离心泵CFX流场分析教程

Workshop5CavitatingCentrifugalPump IntroductiontoCFX Introduction ThePurposeofthetutorialistomodelcavitationinacentrifugalpump whichinvolvestheuseofarotationdomainandthecavitationmodel Theproblemconsistsofafivebladecentrifugalpumpoperatingat2160rpm Theworkingfluidiswaterandflowisassumedtobesteadyandincompressible Duetorotationalperiodicityasinglebladepassagewillbemodeled Theinitialflow fieldwillbesolvedwithoutcavitation Itwillbeturnedonlater StartWorkbenchandsavetheprojectascentrifugalpump wbpjDragCFXintotheProjectSchematicfromtheComponentSystemstoolboxStartCFX PrebydoubleclickingSetupWhenCFX Preopens importthemeshbyright clickingonMeshandselectingImportMesh ICEMCFDBrowsetopump cfx5KeepMeshunitsinmClickOpen Workbench Modifyingthematerialproperties ExpandMaterialsintheOutlinetreeDouble clickWaterOntheMaterialPropertiestabchangeDensityto1000 kg m3 ChangeDynamicViscosityto0 001 kgm 1s 1 underTransportPropertiesClickOK CreatingWorkingFluids SettinguptheFluidDomain Double clickonDefaultDomainUnderFluidandParticleDefinitions deleteFluid1andthencreateanewFluidnamedWaterLiquidSetMaterialtoWaterCreateanothernewFluidnamedWaterVapourNexttotheMaterialdrop downlist clickthe icon thentheImportLibraryDataicon ontherightoftheform andselectWaterVapourat25CundertheWaterDataobjectClickOKBackintheMaterialpanel selectWaterVapourat25CClickOK SettinguptheFluidDomain SettheReferencePressureto0 Pa SetDomainMotiontoRotatingSetAngularVelocityto2160 revmin 1 SwitchonAlternateRotationModelMakesureRotationAxisunderAxisDefinitionissettoGlobalZSwitchtotheFluidModelstab andsetthefollowing TurnonHomogeneousModelintheMultiphasesectionUnderHeatTransfersettheOptiontoIsothermal withaTemperatureof25CSetTurbulenceOptiontoShearStressTransportClickOK InletBoundaryCondition InsertaboundaryconditionnamedInletOntheBasicSettingstab setBoundaryTypetoInletSetLocationtoINLETSetFrameTypetoStationarySwitchtotheBoundaryDetailstabSpecifyMassandMomentumwithaNormalSpeedof7 0455 m s SwitchtotheFluidValuestabForWaterLiquid settheVolumeFractiontoaValueof1ForWaterVapour settheVolumeFractiontoaValueof0ClickOK OutletBoundaryCondition InsetaboundaryconditionnamedOutletOntheBasicSettingstab setBoundaryTypetoOpeningSetLocationtoOUTSetFrameTypetoStationarySwitchtotheBoundaryDetailstabSpecifyMassandMomentumusingEntrainment andenteraRelativePressureof600 000 Pa EnablethePressureOptionandsetittoOpeningPressureSetTurbulenceOptiontoZeroGradientSwitchtotheFluidValuestabForWaterLiquid settheVolumeFractiontoaValueof1ForWaterVapour settheVolumeFractiontoaValueof0ClickOK PeriodicInterface ClicktocreateanInterface andnameitPeriodicSettheInterfaceTypetoFluidFluidForInterfaceSide1 settheRegionListtoDOMAININTERFACE1SIDE1andDOMAININTERFACE2SIDE1 usethe iconandtheCtrlkey ForInterfaceSide2 settheRegionListtoDOMAININTERFACE1SIDE2andDOMAININTERFACE2SIDE2SettheInterfaceModelsoptiontoRotationalPeriodicityUnderAxisDefinition selectGlobalZSetMeshConnectionOptionto1 1ClickOK WallBoundaryConditions InsertaboundaryconditionnamedStationarySetittobeaWall usingtheSTATIONARYlocationOntheBoundaryDetailstab enableaWallVelocityandsetittoCounterRotatingWallClickOKIntheOutlineTree right clickontheDefaultDomainDefaultboundaryandrenameittoMovingThedefaultbehaviorfortheMovingboundaryconditionistomovewiththerotatingdomain sothereisnothingthatneedstobeset Initialization ClicktoinitializethesolutionOntheFluidSettingsform setWaterLiquidVolumeFractiontoAutomaticwithValue andsettheVolumeFractionto1SetWaterVapourVolumeFractiontoAutomaticwithValue andsettheVolumeFractionto0ClickOK SolverControl