1、in Equation7.19-1, or7.19-2） and the inertial resistance coefficients （7.19-2）, and define the direction vectors for which they apply. Alternatively, specify the coefficients for the power-law model.7. Specify the porosity of the porous medium.8. Select the material contained in the porous medium （r
2、equired only for models that include heat transfer）. Note that the specific heat capacity, for the selected material in the porous zone can only be entered as a constant value.9. Set the volumetric heat generation rate in the solid portion of the porous medium （or any other sources, such as mass or
3、momentum）. （optional）10. Set any fixed values for solution variables in the fluid region （optional）.11. Suppress the turbulent viscosity in the porous region, if appropriate.12. Specify the rotation axis and/or zone motion, if relevant.Methods for determining the resistance coefficients and/or perme
4、ability are presented below. If you choose to use the power-law approximation of the porous-media momentum source term, you will enter the coefficientsand7.19-3instead of the resistance coefficients and flow direction.You will set all parameters for the porous medium in theFluidpanel（Figure7.19.1）,
5、which is opened from theBoundary Conditions（as described in Section7.1.4）.Figure 7.19.1:ThePanel for a Porous ZoneDefining the Porous ZoneAs mentioned in Section7.1, a porous zone is modeled as a special type of fluid zone. To indicate that the fluid zone is a porous region, enable thePorous Zoneopt
6、ion in thepanel. The panel will expand to show the porous media inputs （as shown in Figure7.19.1）.Defining the Porous Velocity FormulationSolverpanel contains aPorous Formulationregion where you can instructFLUENTto use either a superficial or physical velocity in the porous medium simulation. By de
7、fault, the velocity is set toSuperficial Velocity. For details about using thePhysical Velocityformulation, see Section7.19.7.Defining the Fluid Passing Through the Porous MediumTo define the fluid that passes through the porous medium, select the appropriate fluid in theMaterial Namedrop-down list
8、in thepanel. If you want to check or modify the properties of the selected material, you can clickEdit.to open theMaterialpanel; this panel contains just the properties of the selected material, not the full contents of the standardMaterialspanel.If you are modeling species transport or multiphase f
9、low, thelist will not appear in thepanel. For species calculations, the mixture material for all fluid/porous zones will be the material you specified in theSpecies Modelpanel. For multiphase flows, the materials are specified when you define the phases, as described in Section23.10.3.Enabling React
10、ions in a Porous ZoneIf you are modeling species transport with reactions, you can enable reactions in a porous zone by turning on theReactionoption in thepanel and selecting a mechanism in theReaction Mechanismdrop-down list.If your mechanism contains wall surface reactions, you will also need to s
11、pecify a value for theSurface-to-Volume Ratio. This value is the surface area of the pore walls per unit volume （）, and can be thought of as a measure of catalyst loading. With this value,can calculate the total surface area on which the reaction takes place in each cell by multiplyingby the volume
12、of the cell. See Section14.1.4for details about defining reaction mechanisms. See Section14.2for details about wall surface reactions.Including the Relative Velocity Resistance FormulationPrior to6.3, cases with moving reference frames used the absolute velocities in the source calculations for iner
13、tial and viscous resistance. This approach has been enhanced so that relative velocities are used for the porous source calculations （Section7.19.2）. Using theRelative Velocity Resistance Formulationoption （turned on by default） allows you to better predict the source terms for cases involving movin
14、g meshes or moving reference frames （MRF）. This option works well in cases with non-moving and moving porous media. Note thatwill use the appropriate velocities （relative or absolute）, depending on your case setup.Defining the Viscous and Inertial Resistance CoefficientsThe viscous and inertial resi
15、stance coefficientsare both defined in the same manner. The basic approach for defining the coefficients using a Cartesian coordinate system is to define one direction vector in 2D or two direction vectors in 3D, and then specify the viscous and/or inertial resistance coefficients in each direction.
16、 In 2D, the second direction, which is not explicitly defined, is normal to the plane defined by the specified direction vector and thedirection vector. In 3D, the third direction is normal to the plane defined by the two specified direction vectors. For a 3D problem, the second direction must be no
17、rmal to the first. If you fail to specify two normal directions, the solver will ensure that they are normal by ignoring any component of the second direction that is in the first direction. You should therefore be certain that the first direction is correctly specified.You can also define the visco
18、us and/or inertial resistance coefficients in each direction using a user-defined function （UDF）. The user-defined options become available in the corresponding drop-down list when the UDF has been created and loaded intoFLUENT. Note that the coefficients defined in the UDF must utilize theDEFINE_PR
19、OFILEmacro. For more information on creating and using user-defined function, see the separate UDF Manual.If you are modeling axisymmetric swirling flows, you can specify an additional direction component for the viscous and/or inertial resistance coefficients. This direction component is always tan
20、gential to the other two specified directions. This option is available for both density-based and pressure-based solvers.In 3D, it is also possible to define the coefficients using a conical （or cylindrical） coordinate system, as described below.Note that the viscous and inertial resistance coeffic
21、ients are generally based on the superficial velocity of the fluid in the porous media.The procedure for defining resistance coefficients is as follows:Define the direction vectors. To use a Cartesian coordinate system, simply specify theDirection-1 Vectorand, for 3D, theDirection-2 Vector. The unsp
22、ecified direction will be determined as described above. These direction vectors correspond to the principle axes of the porous media.For some problems in which the principal axes of the porous medium are not aligned with the coordinate axes of the domain, you may not know a priori the direction vec
23、tors of the porous medium. In such cases, the plane tool in 3D （or the line tool in 2D） can help you to determine these direction vectors.（a） Snap the plane tool （or the line tool） onto the boundary of the porous region. （Follow the instructions in Section27.6.1or27.5.1for initializing the tool to a
24、 position on an existing surface.）（b） Rotate the axes of the tool appropriately until they are aligned with the porous medium.（c） Once the axes are aligned, click on theUpdate From Plane ToolUpdate From Line Toolbutton in thepanel.will automatically set theDirection-1 Vectorto the direction of the r
25、ed arrow of the tool, and （in 3D） theDirection-2 Vectorto the direction of the green arrow. To use a conical coordinate system （e.g., for an annular, conical filter element）, follow the steps below. This option is available only in 3D cases.Turn on theConicaloption.Specify theCone Axis VectorPoint o
26、n Cone Axis. The cone axis is specified as being in the direction of the（unit vector）, and passing through thePoint on Cone Axis. The cone axis may or may not pass through the origin of the coordinate system.Set theCone Half Angle（the angle between the cones axis and its surface, shown in Figure7.19
27、.2）. To use a cylindrical coordinate system, set theCone Half Angleto 0.Figure 7.19.2:Cone Half AngleFor some problems in which the axis of the conical filter element is not aligned with the coordinate axes of the domain, you may not know a priori the direction vector of the cone axis and coordinate
28、s of a point on the cone axis. In such cases, the plane tool can help you to determine the cone axis vector and point coordinates. One method is as follows:Select a boundary zone of the conical filter element that is normal to the cone axis vector in the drop-down list next to theSnap to Zonebutton.
29、Click on thebutton.will automatically snap the plane tool onto the boundary. It will also set theand thePoint on Cone Axis. （Note that you will still have to set theyourself.）An alternate method is as follows: the plane tool onto the boundary of the porous region. （Follow the instructions in Section
