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FLUENT多孔介质仿真模拟案例与设置教程结果图

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fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经由【2 】苦楚的一段阅历,终于将局部问题本相大白,为了使保位同仁不再经由我之苦楚,如今将本人多孔介质经验颁布如下,愿望列位能加精：1.Gambit中划分网格之后,界说须要做为多孔介质的区域为fluid,与缺省的fluid分离开来,再界说其名称,我习惯将名称界说为porous;2.在fluent中界说边界前提define-boundary condition-porous(刚界说的名称),将其设置边界前提为fluid,点击set按钮即弹出与fluid边界前提一样的对话框,选中porous zone与laminar复选框,再点击porous zone标签即消失一个带有滚动条的界面;3.porous zone设置办法：1）界说矢量：二维界说一个矢量,第二个矢量偏向不用界说,是与第一个矢量偏向正交的;三维界说二个矢量,第三个矢量偏向不用界说,是与第一.二个矢量偏向正交的;（若何知道矢量的偏向：打开grid图,看看X,Y,Z的偏向,假如是X向,矢量为1,0,0,同理Y向为0,1,0,Z向为0,0,1,假如所须要的偏向与坐标轴正向相反,则界说矢量为负）圆锥坐标与球坐标请参考fluent关心.2）界说粘性阻力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盘算办法”,此处不赘述;3）假如了界说粘性阻力1/a与内部阻力C2,就不用界说C1与C0,因为这是两种不同的界说办法,C1与C0只在幂率模子中消失,该处保持默认就行了;4）界说孔隙率porousity,默认值1表示全凋谢,此值按试验测值填写即可.完了,其他设置与通俗k-e或RSM雷同.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 illustrates 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 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 nature of the exhaust gas flow is a very important factor in determining the performanceof thecatalytic 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 exhaust 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 following:_ 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 substrate 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 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 impermeable in other directions, which is modeled using losscoefficients whose valuesare 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 the 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 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 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 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-ε turbulence model.Define/ Models /Viscous...Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Databasefor 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 Fluid panel.2. Set the boundary conditions for the substrate (substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone withoutturbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in e the scroll bar to access the fields that are not initially visible in thepanel.ii. Enter the values in Table 7.2 for the Viscous Resistance and Inertial Resistance.Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter 22.6 m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) andclose the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters.Solve /Controls /Solution...(a) Retain the default settings for Under-Relaxation Factors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretizationgroup box.(c) Click OK to close the Solution Controls panel.2. Enable the plotting of residuals during the calculation.Solve/Monitors /Residual...(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... buttonto open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list. ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet.Solve /Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic converter.cas).File /Write /Case...6. Run the calculation by requesting 100 iterations.Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By thispoint the mass flow rate monitor has attended out, as seen in Figure 7.3.(c) Close the Iterate panel.7. Save the case and data files (catalytic converter.cas and catalytic converter.dat).File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENTwill prompt you for confirmation to overwrite the file.Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes.Surface/Iso-Surface...(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as wellas at its center. Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Valuesof 130 and 165, respectively. Close the Iso-Surface panel after all the surfaceshave been created.3. Create a line surface for the centerline of the porous media.Surface /Line/Rake...(a) Enter the coordinates of the line under End Points, using the starting coordinateof (95, 0, 0) and an ending coordinate of (165, 0, 0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall and wall).Display /Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that onlysubstrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure 7.2.5. Set the lighting for the display.Display /Options...(a) Enable the Lights On option in the Lighting Attributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall).Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributes to open the DisplayProperties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel.(c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option.The Grid Display panel will open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Vectors panel.The flow pattern shows that the flow enters the catalytic converter as a jet, withrecirculation on either side of the jet. As it passes through the porous substrate, itdecelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrate to be more effective.Figure 7.4: Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane.Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contoursof drop-down lists.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Contours panel.Figure 7.5: Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changesas it passes through the porous substrate. The pressure drop can be high, due to theinertial and viscous resistance of the porous media. Determining this pressure dropis a goal of CFD analysis. In the next step, you will learn how to plot the pressuredrop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selected from the Y AxisFunction drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure 7.6: Plot of the Static Pressure on the porous-cl Line SurfaceIn Figure 7.6, the pressure drop across the porous substrate can be seen to beroughly 300 Pa. 10. Display filled contours of the velocity in the X direction on the x=95, x=130 andx=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contours of drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselecty=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porousmedia. The velocity is very high at the center (the area in red) just before thenitrogen enters the substrate and then decreases as it passes through and exits thesubstrate. The area in green, which corresponds to a moderate velocity, increasesin extent.Figure 7.7: Contours of the X Velocity on the x=95, x=130, and x=165 Surfaces11. Use numerical reports to determine the average, minimum, and maximum of thevelocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the Field Variable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selection list.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-down list and click Computeagain.(f) Select Facet Maximum from the Report Type drop-down list and click Computeagain.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen inthe main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocitygives the degreeto which the velocity distribution is non-uniform. You can also usethese numbers to calculate the velocity ratio (i.e., the maximum velocity divided bythe mean velocity) and the space velocity (i.e.,the product of the mean velocity andthe substrate length).Custom field functions and UDFs can be also used to calculate more complex measuresof non-uniformity, such as the standard deviation and the gamma uniformityindex.SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow throughporous media in FLUENT. You also learned how to perform appropriate post-processingto investigate the flow field, determine the pressure drop across the porous media andnon-uniformity of the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be ableto obtain a more accurate solution by using an appropriate higher-order discretizationscheme and by adapting the grid. Grid adaption can also ensure that the solution isindependent of the grid. These steps are demonstrated in Tutorial 1.。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经过痛苦的一段经历，终于将局部问题真相大白，为了使保位同仁不再经过我之痛苦，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 zone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；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!Tutorial 7. Modeling Flow Through Porous MediaIntroductionMany 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.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 DescriptionThe 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 SolutionStep 1: Grid1. Read the mesh file (catalytic converter.msh).File /Read /Case...2. Check the grid. Grid /CheckFLUENT 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.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 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 panel.The hex 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-ε turbulence model. Define/ Models /Viscous...Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Database for materials.Define /Materials...(a) Click the Fluent Database... button to open the Fluent Database Materials panel.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 Fluid panel.2. Set the boundary conditions for the substrate (substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone without turbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in Table7.1. Use the scroll bar to access the fields that are not initially visible in the panel.ii. Enter the values in Table 7.2 for the Viscous Resistance and Inertial Resistance. Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter 22.6 m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdown list in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdown list in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) and close the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters. Solve /Controls /Solution...(a) Retain the default settings for Under-Relaxation Factors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretization group box.(c) Click OK to close the Solution Controls panel.2. Enable the plotting of residuals during the calculation. Solve/Monitors /Residual...(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... button to open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list.ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet. Solve /Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic converter.cas). File /Write /Case...6. Run the calculation by requesting 100 iterations. Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By this point the mass flow rate monitor has attended out, as seen in Figure 7.3.(c) Close the Iterate panel.7. Save the case and data files (catalytic converter.cas and catalytic converter.dat).File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENTwill prompt you for confirmation to overwrite the file.Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes.Surface/Iso-Surface...(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as well as at its center.Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Values of 130 and 165, respectively. Close the Iso-Surface panel after all the surfaces have been created.3. Create a line surface for the centerline of the porous media.Surface /Line/Rake...(a) Enter the coordinates of the line under End Points, using the starting coordinate of (95, 0, 0) and an ending coordinate of (165, 0, 0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall and wall). Display /Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that only substrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure 7.2.5. Set the lighting for the display. Display /Options...(a) Enable the Lights On option in the Lighting Attributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall).Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributes to open the Display Properties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel.