Gambit多孔介质

1、PorousMediaConditionsTheporousmediamodelcanbeusedforawidevarietyofproblems,includingflowsthroughpackedbeds,filterpapers,perforatedplates,flowdistributors,andtubebanks.Whenyouusethismodel,youdefineacellzoneinwhichtheporousmediamodelisappliedandthepressurelossintheflowisdeterminedviayourinputsasdescri

2、bedinSection7.19.2.Heattransferthroughthemediumcanalsoberepresented,subjecttotheassumptionofthermalequilibriumbetweenthemediumandthefluidflow,asdescribedinSection7.19.3.多孔介质可以用于许多广泛的问题，包括填充层过滤纸，穿孔平板，流量分配器,管排等。当你使用这个模型时，你定义一个cellzone来使用多孔介质模型，并且流动中的压力损失通过你输入决定。通过多孔介质传热同样可以描述，给予在多孔介质和流体流动之间的热平衡假设。A1Ds

3、implificationoftheporousmediamodel,termedthe"porousjump,''canbeusedtomodelathinmembranewithknownvelocity/pressure-dropcharacteristics.Theporousjumpmodelisappliedtoafacezone,nottoacellzone,andshouldbeused(insteadofthefullporousmediamodel)wheneverpossiblebecauseitismorerobustandyieldsbett

4、erconvergence.SeeSection7.22fordetails.多孔介质的一维简化称之为“porousjump”，可以用来在知道速度/压降特征的情况下模拟很薄的隔膜。porousjump模型适用于facezone,而不是cellzone,并且尽可能的使用(代替完整的多孔介质模型)因为它更耐用，显示出更好的收敛性。LimitationsandAssumptionsofthePorousMediaModelTheporousmediamodelincorporatesanempiricallydeterminedflowresistanceinaregionofyourmodelde

5、finedas"porous''.Inessence,theporousmediamodelisnothingmorethananaddedmomentumsinkinthegoverningmomentunequations.Assuch,thefollowingmodelingassumptionsandlimitationsshouldbereadilyrecognized:在你定义为多孑L的区域，多孔介质模型结合一个决定经验的流动阻力。本质上，多孔介质模型只不过是在动量方程里附加了一个动量汇，如此的，接下来的模型假设和局限性显而易见。?Sincethevolu

6、meblockagethatisphysicallypresentisnotrepresentedinthemodel,bydefaultFLUENTisesandreportsasuperficialvelocityinsidetheporousmedium,basedonthevolumetricflowrate,toensurecontinuityofthevelocityvectorsacrosstheporousmediuminterface.Asamoreaccuratealternative,youcaninstructFLUENTousethetrue(physical)vel

7、ocityinsidetheporousmedium.SeeSection7.19.7fordetails.因为物理上提到的容积阻塞在这个模型中并不存在，默认地,FLUENTS多孔介质里使用和报告一个非常粗略的速度，基于体积流速，来保证速度向量穿过多孔介只表面时的连续性。另一种更为精确的办法，你可以命令FLUENT®用多孔介质里真实的速度。?Theeffectoftheporousmediumontheturbulencefieldisonlyapproximated.SeeSection7.19.4fordetails.多孔介质对湍流场的影响是近似的。?Whenapplyingth

8、eporousmediamodelinamovingreferenceframe,FLUENTwilleitherapplytherelativereferenceframeortheabsolutereferenceframewhenyouenabletheRelativeVelocityResistanceFormulation.Thisallowsforthecorrectpredictionofthesourceterms.Formoreinformationaboutporousmedia,seeSections7.19.6and7.19.6.当应用多孔介质到移动的参考架时，你使Re

9、lativeVelocityResistanceFormulation可用，FLUENT用相对参考架或者绝对参考架，?Whenspecifyingthespecificheatcapacity,fortheselectedCpmaterialintheporouszone,mustbeenteredasaconstantvalue.q当确定比热容时，对于选定的材料，在porouszone,必须为常数。?MomentumEquationsforPorousMedia?Porousmediaaremodeledbytheadditionofamomentumsourcetermtothestand

10、ardfluidflowequations.Thesourcetermiscomposedoftwoparts:aviscouslossterm(Darcy,thefirsttermontheright-handsideofEquation7.19-1),andaninertiallossterm(thesecondtermontheright-handsideofEquation7.19-1)多孔介质通过在动量方程中附加源项来模拟,源项由两部分组成,粘性损失项(Darcy,7.19-1右边的第一项)和惯性损失项(7.19-1右边的第二项)''/；(7.19-1)v=lj=LJ

