icepak-05-meshing

E-1MeshingE-2Choiceofthreemeshersavailable:TwoHexahedralmeshersSuitedformost(99%)ofelectronicscoolingapplications.Unstructured–ItcanbeusedformostapplicationssatisfactorilyCartesianTetrahedralmesherIntendedforsomecomplexgeometryMustbeusedforellipsoids,ellipticalcylinders,orpolygonalductingIcepakautomaticmeshing:OverviewE-3•Allthemethodsarefullyautomated•CangeneratecomputationalmeshesatvaryinglevelsofcomplexityNoparameterssetParametersdefinedonanobjectbyobjectbasis•Aftermeshing,Icepakloadsthemeshandchecksthekeyqualitymeasure,andreportstheminimumvalueinthemessagewindow.Iftherearecellswithpoorquality,Icepakwillautomaticallydisplaythem.•TheKeymeasuresare:FaceAlignmentforHexahedralAspectRatioforTetrahedralAutomaticmeshingE-4Forhighermeshcountacrossanobject-usex,y,zcountLowandHighelementsize/ratiotorefinearoundobjectsInwardheight/ratiotorefinewithinanobjectOutwardheighttorefinemeshawayfromplanarobjectsBackgroundmesh-setMaxX,Y,ZsizesUsefluidblockstorefinethemeshlocallyExaminemeshusingsurfaceplotsandcutplanesAlwayscheckqualityusingdiagnosticMaintainsufficientmeshdensitytocapturephysicsGenerateFirstCutMeshCoarsedefaultoptionswithMaxX,Y,Zsetto1/10thor1/20thofdomainsizeRefinetheMeshExaminetheMeshSolveGeneratenewMeshYesNoRe-examinetheMeshOK?Meshingstepsandconsiderations•Usecoarsemeshforinitialsolutionsandforobservingtrends•UsesuitablyrefinedmeshforfinalsolutionE-5TwoHexahedralMeshersUnstructured-Meshwillfollowthegeometry-Usesallelementtypestofitthemeshtothegeometry-BackgroundmeshismadeofhexahedralelementsCartesian-Meshwillbestructuredmeshconsistingonlyofhexahedralelements-Stair-stepapproximationstonon-rectangulargeometryBothofthesemesherscanbeusedtomeshassembliesseparately.Thiswillbediscussedinmoredetaillater.Bothmeshershavethesameglobalandper-objectsettings.HexahedralmeshingE-6Duringthemeshingprocessforthehexahedralmeshers,Icepakusestheseparationvaluetocheckthemodel.Icepakcalculatesthedistancesbetweenobjectsineachco-ordinatedirectionandwillalignobjectswheretheirseparationissmallerthanthetoleranceset.Asaruleofthumb,thetoleranceshouldbeapproximately1/10thofthesmallestdimensioninthemodel.Thiswillensurethatanychangesinvolumewillnotsignificantlyaltertheresults.Iftheseparationissethigherthan10%,butlessthan50%ofthesmallestdimension,Icepakwillpromptyoutoeither-Stopmeshingandchangemanually-Continueandchangeautomaticallyto10%-IgnoreandcontinueIftheseparationislargerthan50%,Icepakwillpromptyouto-Stopmeshing-ContinueandchangeautomaticallyTheseparationcanbeseteitherinthemeshingpanelorinthesettingsconfigurationpanelCheckingduringmeshingE-7Icepakoperatesona“cocooning”methodologyEachobjectismeshedindividuallyasclosetothespecificationsdefinedaspossibleFirstcombinesadjacentobjectstogether–Createssinglegroupofmultipleobjectsto“O”gridtogetherThencreatesthebackgroundCartesianmesh–MaxCellsizeiscontrolledbyMaxx,MaxyandMaxzvaluesCutsoutasectionofthemesharoundthegroupedobjectsandreplacesthemeshwithanunstructuredmesh-the“O”-Meshregion–Thisallowsforafinermeshtobegeneratedclosetoobjects–Inopenspacesbetweenobjectsthemeshistessellatedwithlargerelements–MinimizecomputationalcostsMeshingisthemostcriticalaspectofCFDmodeling:AgoodmeshisabsolutelyessentialforagoodsolutionHexa-unstructuredmeshingmethodologyE-8ElementsofanIcepakmeshE-9GlobalSettings-forrefiningmeshDefaultSettings-meshertype,backgroundmeshsettingsPanelstogenerate,Display,Checkquality,andExporttoIdeasHexahedralmeshing:GenerationpanelE-10MesherTypeHexa-Unstructured,Hexa-Cartesian,TetrahedralUnitstouseMaxX,MaxY,MaxZControlthesizeofthelargestcellallowableinthebackgroundmeshInitHeightMaximumheightoffirstcellintothedomainonallobjectswithinthemodelObjectParamsIndividualparametersSeparationToleranceusedwhenmeshingtoremoveanysmallgaps/misalignmentsDefaultsettingsE-11MaxX,Y,ZBydefaultthisis1/20thofthecabinetdimensions1/10thofthedomainsizeissufficientforacoarsegridValuessmallerthan1/20thdomainsizeisrarelyneededandisnotrecommendedThesearenotmeanttobeusedtorefinethemeshclosetoobjects,butpurelytogenerateareasonablebackgroundmeshInitHeightRecommendedthatyoudonotsetthisonlargemodelsasitcanresultinverylargemeshcountsSeparationItisrecommendedthatyousetthisto10%ofthesmallestdimensioninyourmodelfortypicalcalculationstopreventanylargevolumechangesoccurringthatmightleadtoinaccuraciesintheresults.RecommendationsE-12NormalMesher–ProvidesanacceptablemeshformostsituationsprovidedbackgroundgridisreasonableCoarseMesher–Providesacoarsemesh“firstcut”meshthatcanberefinedlocallyMesherdefaultsettingsinclude:Minelementsinfluidgap-MinimumnumberofcellsinbetweenadjacentfacesofcloselyspacedobjectsMinelementsonsolidedge-MinimumnumberofcellstobeplacedontheedgeofanobjectMaxO-gridheight-MaximumheightoftheO-gridregionfromthesurfaceofanobjectMinelementsinfluidgap=2Minelementsinfluidgap=3Globalsettings(1)E-13MaximumSizeRatioControlsthegrowthrateofcellsizeTheGrowthratioofelementsawayfromsurfacescanbecontrolledusingthissetting.Dx2/Dx1MaxsizeRatiosettingSolidregionFluidRegionDx2Dx3Dx1Globalset