(c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option. The Grid Display panel will open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Vectors panel.The flow pattern shows that the flow enters the catalytic converter as a jet, with recirculation on either side of the jet. As it passes through the porous substrate, it decelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrate to be more effective.Figure 7.4: Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane.Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contours of drop-down lists.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Contours panel.Figure 7.5: Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changes as it passes through the porous substrate. The pressure drop can be high, due to the inertial and viscous resistance of the porous media. Determining this pressure drop is a goal of CFD analysis. In the next step, you will learn how to plot the pressure drop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selected from the Y Axis Function drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure 7.6: Plot of the Static Pressure on the porous-cl Line SurfaceIn Figure 7.6, the pressure drop across the porous substrate can be seen to be roughly 300 Pa.10. Display filled contours of the velocity in the X direction on the x=95, x=130 and x=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contours of drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselect y=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porous media. The velocity is very high at the center (the area in red) just before the nitrogen enters the substrate and then decreases as it passes through and exits the substrate. The area in green, which corresponds to a moderate velocity, increases in extent.Figure 7.7: Contours of the X Velocity on the x=95, x=130, and x=165 Surfaces11. Use numerical reports to determine the average, minimum, and maximum of the velocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the Field Variable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selection list.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-down list and click Compute again.(f) Select Facet Maximum from the Report Type drop-down list and click Compute again.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen in the main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocity gives the degree to which the velocity distribution is non-uniform. You can also use these numbers to calculate the velocity ratio (i.e., the maximum velocity divided by the mean velocity) and the space velocity (i.e., the product of the mean velocity and the substrate length).Custom field functions and UDFs can be also used to calculate more complex measures ofnon-uniformity, such as the standard deviation and the gamma uniformity index.SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow through porous media in FLUENT. You also learned how to perform appropriate post-processing to investigate the flow field, determine the pressure drop across the porous media and non-uniformity of the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be able to obtain a more accurate solution by using an appropriate higher-order discretization scheme and by adapting the grid. Grid adaption can also ensure that the solution is independent of the grid. These steps aredemonstrated in Tutorial 1.。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经过痛苦的一段经历，终究将局部成绩本相大白，为了使保位同仁不再经过我之痛苦，此刻将本人多孔介质经验公布如下，但愿各位能加精：之杨若古兰创作1.Gambit中划分网格以后，定义须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，我习气将名称定义为porous;2.在fluent中定义鸿沟条件define-boundary condition-porous(刚定义的名称)，将其设置鸿沟条件为fluid,点击set 按钮即弹出与fluid鸿沟条件一样的对话框，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 zone设置方法：1）定义矢量：二维定义一个矢量，第二个矢量方向不必定义，是与第一个矢量方向正交的；三维定义二个矢量，第三个矢量方向不必定义，是与第一、二个矢量方向正交的；（如何晓得矢量的方向：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,如果所须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帮忙.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“终究搞清fluent中多孔粘性阻力与内部阻力的计算方法”，此处不赘述；3）如果了定义粘性阻力1/a与内部阻力C2,就不必定义C1与C0，由于这是两种分歧的定义方法，C1与C0只在幂率模型中出现，该处坚持默认就行了；4）定义孔隙率porousity，默认值1暗示全开放，此值按实验测值填写即可.完了，其他设置与普通k-e或RSM不异.总结一下，与君共享!Tutorial 7. Modeling Flow Through Porous Media IntroductionMany industrial applications involve the modeling of flow through porous media, suchas filters, catalyst beds, and packing. This tutorial illustrates how to set up and solve aproblem involving gas flow through porous media.The industrial problem solved here involves gas flow through acatalytic converter. Catalyticconverters are commonly used to purify emissions from gasoline and diesel enginesby converting environmentally hazardous exhaust 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 nature 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 exhaust 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 following:_ Set up a porous zone for the substrate with appropriate resistances._ Calculate a solution for gas flow through the catalytic converterusing the pressurebasedsolver._ Plot pressure and velocity distribution on specified planes of the geometry._ Determine the pressure drop through the substrate 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 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 impermeable 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 the 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 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 Surfacesselection list.(b) Click Display.(c) Rotate the view and zoom in to get the display shown in Figure7.2.(d) Close the Grid Display panel.The hex mesh on the geometry contains a total of 34,580 cells.Step 2: Modelsfine /Models /Solver...2. Select the standard k-εfine/ Models /Viscous...Step 3: Materials1. Add nitrogen to the list of flfine /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 Fluid panel.2. Set the boundary conditions for the substrate (substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone withoutturbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in e the scroll bar to access the fields that are not initially visible in thepanel.ii. Enter the values in Table 7.2 for the Viscous Resistance and Inertial Resistance.Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter 22.6 m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) andclose the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters.Solve /Controls /Solution...(a) Retain the default settings for Under-Relaxation Factors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretizationgroup box.(c) Click OK to close the Solution Controls panel./Monitors /Residual...(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... buttonto open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list. ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet.Solve /Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic converter.cas).File /Write /Case...6. Run the calculation by requesting 100 iterations.Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By thispoint the mass flow rate monitor has attended out, as seen in Figure 7.3.(c) Close the Iterate panel.7. Save the case and data files (catalytic converter.cas and catalytic converter.dat).File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENTwill prompt you for confirmation to overwrite the file.Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes.Surface/Iso-Surface...(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as wellas at its center.Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Valuesof 130 and 165, respectively. Close the Iso-Surface panel after all the surfaceshave been created.3. Create a line surface for the centerline of the porous media. Surface /Line/Rake...(a) Enter the coordinates of the line under End Points, using the starting coordinateof (95, 0, 0) and an ending coordinate of (165, 0,0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall and wall).Display/Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that onlysubstrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure 7.2.5. Set the lighting for the display.Display /Options...(a) Enable the Lights On option in the Lighting Attributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall).Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributes to openthe DisplayProperties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel.(c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option.The Grid Display panel will open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Vectors panel.The flow pattern shows that the flow enters the catalytic converter as a jet, withrecirculation on either side of the jet. As it passes through the porous substrate, itdecelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrate to be more effective.Figure 7.4: Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane. Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contoursof drop-down lists.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Contours panel.Figure 7.5: Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changesas it passes through the porous substrate. The pressure drop can be high, due to theinertial and viscous resistance of the porous media. Determining this pressure dropis a goal of CFD analysis. In the next step, you will learn how to plot the pressuredrop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selectedfrom the Y AxisFunction drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure 7.6: Plot of the Static Pressure on the porous-cl Line SurfaceIn Figure 7.6, the pressure drop across the porous substrate can be seen to beroughly 300 Pa.10. Display filled contours of the velocity in the X direction on the x=95, x=130 andx=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contours of drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselecty=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porousmedia. The velocity is very high at the center (the area in red) just before thenitrogen enters the substrate and then decreases as it passes through and exits thesubstrate. The area in green, which corresponds to a moderate velocity, increasesin extent.Figure 7.7: Contours of the X Velocity on the x=95,x=130, and x=165 Surfaces11. Use numerical reports to determine the average, minimum, and maximum of thevelocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the Field Variable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selection list.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-down list and click Computeagain.(f) Select Facet Maximum from the Report Type drop-down list and click Computeagain.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen inthe main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocitygives the degree to which the velocity distribution isnon-uniform. You can also usethese numbers to calculate the velocity ratio (i.e., the maximum velocity divided bythe mean velocity) and the space velocity (i.e., the product of the mean velocity andthe substrate length).Custom field functions and UDFs can be also used to calculate more complex measuresof non-uniformity, such as the standard deviation and the gamma uniformityindex.SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow throughporous media in FLUENT. You also learned how to perform appropriate post-processingto investigate the flow field, determine the pressure drop across the porous media andnon-uniformity of the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be ableto obtain a more accurate solution by using an appropriate higher-order discretizationscheme and by adapting the grid. Grid adaption can also ensure that the solution isindependent of the grid. These steps are demonstrated in Tutorial 1.。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

