Interpolate Geometry Motion

You can implement Geometry motion over multiple Time Steps using the setGeometryMotion method.

To interpolate Geometry motion:
Specify an action time that is greater than the Time Step that EDEM is set to use, the motion of a Geometry is automatically interpolated over the specified number of Time Steps.
Note: Geometry motion is linearly interpolated in both linear (translation) and spherical (orientation) components of motion. The linear interpolation is performed using the LERP algorithm and spherically using the SLERP algorithm.
The following best practices ensure that the desired results are achieved:
  1. When setting an action time on a Geometry, you must set it for a multiple of an EDEM Time Step. Motions are guaranteed to be completed for the last Time Step, and therefore, the result of setting a fractional action time is that the motion will be completed up to one Time Step before EDEM completes its simulation step.
  2. Linear interpolation always acts in a straight line between two points. Therefore, non-linear motions will have a degree of positional error associated with them. These positional errors must be factored in when selecting an appropriate data exchange interval.
  3. Spherical linear interpolation always acts on the minimal path. Therefore, a motion with an orientation change of over 180 degrees will result in rotation in the opposite direction (this is the minimal path).
  4. Spherical linear interpolation with an orientation change of exactly 180 degrees is undefined. Since there are multiple paths to achieve this, setting a motion with an orientation change of 180 degrees can result in undefined behavior.
  5. The Geometry velocities input using the setGeometryMotion is maintained for the duration of the movement and therefore there is an effect on the particle-equipment contact results. For the vast majority of DEM simulations, equipment accelerations are significantly lower than those of the material interacting with them and changes in Geometry velocity should not be extreme. Time Step ratios of the order of 10 should not have an impact effect on the results of a simulation.
  6. The precise sensitivity of the Time Step ratio is simulation-dependent. It is important that you determine your own acceptable ratio through appropriate numerical experiments.
  7. Geometries that have an associated velocity vector will be rendered in EDEM Analyst with an arrow to indicate the direction of motion of the Geometry. The arrow is drawn using the velocity field of the target Geometry. To ensure that the velocity vector is displayed correctly, exercise caution when calculating the Geometry velocity so that each of the velocity vector's components [x, y, and z] are factored in. For example, if the Geometry's motion is only along the y-axis, you must explicitly set the x and z components of the velocity vector to zero. Failure to implement this functionality could result in the Geometry velocity vector not being displayed as expected.