11、Siywhereisthesourcetermfortheth(外，,or)momentum也Inequation,isthemagnitudeofthevelocityand-'andareprescribedmatrices.D,C是给定的矩阵Thismomentumsinkcontributestothepressuregradientintheporouscell,creatingapressuredropthatisproportionaltothefluidvelocity(orvelocitysquared)inthecell.动量汇造成了porouscell中的压力梯度

12、，导致了在cell里压降正比于流速。Torecoverthecaseofsimplehomogeneousporousmedia均匀多孔介质中的简单情况方程改写为(7.19-2)awhere1isthepermeabilityandistheinertialresistance1/afactor,simplyspecify.andC：asdiagonalmatriceswithanda,respectively,onthediagonals(andzerofortheotherChelements).。是渗透性是惯性阻力因子，将D,C简化为对角矩阵，1/aa对角线上分别为为，。FLUEN

13、9;lsoallowsthesourcetermtobemodeledasapowerlawofthevelocitymagnitude:FLUENTt许源项被模拟成和速度大小成幕指数形式三一白期81)优(7.19-3)5Q)Ci?whereandareuser-definedempiricalcoefficients.和用户自定义的经验参数。Inthepower-lawmodel,thepressuredropisisotropicandtheDI4一unitsforareSI.号指数模型中，压降各向同性Darcy'sLawinPorousMediaChInlaminarflowst

14、hroughporousmedia,thepressuredropistypicallyproportionaltovelocityandtheconstantcanbeconsideredtobezero.Ignoringconvectiveaccelerationanddiffusion,theporousmediamodelthenreducestoDarcy'sLaw:Ct?层流流过多孔介质时，压降和速度成正比，常数被认为是00忽略对流加速和扩散，多孔介质简化为Darcy法则.二，(7.19-4)Q?ThepressuredropthatFLUENTcomputesineach

15、ofthethree(,y,工)coordinatedirectionswithintheporousregionisthen?3g=£?wherearetheentriesinthematrixinEquation7.19-1,与yarethevelocitycomponentsinthe,anddirections,An,and,andarethethicknessesofthemediuminthey1/ay阴，,andddirections.是方程7.19-1中矩阵D的元素Here,thethicknessofthemedium(,or)istheactualthicknes

16、softheporousregioninyourmodel.Thusifthethicknessesusedinyourmodeldifferfromtheactualthicknesses,l/oijyoumustmaketheadjustmentsinyourinputsfor.介质的厚度是你模拟多孔区域的实际厚度，因此，如果你模型使用的厚度和实际厚度不同，你必须修改1InertialLossesinPorousMediaaAthighflowvelocities,theconstantinEquation7.19-1providesacorrectionforinertiallosses

17、intheporousmedium.Thisconstantcanbeviewedasalosscoefficientperunitlengthalongtheflowdirection,therebyallowingthepressuredroptobespecifiedasafunctionofdynamichead.在高速流动时，方程7.19-1a中的常数对惯性损失提供了修正，这个常数可以被看作流向上每单位长度的损失系数，因此，允许压降看成是动压头的函数。Ifyouaremodelingaperforatedplateortubebank,youcansometimeseliminate

18、thepermeabilitytermandusetheinertiallosstermalone,yieldingthefollowingsimplifiedformoftheporousmediaequation:如果你模拟穿孔平板或者管组时，你可以取消渗透项并且单独使用惯性损失项，从而有下面简单的形式(7.19-6)?orwhenwrittenintermsofthepressuredropinthedirections:,or)is the?Again,thethicknessofthemedium(,thicknessyouhavedefinedinyourmodel.?介质厚度是你

19、定义的厚度力-3Ecaj&i河也|可口冉总$E%Q%可加州，=i%-3引握器不卬aw(7.19-7)用AnvAniAgain,thethicknessofthemedium(,or)isthein Porous Mediathicknessyouhavedefinedinyourmodel.TreatmentoftheEnergyEquationFLUENEolvesthestandardenergytransportequation(Equation13.2-1)inporousmediaregionswithmodificationstotheconductionfluxandth

