Transcription of Radiation in ANSYS FLUENT
1 61 Radiation in ANSYS Fluent1 Radiation in ANSYS FLUENT61 Radiation in ANSYS Fluent2 Overview ANSYSF luentprovidesfiveradiationmodelsthatallo wustoincluderadiation,withorwithoutapart icipatingmedium,inheattransfersimulation s. Heatingorcoolingofsurfacesduetoradiation and/orheatsourcesorsinksduetoradiationwi thinthefluidphasecanbeincludedinyourmode lusingoneofthefollowingradiationmodels. Discrete transfer Radiation Model (DTRM) P1 Radiation Model Rosseland Model Surface-to-Surface (S2S) Discrete Ordinates Model (DOM)Inadditiontotheseradiationmodels, in ANSYS Fluent3 Weshouldincluderadiativeheattransferinou rsimulationswhentheradiantheatfluxislarg ecomparedtotheheattransferrateduetoconve ctionorconduction.
2 Applications61 Radiation in ANSYS Fluent4 radiativeheattransferfromflames surface-to-surfaceradiantheatingorcoolin g coupledradiation,convection,and/orconduc tionheattransfer radiationthroughwindowsinHVAC(Heating,ve ntilation,andairconditioning)application s,andcabinheattransferanalysisinautomoti veandaircraftapplications radiationinglassprocessing,glassfiberdra wing,andceramicprocessing(materialsproce ssing) ApplicationsTypicalapplications61 Radiation in ANSYS Fluent5 Applicationshow radiant ceiling heating and cooling work61 Radiation in ANSYS Fluent6 Radiative transfer EquationRadiative heat Transfera+ in ANSYS Fluent7 1.
3 Discrete transfer Radiation Model Mainassumption Radiationleavingasurfaceelementwithinasp ecifiedrangeofsolidanglescanbeapproximat edbyasingleray. Usesaray-tracingtechniquetointegrateradi antintensityalongeachray: Advantages: Relatively simple model. Can increase accuracy by increasing number of rays. Applicable to a wide range of optical thicknesses. Limitations: Assumes all surfaces are diffuse. Effect of scattering not included. Solving a problem with a large number of rays is in ANSYS Fluent8 2. P-1 modelMainassumption ThedirectionaldependenceinRTEisintegrate dout,resultinginadiffusionequationforinc identradiation.
4 Advantages: Radiativetransferequationeasytosolvewith smallCPUdemand. ,droplets,andsootcanbeincluded. Worksreasonablywellforapplicationswheret heopticalthicknessislarge( ,combustion). Limitations: Assumesallsurfacesarediffuse. Mayresultinlossofaccuracy(dependingonthe complexityofthegeometry)iftheopticalthic knessissmall. Tendstooverpredictradiativefluxesfromloc alizedheatsourcesorsinks. in ANSYS Fluent9 3. Rosseland Model (astheP-1modeldoes),theRosselandmodelisf asterthantheP-1modelandrequireslessmemor y. ;itisavailablewiththepressure-basedsolve r, in ANSYS Fluent10 4. Surface-to-Surface Radiation ModelTheS2 Sradiationmodelcanbeusedformodelingradia tioninsituationswherethereisnoparticipat ingmedia.
5 Forexample,spacecraftheatrejectionsystem ,solarcollectorsystems,radiativespacehea ters,andautomotiveunderhoodcooling. S2S is a view-factor based model. Non-participating media is assumed. Limitations: The S2S model assumes that all surfaces are diffuse. The implementation assumes gray Radiation . Storage and memory requirements increase very rapidly as the number of surface faces increases. Memory requirements can be reduced by using clusters of surface faces. Clustering does not work with sliding meshes or hanging nodes. Not to be used with periodic or symmetry boundary in ANSYS Fluent11 5. Discrete Ordinates ModelThe radiative transfer equation is solved for a discrete number of finite solid angles, s: Advantages: Mostcomprehensiveradiationmodel:Accounts forscattering,semi-transparentmedia,spec ularsurfaces,andwavelength-dependenttran smissionusingbanded-grayoption.
