Generating the Extruder Mesh

Use the extruder mesh to extend the domain in the inflow and outflow directions. As the flow in these directions is generally normal to the cell faces, it is acceptable to generate stretched cells. In this tutorial, the largest cells have an aspect ratio of approximately 300.

First, extend the domain in the upstream direction:

  1. Right-click the Geometry > Operations node and select New > Surface Preparation > Surface Extruder.
  2. In the Create Surface Extruder dialog, set:
    1. Input Parts to Static Region.
    2. Input Part Surfaces to Static Region > Inlet.
    3. Create New Part to Single New Part.
    4. Output Part Surfaces to Single Side.
    5. Extrusion Distance to 1.0 m.
    6. Activate Create Volume Extruder from Output Parts and Execute Surface Extruder Operation Upon Creation.
  3. Click OK.
  4. Expand the Geometry > Operations > Volume Extruder > Controls node and set the following properties:
    Node Property Setting
    Number of Layers Number of Layers 10
    Stretching Function Stretching Method One Sided Geometric
    One Sided Options Stretching Mode Thickness Ratio
    One Sided Options > Thickness Ratio Thickness Ratio 2
Now extend the domain in the downstream direction:
  1. Right-click the Geometry > Operations node and select New > Surface Preparation > Surface Extruder.
  2. In the Create Surface Extruder dialog, set:
    1. Input Parts to Static Region.
    2. Input Part Surfaces to Static Region > Outlet.
    3. Create New Part to Single New Part.
    4. Output Part Surfaces to All Pertinent Sides.
    5. Extrusion Distance to 3.0 m.
    6. Activate Create Volume Extruder from Output Parts and Execute Surface Extruder Operation Upon Creation.
  3. Click OK.
  4. Expand the Geometry > Operations > Volume Extruder 2 > Controls node and set the following properties:
    Node Property Setting
    Number of Layers Number of Layers 40
    Stretching Function Stretching Function One Sided Geometric
    One Sided Options Stretching Function Thickness Ratio
    One Sided Options > Thickness Ratio Thickness Ratio 2
    NoteTwo part placeholders appear under the Geometry > Parts node: Surface Extruder (upstream extension) and Surface Extruder 2 (downstream extension).
  5. Within Geometry > Parts , rename these parts to Upstream Extension and Downstream Extension respectively.
  6. Multi-select the Upstream Extension and Upstream Extension nodes, right-click and select Assign Parts to Regions.
  7. In the Assign Parts to Regions dialog:
    1. Select Create a Region for Each Part.
    2. Select Create a Boundary for Each Part Surface.
    3. Click Apply, then Close.
  8. In the Mesh Generation Toolbar, click Generate Volume Mesh.
  9. To create a new Mesh Scene, right-click Scenes > New > Mesh and examine the mesh.
  10. Save the simulation.
    NoteThe boundaries Static Region.Inlet and Static Region.Outlet now form interfaces between the Static Region and the Upstream Extension and Downstream Extension regions respectively. The propeller shaft extension is named Static Region.Shaft as default, and the outer boundaries on the new regions are named Default and Static Region.Far Field respectively.