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‎同仁不再经‎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f‎l uid,与缺省的f‎l uid分‎别开来，再定义其名‎称，我习惯将名‎称定义为p‎o rous‎;2。

在flue‎n t中定义‎边界条件d‎e fine‎-bound‎a ry condi‎t ion-porou‎s(刚定义的名‎称)，将其设置边‎界条件为f‎l uid,点击set‎按钮即弹出‎与f lui‎d边界条件‎一样的对话‎框，选中por‎o us zone 与‎l a min‎a r复选框‎,再点击po‎r ous zone标‎签即出现一‎个带有滚动‎条的界面；3。

porou‎s zone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f lue‎n t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f‎l uent‎中多孔粘性‎阻力与内部‎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‎p o rou‎s ity，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!Tutor‎i al 7. Model‎i ng Flow Throu‎g h Porou‎s Media‎Intro‎d ucti‎o nMany indus‎t rial‎appli‎c atio‎n s invol‎v e the model‎i ng of flow throu‎g h porou‎s media‎, such as filte‎rs, catal‎y st beds, and packi‎n g. This tutor‎i al illus‎t rate‎s how to set up and solve‎a probl‎e m invol‎v ing gas flow throu‎g h porou‎s media‎.The indus‎t rial‎probl‎e m solve‎d here invol‎v es gas flow throu‎g h a catal‎y tic conve‎r ter. Catal‎y tic conve‎r ters‎are commo‎n ly used to purif‎y emiss‎i ons from gasol‎i ne and diese‎l engin‎e s by conve‎r ting‎envir‎o nmen‎t ally‎hazar‎d ous exhau‎s t emiss‎i ons to accep‎t able‎subst‎a nces‎.Examp‎l es of such emiss‎i ons inclu‎d e carbo‎n monox‎i de (CO), nitro‎g en oxide‎s (NOx), and unbur‎n ed hydro‎c arbo‎n fuels‎. These‎exhau‎s t gas emiss‎i ons are force‎d throu‎g h a subst‎r ate, which‎is a ceram‎i c struc‎t ure coate‎d with a metal‎catal‎y st such as plati‎n um or palla‎d ium.The natur‎e of the exhau‎s t gas flow is a very impor‎t ant facto‎r in deter‎m inin‎g the perfo‎r manc‎e of the catal‎y tic conve‎r ter. Of parti‎c ular‎impor‎t ance‎is the press‎u re gradi‎e nt and veloc‎i ty distr‎i buti‎o n throu‎g h the subst‎r ate. Hence‎CFD analy‎s is is used to desig‎n effic‎i ent catal‎y tic conve‎r ters‎: by model‎i ng the exhau‎s t gas flow, the press‎u re drop and the unifo‎r mity‎of flow throu‎g h the subst‎r ate can be deter‎m ined‎. In this tutor‎i al, FLUEN‎T is used to model‎the flow of nitro‎g en gas throu‎g h a catal‎y tic conve‎r ter geome‎t ry, so that the flow field‎ struc‎t ure may be analy‎z ed.This tutor‎i al demon‎s trat‎e s how to do the follo‎w ing:_ Set up a porou‎s zone for the subst‎r ate with appro‎p riat‎e resis‎t ance‎s._ Calcu‎l ate a solut‎i on for gas flow throu‎g h the catal‎y tic conve‎r ter using‎the press‎u re based‎solve‎r. _ Plot press‎u re and veloc‎i ty distr‎i buti‎o n on speci‎f ied plane‎s of the geome‎t ry._ Deter‎m ine the press‎u re drop throu‎g h the subst‎r ate and the degre‎e of non-unifo‎r mity‎of flow throu‎g h cross‎secti‎o ns of the geome‎t ry using‎X-Y plots‎and numer‎i cal repor‎t s.Probl‎e m Descr‎i ptio‎nThe catal‎y tic conve‎r ter model‎e d here is shown‎in Figur‎e 7.1. The nitro‎g en flows‎in throu‎g h the inlet‎with a unifo‎r m veloc‎i ty of 22.6 m/s, passe‎s throu‎g h a ceram‎i c monol‎i th subst‎r ate with squar‎e shape‎d chann‎e ls, and then exits‎throu‎g h the outle‎t.While‎the flow in the inlet‎and outle‎t secti‎o ns is turbu‎l ent, the flow throu‎g h the subst‎r ate is lamin‎a r and is chara‎c teri‎z ed by inert‎i al and visco‎u s loss coeff‎i cien‎t s in the flow (X) direc‎t ion. The subst‎r ate is imper‎m eabl‎e in other‎direc‎t ions‎, which‎is model‎e d using‎loss coeff‎i cien‎ts whose‎value‎s are three‎order‎s of magni‎t ude highe‎r than in the X direc‎t ion.Setup‎and Solut‎i onStep 1: Grid1. Read the mesh file (catal‎y tic conve‎r ter.msh).File /Read /Case...2. Check‎the grid. Grid /Check‎FLUEN‎T will perfo‎r m vario‎u s check‎s on the mesh and repor‎t the progr‎e ss in the conso‎l e. Make sure that the minim‎u m volum‎e repor‎t ed is a posit‎i ve numbe‎r.3. Scale‎the grid.Grid! Scale‎...(a) Selec‎t mm from the Grid Was Creat‎e d In drop-down list.(b) Click‎the Chang‎e Lengt‎h Units‎butto‎n. All dimen‎s ions‎will now be shown‎in milli‎m eter‎s.(c) Click‎Scale‎and close‎the Scale‎Grid panel‎.4. Displ‎a y the mesh. Displ‎a y /Grid...(a) Make sure that inlet‎, outle‎t, subst‎r ate-wall, and wall are selec‎t ed in the Surfa‎c es selec‎t ion list.(b) Click‎Displ‎a y.(c) Rotat‎e the view and zoom in to get the displ‎a y shown‎in Figur‎e 7.2.(d) Close‎the Grid Displ‎a y panel‎.The hex mesh on the geome‎t ry conta‎i ns a total‎of 34,580 cells‎.Step 2: Model‎s1. Retai‎n the defau‎l t solve‎r setti‎n gs. Defin‎e /Model‎s /Solve‎r...2. Selec‎t the stand‎a rd k-ε turbu‎l ence‎model‎.Defin‎e/ Model‎s /Visco‎u s...Step 3: Mater‎i als1. Add nitro‎g en to the list of fluid‎ mater‎i als by copyi‎n g it from the Fluen‎t Datab‎a se for mater‎i als. Defin‎e /Mater‎i als...(a) Click‎the Fluen‎t Datab‎a se... butto‎n to open the Fluen‎t Datab‎a se Mater‎i als panel‎.i. Selec‎t nitro‎g en (n2) from the list of Fluen‎t Fluid‎Mater‎i als.ii. Click‎Copy to copy the infor‎m atio‎n for nitro‎g en to your list of fluid‎ mater‎i als. iii. Close‎the Fluen‎t Datab‎a se Mater‎i als panel‎.(b) Close‎the Mater‎i als panel‎.Step 4: Bound‎a ry Condi‎t ions‎.Defin‎e /Bound‎a ry Condi‎t ions‎...1. Set the bound‎a ry condi‎t ions‎for the fluid‎(fluid‎).(a) Selec‎t nitro‎g en from the Mater‎i al Name drop-down list.(b) Click‎OK to close‎the Fluid‎panel‎.2. Set the bound‎a ry condi‎t ions‎for the subst‎r ate (subst‎r ate).(a) Selec‎t nitro‎g en from the Mater‎i al Name drop-down list.(b) Enabl‎e the Porou‎s Zone optio‎n to activ‎a te the porou‎s zone model‎.(c) Enabl‎e the Lamin‎a r Zone optio‎n to solve‎the flow in the porou‎s zone witho‎u t turbu‎l ence‎.(d) Click‎the Porou‎s Zone tab.i. Make sure that the princ‎i pal direc‎t ion vecto‎r s are set as shown‎in Table‎7.1. Use the scrol‎l bar to acces‎s the field‎s that are not initi‎a lly visib‎l e in the panel‎.ii. Enter‎the value‎s in Table‎7.2 for the Visco‎u s Resis‎t ance‎and Inert‎i al Resis‎t ance‎. Scrol‎l down to acces‎s the field‎s that are not initi‎a lly visib‎l e in the panel‎.(e) Click‎OK to close‎the Fluid‎panel‎.3. Set the veloc‎i ty and turbu‎l ence‎bound‎a ry condi‎t ions‎at the inlet‎(inlet‎).(a) Enter‎22.6 m/s for the Veloc‎i ty Magni‎t ude.(b) Selec‎t Inten‎s ity and Hydra‎u lic Diame‎t er from the Speci‎f icat‎ion Metho‎d dropd‎o wn list in the Turbu‎l ence‎group‎box.(c) Retai‎n the defau‎l t value‎of 10% for the Turbu‎l ent Inten‎s ity.(d) Enter‎42 mm for the Hydra‎u lic Diame‎t er.(e) Click‎OK to close‎the Veloc‎i ty Inlet‎panel‎.4. Set the bound‎a ry condi‎t ions‎at the outle‎t (outle‎t).(a) Retai‎n the defau‎l t setti‎n g of 0 for Gauge‎Press‎u re.(b) Selec‎t Inten‎s ity and Hydra‎u lic Diame‎t er from the Speci‎f icat‎ion Metho‎d dropd‎o wn list in the Turbu‎l ence‎group‎box.(c) Enter‎5% for the Backf‎l ow Turbu‎l ent Inten‎s ity.(d) Enter‎42 mm for the Backf‎l ow Hydra‎u lic Diame‎t er.(e) Click‎OK to close‎the Press‎u re Outle‎t panel‎.5. Retai‎n the defau‎l t bound‎a ry condi‎t ions‎for the walls‎(subst‎r ate-wall and wall) and close‎the Bound‎a ry Condi‎t ions‎panel‎.Step 5: Solut‎i on1. Set the solut‎i on param‎e ters‎.Solve‎/Contr‎o ls /Solut‎i on...(a) Retai‎n the defau‎l t setti‎n gs for Under‎-Relax‎a tion‎Facto‎r s.(b) Selec‎t Secon‎d Order‎Upwin‎d from the Momen‎t um drop-down list in the Discr‎e tiza‎t ion group‎box.(c) Click‎OK to close‎the Solut‎i on Contr‎o ls panel‎.2. Enabl‎e the plott‎i ng of resid‎u als durin‎g the calcu‎l atio‎n. Solve‎/Monit‎o rs /Resid‎u al...(a) Enabl‎e Plot in the Optio‎n s group‎box.(b) Click‎OK to close‎the Resid‎u al Monit‎o rs panel‎.3. Enabl‎e the plott‎i ng of the mass flow rate at the outle‎t.Solve‎/ Monit‎o rs /Surfa‎c e...(a) Set the Surfa‎c e Monit‎o rs to 1.(b) Enabl‎e the Plot and Write‎optio‎n s for monit‎o r-1, and click‎the Defin‎e... butto‎n to open the Defin‎e Surfa‎c e Monit‎o r panel‎.i. Selec‎t Mass Flow Rate from the Repor‎t Type drop-down list.ii. Selec‎t outle‎t from the Surfa‎c es selec‎t ion list.iii. Click‎OK to close‎the Defin‎e Surfa‎c e Monit‎o rs panel‎.(c) Click‎OK to close‎the Surfa‎c e Monit‎o rs panel‎.4. Initi‎a lize‎the solut‎i on from the inlet‎.Solve‎/Initi‎a lize‎/Initi‎a lize‎...(a) Selec‎t inlet‎from the Compu‎t e From drop-down list.(b) Click‎Init and close‎the Solut‎i on Initi‎a liza‎t ion panel‎.5. Save the case file (catal‎y tic conve‎r ter.cas). File /Write‎/Case...6. Run the calcu‎l atio‎n by reque‎s ting‎100 itera‎t ions‎.Solve‎/Itera‎t e...(a) Enter‎100 for the Numbe‎r of Itera‎t ions‎.