High Lift Prediction Workshop - A Comparison of RANS, URANS, … · 2018-01-24 · • Starting...

AComparisonofRANS,URANS,andDDESforHigh-LiftSystemsfrom

HiLiftPW-3

RiccardoBalinandKennethE.JansenAnnandH.J.Smead DepartmentofAerospaceEngineeringSciences

UniversityofColorado- Boulder

AIAASciTechForumJanuary10th,2018

Outline

• Overviewofcasesstudiedandnumericalcomputations

• Numericalresults• GridconvergencestudyonHL-CRMmodel• EffectsofinitialconditionsJSM• RANS,URANS,andDDESonJSM

• Conclusions

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WorkshopCasesStudiedHL-CRM

JSM

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Cases AnglesofAttack(AoA) Notes

1a 8°,16° • gridrefinementstudy• full-gapgeometry• B1committeegrids,Coarse-Medium-Fine

1b 16° • gridadaptationstudy• full-gapgeometry• in-house,Simmetrix grids


2a 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°

• nonacelle• C1committeegrid,M

2b 21.57° • nonacelle• DDES• adaptationstudy,in-houseSimmetrix grids

2c 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°

• withnacelle• C1committeegrid,M


JSM

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2a 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°



2c 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°


inprogress

inprogress


JSM

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2a 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°



2c 4.36°,10.47°,14.54°,18.58°,20.59°,21.57°


inprogress

inprogress

NumericalSet-Up

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• ComputationscarriedoutwithPHASTAstabilized,finiteelementflowsolver.• Spalart-Allmaras (SA)one-equationmodel(QCRresultsrun,notfocushere).

• Allcomputationsrunfullyturbulent,nospecifiedtransition.

• IncompressibleNavier-Stokesequationssolved.

• Allresultsarewithglobaltimestepping:willcitetimestepinchordflights.

SliceacrosswingsectionoftheJSMgridused

HL-CRM– GridConvergenceStudy

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Lift:• About5%under-predictionwithCoarse• Mediumwithin1%ofFineforbothAoA• Mediumconverged to“true”solution

Liftanddragcoefficientsvs.numberofgridpointsto-2/3power

Drag:• Slowerconvergence,Med.gridnot

within1%ofFine

LiftCoefficient DragCoefficient

Coarse

MediumFine


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Pressurecoefficientprofilesat24%and68%ofthehalf-spanfor16° AoA

• ExcessiveflowseparationoverbothflapswithCoarsegrid• MediumandFinegridsalmostidentical.

PS2

PS6


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Pressurecoefficientprofilesatotherpressurestationsfor16° AoA


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Pressurecoefficientprofilesatotherpressurestationsfor16° AoA


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SurfaceLineIntegralConvolutionofWallShearStressat16° AoA


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Separationlineoninboardflapatmid-chord


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Separationlineonoutboardflapfurtherdownstream,flowstaysattachedforlonger


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SurfaceLineIntegralConvolutionofWallShearStressat16° AoA –Zoomonflapgap


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SurfaceLineIntegralConvolutionofWallShearStressat16° AoA –Zoomonflapgap

Largerregionofseparatedflowattheflapgap


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Sliceat24%ofhalf-spancoloredbyspan-wisevorticity

Negativevorticity(outofscreen)Positivevorticity(intoscreen)

Flowdirection


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Distortedshearlayerduetolackofresolution

Shearlayersaccuratelycomputed


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Morenarrowjetofirrotationalflowthoughgap,slowermovingfluidovertheflapleadingedge


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Boundarylayerseparation


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Interimsummary:• Mediumgridsufficientforconvergencetowithin1%forlift,slightlymore

than1%fordrag.• Coarsegridhasexcessiveseparationovertheflaps.• Causeofexcessiveseparationisthepoorresolutionoftheflapcoveshear

layerseparation,themainelementwake,andtheflapgap.

Adaptivity:• Thiscaseposesadifficultchallengeforadaptivity:Mediumgridonly3xlargergives

closetofinesolutionleavesnarrowmarginforadaptive“win”.Finegridonly9xlarger.

• Inourexperience,fullyautomaticanisotropicadaptivity canrequire4ormorecyclesofadaptationandresultingridsaslargeasmedium.Worthwhile?

• Weexploredasimplerapproach:• StartadaptationfromagridthatusesCoarse“surface”gridwithselected

improvementingapsandMediumnormalspacing,growth,andtrailingedgethickness(newmeshis14.5Mnodesvs{8,26.5,70}Mfor{C,M,F}),

• Attempt,inoneadaptation,toimprovelocationsofsurfacegridinadequacytothesamelevelasfine.

• Goal:yieldsamequalityasfineforlesscomputationaleffortthanmedium.

HL-CRM– CustomGridforAdaptivity

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Pressurecoefficientprofilesatinboardpressurestationsfor16° AoA


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Pressurecoefficientprofilesatoutboardpressurestationsfor16° AoA


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Pressurecoefficientprofilesatoutboardpressurestationsfor16° AoA

SelectimprovementsofB2CommitteeCoarsegrid(normalspacing,trailingedges,andmodestgapresolution)eliminatestheextraseparationandbringtheotherwiseB2CommitteeCoarsegridresolutionintosameflowregimeasMediumandFinegrids(e.g,.1%CL difference).

