PeriodicXPIC Custom Task - Revision history

Nairnj: /* Introduction */

2026-04-12T19:13:17Z

Introduction

← Older revision		Revision as of 19:13, 12 April 2026
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	== Introduction ==		== Introduction ==

	The FMPM(k)<ref name="FMPM"/><ref name="FMPMrev"/> (or XPIC(k)<ref name="XPIC"/>) method is an [[FMPM Features\|advanced method]] makes use of an approximate inverse of the full mass matrix to filter out unwanted noise (in the null space) without damping out useful information. A drawback is that it adds calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using FMPM(k) (or XPIC(k)). The methods can be done every time step or only on periodic time steps. This custom tasks adds FMPM(k) (~~orm~~ XPIC(k)) to any simulation and lets you select the frequency of those calculations.		The FMPM(k)<ref name="FMPM"/><ref name="FMPMrev"/> (or XPIC(k)<ref name="XPIC"/>) method is an [[FMPM Features\|advanced method]] makes use of an approximate inverse of the full mass matrix to filter out unwanted noise (in the null space) without damping out useful information. A drawback is that it adds calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using FMPM(k) (or XPIC(k)). The methods can be done every time step or only on periodic time steps. This custom tasks adds FMPM(k) (or XPIC(k)) to any simulation and lets you select the frequency of those calculations.

	== Using FMPM(k) or XPIC(k) For Mechanics ==		== Using FMPM(k) or XPIC(k) For Mechanics ==

Nairnj at 19:12, 12 April 2026

2026-04-12T19:12:25Z

← Older revision		Revision as of 19:12, 12 April 2026
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	A [[MPM Input Files#Custom Tasks\|custom task]] to use [[~~XPIC~~ Features\|~~XPIC~~(k) ~~and FMPM~~(k) methods]] on all or selected time steps		A [[MPM Input Files#Custom Tasks\|custom task]] to use [[FMPM Features\|FMPM(k) (or XPIC(k)) methods]] on all or selected time steps
	__TOC__		__TOC__
	== Introduction ==		== Introduction ==

	The ~~XPIC~~(k)<ref name="~~XPIC~~"/> ~~and FMPM(k)~~<ref name="~~FMPM~~"/><ref name="~~FMPMrev~~"/> ~~methods are~~ [[~~XPIC~~ Features\|advanced ~~methods~~]] ~~that~~ filter out unwanted noise (in the null space) without damping out useful information. ~~Their~~ drawback is that ~~they add~~ calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using ~~XPIC~~(k) or ~~FMPM~~(k). The ~~XPIC(k) and FMPM(k)~~ methods can be done every time step or only on periodic time steps. This custom tasks adds ~~XPIC~~(k) ~~or FMPM~~(k) to any simulation and lets you select the frequency of those calculations.		The FMPM(k)<ref name="FMPM"/><ref name="FMPMrev"/> (or XPIC(k)<ref name="XPIC"/>) method is an [[FMPM Features\|advanced method]] makes use of an approximate inverse of the full mass matrix to filter out unwanted noise (in the null space) without damping out useful information. A drawback is that it adds calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using FMPM(k) (or XPIC(k)). The methods can be done every time step or only on periodic time steps. This custom tasks adds FMPM(k) (orm XPIC(k)) to any simulation and lets you select the frequency of those calculations.

	== Using FMPM(k) or XPIC(k) For Mechanics ==		== Using FMPM(k) or XPIC(k) For Mechanics ==

Nairnj: /* References */

2026-04-10T18:00:25Z

References

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	<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>		<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>

	<ref name="FMPMrev">J. A. Nairn, "Improved Implementation of Approximate Full Mass Matrix Inverse Methods into Material Point Method Simulations," <i>arXiv:2604.07307<i> (2026). ([https://arxiv.org/abs/2604.07307 See PDF])</ref>		<ref name="FMPMrev">J. A. Nairn, "Improved Implementation of Approximate Full Mass Matrix Inverse Methods into Material Point Method Simulations," <i>arXiv:2604.07307</i> (2026). ([https://arxiv.org/abs/2604.07307 See PDF])</ref>

	<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>		<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>

	</references>		</references>

Nairnj: /* Introduction */

2026-04-10T17:59:54Z

Introduction

← Older revision		Revision as of 17:59, 10 April 2026
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	== Introduction ==		== Introduction ==

	The XPIC(k)<ref name="XPIC"/> and FMPM(k)<ref name="FMPM"/> methods are [[XPIC Features\|advanced methods]] that filter out unwanted noise (in the null space) without damping out useful information. Their drawback is that they add calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using XPIC(k) or FMPM(k). The XPIC(k) and FMPM(k) methods can be done every time step or only on periodic time steps. This custom tasks adds XPIC(k) or FMPM(k) to any simulation and lets you select the frequency of those calculations.		The XPIC(k)<ref name="XPIC"/> and FMPM(k)<ref name="FMPM"/><ref name="FMPMrev"/> methods are [[XPIC Features\|advanced methods]] that filter out unwanted noise (in the null space) without damping out useful information. Their drawback is that they add calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using XPIC(k) or FMPM(k). The XPIC(k) and FMPM(k) methods can be done every time step or only on periodic time steps. This custom tasks adds XPIC(k) or FMPM(k) to any simulation and lets you select the frequency of those calculations.