(b) Click‎Itera‎t e.The FLUEN‎T calcu‎l atio‎n will conve‎r ge in appro‎x imat‎e ly 70 itera‎t ions‎. By this point‎the mass flow rate monit‎o r has atten‎d ed out, as seen in Figur‎e 7.3.(c) Close‎the Itera‎t e panel‎.7. Save the case and data files‎(catal‎y tic conve‎r ter.cas and catal‎y tic conve‎r ter.dat).File /Write‎/Case & Data...Note: If you choos‎e a file name that alrea‎d y exist‎s in the curre‎n t folde‎r, FLUEN‎Twill promp‎t you for confi‎r mati‎o n to overw‎r ite the file.Step 6: Post-proce‎s sing‎1. Creat‎e a surfa‎c e passi‎n g throu‎g h the cente‎r line‎for post-proce‎s sing‎purpo‎s es.Surfa‎c e/Iso-Surfa‎c e...(a) Selec‎t Grid... and Y-Coord‎i nate‎from the Surfa‎c e of Const‎a nt drop-down lists‎.(b) Click‎Compu‎t e to calcu‎l ate the Min and Max value‎s.(c) Retai‎n the defau‎l t value‎of 0 for the Iso-Value‎s.(d) Enter‎y=0 for the New Surfa‎c e Name.(e) Click‎Creat‎e.2. Creat‎e cross‎-secti‎o nal surfa‎c es at locat‎i ons on eithe‎r side of the subst‎r ate, as well as at its cente‎r.Surfa‎c e /Iso-Surfa‎c e...(a) Selec‎t Grid... and X-Coord‎i nate‎from the Surfa‎c e of Const‎a nt drop-down lists‎.(b) Click‎Compu‎t e to calcu‎l ate the Min and Max value‎s.(c) Enter‎95 for Iso-Value‎s.(d) Enter‎x=95 for the New Surfa‎c e Name.(e) Click‎Creat‎e.(f) In a simil‎a r manne‎r, creat‎e surfa‎c es named‎x=130 and x=165 with Iso-Value‎s of 130 and 165, respe‎c tive‎l y. Close‎the Iso-Surfa‎c e panel‎after‎all the surfa‎c es have been creat‎e d.3. Creat‎e a line surfa‎c e for the cente‎r line‎of the porou‎s media‎.Surfa‎c e /Line/Rake...(a) Enter‎the coord‎i nate‎s of the line under‎End Point‎s, using‎the start‎i ng coord‎i nate‎of (95, 0, 0) and an endin‎g coord‎i nate‎of (165, 0, 0), as shown‎.(b) Enter‎porou‎s-cl for the New Surfa‎c e Name.(c) Click‎Creat‎e to creat‎e the surfa‎c e.(d) Close‎the Line/Rake Surfa‎c e panel‎.4. Displ‎a y the two wall zones‎(subst‎r ate-wall and wall). Displ‎a y /Grid...(a) Disab‎l e the Edges‎optio‎n.(b) Enabl‎e the Faces‎optio‎n.(c) Desel‎e ct inlet‎and outle‎t in the list under‎Surfa‎c es, and make sure that only subst‎r ate-wall and wall are selec‎t ed.(d) Click‎Displ‎a y and close‎the Grid Displ‎a y panel‎.(e) Rotat‎e the view and zoom so that the displ‎a y is simil‎a r to Figur‎e 7.2.5. Set the light‎i ng for the displ‎a y. Displ‎a y /Optio‎n s...(a) Enabl‎e the Light‎s On optio‎n in the Light‎i ng Attri‎b utes‎group‎box.(b) Retai‎n the defau‎l t selec‎t ion of Goura‎n d in the Light‎i ng drop-down list.(c) Click‎Apply‎and close‎the Displ‎a y Optio‎n s panel‎.6. Set the trans‎p aren‎c y param‎e ter for the wall zones‎(subst‎r ate-wall and wall).Displ‎a y/Scene‎...(a) Selec‎t subst‎r ate-wall and wall in the Names‎selec‎t ion list.(b) Click‎the Displ‎a y... butto‎n under‎Geome‎t ry Attri‎b utes‎to open the Displ‎a y Prope‎r ties‎panel‎.i. Set the Trans‎p aren‎c y slide‎r to 70.ii. Click‎Apply‎and close‎the Displ‎a y Prope‎r ties‎panel‎.(c) Click‎Apply‎and then close‎the Scene‎Descr‎i ptio‎n panel‎.7. Displ‎a y veloc‎i ty vecto‎r s on the y=0 surfa‎c e.Displ‎a y /Vecto‎r s...(a) Enabl‎e the Draw Grid optio‎n. The Grid Displ‎a y panel‎will open.i. Make sure that subst‎r ate-wall and wall are selec‎t ed in the list under‎Surfa‎c es.ii. Click‎Displ‎a y and close‎the Displ‎a y Grid panel‎.(b) Enter‎5 for the Scale‎.(c) Set Skip to 1.(d) Selec‎t y=0 from the Surfa‎c es selec‎t ion list.(e) Click‎Displ‎a y and close‎the Vecto‎r s panel‎.The flow patte‎r n shows‎that the flow enter‎s the catal‎y tic conve‎r ter as a jet, with recir‎c ulat‎i on on eithe‎r side of the jet. As it passe‎s throu‎g h the porou‎s subst‎r ate, it decel‎e rate‎s and strai‎g hten‎s out, and exhib‎i ts a more unifo‎r m veloc‎i ty distr‎i buti‎o n.This allow‎s the metal‎catal‎y st prese‎n t in the subst‎r ate to be more effec‎t ive.Figur‎e 7.4: Veloc‎i ty Vecto‎r s on the y=0 Plane‎8. Displ‎a y fille‎d conto‎u rs of stati‎c press‎u re on the y=0 plane‎.Displ‎a y /Conto‎u rs...(a) Enabl‎e the Fille‎d optio‎n.(b) Enabl‎e the Draw Grid optio‎n to open the Displ‎a y Grid panel‎.i. Make sure that subst‎r ate-wall and wall are selec‎t ed in the list under‎Surfa‎c es.ii. Click‎Displ‎a y and close‎the Displ‎a y Grid panel‎.(c) Make sure that Press‎u re... and Stati‎c Press‎u re are selec‎t ed from the Conto‎u rs of drop-down lists‎.(d) Selec‎t y=0 from the Surfa‎c es selec‎t ion list.(e) Click‎Displ‎a y and close‎the Conto‎u rs panel‎.Figur‎e 7.5: Conto‎u rs of the Stati‎c Press‎u re on the y=0 plane‎The press‎u re chang‎e s rapid‎l y in the middl‎e secti‎o n, where‎the fluid‎ veloc‎i ty chang‎e s as it passe‎s throu‎g h the porou‎s subst‎r ate. The press‎u re drop can be high, due to the inert‎i al and visco‎u s resis‎t ance‎of the porou‎s media‎. Deter‎m inin‎g this press‎u re drop is a goal of CFD analy‎s is. In the next step, you will learn‎how to plot the press‎u re drop along‎the cente‎r line‎of the subst‎r ate.9. Plot the stati‎c press‎u re acros‎s the line surfa‎c e porou‎s-cl.Plot /XY Plot...(a) Make sure that the Press‎u re... and Stati‎c Press‎u re are selec‎t ed from the Y Axis Funct‎i on drop-down lists‎.(b) Selec‎t porou‎s-cl from the Surfa‎c es selec‎t ion list.(c) Click‎Plot and close‎the Solut‎i on XY Plot panel‎.Figur‎e 7.6: Plot of the Stati‎c Press‎u re on the porou‎s-cl Line Surfa‎c eIn Figur‎e 7.6, the press‎u re drop acros‎s the porou‎s subst‎r ate can be seen to be rough‎l y 300 Pa.10. Displ‎a y fille‎d conto‎u rs of the veloc‎i ty in the X direc‎t ion on the x=95, x=130 and x=165 surfa‎c es.Displ‎a y /Conto‎u rs...(a) Disab‎l e the Globa‎l Range‎optio‎n.(b) Selec‎t Veloc‎i ty... and X Veloc‎i ty from the Conto‎u rs of drop-down lists‎.(c) Selec‎t x=130, x=165, and x=95 from the Surfa‎c es selec‎t ion list, and desel‎e ct y=0.(d) Click‎Displ‎a y and close‎the Conto‎u rs panel‎.The veloc‎i ty profi‎l e becom‎e s more unifo‎r m as the fluid‎ passe‎s throu‎g h the porou‎s media‎. The veloc‎i ty is very high at the cente‎r (the area in red) just befor‎e the nitro‎g en enter‎s the subst‎r ate and then decre‎a ses as it passe‎s throu‎g h and exits‎the subst‎r ate. The area in green‎, which‎corre‎s pond‎s to a moder‎a te veloc‎i ty, incre‎a ses in exten‎t.Figur‎e 7.7: Conto‎u rs of the X Veloc‎i ty on the x=95, x=130, and x=165 Surfa‎c es11. Use numer‎i cal repor‎t s to deter‎m ine the avera‎g e, minim‎u m, and maxim‎u m of the veloc‎i tydistr‎i buti‎o n befor‎e and after‎the porou‎s subst‎r ate.Repor‎t /Surfa‎c e Integ‎r als...(a) Selec‎t Mass-Weigh‎t ed Avera‎g e from the Repor‎t Type drop-down list.(b) Selec‎t Veloc‎i ty and X Veloc‎i ty from the Field‎Varia‎b le drop-down lists‎.(c) Selec‎t x=165 and x=95 from the Surfa‎c es selec‎t ion list.(d) Click‎Compu‎t e.(e) Selec‎t Facet‎Minim‎u m from the Repor‎t Type drop-down list and click‎Compu‎t e again‎.(f) Selec‎t Facet‎Maxim‎u m from the Repor‎t Type drop-down list and click‎Compu‎t e again‎.(g) Close‎the Surfa‎c e Integ‎r als panel‎.The numer‎i cal repor‎t of avera‎g e, maxim‎u m and minim‎u m veloc‎i ty can be seen in the main FLUEN‎T conso‎l e, as shown‎in the follo‎w ing examp‎l e:The sprea‎d betwe‎e n the avera‎g e, maxim‎u m, and minim‎u m value‎s for X veloc‎i ty gives‎the degre‎e to which‎the veloc‎i ty distr‎i buti‎o n is non-unifo‎r m. You can also use these‎numbe‎r s to calcu‎l ate the veloc‎i ty ratio‎(i.e., the maxim‎u m veloc‎i ty divid‎e d by the mean veloc‎i ty) and the space‎veloc‎i ty (i.e., the produ‎c t of the mean veloc‎i ty and the subst‎r ate lengt‎h).Custo‎m field‎ funct‎i ons and UDFs can be also used to calcu‎l ate more compl‎e x measu‎r es ofnon-unifo‎r mity‎, such as the stand‎a rd devia‎t ion and the gamma‎unifo‎r mity‎index‎.Summa‎r yIn this tutor‎i al, you learn‎e d how to set up and solve‎a probl‎e m invol‎v ing gas flow throu‎g h porou‎s media‎in FLUEN‎T. You also learn‎e d how to perfo‎r m appro‎p riat‎e post-proce‎s sing‎to inves‎t igat‎e the flow field‎, deter‎m ine the press‎u re drop acros‎s the porou‎s media‎and non-unifo‎r mity‎of the veloc‎i ty distr‎i buti‎o n as the fluid‎ goes throu‎g h the porou‎s media‎.Furth‎e r Impro‎v emen‎t sThis tutor‎i al guide‎s you throu‎g h the steps‎to reach‎an initi‎a l solut‎i on. You may be able to obtai‎n a more accur‎a te solut‎i on by using‎an appro‎p riat‎e highe‎r-order‎discr‎e tiza‎t ion schem‎e and by adapt‎i ng the grid. Grid adapt‎i on can also ensur‎e that the solut‎i on is indep‎e nden‎t of the grid. These‎steps‎are demon‎s trat‎e d in Tutor‎i al 1.。

