chapter4—porousmediamodel.ppt

2. 物理模型 指定类型 指定拖曳系数 3. 过滤网参数设定 指定参数 以 FAVOR 查看网格建立好坏 在网格划分完成后，可以用 FAVOR 查看在现有网格数量设定下，是否能够完整的描述几何外形。 选择 Render 4、过滤网材料选择 材料的材质会影响热传的速度以及温度的分布。不同的材料其温度传递的速度也会不同。 FLOW-3D 提供过滤网的材料 ，用户也可自己定义。 操作：选择模具材料 过滤网初始温度/热传系数 如果已知模具温度，直接填入温度。FLOW-3D 采用温度单位为 K ，因此必须把摄氏度 + 273.15。 指定热传系数 指定初始温度 结果 流体经过过滤网的状态 * * 第四章、FLOW-3D 多孔介质模型 FLOW-3D? v9.4 Examples of Porous Media * User Training Sponge Wire Screen Streambed Sinter Metal Filter Paper Tube Bundle 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 Types of Porous Objects in FLOW-3D * User Training Porous Media Modeling Theory List of topics 介绍达西定律（Darcy law） 介绍 FLOW-3D?拖曳力模型(drag model) 介绍饱和多孔介质模型 (the saturated porous media model) 介绍拖曳力系数与渗透率的关系 (drag coefficient and permeability) 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 (the unsaturated porous media model) 达西定律（Darcy Law） Q : units of volume per time (e.g., m3/s) A : cross-sectional area ( Pb ? Pa ) : the pressure drop μ : dynamic viscosity Κ : the permeability of the medium (units of area, e.g. m2) L : the length 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