FLOW3D鑄造-進(jìn)階培訓(xùn)-物理選項(xiàng)

新近增加了的模型(2007年和2008年版本)。

常規(guī)模式

特別輸出物理工具和模型參數(shù)設(shè)置詳解目錄InletBC -體積流量網(wǎng)格邊界條件

-離心鑄造入口逆流旋轉(zhuǎn)counter-rotatinginletflowincentrifugalcasting-質(zhì)量/動(dòng)力源

Filling -卷氣和表面缺陷跟蹤

-紊流、渦流粘度

turbulence&eddyviscosity -filters過(guò)濾器 -airbackpressureandventing空氣背壓和排氣

Heat -constant,non-uniformmoldtemperature恒量，非均勻模溫transfer& -micro-andmacro-porositymodels微觀和宏觀孔隙度模型

Solidification-flowinmushyzone -exothermicsleeves

加熱管Output -fillingandsolidificationtimes充填和凝固時(shí)間 -residencetime停留時(shí)間 -distancetravelledbymetal金屬行進(jìn)距離 -porositycriterionfunctionsandDAS孔隙度判據(jù)和DAS體積流量網(wǎng)格邊界條件指定的速度的邊界條件

convenientwhentheopenareaisnotexactlyknownisamorenaturalboundaryconditioninthatflowrateisusuallybetterknownthanvelocitycanbeafunctionoftimeusingtabulardefinitioncanbeusedatbothinletsandoutlets體積流量網(wǎng)格邊界條件

:定義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體積流量網(wǎng)格邊界條件

:界面anyofthesixmeshboundariescharacterizedbythesameflowparametersasthefixed-velocityBC,forexample,temperatureflowdirectionvectordefaultstoinflownormaltotheboundary

newin9.3離心鑄造中的入口流體逆旋轉(zhuǎn)FillingincentrifugalcastingistypicallysimulatedinFLOW-3Dusingthenon-inertialreferenceframemotionmodel.Thecoordinatesystem,togetherwiththemesh,areattachedtotherotatingmold.Thentheincomingmetalshouldrotateintheoppositedirection.

離心鑄造設(shè)置

Option1:constantrotationaroundz-axisOption2:tabularinputfortime-dependentmotion.

Hint:tocheckthecorrectnessoftheinput: -preprocessthesimulation; -openprppltplotfileinAnalyze;

-

lookatthegraphsofangularvelocitiesandaccelerationsvs.time.

newin9.312ExamplewithandwithoutCounter-rotatingFlowWithoutthecounter-rotatingflowcomponenttheincomingmetalisdispersedbythecentrifugalforceWiththecounter-rotatingflowcomponenttheincomingmetaljetismuchmorecoherentcounter-rotation質(zhì)量/動(dòng)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.質(zhì)量/動(dòng)力源

:解釋Mass/MomentumSources:定義shapeUpto100mass/momentumsourcescanbedefined,eachcharacterizedby:sizelocationandorientationmassflowratesourcemotion

shapesizelocationandorientationflowratenewin9.3Mass/momentumsourcesarerepresentedinthecomputationaldomainwithaspecialtypeofparticles.Theseparticlescanbeusedtovisualizethesourceson2Dand3Dplots.Mass/MomentumSources:Visualization目測(cè)查看充填期間的表面缺陷跟蹤

:氧化和夾渣Oxidationandotherinclusionsformingonliquidmetalfreesurfacecancausestructuraldefectsinthefinalcasting.Thedefecttrackingmodelpredictsthelocationandthelikelihoodofthepotentialdefectsduringfillingmaximumbendingstressofanaluminumplateasafunctionoffillingrate(fromJohnCampbell)micrographofacracksurfaceofamotorcyclebreakpedal;reportedly,thepedalbrokeduringaride…充填期間的表面缺陷跟蹤

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

-oxidefilmconcentration; t–time.atfreesurfaceinthebulkRepresententrainedoxidewithavolumeconcentrationCInsurfacecellsoxidesareproducedataconstantrateSimilarmodelappliestofoamresidueinthelostfoamprocess.Theresidueisformedatthemetal/foaminterfaceasafractionoftheburntfoam.likelylocationofdefects充填期間的表面缺陷跟蹤

:范例Whenanalyzingtheresults,lookfor“hotspots”ofthedefectconcentration–localizedpeaksinconcentration.Aluminumdiecasting充填期間的表面缺陷跟蹤

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

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

-activatevariabledensitymodel(noheattransfercanbeusedthen)-setairdensity-activatedrift-fluxmodelwiththeescapeoptionsetaverageairbubblesizebottlefilling激活卷氣模型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:紊流混合長(zhǎng)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=?averageinlet,runnerorgatewidth紊流:渦流粘度的近似法

EddyViscosityApproachlaminarfloweddyviscositycoefficient紊流:

渦流粘度近似法的驗(yàn)證Recommendedforhighpressurediecastingfilling.Fasterthanafullturbulencemodel,lessmemoryrequired,providesadequateresults.過(guò)濾網(wǎng)FiltersinFLOW-3Daredescribedwiththeporousmediummodel.Afilterisrepresentedbyaporousgeometrycomponent.Eachporouscomponentischaracterizedbyseveralparametersdescribingflowlossesandheattransfer.Filtrationofinclusionsisnotincludedinthemodel.locationoffilters過(guò)濾網(wǎng):定義ActivateaporousmediamodelinPhysicsAddanewcomponent,oftypePorousDefineporousmediaproperties:porosity,between0.0(fullyblocked)and1.0(fullyopen)specificarea(forheattransfer)dragcoefficients(flowlosses)capillarypressure過(guò)濾網(wǎng):目測(cè)查看PorousMediaisvisualizedon2DDisplayand3DFAVORizerplotsasarraysofsmalltetrahedrons.3DIso-surfaceplotsinDisplayarebasedsolelyonthevolumefractionvalues.accelerationinertiapressureviscousforcesgravityflowlossesinporousmedia過(guò)濾網(wǎng):定義阻力系數(shù)Twomainflowlossmodels: 1.Linear,porosity-dependentdragcoefficient: 2.Quadratic,Reynoldsnumber-dependentdragcoefficient:D’Arcypermeability:過(guò)濾網(wǎng):線性拖曳模型

