Superposing Motions on a Trajectory Motion

Simcenter STAR-CCM+ allows you to superpose rotations and translations on trajectory motions. With superposing motions, the moving region translates along the specified trajectory and, additionally, rotates and translates as prescribed by the superposing motions.

In addition to the Rotation and Translation motions, which can be superposed on any type of rigid motion, Simcenter STAR-CCM+ provides specific types of superposing rotations that work exclusively with the Trajectory motion. These specific motions define the orientation of the region with respect to the local curvature of the trajectory:

Tangential Rotation—the rotation of the region is defined by the rotation of the curve tangent.
Constrained Rotation—the rotation of the region is defined using a two-point constraint. Two points at a specified offset are always in contact with the curve. The region rotates based on the rotation of the line that connects the two points. A typical example is the motion of a chassis on a fixed paint dipping skid.
Vantage Point Rotation—the rotation of the region is defined by the rotation of the line that connects the current position point on the trajectory with a specified point (the vantage point).

To specify the first level superposing motion with respect to the root trajectory motion:

Right-click the Motions > Trajectory > Superposing Motions node and select the required type of motion.
Set the superposed motion properties.
- For the Rotation motion, depending on the Rotation Specification selected, you specify associated rotation motion properties. For more details, refer to Rotation Motion Properties.
- For the Translation motion, specify Translation Velocity as constant, global parameter or field function.
- For the Constrained Rotation motion, specify Horizontal Offset between the points. For a example setup, refer to the Defining the Trajectory Motion with Constrained Rotation in the paint dipping tutorial.
- For the Vantage Point Rotation motion, specify the position of the vantage point in Point.

Underneath the first level superposing motion of the trajectory motion, you can define further an embedded superposing motion from either Rotation or Translation.

Right-click Motions > Trajectory > Superposing Motions > [superposing motion] > Superposing Motions node and select New > Rotation / Translation.

Note	In Simcenter STAR-CCM+ all the coordinate systems of the root and superposing motions are created and managed automatically. However, the origin and orientation of a child coordinate systems are taken over from the parent coordinate system. You modify the settings in case of deviation.