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1、Tutorial 7. Modeling Flow Through Porous MediaIntroductionMany industrial applications involve the modeling of ow through porous media, such as _lters, catalyst beds, and packing. This tutorial illustrates how to set up and solve a problem involving gas ow through porous media.The industrial problem
2、 solved here involves gas ow through a catalytic converter. Catalytic converters are commonly used to purify emissions from gasoline and diesel engines by converting environmentally hazardous exhaust emissions to acceptable substances.Examples of such emissions include carbon monoxide (CO), nitrogen
3、 oxides (NOx), and unburned hydrocarbon fuels. These exhaust gas emissions are forced through a substrate, which is a ceramic structure coated with a metal catalyst such as platinum or palladium.The nature of the exhaust gas ow is a very important factor in determining the performance of the catalyt
4、ic converter. Of particular importance is the pressure gradient and velocity distribution through the substrate. Hence CFD analysis is used to designe_cient catalytic converters: by modeling the exhaust gas ow, the pressure drop and the uniformity of ow through the substrate can be determined. In th
5、is tutorial, FLUENTis used to model the ow of nitrogen gas through a catalytic converter geometry, so that the ow _eld structure may be analyzed.This tutorial demonstrates how to do the following:_ Set up a porous zone for the substrate with appropriate resistances._ Calculate a solution for gas ow
6、through the catalytic converter using the pressurebased solver._ Plot pressure and velocity distribution on speci_ed planes of the geometry._ Determine the pressure drop through the substrate and the degree of non-uniformityof ow through cross sections of the geometry using X-Y plots and numerical r
7、eports.许多工业应用都涉及通过多孔介质（如过滤器，催化剂床和填料）的流动模型。本教程说明如何建立和解决涉及气体通过多孔介质的问题。这里解决的工业问题涉及通过催化转换器的气体流量。催化转化器通常用于通过将对环境有害的废气排放物转化为可接受的物质来净化汽油和柴油发动机的排放物。这种排放的例子包括一氧化碳（CO），氮氧化物（NOx）和未燃烧的碳氢化合物燃料。这些废气排放物被迫通过衬底，该衬底是涂覆有诸如铂或钯的金属催化剂的陶瓷结构。排气流量的性质是决定催化转化器性能的一个非常重要的因素。特别重要的是通过基底的压力梯度和速度分布。因此，使用CFD分析来设计催化转换器：通过对排气流量进行建模，可以
8、确定通过基板的流量的压降和流量的均匀性。在本教程中，FLUENT用于模拟通过催化转化器几何形状的氮气流量，从而可以分析流量结构。本教程演示了如何执行以下操作：_设置具有适当阻力的基材的多孔区域。_使用基于压力的解算器计算通过催化转化器的气体流量的解决方案。_绘制几何体特定平面上的压力和速度分布。_确定通过基材的压降和不均匀的程度通过使用X-Y图和数字报告的几何横截面的流量。PrerequisitesThis tutorial assumes that you are familiar with the menu structure in FLUENT and thatyou have comp
9、leted Tutorial 1. Some steps in the setup and solution procedure will notbe shown explicitly.本教程假设您熟悉FLUENT中的菜单结构您已完成教程1.设置和解决方案过程中的某些步骤不会明确显示。Problem DescriptionThe catalytic converter modeled here is shown in Figure 7.1. The nitrogen ows inthrough the inlet with a uniform velocity of 22.6 m/s, pas
10、ses through a ceramic monolithsubstrate with square shaped channels, and then exits through the outlet.图7.1所示为这里建模的催化转化器。氮流入以22.6m / s的均匀速度通过入口，穿过陶瓷整体具有方形通道的基底，然后通过出口离开。While the ow in the inlet and outlet sections is turbulent, the ow through the substrate is laminar and is characterized by inertia
11、l and viscous loss coe_cients in the ow (X) direction. The substrate is impermeable in other directions, which is modeled using losscoe_cients whose values are three orders of magnitude higher than in the X direction.当入口和出口段的湍流是湍流时，通过基底的流动是层流的，并且在流动（X）方向上具有惯性和粘性损失系数。 基材在其他方向上是不透水的，其使用的损失系数比在X方向上高三个数
12、量级。Setup and SolutionPreparation1. Download porous.zip from the Fluent Inc. User Services Center or copy it fromthe FLUENT documentation CD to your working folder (as described in Tutorial 1).2. Unzip porous.zip.catalytic converter.msh can be found in the porous folder created after unzippingthe _le
13、.3. Start the 3D (3d) version of FLUENT.1.从Fluent Inc.用户服务中心下载porous.zip或从中复制FLUENT文档光盘放到您的工作文件夹中（如教程1所述）。2.解压多孔.zip。催化转换器.msh可以在解压后形成的多孔文件夹中找到。3.启动FLUENT的3D（3D）版本。Step 1: Grid1. Read the mesh _le (catalytic converter.msh).File ! Read !Case.2. Check the grid.Grid !CheckFLUENT will perform various ch
14、ecks on the mesh and report the progress in the console. Make sure that the minimum volume reported is a positive number.3. Scale the grid.Grid !Scale. (a) Select mm from the Grid Was Created In drop-down list.(b) Click the Change Length Units button. All dimensions will now be shown in millimeters.
15、(c) Click Scale and close the Scale Grid panel.4. Display the mesh. Display !Grid.(a) Make sure that inlet, outlet, substrate-wall, and wall are selected in the Surfaces selection list.(b) Click Display.(c) Rotate the view and zoom in to get the display shown in Figure 7.2.(d) Close the Grid Display
16、 panel.The hex mesh on the geometry contains a total of 34,580 cells.Step 2: Models1. Retain the default solver settings. De_ne ! Models !Solver.2. Select the standard k-_ turbulence model.De_ne ! Models !Viscous.Step 3: Materials1. Add nitrogen to the list of uid materials by copying it from the Fluent Datab
