FLOW-3D多介质模型-渗流模型.pptxVIP

第四章、FLOW-3D 多孔介质模型;Examples of Porous Media;Porous components Require 2 computational cells to adequately resolve Model object as component if Significant gradients occur through thickness of material Material is anisotropic Porous material may be Isotropic (e.g. bed of uniform particles) Anisotropic (e.g. tube bundles) Porous baffles No thickness, reside on cell faces Best for modeling screens Drag can be linear or quadratic Model assumes baffle is saturated, no bubble pressure across ; Porous Media Modeling Theory;List of topics ;达西定律（Darcy Law）;Darcy’s Law: Flow rate through porous media is proportional to pressure drop according to: where v = macroscopic (superficial) velocity (FLOW-3D computes and reports microscopic velocity) K = intrinsic permeability - may be isotropic or anisotropic (directional) m = dynamic viscosity P = fluid pressure Permeability Property of the porous material Represents the average resistance to flow in a control volume Darcy’s law represents viscous losses through pores Applicable when pore Reynolds number Rep ~ 1, where Rep = Applies well to tightly packed spheres and fibers Does not represent inertial losses in loosely packed beds ;Inertial drag becomes significant when Rep exceeds 10 Darcy’s Law can be extended to include inertial effects Quadratic drag: Forchheimer’s Equation ;Understanding FLOW-3D?’sDrag Model;Porous material characterized by: Solid structure permeated by interconnected capillaries May consist of fibers, particles, open pores Two types of flow inside porous media Saturated Assumes media is already wet If interface between fluid and air exists, treated as sharp Unsaturated Diffuse fluid/air interface - wicking Hysteresis (filling/draining) effects Two contributions to fluid drag in porous media Viscous (Skin Drag) Inertial (Form Drag);Resolve all geometry (FAVOR) Compute pressures and velocities directly from Navier Stokes equations Useful for characterizing materials Computationally expensive;;Po