFD_trias_for_tetramesh,thatisusedtogeneratetheinnercoretetrahedralmeshusingthe“tetramesh”sub-panel.

CollectorsCFD_boundary_layerandCFD_tetramesh_coreareautomaticallycreatediftheydonotexist.However,ifthesecollectorsexisttheyshouldbeemptycollectors.Formostcasesitisbesttoselecttheoptimizemeshqualityoption.

6.

Selectthetetrahedralcoregrowthrate,interpolate.

Thisavoidstheproblemofgeneratingtetrahedralelementsthataretoolargeatthecenterofthecoremesh.

7.

Selectalltheelements/componentsthatdefinethesurfaceareaonwhichyouneedtogenerateboundarylayers.Thisselectionisdoneinthefloat/fixedwithboundarylayerselector.

8.

Clickcompsandselectcollector,wall.

9.

Selectalltheelements/componentsthatdefinethesurfaceareaonwhichyouwanttogenerateboundarylayers.Thisselectionisdonewiththefloatw/oboundarylayerselector.

10.

Clickcomps.

11.

Selectcollectors:

inletandoutlets.

12.

Verifythattheswitchbelowthefloatw/oboundarylayerselectorissettoremesh.

Thismeansthatthemeshesinthezonesdefinedbycollectorsinletandoutletswillberemeshedafterbeingdeformedbytheboundarylayergrowthfromadjacentsurfaceareas.

13.

ClickmeshtocreatetheCFDmesh.

Whenthistaskisfinished,twocollectorsareautomaticallycreated:

CFD_boundary_layerandCFD_Tetramesh_core.

.

Step5:

Masksomeofthemeshtoviewtheinteriorelementsandboundarylayers.

YoucanmaskthemeshbyusingtheshortcutkeyF5,andselectelementstobemasked.

Followingisasnapshot.Observetheexcellentmeshqualityproduced.

Step6:

Generateboundaryregionstospecifyboundaryconditions.

Inthissection,definemeshsurfaceregionsusedtospecifyboundaryconditionsinanyCFDcode（FLUENT,StarCD,CFX,etc）.Forexample,assumethatyouaregoingtoexportthemeshforFLUENT.Youneedtocreatethreecollectorstoplacetheboundaries:

inflow,outflow,wall.YouhaveselectedtwonewnamesthatarenotalreadyinyourHyperMeshdatabaseandatthesametimearecompatiblewiththeprefixesrequiredbyFLUENTtorecognizeboundarytypesaccordingtotheirnames.

YouaregoingtoreusethesurfacemeshcontainedincollectorwallbecausethismeshremainedunchangedbytheCFDmeshprocessasthiscomponentwasspecifiedas“fixedwithboundarylayer.”However,thesurfaceareasassociatedwiththeoriginalcollectorsinletandoutletshavebeencompletelyregeneratedandyouneedtocreatenewcomponentsthatwillbenamedinflowandoutflow,respectively.

Step7:

Organizethevolumeelementsintoacollectornamedfluid.

RenamecollectorCFD_Tetramesh_coreasfluid.

Thiscollectorwillholdallthe3-Dvolumeelements.

AccesstheToolpage,organizepaneltomovealltheelementsfromcollectorCFD_boundary_layertocollectorfluid.

Step8:

Createfaceelementsforthecollectorfluid.

AccesstheToolpage,facespaneltoautomaticallygeneratecollector^facescontainingalltheexternalfacesoftheelementsincollectorfluid.ThesamepanelcanbeaccessedfromtheMeshmenubyselectingCheck,thenComponents,thenFaces.

Step9:

Createtwonewcollectorsnamedinflowandoutflow.

Createtwonewcomponentsnamedinflowandoutflow.

Thereisnoneedtospecifyacardimageormaterialname.

Step10:

Organizethefacesintotheinflowandoutflowcollectors.

Nowyouaregoingtomovesomeoftheelementsfromcollector^facestocollectorsinflowandoutflow.

IntheModelbrowser,isolatethe^facescomponent.

AccesstheToolpage,organizepanelandclickoneelementontheinlet/inflowplane（theelementwillbecomehighlighted）.

Selectelementsbyface.

Alltheelementsfromcollector^facesontheinlet/inflowplanewillbeselected.

Selectdestinationcollectorinflow,andclickmove.Similarly,movetheelementsfrom^facesassociatedwiththefouroutletstocollectoroutflow.

ShowtheinflowandoutflowcomponentsintheModelbrowser.

Whendone,youwillhavealltheexteriorsurfacescoloredaccordingtothecollectorswheretheyhavebeenplacedasshowninthefollowingimage.

Step11:

Deletethecollectors^facesandCFD_boundary_layer.

Theremainingelementsincollector^facesarethesameasinwallandyoucandiscardthem.

Deletebothcollector^facesandcollectorCFD_boundary_layer,whichisnowempty.

Step12:

ExportsurfaceandvolumemeshandimportthismeshintoFLUENT.

DisplayonlythecomponentscontainingelementsthathavetobeexportedforFLUENT,thecomponentsare:

fluid,inflow,outflow,andwall.Allothercomponentsshouldnotbevisible.

UsingtheCFDprofileUtilitymenu,CFDI/O,clickFluentCAS/MSHfiles:

Write.

ClickYeswhenaskedifyouwanttocontinueexportinga.casfileforFLUENT.

Specifythe.casfilenameprefixasmanifoldandclickSave.

Apop-updialogwillaskifyouwanttoreuseanother.casfiletoextractmodelandboundaryconditionsinformation.ClickNo.

Becauseyouarenotreusingmodel/boundaryconditionsinformationfromanexisting.casfile,thefileisactuallyverymuchlikea.mshfile.

Amessageboxwindowwillpopupindicatingthatfilemanifold.caswassaved.

Step13:

CreateaFLUENTsimulationcase.

IfyouhaveaccesstoFLUENT,youcanimportmanifold.castocreateanewFLUENTsimulationcaseasfollows

StartFLUENT3dor3ddp.

FromtheFilemenu,selectRead,thenCase....

Selectmanifold.cas.

Afterimportingthisfile,youwillobservethatFLUENThasrecognizedtheboundaryzonesoutflow,inflow,andwallbyname,andthe3-Dvolumezonefluid.Zoneinterior-*isautomaticallycreatedbyFLUENTcontainingalltheinteriorfacessharedbytwo3-Dcells.

SelectDefine,thenselectBoundaryConditions.

Selectzoneinflow,andsettheappropriateboundaryconditionsuchasmass-flow-inletandvelocityinlet.

Changetheboundaryconditiontypefortheremainingsurfacezones,outflowandwall.

HyperMeshallowedyoutoperformthemos