Towards Industrial LES/DNS in Aeronau7cs Paving the … · Towards Industrial LES/DNS in Aeronau7cs Paving the Way for Future Accurate CFD ... • The TILDA project • Expected outcome

TowardsIndustrialLES/DNSinAeronau7csPavingtheWayforFutureAccurateCFD

CharlesHirschPresident,NUMECAInt.

2©NUMECAInt.–Allrightsreserved

•  CurrentCFDlimita@ons

•  ThevisionsoffutureCFD

•  TheTILDAproject

•  ExpectedoutcomeforIndustry

Content

07/06/2017 AIAAAvia@onForum--TILDALES/DNSSession


•  CFDhasprogressedconsiderablyinthelast50years,duetoalgorithmicdevelopmentsandgrowingcapaci@esincomputerhardwareandHPC

•  Thecurrentindustrialprac@cereliesessen@allyonRANSmodeling,despitethestronglimita@onsofpresentdayturbulence(andtransi@on)modelling

•  TheuseofCFDhasremainedconfinedtoasmallregionoftheopera@ngdesignspaceduetotheinabilityofcurrentmethodstoreliablypredictturbulentseparatedflows

CurrentCFDcapabili@esandlimita@ons

Flight envelopes and level of confidence in CFD solutions - given by colour gradient (Courtesy: Airbus, A. Abbas (2012))

07/06/2017 AIAAAvia@onForum--TILDALES/DNSSession ©NUMECAInt.–Allrightsreserved


CurrentLimita@onsofCFDinAeronau@cs



•  ThereisastrongneedtomovebeyondRANSbasedmodelingandovercomethelimita@onsofturbulencemodels,bymovingtowardsLES/DNSlevelsofsimula@ons

•  HybridRANS-LESandwall-modeledLESofferatemporaryintermediateop@on,althoughsignificantmodelingissuesremaintobeaddressedhereaswell

•  Toachieveahigherlevelofpredic7vereliability,weneedtoreducethelevelofempiricism

•  AgrowingnumberofLES/DNSsimula@onswithfinemeshresolu@onshavebeenproducedinrecentyears,mainlyonbasicsimplifiedconfigura@ons

•  WhatistheroadtowardsfullLES/DNScapabili7esatanindustriallevelin

Aeronau7cs?

Howcanweovercometheselimita@ons



Thevisionsfornextgenera7onCFDTwointeres@ngoverviewsofthefutureofCFDhavebeenprovidedrecentlyby

–  NASAvisionCFD-2030(2014)–  P.Spalart(2012)andP.SpalartandV.Venkatakrishnan(Aeronau@cal

Journal2016)Plusthe

–  TILDAVision(2014)Canbeclassifiedas

–  Realis@c:NASAvisionCFD-2030–  Pessimis@c:P.SpalartandV.Venkatakrishnan(2016)–  Op@mis@c:TILDAvision

CFDFutureVisions



NASAVisionCFD-2030



SpalartFutureCFDVision(2012)


•  Webelievethises@ma@ontobetoopessimis@c!

•  Itisbasedonstandardsecondorderschemes

•  HOM’sandHPCoffernewopportuni@es,whichcanbelargelyexploited


FromP.SpalartandV.Venkatakrishnan(2016)–  WebelievethereisatendencytowardsoverconfidenceinCFDinsome

circles,eventotheextentofignoringwell-knownsourcesoferror,whichcreatesariskofbacklash,wereCFDtobeblamedforcostlymistakes.

•  WenowsummarizeourpredicBonsforturbulencetreatmentattheReynoldsnumbersofinterest–  DNSandwall-resolvedLESwillnotbeused.Thechallengesin

physicalmodellingoftransi>onandturbulencewillnotbetrulyovercomeinthiscentury(!!?)

–  PureRANScannotbefullyeliminated,butisnottobetrustedaDermassivesepara>on,andul>matelynoteveninboundarylayersinstrongadversepressuregradients.

–  TheswitchfromRANStoWMLESwillnothappenglobally,butinstead,hybridsimulaBonswillseetheboundarymoveforwardtograduallyshrinktheRANSregion,reducingittothethinnestareasofboundarylayers,whicharetheleastdifficulttopredictbutcannotbeignored.

