Define the Fluid Model

Create the fluid domain, apply a material to it, and define the region where the flow occurs.

A fluid domain is a finite volume consisting of one or more fluid regions that are bounded by parts, exterior geometries, and openings. For external fluid flow simulations, you must define exterior geometry to cap the total space that you mesh. If your model is symmetric, you can use techniques while creating the fluid domain to reduce the amount of space that you need to mesh. This approach can significantly reduce the simulation's run time.

In this example, you create a fluid domain that surrounds only half of the drone to take advantage of the drone's symmetric design. You bound the fluid domain using the surface of the drone (a part) and a bounding box (exterior geometry). Then, you define the space between the drone and the bounding box as the fluid region. The fluid region is where air flows around the drone.

  1. From the Assistant, click Model.
    The Finite Element Model dialog box appears.
  2. From the Model options, select Create to create a finite element model (FEM).
  3. Name it Airflow Mesh, and click OK.
    Airflow Mesh A.1 appears in the tree.

    Tip: Press F3 to display the tree if it is not visible.

  4. From the Model section of the Assistant, click Model Setup .
  5. Select Include external flow.
    A bounding box appears around the drone.

  6. Apply the material definition for air to the fluid section associated with the fluid domain.
    1. Click to open the Material Palette.
    2. From the Material Palette, search for MynameEXAMPLE-Air.
      The Myname prefix is the duplication string you specified during Create the Fluid Simulation.
    3. Select MynameEXAMPLE-Air, and click OK.
      The app applies the material definition to the fluid section and closes the Material Palette.
  7. Expand the Fluid domain bounding parts section, and confirm that all five parts are selected.
  8. Resize the bounding box to enclose a symmetric half of the drone.
    1. Expand the Bounding box section.
    2. Enter the following coordinates for the Minimum and Maximum values of X, Y, and Z:

      Axis Minimum Maximum
      X -30000mm 10000mm
      Y -15000mm 0mm
      Z -15000mm 15000mm

      These coordinates create a bounding box that divides the drone into two symmetrical parts.

    3. Confirm that all bounding box faces specify No boundary layers .

      Boundary layers on the bounding box faces are useful when these faces represent a solid surface, like a road or the walls of a wind tunnel simulator. In this example, you simulate the drone flying in normal operating conditions with no solid surfaces within close proximity to the drone.

  9. Specify the region that contains the fluid.
    1. Expand the Regions section.
    2. Select any surface of the drone that is also inside the bounding box.
      A glyph of a blue cube with a stem appears on that surface.
    3. If required, click Flip direction to immerse the cubical portion of the glyph in the fluid volume.


  10. Click OK.