hpcmo reno02 - Cobalt Solutions, LLC

1 AIAA 2002 1021 Progress on Detached-EddySimulation of Massively SeparatedFlowsKyle D. SquiresMAE Department, Arizona State UniversityJames R. Forsythe and Scott A. MortonDept. of Aeronautics, USAF AcademyWilliam Z. Strang, Kenneth E. Wurtzler, and Robert Solution, LLCM atthew J. GrismerAir Force Research LaboratoryPhilippe R. SpalartBoeing Commercial AirplanesAerospace Sciences Meeting 200214 18 January 2002 / Reno, NevadaFor permission to copy or republish, contact the American Institute of Aeronautics and Astronautics1801 Alexander Bell Drive, Suite 500, Reston, VA 20191 MAED epartment, , , {, , ,Spalartetal.}

2 [2]proposedDetached-EddySimulation(DES) ,combiningReynolds-averagedNavierStokes( RANS)andLargeEddySimulation(LES).DEScomb inesthee ,moreunsteady ,\AnalysisofFullAircraftwithMassiveSepar ationUsingDetached-EddySimulation".Numer ous owsareexamined,includingacylinder,two-an dthree-dimensionalforebodies,aprolatesph eroid,asupersonicbase ow,adeltawing,anotionaltruck,theC130,the F-16, owsolver{ Cobalt {whichusesMessagePassingI nterface(MPI) ,solutionsareobtainedonasmanyas512proces sors,providingfullaircraft, ow eldsencounteredinDoDap-plicationsoccurwi thinandaroundcomplexde-vicesandatspeedsf orwhichtheunderlyingstateofthe (CFD)}}

3 Isgainingincreasedpromi-nenceasausefulap proachtoanalyzeandultimatelydesigncon gurations,e cientandaccuratesolutionsrequiresubstant iale ,numericalsolutionoftheNavier-Stokesequa tions,ande cient Professor,MemberofAIAAyAssistantProfesso r,MemberofAIAAzAssociateProfessor,Associ ateFellowofAIAAxPresident,MemberofAIAA{V icePresident,MemberofAIAAkVicePresident, MemberofAIAA Engineer, ,CFDhasremainedlimitedasareliabletoolfor predictionofinherentlyunsteady owsat owsarebasedonsolutionoftheReynolds-avera gedNavier-Stokes(RANS) owswithnoregionsofreversed ow,orpossiblyexhibitingshallowseparation s,itappearsinevitablethatRANS turbulencemodelsareunabletoaccuratelypre dictphenomenadominating ,arguably,arewhatdefeatsRANStur-bulencem odels, {1021 Toovercomethede cienciesofRANS modelsforpredictingmassivelyseparated ows,Spalartetal.}}

4 [2]proposedDetached-EddySimulation(DES)w iththeobjectiveofdevelopinganumericallyf easibleandaccurateapproachcombiningthemo stfavor-ableelementsofRANS modelsandLargeEddySim-ulation(LES).Thepr imaryadvantageofDESisthatitcanbeapplieda thighReynoldsnumbersascanReynolds-averag edtechniques,butalsoresolvesgeometry-dep endent, owsincomplexcon gurations, (DoD)Chal-lengeprojectbytheHighPerforman ceComputingModernizationO ce( hpcmo ), rstyeare ortontheChallengeproject{\AnalysisofFull AircraftwithMassiveSeparationUsingDetach ed-EddySimulation".Duetothelargescopeoft heproject,onlybriefsummariesofthevar-iou scalculationsthathavebeenundertakenwillb eprovided, ortisCobalt60(Strangetal.)}

5 [6]) {acompressible owsolverdevelopedattheAirForceResearchLa boratoryinsupportoftheCom-monHighPerform anceSoftwareSupportInitiative(CHSSI).The relevantimprovementsavailableinthecommer cialversionandcentraltothesuccessofthisp roposalarerigidbodymotion,fasterper-iter ationtimes,theinclusionofSST-basedDES,im provedtrip-ping,abilitytocalculatetime-a veragesandturbulentstatistics,animproved spatialoperator, [6]validatedthecodeonanumberofproblems,i ncludingtheSpalart-Allmarasmodel(whichfo rmsthecoreoftheDESmodel).Tomaroetal.[7]c onvertedCobalt60fromexplicittoimplicitti meintegration, [8]thenparallelizedthecode, [5] [9],Karypisetal.}

6 [10] (SA)one-equationmodel[12]solvesasinglepa rtialdi erentialequationforavari-ablee erentialequationisderivedby\usingempiric ismandargumentsofdimensionalanalysis,Gal ileanin-varianceandselecteddependenceont hemolecularviscosity."[1]Themodelinclude sawalldestructiontermthatreducestheturbu lentviscosityintheloglayerandlaminarsubl ayerandtriptermsthatpro-videsasmoothtran sitionfromlaminartoturbulent , ,atransportequationisusedtocomputeaworki ngvariableusedtoformtheturbulenteddyvisc osity,De Dt=cb1[1 ft2]eSe hcw1fw cb1 2ft2i e d 2+1 hr (( +e )re )+cb2(re )2i;+ft1 U2;(1)wheree tisobtainedfrom, t=e fv1;fv1= 3 3+c3v1; e ;(2)where ,eS fv3S+e 2d2fv2;(3)fv2= 1+ cv2 3;(4)fv3=(1+ fv1)(1 fv2).

