Prescribing Rotations and Translations

In transient simulations, you can model scenarios where a region rotates about a fixed axis, translates along a fixed direction, or a combination of both. To model rotations and translations, Simcenter STAR-CCM+ provides the Rotation, Translation, and Rotation and Translation motion models. To define rotations independently on the different parts of a region, you can use direct rotations.

For prescribed translation, you create a motion specification within the Tools > Motions node.

For prescribed rotation, you can either create a motion specification as for translation or add a direct rotation to a region.

  1. To create a direct rotation:
    • Add the rotation values directly in the region settings. See Defining Direct Rotating Motion.
    • Right-click the Tools > Motions node, select New and choose Rotation.
To create other Translation with or without Rotation motion specification:
  1. Right-click the Tools > Motions node, select New and choose one of the following models:
    • To model translation along a fixed direction, select Translation.
    • To model a combination of rotation and translation, select Rotation and Translation.
  2. Assign the motion to the relevant region.
    The prescribed motion details are listed in the following table:
    Motion Steps
    Rotation
    1. Select the Motions > Rotation node.
    2. Set Rotation Specification based on the quantities that you provide to define the rotation, for example, the rotation rate or angular velocity. For more details, refer to Rotation Motion Properties.
    3. These quantities are defined with respect to a coordinate system, which you can specify using the Coordinate System property.
    4. Depending on the selected Rotation Specification, specify the corresponding quantities (for example, the rotation rate and axis) using the relevant nodes.
    5. Optionally, you can define superposing motions. See Superposing Motions.
    Direct Rotation
    1. Select the [region] > Physics Conditions > Motion Specification Option node and set Option to Direct Rotating Motion Values.
    2. Select the Physics Values > Direct Rotating Motion > Direct Rotating Motion Values node and specify the rotation by setting the following properties:
      • Axis Direction
      • Axis Origin
      • Coordinate System
      • Rotation Rate
    3. To specify rotations for subgroups, refer to Defining Direct Rotating Motion.
    Translation
    1. Select the Motions > Translation node.
    2. Specify the velocity vector by setting the Translation Velocity property. This vector is defined with respect to a coordinate system, that you select in the Coordinate System property.

      For more information on the available properties, see Translation Motion Properties.

    3. Optionally, you can define superposing motions. See Superposing Motions.
    Rotation and Translation
    1. Select the Motions > Rotation and Translation node.
    2. For the translation motion, specify the velocity vector by setting the Translation Velocity property.
    3. For the rotation motion, specify the axis of rotation by setting the Axis Direction and Axis Origin properties. In addition, specify the rotation rate using the Rotation Rate property.

    The Translation Velocity, Axis Direction, and Axis Origin vectors are defined with respect to the same coordinate system that you select in the Coordinate System property.

    For more information on the available properties, see Rotation and Translation Motion Properties.

    When you select one of these motions, Simcenter STAR-CCM+ adds a read-only reference frame under the Tools > Reference Frame node. For more information, see Reference Frames.