Preparing and Generating the Mesh

After assigning parts to regions and setting the boundary types, you can define the mesh settings for the volume mesh. For this simulation, you generate an anisotropic and aligned volume mesh based on an initial quadrilateral surface mesh.

The polyhedral mesher is used in conjunction with the advancing layer mesher to build a suitable mesh for the fluid volume. In order to resolve the boundary layer, the number of prism layers is set to 20 and the prism layer near wall thickness is set to a value consistent with y+ ~ 1. For external aerodynamic cases, 20-30 prism layers are typically used.

  1. To set up the volume mesh:
    1. Right-click the Geometry > Operations node and select New > Mesh > Automated Mesh.
    2. In the Create Automated Mesh Operation dialog:
      1. From the Parts list, select Fluid.
      2. Within Select Meshers, select the following meshers in order:
        Group Mesher
        Surface Meshers Surface Remesher
        Core Volume Meshers Polyhedral Mesher
        Optional Boundary Layer Meshers Advancing Layer Mesher
      3. Click OK.
    3. Select the Geometry > Operations > Automated Mesh node and in the Properties window, set Mesher Execution Mode to Parallel.
    4. Select the Automated Mesh > Meshers > Advancing Layer Mesher node and set Distribution Mode to Wall Thickness.
  2. Edit the Automated Mesh > Default Controls node, click Expand/Contract Tree, and set the following properties:
    Node Property Setting
    Base Size Value 0.2 m
    Minimum Surface Size Percentage of Base 15.0
    Surface Growth Rate Surface Growth Rate Slow
    Number of Prism Layers Number of Prism Layers 20
    Prism Layer Near Wall Thickness Prism Layer Near Wall Thickness 1.55E-6 m
    Prism Layer Total Thickness Size Type Absolute
    Absolute Size 0.005 m
  3. As flow behavior far from the wing is not particularly important for this simulation, you can specify a coarser mesh on the far-field. To do so:
    1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Surface Control.
    2. Rename the Surface Control node to FarField.
    3. Edit the Custom Controls > Farfield node and set the following:
      Node Property Setting
      Farfield Part Surfaces Fluid > Surfaces > Farfield
      Fluid > Surfaces > Symmetry
      Controls > Target Surface Size Target Surface Size Custom
      Values > Target Surface Size Size Type Absolute
      Absolute Size 3.0 m
  4. To capture the turbulent flow conditions that occur behind the wing, set up a wake refinement control:
    1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Surface Control.
    2. Rename the Surface Control node to Wake Refinement.
    3. Edit the Custom Controls > Wake Refinement node and set the following:
      Node Property Setting
      Wake Refinement Part Surfaces Fluid > Surfaces > TrailingEdgeSurface
      Controls > Wake Refinement Specify wake refinement options Activate
      Values > Wake Refinement Distance 5.0 m
      Spread Angle 5.0 deg
Anisotropic meshing helps to reduce the number of mesh faces while maintaining the solution accuracy. In this tutorial, you specify anisotropic meshing on the leading, trailing and side edges of the wing. The image below shows a mesh with and without anisotropic meshing.

  1. To use anisotropic meshing:
    1. Select the Automated Mesh > Meshers > Surface Remesher node and set Meshing Method to Quad Dominant.
    2. To obtain a uniform mesh, deactivate the following properties:
      1. Perform Curvature Refinement
      2. Perform Proximity Refinement

      By disabling the Curvature and Proximity controls on the wing, the mesh is refined using only the anisotropic size control applied on the leading and trailing edge. The setup generates an anisotropic mesh with a much smaller number of faces.

  2. To refine the mesh on the leading edge:
    1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Curve Control.
    2. Rename the Curve Control node to Leading Edge.
    3. Edit the Custom Controls > Leading Edge node and set the following:
      Node Property Setting
      Leading Edge Part Curves Fluid > Curves > Leading Edge
      Controls > Anisotropic Surface Size > Specify anisotropic surface size settings Activate
      Specify anisotropic mesh distribution between close Part Curves Activate
      Values > Anisotropic Surface Size Number of Constant Layers 3
      First Layer Thickness Size Type Absolute
      Absolute Size 0.001 m
      Minimum Layer Size in Narrow Regions of Thin Areas Size Type Absolute
      Absolute Size 3.0E-4 m
  3. To refine the mesh on the side:
    1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Curve Control.
    2. Rename the Curve Control node to Wing Side.
    3. Edit the Custom Controls > Wing Side node and set the following:
      Node Property Setting
      Wing Side Part Curves Fluid > Curves > Wing Side
      Controls > Anisotropic Surface Size > Specify anisotropic surface size settings Activate
      Specify anisotropic mesh distribution between close Part Curves Activate
      Values > Anisotropic Surface Size Number of Constant Layers 3
      First Layer Thickness Size Type Absolute
      Absolute Size 3.0E-4 m
      Minimum Layer Size in Narrow Regions of Thin Areas Size Type Absolute
      Absolute Size 2.5E-4 m
  4. To refine the mesh on the trailing edge:
    1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Curve Control.
    2. Rename the Curve Control node to Trailing Edge.
    3. Edit the Custom Controls > Trailing Edge node and set the following:
      Node Property Setting
      Trailing Edge Part Curves Fluid > Curves > Lower Trailing Edge, Trailing Edge Side and Upper Trailing Edge
      Controls > Anisotropic Surface Size > Specify anisotropic surface size settings Activate
      Specify anisotropic mesh distribution between close Part Curves Activate
      Values > Anisotropic Surface Size Number of Constant Layers 6
      Min Number of Layers 3
      First Layer Thickness Size Type Absolute
      Absolute Size 4.25E-4 m
      Minimum Layer Size in Narrow Regions of Thin Areas Size Type Absolute
      Absolute Size 1.5E-4 m
Now that all mesh settings are defined, you can generate the volume mesh.
  1. Click (Generate Volume Mesh) in the toolbar or select Generate Volume Mesh in the Mesh menu.

    The run and progress of the meshers are displayed in the Output window.

  2. To display the volume mesh, from the Vis toolbar, click (Create/Open Scenes) and select Mesh.
  3. Save the simulation.