SpalartFutureCFDVision(2016)



Thesees@matesdonottakeintoaccountthepoten@alofferedby:•  HighOrderMethods•  AdvancesinHPCandtheincreasingcapaci@esofnew

mul@core-mul@threadarchitectures•  Thepoten@aladd-onsfrommul@pleGPU’sinfrastructures•  AdvancementsinLES/DNSmethodologies,throughimproved

algorithmicdevelopments,suchas–  Mul@level,mul@scalemethodologies–  Op@malcombina@onsofexplicitandimplicitmethods

Withapoten@algainof3to4ordersofmagnitude!!

TheTILDAVision



HighOrderMethods(HOM)


•  CurrentCFDcodesarenominallyofsecondorder–  ValidstrictlyonCartesiangrids–  Onunstructuredgridsthereisagenerallossofaccuracyduetoirregularcellshape

andsizes

•  Highordermethods(HOM)onunstructuredgrids–  Uptounlimitedorderofaccuracy–  Keepstheaccuracyineachcellsincetheorderisdefinedbythepowerofthe

polynomialrepresenta@onineachcell–  Provideshighlyaccuratesolu@onsoncoarsegrids–  Variousmethodsareavailableandinfurtherdevelopment,towardshigherlevels

ofmaturity:•  Discon@nuousGalerkin•  SpectralDifferences•  FluxReconstruc@on


•  Necessityforcurvedmeshesatboundaries•  Moreefficient@meintegra@onmethods•  Futurepoten@al

–  FromtheIDIHOMprojectitappearsthatHOMisnotyetcompe@@vecomparedtocurrentefficientfinitevolumeCFDcodes,forsteadyRANS

–  Butroomiss@llavailableforperformanceimprovements

•  However,HOM’sarehighlycompe@@veforunsteadyflows,inpar@cularforCAAandLES/DNS

Challenges of HOM



TheTILDAProject

Mainobjec7vesoftheTILDAproject(CoordinatedbyNUMECA)Quan7ta7veObjec7ve:•  Runa1-10BillionDoFforLES/DNSon50,000+coresin1day;thatisfora

costof1to1.5MCPU-h•  Evolu7onofHPCpowerinIndustry

Thisgoalcanbemetbyintroducing:--Efficienthigh-ordermethods(HOM),whichoffertherequestedaccuracyoncoarserunstructuredmeshesandhavethepoten@altomakefullyresolvedsimula@ons(LES,butalsoDNS)feasibleforindustry.--NewmethodologiesforLES/DNS,basedonmul@level,mul@-resolu@on,adap@veandothermethods--Exploitmassiveparallelism,includingmul@-coreandmul@-threadedhardware

Evaluation of HPC, i.e. number of cores vs. years used/in use and extrapolated to the end of TILDA



PathtoIndustrialLES/DNS


●  Improvements in single thread performance has slowed, but not completely flattened

●  Continued increases in the number of cores per

processor and energy efficient accelerators mean Moore’s Law will hold into the near future (~2020-2025)

●  Harnessing the power of future systems will

require software that map well onto heterogeneous, high-FLOPs, low memory bandwidth hardware

●  High order solvers are demonstrated to

efficiently utilize current leadership systems at scale[2] ○  Piz-Daint system: ~10 PF ○  PyFR: 45% of peak system utilization

●  The current path points to exascale systems

deployed by 2025, providing 100X more FLOPs for industrial LES

[1]hmps://www.karlrupp.net/2015/06/40-years-of-microprocessor-trend-data/[2]hmps://www.nas.nasa.gov/assets/pdf/ams/2016/AMS_20160531_Witherden-Vincent.pdf[3]hmps://[email protected]/wordpress/wp-content/uploads/2015/09/[email protected]


•  Budget:around3M€,foraperiodofthreeyears

•  NUMECAInt.(Belgium)•  DLR(Germany)•  ONERA(France)•  DassaultAvia@on(France)•  SAFRAN(France)•  CERFACS(France)•  CENAERO(Belgium)•  Univ.CatholiquedeLouvain-UCL(Belgium)•  Univ.Bergamo(Italy)•  ImperialCollege(UK)•  TsAGI(Russia)

