Create the FEM and Define the Fluid Domain

Create a fluid domain to define the volume through which the fluid flows.

Instead of manually performing operations to extract the geometry for the fluid's location, you can create a fluid domain to serve as an abstract representation of where the fluid is contained.

In this example, the air flow from the cooling fan acts as the fluid as it passes through the CPU board. You select all six mechanical features as the structural parts that contain the fluid, and you select the bottom surface as the region where the fluid flows. Finally, you define the openings of the fluid domain to represent the inlet/outlets through which the fluid enters/exits the model. The inlet is the round vent above the heat sink, and the outlets are the 10 rectangular vents on the ends of the model.

  1. From the Setup section of the action bar, click Finite Element Model .
  2. From the Model options, select Create to create a FEM.
  3. Name it FEM_ConHT, and click OK.
    FEM_ConHT A.1 appears in the tree.
  4. From the View section of the action bar, click Fit All In.

    The app enlarges or shrinks the model to fit in the 3D area.

  5. From the standard area of the action bar, click Model .
    The model opens in Fluid Model Creation.
  6. From the Setup section of the action bar, click Fluid Domain .
  7. Name the fluid domain Enclosure_1.
  8. From the Definition field, select Extract from part boundaries.
  9. Select the structural parts that contain the fluid and are surrounded by the fluid flow.
    1. Click on the Parts container.
    2. From the 3D area, click and drag a rectangle around the entire model to select the heat sink, chip, and enclosure.
      The Support field indicates that six mechanical features are selected.

    3. Select Allow boundary layers to be added to enable the creation of boundary layers along the part boundary.
    4. Click OK.
  10. Specify the regions where the fluid flows.
    1. Click on the Regions container.
    2. Select the inside bottom surface, which is next to the chip.
      A glyph appears, indicating that the fluid is located outside the enclosure.
    3. Click Flip direction to specify that the fluid is passing through the enclosure rather than around it.
      The glyph moves to the interior of the enclosure.
    4. Click OK.

  11. Indicate the openings of the fluid domain. There are 11 openings to define, all of them on the CPU surface enclosure. One opening is the round vent above the heat sink, and the other 10 openings are the small rectangular vents on the ends of the enclosure.
    1. Click on the Openings container.
    2. Define the circular opening by selecting the two inner edges of the round vent.

      Tip: To help you select the required edges, click Edge Selection from the context toolbar.

      A circular disc glyph shows the location of the opening.
    3. Click OK.
    4. Define a rectangular vent opening by selecting each of the four edges of the small rectangular vents, and click OK.
    5. Similarly, repeat Step d to define the other nine openings.



  12. Click OK.