Setting Up and Generating the 2D Mesh

Before you can generate a 2D mesh as part of an automated mesh pipeline, you must badge the part. Badging a part notifies Simcenter STAR-CCM+ that this part will be used to generate a 2D mesh. The requirement for this feature is that one separate surface must lie on the Z = 0 plane. In a previous section, you renamed the surface that lies on the Z = 0 plane to Surface for 2D Mesh, so in this case the requirement is met. A volume mesh is generated using trimmed cells. To make sure the y+ value calculated by the turbulence model is around 50, do not refine the mesh near the walls.

To set up and generate the 2D mesh:
  1. Assign parts to regions:
    1. Right-click the Parts > Backward Facing Step node and select Assign Parts to Regions.
    2. In the Assign Parts to Regions dialog, select Create a Region for Each Part and Create a Boundary for Each Part Surface.


    3. Click Apply then Close.
      A new region is created. Each labeled surface is now a separate boundary in the region.
  2. Set the boundary types for the inlet and outlet boundaries:
    1. Select the Regions > Backward Facing Step > Boundaries > Inlet node and set the Type to Velocity Inlet.
    2. Select the Outlet node and set the Type to Pressure Outlet.
  3. Badge the backwards facing step part for 2D Meshing:
    1. Right-click the Geometry > Operations node and select New > Mesh > Badge for 2D Meshing.
    2. In the Create Badge for 2D Meshing Operation dialog, select Backward Facing Step from the Parts list, and click OK.
      A new operation, Badge for 2D Meshing is added below the Operations node.
    3. Right-click the Badge for 2D Meshing node and select Execute.
      Expand the Geometry > Parts > Backward Facing Step > Surfaces node to see the badge added next to the surfaces that are identified for 2D meshing.

      When you execute this mesh operation, you generate a 2D mesh. The surface with the dark red tag (on the node icon) becomes the 2D region, while the surfaces with the yellow tags become 2D boundaries.
  4. Generate a volume mesh using trimmed cells:
    1. Right-click the Geometry > Operations node and select New > Mesh > Automated Mesh.
    2. In the Create Automated Mesh Operation dialog, select Backward Facing Step from the Parts list, then select the following meshers, in order:
      Group Box Mesher
      Surface Meshers Surface Remesher
      Core Volume Meshers Trimmed Cell Mesher
    3. Click OK to close the window.
  5. Modify the mesher parameters:
    1. Select the Automated Mesh > Meshers > Trimmed Cell Mesher node and activate Perform Mesh Alignment.
      This option allows you to align the mesh at a specific point, for example at the top corner of the step.
    2. Edit the Automated Mesh > Default Controls node and set the following properties:
      Node Property Setting
      Base Size Value 0.2 m
      Minimum Surface Size Percentage of Base 100
      Mesh Alignment Location Location [0.0, 1.0, 0.0] m
  6. Create a volumetric control to refine the mesh near the bottom wall:
    1. Right-click the Operations > Automated Mesh > Custom Controls node and select New > Volumetric Control.
      A new node, Volumetric Control, is added below the Custom Controls node.
    2. Select the Volumetric Control node and set Parts to Refinement Box.
    3. Select the Volumetric Control > Controls > Trimmer node and activate Customize Isotropic Size option.
      A new node, Custom Size, is added to the Volumetric Control > Values node.
    4. Select the Values > Custom Size node and set Percentage to Base to 50.
  7. Generate the 2D mesh:
    1. Click (Generate Volume Mesh).
    2. Create a mesh scene to examine the mesh.
      The 2D mesh is shown below:

  8. Save the simulation.