Transitional Delayed Detached Eddy Simulation of ... · Dr. Jim Coder Assistant Professor Hector D....
Transcript of Transitional Delayed Detached Eddy Simulation of ... · Dr. Jim Coder Assistant Professor Hector D....
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TransitionalDelayedDetachedEddySimulationof
Multielement,High-LiftAirfoilsDr.JimCoder
AssistantProfessor
HectorD.Ortiz-MelendezGraduateResearchAssistant
DepartmentofMechanical,Aerospace&BiomedicalEngineering
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Introduction
• High-liftisacriticalpartofaircraftdesign• Maximumliftcapabilitydetermineswingplanformarea• Wingareahasleading-ordereffectoncruisedrag
• Difficult-to-predictaerodynamicphenomenainhigh-liftsystems• Laminar-turbulenttransition• Smooth-bodyseparation• Strongcompressibilityeffectsevenatlowflightspeeds• Non-linearinteractionsbetweenelements(c.f.A.M.O.Smith[1975])
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Background
• Computationalfluiddynamicsoftenrequiredforhigh-liftanalyses• Viscouseffects,compressibility,andnon-linearinteractions
• AIAAHigh-LiftPredictionWorkshop(HiLiftPW)seriesconductedtoassesscurrentstateoftheartinCFDcapabilities• PredominatelyRANS,withsomeLattice-Boltzmann• RANSunabletoreliablypredictsmooth-bodyseparation• TransitionmodelingrecognizedasbeinginfluentialforTrapWing(HiLiftPW-1)andJAXAStandardModel(HiLiftPW-3)cases• Timeaccuracymayimprovesolutionphysicality
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Background
• HybridRANS/LESModeling• ExtensionofRANStomitigateexcessivedissipationinnon-attachedflows
• Canimprovepredictionofflowseparation• DelayedDetachedEddySimulation(DDES)iswidelyused• Requirestime-accuratesolutiononfine-resolutiongrids
• TransitionModeling• RecentdevelopmentswithRANS-basedmodels• Amplificationfactortransportmodel(AFT2017b)hasshownpromiseforhigh-liftpredictions(c.f.Coder,Pulliam,andJensen[2018])
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DesiredModelingCapabilities
• TransitionalhybridRANS/LESmethodsarethenextprogression• Currentapproachesbasedonɣ-Reθt transitionmodels• SST-basedLangtry-Menter +HRLES(Hodara andSmith)• SA-basedMedida-Baeder +DDES(Baeder etal.)
• Goal: DemonstratearobusttransitionalDDESmethodologyforhigh-liftpredictionbasedonSA-AFT2017bturbulence/transitionmodelingframework
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AFT-basedTransitionalDDES
• SA-neg-RCmodel
• AFT2017bmodel
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AFT-basedTransitionalDDES
• Intermittencygrowthoccursonceñ reachesNcrit (takentobe9)• InteractswithSAmodelthroughft2term
• DDESusesasensortodetectattachedboundarylayers
• Extrarobustnessneededtoaccountforlaminarboundarylayers
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ModelImplementation• SA-neg-RC-DDES-AFT2017binNASAOVERFLOW2.2nsolver• Slightmodificationsofreleaseversionofcode
• Numericalmethodsforcurrentwork• 5th-order-accurate,WENOscheme(RHS)formeanflowconvectivefluxes
• Upwinded Roefluxes• 3rd-order-accurateschemeforturbulence/transitionequations• ImplicitBDF2temporaladvancement
• Δt*=0.0025• 15Newtonsubiterations (fixed)
• D3ADIalgorithm(LHS)
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TestCase– MD30P/30N
• Three-elementhigh-liftairfoil• DevelopedbyMcDonnell-Douglas• TestedinNASALangleyLTPT• Availabledataaretransitional(e.g.untripped)
Stowed Chord 0.5588 m
SlatDeflection 30°
SlatGap 2.95%
SlatOverhang -2.5%
FlapDeflection 30°
FlapGap 1.27%
Flap Overhang 0.25%
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GridSystem
• OversetgridsystemgeneratedusingPointwiseandChimeraGridTools• Spanwise extentof0.18c• Periodicboundaries
• Griddimensions• Slat:209x65x41• Main:505x65x41• Flap:205x65x41• Total: 11.7million
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QualitativeModelVerification
• FlowStructure(α=8°)
VelocityContourswithWakeStructure(Q-criterion)
Q-criterionIsosurface(ColoredbyVorticityMagnitude)
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QualitativeModelVerification
• IntermittencyandTransitionPatterns(α=8°)