DoubleclickSolverControlintheOutlinetreeSetTimescaleControltoPhysicaltimescaleAcommonlyusedtimescaleinturbomachineryis1 omega whereomegaistherotationrateinradianspersecond Youcanuseanexpressiontodetermineatimestepfromthis Inthiscase 2 omegawillbeusedtoachievefasterconvergence EnterthefollowingexpressioninthePhysicalTimescalebox 1 pi 2160 min 1 SetResidualTargetto1e 5OntheAdvancedOptionstab turnonMultiphaseControl thenturnonVolumeFractionCouplingandsettheOptiontoCoupledClickOK OutputControl DoubleClickonOutputControlintheOutlinetreeOntheMonitortab turnonMonitorOptionsUnderMonitorPointsandExpressions createanewobjectandcallitInletPTotalAbsSetOptiontoExpressionSpecifythefollowingexpression massFlowAve TotalPressureinStnFrame InletCreateanewobjectcalledInletPStatic andsetOptiontoExpressionSpecifythefollowingexpression areaAve Pressure InletClickOK Solver CloseCFX PreandswitchtotheWorkbenchProjectwindowSavetheprojectNowdoubleclickonSolutionintheProjectSchematictostarttheSolverManagerWhentheSolverManageropens clickStartRunWhenthesolutionhascompleted closetheSolverManagerandreturntotheProjectwindowSavetheproject Post processing ViewtheresultsinCFD PostbydoubleclickingResultsintheProjectSchematicInsertaContourbyclickingFortheLocation click expandRegionsandthenselectBLADESetVariabletoAbsolutePressurefromtheextendedlistSetRangetoGlobalOntheRendertabswitchoffLightingandShowcontourLinesClickApply Post processing InsertanotherContourontheHUBlocation usingthevariableAbsolutePressurecolouredbyLocalRange TurnoffLightingandShowContourLines InsertanotherContourontheSHROUDlocation usingthevariableAbsolutePressurecolouredbyLocalRange TurnoffLightingandShowContourLines TheminimumpressureisabovetheSaturationPressureof2650PaforWaterhere Inthenextstep theoutletpressurewillbereducedenoughtoinitiateCavitation AddinganotherAnalysis CloseCFD PostandreturntotheProjectSchematicClickthearrownexttotheAcellandselectDuplicateAnewCFXprojectiscreatedasacopyofthefirstChangethenameofthenewSimulationtoCavitationUsethearrownexttotheAcelltoRenameittoNoCavitationSavetheProjectDouble clickSetupfortheCavitationsimulationtoopenCFX Pre PhysicsModifications EdittheDefaultDomainOntheFluidPairModelstabsetMassTransfertoCavitationSetOptiontoRayleighPlessetTurnonSaturationPressureSetaSaturationPressureof2650 Pa ClickOKEdittheOutletBoundaryConditionOntheBoundaryDetailstab settheRelativePressureto300 000 Pa ClickOK PhysicsModifications EditSolverControlSettheMax Iterationsto150SettheResidualTargetto1e 4ClickOKCloseCFX PreandsavetheprojectIntheProjectSchematic dragcellA3ontocellB3Thenon cavitatingsolutionwillbeusedastheinitialguessforthecavitatingsolutionDouble clickSolutionfortheCavitationsystemIntheSolverManagernotethattheinitialconditionshavebeenprovidedfromtheprojectschematicClickStartRun CavitationSolution Thereisasignificantspikeinresiduals inpartduetotheoutletpressuredifference butalsoduetothefactthattheabsolutepressureislowenoughtoinducecavitation Whentheruncompletes closetheSolverManagerandreturntotheProjectSchematicSavetheprojectDouble clickResultsfortheCavitationprojecttoopenCFD Post Post processing Ifitisnotenabled turnonvisibilityfortheWireframeandturnoffvisibilityforanyUserLocationsandPlotsCreateanXYPlaneatZ 0 01 m ColouritbyAbsolutePressure thevariableisavailableintheExtendedListbyclicking UseaGlobalRangeTheminimumabsolutepressureisequivalenttotheSaturationPressurespecifiedearlier whichisastronghintthatsomecavitationhasoccurredChangetheColourVariabletoWaterVapour VolumeFractionChangetheColourMaptoBluetoWhite Post processing TurnoffvisibilityforPlane1CreateaVolumeusingtheIsovolumemethodSettheVariabletoWa