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ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-1April28,2009Inventory#002599Introdu

ctionThePurposeofthetutorialistomodelcavitationinacentrifugalpump,whichinvolvestheuseofarotationdomainandthecavitationmodel.Thep

roblemconsistsofafivebladecentrifugalpumpoperatingat2160rpm.Theworkingfluidiswaterandflowisassumedtobesteadyandincompressible.Duetorotationalperiodic

ityasinglebladepassagewillbemodeled.Theinitialflow-fieldwillbesolvedwithoutcavitation.Itwillbeturnedonlater.ANSYS,Inc.P

roprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-2April28,2009Inventory#0025991.StartW

orkbenchandsavetheprojectascentrifugalpump.wbpj2.DragCFXintotheProjectSchematicfromtheComponentSystemstoolbox3.

StartCFX-PrebydoubleclickingSetup4.WhenCFX-Preopens,importthemeshbyright-clickingonMeshandselectingIm

portMesh>ICEMCFD5.Browsetopump.cfx56.KeepMeshunitsinm7.ClickOpenWorkbenchANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreser

ved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-3April28,2009Inventory#002599Modifyingthematerialprop

erties:1.ExpandMaterialsintheOutlinetree2.Double-clickWater3.OntheMaterialPropertiestabchangeDensityto1000[kg/m3]4.ChangeDynamicViscosityto0.001[kg

m^-1s^-1]underTransportProperties5.ClickOKCreatingWorkingFluidsANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupple

mentWS5:CavitatingCentrifugalPumpWS5-4April28,2009Inventory#002599SettinguptheFluidDomain1.Double-cli

ckonDefaultDomain2.UnderFluidandParticleDefinitions,deleteFluid1andthencreateanewFluidnamedWaterLiquid3.SetMate

rialtoWater4.CreateanothernewFluidnamedWaterVapour5.NexttotheMaterialdrop-downlist,clickthe“…”icon,thentheImportLibra

ryDataicon(ontherightoftheform),andselectWaterVapourat25CundertheWaterDataobject–ClickOK6.BackintheMaterialpanel,selectWaterVapourat25C–Click

OKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-5April28,2009Inventory#002599Setting

uptheFluidDomain7.SettheReferencePressureto0[Pa]8.SetDomainMotiontoRotating9.SetAngularVelocityto2160[revmin^-

1]10.SwitchonAlternateRotationModel11.MakesureRotationAxisunderAxisDefinitionissettoGlobalZ11.SwitchtotheFluidModelstab,andsetthefollowing:12.Tur

nonHomogeneousModelintheMultiphasesection13.UnderHeatTransfersettheOptiontoIsothermal,withaTemperatu

reof25C14.SetTurbulenceOptiontoShearStressTransport15.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsres

erved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-6April28,2009Inventory#002599InletBoundaryCondition1

.InsertaboundaryconditionnamedInlet2.OntheBasicSettingstab,setBoundaryTypetoInlet3.SetLocationtoINLET4.SetFrameTypetoStationary5.Swi

tchtotheBoundaryDetailstab6.SpecifyMassandMomentumwithaNormalSpeedof7.0455[m/s]7.SwitchtotheFluidValuestab8.ForWaterLiquid,set

theVolumeFractiontoaValueof19.ForWaterVapour,settheVolumeFractiontoaValueof010.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsrese

rved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-7April28,2009Inventory#002599OutletBoundaryCondition1.InsetaboundaryconditionnamedOut

let2.OntheBasicSettingstab,setBoundaryTypetoOpening3.SetLocationtoOUT4.SetFrameTypetoStationary5.SwitchtotheBoundaryDetailstab6.SpecifyMas

sandMomentumusingEntrainment,andenteraRelativePressureof600,000[Pa]7.EnablethePressureOptionandsetittoOpeningPressure8.SetTurbulenceOptiontoZeroGr

adient9.SwitchtotheFluidValuestab10.ForWaterLiquid,settheVolumeFractiontoaValueof111.ForWaterVapour,settheVolumeFractiontoaValueof012.ClickOKA

NSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-8A

pril28,2009Inventory#002599PeriodicInterface1.ClicktocreateanInterface,andnameitPeriodic2.SettheInterfaceTypetoFluidFluid3.ForInterfaceSide1,se

ttheRegionListtoDOMAININTERFACE1SIDE1andDOMAININTERFACE2SIDE1(usethe“…”iconandtheCtrlkey)4.ForInterfaceSide2,

settheRegionListtoDOMAININTERFACE1SIDE2andDOMAININTERFACE2SIDE25.SettheInterfaceModelsoptiontoRotationalPeriodicity6.UnderAxisDefinition,sele

ctGlobalZ7.SetMeshConnectionOptionto1:18.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS

5:CavitatingCentrifugalPumpWS5-9April28,2009Inventory#002599WallBoundaryConditions1.InsertaboundaryconditionnamedStationary2.SetittobeaWa

ll,usingtheSTATIONARYlocation3.OntheBoundaryDetailstab,enableaWallVelocityandsetittoCounterRotatingWall4.ClickOK5.IntheOutlineTree,r

ight-clickontheDefaultDomainDefaultboundaryandrenameittoMoving–ThedefaultbehaviorfortheMovingboundaryconditionistomovewiththerotatingdomain,s

othereisnothingthatneedstobesetANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifuga

lPumpWS5-10April28,2009Inventory#002599Initialization1.Clicktoinitializethesolution2.OntheFluidSettingsform,setWaterLiquidVo

lumeFractiontoAutomaticwithValue,andsettheVolumeFractionto13.SetWaterVapourVolumeFractiontoAutomaticwi

thValue,andsettheVolumeFractionto04.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifuga

lPumpWS5-11April28,2009Inventory#002599SolverControl1.DoubleclickSolverControlintheOutlinetree2.SetTimescaleControltoPhysicaltimescaleA

commonlyusedtimescaleinturbomachineryis1/omega,whereomegaistherotationrateinradianspersecond.Youcanuseanexpressiontodetermineatimestepfro

mthis.Inthiscase,2/omegawillbeusedtoachievefasterconvergence.3.EnterthefollowingexpressioninthePhysicalTimesc

alebox:1/(pi*2160[min^-1])4.SetResidualTargetto1e-55.OntheAdvancedOptionstab,turnonMultiphaseControl,thenturnonVolumeFractionCouplingandse

ttheOptiontoCoupled6.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5

-12April28,2009Inventory#002599OutputControl1.DoubleClickonOutputControlintheOutlinetree2.OntheMonitortab,turnonMon

itorOptions3.UnderMonitorPointsandExpressions,createanewobjectandcallitInletPTotalAbs4.SetOptiontoExpression5.Spec

ifythefollowingexpression:massFlowAve(TotalPressureinStnFrame)@Inlet6.CreateanewobjectcalledInletPStatic,andsetOptiontoExpression7.Specifythefollo

wingexpression:areaAve(Pressure)@Inlet8.ClickOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5

:CavitatingCentrifugalPumpWS5-13April28,2009Inventory#002599Solver1.CloseCFX-PreandswitchtotheWorkbe

nchProjectwindow2.Savetheproject3.NowdoubleclickonSolutionintheProjectSchematictostarttheSolverManager4.WhentheSolverManage

ropens,clickStartRun5.Whenthesolutionhascompleted,closetheSolverManagerandreturntotheProjectwindow6.Savethe

projectANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-14

April28,2009Inventory#002599Post-processing1.ViewtheresultsinCFD-PostbydoubleclickingResultsintheProjectSchematic2.InsertaContourbyclicking3.

FortheLocation,click,expandRegionsandthenselectBLADE4.SetVariabletoAbsolutePressurefromtheextendedlist5.Set

RangetoGlobal6.OntheRendertabswitchoffLightingandShowcontourLines7.ClickApplyANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsres

erved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-15April28,2009Inventory#002599Post-processing9.InsertanotherContourontheHUBloca

tion,usingthevariableAbsolutePressurecolouredbyLocalRange.TurnoffLightingandShowContourLines.10.InsertanotherContourontheSHROUDlo

cation,usingthevariableAbsolutePressurecolouredbyLocalRange.TurnoffLightingandShowContourLines.Themin

imumpressureisabovetheSaturationPressureof2650PaforWaterhere.Inthenextstep,theoutletpressurewillbereducedenoughtoinitiateCavitation.ANSYS,Inc.Pro

prietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-16April28,2009Inventory#002599AddinganotherAnalysis

