ACU-T: 4001 Water Filling in a Tank

Prerequisites

This tutorial provides instructions for setting up, solving, and viewing results for a transient dam break simulation using the Level Set method. 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 HyperMesh CFD and AcuSolve. To run this simulation, you will need access to a licensed version of HyperMesh CFD and AcuSolve.

Before you begin, copy the file(s) used in this tutorial to your working directory.

Problem Description

The problem to be solved is shown schematically in the figure below. It consists of a half-filled water tank at time t=0. Water is injected through the Inlet at t=0 and as the water fills in through the inlet, the water-air interface can be visualized in a transient simulation.

Figure 1.


Start HyperMesh CFD and Create the HyperMesh Model Database

  1. Start HyperMesh CFD from the Windows Start menu by clicking Start > Altair <version> > HyperMesh CFD.
    When HyperMesh CFD is loaded, the Geometry ribbon is open by default.
  2. Create a new .hm database in one of the following ways:
    • From the menu bar, click File > Save.
    • From the Home tools, Files tool group, click the Save As tool.
      Figure 2.


  3. In the Save File As dialog, navigate to the directory where you would like to save the database.
  4. Enter FillingTank as the name for the database then click Save.
    This will be your problem directory and all the files related to the simulation will be stored in this location.

Import and Validate the Geometry

Import the Geometry

  1. From the menu bar, click File > Import > Geometry Model.
  2. In the Import File dialog, browse to your working directory then select ACU-T4001_tank2D.x_t and click Open.
  3. In the Geometry Import Options dialog, leave all the default options unchanged then click Import.
    Figure 3.


    Figure 4.


Validate the Geometry

  1. From the Geometry ribbon, click the Validate tool.
    Figure 5.


    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.

    The current model does not have any of the issues mentioned above. Alternatively, if any issues are found, they are indicated by the number in the brackets adjacent to the tool name.

    Observe that a blue check mark appears on the top-left corner of the Validate icon. This indicates that the tool found no issues with the geometry model.
    Figure 6.


  2. Press Esc or right-click in the modeling window and swipe the cursor over the green check mark from right to left.
  3. Save the database.

Set Up the Problem

Set Up the Simulation Parameters and Solver Settings

  1. From the Flow ribbon, click the Physics tool.
    Figure 7.


    The Setup dialog opens.
  2. Under the Physics models setting:
    1. Activate the Multiphase flow radio button.
    2. Set the Multifluid type to Immiscible and the Immiscible material to Air-Water
    3. Set the Time step size to 0.01 and the Final time to 3.0
    4. Select Laminar as the Turbulence model.
    5. Set the gravity to -9.81 m/sec2 in the y direction.
    Figure 8.


  3. Click the Solver Controls setting and set the Maximum stagger iterations to 4.
    Figure 9.


  4. Close the dialog and save the model.

Assign Material Properties

  1. From the Flow ribbon, click the Material tool.
    Figure 10.


  2. In the Materials legend, verify that Air-Water is assigned.
  3. Click on the guide bar.

Define Flow Boundary Conditions

  1. From the Flow ribbon, click the Slip tool.
    Figure 11.


  2. Select the right most face on the positive z-axis, as shown in the figure below.
    Figure 12.


  3. In the Boundaries legend, double-click on Slip, rename it to z_pos and press Enter.
  4. On the guide bar, click to execute the command and remain in the tool.
  5. Rotate the model and select the opposite face.
  6. In the Boundaries legend, rename Slip to z_neg.
  7. On the guide bar, click to execute the command and exit the tool.
  8. Click the Constant tool.
    Figure 13.


  9. Select the inlet surface shown in the figure below.
    Figure 14.


  10. In the microdialog,
    1. Set the Inflow velocity type to Normal.
    2. Set the Normal velocity to 1.5 m/s.
    3. Select Water as the incoming immiscible fluid.
  11. On the guide bar, click to execute the command and exit the tool.
  12. Click the Outlet tool.
    Figure 15.


  13. Select the outlet surface shown in the figure below.
    Figure 16.


  14. In the microdialog, activate Hydrostatic pressure.
  15. On the guide bar, click to execute the command and exit the tool.
  16. Save the database.

Generate the Mesh

In this step, first you will create a surface mesh using the Interactive meshing tool; then, you will specify a global mesh size and growth rate for the model and generate the volume mesh using the Batch tool in the Mesh ribbon.

