LAVAContributiontoHiLiftPW-3
JamesJensen,MarieDenison,Gerrit Stich,JeffreyHousman,andCetinKiris
ComputationalAerosciences BranchNASAAmesResearchCenter
PID033
3rd HighLiftPredictionWorkshopDenver,COJune3-4,2017
Summaryofcasescompleted:- LAVA,OversetStructured,SA-QCR2000
Case Alpha=8,Fully turb,grid
study
Alpha=16,Fully turb,grid
study
1a(fullgap) yes yes
1c(partialseal) yes yes
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Case Polar, Fullyturb Polar,specifiedtransition
Polar,wtransitionprediction
2a (nonacelle) yes no no
2c (withnacelle) yes no no
- LAVA,UnstructuredPolyhedral,SACase Polar, Fullyturb Polar,specified
transitionPolar,wtransitionprediction
2c (withnacelle) yes no no
Case 2DVerificationstudy
3 yes
Launch Ascent and Vehicle Aerodynamics (LAVA) Framework
Far FieldAcoustic Solver
Structural Dynamics
ObjectOrientedFramework
DomainConnectivity/SharedDataC++/FortranwithMPIParallelism
LAVA
Multi-Physics:Multi-PhaseCombustionChemistryElectro-Magnetics……
6 DOF Body Motion
Post-ProcessingTools
Conjugate Heat Transfer
Other Solvers& Frameworks
Not Yet Connected
Connected Existing
Future3
Framework
Developing
Other Development Efforts• Higher order methods• Curvilinear grid generation• Wall modeling• LES/DES/ILES Turbulence• HEC (optimizations, accelerators,
etc) Kiris at al. AST-2016 and AIAA-2014-0070
Prismatic Layers
Structured Curvilinear
Navier-Stokes
Unstructured Arbitrary Polyhedral
Navier-Stokes
Structured Cartesian AMR
Navier-Stokes
LatticeBoltzmann
Actuator DiskModels
• High quality body fitted grids • Low computational cost• Reliable higher order methods
• Grid generation largely manual and time consuming
• Essentially no manual grid generation
• Highly efficient Structured • Adaptive Mesh Refinement (AMR)
• Low computational cost• Reliable higher order methods• Non-body fitted -> Resolution of boundary layers inefficient
• Partially automated grid generation
• Body fitted grids • Grid quality can be challenging• High computational cost• Higher order methods yet to fully mature
LAVA Computational Grid Paradigms
4
Structured Cartesian AMR
Unstructured Arbitrary Polyhedral
Structured Curvilinear
• 2nd order cell centered• MUSCL Scheme• AUSMPW+ convective flux function• BDF2 with GMRES linear solver (PETSc)• SA turbulence model
LAVA Solver Details
5
Unstructured Arbitrary Polyhedral Structured Curvilinear
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AllsimulationsarerunwithRANSusingcoldstartswithoutCFLramping
• 2nd order accurate Modified Roe Flux Difference Splitting for the convective terms
• 2nd order central differencing for the viscous terms
• SA turbulence model with QCR-2000 for viscous flux tensor
Briefoverviewofgridsystem(s)
OversetGridforCase2c 6
GridSystem Case(s) If committeegrid,reportanyproblems/issuesIfusergrid,reasonforgeneratinggridsystem
Committee(GridA,StructuredOverset) 1a and1c Observedsolutiondecouplinginunexpectedareasofthegrid
Committee(GridA,StructuredOverset) 2aand2c Usedcustom domainconnectivitywithcommitteegrids
User(UnstructuredPolyhedral) 2c Customgeneratedwithdifferentwakerefinements
UnstructuredGridforCase2c
ProvidedtheCommitteeOversetGridsforCase2aandCase2c• GeneratedwiththeChimeraGridTools(CGT)• Thegridwasgeneratedasamediumgridusingtheparametersfromthegriddingguidelinesdocumentprovidedbythecommittee
• Trailingedgehad25pointsinsteadofthe9specifiedinthedocument• Spanwise spacingattherootandtipofelementswasbasedonlocalcellsizes• Usedseparatewakemeshesratherthanaregionofuniformspacinginthevolumes
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Case2a
Case2c
ReasoningBehindWakeGrids
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WakeStreamlinesFinal“Geometric”WakeGrids
• Decidedtousea“geometric”basedwakegrid
• Originalplanwastogenerateanwakegridbasedonthestreamlines• Thestreamlinesvarygreatlywithangleofattacksothestreamlinebasedwakeswerenotgeneral
OversetStructuredandUnstructuredPolyhedralMeshParadigms• Closelookattheslat-wingjunction
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LAVAModifiedImplicitHoleCutting(MIHC)Procedure
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• FirsttheDCFroutinesinOVERFLOWareusedtoprovideaminimumholecutandensurethattherequirednumberoffringelayersareavailable(withminimumhole)fortheflowsolver(doublefringeinthiscase)
• Theglobalwall-distanceisalsocomputedandstoredtofile• NexttheMIHCcodeisappliedtotheoversetgridsystemwiththeminimumholescut
MinimumHole FinalHole
WakeGrids• Thedifferentconnectivitycodesincorporatedthewakegridsdifferently
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MIHCWakeGrids Peg5WakeGrids
WhatisSolutionDecoupling?
