FLOW3D铸造-进阶培训-物理选项

新近增加了的模型(2007年和2008年版本)。

常规模式

特别输出物理工具和模型参数设置详解目录InletBC -体积流量网格边界条件

-离心铸造入口逆流旋转counter-rotatinginletflowincentrifugalcasting-质量/动力源

Filling -卷气和表面缺陷跟踪

-紊流、涡流粘度

turbulence&eddyviscosity -filters过滤器 -airbackpressureandventing空气背压和排气

Heat -constant,non-uniformmoldtemperature恒量，非均匀模温transfer& -micro-andmacro-porositymodels微观和宏观孔隙度模型

Solidification-flowinmushyzone -exothermicsleeves

加热管Output -fillingandsolidificationtimes充填和凝固时间 -residencetime停留时间 -distancetravelledbymetal金属行进距离 -porositycriterionfunctionsandDAS孔隙度判据和DAS体积流量网格边界条件指定的速度的边界条件

convenientwhentheopenareaisnotexactlyknownisamorenaturalboundaryconditioninthatflowrateisusuallybetterknownthanvelocitycanbeafunctionoftimeusingtabulardefinitioncanbeusedatbothinletsandoutlets体积流量网格边界条件

:定义AflowrateBCisdefinedby: a.flowrateQ(t)≥0.0–mustbepositive

(orzero)!

b.flowdirectionvectorN c.Q(t)isconvertedtouniformvelocityu

basedonopenareaA:

uN

un

=Q/Astraightinflowatleft:

N

=(1,0,0)straightinflowatright:

N

=(-1,0,0)angledinflowatleft:

N

=(N1,

N2,0)angledoutflowatright:

n

=(N1,

N2,0)InallthesecasesQ(t)canbethesame体积流量网格边界条件

:界面anyofthesixmeshboundariescharacterizedbythesameflowparametersasthefixed-velocityBC,forexample,temperatureflowdirectionvectordefaultstoinflownormaltotheboundary

newin9.3离心铸造中的入口流体逆旋转FillingincentrifugalcastingistypicallysimulatedinFLOW-3Dusingthenon-inertialreferenceframemotionmodel.Thecoordinatesystem,togetherwiththemesh,areattachedtotherotatingmold.Thentheincomingmetalshouldrotateintheoppositedirection.

离心铸造设置

Option1:constantrotationaroundz-axisOption2:tabularinputfortime-dependentmotion.

Hint:tocheckthecorrectnessoftheinput: -preprocessthesimulation; -openprppltplotfileinAnalyze;

-

lookatthegraphsofangularvelocitiesandaccelerationsvs.time.

newin9.312ExamplewithandwithoutCounter-rotatingFlowWithoutthecounter-rotatingflowcomponenttheincomingmetalisdispersedbythecentrifugalforceWiththecounter-rotatingflowcomponenttheincomingmetaljetismuchmorecoherentcounter-rotation质量/动力源

Unlikemasssourcesthatareassociatedwithcomponentsandcharacterizedonlybyflowrate,mass/momentumsourcesarenotassociatedwithgeometryandcanbedefinedanywhereintheopenspace.Thesesourcesarecharacterizedbytime-dependentflowrateanddirection.Mass/momentumsourcescanbeusedtodefineinletsinsidethedomainasanalternativetousingmeshboundaryconditions.Bothsourceshavethesamemassflowrate.Mass/momentumsourceshaveadistinctdirectiontotheemergingflow,characterizedbythefluidvelocity,u=Q/A∙n.Mass/MomentumSourcesvs.ComponentSourcesmass/momentumsourcemasssourceAmass/momentumsourceapproximatesaflat,two-dimensionalorificeoutofwhichemergesliquidmetal,e.g.,across-sectionofapipe.质量/动力源

:解释Mass/MomentumSources:定义shapeUpto100mass/momentumsourcescanbedefined,eachcharacterizedby:sizelocationandorientationmassflowratesourcemotion

shapesizelocationandorientationflowratenewin9.3Mass/momentumsourcesarerepresentedinthecomputationaldomainwithaspecialtypeofparticles.Theseparticlescanbeusedtovisualizethesourceson2Dand3Dplots.Mass/MomentumSources:Visualization目测查看充填期间的表面缺陷跟踪

:氧化和夹渣Oxidationandotherinclusionsformingonliquidmetalfreesurfacecancausestructuraldefectsinthefinalcasting.Thedefecttrackingmodelpredictsthelocationandthelikelihoodofthepotentialdefectsduringfillingmaximumbendingstressofanaluminumplateasafunctionoffillingrate(fromJohnCampbell)micrographofacracksurfaceofamotorcyclebreakpedal;reportedly,thepedalbrokeduringaride…充填期间的表面缺陷跟踪

