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FLOW-3D多孔介质模型-渗流模型.pptx

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第四章、FLOW-3D多孔介质模型ExamplesofPorousMediaPorouscomponents Require2computationalcellstoadequatelyresolve Modelobjectascomponentif Significantgradientsoccurthroughthicknessofmaterial Materialisanisotropic Porousmaterialmaybe Isotropic(e.g.bedofuniformparticles) Anisotropic(e.g.tubebundles) Porousbaffles Nothickness,resideoncellfaces Bestformodelingscreens Dragcanbelinearorquadratic Modelassumesbaffleissaturated,nobubblepressureacross PorousMediaModeling TheoryListoftopics达西定律（DarcyLaw）Darcy’sLaw:Flowratethroughporousmediaisproportionaltopressuredropaccordingto: where v=macroscopic(superficial)velocity(FLOW-3Dcomputesandreportsmicroscopicvelocity) K=intrinsicpermeability-maybeisotropicoranisotropic(directional) m=dynamicviscosity P=fluidpressure Permeability Propertyoftheporousmaterial Representstheaverageresistancetoflowinacontrolvolume Darcy’slawrepresentsviscouslossesthroughpores ApplicablewhenporeReynoldsnumberRep~1,whereRep= Applieswelltotightlypackedspheresandfibers Doesnotrepresentinertiallossesinlooselypackedbeds InertialdragbecomessignificantwhenRepexceeds10 Darcy’sLawcanbeextendedtoincludeinertialeffects Quadraticdrag:Forchheimer’sEquation UnderstandingFLOW-3D®’sDragModelPorousmaterialcharacterizedby: Solidstructurepermeatedbyinterconnectedcapillaries Mayconsistoffibers,particles,openpores Twotypesofflowinsideporousmedia Saturated Assumesmediaisalreadywet Ifinterfacebetweenfluidandairexists,treatedassharp Unsaturated Diffusefluid/airinterface-wicking Hysteresis(filling/draining)effects Twocontributionstofluiddraginporousmedia Viscous(SkinDrag) Inertial(FormDrag)Resolveallgeometry(FAVOR) ComputepressuresandvelocitiesdirectlyfromNavierStokesequations Usefulforcharacterizingmaterials ComputationallyexpensivePorousmediasimulationsetupsteps: Decideflowtype:SaturatedorUnsaturated Defineporousgeometry DragModel 3choicesforsaturatedflow 1choiceforunsaturatedflow CharacterizeMaterial Porosity Fitdragcoefficients experimentaldata computefromfiber/