1.CloseCFD-PostandreturntotheProjectSchematic2.ClickthearrownexttotheAcellandselectDuplicate–AnewCFX

projectiscreatedasacopyofthefirst3.ChangethenameofthenewSimulationtoCavitation4.UsethearrownexttotheAcelltoRenameittoNoCavitation5.Savet

heProject6.Double-clickSetupfortheCavitationsimulationtoopenCFX-PreANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopS

upplementWS5:CavitatingCentrifugalPumpWS5-17April28,2009Inventory#002599PhysicsModifications1.EdittheDefault

Domain2.OntheFluidPairModelstabsetMassTransfertoCavitation3.SetOptiontoRayleighPlesset4.TurnonSaturationPressure5.Set

aSaturationPressureof2650[Pa]6.ClickOK7.EdittheOutletBoundaryCondition8.OntheBoundaryDetailstab,settheRelativePressureto300,000

[Pa]9.ClickOKMostcavitationsolutionsshouldbeperformedbyturningcavitationonandthensuccessivelyloweringthesystem

pressureoverseveralrunstomoregraduallyinducecavitation.Tospeedupthisworkshop,asuddenchangeinpressureisintroduced.Notethatthisapproac

hmaynotbesuitableformodellingsomeindustrialcases.ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupple

mentWS5:CavitatingCentrifugalPumpWS5-18April28,2009Inventory#002599PhysicsModifications1.EditSolverControl2

.SettheMax.Iterationsto1503.SettheResidualTargetto1e-44.ClickOK5.CloseCFX-Preandsavetheproject6.IntheProjectSchematic,dragcellA

3ontocellB3–Thenon-cavitatingsolutionwillbeusedastheinitialguessforthecavitatingsolution7.Double-clickSolutionfortheCavitationsystem–In

theSolverManagernotethattheinitialconditionshavebeenprovidedfromtheprojectschematic8.ClickStartRunANSYS,Inc.Proprietary©2009AN

SYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-19April28,2009Inventory#002599CavitationSolut

ionThereisasignificantspikeinresiduals,inpartduetotheoutletpressuredifference,butalsoduetothefactthattheabsolutepressureislowenought

oinducecavitation.1.Whentheruncompletes,closetheSolverManagerandreturntotheProjectSchematic2.Savetheproject3.Double-clickResultsfortheCavitationproj

ecttoopenCFD-PostANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-20April28,2

009Inventory#002599Post-processing1.Ifitisnotenabled,turnonvisibilityfortheWireframeandturnoffvisibilityforanyUserLocationsandPlots2.CreateanXYP

laneatZ=0.01[m]3.ColouritbyAbsolutePressure(thevariableisavailableintheExtendedListbyclicking).UseaGlobalRange–Theminimumabsolutepressureisequiva

lenttotheSaturationPressurespecifiedearlier,whichisastronghintthatsomecavitationhasoccurred4.Changeth

eColourVariabletoWaterVapour.VolumeFraction5.ChangetheColourMaptoBluetoWhiteANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreser

ved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-21April28,2009Inventory#002599Post-processing1.TurnoffvisibilityforPlane12.CreateaVolumeusingt

heIsovolumemethod3.SettheVariabletoWaterVapour.VolumeFraction4.SetModetoAboveValue,andenteravalueof0.55.Toview360degree

softhemodel,double-clickDefaultTransform6.UncheckInstancingInfofromDomain7.Set#ofcopiesto58.Set#ofPassagesto59.Clic

kOKANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.WorkshopSupplementWS5:CavitatingCentrifugalPumpWS5-22April28,2009Inventory#002599Po

st-processingThemainareaofcavitationexistsbetweenthesuctionsideofthebladeandtheshroudinthisgeometry.Aseco

ndaryareaofcavitationisjustbehindtheleadingedgeofthebladeonthepressuresideFurtherstepstotry:1.CalculatetorqueontheBLAD

Eusingthefunctioncalculator(hint,usetheextendedregionlisttofindtheBLADE,anduseGlobalZaxis)2.PlotvelocityVectorsonPlane1,usingthevariableWaterLiqui

d.VelocityinStn.Frame3.Calculatethemassflowthroughthepump(hint:usethefunctioncalculatortoevaluatemassFlowattheO

utletregion)4.Usingasimilarmethodtostep2,calculatethedropinTotalPressurefromInlettoOutlet5.PlotStreamlines,startingfromtheInletloc

ation