:模型界面Calculatesaconcentrationofoxides,basedonexposuretimetoair.ThevalueforoxidegenerationRateisconstantandarbitrary(>0.0).Theresultisinterpretedasaprobabilityofadefect–thehigherthevalue,thehighertheprobability. C(x,t)

-oxidefilmconcentration; t–time.atfreesurfaceinthebulkRepresententrainedoxidewithavolumeconcentrationCInsurfacecellsoxidesareproducedataconstantrateSimilarmodelappliestofoamresidueinthelostfoamprocess.Theresidueisformedatthemetal/foaminterfaceasafractionoftheburntfoam.likelylocationofdefects充填期间的表面缺陷跟踪

:范例Whenanalyzingtheresults,lookfor“hotspots”ofthedefectconcentration–localizedpeaksinconcentration.Aluminumdiecasting充填期间的表面缺陷跟踪

:更多范例MagnesiumdiecastingAluminumdiecastingLostfoam(aluminum)充填期间的卷气Simpleentrainmentofairduetoturbulenceduringfillingmaycausedefectslikeporosity,leakageandfracture.Airentrainmentoccursasaresultofthebalanceofthreefactors: -turbulencecreatesperturbationsonthefreesurfaces, -gravityandsurfacetensionactasstabilizingforces.EntrainedairisrecordedasavolumefractionCairoftheair/metalmixture.a卷气:模型界面sLimitations:-pressureeffectonentrainedairvolumeisnotincluded.Asaresult, pressurizationofthecavitydoeshasnoeffectontheamountofairinthe metal; -thesizeofentrainedairbubblesisnotpredicted.Note:Itisnotnecessarytouseturbulenceforthismodel

卷气:范例entrainedairdefecttrackingmodelporosityinanaluminumdiecastingAswiththedefecttrackingmodel,lookfor“hotspots”oftheairvolumefraction–highlylocalizedpeaksinconcentration.卷气:范例#2Theairentrainmentmodelcanbeusedintwomodes:Passivemode:Theentrainedairdoesnotalterthedynamicsofthemetal.Onceentrained,theairstaysinthemetal.Activemode:Intheactivemodelthefollowingphenomenaareadded:metal/airdensityiscomputedasaweightedaverage(buoyancy)thebulkvolumeofthemetalincreases(bulking)entrainedairbubblesdriftthoughthemetalandescapebackintotheatmosphereatfreesurface(de-aeration) Theactivemodeshouldbeusedwhen:airentrainmentissignificanttimeislongenoughfortheairtoseparateandescape;thismayhappeningravityandlowpressurefillingprocesses,butnotinpressurediecasting.卷气:模型选项

-activatevariabledensitymodel(noheattransfercanbeusedthen)-setairdensity-activatedrift-fluxmodelwiththeescapeoptionsetaverageairbubblesizebottlefilling激活卷气模型variabledensitymodelairdensityaveragebubblesizeairescapeatfreesurfaceactivatedrift-fluxmodel紊流flowinsidemoldduringfillingisusuallyathighReynoldsnumbers(>20,000)andis,therefore,turbulent;outofthefiveavailablemodels,theRNGmodelisthebestchoice;RNGCPUloadisnotexcessive,<20%;buttypically,bettermeshresolutionisneededtocaptureturbulencethanforlaminarflows;donotuseturbulencewhentheflowisnotturbulent.availableturbulencemodelsWhenusingaturbulencemodel,Turbulentmixinglength(TML)shouldbeset.TMLisrelatedtotheaveragescaleofturbulenteddiesintheflow.Incasting,itisrelatedtothesmallestoftheaveragewallthickness,d,andrunnerandgatewidth,h: TML=0.07*min(d,h)Hint:thelargerthevalueofTML,thehigherthelevelofturbulence.紊流:紊流混合长度

dhturbulentmixinglengthGenerally,turbulencemodelsarenotbeenvalidatedforfillinganalysisingreatdetail,especiallyforhighpressurediecasting.Themainexperimentalparametertomatchisthefillingtime,asingravitycasting(hardtomeasureanythingelse).Iffillingrateisfixed,asinhighpressurediecasting,thenmodelingturbulenceisnotusuallynecessary.Inmanycasesofcomplexgeometries,itishardtoachievesufficientresolutiontobenefitfromtheinclusionofturbulenceinthefillingmodel,especially

inthin-wallcastings.紊流:IsItWorththePrice?Asimplerapproach,EddyViscosity,canbeusedtoapproximateturbulentbehaviorduringfilling:

-laminarflowoption; -increasedconstantviscositycoefficient,meddy,torepresenta uniformlevelofturbulenceThevaluemeddy

iscomputedfromtheReynoldsnumberatalocationintheflowwherevelocityisknown,e.g.,attheinlet:

meddy

=rUL/2000U=averagespeedattheselectedlocationr=metaldensityL=½averageinlet,runnerorgatewidth紊流:涡流粘度的近似法

