FLOW-3D多孔介质模型-渗流模型VIP专享VIP免费

第四章、FLOW-3D多孔介质模型FLOW-3D®v9.4ExamplesofPorousMediaFebruary3,2025UserTrainingSpongeWireScreenStreambedSinterMetalFilterPaperTubeBundle•Porouscomponents–Require2computationalcellstoadequatelyresolve–Modelobjectascomponentif•Significantgradientsoccurthroughthicknessofmaterial•Materialisanisotropic–Porousmaterialmaybe•Isotropic(e.g.bedofuniformparticles)•Anisotropic(e.g.tubebundles)•Porousbaffles–Nothickness,resideoncellfaces–Bestformodelingscreens–Dragcanbelinearorquadratic–Modelassumesbaffleissaturated,nobubblepressureacrossTypesofPorousObjectsinFLOW-3DFebruary3,2025UserTrainingPorousMediaModelingTheoryListoftopics•介绍达西定律（Darcylaw）•介绍FLOW-3D®拖曳力模型(dragmodel)•介绍饱和多孔介质模型(thesaturatedporousmediamodel)•介绍拖曳力系数与渗透率的关系(dragcoefficientandpermeability)•如何处理流体在多孔介质中的各向异性(anisotropy)特征•介绍非饱和多孔介质模型(theunsaturatedporousmediamodel)达西定律（DarcyLaw）Q:unitsofvolumepertime(e.g.,m³/s)A:cross-sectionalarea(Pb−Pa):thepressuredropμ:dynamicviscosityΚ:thepermeabilityofthemedium(unitsofarea,e.g.m²)L:thelength•Darcy’sLaw:Flowratethroughporousmediaisproportionaltopressuredropaccordingto:wherev=macroscopic(superficial)velocity(FLOW-3Dcomputesandreportsmicroscopicvelocity)K=intrinsicpermeability-maybeisotropicoranisotropic(directional)m=dynamicviscosityP=fluidpressure•Permeability–Propertyoftheporousmaterial–Representstheaverageresistancetoflowinacontrolvolume•Darcy’slawrepresentsviscouslossesthroughpores–ApplicablewhenporeReynoldsnumberRep~1,whereRep=–Applieswelltotightlypackedspheresandfibers–DoesnotrepresentinertiallossesinlooselypackedbedsViscousDraginPorousMedia:Darcy’sLawvKxPporeLu•InertialdragbecomessignificantwhenRepexceeds10•Darcy’sLawcanbeextendedtoincludeinertialeffects•Quadraticdrag:Forchheimer’sEquationInertialLosses:Forchheimer’sEquation22/1ucKuKxPviscoustransitionalinertialwherer=fluiddensityUnderstandingFLOW-3D®’sDragModel•由于流体在多孔介质中受到的很多阻力太小而无法求解，所以用一个均布的阻力系数来计算：•K表示拖曳力系数，也就是流体在多孔介质中的流动阻力。uGuAuuAuffKVpVtff111TotalaccelerationInertiaAcc.duetopress.gradientAccel.duetoviscosityAccel.duetogravityDrageffectsVf=Volumefraction(porosity)ofcomputationalcellAf=DiagonaltensorareafractionsofcellN-S张量方程•Porousmaterialcharacterizedby:–Solidstructurepermeatedbyinterconnectedcapillaries–Mayconsistoffibers,particles,openpores•Twotypesofflowinsideporousmedia–Saturated•Assumesmediaisalreadywet•Ifinterfacebetweenfluidandairexists,treatedassharp–Unsaturated•Diffusefluid/airinterface-wicking•Hysteresis(filling/draining)effects•Twocontributionstofluiddraginporousmedia–Viscous(SkinDrag)–Inertial(FormDrag)PorousMediaFlow•Resolveallgeometry(FAVOR)•ComputepressuresandvelocitiesdirectlyfromNavierStokesequations•Usefulforcharacterizingmaterials•ComputationallyexpensiveApproachestoModelingPorousMaterialsDirectVolumeAveraged•Geometryrepresentedasvolumefraction(porosity)opentoflow•Assumeflowisuniformovercell•RequiressomeknowledgeofmaterialPorosityPressuredropvsvelocityorParticle/fibersizeFocusofthispresentationisthevolumeaveragedapproach•SaturatedFlow•UnsaturatedFlowInterfacialEffects:CapillaryPressure•Generallyappliesto...