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1、. .经过痛苦的一段经历，终于将局部问题真相大白，为了使保位不再经过我之痛苦，现在将本人多孔介质经验公布如下，希望各位能加精：1。Gambit中划分网格之后，定义需要做为多孔介质的区域为fluid,与缺省的fluid分别开来，再定义其名称，我习惯将名称定义为porous;2。在fluent中定义边界条件define-boundary condition-porous(刚定义的名称)，将其设置边界条件为fluid,点击set按钮即弹出与fluid边界条件一样的对话框，选中porous zone与laminar复选框,再点击porous zone标签即出现一个带有滚动条的界面；3。porous z
2、one设置方法：1）定义矢量：二维定义一个矢量，第二个矢量方向不用定义，是与第一个矢量方向正交的；三维定义二个矢量，第三个矢量方向不用定义，是与第一、二个矢量方向正交的；（如何知道矢量的方向：打开grid图，看看X,Y,Z的方向，如果是X向，矢量为1,0,0,同理Y向为0,1,0，Z向为0,0,1,如果所需要的方向与坐标轴正向相反，则定义矢量为负）圆锥坐标与球坐标请参考fluent帮助。2）定义粘性阻力1/a与部阻力C2：请参看本人上一篇博文“终于搞清fluent中多孔粘性阻力与部阻力的计算方法”，此处不赘述；3）如果了定义粘性阻力1/a与部阻力C2,就不用定义C1与C0，因为这是两种不同的定
3、义方法，C1与C0只在幂率模型中出现，该处保持默认就行了；4）定义孔隙率porousity，默认值1表示全开放，此值按实验测值填写即可。完了，其他设置与普通k-e或RSM一样。总结一下，与君共享!Tutorial 7. Modeling Flow Through Porous MediaIntroductionMany industrial applications involve the modeling of flow through porous media, suchas filters, catalyst beds, and packing. This tutorial illust
4、rates how to set up and solve aproblem involving gas flow through porous media.The industrial problem solved here involves gas flow through a catalytic converter. Catalyticconverters are commonly used to purify emissions from gasoline and diesel enginesby converting environmentally hazardous exhaust
5、 emissions to acceptable substances.Examples of such emissions include carbon monoxide (CO), nitrogen oxides (NOx), andunburned 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 na
6、ture of the exhaust gas flow is a very important factor in determining the performanceof the catalytic converter. Of particular importance is the pressure gradientand velocity distribution through the substrate. Hence CFD analysis is used to designefficient catalytic converters: by modeling the exha
7、ust gas flow, the pressure drop andthe uniformity of flow through the substrate can be determined. In this tutorial, FLUENTis used to model the flow of nitrogen gas through a catalytic converter geometry, so thatthe flow field structure may be analyzed.This tutorial demonstrates how to do the follow
8、ing:_ Set up a porous zone for the substrate with appropriate resistances._ Calculate a solution for gas flow through the catalytic converter using the pressurebasedsolver._ Plot pressure and velocity distribution on specified planes of the geometry._ Determine the pressure drop through the substrat
9、e and the degree of non-uniformityof flow through cross sections of the geometry using X-Y plots and numerical reports.Problem DescriptionThe catalytic converter modeled here is shown in Figure 7.1. The nitrogen flows inthrough the inlet with a uniform velocity of 22.6 m/s, passes through a ceramic
10、monolithsubstrate with square shaped channels, and then exits through the outlet.While the flow in the inlet and outlet sections is turbulent, the flow through the substrateis laminar and is characterized by inertial and viscous loss coefficients in the flow (X)direction. The substrate is impermeabl
11、e in other directions, which is modeled using losscoefficients whose values are three orders of magnitude higher than in the X direction.Setup and SolutionStep 1: Grid1. Read the mesh file (catalytic converter.msh).File /Read /Case.2. Check the grid.Grid /CheckFLUENT will perform various checks on t
12、he mesh and report the progress in theconsole. 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.(c) Click Sc
13、ale 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 Surfacesselection 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 panel.The hex
14、 mesh on the geometry contains a total of 34,580 cells.Step 2: Models1. Retain the default solver settings.Define /Models /Solver.2. Select the standard k- turbulence model.Define/ Models /Viscous.Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Databasef
15、or materials.Define /Materials.(a) Click the Fluent Database. button to open the Fluent Database Materialspanel.i. Select nitrogen (n2) from the list of Fluent Fluid Materials.ii. Click Copy to copy the information for nitrogen to your list of fluid materials.iii. Close the Fluent Database Materials panel.(b) Close the Materials panel.Step 4: Boundary Conditions. Define /Boundary Conditions.1. Set the boundary conditions for the fluid (fluid).(a) Select nitrogen from the Material Name drop-down list.(b) Click OK to close the Fl