U-bulkmetalvelocityu-microscopicmetalvelocitybulkvelocityUDptypicalpressurelosscurveasafunctionofbulkvelocityLUuaporousmedia過(guò)濾網(wǎng):二次拖曳模型

d–theaverageporesizebulkvelocityUDpdasPositivecapillarypressuredescribeshydrophilicmedia.Negativecapillarypressuredescribeshydrophobicmedia.Hint:surfacetensionmodeldoesnothavetobeactivatedtoincludecapillarypressureinporousmedia.過(guò)濾網(wǎng):Capillarypressure毛細(xì)管壓力Capillarypressureaccountsforthesurfacetensionforcesinporousmediaactingatmetal’sfreesurfaceinsidethepores;theseforcescanaddresistancetothemetal(hydrophobicmedia)orpromoteflow(hydrophilicmedia)過(guò)濾網(wǎng):HeatTransfer熱傳Heattransferwithporousmediaisdefinedthesamewayaswiththemold,exceptforoneadditionalvariableforeachporouscomponent:SpecificSurfaceAreaItdescribesthesurfaceareaofthefilterperunitbulkvolumeandisafunctionofitsmicroscopicstructure.Itistypicallyprovidedwiththefilterspecifications.Thedefaultvalueis0.0whichmeansnoheattransferinsidethefilter.過(guò)濾網(wǎng):Output輸出Wheneveraporousmediamodelisactivatedthenormalizeddragcoefficientisstoredasaspatialvariableintheflsgrfdatafile:whereDtisthetimestepsize.DRG=0.0outsideporousmedia(K=0.0)DRG>0.0insideporousmediaDRGiscloserto1.0forhigherflowlosses.

AirBackPressure空氣背壓

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

defineGammaof1.4inFluidspropertytreeintheInitialtab–usetheabsolutevaluefortheatmosphericpressureforVoidinitialstatepressureg=1.4forair背壓:AdiabaticBubbles絕熱氣泡Foragasbubbleswithoutheatandmassexchangewiththesurroundings,itspressureisasimplefunctionofthevolume:whereV0andP0aretheinitialbubblevolumeandpressure.123Bubblesconnectedtoafixed-pressuremeshboundarywithfluidfractionF=0.0,assumetheboundarypressure.Itisrecommendedtoalwaysusetheadiabaticbubblemodelforpermanentmoldfillingproblems,especiallyhighpressurediecasting.Workswellwiththeoxidefilmandairentrainmentmodels.絕熱氣泡:最終備注Aluminumstructuralcomponentdiecasting恒量,非均勻模溫Thermaldiecyclingismodeledindiecastingtoobtainarealistictemperaturedistributioninthedie.Iffillingisthencarriedoutasarestartsimulation,thesetemperaturesareusedastheinitialconditions.Sincefillingtimeisveryshortcomparedtothethermaldiffusiontimescaleinthedie,itmakessensetoassumethatthedietemperaturedoesnotchangeduringfilling.Thissimplificationprovidessignificantgainsinthespeedofthefillingsimulation–over10timesshortertimesandmuchlessmemory.diecyclingsimulationfillingsimulationrestart恒量,非均勻模溫,接上頁(yè)Duetotheassumptionoftheconstantdietemperature,themetalloosesmorethermalenergyduringfilling,equivalenttotheaveragetemperatureofabout5-10degreesforaluminumcastings.Itisimportanttoprovideallthesamethermalpropertiesforthedieasinthefullheattransfermodel,e.g.,duringthethermaldiecyclingsimulation.Otherwise,themetal/dieheattransfercalculationswillnotbeaccurate.Note:anon-uniform,constantmoldtemperaturecanalsobedefinedintheinitialconditions,insteadoftakingitfromaresultsfile.凝固過(guò)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凝固過(guò)程中孔隙度

:模型建立Severalfeedingmodesareconsideredinthemodel:atearlystagesofsolidification,belowsolidcoherencypoint,gravityisthedominantfactor.laterduringsolidification,feedingoccursbyinterdendriticflow,independentlyofgravity.nofeedingoccurswhenthesolidfractionexceedsthecriticalvalue.Thedistinctionismadeusingcriticalandcoherencysolidfractions.凝固過(guò)程中孔隙度

:快速收縮模型

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

:鋼錠范例

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.凝固過(guò)程中孔隙度

:微縮孔模型Computestheformationofmicro-poreswhensolidfractionexceedsthecriticalvalue,Fs>FSCR.Takesintoaccountthebulkmodulusofmetal:

a-speedofsoundinthesolidifyingmetal,

p0

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

:設(shè)置微縮孔模型

Requiresdifferentsolidandliquidphasedensityandacriticalsolidfractionlessthan1.0A380diecasting凝固過(guò)程中孔隙度

:微縮孔模型輸出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:凝固阻力系數(shù)

Theco