Fluent优化技术培训

ANSYSFLUENT优化技术培训,姓名：宋述军公司：安世亚太科技（北京）有限公司,Preface,ThereleaseoftheadjointsolverinFluent13istheculminationofseveralyearsofR&Deffort.Thisprojectwasrisky,buttherewardsaregreatbothforANSYSanditsclients.Therewereanumberoffalsestartsanddead-ends.Writinganadjointsolverthatmeetstheneedsoftheengineeringcommunityisnotatrivialtask.Wearepleasedtohavecomesofar,andlookforwardtogoingmuchfurther.,KeyIdeas-Fundamentals,KeyIdeas-Fundamentals,FLOWSOLVER,High-level“system”viewofaconventionalflowsolver,HowarechangestoKEYOUTPUTSDEPENDENTonchangestotheINputs?,KeyIdeas-Fundamentals,Flowsolutionq,andtheinputstotheproblemc.,Output,ResidualsoftheNavier-Stokesequations,LinearizedNavier-Stokes,EngineeraparticularlinearcombinationoflinearizedNSequationsintroducemultipliers,Topleveladjointsolveralgorithmquasi-NewtonschemeSolveusingAMGInvolvesafamiliarprocessSolutionadvancementcontrolsCourantnumber,under-relaxationResiduals&iterationsRoughlythesameeffortasaconventionalflowsolution,KeyIdeasAdjointEquations,Thisinnocent-lookingsystemofequationsisattheheartoftheadjointsolver.,Constructandsolveanadjointproblemtogetahelpersolution,Approximatelinearizationwithpseudo-timestepintroduced.Similartooriginalflowsolver,buttransposed.,Updatetotheadjointsolution,SystemJacobian(transposed),Derivativeofachosenobservablewithrespecttotheflowsolution,KeyIdeas-Workflow,KeyIdeasShapeSensitivity,Shapesensitivity:Sensitivityoftheobservedvaluewithrespectto(boundary)gridnodelocations,DragsensitivityforNACA0012,KeyIdeasGradientAlgorithm&Optimization,Firstorderestimateofthechange,KeyIdeasMeshMorphing,Flow,KeyIdeasMeshMoprhing,Actualchange3.1DP=-213.8Totalimprovementof8%,KeyIdeasMeshAdaptation,AdjointsolutionDragsensitivity,BaselineMesh,AdaptedMesh,AdaptedMeshDetail,KeyIdeas,Usage,TheadjointsolverisabetaaddonfeaturetobereleasedwithallFluent13packages.Documentationwillbeavailableonlineviatheuserservicescenter.TheoryUsageTutorialCasestudyFunctionalityisactivatedbyEnablingbetafeatures.LoadingtheadjointsolveraddonmoduleAnewmenuitemisaddedatthetoplevel.TUIentriesunderadjoint,Usage-Overview,/adjointcontrolsmorphing/reporting/monitors/observable/run/,GUIFollowascloseaspossiblesamedesignlayoutasFluentsolverSpecifyobservableAdjointsolutionadvancementcontrolsResidualmonitorsInitializationanditerationPost-processing:contours,vectors.ResultsreportingMesh-morphingwithpre-calculationofexpectedchangeinobservable.,Usage-Overview,Usage-Overview,ANSYS-FluentflowsolverhasverybroadscopeAdjointisconfiguredtocomputesolutionsbasedonsomeassumptionsSteady,incompressible,laminarflow.Steady,incompressible,turbulentflowwithstandardwallfunctions.First-orderdiscretizationinspace.Frozenturbulence.TheprimaryflowsolutiondoesNOTneedtoberunwiththeserestrictionsStrongevidencethattheseassumptionsdonotunderminetheutilityoftheadjointsolutiondataforengineeringpurposes.Fullyparallelized.GradientalgorithmforshapemodificationMeshmorphingusingcontrolpoints.Adjoint-basedsolutionadaption,Usage-Overview,ModellimitationsNoporousmediaNoMRFNocompressibilityNoheattransferTwotypesofmodeling-relatedmessagesmaybeprintedintheconsoleProvidesdetailsofthedifferencesbetweenhowtheadjointsolverimplementationistreatingtheproblemincomparisontotheconventionalflowsolver.WarningDifferenceisnotfatal.Adjointsolvercanexecute.Maydetractfromqualityofadjointresults.ErrorModelsusedintheconventionalsolverareincompatiblewiththeadjointsolver.Adjointsolvercannotberun.,Usage-flowaroundcylinder,Contoursofvelocitymagnitude,Contoursofvelocitymagnitude,TUIdefine/models/addon-moduleFLUENTAddonModules:0.None1.MHDModel2.FiberModel3.FuelCellandElectrolysisModel4.SOFCModelwithUnresolvedElectrolyte5.PopulationBalanceModel6.AdjointSolverEnterModuleNumber:06,Usage-Observables,Availableobservables,Forceinspecifieddirection,Directioninwhichforceistoberesolved,Contributingwalls,Observabletypeselection,Writevalueofobservabletofile,Printvalueofobservableinconsole,Totalpressuredrop,InitializingDiscreteAdjointSolver.Done.Observedvalue=1.337968765e+03(n),Usage-Controls,SolutionAdvancementControls,Courantnumber:SmallervaluestabilizesinnerAMGiterations,butresultsinmoreouteriterations.,Enablepreconditioning.Usuallyrequiredforturbulentflowproblems.,Artificialcompressibility:LargervaluestabilizesinnerAMGiterations,butresultsinmoreouteriterations.,Stabilizationfactor:Increasethisvaluetostabilizethecalculationinregionsofstrongshear.Alargervalueimpliesalessaccurateadjointsolution.,Under-Relaxationfactors:Thesefactorsplaythesameroleastheconventionalflowsolverunder-relaxationfactors.,ToleranceforconvergenceoftheinnerAMGiterations,MaximumnumberofAMGiterationstobeattempted,PrinttheresidualsoftheAMGiterationsintheconsole.Usedtoverifythattheinneriterationsareconverging.,Usage-Monitors,Residualmonitorsandconvergencecriteria,Defineconvergencecriteriaforadjointequations,Whetherornotanequationistobecheckedforconvergence,Samebehaviorasconventionalflowsolver,Residualsplottedinspecifiedwindow,Usage-Iterating,Initialization&Iteration,Initializetheadjointsolutionfieldtozeroeverywhere,Maximumnumberofiterationstobeperformed,Starttheiterationcyclefortheadjointsolver,UsageSolutionstrategy,SolutionAdvancementGuidelinesLargerturbulentproblemswillrequirepreconditioningStartwithCourantnumberof5.Artificialcompressibilityof0.25.Showinneriterationsforalgebraicmultigrid.PerformacoupleofiterationsandensurethatAMGisconverging.Idealscenario:5-10iterations.IfmorethanthisisrequiredthentheCourantnumbershouldbereduced.Iftheinneriterationsconvergeinfewerthan4iterationsthentheCourantnumbermaybeincreasedtoimprovetherateofconvergenceoftheouteriterations.Notethattheouteriterationscanstilldivergeeventhoughtheinneriterationsconverge.Theouteriterationswillneverconvergeiftheinneriterationsdiverge!ProblemswithstrongshearrequirestabilizationIftheouteriterationsdivergewhiletheinneriterationsconvergetryreducingtheCourantnumberand/ortheunder-relaxationfactors.Increasingthestabilizationfactorcanalsostabilizetheouteriterations.(Itcanalsoaidinstabilizinginneriterations)Avalueof1orlessispreferredforstabilization,butnotessential.Thelargerthestabilizationfactorthelessaccuratetheadjointsolutionwillbe.Iftheprimaryflowisclosetobeingunsteadythentheadjointsolverislikelytohavedifficultyconverging.KeysettingsCourantnumberStabilization,Usage-Reporting,Reportingofboundaryconditionsensitivity,Printthereportintheconsolewindow,Write/appendthereporttoafile,Boundaryforwhichareportistoberequested,Velocityinletid5Velocitymagnitude=4.000000000e+01(m/s),Sensitivity=5.429127866e+01(n)/(m/s),Examplereport:,UsageContours&Vectors,ContoursAdjointvelocitycomponentsAdjointpressure,VectorsControlsensitivityShapesensitivityAdjointvelocity,Shapesensitivitycoloredbyadjointpressure,AdjointPressureContours,AdjointX-VelocityContours,UsageContours&Vectors,InterpretingtheadjointsolutionfieldsTheadjointsolutiondatasetisveryrich.Offersdetailedguidanceonhowfactorsthatareexternaltothesystemaffectthequantityofinterest.Adjointvelocityeffectofsources/sinksofmomentum.Largeadjointvelocityimpliesthattheintroductionofabodyforceinthefluidatthatlocationwillhaveastrongimpactonthequantityofinterest.Adjointpressureeffectofsources/sinksofmass.Adjointpressureonaboundaryshowseffectofblowing/suction(e.g.bleedair).,Usage-Morphing,Definingtheregiontobemorphed,Selectthewallsthataretobepermittedtomove.Surfacesthatarenotselectedthatintersectthecontrolvolumewillremainfixed.,Drawsaboundingboxaroundtheselectedsurfaces,Enlargethecontrolvolume,Shrinkthecontrolvolume,Updatesthecontrolpointsensitivities.Mustbedoneanytimethecontrolvolumedefinitionchanges.,Explicitboundsofthecontrolvolume,Numberofcontrolpointsineachcoordinatedirection,Orderofcontinuityatedgeofcontrolvolume,Visibilityoftheboundingbox,HandlingofSymmetryplanes,Usage-Morphing,Computingtheexpectedchangeandmodifyingthemesh,AftertheupdateoperationtheUpdatebuttonisgrayedoutuntilthecontrolvolumeismodified,Scalefactorforthemorphing,Printtheexpectedchangetotheconsolewindow,Write/appendtheexpectedchangetoafile,Updatingcontrolpointlocationsandsensitivities.Done.Expectedchangeinobservableduetomorphing:-4.466302281e+01(n),Modifythemesh,ExampleReportofexpectedchange,Usage-Morphing,Finishingup,Putthemeshbackasitwasbeforemorphing,Proceedandusemorphedmesh,Control-VolumeAroundCylinder,Control-pointSensitivity,Usage-Morphing,NotesHowtopickthescalefactorTheexpectedchangeiscomputedfromalinearextrapolation.Iftheexpectedchangeislargerthan20%oftheobservedvaluethescalefactorisprobablytoobig!Commonsenseshouldprevailinthechoiceofthescale.Ascalefactorthatgivesanestimateofafewpercentchangeisprobablygood.Excessivescalefactorchoicescangiverisetohighly-distortedmeshesandsometimesnegativecellvolumes.ControlpointsandfixedsurfacesThereisalimitof100controlpointsineachcoordinatedirection.Thelargerthenumberofcontrolpoints,themoredegreesoffreedominthemorphingprocess.Offerssomecontroloversmoothnessofdeformation.Fortypicalapplicationsapproximately30-40controlpointsineachcoordinatedirectionworkswell.Iftherearealargenumberoffixedsurfaces,andmanycontrolpoints,thetimetakentoupdatethecontrolpointsensitivitiescanbecomelarge.Overlyrestrictivefixedsurfacescanresultinpoorguidanceonhowtogetimprovedperformance.,Examples,FulldiscreteadjointforshapesensitivityFrozenturbulenceReducetotalpressuredrop,DP,throughsystem,InternalflowSimple2D,DP=-232.8Expectchange10.0,Baseline,InternalflowSimple3D,Totalpressure,Sensitivityoftotalpressuredroptoshape,InternalflowSimple3D,Totalpressuredrop=-23765PaPredictedchange=2858PaActualchange=2390Pa,180Elbowoptimization,ThankstoHaukeReeseANSYSGermany,180Elbow:OptimizationLoop,Basedesign,Enddesign,180弯管:OptimizationLoop,ICEngineflow,AdjointResiduals,Adjointvelocityvectorscoloredbyadjointpressure,SteadyflowPistonasoutletTotalpressuredrop,ICEngineflow,AdjointResiduals,Shapesensitivityvectors,Contoursofmagnitudeofshapesensitivity,ExternalAutomotiveAerodynamics-Sedan,Surfacemapofthedragsensitivitytoshapechanges,Surfacemapofthedragsensitivitytoshapechanges,Surfacemapofthedragsensitivit