AssociatedPartners•  Airbus•  MTU(Germany)•  NASAGlenn–HTHuynh(USA)

TILDABudgetandPartners



Thetechnicalobjec@vesforbringingLESandfutureDNSclosertoindustrialapplica@onsinthemid-term,requireinnova@vedevelopments,ensuringfutureCFDapproachestoofferconfidenceandreliabilitycombinedwithaccuracyanduser-friendliness.HenceintheTILDAprojecttheobjec@vesread:•  AdvancemethodstoaccelerateHOMforunsteadysimula>onsofLESandfuture

DNSonunstructuredgrids.•  AdvancemethodstoaccelerateLESandfutureDNSmethodologybymul@level,

adap@ve,fractalandsimilarapproachesonunstructuredgrids.•  ExtendLES/DNStoindustriallyrelevantapplica@onsusingHOMsonunstructured

gridsforunsteadyflowsaimingatareduc@onof2-3ordersofmagnitudeinCPU>me,togetherwiththeuseoftheinnova@veresearchonLESwithrespecttoadap@vityandmul@levelusewithanaddi>onalpoten>algainof1-2ordersofmagnitude.

•  Providegridgenera>onmethodsforHOMonunstructuredgrids,withemphasisonvalidcurvilinearmeshesforcomplexgeometriesincludingboundarylayerandhybridmeshes,whileaccoun>ngforbothmeshandsolu>onquality.

•  Moreover,keepafocusonlargescalecomputa@onswithefficientmeshgenera@onalgorithmsandparalleladapta@on,aswellasperformance-orientedload-balancingandpar@@oningstrategies.

TILDAObjec@ves



TILDAWorkPackages



TILDATESTCASES



TILDATESTCASES


©NUMECAInt.–Allrightsreserved

Arepresenta@veexampleofTILDAAchievements

•  FromP.Vincentetal,ImperialCollege,2016

•  22.5BillionDoF,•  Order4,•  on5000GPUin35

Hours,onTITAN

NUMECAIngBuroUserMee@ng2017-Nurnberg 2025/04/2017


•  Predic@onofextendedFlightEnvelope,whichhavethepoten@altochangethewayindustryusesCFDinthedesignprocess,–  byensuringhighlyreliabledata,insupportofthedesigndecisionprocess,witha

turnaround@meof1day•  Enhancedunderstandingoftheunderlyingphysics•  Thegenera@onofrepresenta@veLES/DNSdatabasesshouldprovidea

frameworkforimprovementsofTurbulenceandTransi@onmodelsforRANSsimula@ons–  Thesesimula@onsprovideaneverseenbeforeamountoffullydetaileddatato

inves@gateallthecontribu@onsto,e.g.k;e;Reynoldsstresses,……,–  Andcomparewithexis@ngmodels–  Andimprovethemodels

•  ThisopensalargeroadtowardsmorereliableRANSmodels,aswellasmorereliablesubgridscalemodelsforWMLES

Expectedoutcomeforindustry



AnImprovedEARSMModel,basedonextensiveLES/DNSdata


•  Separa7onSensi7veCorrectedExplicitAlgebraicReynoldsStressModel(SSC-EARSM)S.Monté,L.Temmerman,B.Léonard,B.TarBnville,C.Hirsch,ETMM11(2016)

•  TheSSC-EARSMisdesignedwiththeaimofbemerpredic@ngseparatedflows.

•  ItisconstructedontheSBSL-EARSMmodelofMenteretal.(2012),Jakirlicetal(2015)inwhichthreecorrec@onsareintroducedbasedoniden@fiedweaknessesoftheoriginalmodel.

