5.2.1.7. Partial Enclosure Example

If your problem has non-meshed internal enclosures that are not fully closed, you can use a partial enclosure to allow the open parts of the enclosure to radiate to a specified far-field condition based on the view factor of the opening.

Warning

Gaps in a partial enclosure (e.g. near contact surfaces or from forgetting to add a sideset to the enclosure definition) will be treated as part of the enclosure opening and allow radiation to the far-field condition through those openings. Ensure you have well-formed enclosures when using the partial enclosure feature.

5.2.1.7.1. Problem Files

The files required for this example can be downloaded here, or found at $TESTS/aria_rtest/example/training/enclrad (where TESTS=/projects/sierra/tests in a CEE environment, or your Sierra test distribution otherwise).

The geometry for this example is a cylinder with a cup open on one end. The cup and ends of the cylinder (red surfaces) make a partial enclosure that is open to a specified environment. Faces inside the cup can radiate to other parts of the cup, and to the environment.

Blocks in the mesh

5.2.1.7.2. Input Deck Modification

To use a partial enclosure, you must make the following changes to the existing enclosure definitions.

  1. Define a viewfactor smoothing block that uses no smoothing (smoothing partial enclosures is not allowed)

# Aria Region level
Begin Viewfactor Smoothing vf_smooth_none
  Method = NONE
End

  1. Define the partial enclosure area, temperature, and emissivity in the enclosure definition block - make sure to set the smoothing to use the block you defined with no smoothing.

Note

The partial enclosure area is always required, but has no effect on the solution when the partial enclosure emissivity is 0 or 1.

# Aria Region
Begin Enclosure Definition enc1
  Add Surface surface_1

  Use Viewfactor Calculation vf_hemicube
  Use Viewfactor Smoothing vf_smooth_none
  Use Radiosity Solver rad_solver

  # Define partial enclosure
  partial enclosure emissivity = 1.0
  partial enclosure area = 1 # arbitrary since emissivity = 1
  partial enclosure temperature = 50.0
End

Warning

When using the partial enclosure to represent a real object with 0 < emissivity < 1 you must use the object’s real area or the results will be incorrect.

For example, if the partial enclosure environment is really a hemisphere surface of aluminum using real aluminum emissivity (as in the image below) but you want to use a partial enclosure since it will be held at a constant temperature, you must still set the area to the actual area of the hemisphere you want to model.

Blocks in the mesh