Creating the Overset Mesh Interfaces with Prism Layer Shrinkage

The overset mesh approach generally requires one static mesh, (the background mesh), and one or more overset meshes that contain the surfaces describing the moving geometry. The overset meshes overlap with the background mesh and can also overlap with each other.

In the course of the simulation, variable values are exchanged through interpolation between the meshes in the individual regions. To associate the regions with each other and to enable this variable exchange, you create overset interfaces between the background region and the overset regions as well as between the two overset regions.

The boundaries of the counter-rotating lobes approach each other closely forming a small gap between them. Overset mesh modeling requires a minimum of two to three active cell layers to resolve a gap between two wall boundaries. To ensure that this requirement is always met, you must activate prism layer shrinkage. Prism layer shrinkage morphs the prism layer cells between wall boundaries in close proximity.

Create the overset mesh interfaces as follows:

  1. Between the region of Lobe 1 and the background region:
    1. Multi-select the regions Lobe 1 and BG.
    2. Right-click on any of them and select Create Interface > Overset Mesh.
  2. Between the region of Lobe 2 and the background region:
    1. Multi-select the regions Lobe 2 and BG.
    2. Right-click on any of them and select Create Interface > Overset Mesh.
  3. Between the regions of Lobe 1 and Lobe 2:
    1. Multi-select the regions Lobe 1 and Lobe 2.
    2. Right-click on any of them and select Create Interface > Overset Mesh.
  4. To account for the small gaps that occur, adjust the overset mesh interface settings:
    1. Multi-select the interfaces Overset Mesh 1, Overset Mesh 2, and Overset Mesh 3, right-click on one of the selected interfaces and select Edit.
    2. In the Multiple Objects dialog, expand the Physics Conditions > Overset Hole Cutting Options node and activate Prism Layer Shrinkage.
    3. Expand Physics Conditions > Interpolation Option and set Option to Linear. Click Close.

      Setting the Interpolation Option to Linear enhances the accuracy of the variable value interpolation for all three overset mesh interfaces.

  5. Save the simulation.