EddyViscosityApproachlaminarfloweddyviscositycoefficient紊流:

涡流粘度近似法的验证Recommendedforhighpressurediecastingfilling.Fasterthanafullturbulencemodel,lessmemoryrequired,providesadequateresults.过滤网FiltersinFLOW-3Daredescribedwiththeporousmediummodel.Afilterisrepresentedbyaporousgeometrycomponent.Eachporouscomponentischaracterizedbyseveralparametersdescribingflowlossesandheattransfer.Filtrationofinclusionsisnotincludedinthemodel.locationoffilters过滤网:定义ActivateaporousmediamodelinPhysicsAddanewcomponent,oftypePorousDefineporousmediaproperties:porosity,between0.0(fullyblocked)and1.0(fullyopen)specificarea(forheattransfer)dragcoefficients(flowlosses)capillarypressure过滤网:目测查看PorousMediaisvisualizedon2DDisplayand3DFAVORizerplotsasarraysofsmalltetrahedrons.3DIso-surfaceplotsinDisplayarebasedsolelyonthevolumefractionvalues.accelerationinertiapressureviscousforcesgravityflowlossesinporousmedia过滤网:定义阻力系数Twomainflowlossmodels: 1.Linear,porosity-dependentdragcoefficient: 2.Quadratic,Reynoldsnumber-dependentdragcoefficient:D’Arcypermeability:过滤网:线性拖曳模型

U-bulkmetalvelocityu-microscopicmetalvelocitybulkvelocityUDptypicalpressurelosscurveasafunctionofbulkvelocityLUuaporousmedia过滤网:二次拖曳模型

d–theaverageporesizebulkvelocityUDpdasPositivecapillarypressuredescribeshydrophilicmedia.Negativecapillarypressuredescribeshydrophobicmedia.Hint:surfacetensionmodeldoesnothavetobeactivatedtoincludecapillarypressureinporousmedia.过滤网:Capillarypressure毛细管压力Capillarypressureaccountsforthesurfacetensionforcesinporousmediaactingatmetal’sfreesurfaceinsidethepores;theseforcescanaddresistancetothemetal(hydrophobicmedia)orpromoteflow(hydrophilicmedia)过滤网:HeatTransfer热传Heattransferwithporousmediaisdefinedthesamewayaswiththemold,exceptforoneadditionalvariableforeachporouscomponent:SpecificSurfaceAreaItdescribesthesurfaceareaofthefilterperunitbulkvolumeandisafunctionofitsmicroscopicstructure.Itistypicallyprovidedwiththefilterspecifications.Thedefaultvalueis0.0whichmeansnoheattransferinsidethefilter.过滤网:Output输出Wheneveraporousmediamodelisactivatedthenormalizeddragcoefficientisstoredasaspatialvariableintheflsgrfdatafile:whereDtisthetimestepsize.DRG=0.0outsideporousmedia(K=0.0)DRG>0.0insideporousmediaDRGiscloserto1.0forhigherflowlosses.

AirBackPressure空气背压

Aircanbetrappedinsidemetalandmoldandpressurizeprovidingadditionalresistancetothemetalflow.Intheone-fluidapproachtomodelingfilling,aircanbeapproximatedasbubbleswithuniformproperties(pressureandtemperature);noairflowiscomputedwithinthebubbles.Threemainmodesoftreatingtheair:instantandcompleteventing:constantpressurebubbles:gravityfillinginsandmoldsnoventingatall:adiabaticbubbles:highpressurediecastingpartialventing:adiabaticbubbles+vents:gravitydiecastingindividualbubblesTousetheadiabaticbubblemodel:activatethemodelinPhysics

defineGammaof1.4inFluidspropertytreeintheInitialtab–usetheabsolutevaluefortheatmosphericpressureforVoidinitialstatepressureg=1.4forair背压:AdiabaticBubbles绝热气泡Foragasbubbleswithoutheatandmassexchangewiththesurroundings,itspressureisasimplefunctionofthevolume:whereV0andP0aretheinitialbubblevolumeandpressure.123Bubblesconnectedtoafixed-pressuremeshboundarywithfluidfractionF=0.0,assumetheboundarypressure.Itisrecommendedtoalwaysusetheadiabaticbubblemodelforpermanentmoldfillingproblems,especiallyhighpressurediecasting.Workswellwiththeoxidefilmandairentrainmentmodels.绝热气泡:最终备注Aluminumstructuralcomponentdiecasting恒量,非均匀模温Thermaldiecyclingismodeledindiecastingtoobtainarealistictemperaturedistributioninthedie.Iffillingisthencarriedoutasarestartsimulation,thesetemperaturesareusedastheinitialconditions.Sincefillingtimeisveryshortcomparedtothethermaldiffusiontimescaleinthedie,itmakessensetoassumethatthedietemperaturedoesnotchangeduringfilling.Thissimplificationprovidessignificantgainsinthespeedofthefillingsimulation–over10timesshortertimesandmuchlessmemory.diecyclingsimulationfillingsimulationrestart恒量,非均匀模温,接上页Duetotheassumptionoftheconstantdietemperature,themetalloosesmorethermalenergyduringfilling,equivalenttotheaveragetemperatureofabout5-10degreesforaluminumcastings.Itisimportanttoprovideallthesamethermalpropertiesforthedieasinthefullheattransfermodel,e.g.,duringthethermaldiecyclingsimulation.Otherwise,themetal/dieheattransfercalculationswillnotbeaccurate.Note:anon-uniform,constantmoldtemperaturecanalsobedefinedintheinitialconditions,insteadoftakingitfromaresultsfile.凝固过程中孔隙度