Create Surface Mesh

  1. From the Mesh ribbon, click the Interactive tool.
    Figure 17.


    By default, the Create should be selected from the secondary ribbon.
  2. Click on the guide bar to open the options menu, then make the following changes:
    1. Set the Element size to 0.01.
    2. Set the Element type to R-Trias.
    3. Expand Adaptive mesh and activate the Curvature based refinement option.
      Leave the remaining settings unchanged.
    Figure 18.


  3. On the guide bar, change the entity selector to Solids then select the solid in the modeling window.
  4. Click Mesh in either the microdialog or on the guide bar to generate the surface mesh.
  5. Once the surface mesh is created, press Esc to exit out of the tool.

Generate Volume Mesh

  1. From the Mesh ribbon, click the Volume tool.
    Figure 19.


    The Meshing Operations dialog opens.
  2. Verify that the Mesh size option is set to Average size.
  3. Set the Average element size to 0.02.
  4. Set the Mesh growth rate to 1.0.
    Figure 20.


  5. 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.

Define Nodal Outputs and Nodal Initial Conditions

In this step, you will define the nodal output frequency and then specify the nodal initial conditions for the water column.

Define Nodal Output Frequency

  1. From the Solution ribbon, click the Field tool.
    Figure 21.


    The Field Output dialog opens.
  2. Click the Solution variables setting.
  3. Activate the Write initial conditions option.
  4. Verify that the Write results at time step interval option is active.
  5. Set the Time step interval to 1.
    Figure 22.


Define the Nodal Initial Conditions

  1. From the Solution ribbon, click the Plane tool.
    Figure 23.


  2. Click on the tank solid and verify the selection on the guide bar.
    Figure 24.


  3. Click Plane on the guide bar then click anywhere near the center of the solid.
  4. In the microdialog, click in the top-left corner, select Fluid, then click in empty space in the dialog.
  5. Change the Value field to Water.
    Figure 25.


  6. Click in the top-right corner to orient the plane with the Vector tool.
  7. In the plane definition microdialog, verify that the normal orientation is along the negative y-axis (i.e. 0, -1, 0).
    Figure 26.


  8. Click , set the coordinates to (0, 0, 0), then press Enter.
    Figure 27.


  9. On the guide bar, click to execute the command and exit the tool.
  10. Save the database.

Run AcuSolve

  1. From the Solution ribbon, click the Run tool.
    Figure 28.


    The Launch AcuSolve dialog opens.
  2. Set the Parallel processing option to Intel MPI.
  3. Optional: Set the number of processors to 4 or 8 based on availability.
  4. Deactivate the Automatically define pressure reference option.
  5. Expand the Default initial conditions tab and deactivate the Pre-compute flow option.
  6. Set the x-velocity to 0.
  7. Set the Immiscible fluid to Air (if not already set).
  8. Leave the remaining options as default and click Run to launch AcuSolve.
    Figure 29.


    The Run Status dialog opens. Once the run is complete, the status is updated and you can close the dialog.
    Tip: While AcuSolve is running, right-click on the AcuSolve job in the Run Status dialog and select View Log File to monitor the solution process.

Post-Process the Results with HM-CFD Post

  1. Once the solution is completed, navigate to the Post ribbon.
  2. From the menu bar, click File > Open > Results.
  3. Select the AcuSolve log file in your problem directory to load the results for post-processing.
    The solid and all the surfaces are loaded in the Post Browser.
  4. Click the Top face on the View Cube to align the model.
    Figure 30.


  5. Right-click on the z_pos boundary in the Post Browser and select Edit.
  6. In the display properties microdialog, set the display to volume fraction water.
  7. Activate the Legend toggle and click to refresh the range.
  8. Click , set the Colormap style to Filled, the Number of colors to 2, and the Colormap Name to Rainbow Desaturated.
    Figure 31.


  9. Click on the guide bar.
  10. Click at the bottom of the modeling window to view a live animation of the flow.
    Figure 32.


  11. Save the animation.
    1. Go to File > Screen Capture > Advanced Capture.
    2. Click on the toolbar.
    3. Uncheck Include mouse cursor.
    4. Set the frame rate to 30.
    5. Click on the toolbar then drag over the area you want to record.
    6. Click to start recording and the same button to stop recording.
    7. Name the file and save it.

Summary

In this tutorial, you successfully learned how to set up and solve a multiphase flow tank filling problem using HyperMesh CFD and AcuSolve. You started by importing the geometry and then completed the flow set up. Once the volume meshing was done, you specified the field initial conditions for the water column using the plane initialization tool. Once the solution was computed, you post-processed the results using the Post ribbon where you generated an animation of the water flow.