Defining Mesh Operations for the Airgap

In electric machine applications, it is common to generate a tetrahedral mesh for parts with a complex geometry and then extrude it to the parts that have a more regular geometry. For illustration purposes, this tutorial adopts the same meshing strategy, although this simple geometry could be meshed directly using the directed mesher.

In this simulation, you only model a 45 degree sector of the full geometry. To simulate the behavior of the full geometry, you create periodic contacts between the side surfaces of the sector geometry.

  1. To create these contacts, set up a Contact Creator operation:
    1. Right-click the Geometry > Operations node and select New > Surface Preparation > Contact Creator.
    2. In the Create Contact Creator Operation dialog, click () Show/Hide Filters, and activate nonAirgapParts.
    3. Select all the parts that appear in the list.


    4. Click OK.
    5. Rename the Operations > Contact Creator node to Contact Creator Periodic Base.
    6. Select the Operations > Contact Creator Periodic Base node and set Contact Type to Periodic Rotation.
  2. Right-click the Operations node and select New > Mesh > Automated Mesh.
  3. In the Create Automated Mesh Operation dialog:
    1. Select Coil, Coil2, Fixed, Magnet, and Rotating.
    2. In the Select Meshers group box, choose the following meshers:
      Surface Meshers Surface Remesher
      Core Volume Meshers Tetrahedral Mesher
    3. Click OK.
  4. Edit the Operations > Automated Mesh > Default Controls > Base Size node and set Value to 0.05 m.
To refine the mesh at the interface between the air regions and the airgap regions:
  1. Right-click the Operations > Automated Mesh > Custom Controls node, and select New > Surface Control.
  2. Edit the Custom Controls > Surface Control node and set the following properties:
    Node Property Setting
    Surface Control Part Surfaces Fixed > Surfaces > Interface
    Rotating > Surfaces > Interface
    Controls > Target Surface Size Target Surface Size Custom
    Values > Target Surface Size Size Type Absolute
    Absolute Size 0.025 m
  3. Right-click the Operations node and select New > Mesh > Volume Extruder.
  4. In the Create Volume Extruder Operation dialog:
    1. Select the following parts:
      Property Setting
      Input Parts
      • Coil_Extrusion
      • Coil2_Extrusion
      • Fixed_Extrusion
      • Magnet_Extrusion
      • Rotating_Extrusion
    2. Click OK.
  5. Select the Volume Extruder > Controls > Number of Layers and set Number of Layers to 4.
  6. To account for the motion of the rotating portion of the airgap, define a transform operation that updates the position of its associated parts according to the rotation motion:
    1. Right-click the Operations node and select New > Surface Preparation > Transform.
    2. In the Create Transform Operation dialog, select Airgap_Rotating and click OK.
    3. Right-click the Operations > Transform > Transforms node and select New > Motion.
    4. Select the Transforms > Motion node and set Motion to Rotation.
  7. Define an imprint operation between the rotating airgap and the fixed airgap parts:
    1. Right-click the Operations node and select New > Boolean > Imprint.
    2. In the Create Imprint Operation dialog:
      1. Select Airgap_Fixed and Airgap_Rotating.
      2. Activate Perform CAD Imprint.
      3. Click OK.
      4. Select the Operations > Imprint > Controls > Resulting Part Surfaces node and set Put Results In to New Part Surfaces.
  8. Use the surface extruder to extrude the tetrahedral mesh:
    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
        • Airgap_Fixed
        • Airgap_Rotating
        Input Part Surfaces
        • Airgap_Fixed > Surfaces > Top
        • Airgap_Rotating > Surfaces > Top
        Create New Part Per Part
        Extrusion Distance 0.12 m
      2. Click OK.
    3. Rename the Operations > Surface Extruder 2 node to Airgap Surface Extruder.
    4. Expand the Geometry > Parts node.
    5. Rename the extruded parts as follows:
      Current node name: Rename to:
      Surface Extruder 2 Airgap_Rotating_Extrusion
      Surface Extruder 2 2 Airgap_Fixed_Extrusion

For airgap remeshing, you require periodic contacts between the rotating and the fixed airgap parts.

  1. To create the periodic contacts, set up a contact creator operation:
    1. Right-click the Geometry > Operations node and select New > Surface Preparation > Contact Creator.
    2. In the Create Contact Creator Operation dialog, click () Show/Hide Filters, and activate AirgapParts.
    3. Select all the parts that appear in the list.


    4. Click OK.
    5. Rename the Operations > Contact Creator node to Contact Creator Periodic Airgap.
    6. Select the Operations > Contact Creator Periodic Airgap node and set Contact Type to Periodic Rotation.
  2. Create a tetrahedral mesh for the airgap parts:
    1. Right-click the Operations node and select New > Mesh > Automated Mesh.
    2. In the Create Automated Mesh Operation dialog:
      1. Select Airgap_Fixed and Airgap_Rotating.
      2. In the Select Meshers group box, choose the following meshers:
        Surface Meshers Surface Remesher
        Core Volume Meshers Tetrahedral Mesher
      3. Click OK.
    3. Rename the Operations > Automated Mesh 2 node to Airgap Tet Mesh.
To specify the size of the tetrahedral elements and create a conformal mesh across part contacts:
  1. Edit the Operations > Airgap Tet Mesh node and set the following properties:
    Node Property Setting
    Meshers > Tetrahedral Mesher Conformal to Existing Mesh Activated
    Default Controls
    Base Size Base Size 0.05 m
    Conformal Contacts Contacts Airgap_Fixed/Fixed > Contact > Interface/Interface and Rotating/Airgap_Rotating > Contact > Interface/Interface
  2. Right-click the Operations node and select New > Mesh > Volume Extruder.
  3. In the Create Volume Extruder Operation dialog:
    1. Select Airgap_Fixed_Extrusion and Airgap_Rotating _Extrusion.
    2. Click OK.
  4. Rename the Operations > Volume Extruder 2 node to Airgap Volume Extruder.
  5. Select the Airgap Volume Extruder > Controls > Number of Layers and set Number of Layers to 4.
  6. Define an imprint operation between the rotating airgap and the rotating parts:
    1. Right-click the Geometry > Operations node and select New > Boolean > Imprint.
    2. In the Create Imprint Operation dialog:
      1. Select Airgap_Rotating_Extrusion and Rotating_Extrusion.
      2. Click OK.
      As the extrusion parts are not 3D-CAD parts, you do not activate Perform CAD Imprint.
  7. Define an imprint operation between the fixed airgap and the fixed parts:
    1. Right-click the Geometry > Operations node and select New > Boolean > Imprint.
    2. In the Create Imprint Operation dialog:
      1. Select Airgap_Fixed_Extrusion and Fixed_Extrusion.
      2. Click OK.

In this simulation, the airgap remeshing process requires a repeating interface between the rotating airgap region and the fixed airgap region. This repeating interface is created from a periodic contact.

  1. To create the periodic contact between the rotating and fixed airgap parts:
    1. Delete any existing in-place contact between these parts:
      1. Right-click the Contacts > Airgap_Rotating/Airgap_Fixed > Repeating Interface/Repeating Interface node and select Delete. Accept the warning in the dialog.
    2. Multi-select the Geometry > Parts > Airgap_Fixed > Surfaces > Repeating Interface and Geometry > Parts > Airgap_Rotating > Surfaces > Repeating Interface nodes.
    3. Right-click one of the selected nodes and select Create Periodic.
  2. Save the simulation.