7 (5) (3)di ersfromthatdevelopedinSpalartandAllmaras [12]viatheintroductionoffv3andre-de owsandhavetheadvantagethatforsimulationo f owswithlaminarseparation,spuriousupstrea mpropagationoftheeddyviscosityintoattach ed, cationwascrucialforsuccessfulsimulationo fthe ,fw=g 1+c6w3g6+c6w3 ;1=6g=r+cw2(r6 r);r e eS 2d2:(6)Thefunctionft2isde nedas,ft2=ct3exp( ct4 2):(7)2of9 AmericanInstituteofAeronauticsandAstrona uticsPaper2002{1021 Thetripfunctionft1isspeci edintermsofthedis-tancedtfromthe eldpointtothetrip,thewallvorticity!tatth etrip,and Uwhichisthedi er-encebetweenthevelocityatthe eldpointandthatatthetrip,ft1=ct1gtexp ct2!}

8 2t U2 d2+g2td2t ;(8)wheregt=min(0:1; U=!t x)and :1355, =2=3,cb2=0:622, =0:41,cw1=cb1= 2+(1+cb2)= ,cw2=0:3,cw3=2,cv1=7:1,cv2=5,ct1=1,ct2=2 ,ct3=1:1,andct4= cationtotheSpalart-AllmarasRANS model[12]suchthatthemodelreducestoitsRAN S formulationnearsolidsur-facesandtoasubgr idmodelawayfromthewall[2]. ,d,byed,whereedisde nedas,ed min(d;CDES ):(9)InEqn.(9),forthecomputationsperform edinthisproject, isthelargestdistancebetweenthecellcenter underconsiderationandthecellcenterofthen eighbors( ,thosecellssharingafacewiththecellinques tion).In\natural"applicationsofDES,thewa ll-parallelgridspacings( ,streamwiseandspanwise)areatleastontheor deroftheboundarylayerthick-nessandtheS-A RANS modelisretainedthroughouttheboundarylaye r, ,ed= ,pre-dictionofboundarylayerseparationisd eterminedinthe`RANS mode' , ,thelengthscaleed=CDES intheLESregionyieldsaSmagorinskyeddyvisc ositye /S ,theroleof istoallowtheenergycascadedowntothegridsi ze;roughly,itmakesthepseudo-Kolmogorovle ngthscale,basedontheeddyviscosity, :65wassetinhomogeneousturbulence[3].

9 Strelets[4]introducedaDESmodelbasedonMen ter'sShearStressTransportmodel[13] owsthathavebeencomputedduringthe ,assessment,andimprovementofarelativelyn ewcomputationaltechniqueforpredictingtur bulent owssuchasDetached-EddySimulationisthebui ldingofanexperiencebasethatcanbeusedtopr ovideinsightandexperienceusefulforaddres singpotentialprob-lemsandguidingthesucce ssoffuturee ortsasthemethodisappliedtonewcon owssummarizedbelowpossesseselementsthath avebeenvaluableinadvanc-ingthecomputatio nalapproachandimprovingDEScapabilitiesfo rengineeringandscienti ,takingadvantageofthereasonablerangeof owsexperiencingturbulentboundarylayersep arationareoutofreachofwhole-domainLESsin cetheboundarylayerneedstoberesolved,rath erthanmodelledifthenear-wall owsand,consequently,DESo owoverasectionofacircularcylinderatasupe r-critical(tur-bulentboundarylayersepara tion) (S-A) ,three-dimensionalstructuresquickly owoveracircularcylinderatRe=800.

10 {1021 RoundedSquareOneofthemostsigni cantfactorsa ectingspincharacteristicsformodern ghtersistheforebody,withitscomplexvortic al \building-block" owconsideredaspartoftheChallengeprojecti sthataroundacanon-icalforebodycrosssecti on, [11]haveshownthatthehighReynoldsnumberDE Spredictionsofthe owoverarounded-cornersquareatRe=800; owovera70 deltawinghasbeencomputedataReynoldsnumbe rof1:56 106[14].Inthisef-fort,akey ndingwasthattheRANS model(S-A)wasabletoaccuratelypredictthes econdarysepara-tion, ,withDESgivingamorerealisticpre-dictiono fthe ,infact, [15]waspredictedusingDESandcomparedtoLES andRANS results[16].}