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TransitionalDelayedDetachedEddySimulationof

Multielement,High-LiftAirfoilsDr.JimCoder

AssistantProfessor

HectorD.Ortiz-MelendezGraduateResearchAssistant

DepartmentofMechanical,Aerospace&BiomedicalEngineering

volAIR - revolutionary Aerodynamics Innovation and Research

Introduction

• High-liftisacriticalpartofaircraftdesign• Maximumliftcapabilitydetermineswingplanformarea• Wingareahasleading-ordereffectoncruisedrag

• Difficult-to-predictaerodynamicphenomenainhigh-liftsystems• Laminar-turbulenttransition• Smooth-bodyseparation• Strongcompressibilityeffectsevenatlowflightspeeds• Non-linearinteractionsbetweenelements(c.f.A.M.O.Smith[1975])


Background

• Computationalfluiddynamicsoftenrequiredforhigh-liftanalyses• Viscouseffects,compressibility,andnon-linearinteractions

• AIAAHigh-LiftPredictionWorkshop(HiLiftPW)seriesconductedtoassesscurrentstateoftheartinCFDcapabilities• PredominatelyRANS,withsomeLattice-Boltzmann• RANSunabletoreliablypredictsmooth-bodyseparation• TransitionmodelingrecognizedasbeinginfluentialforTrapWing(HiLiftPW-1)andJAXAStandardModel(HiLiftPW-3)cases• Timeaccuracymayimprovesolutionphysicality


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])


DesiredModelingCapabilities

• TransitionalhybridRANS/LESmethodsarethenextprogression• Currentapproachesbasedonɣ-Reθt transitionmodels• SST-basedLangtry-Menter +HRLES(Hodara andSmith)• SA-basedMedida-Baeder +DDES(Baeder etal.)

• Goal: DemonstratearobusttransitionalDDESmethodologyforhigh-liftpredictionbasedonSA-AFT2017bturbulence/transitionmodelingframework


AFT-basedTransitionalDDES

• SA-neg-RCmodel

• AFT2017bmodel


AFT-basedTransitionalDDES

• Intermittencygrowthoccursonceñ reachesNcrit (takentobe9)• InteractswithSAmodelthroughft2term

• DDESusesasensortodetectattachedboundarylayers

• Extrarobustnessneededtoaccountforlaminarboundarylayers


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)


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%


GridSystem

• OversetgridsystemgeneratedusingPointwiseandChimeraGridTools• Spanwise extentof0.18c• Periodicboundaries

• Griddimensions• Slat:209x65x41• Main:505x65x41• Flap:205x65x41• Total: 11.7million


QualitativeModelVerification

• FlowStructure(α=8°)

VelocityContourswithWakeStructure(Q-criterion)

Q-criterionIsosurface(ColoredbyVorticityMagnitude)


QualitativeModelVerification

• IntermittencyandTransitionPatterns(α=8°)

IntermittencyField SurfaceTurbulenceIndex


LiftCurves

• TotalLiftCoefficient• DDEScausesadecreaseinliftcomparedtoRANS• Transitionincreasesliftcomparedtofullyturbulent• TransitionalDDEShasoverallbestagreement,especiallyatlowerangles• Stallcharactermissedbyallmethods


LiftCurves

• SlatLiftCoefficient• DDESslightlylowerstheliftcoefficient,andtransitionincreasesit• Allmethodsfailtopredictlift-curveslopatlowerangles• Noneofthemethodsexhibitdiscerniblestallbehavior


LiftCurves

• Main-ElementLiftCoefficient• DDESlowerstheliftcoefficient,whiletransitionincreasesit• TransitionalDDESseemstobehavebetteratlowerangles,butoverpredicts maximumlift• FullyturbulentDDESbetteratmaximumlift,butnotatlowerangles


LiftCurves

• FlapLiftCoefficient• TransitionalDDESagreesbestforloweranglesofattack,butdoesnotshowasmuchreductioninliftathigherangles


PressureDistributions(α=8°)

• Flapexhibitsmoreseparationinfullyturbulentcase• Increasedflapcirculationaidsmainelementandslat



• Bothtransitionalandturbulentagreequalitativelywellwithexperiment• Transitionalsolutionagreesbetterforflap• Slightdifferenceinpressurehasmeasurableimpactonlift



• Transitionalcaseshowsmore-negativepressurepeaksonflapandmainelement• Lessseparationeffectsonflapwithtransition• Mainelementnotseparated;however,itsloadingisnotsevere


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


x/c=0.1075(main) x/c=0.4500(main)



Velocity Magnitude

x/c

0.4 0.45 0.5 0.55 0.60

0.02

0.04

0.06

0.08


Velocity Magnitude

x/c

0.2 0.25 0.3 0.35 0.40

0.02

0.04

0.06

0.08


x/c=0.1075(main) x/c=0.4500(main)



• 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


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


x/c=0.8500(main) x/c=0.8982(flap)



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


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


x/c=1.0321(flap) x/c=1.1125(flap)


Conclusion• TransitionalDDESmethodologyestablishedandimplementedintotheOVERFLOW2.2nsolver• BasedonSA-neg turbulencemodelwithAFT2017btransitionmodel• Couplingstrategyextensibletoothertransitionmodels

• ConsistentimprovementinpredictionsforMD30P/30NtestcasewithtransitionalDDESoverfullyturbulentDDESandeithertransitionalorturbulentRANS• Bothintegratedloadsandvelocityprofiles

• Accuratepredictionofflaploadingappearstobemostcriticalfactorforthiscase


Acknowledgments

• ThismaterialisbaseduponworksupportedbytheNationalAeronauticsandSpaceAdministration(NASA)undercooperativeagreementawardnumberNNX17AJ95A(UniversityLeadershipInitiative)


Questions?

transitional delayed detached eddy simulation of ... · dr. jim coder assistant professor hector d....

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