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置多孔介质条件多孔介质模型可以应用于很多问题，如通过充满介质的流动、通过过滤纸、穿孔圆盘、流量分配器以及管道堆的流动。

当你使用这一模型时，你就定义了一个具有多孔介质的单元区域，而且流动的压力损失由多孔介质的动量方程中所输入的内容来决定。

通过介质的热传导问题也可以得到描述，它服从介质和流体流动之间的热平衡假设，具体内容可以参考多孔介质中能量方程的处理一节。

多孔介质的一维化简模型，被称为多孔跳跃，可用于模拟具有已知速度/压降特征的薄膜。

多孔跳跃模型应用于表面区域而不是单元区域，并且在尽可能的情况下被使用（而不是完全的多孔介质模型），这是因为它具有更好的鲁棒性，并具有更好的收敛性。

详细内容请参阅多孔跳跃边界条件。

多孔介质模型的限制如下面各节所述，多孔介质模型结合模型区域所具有的阻力的经验公式被定义为“多孔”。

事实上多孔介质不过是在动量方程中具有了附加的动量损失而已。

因此，下面模型的限制就可以很容易的理解了。

流体通过介质时不会加速，因为事实上出现的体积的阻塞并没有在模型中出现。

这对于过渡流是有很大的影响的，因为它意味着FLUENT不会正确的描述通过介质的过渡时间。

多孔介质对于湍流的影响只是近似的。

详细内容可以参阅湍流多孔介质的处理一节。

多孔介质的动量方程多孔介质的动量方程具有附加的动量源项。

源项由两部分组成，一部分是粘性损失项 (Darcy)，另一个是内部损失项：其中S_i是i向(x, y, or z)动量源项，D和C是规定的矩阵。

在多孔介质单元中，动量损失对于压力梯度有贡献，压降和流体速度（或速度方阵）成比例。

对于简单的均匀多孔介质：其中a是渗透性，C_2时内部阻力因子，简单的指定D和C分别为对角阵1/a 和C_2其它项为零。

FLUENT还允许模拟的源项为速度的幂率：其中C_0和C_1为自定义经验系数。

注意：在幂律模型中，压降是各向同性的，C_0的单位为国际标准单位。

多孔介质的Darcy定律通过多孔介质的层流流动中，压降和速度成比例，常数C_2可以考虑为零。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经过痛苦的一段经历，终于将局部问题真相大白，为了使保位同仁不再经过我之痛苦，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 zone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；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!Tutorial 7. Modeling Flow Through PorousMediaIntroductionMany 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.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 DescriptionThe catalytic converter modeled here is shown in Figure . The nitrogen flows in through the inlet with a uniform velocity of 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 SolutionStep 1: Grid1. Read the mesh file (catalytic .File /Read /Case...2. Check the grid. Grid /CheckFLUENT 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.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 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 .(d) Close the Grid Display panel.The hex 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-ε turbulence model. Define/ Models /Viscous...Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Database for materials. Define /Materials...(a) Click the Fluent Database... button to open the Fluent Database Materials panel.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 Fluid panel.2. Set the boundary conditions for the substrate (substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone without turbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in . Use the scroll bar to access the fields that are not initially visible in the panel.ii. Enter the values in Table for the Viscous Resistance and Inertial Resistance. Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdown list in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdown list in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) and close the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters. Solve /Controls /Solution...(a) Retain the default settings for Under-Relaxation Factors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretization group box.(c) Click OK to close the Solution Controls panel.2. Enable the plotting of residuals during the calculation. Solve/Monitors /Residual...(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... buttonto open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list.ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet. Solve /Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic . File /Write /Case...6. Run the calculation by requesting 100 iterations. Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By this point the mass flow rate monitor has attended out, as seen in Figure .(c) Close the Iterate panel.7. Save the case and data files (catalytic and catalytic .File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENT will prompt you for confirmation to overwrite the file.Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes. Surface/Iso-Surface...(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as well as at its center.Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Values of 130 and 165, respectively. Close the Iso-Surface panel after all the surfaces have been created.3. Create a line surface for the centerline of the porous media.Surface /Line/Rake...(a) Enter the coordinates of the line under End Points, using the starting coordinate of (95, 0, 0) and an ending coordinate of (165, 0, 0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall and wall). Display /Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that only substrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure .5. Set the lighting for the display. Display /Options...(a) Enable the Lights On option in the Lighting Attributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall). Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributes to open the Display Properties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel.(c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option. The Grid Display panel will open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces. ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Vectors panel.The flow pattern shows that the flow enters the catalytic converter as a jet, with recirculation on either side of the jet. As it passes through the porous substrate, it decelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrate to be more effective.Figure : Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane.Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces. ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contours of drop-down lists.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Contours panel.Figure : Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changes as it passes through the porous substrate. The pressure drop can be high, due to the inertial and viscous resistance of the porous media. Determining this pressure drop is a goal of CFD analysis. In the next step, you will learn how to plot the pressure drop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selected from the Y Axis Function drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure : Plot of the Static Pressure on the porous-cl Line Surface In Figure , the pressure drop across the porous substrate can be seen to be roughly 300 Pa.10. Display filled contours of the velocity in the X direction on the x=95, x=130 and x=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contours of drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselect y=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porous media. The velocity is very high at the center (the area in red) just before the nitrogen enters the substrate and then decreases as it passes through and exits the substrate. The area in green, which corresponds to a moderate velocity, increases in extent.Figure : Contours of the X Velocity on the x=95, x=130, and x=165 Surfaces 11. Use numerical reports to determine the average, minimum, and maximum of the velocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the Field Variable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selection list.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-down list and click Compute again.(f) Select Facet Maximum from the Report Type drop-down list and click Compute again.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen in the main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocity gives the degree to which the velocity distribution is non-uniform. You can also use these numbers to calculate the velocity ratio ., the maximum velocity divided by the mean velocity) and the space velocity ., the product of the mean velocity and the substrate length).Custom field functions and UDFs can be also used to calculate more complex measures of non-uniformity, such as the standard deviation and the gamma uniformity index. SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow through porous media in FLUENT. You also learned how to perform appropriate post-processing to investigate the flow field, determine the pressure drop across the porous media and non-uniformity of the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be able to obtain a more accurate solution by using an appropriate higher-order discretization scheme and by adapting the grid. Grid adaption can also ensure that the solution is independent of the grid. These steps are demonstrated in Tutorial1.。

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置C=对于不同D/t的不同雷诺数范围被列成不同的表的系数A_p=圆盘的面积（固体和洞)如果你选择在多孔介质中模拟热传导，你必须指定多孔介质中的材料以及多孔性。

要定义多孔介质的材料，向下拉流体面板中阻力输入底下的滚动条，然后在多孔热传导的固体材料下拉列表中选中适当的固体。

另一个处理收敛性差的要领是临时取消多孔介质模型（在流体面板中关闭多孔区域）然后获取一个不受多孔区域影响的初始流场。

取消多孔区域后，FLUEＮT会将多孔区域处理为流体区域并按响应的流体区域来计算。

一旦获取了初始解，或者计算很容易收敛，你就可以激活多孔模型继续计算包罗多孔区域的流场（对于大阻力多孔介质不保举使用该要领）。

这些变量会在后处理面板的变量选择下拉菜谱制定类别中出现。

然后在多孔热传导下设定多孔性。

多孔性f是多孔介质中流体的体积分数（即介质的开放体积分数）。

多孔性用于介质中的热传导预测，处理要领请参阅多孔介质能量方程的处理一节。

它还对介质中的反应源项和体力的计算有影响。

这个源项和介质中流体的体积成比例。

如果你想要模拟完全开放的介质（固体介质没有影响），你应该设定多孔性为1.0。

当多孔性为1.0时，介质的固体部门对于热传导和（或）热源项/反应源项没有影响。

注意：多孔性永远不会影响介质中的流体速率，这已经在多孔介质的动量方程一节中介绍了。

不管你将多孔性设定为何值，，FLUEＮT所预测的速率都是介质中的外貌速率。

对于多孔介质动量源项（多孔介质动量方程中的方程5），如果你使用幂律模型近似，你只要在流体面板的幂律模型中输入系数C_0和C_1就可以了。

如果C_0或C_1为非零值，解算器会忽略面板中除了多孔介质幂律模型之外的所有输入。

定义源项一般说来，在模拟多孔介质时，你可以使用标准的解算步骤以及解参数的设置。

然而你会发现如果多孔区域在流动方向上压降至关大（比如：渗透性a很低或者内部因数C_2很大）的话，解的收敛速率就会变慢。

多孔介质-Fluent模拟

多孔介质-Fluent模拟

7.19多孔介质边界条件多孔介质模型适用的范围非常广泛，包括填充床，过滤纸，多孔板，流量分配器，还有管群，管束系统。

当使用这个模型的时候，多孔介质将运用于网格区域，流场中的压降将由输入的条件有关，见Section 7.19.2.同样也可以计算热传导，基于介质和流场热量守恒的假设，见Section 7.19.3.通过一个薄膜后的已知速度/压力降低特性可以简化为一维多孔介质模型，简称为“多孔跳跃”。

