Flow Through Porous Media

Introduction

-This workshop demonstrates how to model porous media in CFX.

-It models a catalytic converter. Nitrogen flows in through the inlet with a uniform velocity of 10 m/s, passes through a ceramic monolith substrate with square shaped channels, and then exits through the outlet.

-The substrate is impermeable in the X and Y direction, which is modeled by specifying loss coefficients 2 orders of magnitude higher than in the Z direction.

 

Starting CFX-Pre

1.Start Workbench and save the Project as cat_converter.wbpj

2.Drag CFX into the Project Schematic from the Component Systems toolbox and name the system Porous

3.Start CFX-Pre by double clicking Setup

4.When CFX-Pre opens, right-click Mesh and select Import Mesh > ICEM CFD. Select the file catconv.cfx5

5.Keep the Mesh Units in m

Material Import

1.Right-click Materials and select Import Library Data

2.Select N2 Ideal Gas by expanding the Calorically Perfect Ideal Gases branch

3.Click OK

Fluid Domain Setup

1.Double-click Default Domain

2.For Fluid 1, set the Material to N2 Ideal Gas (note: use theicon)

3.Switch to the Fluid Models tab

4.Set Heat Transfer to Isothermal

5.Set Fluid Temperature to 450 [C]

6.Set Turbulence to k-epsilon

7.Click OK

Setting Up Boundary conditions

1. Insert a boundary condition named Inlet
2. Set Boundary Type to Inlet
3. Set Location to INLET
4. Switch to the Boundary Details tab
5. Set Mass and Momentum to a Normal Speed of 10 [m s^-1]
6. Click OK
7. Insert a Boundary Condition named Outlet
8. Set Boundary Type to Outlet
9. Set Location to OUTLET
10. Switch to the Boundary Details tab
11. Enter a Relative Pressure of 0 [Pa]
12. Click OK

Setting Up Porous Domain

1. Right-click on Flow Analysis 1 and insert a Domain named Substrate
2. Set the Location to SUBSTRATE
3. Set the Domain Type to Porous Domain
4. Switch to the Porosity Settings tab
5. Set Volume Porosity to 0.5
6. Set the Loss Model option to Directional Loss
7. For the Streamwise Direction, enter components of 0,0,1
8. Set Streamwise Loss to Linear and Quadratic Resistance Coefficients
9. Turn on Quadratic Resistance Coefficient and enter a value of 440 [kg m^-4]
10. Set the Streamwise Coefficient Multiplier to 100 and click OK

Domain Interface

CFX automatically creates a Fluid-Porous interface between the Default Domain and Substrate.

You can double-click Default Fluid-Porous Interface to view the setup, or highlight the Default Fluid Porous Interface Side 1 and Default Fluid Porous Interface Side 2 boundaries in the individual domains to see that that regions are correct.

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