•  Basedonsystema7ccomparisonswithLESandDNSdatabases,comparingdatasuchasshearstressandkine7cturbulentenergydistribu7ons

•  Themodifica7onshavebeendesignedtobederpredictthekine7cenergyproduc7on,andtheshearstress,acrossthesepara7onbubble

Turbulentkine@cenergyintheseparatedbubbleofthecurvedbackwardfacingstep.Squares:LESofBentalebetal.(2011).Red:theSBSL-EARSMmodel.Blue:theSSC-EARSMmodel

LES

SBSL-EARSM

SSC-EARSM


SSC-EARSMTurbulenceModel


•  Thedevelopmentandtheextensivetes@ngoftheSSC-EARSMmodelindicatethatmajorweaknessesoftheSBSL-EARSMmodel,whicharecommontomostRANSmodels,canbeaddressed

•  Thedevelopmentofthemodelwasbasedonalargenumberofreferencedata,suchasthecurvedbackwardfacingstepofBentalebetal.(2011),theperiodichill,DNSdatafortheflatplate,………

•  TheoutcomeisthattheSSC-EARSMmodelbemerresolvesseparatedflows,includingmorecomplexseparatedflowssuchasthe

–  TrapwingofHLPW-1–  DrivAercarmodelsofHeretal.(2012)–  CRMmodelofDPW-4

TurbulentkineBcenergyk/Uτ^2overaturbulentflatplateatReθ=2,540.Redsolidline:theSBSL-EARSMmodel.Cyansolidline:theSSC-EARSMmodelDots:DNSdatafromP.Schla\er(KTH).


TrapWingofHLPW-1



SSC-EARSMTurbulenceModel-industrialapplica@on


Exp SBSL-EARSM SSC-EARSM

Fastback

Pressurecoefficientandskinfric@onovertheDrivAercargeometries.


SSC-EARSMTurbulenceModel--Dragpredic@on



CRMModelforNASAandJAXADragpredic@on


AIAADPW4●  NASACommonResearchModelinitsWing-Body-Tailconfigura@on●  Representa@veofcontemporarytransonictransportaircrar●  Wingprofiledesignedforthepurposesofresearchanddevelopment:

○  Strongadversepressuregradientoverthelast10%-15%oflocalchord○  Promotesepara@onofboundarylayertoamplifyeffectofturbulence

model●  ExperimentaldatafromNASAAmes11rtransonicwindtunnelandfrom

JAXA,takingintoaccountelas@cdeforma@on


•  UnstructuredgridfromJAXA•  Solver:FINE™/OpenfromNUMECAwithSSC-EARSMmodel

JAXAgridsandexperimentaldata


29©NUMECAInt.–Allrightsreserved07/06/2017 AIAAAvia@onForum--TILDALES/DNSSession

JAXAgridsandexperimentaldata:CL-Alpha

DatafromJAXAAPC-1Workshop


JAXAgridsandexperimentaldata:Polar




JAXAgridsandexperimentaldata:CM-Alpha




•  TheTILDAprojectsisac@veun@lNovember2018•  A“TILDA”Symposiumisplanned,byNovember2018:

HighFidelityLES/DNSforIndustrialApplica7ons

•  Expectedtoini@ateanewdedicatedbi-annualseriesofconferences,coveringa.o.

–  ImprovementsinHOMandgridgenera7onforLES/DNS–  Industrialrelevantapplica7ons–  Understandingofthefundamentalsofturbulenceandtransi7on–  Exploita7ontowardsimprovementofWMLES,RANSandtransi7onmodeling

•  Willbeorganizedbythenewlyformed“AerospaceEurope”community,composedbythemajorEUscien@ficandindustrialAeronau@calAssocia@ons:

–  CEAS,ECCOMAS,EUROMECH,ERCOFTAC,EUROTURBO,EUCASS–  AnAssocia@onwithAIAAisunderconsidera@on

Next



•  Variouspresenta@onstofollowwillpresentsomeofthecurrentprogresswithintheTILDAproject

•  Manyissuesaboutthesmallscalenear-walltreatmentaretobeinves@gated

•  Itisexpectedtoallow,inthenearfuture,extensiveHOMsimula@onsforfullyresolvedLES/DNSwithhighresolu@onatincreasingRe-numbers.

Conclusions



Thankyouforyouramen@on


Documents

Towards Industrial LES/DNS in Aeronau7cs Paving the … · Towards Industrial LES/DNS in Aeronau7cs Paving the Way for Future Accurate CFD ... • The TILDA project • Expected outcome