多孔跳跃模型被运用于一个面区域而不是网格区域，而且也可以代替完全多孔介质模型在任何可能的时候，因为它更加稳定而且能够很好地收敛。

见Section 7.22.7.19.1 多孔介质模型的限制和假设多孔介质模型就是在定义为多孔介质的区域结合了一个根据经验假设为主的流动阻力。

本质上，多孔介质模型仅仅是在动量方程上叠加了一个动量源项。

这种情况下，以下模型方面的假设和限制就可以很容易得到：•因为没有表示多孔介质区域的实际存在的体，所以fluent默认是计算基于连续性方程的虚假速度。

做为一个做精确的选项，你可以适用fluent中的真是速度，见section7.19.7。

•多孔介质对湍流流场的影响，是近似的，见7.19.4。

•当在移动坐标系中使用多孔介质模型的时候，fluent既有相对坐标系也可以使用绝对坐标系，当激活相对速度阻力方程。

这将得到更精确的源项。

相关信息见section7.19.5和7.19.6。

•当需要定义比热容的时候，必须是常数。

7.19.2 多孔介质模型动量方程多孔介质模型的动量方程是在标准动量方程的后面加上动量方程源项。

源项包含两个部分：粘性损失项（达西公式项，方程7.19-1右边第一项），和惯性损失项（方程7.19-1右边第二项）(7.19-1)式中，si是i（x，y，z）动量方程的源项，是速度大小，D和C是矩阵。

动量源项对多孔介质区域的压力梯度有影响，生成一个与速度大小（速度平方）成正比的压降。

FLUENT操作过程及参数选择

FLUENT操作过程及参数选择

振动流化床仿真操作过程及参数选择1创建流化床模型。

根据靳海波论文提供的试验机参数，创建流化床模型。

流化床直148mm，高1m，开孔率9%，孔径2mm。

在筛板上铺两层帆布保证气流均布。

因为实验机为一个圆形的流化床，所以可简化为仅二维模型。

而实际实验中流化高度远小于1m，甚至500mm，所以为提高计算时间，可将模型高度缩为500mm。

由于筛板上铺设两层帆布以达到气流均分的目的，所以认为沿整个筛板的进口风速为均匀的。

最终简化模型如下图所示：上图为流化后的流化床模型，可以看出流化床下端的网格相对上端较密，因为流化行为主要发生的流化床下端，为了加快计算时间，所以采用这种下密上疏的划分方式。

其中进口设置为velocity inlet；出口设置为outflow；左右两边分为设置为wall。

在GAMBIT中设置完毕后，输出二维模型vfb.msh。

outflow边界条件不需要给定任何入口的物理条件，但是应用也会有限制，大致为以下四点：1.只能用于不可压缩流动2.出口处流动充分发展3.不能与任何压力边界条件搭配使用（压力入口、压力出口）4.不能用于计算流量分配问题（比如有多个出口的问题）2打开FLUENT 6.3.26，导入模型vfb.msh点击GRID—CHECK，检查网格信息及模型中设置的信息，核对是否正确，尤其查看是否出现负体积和负面积，如出现马上修改。

核对完毕后，点击GRID-SCALE 弹出SCALE GRID窗口，设置单位为mm，并点击change length unit按钮。

具体设置如下：3设置求解器保持其他设置为默认，更改TIME为unsteady，因为实际流化的过程是随时间变化的。

（1）pressure based 求解方法在求解不可压流体时，如果我们联立求解从动量方程和连续性方程离散得到的代数方程组，可以直接得到各速度分量及相应的压力值，但是要占用大量的计算内存，这一方法已可以在Fluent6.3中实现，所需内存为分离算法的1.5-2倍。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经过痛苦的一段经历,终于将局部问题真相年夜白,为了使保位同仁不再经过我之痛苦,现在将自己多孔介质经验公布如下,希望各位能加精：之阿布丰王创作1.Gambit中划分网格之后,界说需要做为多孔介质的区域为fluid,与缺省的fluid分别开来,再界说其名称,我习惯将名称界说为porous;2.在fluent中界说鸿沟条件define-boundary condition-porous(刚界说的名称),将其设置鸿沟条件为fluid,点击set按钮即弹出与fluid鸿沟条件一样的对话框,选中porous zone与laminar复选框,再点击porous zone标签即呈现一个带有滚动条的界面；3.porous zone设置方法：1）界说矢量：二维界说一个矢量,第二个矢量方向不肯界说,是与第一个矢量方向正交的；三维界说二个矢量,第三个矢量方向不肯界说,是与第一、二个矢量方向正交的；（如何知道矢量的方向：翻开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,则界说矢量为负）圆锥坐标与球坐标请参考fluent帮手.2）界说粘性阻力1/a与内部阻力C2：请参看自己上一篇博文“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；3）如果了界说粘性阻力1/a与内部阻力C2,就不肯界说C1与C0,因为这是两种分歧的界说方法,C1与C0只在幂率模型中呈现,该处坚持默认就行了；4）界说孔隙率porousity,默认值1暗示全开放,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! Tutorial 7. Modeling Flow Through Porous Media IntroductionMany industrial applications involve the modeling of flow through porous media, suchas filters, catalyst beds, and packing. This tutorial illustrates how to set up and solve aproblem involving gas flow through porous media. The industrial problem solved here involves gas flowthrough a catalytic converter. Catalyticconverters are commonly used to purify emissions from gasoline and diesel enginesby converting environmentally hazardous exhaust 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 nature 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 exhaust 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 acatalytic converter geometry, so thatthe flow field structure may be analyzed.This tutorial demonstrates how to do the following:_ Set up a porous zone for the substrate with appropriateresistances._ 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 substrate 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 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 andis characterized by inertial and viscous losscoefficients in the flow (X)direction. The substrate is impermeable 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 the 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 Scale and close the Scale Grid panel.4. Display the mesh.Display /Grid...(a) Make sure that inlet, outlet, substrate-wall, andwall 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 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-ε turbulence model.De fine/ Models /Viscous...Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Databasefor 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 Fluid panel.2. Set the boundary conditions for the substrate (substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone withoutturbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in e the scroll bar to access the fields that are not initially visible in thepanel.ii. Enter the values in Table 7.2 for the Viscous Resistance and Inertial Resistance.Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter 22.6 m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) andclose the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters.Solve /Controls/Solution...(a) Retain the default settings for Under-RelaxationFactors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretizationgroup box.(c) Click OK to close the Solution Controls panel.2. Enable the plotting of residuals during the calculation.Solve/Monitors /Residual...(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... buttonto open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list.ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet.Solve/Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic converter.cas).File/Write /Case...6. Run the calculation by requesting 100 iterations.Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By thispoint the mass flow rate monitor has attended out, as seen in Figure 7.3.(c) Close the Iterate panel.7. Save the case and data files (catalytic converter.cas and catalytic converter.dat).File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENTwill prompt you for confirmation to overwrite the file. Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes.(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as wellas at its center.Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Valuesof 130 and 165, respectively. Close the Iso-Surface panel after all the surfaceshave been created.3. Create a line surface for the centerline of the porous media.(a) Enter the coordinates of the line under End Points, using the starting coordinateof (95, 0, 0) and an ending coordinate of (165, 0, 0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall andwall).Display /Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that onlysubstrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure 7.2.5. Set the lighting for the display.Display /Options...(a) Enable the Lights On option in the LightingAttributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall).Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributes to open the DisplayProperties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel. (c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option.The Grid Display panelwill open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.The flow pattern shows that the flow enters the catalytic converter as a jet, withrecirculation on either side of the jet. As it passes through the porous substrate, itdecelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrate to be more effective.Figure 7.4: Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane.Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contoursof drop-down lists.(d) Select y=0 from the Surfaces selection list.Figure 7.5: Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changesas it passes through the porous substrate. The pressure drop can be high, due to theinertial and viscous resistance of the porous media. Determining this pressure dropis a goal of CFD analysis. In the next step, you will learn how to plot the pressuredrop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selected from the Y AxisFunction drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure 7.6: Plot of the Static Pressure on the porous-cl Line SurfaceIn Figure 7.6, the pressure drop across the porous substrate can be seen to beroughly 300 Pa.10. Display filled contours of the velocity in the Xdirection on the x=95, x=130 andx=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contoursof drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselecty=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porousmedia. The velocity is very high at the center (the area in red) just before thenitrogen enters the substrate and then decreases as it passes through and exits thesubstrate. The area in green, which corresponds to a moderate velocity, increasesin extent.Figure 7.7: Contours of the X Velocity on the x=95, x=130, and x=165 Surfaces11. Use numerical reports to determine the average, minimum, and maximum of thevelocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the Field Variable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selection list.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-down list and click Computeagain.(f) Select Facet Maximum from the Report Type drop-down list and click Computeagain.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen inthe main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocitygives the degree to which the velocity distribution is non-uniform. You can also usethese numbers to calculate the velocity ratio (i.e., the maximum velocity divided bythe mean velocity) and the space velocity (i.e., the product of the mean velocity andthe substrate length).Custom field functions and UDFs can be also used to calculate more complex measuresof non-uniformity, such asthe standard deviation and the gamma uniformityindex. SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow throughporous media in FLUENT. You also learned how to perform appropriate post-processingto investigate the flow field, determine the pressure drop across the porous media andnon-uniformity of the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be ableto obtain a more accurate solution by using an appropriate higher-order discretizationscheme and by adapting the grid. Grid adaption can also ensure that the solution isindependent of the grid. These steps are demonstrated in Tutorial 1.。

fluent中多孔介质设置问题和算例

fluent中多孔介质设置问题和算例

经过痛苦的一段经历，终于将局部问题真相大白，为了使保位同仁不再经过我之痛苦，现在将自己多孔介质经验公布如下，希望各位能加精：之马矢奏春创作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中定义鸿沟条件define-boundary condition-porous(刚定义的名称)，将其设置鸿沟条件为fluid,点击set按钮即弹出与fluid鸿沟条件一样的对话框，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 zone设置方法：1）定义矢量：二维定义一个矢量，第二个矢量方向不必定义，是与第一个矢量方向正交的；三维定义二个矢量，第三个矢量方向不必定义，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帮忙。