6 Limitations Solving a problem with a large number of ordinates is in ANSYS Fluent12 Gray Radiation and non-gray , in ANSYS Fluent13 Solar Load Model Solarloadmodel Raytracingalgorithmforsolarradiantenergy transport:Compatiblewithallradiationmode ls Availablewithparallelsolver(butraytracin galgorithmisnotparallelized) 3 Donly Specifications Sundirectionvector Solarintensity(direct,diffuse) Solarcalculatorforcalculatingdirectionan ddirectintensityusingtheoreticalmaximumo r fairweatherconditions Transientcases61 Radiation in ANSYS Fluent14 Choosing a Radiation model Forcertainproblems,oneradiationmodelmayb emoreappropriatethanothers.
7 Computationaleffort P1givesreasonableaccuracywithlesseffort. Accuracy DTRMandDOMmoreaccurate. Opticalthickness DTRM/DOMforopticallythinmedia( L<<small);P1betterforopticallythickmedia . Scattering P1andDOMaccountforscattering. Particulateeffects P1andDOMaccountforradiationexchangebetwe engasandparticulates. Localizedheatsources DTRM/ in ANSYS Fluent15 Main stepsTheprocedureforsettingupandsolvinga radiationproblemisoutlinedbelow, , in ANSYS Fluent16 Related settings Settheappropriateradiationparameters. Ifwearemodelingnon-grayradiationusingthe P-1model,definethenon-grayradiationparam etersasdescribedinSettingUptheP-1 ModelwithNon-GrayRadiation.
8 IfweareusingtheDTRM,definetheraytracinga sdescribedinSettingUptheDTRM. IfweareusingtheS2 Smodel,definethesurfaceclustersandviewfa ctorssettingsandcomputeorreadtheviewfact orsasdescribedinSettingUptheS2 SModel. IfyouareusingtheDOmodel,chooseDO/EnergyC ouplingifdesired,definetheangulardiscret izationasdescribedinSettingUptheDOModela nd,ifrelevant, in ANSYS Fluent17 Related settings Definethematerialpropertiesasdescribedin DefiningMaterialPropertiesforRadiation. ,seetheinformationbelowonsettingupsemi-t ransparentmedia. Settheparametersthatcontrolthesolution(D TRM,DO,S2S,andP-1only)asdescribedinSolut ionStrategiesforRadiationModeling.
9 RunthesolutionasdescribedinRunningtheCal culation. in ANSYS Fluent18 Example using FluentInthisexample, : Usethesurface-to-surface(S2S)radiationmo delinANSYSFLUENT. Settheboundaryconditionsforaheattransfer probleminvolvingnaturalconvectionandradi ation. Calculateasolutionusingthepressure-based solver. Displayvelocityvectorsandcontoursofwallt emperature,surfaceclusterID, in ANSYS Fluent19 Problem , ,absorb, ,aswellasthewallheatflux,usingthesurface -to-surface(S2S) ,andtheRayleighnumberbasedonL( ) , in ANSYS Fluent20 Main stepsStep1:MeshStep2:GeneralSettingsStep 3:ModelsStep4:MaterialsStep5:BoundaryCon ditionsStep6:SolutionStep7:Postprocessin gStep8:ComparetheContourPlotsafterVaryin gRadiatingSurfacesStep9:S2 SDefinition,Solution,andPostprocessingwi thPartialEnclosure61 Radiation in ANSYS Fluent21 Step 1: Mesh61 Radiation in ANSYS Fluent22 Step 1.
10 Mesh-geometry Geometry>surface>standard_shapes61 Radiation in ANSYS Fluent23 Step 1: Mesh-creating part61 Radiation in ANSYS Fluent24 Step 1: Mesh-creating blockStructuredmesh61 Radiation in ANSYS Fluent25 Step 1: Mesh-setting nodes61 Radiation in ANSYS Fluent26 Step 1: Mesh-check mesh quality61 Radiation in ANSYS Fluent27 Step 1: Mesh(80 80 80)(40 40 40)61 Radiation in ANSYS Fluent28 Step 1: Mesh-output mesh61 Radiation in ANSYS Fluent29 Step 1: MeshThemeshsizewillbereportedas64,000cel ls(40 40 40). in ANSYS Fluent30 Step 2: General Settingsa. Retain the default settings in the Solver group Enable the Gravity Enter m/s2for Y in the Gravitational Acceleration group in ANSYS Fluent31 Step 3: Models1.
