TheinhomogeneousMUSIGmodelforthesimulationofpolydispersedflowsOriginalResearchArticle

Ageneralizedinhomogeneousmultiplesizegroup(MUSIG)modelbasedontheEulerianmodelingframeworkwasdevelopedinclosecooperationofANSYS-CFXandForschungszentrumDresden-RossendorfandimplementedintotheCFDcodeCFX.Themodelenablesthesubdivisionofthedispersedphaseintoanumberofsizegroupsregardingthemassbalanceaswellasregardingthemomentumbalance. Inthiswork,thespecialcaseofpolydispersedbubblyflowisconsidered.Bysimulatingsuchflows,themassexchangedbetweenbubblesizeclassesbybubblecoalescenceandbubblefragmentation,aswellasthemomentumtransferbetweenthebubblesandthesurroundingliquidduetobubblesizedependentinterfacialforceshavetobeconsidered.Particularlytheliftforcehasbeenproventoplayanimportantroleinestablishingacertainbubblesizedistributiondependentflowregime. Inapreviousstudy[Krepper,E.,Lucas,D.,Prasser,H.-M.,2005.Onthemodelingofbubblyflowinverticalpipes.Nucl.Eng.Des.235,597–611]theapplicationofsucheffectswereconsideredandjustifiedandageneraloutlineofsuchamodelconceptwasgiven.Inthispaperthemodelanditsvalidationforseveralverticalpipeflowsituationsispresented.TheexperimentaldatawereobtainedfromtheTOPFLOWtestfacilityattheForschungszentrumDresden-Rossendorf(FZD).Thewire-meshtechnologymeasuringlocalgasvolumefractions,bubblesizedistributionsandvelocitiesofgasandliquidphaseswereemployed. TheinhomogeneousMUSIGmodelapproachwasshownascapableofdescribingbubblyflowswithhighergascontent.Particularlytheseparationphenomenonofsmallandlargebubblesiswelldescribed.Thisseparationhasbeenprovenasakeyphenomenonintheestablishmentofthecorrespondingflowregime.Weaknessesinthisapproachcanbeattributedtothecharacterizationofbubblecoalescenceandbubblefragmentation,whichmustbefurtherinvestigated.