20、etransienttermsonly.Intheporousmedium,theconductionfluxusesaneffectiveconductivityandthetransienttermincludesthethermalinertiaofthesolidregiononthemedium:FLUENTS多孑L介质中求解标准能量传输方程仅仅引入了对导热和瞬时项的修正。在多孔介质中，导热项使用可等效导热率，在瞬态项中使用了介质固体区域的热惯性。而CwEf+(l-T)pw&)+S幽R+p)=V*-where=totalfluidenergy=totalsolidmedium

21、energy=porosityofthemedium孔隙率一材料中孔隙的总体积与整个材料的体积之间的比=effectivethermalconductivityofthemedium=fluidenthalpysourcetermEffectiveConductivityinthePorousMediumTheeffectivethermalconductivityintheporousmedium,iscomputedbyFLUENTisthevolumeaverageofthefluidconductivityandthesolidconductivity:多孔介质中的等效热导率由流体导热

22、率和固体导热率的容积平均值得到:穹=*/+匚一喂的（7.19-9）where是）流体的导热=porosityofthemedium=fluidphasethermalconductivity(includingtheturbulentcontribution,率，包含了湍流的影响=solidmediumthermalconductivityThefluidthermalconductivityandthesolidthermalconductivitycanbecomputedviauser-definedfunctions.流体热导率和固体热导率可以通过用户自定义函数来计算Theanisot

23、ropiceffectivethermalconductivitycanalsobespecifiedviauser-definedfunctions.Inthiscase,theisotropiccontributionsfrom7t/thefluid,areaddedtothediagonalelementsofthesolidanisotropicthermalconductivitymatrix.各向异性等效热导率同样可以通过用户自定义函数来指定，在这种情况下，流体各向同性的贡献被添加到固体各向异型热导率矩阵的对角元素上。TreatmentofTurbulenceinPorousMed

24、iaFLUENTWill,bydefault,solvethestandardconservationequationsforturbulencequantitiesintheporousmedium.Inthisdefaultapproach,turbulenceinthemediumistreatedasthoughthesolidmediumhasnoeffectontheturbulencegenerationordissipationrates.Thisassumptionmaybereasonableifthemedium'spermeabilityisquitelarge

25、andthegeometricscaleofthemediumdoesnotinteractwiththescaleoftheturbulenteddies.Inotherinstances,however,youmaywanttosuppresstheeffectofturbulenceinthemedium.对于多孔介质中的湍流程度，默认情况下，FLUEN俅解标准的守恒方程来获得。这种默认的方法，介质中的湍流被处理得好像固体介质对于湍流生成和耗散速率没有影响，这种假设当如果介质的渗透性非常大并且介质的几何尺寸与湍流涡旋尺度没有相互影响时是合理的。在其他的情况下，你有可能要减小介质中湍流的影

26、响。Ifyouareusingoneoftheturbulencemodels(withtheexceptionoftheLargeEddySimulation(LES)model),youcansuppresstheeffectofturbulenceinaporousregionbysettingtheturbulentcontributionto出viscosity,equaltozero.Whenyouchoosethisoption,FLUENTwilltransporttheinletturbulencequantitiesthroughthemedium,buttheireffe

27、ctonthefluidmixingandmomentumwillbeignored.Inaddition,thegenerationofturbulencewillbesettozerointhemedium.ThismodelingstrategyisenabledbyturningontheLaminarZoneoptionintheFluid出panel.Enablingthisoptionimpliesthatiszeroandthatgenerationofturbulencewillbezerointhisporouszone.Disablingtheoption(thedefa

28、ult)impliesthatturbulencewillbecomputedintheporousregionjustasinthebulkfluidflow.RefertoSection7.17.1fordetailsaboutusingtheLaminarZoneoption.如果你使用某种湍流模型（除了LES模型），你可以通过设置湍流对于粘性的贡献出为0来减小多孔区域湍流的影响。当你选择了这个选项，FLUENT1入口湍流量通过介质传输，但是他们对于流体混合和动量的影响将会被忽略。另外，介质中湍流的生成将会被设置成0o这种方法将通过使LaminarZoneoption可用来实现。选择这个

29、选项后，在多孔zone"和湍流的生成将会被设置成00取消这个选项则意味着在porousregion湍流将会被计算，正如宏观流体流动一样。SpecifyingaLaminarZoneWhenyouarecalculatingaturbulentflow,itispossibleto"turnoff"turbulencemodelinginaspecificfluidzone.Todisableturbulencemodeling,turnontheLaminarZoneoptionintheFluidpanel.Thiswilldisabletheturbulenc

