FLUENT颗粒流模型

©2008ANSYS,Inc.Allrightsreserved.1ANSYS,Inc.Proprietary2008InternationalANSYSConferenceParticulatemodelinginANSYSCFDJeffMaandMohanSrinivasaANSYSInc.©2008ANSYS,Inc.Allrightsreserved.2ANSYS,Inc.ProprietaryAgenda•SummarizeandillustrateapproachesformodelingparticulatemediainANSYSCFDproducts•HighlightaspectsthathelpincustomizingandextendingthemodelsavailableinFluentandCFX©2008ANSYS,Inc.Allrightsreserved.3ANSYS,Inc.ProprietaryIntroduction•Rheologyofacollectionofparticlesorgrains•Complexmechanicalbehavior–Fluidlike–pneumatictransport,fluidizedbeds–Solidlike–heaps,foundations•Mainfactorsgoverningbehavior–Volumefraction–Shearrates–Influenceoffluid©2008ANSYS,Inc.Allrightsreserved.4ANSYS,Inc.ProprietaryOverviewofmodelingapproachesConceptillustrationborrowedfromProf.TsujiPresentationatWCPT5,April2006FlowaroundindividualparticlesorlocalaveragingContinuummodel(multidimensional)LocalaveragingParticleMotionFluidMotionLagrangianmodelsEulerianGranularTrajectoriesofindividualparticles©2008ANSYS,Inc.Allrightsreserved.5ANSYS,Inc.ProprietaryGranularmodelsavailableinANSYS•Twofluidmodels–Euler-granular–Euler-granularwithfrictionalviscosityfordensephase•Particlemodels–DPMfordilutephase(steadyandtimedependent)–Particletrackingmodelwithaprobabilisticcollisionmodel–DensephaseDPM(DP-DPM)fordenseflowswithlargesizedistributions(UDF)–MacroscopicParticleModel(MPM)forlargeparticles(UDF)©2008ANSYS,Inc.Allrightsreserved.6ANSYS,Inc.ProprietaryParticletoparticleinteractionsCouplingwithcont.phaseAdditionalphysics&chemistryParticleshape,sizedistributionOrderof#ofparticlesComputationspeed¶llelizationDEMDirectcontactandotherforcesimplementationNoneorthroughext.CFDcodeNotimplementedArbitrary(clusteredspheres)shape&distribution~105Stronglydependenton#ofparticles,notparallelized,Rel.slowDPMCollisions&breakupindirectly;packinglimitnotaccountedCorrelation-baseddragforceCoupledwithallstd.Fluentmodels,easytocustomizeSphericalandellipsoidal~106Veryfast,parallelizedMP-PICParticlesarerepresentedbyclusters,packinglimitismaintainedCorrelation-baseddragforceCoupledwithallstd.Fluentmodels,easytocustomizeSpherical,arbitrarysizedistributionavailableNolimitonpart/clusters(testedupto~2.5x105)Rel.fast,affectedbymeshsize&#ofparticles,parallelizedMPMDirectcontactandotherforcesimplementationDrag&torqueresolvedFurthercustomizationpossibleSpherical*,arbitrarydistribution~105Slow,paralleltracking(interactionsnotparallel)EulerGranularIndirect:solidpressure&radialdistr.,otherforcesimplementedindirectlyCell-avg.drag,lift&otherinter-ph.termsCoupledwithallstd.Fluentmodels;easiertocustomizeSpherical;Sizedist.throughpopulationbalancePracticallyunlimitedFast,dependsonthemeshsize&physicsonly,parallelized©2008ANSYS,Inc.Allrightsreserved.7ANSYS,Inc.ProprietaryEuler-Granularmodels©2008ANSYS,Inc.Allrightsreserved.8ANSYS,Inc.ProprietaryForbestresults…•Runthesimulationstransient•Calibratethedraglaw–Governstheminimumfluidizationvelocity–Minimumfluidizationvelocityshouldbematchedwiththeexperimentalvalue•Forthemaximumpackinglimit–Settothevolumefractionatminimumfluidization•Timestep~0.001s–Mayneedtouselowertimestepsifadditionalphysicsisadded©2008ANSYS,Inc.Allrightsreserved.9ANSYS,Inc.ProprietarySegregation•Differencesinparticlesizesanddensitycouldcausesegregation•Inliquidfluidizedbeds–Atlowsuperficialvelocitiessmalleranddenserparticlesareatthebottomandlighterandbiggerparticlesareontop–Athighsuperficialvelocitiessmalleranddenserparticlesareattopandlighterparticlesareatthebottom•SimulationsetuptoreproduceexperimentaldataofMoritomietal(1982)©2008ANSYS,Inc.Allrightsreserved.10ANSYS,Inc.ProprietaryPredictionofsolidinversionHollowcharHollowcharGlassbeadsGlassbeadsCharandglassbeadsarewellmixedatthelowliquidvelocityof2.5mm/sInversionofcharandglassbeadsatahighliquidvelocityof9mm/s©2008ANSYS,Inc.Allrightsreserved.11ANSYS,Inc.ProprietaryQuantitativecomparisonwithexperimentsofMoritomietal.©2008ANSYS,Inc.Allrightsreserved.12ANSYS,Inc.ProprietaryLagrangianinformationfromEuleriansimulations•IsitpossibletorecoveranyparticlelevelinformationfromtheEuleriansolution?•Doparticlesreleasedfromthesamepositionatdifferentinstants,spendthesametimeinthereactor?•Whatisthedistributionoftheresidencetimesatvariouszonesintheequipment?–TimespentinthesprayzoneofaWursterbeddeterminescoatingthicknessHomogenizing?Solution©2008ANSYS,Inc.Allrightsreserved.13ANSYS,Inc.ProprietaryTrackingparticleswiththesecondaryphase•WeneedamechanismtoconvectparticlesbasedontheEulerianvelocity•Bydefault,DPMparticlesconvectwiththeprimaryphase•WecancustomizeFluentintoconvectingparticlesbythesecondaryphaseby–Copyingsecondaryphasevelocitiestotheprimaryphasejustbeforeparticlepositionupdate–Restoreprimaryphasevelocitiesaftertheparticleupdate•UDFtodothisavailable©2008ANSYS,Inc.Allrightsreserved.14ANSYS,Inc.ProprietarySomeresults©2008ANSYS,Inc.Allrightsreserved.15ANSYS,Inc.ProprietaryLagrangianmodels©2008ANSYS,Inc.Allrightsreserved.16ANSYS,Inc.ProprietaryLagrangianmodels•Particle/parcelsaretrackedintheLagrangianphase•Economicalwayofaccountingforparticl