Porosityformsasaresultofthechangeinmetaldensityduringsolidification.Inmany(butnotall)alloysthesolidphasedensityislargerthanthedensityoftheliquidphase.Asaresult,themetalshrinksasitcoolsandsolidifies.Porosityisthe#1reasonforrejectedcastings:Adequatefeedingmustbeprovidedtocompensatefortheshrinkageand/ormoveitto“safe”locations.macroporositymicroporosity

-poormechanicalproperties -leakage -surfacedefectsTwomodelsareavailableinFLOW-3Dtopredictporosity: -macroposity(RapidShrinkage) -microporosityBothmodelsassumealineardependencyofmetaldensityronsolidfractionfs:wherersandrl

aretheuser-definedconstantsolidandliquidphasedensities,respectively.Bothmodelsarebasedonthethermalsolution.Feedingiscomputedfromthethree-dimensionaldistributionoftemperatureandsolidfraction.Themodelscanbeusedincombinationwitheachother.Therapidshrinkagemodelassumesnofluidflow.Themicroporositymodelcanbeusedwithany

flowandsolidificationmodel凝固过程中孔隙度

:模型建立Severalfeedingmodesareconsideredinthemodel:atearlystagesofsolidification,belowsolidcoherencypoint,gravityisthedominantfactor.laterduringsolidification,feedingoccursbyinterdendriticflow,independentlyofgravity.nofeedingoccurswhenthesolidfractionexceedsthecriticalvalue.Thedistinctionismadeusingcriticalandcoherencysolidfractions.凝固过程中孔隙度

:快速收缩模型

gsolidI.Feedingbygravity:min(Fs)<FSCOII.Interdendriticfeedingatlaterstages:min(Fs)>FSCOcoolingsolidliquidmushyverymushy凝固过程中孔隙度

:钢锭范例

FSCO=0.15FSCR=0.67(default)FSCO=0.0FSCR=0.67FSCO=0.7FSCR=0.8Macroporosityisbestdisplayedintermsoffluidfraction:

F=1.0–soundcasting

F<1.0–containspores:(1-F)times100%byvolumeThesizeandlocationoftheporositycanbecontrolledbyadjustingthevaluesofthecriticalandcoherencysolidfractions.凝固过程中孔隙度

:微缩孔模型Computestheformationofmicro-poreswhensolidfractionexceedsthecriticalvalue,Fs>FSCR.Takesintoaccountthebulkmodulusofmetal:

a-speedofsoundinthesolidifyingmetal,

p0

–intensificationorinitialpressure.Whenpressuredropsbelowacriticalvalue,porosityforms.Thus,pressurizationofthemetalcanreducetheamountofporosity.Calculatesandstores%porositybyvolume.solidfractiontimemetalpressurefscrp_intensificationp_poremicroporosityforms20.0e+05newin9.3solidfractiontimemetalpressurefscrIntensificationpressureGasporepressuremicroporosityforms凝固过程中孔隙度

:设置微缩孔模型

Requiresdifferentsolidandliquidphasedensityandacriticalsolidfractionlessthan1.0A380diecasting凝固过程中孔隙度

:微缩孔模型输出FlowinMushyZoneIIIIIISeveraloptionsareavailabletomodelflowofsemi-solid(mushy)metal.Inthestandard(default)model,flowisdividedintothreeregimes:0.0<fs<FSCO-solidcrystalsfloatfreelyintheliquidphase(suspensionflow);themixtureviscosityincreaseswithfs.FSCO<fs

<FSCR–solidcrystalsformarigidcoherentstructure,liquidphaseseepsthroughit(porousmediaflow);aD’Arcytypedragcoefficientisapplied.FSCR<fs

<1.0–liquiddoesnotformcontinuousflowregions;noflowonmacroscopicscale:K∞.FlowinMushyZone:凝固阻力系数

Theco