PreliminaryAdaptivity

Skinner,Doostan,Peters,Evans,andJansen 24

PreliminaryAdaptivity:PreserveSurfaceAnisotropy


Adaptivity:FineGridResolutionOnlyWhereRequired


JSM– EffectsofInitialConditions

• MostgroupsusedsteadyRANS,butobservedtwomainstrategiesforinitialconditions• Startingeveryangleofattackfromfree

streamconditions• Usingconvergedsolutionatsmallerangleof

attack– alphacontinuation

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RANScomputationsontheJSMno-nacellemodelfrom3rd AIAAHigh-LiftWorkshop1

• Significantvariationinparticipantpredictionsdueto:• Flowsolver(numerics)• Turbulencemodel• Modelingstrategy(initialconditions(IC),timestepsize,etc.)• Grids

numericalexperiment

JSMLiftCurve


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LinearSectionoftheLiftCurve• MultiplesolutionsforthesameAoA• FreestreamICleadstounder-predictionoflift• Alphacontinuationresultsmatchexperimentalliftwell

Liftcoefficientvs.angleofattack(AoA)


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LinearSectionoftheLiftCurve– 14.54° AoA

• FreestreamICshowsmassiveseparationdownstreamoftracks7and8

• Alphacontinuationsolutiononlyseparateddownstreamoftrack8,agreeingwithexperimentaldata

Time-averagedwallshearstressalongthestream-wisedirection(Wss_X)

FreestreamIC Alphacontinuation

Tr8Tr7

Tr8Tr7


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LinearSectionoftheLiftCurve– 14.54° AoA Inwakeoftrack7

Inwakeoftrack8


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Maximumliftandstall• MultiplesolutionsforthesameAoA• Bothapproachesover-predictmaximumliftsignificantly• StallonlypredictedwithfreestreamIC

Liftcoefficientvs.angleofattack(AoA)


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• Bothsolutionsmissrootseparationseeninexperiment,over-predictinglift

• UsingfreestreamICleadstoseparationattrack7,betteragreementinliftforwrongreason,wrongstallmechanism

Time-averagedwallshearstressalongthestream-wisedirection(Wss_X)

FreestreamIC Alphacontinuation

Experimentaloilflowimageat21° ofJSM

Tr8Tr7

Tr8Tr7


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Interimsummary:• MultiplesolutionsexistforthesameAoA dependingonICs• Alphacontinuationapproachprovidesimprovedflowfieldsolutions• Alphacontinuationisparticularlyeffectiveinlinearpartoftheliftcurve• Freestreaminitialconditionscanleadtooverlyseparatedflow

• Alphacontinuationcanbecomputationallyexpensive,requiresmultiplecomputations

• CanweconvergetothehighliftsolutionifthetransientphaseisnotneglectedwithsteadyRANS,andinsteadweperformaURANSfromfreestreamIC?

JSM– UnsteadyRANS

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• URANSfromfreestreamICat21.57° AoA

• ∆𝑡# = ∆𝑡𝑐&'#/𝑈* = 0.05 and∆𝑡# = 0.01

• timeindependentsolutionachievedwith∆𝑡# = 0.05

• URANSachievessamesolutionassteadyRANSwithalphacontinuation,forfractionofcost

HiLiftPW-3,DenverCO,June2017 35

JSM– DDESPressureProfiles:Post-Stall

HiLiftPW-3,DenverCO,June2017 36

StartingfromURANSmayormaynotbeOKbecauseseparated.ResolutioninadequateforDDES.

JSM– DDESPressureProfiles:Post-Stall

Conclusion

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• JSM:MultiplesolutionsexistforthesameAoA dependingonICs• Alphacontinuationapproachagreeswellwithexperimentsperformed

similarly• RANSfromfreestreaminitialconditionscanleadtooverlyseparatedflow• URANSachievessameresultsasalpha-continuationwithsubstantiallyless

cost(forasingleangleofinterest).• PreliminaryDDESperformslightlybetterthanURANSbutmorerefinement

needed• SofarDDESisnotshowingrootstallasseeninexperiments• Willitneedbettertransitionmodeltocapturethiseffect?• HLCRM:coarsegridshowsexcessiveseparationbutmediumandfinein

goodagreement.• Adaptivegridsbeingpursuedtounderstandifcoarsegrid+adaptivity can

getfinegridqualityatlessthanmediumgridcost.• Semi-automaticadaptivity thatpreservessurfacegridanisotropyisshowing

promisetoreducenumberofadaptationcycles.

Acknowledgements

AnawardofcomputertimewasprovidedbytheInnovativeandNovelComputationalImpactonTheoryandExperiment(INCITE)program.ThisresearchusedresourcesoftheArgonneLeadershipComputingFacility,whichisaDOEOfficeofScienceUserFacilitysupportedunderContractDE-AC02-06CH11357.Specifically,theproductionrunsweredoneonMiraandCetuswhilethepost-processingwasdoneonCooley.ThisworkalsoutilizedtheJanus supercomputer,whichissupportedbytheNationalScienceFoundation (awardnumberCNS-0821794)andtheUniversityofColoradoBoulder.TheJanussupercomputerisajointeffortoftheUniversityofColoradoBoulder,theUniversityofColoradoDenverandtheNationalCenterforAtmosphericResearch.Specifically,theseresourceswereusedinmeshgenerationandpre-processing.Finally,wearegratefultoacknowledgeSimmetrix Inc.fortheirmeshingandgeometricmodelinglibraries,Acusim SoftwareInc.(acquiredbyAltairEngineering)fortheirlinearalgebrasolverlibrary,andKitware (ParaView)fortheirvisualizationtools.TheSCOREC-coremeshpartitioningandadaptationtoolsusedinthisresearchweresupportedbytheU.S.DepartmentofEnergy,OfficeofScience,OfficeofAdvancedScientificComputingResearch,underawardDE-SC00066117(FASTMath SciDAC Institute).

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Questions

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References

1J.Slotnick,T.Wayman,D.Simpson,andS.Fowler,“HiLiftPW-3:Case2Results.”https://hiliftpw.larc.nasa.gov/Workshop3/HiLiftPW3-Presentations/Summary_Case2.pdf.

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