case 3 results verification exercise - nasacase 3 –2d airfoil near-wake verification 3 • study a...

CFD High Lift Prediction Workshop

Case3ResultsVerificationExercise

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compiledbytheHiLiftPW Committee

AIAAHiLiftPW-3- Denver,CO,USAJune3-4,2017


Overview• SourcesofdifferencesbetweenCFDresults(assuminguse

ofthecorrectgeometry):– Differentequations

• Thismaybeaduetounintentionalbugsinthesoftware• Oritmaybeonpurpose(e.g.,tweaktoaturbulencemodel)

– Useofdifferentboundaryconditions– Insufficientgridrefinement– VERIFICATION canhelpdiagnosethis

• Strongverification:methodofmanufacturedsolutions(MMS)• Weakverification:TurbulenceModelResource(TMR)website(https://turbmodels.larc.nasa.gov)

• Wewillshowyou:manyofthecodesusedinthisworkshophavenotbeenverified

• Wewillattempttolinkinconsistenciesintheverificationcasetoinconsistenciesinthelargehigh-liftcases

2AIAAHiLiftPW-3- Denver,CO,USAJune3-4,2017


Case3– 2DAirfoilNear-WakeVerification

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• Studyasimple2-Dcaseofnear-wakebehindDSMA661(MODELA)airfoil(J.FluidMech.(1985),Vol.160,pp.155-179)fromTMRwebsite

• CompareCFDresults that useostensibly thesame turbulence model toeach other• ForSAandSST,consistent results from2codes aretaken fromtheTMRwebsite• Results foragiven turbulence modelshould beconsistent as thegrid is refined

Notepossibleissue:farfield BCextentofonly20cmeansthatsolutiondifferencesmayoccurbecauseofnon-identicalfarfield BCimplementations



OverallresultsforCase3

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Red:SA-typemodelsGreen:SST-typemodelsBlue:Othermodels


LiftandDrag


OverallresultsforCase3

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Red:SA-typemodelsGreen:SST-typemodelsBlue:Othermodels


Minu-velocityinthewake


SAmodel



SA– referencesolutions



IdentifySAresultsthatareconsistent



PID Plot letter CL CD Velmin 1.01 Velmin 1.80 Overall001.1 A No No No No No003.2 C Y Y close No No004.1 D Y Y Y Y Y004.4 D close Y close Y close006.2 F Y Y Y Y Y007.1 G Y Y Y Y Y008.1 H Y close close Y close010.1 J close Y No Y No012.1 L Y Y (missing) (missing) Y015.1 O close close (missing) (missing) close016.2 P close close Y No No018.1 R No No No No No019.1 S No No No No No021.1 U Y No No No No022.2 V Y Y Y Y Y023.3 W Y Y Y Y Y026.1&3 Z close Y Y Y close026.2&4 Z Y Y Y Y Y030.5 b No No No No No033.2 f Y No No No No034.1 g close No No No No035.1 h No No No No No036.5 m Y Y No Y No 9AIAAHiLiftPW-3- Denver,CO,USAJune3-4,2017


OverallsummaryfortheSAmodel• SAresultsincludeSA,SA-neg,SA-noft2,andSA-QCR– NotincludingRorRCvariantshere

• Consistentwitheachother:– CFL3D,FUN3D,004.1,006.2,007.1,012.1,022.2,023.3,026.2/4…30%ofentries

• Fairly“close”,butnotfullyconsistent:– 004.4,008.1,015.1,026.1/3

• Not-so-close:– 001.1,003.2,010.1,016.2,018.1,019.1,021.1,030.5,033.2,034.1,035.1,036.5• Note:036.5wasconsistenton3outof4measures



Lookatconsistent SAresultsinwake



Cross-correlationwithHighLiftCases

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SAonly(therewerenotenoughresultsfromothermodelstodrawconclusions)

Note:someranCase3butdidnotrunhighliftcaseswiththesamemodel(only

plottingthosewhodid)



HL-CRM,alpha=8deg.

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AllSAResults

CL CD Cm



HL-CRM,alpha=8deg.

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AllSAResults

ResultscorrespondingwiththemostconsistentSAsolns fromCase3

CL CD Cm



HL-CRM,alpha=16deg.

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AllSAResults

CL CD Cm



HL-CRM,alpha=16deg.

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AllSAResults

CL CD Cm

ResultscorrespondingwiththemostconsistentSAsolns fromCase3



JSM,nonacelle/pylon

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AllSAResultsResultscorrespondingwiththemost

consistentSAsolns fromCase3

NoconsistencynearCL,max



Othermodels• SSTresults– Hadfarlesscontributions– Couldnot notetrendswithhigh-liftcases– ThreeresultswereconsistentwithCFL3D&FUN3Dcase3referencesolution:• 010.2,016.3,023.4• Others(003.1,020.3,025.1,030.6,036.6)wereclose,butlessconsistent– Note:020.3 usedSST+SAS,025.1 usedSST-V-sust,036.6 usedSST(mod)

• SSG/LRR-RSM-w2012– Twocontributors(onlyoneranhighliftcases)– 026.6 wasreasonablyconsistentwithCFL3D(026.5 wasoffonCL)

– 016.1 wasnotconsistentforumin atx/c=1.8



Conclusions

• SimilartopreviousverificationexercisesfrompastDPWsandHiLiftPWs:– Ifacodehasnotbeenverified,thenyoucannotexpecttogetconsistentsolutionswithothercodes

• Only30%ofparticipantswhoranCase3withSAwerefullyconsistent

• TakingthePIDsthatproducedthemostconsistentCase3results(withSA):– TheirSAresultsalsoweregenerallymoreconsistentforthetwoHL-CRMcases

– ButtheywerenotconsistentforJSMnearCL,max• nogridstudy



Backupslides



SampleiterativeconvergenceresultsforCase3

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(onfinegrid)



Definea“bandofacceptability”

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(ash->0)



FocusonSA(CL)

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Zoom:


FocusonSA(CD)

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Zoom:



FocusonSA(umin atx/c=1.01)

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Zoom:



FocusonSA(umin atx/c=1.80)

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Zoom:



OtherSA-relateditemsofnote

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• RorRCappearstolowerCL andCD somewhat(comparedtoSA),butthereisnotenoughconsistencyfromtheresultstoknowforsure




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• UseoflowMpreconditioningchangesresults




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• In026,aFarfield PointVortex(ffpv)wasrequiredtobringCL inlinewith“accepted”solutions• Reasonforthisisnotknown• Thereferencesolutionsdidnot useffpv

• Thenoft2optionhadasmalleffectondrag(reasonunknown)AIAAHiLiftPW-3- Denver,CO,USAJune3-4,2017



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• Adaptinggoestosameresultasstandardgridrefinement



LookatconsistentSAresultsinwake



SurfaceCp resultsforCase3

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Surfacepressurecoefficientsdonottellustoomuch



Velocityprofiles



Turbulentshearstressprofiles



SSTmodel



FocusonSST(CL)



FocusonSST(CD)



FocusonSST(umin atx/c=1.01)



FocusonSST(umin atx/c=1.80)



SSTmodelsfromcase1a


alpha=8deg. alpha=16deg.


SSG/LRR-RSMmodel



FocusonRSM(CL)

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CFL3Dwasrunforcomparisontothe2submittedresults



FocusonRSM(CD)



FocusonRSM(umin atx/c=1.01)



FocusonRSM(umin atx/c=1.80)


case 3 results verification exercise - nasacase 3 –2d airfoil near-wake verification 3 • study a...

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