Lecture 4 - Boundary & Initial Conditions――FloEFD的

.Lecture4BoundaryConditions&InitialConditions81.Conditions•AnyproblemsolvedwithEFDmusthaveboundaryconditionsandinitialconditions.•Insteadystateproblems,initialconditionsinfluencetherateofconvergencetothefinalsolution,whereasboundaryconditionsfullygoverntheflowpattern.•Intransient(unsteady)problemsthetime-dependentflowpatterndependsbothoninitialconditionsandboundaryconditions.82.Createaboundarycondition•ClickBoundaryConditionontheEFDFeaturestoolbar.•FlowAnalysis,Insert,BoundaryCondition.•IntheEFDanalysistreeright-clicktheBoundaryConditionsiconandselectInsertBoundaryConditionYoucanalsoright-clickamodelfaceinthegraphicsareaandselectInsertBoundaryConditiontocreateaboundaryconditionontheselectedface.83.•Youcanvisualizespecifiedboundaryconditionsdirectlyonthemodel:–coloredarrowsindicatethedirectionandtypeofcondition.–Right-clickaboundaryconditionitemintheEFDanalysistreeandselectShoworHidetoturnonorturnoffthearrows.84.Boundaryconditiontypes•FlowOpenings–Inletoroutlet–Velocity;Massflowrate;Volumeflowrate•PressureOpenings–Staticpressure;Totalpressure;Environmentpressure•Walls–Realwall;Idealwall;Outerwall85.FlowOpenings()•Inlet/outlet•MassFlowVolumeFlowVelocityMachNumber86.FlowParameters•NormalToFace.Theflowisperpendiculartotheopeningsurface.•Swirl.Allowsyoutospecifyswirlingoftheflowaboutthereferenceaxis.–Right-HandGripRule(alsoknownastheCorkscrewRule)–Angularvelocityandradialvelocity•3DVector.VectorcomponentsinX,Y,Zdirectionsforangledflows87.•InletProfile.Forintegralinletflowconditionssuchasmassflowrateandvolumeflowrate,youcanspecifyaninletvelocityprofile(e.g.parabolicprofile).88.PressureOpenings()•StaticPressure,TotalPressureorEnvironmentPressure–TheEnvironmentPressureconditionisinterpretedbyEFDasatotalpressureforincomingflowsandasastaticpressureforoutgoingflows.•Temperature89.Walls()•Idealwall–Theidealwallconditionallowsyoutospecifyallselectedfacesasadiabatic,frictionlesswallinsteadofthedefaultfluidfrictionwall•Realwall–specifyroughnessand/orheattransfercoefficientand/orwalltemperature90.•WallTemperature–Thespecifiedwalltemperatureisconsideredasaheatsource(orsink)•HeatTransferCoefficient–Q=(Ts-Tf)S.•WallRoughnessWalls()91.HeatSources•SurfaceSource–Heatconductioninsolidsdisabled–HeatTransferRate(W)–HeatFlux(W/m2)–Heatconductioninsolidsdisabled–HeatGenerationRate(W)–SurfaceHeatGenerationRate(W/m2)92.HeatSources•VolumeSource–HeatGenerationRate(W)–VolumetricHeatGenerationRate(W/m3)–Temperature(oCorK)93.Fan•AFanisconsideredasanidealdevicecreatingavolume(ormass)flowrate(withanoptionalswirling).•FanperformancecurvecanbefoundintheEngineeringDatabase.ItisstronglyrecommendedtocontacttheFanmanufacturerforthelatesttechnicaldataforthefanofyourchoice.94.•Fancurves95.OtherParameters•Humidity.–IftheRelativeHumidityofgasiscalculatedintheproject(theHumidityoptionisenabled)•SubstanceConcentrations.–Formultiplefluids,therelativeconcentrationofeachonecanbespecifiedeitherbymassorvolume.•TurbulenceParameters•BoundaryLayer.–TurbulentorLaminar(Turbulentbydefault).96.InitialConditions(optional)•IfyouwanttosolveanInternalprobleminashortertime,simplyspecifyinitialconditionsclosertotheassumedsolution(insteadofusingthedefaultvalues).•IfyousolveanExternalproblem,youspecifyinitialconditionsasInitialandambientconditions.Ambientconditionsarevaluesoftheundisturbedexternalflow’sindependentparameters.97.•Forgases:–Staticpressure,statictemperature,staticdensity(any2ofthem)–Velocity(orMachnumber)•Forliquids:–Staticpressure,temperature,andvelocity•Forsolids:–Temperature98.Createaninitialcondition•ClickInitialConditionontheEFDFeaturestoolbar.•FlowAnalysis,Insert,InitialCondition.•IntheEFDanalysistreeright-clicktheInitialConditionsiconandselectInsertInitialCondition99.LocalInitialConditionYoucancreateaprojectthatincludesinternalflowregionswithinitialconditionsthataredifferentfromthedefaults.•aclosedfluidregion–Selectoneofthefacesboundingtheregion•disabledcomponentparts–Ifafluidcomponentoverlapsthesolidregion,EFDconsiderstheoverlappedregionasasolid.100