NASA Ames Research Center Contribu4on to GMGW-1

WilliamM.Chan

NASAAmesResearchCenter

PID02

1stAIAAGeometryandMeshGenera?onWorkshopDenver,COJune3-4,2017

SummaryofGridsGenerated

Case Code(s) Star4ngGeometryModel

GridType NumberGridLevels

HL-CRMfullgap ChimeraGridTools STEP OversetStructured 4

HL-CRMpar?allysealed ChimeraGridTools STEP OversetStructured 1

GMGW-1,DenverCO,June2017 2

Chan,W.M.,DevelopmentsinStrategiesandSoQwareToolsforOversetStructuredGridGenera?onandConnec?vity,AIAA2011-3051.Chan,W.M.,Gomez,R.J.,Rogers,S.E.,Buning,P.G.,BestPrac?cesinOversetGridGenera?on,AIAA2002-3191

ChimeraGridTools(CGT)-Acollec?onofsoQwaretoolsforpre-andpost-processingofCFDsimula?onusingstructuredoversetgrids-Geometry/GridTools:geometry/gridprocessing,algebraicandhyperbolicsurfaceandvolumegridgenera?on-AnalysisTools:gridquality,aerodynamicloads,flowsolu?on-HighLevelTools:OVERGRIDgraphicalinterface,ScriptLibrary(200+macros)

GeometryImportandPrepara4on

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•  ImportSTEPfileintoANSA-Generatetriangula?onthataccuratelyresolvesgeometry-Gridresolu?oninhighcurvatureregions(leadingedges)needstobeequalorhigherthanthestructuredsurfacegridstobegenerated•  Noimportdifficul?es

•  Nomodifica?onsperformedongeometry

•  Lessonslearned-IntroduceCADedgealongallleadingedges-BecarefulontolerancesnearCADfaceboundaries(doesnotaffectstructuredoversetsurfacemeshgenera?oniflocalsurfacenormalsarealmostconsistent)

MeshGenera4onProcessSummary

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•  Surfacemeshgenera?on-Iden?fydomainsforalgebraicmeshing(2,3,or4ini?alcurves)hyperbolicmeshing(1ini?alcurve)-Prescribegridpointdistribu?ononini?alcurves-CreatesurfacemeshusingTFIorhyperbolicmarching•  Volumemeshgenera?on(near-body:hyperbolic,off-body:Cartesian)•  Domainconnec?vity:Distance-basedholecuts(C3P),orX-rayhole-cut(OVERFLOW-DCF)•  Meshexportformats:Gridsystem-PLOT3DOversetmeshconnec?vitydata–XINTOUT•  En?reprocessrecordedinTclscriptsystembasedonCGTScriptLibrary

5

Hyperbolicgridmarchingdistanceschosentoprovideproperoverlapatmediumlevel(e.g.,5-pointoverlapfor5-pointflowsolverstencil)Insomeregions:-Insufficientoverlapatcoarselevel-Toomuchoverlapatfineandextrafinelevels

Coarse Medium

Fine ExtraFine

MeshGenera4onIssues(I)ParameterAdjustmentsatDifferentMeshResolu4onLevels(A)

6

Finergridspacinginconcavecornersinfinerlevels-Needtoadjustsmoothingparametersforhyperbolicmarching

CoarseMediumFineExtra-fine

MeshGenera4onIssues(I)ParameterAdjustmentsatDifferentMeshResolu4onLevels(B)

7

TwoproblemswerediscoveredaQerini?alversionofmeshsystem1.Averysmallnumberofnega?vecellvolumesfound-Disregardedini?allysinceflowsolverisnodecenteredFix:lowersmoothingvalues2.TFIsurfacemesharoundflapleadingedgehadlargestretchingra?o-Badprojec?ontogeometrydefini?onfromlackofleadingedgegeometrycurve-Surfacegridpointsareongeometry,butsurfacecellsarefarfromgeometryFix:introduceleadingedgecurve,redoTFIandprojec?ontogeometrydefini?on

MeshGenera4onIssues(II)Nega4veCellVolumesandBadProjec4on

MeshSta4s4cs

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GeometryModel

GridType GridLevel

Blocks SurfaceGridPoints

VolumeGridPoints

OrphanPoints

HLCRMFullGap

OversetStructured Coarse 72 0.27M 24.1M 2

Medium 72 0.51M 65.4M 6

Fine 76 1.02M 189.3M 16

Extra-Fine

102 2.08M 564.9M 119

HLCRMPar?alSeal

OversetStructured Medium 73 0.53M 66.3M 22

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GridAKributeHistogramsforFullGapMediumMesh

Surface Mesh Wing Upper Surface

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Surface Mesh Wing Lower Surface

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Surface Mesh - Wing Slat LE at Root

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Surface Mesh - Wing Flap TE at Root

