fluent 13.0中的自然对流问题

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1、CustomerTrainingMaterialLt4Lecture4NaturalConvectionHeatTransferHeatTransferModelingusingANSYSFLUENTANSYSFLUENTANSYS,Inc.ProprietaryRelease13.0©2010ANSYS,Inc.Allrightsreserved.L4-1December2010HeatTransferModelingusingANSYSFLUENTOutlineCustomerTrainingMaterial1.Theory/Definit

2、ion4.ModelsetupinFLUENTa.Phenomenaa.Referencedensityandb.TransitionTransitiontoturbulentflowtoturbulentflowtemperatureb.Boussinesqvs.incompressibleidealgas2.Turbulencea.Dyyynamicvs.thermalboundary5.ElExampleslayera.Validationcase–Tallcavityb.Fullbuoyancyeffectb.Baselinecases

3、i.CCoseddoaloseddomainwithhighRayayegleigh3.MdliModelingtiipsnumbera.Pressurediscretizationii.PlumewithhighRayleighnumberb.Timesteppingforunsteadyc.Industrialcase–GlasstankTC21simulation6.References7.AppppendixANSYS,Inc.ProprietaryRelease13.0©2010ANSYS,Inc.Allrightsreserved.

4、L4-2December2010CustomerTrainingMaterialNaturalconvection:Theory&Definitions&DefinitionsANSYS,Inc.ProprietaryRelease13.0©2010ANSYS,Inc.Allrightsreserved.L4-3December2010HeatTransferModelingusingANSYSFLUENTPhenomenaCustomerTrainingMaterial•Innaturalconvection,fluid∂Pmotionisg

5、eneratedduetoP+dx∂xT=Tdidensittdydiffifference(b(buoyancy))iinwthefluidcausedbytemperature∂ττyxyxΓxτ+dygradients.yx∂xy•BodyforcesT=Tf–TypicallygravitationalP–Centrifugal(rotatingmachinery)–Coriolis(atmosphericandoceanicvorticalmotion)•Forthisclassofproblems,flowForcesactingo

6、nafluidparticleinandenergyarestronglycoupled.naturalconvection.ANSYS,Inc.ProprietaryRelease13.0©2010ANSYS,Inc.Allrightsreserved.L4-4December2010HeatTransferModelingusingANSYSFLUENTLaminartoTurbulentTransitionCustomerTrainingMaterial•Innaturalconvection,theReynoldsnumbernolon

7、gercharacterizestheflow.•Withanappropriatereferencevelocity,itispossibletodetermineacriticalvalueoftheRayleighnumber(Ra).L–ExperimentsshowthatthecriticalRayleighnumber,Ra,isaround109.c–ThetransitionzoneisquitelargeasRavariesbetween106and1010.BuoyancyforceKinematic3βgLΔTνvisc

8、osityRa=GrPr=wherPr=LLναeαKinematicviscosityKinematicviscosityThermaldiffus