IntermittencyField SurfaceTurbulenceIndex
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LiftCurves
• TotalLiftCoefficient• DDEScausesadecreaseinliftcomparedtoRANS• Transitionincreasesliftcomparedtofullyturbulent• TransitionalDDEShasoverallbestagreement,especiallyatlowerangles• Stallcharactermissedbyallmethods
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LiftCurves
• SlatLiftCoefficient• DDESslightlylowerstheliftcoefficient,andtransitionincreasesit• Allmethodsfailtopredictlift-curveslopatlowerangles• Noneofthemethodsexhibitdiscerniblestallbehavior
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LiftCurves
• Main-ElementLiftCoefficient• DDESlowerstheliftcoefficient,whiletransitionincreasesit• TransitionalDDESseemstobehavebetteratlowerangles,butoverpredicts maximumlift• FullyturbulentDDESbetteratmaximumlift,butnotatlowerangles
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LiftCurves
• FlapLiftCoefficient• TransitionalDDESagreesbestforloweranglesofattack,butdoesnotshowasmuchreductioninliftathigherangles
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PressureDistributions(α=8°)
• Flapexhibitsmoreseparationinfullyturbulentcase• Increasedflapcirculationaidsmainelementandslat
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PressureDistributions(α=19°)
• Bothtransitionalandturbulentagreequalitativelywellwithexperiment• Transitionalsolutionagreesbetterforflap• Slightdifferenceinpressurehasmeasurableimpactonlift
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PressureDistributions(α=21°)
• Transitionalcaseshowsmore-negativepressurepeaksonflapandmainelement• Lessseparationeffectsonflapwithtransition• Mainelementnotseparated;however,itsloadingisnotsevere
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VelocityProfiles(α=8°)
Velocity Magnitude
x/c
0.3 0.35 0.4 0.45 0.50
0.02
0.04
0.06
0.08
CFD - TransitionalCFD - TurbulentExperimental
Velocity Magnitude
x/c
0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34 0.360
0.02
0.04
0.06
0.08
CFD - TransitionalCFD - TurbulentExperimental
x/c=0.1075(main) x/c=0.4500(main)
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VelocityProfiles(α=19°)
Velocity Magnitude
x/c
0.4 0.45 0.5 0.55 0.60
0.02
0.04
0.06
0.08
CFD - TransitionalCFD - TurbulentExperimental
Velocity Magnitude
x/c
0.2 0.25 0.3 0.35 0.40
0.02
0.04
0.06
0.08
CFD - TransitionalCFD - TurbulentExperimental
x/c=0.1075(main) x/c=0.4500(main)
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VelocityProfiles(α=19°)
• a
Velocity Magnitude
x/c
0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.320
0.02
0.04
0.06
0.08
0.1
0.12
CFD - TransitionalCFD - TurbulentExperimental
Velocity Magnitude
x/c
0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.34 0.36 0.38 0.40
0.02
0.04
0.06
0.08
0.1
0.12
CFD - TransitionalCFD - TurbulentExperimental
x/c=0.8500(main) x/c=0.8982(flap)
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VelocityProfiles(α=19°)
Velocity Magnitude
x/c
0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.260
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
CFD - TransitionalCFD - TurbulentExperimental
Velocity Magnitude
x/c
0 0.04 0.08 0.12 0.16 0.2 0.240
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.22
0.24
CFD - TransitionalCFD - TurbulentExperimental
x/c=1.0321(flap) x/c=1.1125(flap)
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Conclusion• TransitionalDDESmethodologyestablishedandimplementedintotheOVERFLOW2.2nsolver• BasedonSA-neg turbulencemodelwithAFT2017btransitionmodel• Couplingstrategyextensibletoothertransitionmodels
• ConsistentimprovementinpredictionsforMD30P/30NtestcasewithtransitionalDDESoverfullyturbulentDDESandeithertransitionalorturbulentRANS• Bothintegratedloadsandvelocityprofiles
• Accuratepredictionofflaploadingappearstobemostcriticalfactorforthiscase
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Acknowledgments
• ThismaterialisbaseduponworksupportedbytheNationalAeronauticsandSpaceAdministration(NASA)undercooperativeagreementawardnumberNNX17AJ95A(UniversityLeadershipInitiative)
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