	== Using FMPM(k) or XPIC(k) For Mechanics ==		== Using FMPM(k) or XPIC(k) For Mechanics ==

Nairnj: /* References */

2026-04-10T17:59:31Z

References

← Older revision		Revision as of 17:59, 10 April 2026
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	<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>		<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>

			<ref name="FMPMrev">J. A. Nairn, "Improved Implementation of Approximate Full Mass Matrix Inverse Methods into Material Point Method Simulations," <i>arXiv:2604.07307<i> (2026). ([https://arxiv.org/abs/2604.07307 See PDF])</ref>

	<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>		<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>

	</references>		</references>

Nairnj at 17:28, 29 March 2026

2026-03-29T17:28:13Z

← Older revision		Revision as of 17:28, 29 March 2026
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	The meanings of values <tt>(timeInterval)</tt> and <tt>(CFLfactor)</tt> are given in the [[#Using FMPM(k) or XPIC(k) For Mechanics\|previous section]] except that CFL factor is applied to [[MPM_Methods_and_Simulation_Timing#Theory:_MPM_Time_Step\|transport time step]] and not the simulation time step.		The meanings of values <tt>(timeInterval)</tt> and <tt>(CFLfactor)</tt> are given in the [[#Using FMPM(k) or XPIC(k) For Mechanics\|previous section]] except that CFL factor is applied to [[MPM_Methods_and_Simulation_Timing#Theory:_MPM_Time_Step\|transport time step]] and not the simulation time step.

	When using FMPM(k) for transport equations, you should never pick <tt>k=1</tt> because it causes too much numerical diffusion. Any higher order works, unless the FMPM(k) time steps are done too frequently. Because transport time step is usually much longer then mechanics time step, it is usually best to pick transport FMPM(k) frequency using the CFL parameter options and the chosen CFL factor should be 2 or higher for FMPM(2) and 0.5 or higher for FMPM(k>2) to avoid numerical diffusion.<ref name="~~transFMPM~~"/> Alternatively, one could pick blended method (with <tt>0<(stepInterval)<1</tt>) and use a small enough fraction of FMPM(k) to avoid numerical diffusion.		When using FMPM(k) for transport equations, you should never pick <tt>k=1</tt> because it causes too much numerical diffusion. Any higher order works, unless the FMPM(k) time steps are done too frequently. Because transport time step is usually much longer then mechanics time step, it is usually best to pick transport FMPM(k) frequency using the CFL parameter options and the chosen CFL factor should be 2 or higher for FMPM(2) and 0.5 or higher for FMPM(k>2) to avoid numerical diffusion.<ref name="transport"/> Alternatively, one could pick blended method (with <tt>0<(stepInterval)<1</tt>) and use a small enough fraction of FMPM(k) to avoid numerical diffusion.

	== References ==		== References ==

Nairnj: /* References */

2026-03-29T17:27:40Z

References

← Older revision		Revision as of 17:27, 29 March 2026
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	<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>		<ref name="FMPM">J. A. Nairn and C. C. Hammerquist, "Material point method simulations using an approximate full mass matrix inverse," <i>Computer Methods in Applied Mechanics and Engineering</i>, <b>377</b>, 113667 (2021). (2021). ([http://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/FMPMPaper.pdf See PDF])</ref>

	<ref name="~~transFMPM~~">J. A. Nairn, "Coupling ~~transport properties~~ to ~~mechanics~~ in the ~~material point method using~~ an ~~approximate full capacity matrix inverse~~," ~~<i>~~Computer Methods in Applied Mechanics and Engineering~~</i>~~, ~~submitted~~ (~~2023~~).</ref>		<ref name="transport">J. A. Nairn, "Coupling Transport Equations to Mechanics in the Material Point Method Using an Approximate Full Capacity Matrix Inverse," ''Computer Methods in Applied Mechanics and Engineering'', '''420''', 116757 (2024). ([https://www.cof.orst.edu/cof/wse/faculty/Nairn/papers/TransportPaper.pdf See PDF])</ref>

	</references>		</references>

Nairnj: /* Using FMPM(k) For Transport Properties */

2026-03-29T17:27:12Z

Using FMPM(k) For Transport Properties

← Older revision		Revision as of 17:27, 29 March 2026
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	== Using FMPM(k) For Transport Properties ==		== Using FMPM(k) For Transport Properties ==

	You can also use FMPM(k) for temperature (when doing [[Thermal Calculations\|conduction calculations]]), for concentration (when doing [[Diffusion Calculations\|diffusion calculations]]), for pore pressure (when doing [[Poroelasticity Calculations\|poroelasticity calculations]]) or for [[Additional Transport Calculations\|other transports calculations]]. FMPM(k) seems to provide significant improvement of transport modeling and can eliminate oscillations sometimes seen for transport value for particles within one cell. Note the transport modeling must use the same FMPM order as selected for mechanics. Furthermore, it will always uses FMPM(k) even if mechanics is using XPIC(k).		You can also use FMPM(k) for temperature (when doing [[Thermal Calculations\|conduction calculations]]), for concentration (when doing [[Diffusion Calculations\|diffusion calculations]]), for pore pressure (when doing [[Poroelasticity Calculations\|poroelasticity calculations]]) or for [[Additional Transport Calculations\|other transports calculations]].<ref name="transport"/> FMPM(k) seems to provide significant improvement of transport modeling and can eliminate oscillations sometimes seen for transport value for particles within one cell. Note the transport modeling must use the same FMPM order as selected for mechanics. Furthermore, it will always uses FMPM(k) even if mechanics is using XPIC(k).

