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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与内部阻力C2：请参看本人上一篇博文“终于搞清fluent中多孔粘性阻力与内部阻力的计算方法”，此处不赘述；
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3）如果了定义粘性阻力1/a与内部阻力C2,就不用定义C1与C0，因为这是两种不同的定义方法，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相同。总结一下，与君共享!
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Tutorial 7. Modeling Flow Through Porous Media
Introduction
Many industrial applications involve the modeling of flow through porous media, such as filters, catalyst beds, and packing. This tutorial illustrates how to set up and solve a problem involving gas flow through porous media.
The industrial problem solved here involves gas flow 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 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 flow is a very important factor in determining the performance of the catalytic converter. Of particular importance is the pressure
gradient and velocity distribution through the substrate. Hence CFD analysis is used to design efficient catalytic converters: by modeling the exhaust gas flow, the pressure drop and the uniformity of flow through the substrate can be determined. In this tutorial, FLUENT is used to model the flow of nitrogen gas through a catalytic converter geometry, so that the flow field structure may be analyzed.
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This tutorial demonstrates how to do the following:
_ Set up a porous zone for the substrate with appropriate resistances.
_ Calculate a solution for gas flow through the catalytic converter using the pressure based solver.
_ Plot pressure and velocity distribution on specified planes of the geometry.
_ Determine the pressure drop through the substrate and the degree of non-uniformity of flow through cross sections of the geometry using X-Y plots and numerical reports.
Problem Description
The catalytic converter modeled here is shown in Figure 7.1. The nitrogen flows in through the inlet with a uniform velocity of 22.6 m/s, passes through a ceramic monolith substrate 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
substrate is laminar and is characterized by inertial and viscous loss coefficients in the flow (X) direction. The substrate is impermeable in other directions, which is modeled using loss coefficients whose values are three orders of magnitude higher than in the X direction.
Setup and Solution Step 1: Grid
1. Read the mesh file (catalytic converter.msh). File /Read /Case...
2. Check the grid. Grid /Check
FLUENT will perform various checks 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.
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