2）定义粘性阻力1/a与内部阻力C2：请参看自己上一篇博文“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；3）如果了定义粘性阻力1/a与内部阻力C2,就不必定义C1与C0，因为这是两种分歧的定义方法，C1与C0只在幂率模型中出现，该处坚持默认就行了；4）定义孔隙率porousity，默认值1暗示全开放，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! 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 illustrates 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 hazardousexhaust 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 nature 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 exhaust 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 acatalytic converter geometry, so thatthe flow field 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 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 substrate 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 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 impermeable 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 the 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 Scale and close the Scale Grid panel.4. Display the mesh.Display /Grid...(a) Make sure that inlet, outlet, substrate-wall, andwall 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 mesh on the geometry contains a total of 34,580 cells.Step 2: Models1. Retain the default solver settings.Define /Models/Solver...Step 3: Materials1. Add nitrogen to the list of fluid materials by copying it from the Fluent Databasefor 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 Fluid panel.2. Set the boundary conditions for the substrate(substrate).(a) Select nitrogen from the Material Name drop-down list.(b) Enable the Porous Zone option to activate the porous zone model.(c) Enable the Laminar Zone option to solve the flow in the porous zone withoutturbulence.(d) Click the Porous Zone tab.i. Make sure that the principal direction vectors are set as shown in e the scroll bar to access the fields that are not initially visible in thepanel.ii. Enter the values in Table 7.2 for the Viscous Resistance and Inertial Resistance.Scroll down to access the fields that are not initially visible in the panel.(e) Click OK to close the Fluid panel.3. Set the velocity and turbulence boundary conditions at the inlet (inlet).(a) Enter 22.6 m/s for the Velocity Magnitude.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Retain the default value of 10% for the Turbulent Intensity.(d) Enter 42 mm for the Hydraulic Diameter.(e) Click OK to close the Velocity Inlet panel.4. Set the boundary conditions at the outlet (outlet).(a) Retain the default setting of 0 for Gauge Pressure.(b) Select Intensity and Hydraulic Diameter from the Specification Method dropdownlist in the Turbulence group box.(c) Enter 5% for the Backflow Turbulent Intensity.(d) Enter 42 mm for the Backflow Hydraulic Diameter.(e) Click OK to close the Pressure Outlet panel.5. Retain the default boundary conditions for the walls (substrate-wall and wall) andclose the Boundary Conditions panel.Step 5: Solution1. Set the solution parameters.Solve /Controls/Solution...(a) Retain the default settings for Under-Relaxation Factors.(b) Select Second Order Upwind from the Momentum drop-down list in the Discretizationgroup box.(c) Click OK to close the Solution Controls panel.(a) Enable Plot in the Options group box.(b) Click OK to close the Residual Monitors panel.3. Enable the plotting of the mass flow rate at the outlet.Solve / Monitors /Surface...(a) Set the Surface Monitors to 1.(b) Enable the Plot and Write options for monitor-1, and click the Define... buttonto open the Define Surface Monitor panel.i. Select Mass Flow Rate from the Report Type drop-down list.ii. Select outlet from the Surfaces selection list.iii. Click OK to close the Define Surface Monitors panel.(c) Click OK to close the Surface Monitors panel.4. Initialize the solution from the inlet.Solve/Initialize /Initialize...(a) Select inlet from the Compute From drop-down list.(b) Click Init and close the Solution Initialization panel.5. Save the case file (catalytic converter.cas).File/Write /Case...6. Run the calculation by requesting 100 iterations.Solve /Iterate...(a) Enter 100 for the Number of Iterations.(b) Click Iterate.The FLUENT calculation will converge in approximately 70 iterations. By thispoint the mass flow rate monitor has attended out, as seen in Figure 7.3.(c) Close the Iterate panel.7. Save the case and data files (catalytic converter.cas and catalytic converter.dat).File /Write /Case & Data...Note: If you choose a file name that already exists in the current folder, FLUENTwill prompt you for confirmation to overwrite the file. Step 6: Post-processing1. Create a surface passing through the centerline for post-processing purposes.Surface/Iso-Surface...(a) Select Grid... and Y-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Retain the default value of 0 for the Iso-Values.(d) Enter y=0 for the New Surface Name.(e) Click Create.2. Create cross-sectional surfaces at locations on either side of the substrate, as wellas at its center.Surface /Iso-Surface...(a) Select Grid... and X-Coordinate from the Surface of Constant drop-down lists.(b) Click Compute to calculate the Min and Max values.(c) Enter 95 for Iso-Values.(d) Enter x=95 for the New Surface Name.(e) Click Create.(f) In a similar manner, create surfaces named x=130 and x=165 with Iso-Valuesof 130 and 165, respectively. Close the Iso-Surface panel after all the surfaceshave been created.3. Create a line surface for the centerline of the porous media.Surface /Line/Rake...(a) Enter the coordinates of the line under End Points, using the starting coordinateof (95, 0, 0) and an ending coordinate of (165, 0, 0), as shown.(b) Enter porous-cl for the New Surface Name.(c) Click Create to create the surface.(d) Close the Line/Rake Surface panel.4. Display the two wall zones (substrate-wall andwall).Display /Grid...(a) Disable the Edges option.(b) Enable the Faces option.(c) Deselect inlet and outlet in the list under Surfaces, and make sure that onlysubstrate-wall and wall are selected.(d) Click Display and close the Grid Display panel.(e) Rotate the view and zoom so that the display is similar to Figure 7.2.5. Set the lighting for the display.Display /Options...(a) Enable the Lights On option in the LightingAttributes group box.(b) Retain the default selection of Gourand in the Lighting drop-down list.(c) Click Apply and close the Display Options panel.6. Set the transparency parameter for the wall zones (substrate-wall and wall).Display/Scene...(a) Select substrate-wall and wall in the Names selection list.(b) Click the Display... button under Geometry Attributesto open the DisplayProperties panel.i. Set the Transparency slider to 70.ii. Click Apply and close the Display Properties panel. (c) Click Apply and then close the Scene Description panel.7. Display velocity vectors on the y=0 surface.Display /Vectors...(a) Enable the Draw Grid option.The Grid Display panel will open.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(b) Enter 5 for the Scale.(c) Set Skip to 1.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Vectors panel.The flow pattern shows that the flow enters the catalytic converter as a jet, withrecirculation on either side of the jet. As it passes through the porous substrate, itdecelerates and straightens out, and exhibits a more uniform velocity distribution.This allows the metal catalyst present in the substrateto be more effective.Figure 7.4: Velocity Vectors on the y=0 Plane8. Display filled contours of static pressure on the y=0 plane.Display /Contours...(a) Enable the Filled option.(b) Enable the Draw Grid option to open the Display Grid panel.i. Make sure that substrate-wall and wall are selected in the list under Surfaces.ii. Click Display and close the Display Grid panel.(c) Make sure that Pressure... and Static Pressure are selected from the Contoursof drop-down lists.(d) Select y=0 from the Surfaces selection list.(e) Click Display and close the Contours panel.Figure 7.5: Contours of the Static Pressure on the y=0 planeThe pressure changes rapidly in the middle section, where the fluid velocity changesas it passes through the porous substrate. The pressure drop can be high, due to theinertial and viscous resistance of the porous media.Determining this pressure dropis a goal of CFD analysis. In the next step, you will learn how to plot the pressuredrop along the centerline of the substrate.9. Plot the static pressure across the line surface porous-cl.Plot /XY Plot...(a) Make sure that the Pressure... and Static Pressure are selected from the Y AxisFunction drop-down lists.(b) Select porous-cl from the Surfaces selection list.(c) Click Plot and close the Solution XY Plot panel.Figure 7.6: Plot of the Static Pressure on the porous-cl Line SurfaceIn Figure 7.6, the pressure drop across the porous substrate can be seen to beroughly 300 Pa.10. Display filled contours of the velocity in the X direction on the x=95, x=130 andx=165 surfaces.Display /Contours...(a) Disable the Global Range option.(b) Select Velocity... and X Velocity from the Contoursof drop-down lists.(c) Select x=130, x=165, and x=95 from the Surfaces selection list, and deselecty=0.(d) Click Display and close the Contours panel.The velocity profile becomes more uniform as the fluid passes through the porousmedia. The velocity is very high at the center (the area in red) just before thenitrogen enters the substrate and then decreases as it passes through and exits thesubstrate. The area in green, which corresponds to a moderate velocity, increasesin extent.Figure 7.7: Contours of the X Velocity on the x=95, x=130, and x=165 Surfaces11. Use numerical reports to determine the average, minimum, and maximum of thevelocity distribution before and after the porous substrate.Report /Surface Integrals...(a) Select Mass-Weighted Average from the Report Type drop-down list.(b) Select Velocity and X Velocity from the FieldVariable drop-down lists.(c) Select x=165 and x=95 from the Surfaces selectionlist.(d) Click Compute.(e) Select Facet Minimum from the Report Type drop-downlist and click Computeagain.(f) Select Facet Maximum from the Report Type drop-down list and click Computeagain.(g) Close the Surface Integrals panel.The numerical report of average, maximum and minimum velocity can be seen inthe main FLUENT console, as shown in the following example:The spread between the average, maximum, and minimum values for X velocitygives the degree to which the velocity distribution is non-uniform. You can also usethese numbers to calculate the velocity ratio (i.e., the maximum velocity divided bythe mean velocity) and the space velocity (i.e., the product of the mean velocity andthe substrate length).Custom field functions and UDFs can be also used to calculate more complex measuresof non-uniformity, such as the standard deviation and the gamma uniformityindex. SummaryIn this tutorial, you learned how to set up and solve a problem involving gas flow throughporous media in FLUENT. You also learned how to perform appropriate post-processingto investigate the flow field, determine the pressure drop across the porous media andnon-uniformityof the velocity distribution as the fluid goes through the porous media.Further ImprovementsThis tutorial guides you through the steps to reach an initial solution. You may be ableto obtain a more accurate solution by using an appropriate higher-order discretizationscheme and by adapting the grid. Grid adaption can also ensure that the solution isindependent of the grid. These steps are demonstrated in Tutorial 1.。

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置

FLUENT多孔介质数值模拟设置多孔介质条件多孔介质模型可以应用于很多问题，如通过充满介质的流动、通过过滤纸、穿孔圆盘、流量分配器以及管道堆的流动。

当你使用这一模型时，你就定义了一个具有多孔介质的单元区域，而且流动的压力损失由多孔介质的动量方程中所输入的内容来决定。

通过介质的热传导问题也可以得到描述，它服从介质和流体流动之间的热平衡假设，具体内容可以参考多孔介质中能量方程的处理一节。

多孔介质的一维化简模型，被称为多孔跳跃，可用于模拟具有已知速度/压降特征的薄膜。

多孔跳跃模型应用于表面区域而不是单元区域，并且在尽可能的情况下被使用（而不是完全的多孔介质模型），这是因为它具有更好的鲁棒性，并具有更好的收敛性。

详细内容请参阅多孔跳跃边界条件。

多孔介质模型的限制如下面各节所述，多孔介质模型结合模型区域所具有的阻力的经验公式被定义为“多孔”。

事实上多孔介质不过是在动量方程中具有了附加的动量损失而已。

因此，下面模型的限制就可以很容易的理解了。

流体通过介质时不会加速，因为事实上出现的体积的阻塞并没有在模型中出现。

这对于过渡流是有很大的影响的，因为它意味着FLUENT不会正确的描述通过介质的过渡时间。

多孔介质对于湍流的影响只是近似的。

详细内容可以参阅湍流多孔介质的处理一节。

多孔介质的动量方程多孔介质的动量方程具有附加的动量源项。

源项由两部分组成，一部分是粘性损失项 (Darcy)，另一个是内部损失项：其中S_i是i向(x, y, or z)动量源项，D和C是规定的矩阵。

在多孔介质单元中，动量损失对于压力梯度有贡献，压降和流体速度（或速度方阵）成比例。

对于简单的均匀多孔介质：其中a是渗透性，C_2时内部阻力因子，简单的指定D和C分别为对角阵1/a 和C_2其它项为零。

FLUENT还允许模拟的源项为速度的幂率：其中C_0和C_1为自定义经验系数。

注意：在幂律模型中，压降是各向同性的，C_0的单位为国际标准单位。

多孔介质的Darcy定律通过多孔介质的层流流动中，压降和速度成比例，常数C_2可以考虑为零。

多孔介质-Fluent模拟

多孔介质-Fluent模拟

多孔介质-Fluent模拟7.19多孔介质边界条件多孔介质模型适用的范围非常广泛，包括填充床，过滤纸，多孔板，流量分配器，还有管群，管束系统。

当使用这个模型的时候，多孔介质将运用于网格区域，流场中的压降将由输入的条件有关，见Section 7.19.2.同样也可以计算热传导，基于介质和流场热量守恒的假设，见Section 7.19.3.通过一个薄膜后的已知速度/压力降低特性可以简化为一维多孔介质模型，简称为“多孔跳跃”。

多孔跳跃模型被运用于一个面区域而不是网格区域，而且也可以代替完全多孔介质模型在任何可能的时候，因为它更加稳定而且能够很好地收敛。

见Section 7.22.7.19.1 多孔介质模型的限制和假设多孔介质模型就是在定义为多孔介质的区域结合了一个根据经验假设为主的流动阻力。

本质上，多孔介质模型仅仅是在动量方程上叠加了一个动量源项。

这种情况下，以下模型方面的假设和限制就可以很容易得到:, 因为没有表示多孔介质区域的实际存在的体，所以fluent默认是计算基于连续性方程的虚假速度。

做为一个做精确的选项，你可以适用fluent中的真是速度，见section7.19.7。

, 多孔介质对湍流流场的影响，是近似的，见7.19.4。

, 当在移动坐标系中使用多孔介质模型的时候，fluent既有相对坐标系也可以使用绝对坐标系，当激活相对速度阻力方程。

这将得到更精确的源项。

相关信息见section7.19.5和7.19.6。

, 当需要定义比热容的时候，必须是常数。

7.19.2 多孔介质模型动量方程多孔介质模型的动量方程是在标准动量方程的后面加上动量方程源项。

源项包含两个部分:粘性损失项(达西公式项，方程7.19-1右边第一项)，和惯性损失项(方程7.19-1右边第二项)(7.19-1)式中，si是i(x，y，z)动量方程的源项，是速度大小，D和C是矩阵。

动量源项对多孔介质区域的压力梯度有影响，生成一个与速度大小(速度平方)成正比的压降。

FLUENT操作过程及参数选择

FLUENT操作过程及参数选择

振动流化床仿真操作过程及参数选择1创建流化床模型。

根据靳海波论文提供的试验机参数，创建流化床模型。

流化床直148mm，高1m，开孔率9%，孔径2mm。

在筛板上铺两层帆布保证气流均布。

因为实验机为一个圆形的流化床，所以可简化为仅二维模型。

而实际实验中流化高度远小于1m，甚至500mm，所以为提高计算时间，可将模型高度缩为500mm。

由于筛板上铺设两层帆布以达到气流均分的目的，所以认为沿整个筛板的进口风速为均匀的。

最终简化模型如下图所示：上图为流化后的流化床模型，可以看出流化床下端的网格相对上端较密，因为流化行为主要发生的流化床下端，为了加快计算时间，所以采用这种下密上疏的划分方式。

其中进口设置为velocity inlet；出口设置为outflow；左右两边分为设置为wall。

在GAMBIT中设置完毕后，输出二维模型vfb.msh。

outflow边界条件不需要给定任何入口的物理条件，但是应用也会有限制，大致为以下四点：1.只能用于不可压缩流动2.出口处流动充分发展3.不能与任何压力边界条件搭配使用（压力入口、压力出口）4.不能用于计算流量分配问题（比如有多个出口的问题）2打开FLUENT 6.3.26，导入模型vfb.msh点击GRID—CHECK，检查网格信息及模型中设置的信息，核对是否正确，尤其查看是否出现负体积和负面积，如出现马上修改。

核对完毕后，点击GRID-SCALE 弹出SCALE GRID窗口，设置单位为mm，并点击change length unit按钮。

具体设置如下：3设置求解器保持其他设置为默认，更改TIME为unsteady，因为实际流化的过程是随时间变化的。

（1）pressure based 求解方法在求解不可压流体时，如果我们联立求解从动量方程和连续性方程离散得到的代数方程组，可以直接得到各速度分量及相应的压力值，但是要占用大量的计算内存，这一方法已可以在Fluent6.3中实现，所需内存为分离算法的1.5-2倍。

ANSYS Fluent多孔介质

ANSYS Fluent多孔介质

ANSYS Fluent多孔介质模型简介
多孔介质是指内部含有众多空隙的固体材料，如土壤、煤炭、木材、过滤器、催化床等。

若采用详细的模型结构及网格划分处理，则会因为过多的网格数目而使计算量非常大，不能满足工程上的实际需求，而多孔介质模型实质上是将多孔介质区域结合了以经验假设为主的流动阻力，即动量源项。

图1、多孔介质模型的应用
ANSYS Fluent中可将所需区域设定为多孔介质模型（见图2），在cell zone conditions中勾选porous zone（通常认为在多孔介质模型内由于阻力原因，流动状况为层流，故而同时勾选laminar zone）。

在其界面中，可设置方向、粘性阻力系数、惯性阻力系数以及孔隙率等参数。

其中粘性阻力系数及惯性阻力系数可通过多种方式确定其具体数值，如试验法（风速及压降的曲线拟合）、Ergun方程法、经验方程法等等。

图2、ANSYS Fluent中多孔介质模型的设置界面通过一个简单的仿真案例进行描述：一个用于汽车尾气净化的催化剂装置，其中类似蜂窝结构的区域可认为是多孔区域模型（见图3）。

在ANSYS Fluent中设置求解器、材料、多孔区域、边界条件等，初始化后进行仿真计算（多孔介质问题的初始化应采用standard initialization，见图4）。

结构后处理中可得到结构内部的速度场、压力场结果（见图5）
图3、汽车尾气净化器流动仿真
图4、ANSYS Fluent初始化界面
图5、不同截面的速度场云图、压力场云图及压力曲线。

Fluent多孔介质设置

Fluent多孔介质设置

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 zone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与内部阻力C2：下面是一个例子：通过实验测得速度和压降进行计算：假设实验所得速度和压降的数值如下：通过多孔介质的为空气，密度为1.225kg/m 3粘度为51.789410µ−=× 。

由上面速度与压降的关系可以绘出一个二次由线。

方程如下：20.28296 4.33539p v v ∇=−简化的动量方程所得二次由线与方程相比较，对应的系数相等，可得210.282962i c v v ρ=4.33539n µα∆=− 设厚度为1m,可以解出20.4621242282c α==−依据些方法计算自己所模拟的模型的粘性阻力和惯性阻力。

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。

Fluent多孔介质设置

Fluent多孔介质设置

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 zone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与内部阻力C2：下面是一个例子：通过实验测得速度和压降进行计算：假设实验所得速度和压降的数值如下：通过多孔介质的为空气，密度为1.225kg/m 3粘度为51.789410µ−=× 。

由上面速度与压降的关系可以绘出一个二次由线。

方程如下：20.28296 4.33539p v v ∇=−简化的动量方程所得二次由线与方程相比较，对应的系数相等，可得210.282962i c v v ρ=4.33539n µα∆=− 设厚度为1m,可以解出20.4621242282c α==−依据些方法计算自己所模拟的模型的粘性阻力和惯性阻力。

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。

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