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Surface Mesh - Wing Tip LE

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Surface Mesh - Wing Tip TE

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Flap Gap Upper Surface

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Volume Mesh Cut at y=277.5

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Volume Mesh Cut at y=638

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Volume Mesh Cut at y=1050

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MeshEvalua4on:SurfaceandVolumeMeshes

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•  Must-pass•  Jacobian>0atvolumemeshver?cesascomputedbyOVERFLOWflowsolver•  Cellvolume>0(decomposi?oninto6tets)•  Noself-intersec?onofvolumegridpointsagainstsurfacegrid

•  Mostly-pass•  Stretchingra?omostlyaround1.2

•  Adherencetomeshingguidelines•  Trailingedgegridspacingmadetobecon?nuousaroundfinitethicknesstrailingedge•  Mul?-griddablenumberofpointsineachdirec?onisnotneededsinceOVERFLOWflowsolverhasnosuchrestric?ons

•  Lessonslearned•  Needna?veCAD,STEP,IGESgeometryinterroga?ongridtool(e.g.,EGADS)1.projectsurfacegridpointsontogeometrydefini?on2.checkdistanceofsurfacegridpointsfromgeometrydefini?on

21

Count,loca?on,andspread(CGT:OVERGRID)

Total=25,sparsepointsawayfromsurface

MeshEvalua4on:OversetConnec4vity(I)OrphanPoints

22

-Cellvolumera?ohistogramtable(CGT:intchk)andloca?onmap(CGT:OVERGRID)-Badra?o=>gradientscannotbetransferredaccuratelybetweengrids

Cellvolumera?o<0.01

CellVolumeRa?o#Pts.%Total0.5<=R<=1.0271426848.260.2<=R<0.5170503630.320.1<=R<0.267023211.920.01<=R<0.15250489.340.001<=R<0.0196310.17R<0.001210.37E-03

Otherapributesthatcouldbechecked-Cellaspectra?o,orienta?on

MeshEvalua4on:OversetConnec4vity(II)Compa4bilityofCellAKributesBetweenFringePoint

andDonorStencil

23Convertedfringepoints

-Insufficientgridoverlaptosupportdoublefringelocally-Op?ontoconvertfromdoublefringetosinglefringe=>full5-pointdifferencingstencilnotsupportedinflowsolver(loweraccuracy,robustness)

SinglefringeregionLoca?onmap(CGT:OVERGRID)

MeshEvalua4on:OversetConnec4vity(III)ConversiontoLowerNumberofFringeLayers

24

Histogramtable(CGT:intchk)andloca?onmap(CGT:OVERGRID)

StencilQualityCount%TotalQ=0.000.000.0<Q<0.100.000.1<=Q<0.200.000.2<=Q<0.348580.170.3<=Q<0.4121200.420.4<=Q<0.5146600.510.5<=Q<0.6140540.480.6<=Q<0.7195040.670.7<=Q<0.8247880.850.8<=Q<0.9232800.800.9<=Q<1.0453171.56Q=1.0257385894.54

Stencilquality<0.26

MeshEvalua4on:OversetConnec4vity(IV)DonorStencilQuality

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MeshEvalua4on:FlowSolverTestSeeHigh-LiQPredic?onWorkshop3talksonOVERFLOWandLAVAresults

CoarseMediumFineX-Fine

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-Developconnec?onbetweensurfacegridgenera?onsoQwareandgeometryinterroga?ontool(e.g.,usingEGADS)tobringsurfacegridpointsontona?veCAD,STEP,orIGES-Developmoreautomatedoversetsurfacemeshgenera?onalgorithmandsoQware(“StrategiesTowardAutoma1onofOversetStructuredSurfaceGridGenera1on”,tobepresentedatAIAAAvia?on2017)

-DevelopmoregridqualitychecksoQware(minmax,histograms,contourplotsofvariousgridapributes)

FutureTechnology

Summary

•  Oversetsurfacegridgenera?onrequiresthemostmanualeffort•  Crea?onofgridsystemswithdifferentmeshresolu?onlevelsusingthescrip?ngapproachisnotassimpleasfirstan?cipated(marchingdistanceandsmoothingparameteradjustments)

•  Needtobeabletoprojectsurfacegridpointsbacktona?veCAD,STEP,orIGESgeometrydefini?on

•  Needmoregridqualitychecktools

GMGW-1,DenverCO,June2017 27

Task(Mediumfullgapmesh,1stmeshgenerated) Time(hr.) %ofTotal

Geometryprocessing/Ref.triangula4ongenera4on 3.75 5.5

Surfacegridgenera4on 56.05 81.7

Volumegridgenera4on 4.50 6.6

Domainconnec4vity(C3P) 1.20 1.7

Inputprep.(flowsolverb.c.,post-processing) 3.1 4.5

Total 68.6 100

Acknowlegement:NASAT3Project,Transforma?veAeronau?csConceptsProgram(ARMD)