30、eproduction,buttransporttheturbulencequantities.If,inaddition,youwanttosettheturbulentviscositytozeroyoucandothatusingthetextcommanddefine/boundary-conditions/fluid.YouwillbeaskedifyouwanttoSetTurbulentViscositytozerowithinlaminarzone?.Ifyourresponseisyes,FLUENTwillsetboththeproductiontermintheturbu

31、lencetransportequationMtandtozero.Thisisusefulifyouknowthattheflowinacertainregionislaminar.Forexample,ifyouknowthelocationofthetransitionpointonanairfoil,youcancreatealaminar/turbulenttransitionboundarywherethelaminarcellzoneborderstheturbulentcellzone.Thisfeatureallowsyoutomodelturbulenttransition

32、ontheairfoil.当你计算湍流流动时，可以turnoff'湍流模型在一个特定的流体zone。为了取消湍流模型，turnonLaminarZone,这将会取消湍流的生成，但是会传输湍流量。另外，如果你想要将湍流粘性设置为0,你可以使用文本命令define/boundary-conditions/fluid.你将会被问到是否想要SetTurbulentViscositytozerowithinlaminarzone?如果你回答yes,FLUENTjan皎把湍流传输方程中的产生项和也设为0。当你知道在某些特定区域为层流时特别有用。例如，如果你知道机翼的过渡点位置时，你可以创建层流/湍

33、流过渡边界，边界处层流cellzone与湍流cellzone接壤。Disablingturbulencemodelinginafluidzone,canbeappliedtoalltheturbulencemodelsexcepttheLargeEddySimulation(LES)model.取消湍流模型除了LES模型外所有的都可以使用。EffectofPorosityonTransientScalarEquationsFortransientporousmediacalculations,theeffectofporosityonthetime-derivativetermsisaccou

34、ntedforinallscalartransportequationsandthecontinuityequation.Whentheeffectofporosityistakeninto黑7Meaccount,thetime-derivativetermbecomes,whereisthe7scalarquantity(',etc.)andistheporosity.Theeffectofporosityisenabledautomaticallyfortransientcalculations,andtheporosityissetto1bydefault.对于瞬态多孔介质计算，

35、空隙率对时间偏微分项的影响在所有标量传输方程和连续放中都会被考虑。当空隙率的影响被考虑时，时间偏微分向变为，是标量(左，正等等。)是空隙率。对于瞬态计算，空隙率的影响会自动使用，默认情况下，被设置为1。UserInputsforPorousMediaWhenyouaremodelingaporousregion,theonlyadditionalinputsfortheproblemsetupareasfollows.Optionalinputsareindicatedassuch.当你模拟多孔区域时，对于建立这个问题仅仅需要的额外输入如下1. Definetheporouszone.定义多孔

36、zone2. Definetheporousvelocityformulation.(optional)定义多孑L速度公式3. Identifythefluidmaterialflowingthroughtheporousmedium.定义流过多孑L介质流体的原料4. Enablereactionsfortheporouszone,ifappropriate,andselectthereactionmechanism.多孔zone的化学反应，如果合适的话，选择反映机理5. EnabletheRelativeVelocityResistanceFormulation.Bydefault,this

37、optionisalreadyenabledandtakesthemovingporousmediaintoconsideration(asdescribedinSection7.19.6).使用相对速度阻力公式，默认情况下，此选项已被使用，并且考虑了多孔介质的移动加1/。6. Settheviscousresistancecoefficients(inEquation7.19-1,orinGyaEquation7.19-2)andtheinertialresistancecoefficients(inEquation7.19-1,orinEquation7.19-2),anddefineth

38、edirectionvectorsforwhichtheyapply.Alternatively,specifytheshocoefficientsforthepower-lawmodel.设置粘性阻力系数和惯性阻力系数，并且定义他们用的方向向量。或者，确定哥模型的系数。7. Specifytheporosityoftheporousmedium.确定多孔介质的空隙率8. Selectthematerialcontainedintheporousmedium(requiredonlyformodelsthatincludeCp仅仅能被定为常数。heattransfer).Notethatthe

39、specificheatcapacity,fortheselectedmaterialintheporouszonecanonlybeenteredasaconstantvalue.选择多孔介质的材料(只有包含传热的模型才要求)。注意，在多孔zone选定材料的比热容9. Setthevolumetricheatgenerationrateinthesolidportionoftheporousmedium(oranyothersources,suchasmassormomentum).(optional)确定多孑L介质固体音B分容积产热速率(或者其他的源，如质量或者动量)(可选)10. Set

