Difference between revisions of "LeaveLimit Command"
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<li>Particles that are forced back into the grid might lead to nonphysical or erroneous results. Analyses that have many particles leaving the grid should be highly suspect. | <li>Particles that are forced back into the grid might lead to nonphysical or erroneous results. Analyses that have many particles leaving the grid should be highly suspect. | ||
<li>Particles that are deleted are | <li>Particles that are deleted are moved to the lower-left corner of the grid. That corner element needs to be empty and away from other particles. | ||
<li>This command is must useful when the particle leaving the grid itself is already a numerical artifact and therefore forcing it back in may not be making things any worse. A common numerical artifact is an isolated particle that picks up a nonphysical acceleration propelling it off the grid. This command can trap those problem particles and keep the analysis running for the bulk of the remaining particles. | <li>This command is must useful when the particle leaving the grid itself is already a numerical artifact and therefore forcing it back in may not be making things any worse. A common numerical artifact is an isolated particle that picks up a nonphysical acceleration propelling it off the grid. This command can trap those problem particles and keep the analysis running for the bulk of the remaining particles. | ||
<li>If the <tt>LeaveLimit</tt> is greater than 1 and the analysis eventually finishes, the output file will include a warning when the first particle left left the grid and a count of the number of steps that had at least one new particle leaving the grid. | <li>If the <tt>LeaveLimit</tt> is greater than 1 and the analysis eventually finishes, the output file will include a warning when the first particle left left the grid and a count of the number of steps that had at least one new particle leaving the grid. | ||
Revision as of 23:50, 31 December 2020
The LeaveLimit command determines how an MPM analysis responds when a particle leaves the grid:
Use LeaveLimit
In scripted files, the command is
LeaveLimit (maxNum)
In XML input files, the command, which must be within the <MPMHeader> element, is
<LeaveLimit>(maxNum)</LeaveLimit>
where |(maxNum)| is the number of particles leaving the grid that are tolerated before an analysis is stopped. If (maxNum) is positive, a particle that leaves the grid will be moved back into the grid. If (maxNum) is negative, particles that leave the grid will be deleted from the simulation. If |(maxNum)| particles leave the grid, the simulation will stop.
If this command is omitted, the default is positive and set to 1% of the particles. Setting (maxNum) to 1 will cause a simulation to stop if any particle leaves the grid.
Notes
- Particles that are forced back into the grid might lead to nonphysical or erroneous results. Analyses that have many particles leaving the grid should be highly suspect.
- Particles that are deleted are moved to the lower-left corner of the grid. That corner element needs to be empty and away from other particles.
- This command is must useful when the particle leaving the grid itself is already a numerical artifact and therefore forcing it back in may not be making things any worse. A common numerical artifact is an isolated particle that picks up a nonphysical acceleration propelling it off the grid. This command can trap those problem particles and keep the analysis running for the bulk of the remaining particles.
- If the LeaveLimit is greater than 1 and the analysis eventually finishes, the output file will include a warning when the first particle left left the grid and a count of the number of steps that had at least one new particle leaving the grid.