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• Somesolutiondecouplingisexpectedwithintheareasofoverlapbetweengridsbecausethesurfacepointsareslightlydifferent(notpointmatched)
• Thisdecouplingissomethingthatreducesasthemeshisrefined
Coarse
Medium Fine
HL-CRM(Case1)TopologyDifference
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• SawlargerthanexpectedsolutiondecouplingintheslatCp plots
• Firstsuspicionwasthatthesurfaceswerenotidenticalbuttheyweremadebysplittingonesurfacemesh
• Differentvolumegridgenerationmethods
• Leadstoadifferentamountofsolutiondecouplingatthegridinterfaces
HL-CRM(Case1a)GridConvergenceEffect
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• Liftisconvergingwellatbothanglesandhasconvergedtoanalmostidenticalvaluefrombothsolversatbothangles
• Dragisconvergedat⍺=8andisconvergingat⍺=16• Thesolversarewithin10dragcountsofeachotheratbothanglesofattack
JSM(Case2a)ForceandMomentComparisons
15
JSM(Case2a)Cp ComparisonsD-D
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• Atbothanglesofattacktheflapisfairlydifferentbetweenthetwosolvers
• At⍺=18.58° thedifferenceinthesolutionsattheflapbecomesevenmorepronounced
• OverflowappearstomatchthepeakbetterandLAVAappearstomatchbetterintherecoveryregion
JSM(Case2a)Cp ComparisonsG-G• Thedifferencesbetweenthesolversismorepronouncedatthisstation
• Atthehigherangleofattackthedifferencesbecomemorepronounced
• OntheflapLAVAisclosertotheexperimentatthepeakandOverflowiscloserattheTE
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JSM(Case2c)ForceandMomentComparisons
18
JSM(Case2c)Cp ComparisonsD-D
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• AtthelowerangleofattackOverflowismorecloselymatchingtheexperimentaldatabutatthehigherangleofattackLAVAmorecloselymatchestheexperiment
• OntheslatOverflowandtheLAVAUnstructuredresultareclosertotheexperimentatbothanglesofattack
JSM(Case2c)Cp ComparisonsG-G• Atthelowangleontheflapweseeasimilartrendasbefore;OverflowisclosertotheexperimentnearthepeakbutLAVAiscloserintherecoveryregion
• Atthehighangleofattackallofthesolvershavesimilarpredictions
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Summary• GeneratedthecommitteeoversetgridsystemfortheJSMmodel(used“geometric”wakegrids)
• ObservedsomeunexpectedsolutiondecouplinginCase1duetothewaythegridshadbeengenerated
• LAVAforceresultsagreedwellwiththeOverflowresultsforCase1
• TheCp andForceresultsaresimilarbetweenallofthesolversforbothCase2aandCase2c(flapisareaoflargestdifferences)
• NeedtoexploretheinfluenceoftheRCaswellastransitionmodels
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Acknowledgements• TransformationalToolsandTechnologies(T3)projectunderAeronauticsResearchMissionDirectorate(ARMD)
• NASfacilityforcomputertimeonPleiades
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