40、anyfixedvaluesforsolutionvariablesinthefluidregion(optional).在流体区域中设置解变量的固定值(可选)11. Suppresstheturbulentviscosityintheporousregion,ifappropriate.如果合适的话，抑制多孔介质区域中的湍流粘性12. Specifytherotationaxisand/orzonemotion,ifrelevant.选择相应的旋转轴和zone运动。Methodsfordeterminingtheresistancecoefficientsand/orpermeability

41、arepresentedbelow.Ifyouchoosetousethepower-lawapproximationoftheporous-mediamomentumsourceterm,youwillenterthecoefficientsCiandinEquation7.19-3insteadoftheresistancecoefficientsandflowdirection.YouwillsetallparametersfortheporousmediumintheFluidpanel(Figure7.19.1),whichisopenedfromtheBoundaryConditi

42、onspanel(asdescribedinSection7.1.4).FluidZoneNamePorousZoneLaminarZone"SourceTermsFixedValuesPReactionMotionPorousZoneReactionISourceTermsFixedValuesUK|CelFigure7.19.1:TheFluidPanelforaPorousZoneDefiningthePorousZoneAsmentionedinSection7.1,aporouszoneismodeledasaspecialtypeoffluidzone.Toindicat

43、ethatthefluidzoneisaporousregion,enablethePorousZoneoptionintheFluidpanel.Thepanelwillexpandtoshowtheporousmediainputs(asshowninFigure7.19.1).DefiningthePorousVelocityFormulationTheSolverpanelcontainsaPorousFormulationregionwhereyoucaninstructFLUENTouseeitherasuperficialorphysicalvelocityintheporous

44、mediumsimulation.Bydefault,thevelocityissettoSuperficialVelocity.FordetailsaboutusingthePhysicalVelocityformulation,seeSection7.19.7.默认情况下，使用粗略的速度而不是真实的速度DefiningtheFluidPassingThroughthePorousMediumTodefinethefluidthatpassesthroughtheporousmedium,selecttheappropriatefluidintheMaterialNamedrop-downl

45、istintheFluidpanel.Ifyouwanttocheckormodifythepropertiesoftheselectedmaterial,youcanclickEdit.toopentheMaterialpanel;thispanelcontainsjustthepropertiesoftheselectedmaterial,notthefullcontentsofthestandardMaterialspanel.确定流过介质的流体，Ifyouaremodelingspeciestransportormultiphaseflow,theMaterialNamelistwil

46、lnot口appearintheFluidpanel.Forspeciescalculations,themixturematerialforallfluid/porouszoneswillbethematerialyouspecifiedintheSpeciesModelpanel.Formultiphaseflows,thematerialsarespecifiedwhenyoudefinethephases,asdescribedinSection23.10.3.对于模拟组分传输和多项流，MaterialNamelist不会出现在Fluidpanel,对于组分计算，艘由流体和孔zone的

47、混合原料将会在SpeciesModelpanel.里设置。对于多相流，原料是在你定义相时设置EnablingReactionsinaPorousZoneIfyouaremodelingspeciestransportwithreactions,youcanenablereactionsinaporouszonebyturningontheReactionoptionintheFluidpanelandselectingamechanismintheReactionMechanismdrop-downlist.如果你模拟有组分传输和化学反应，enablereactions选项，并在下拉框中选择反

48、应机理Ifyourmechanismcontainswallsurfacereactions,youwillalsoneedtospecifyavaluefortheSurface-to-VolumeRatio.Thisvalueisthesurfaceareaoftheporewallsperunitvolume(),andcanbethoughtofasameasureofcatalystloading.Withthisvalue,FLUENTcancalculatethetotalsurfaceareaonwhichthereactiontakesplaceineachcellbyAVm

49、ultiplyingbythevolumeofthecell.SeeSection14.1.4fordetailsaboutdefiningreactionmechanisms.SeeSection14.2fordetailsaboutwallsurfacereactions.如果你的反应机理包含了壁面反应，你将同样需要对Surface-to-VolumeRatio确定值，这个值是每单位容积孔壁的面积，可以认为是加载催化剂的方法。用这个值，FLUEN研算每个cell总的反应表面积，将cellAV的体积乘。IncludingtheRelativeVelocityResistanceFormula

