Defining Mesh Operations

Complete the operations pipeline by adding mesh operations. In this tutorial, you generate a polyhedral mesh for the fluid and a tetrahedral mesh for the solid. To speed up convergence of the flow solution and prevent reversed flow at the outlet, you also extrude the fluid mesh at the outlet.

Start by defining the operations that generate the fluid mesh:

  1. Right-click the Geometry > Operations node and select New > Mesh > Automated Mesh.
  2. In the Create Automated Mesh Operation dialog:
    1. Set the following properties:
      Property Setting
      Parts Internal Fluid
      Surface Meshers Surface Remesher
      Core Volume Meshers Polyhedral Mesher
      Optional Boundary Layer Meshers Prism Layer Mesher
    2. Click OK.
  3. Rename the Operations > Automated Mesh node to Fluid Polyhedral Mesh.
Define appropriate mesh controls. The curves on the fluid surface have a radius of curvature that is larger than the overall geometry length scales. To obtain a uniform mesh, you can deactivate the curvature and proximity refinement for the surface mesh:
  1. Edit the Fluid Polyhedral Mesh node and set the following properties:
    Node Property Setting
    Meshers > Surface Remesher Perform Curvature Refinement Deactivated
    Perform Proximity Refinement Deactivated
    Default Controls
    Base Size Base Size 2.0 mm
    Minimum Surface Size Percentage of Base 25.0
    Prism Layer Controls > Prism Layer Total Thickness Percentage of Base 64.0
To prevent reversed flow, you extrude the fluid mesh at the outlet. Although the extruded mesh is not an accurate representation of an exhaust pipe, it is appropriate for this case where you are mainly concerned with stress concentrations in the solid region. To extrude the fluid mesh at the outlet:
  1. Right-click the Operations node and select New > Surface Preparation > Surface Extruder.
  2. In the Create Surface Extruder Operation dialog:
    1. Set the following properties:
      Property Setting
      Input Parts Internal Fluid
      Input Part Surfaces Internal Fluid > Fill Holes > Manifold.ToTurbo
      Extrusion Distance 0.2 m
      Create Volume Extruder Operation From Output Parts Activated
    2. Click OK.
  3. Rename the following nodes:
    Node Rename to
    Operations
    Surface Extruder Fluid Outlet Surface Extruder
    Volume Extruder Fluid Outlet Volume Extruder
    Parts > Surface Extruder Fluid Outlet Extrusion
  4. Expand the Operations > Fluid Outlet Volume Extruder > Controls node and set the following properties:
    Node Property Setting
    Number of Layers Number of Layers 40
    Stretching Function Stretching Method One Sided Hyperbolic
For the solid manifold, you define a mesh operation that generates a tetrahedral mesh. Tetrahedral meshes are suitable for finite element solvers.
  1. Right-click the Geometry > Operations node and select New > Mesh > Automated Mesh.
  2. In the Create Automated Mesh Operation dialog:
    1. Set the following properties:
      Property Setting
      Parts Manifold
      Surface Meshers Surface Remesher
      Core Volume Meshers Tetrahedral Mesher
    2. Click OK.
  3. Rename the Operations > Automated Mesh node to Manifold Tetrahedral Mesh.
In this simulation, you assign multiple part surfaces to the same boundaries, based on the boundary conditions that you apply. During mesh generation, Simcenter STAR-CCM+ automatically preserves the perimeter of boundaries, but not the perimeter of the single part surfaces. As later you constrain three surfaces that belong to the same boundary, instruct Simcenter STAR-CCM+ to preserve the perimeter of each part surface during meshing:
  1. Select the Manifold Tetrahedral Mesh node and set Preserve Surface Perimeters to All part surface perimeters.
  2. Expand the Manifold Tetrahedral Mesh > Default Controls node and set the following properties:
    Node Property Setting
    Base Size Base Size 5.0 mm
    Minimum Surface Size Percentage of Base 50.0
    The geometry parts and operations pipeline appear as follows:

  3. Save the simulation.