ACU-T: 6500 Flow Through Porous Medium


This tutorial provides the instructions for setting up, solving and viewing results for a simulation of a flow through porous medium. Prior to starting this tutorial, you should have already run through the introductory tutorial, ACU-T: 1000 Basic Flow Set Up, and have a basic understanding of HyperWorks CFD and AcuSolve. To run this simulation, you will need access to a licensed version of HyperWorks CFD and AcuSolve.

Prior to running through this tutorial, copy from <Altair_installation_directory>\hwcfdsolvers\acusolve\win64\model_files\tutorials\AcuSolve to a local directory. Extract from

Problem Description

The problem to be addressed in this tutorial is shown schematically in the figure below. It consists of a cylindrical channel with a porous medium in the flow section. As the flow passes through this section, a pressure drop is observed. In this simulation, an inlet velocity will be assigned to the flow and pressure drop across the porous medium will be calculated. The length of the porous section is 0.06 m and the fluid is an imaginary air-like fluid with a density of 1 kg/m3 and a molecular viscosity of 0.001 kg/m-s. The inlet velocity of the flow is 0.2 m/s.

Figure 1.

Start HyperWorks CFD and Open the HyperMesh Database

  1. Start HyperWorks CFD from the Windows Start menu by clicking Start > Altair <version> > HyperWorks CFD.
  2. From the Home tools, Files tool group, click the Open Model tool.

    Figure 2.
    The Open File dialog opens.
  3. Browse to the directory where you saved the model file. Select the HyperMesh file and click Open.
  4. Click File > Save As.
  5. Create a new directory named PorousMedia and navigate into this directory.
    This will be the working directory and all the files related to the simulation will be stored in this location.
  6. Enter PorousMedia as the file name for the database, or choose any name of your preference.
  7. Click Save to create the database.

Validate the Geometry

The Validate tool scans through the entire model, performs checks on the surfaces and solids, and flags any defects in the geometry, such as free edges, closed shells, intersections, duplicates, and slivers.

To focus on the physics part of the simulation, this tutorial input file contains geometry which has already been validated. Observe that a blue check mark appears on the top-left corner of the Validate icon on the Geometry ribbon. This indicates that the geometry is valid, and you can go to the flow set up.

Figure 3.

Set Up Flow

Set Up the Simulation Parameters and Solver Settings

  1. From the Flow ribbon, click the Physics tool.

    Figure 4.
    The Setup dialog opens.
  2. Under the Physics models setting:
    1. Set Time marching to Steady.
    2. Select Laminar as the Turbulence model.

    Figure 5.
  3. Click the Solver controls setting.
  4. Confirm that the Steady update factor and the Steady maximum steps are set to 0.6 and 100, respectively.

    Figure 6.

Assign Material Properties

  1. From the Flow ribbon, click the Material tool.

    Figure 7.
  2. Verify that the material Air is assigned to the model's three solids.

    Figure 8.

Define the Porous Medium

  1. From the Flow ribbon, Porous tool group, click the Cartesian Porous Media tool.

    Figure 9.
  2. Select the middle solid on the model.

    Figure 10.
  3. On the guide bar, click Orientation.
  4. Left-click to place a point anywhere on the selected solid.
  5. In the microdialog, enter the following values for the coefficients.

    Figure 11.
  6. In the microdialog, click to open the Orient tool then verify that the direction is aligned to the global x-axis.

    Figure 12.
  7. On the guide bar, click to execute the command and exit the tool.

Assign the Flow Boundary Conditions

  1. From the Flow ribbon, click the Constant tool.

    Figure 13.
  2. Select the inlet face.

    Figure 14.
  3. In the microdialog, set the velocity parameters as shown below.

    Figure 15.
  4. On the guide bar, click to execute the command and exit the tool.
  5. Click the Outlet tool.

    Figure 16.
  6. Select the outlet face.

    Figure 17.
  7. Accept the default parameters then click on the guide bar.

Generate the Mesh

  1. From the Mesh ribbon, click the Volume tool.

    Figure 18.
    The Meshing Operations dialog opens.
    Note: If the model has not been validated, you are prompted to create the simulation model before running the batch mesh.
  2. Check that the Average element size is 0.01.
  3. Accept all other default parameters.

    Figure 19.
  4. Click Mesh.
    The Run Status dialog opens. Once the run is complete, the status is updated and you can close the dialog.
    Tip: Right-click on the mesh job and select View log file to view a summary of the meshing process.

Run AcuSolve

  1. From the Solution ribbon, click the Run tool.

    Figure 20.
  2. In the Launch AcuSolve dialog, enter the following text in the Additional arguments box: -tlog -lprobe.
    This will launch the AcuProbe and AcuTail utilities automatically once the run is launched.
  3. Set the Parallel processing option to Intel MPI.
  4. Optional: Set the number of processors to 4 or 8 based on availability.
  5. Leave the remaining options as default and click Run to launch AcuSolve.

    Figure 21.
    The Run Status dialog opens. Once the run is complete, the status is updated and you can close the dialog.

Post-Process the Results with AcuProbe

As the solution progresses, AcuProbe is launched automatically. AcuProbe can be used to monitor different variables over solution time. In this step, you will plot the residual ratio values and then compute the pressure drop across the porous section.

  1. In the AcuProbe window, from the Data Tree on the left, expand Residual Ratio.
  2. Right-click on Final and select Plot All.

    Figure 22.
  3. Once the solution is converged, right-click again on Final and select Plot None.
  4. Click the User Function icon from the toolbar.
    The User Function dialog opens.
  5. In the dialog, enter dP as the function name.
  6. In the Function field, type P_In =.
  7. In the Data Tree, expand Surface Output > AUTO Porous-1 SolidBody_2_1 internal > Pressure.
  8. Right-click on pressure and select Copy name. Paste the value in the Function window after P_In =.

    Figure 23.
  9. On the next line, type P_Out = and repeat the above step for pressure on the AUTO Porous-3 SolidBody_4_3 internal surface.
  10. On the next line, type value = P_In - P_Out.
    Note: The word “value” is case sensitive and should always be in lower case. If you use a capital letter, an error window appears.

    Figure 24.
  11. Click Apply to display the plot.
    Note: You might need to click on the toolbar in order to properly display the plot.

    Figure 25.


In this tutorial, you learned how to set up and solve a flow simulation with porous medium. You started by importing the HyperWorks CFD input database and then you defined the porous medium. Next, you assigned the flow boundary conditions and generated the mesh. Once the solution was computed, you created a plot of the pressure drop across the porous section using AcuProbe.