50、tionPriortoFLUENT6.3,caseswithmovingreferenceframesusedtheabsolutevelocitiesinthesourcecalculationsforinertialandviscousresistance.Thisapproachhasbeenenhancedsothatrelativevelocitiesareusedfortheporoussourcecalculations(Section7.19.2).UsingtheRelativeVelocityResistanceFormulationoption(turnedonbydef

51、ault)allowsyoutobetterpredictthesourcetermsforcasesinvolvingmovingmeshesormovingreferenceframes(MRF).Thisoptionworkswellincaseswithnon-movingandmovingporousmedia.NotethatFLUENTwillusetheappropriatevelocities(relativeorabsolute),dependingonyourcasesetup.LUENT6.3之前由于移动参考系在源项中计算惯性和粘性阻力使用绝对速度，这个方法得到了提高以

52、至于相对速度用来进行孔源项的计算。使用相对速度阻力公式选项允许你在引入动网格或者移动参考系的时候更好的预测源项。在非移动和移动多孔介质中能很好的工作。注意：FLUENT艮据你的设置使用合适的速度(相对或者绝对)DefiningtheViscousandInertialResistanceCoefficientsTheviscousandinertialresistancecoefficientsarebothdefinedinthesamemanner.ThebasicapproachfordefiningthecoefficientsusingaCartesiancoordinatesyst

53、emistodefineonedirectionvectorin2Dortwodirectionvectorsin3D,andthenspecifytheviscousand/orinertialresistancecoefficientsineachdirection.粘性和惯性阻力系数以同样的方式定义，基本方法是使用笛卡尔坐标系来定义一个方向(2D)h或者两个方向向量(3D),然后确定各个方向的阻力系数。In2D,theseconddirection,whichisnotexplicitlydefined,isnormaltotheplanedefinedbythespecifieddir

54、ectionvectorandtheddirectionvector.在2D中,第二个方向并不显示的定义，而是垂直于通过指定方向向量和z方向向量的平板。In3D,thethirddirectionisnormaltotheplanedefinedbythetwospecifieddirectionvectors.在3D中，第三个方向垂直于前两个方向所定义的平面。Fora3Dproblem,theseconddirectionmustbenormaltothefirst.Ifyoufailtospecifytwonormaldirections,thesolverwillensurethatth

55、eyarenormalbyignoringanycomponentoftheseconddirectionthatisinthefirstdirection.Youshouldthereforebecertainthatthefirstdirectioniscorrectlyspecified.对于3D问题，第二个方向必须垂直于第一个，如果你指定两个方向失败，求解器会通过忽略第二个方向的分量来保证它们垂直，即第二个垂直于第一个。因此，你应该确保第一个方向正确的设置。Youcanalsodefinetheviscousand/orinertialresistancecoefficientsine

56、achdirectionusingauser-definedfunction(UDF).Theuser-definedoptionsbecomeavailableinthecorrespondingdrop-downlistwhentheUDFhasbeencreatedandloadedintoFLUENTNotethatthecoefficientsdefinedintheUDFmustutilizetheDEFINE_PROFILEmacro.Formoreinformationoncreatingandusinguser-definedfunction,seetheseparateUD

57、FManual.你同样可以通过UD既定义各个方向的阻力系数。UDF&J建和加载后将在相应的下拉框中获得。注意：UDF中的系数定义必须使用DEFINE_PROFILEmacro。Ifyouaremodelingaxisymmetricswirlingflows,youcanspecifyanadditionaldirectioncomponentfortheviscousand/orinertialresistancecoefficients.Thisdirectioncomponentisalwaystangentialtotheothertwospecifieddirections.

58、Thisoptionisavailableforbothdensity-basedandpressure-basedsolvers.如果你模拟对成涡流，对于阻力系数你可以确定一个额外的方向组分。这个方向组分总是和其他两个方向相切。这个选项对于density和pressure-based求解器均可获得。In3D,itisalsopossibletodefinethecoefficientsusingaconical(orcylindrical)coordinatesystem,asdescribedbelow.在3D中，可以定义系数使用圆锥或圆柱坐标系统。Notethattheviscousandinertialresistancecoefficientsaregenerallybasedonthegsuperficialvelocityofthefluidintheporousmedia.注意：多孔介质中粘性和惯性系数通常基于流体的粗略速度。定义Theprocedurefordefi