Difference between revisions of "LeaveLimit Command"
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LeaveLimit (maxNum) | LeaveLimit (maxNum) | ||
In XML input files, the command, which must be within the [[MPM Input Files# | In XML input files, the command, which must be within the [[MPM Input Files#MPM Header|<tt><MPMHeader></tt> element]], is | ||
<LeaveLimit>(maxNum)</LeaveLimit> | <LeaveLimit>(maxNum)</LeaveLimit> | ||
where <tt>(maxNum)</tt> is the number of | where <tt>|(maxNum)|</tt> is the number of particles leaving the grid that are tolerated before an analysis is stopped. If <tt>(maxNum)</tt> is positive, a particle that leaves the grid will be moved back into the grid. If <tt>(maxNum)</tt> is negative, particles that leave the grid will be deleted from the simulation. If <tt>|(maxNum)|</tt> 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 <tt>(maxNum)</tt> to 1 will cause a simulation to stop if any particle leaves the grid. | |||
== Notes == | == Notes == | ||
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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 moved into the [[Material Point Reservoir]]. | |||
<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. | ||
</ol> | |||
Latest revision as of 11:41, 22 July 2021
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 into the Material Point Reservoir.
- 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.