	To use FMPM(k) for transport equations, select order [[#Using FMPM(k) or XPIC(k) For Mechanics\|previous section]] and then select periodicity of FMPM(k) for conduction and/or diffusion with following task parameters:		To use FMPM(k) for transport equations, select order [[#Using FMPM(k) or XPIC(k) For Mechanics\|previous section]] and then select periodicity of FMPM(k) for conduction and/or diffusion with following task parameters:

Nairnj at 18:26, 26 March 2026

2026-03-26T18:26:38Z

← Older revision		Revision as of 18:26, 26 March 2026
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	Parameter periodicCFL,(CFLfactor)		Parameter periodicCFL,(CFLfactor)
	Parameter verbose,{verbose}		Parameter verbose,{verbose}
	~~Parameter GridBCOption,(BCoption)~~

	In <tt>XML</tt> files, this task is scheduled using a <tt><Schedule></tt> element, which must be within the single <tt><CustomTasks></tt> block:		In <tt>XML</tt> files, this task is scheduled using a <tt><Schedule></tt> element, which must be within the single <tt><CustomTasks></tt> block:
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	<Parameter name='periodicCFL'>(CFLfactor)</Parameter>		<Parameter name='periodicCFL'>(CFLfactor)</Parameter>
	<Parameter name='verbose'>(verbose)</Parameter>		<Parameter name='verbose'>(verbose)</Parameter>
	~~<Parameter name='GridBCOption'>(BCoption)</Parameter>~~
	</Schedule>		</Schedule>

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	* <tt>(stepInterval)</tt>, <tt>(timeInterval)</tt>, and <tt>(CFLfactor)</tt> - sets the frequency for running periodic FMPM(k) or XPIC(k) time steps for mechanics. The <tt>(stepInterval)</tt> option sets number of time steps between each FMPM(k) or XPIC(k) time step, <tt>(timeInterval)</tt> sets frequency in [[ConsistentUnits Command#Legacy and Consistent Units\|alt time units]], and <tt>(CFLfactor)</tt> sets frequency relative to the basic time step for the momentum equation. If <tt>(stepInterval)</tt> is provided, it is used and the other two are ignored. If <tt>(stepInterval)</tt> is not provided, the time step is found from the <tt>(CFLfactor)</tt> (if provided) or from <tt>(timeInterval)</tt>. One of these three parameters is required to enable periodic FMPM(k) or XPIC(k) calculations.		* <tt>(stepInterval)</tt>, <tt>(timeInterval)</tt>, and <tt>(CFLfactor)</tt> - sets the frequency for running periodic FMPM(k) or XPIC(k) time steps for mechanics. The <tt>(stepInterval)</tt> option sets number of time steps between each FMPM(k) or XPIC(k) time step, <tt>(timeInterval)</tt> sets frequency in [[ConsistentUnits Command#Legacy and Consistent Units\|alt time units]], and <tt>(CFLfactor)</tt> sets frequency relative to the basic time step for the momentum equation. If <tt>(stepInterval)</tt> is provided, it is used and the other two are ignored. If <tt>(stepInterval)</tt> is not provided, the time step is found from the <tt>(CFLfactor)</tt> (if provided) or from <tt>(timeInterval)</tt>. One of these three parameters is required to enable periodic FMPM(k) or XPIC(k) calculations.
	* <tt>(verbose)</tt> - If a non-zero integer, a comment line is printed in the output file every time FMPM(k) or XPIC(k) time steps are done. The default is 0.		* <tt>(verbose)</tt> - If a non-zero integer, a comment line is printed in the output file every time FMPM(k) or XPIC(k) time steps are done. The default is 0.
	* <tt>(BCOption)</tt> - Use "lumped" to use lumped mass matrix methods for boundary conditions, "velocity" to only impose grid velocity conditions in the velocity field, or "combined" to do both. The default is "combined" for FMPM(k) and lumped for XPIC(k). Note that XPIC(k) cannot use "velocity" option (that setting will be changed to "lumped" if used). This option only affects calculations when <tt>(order)</tt> is greater than 1. The defaults are usually the best choice. Details on these options are in Ref. <ref name="FMPM"/>.

	== Using FMPM(k) For Transport Properties ==		== Using FMPM(k) For Transport Properties ==

Nairnj: /* Introduction */

2025-01-08T02:09:45Z

Introduction

← Older revision		Revision as of 02:09, 8 January 2025
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	== Introduction ==		== Introduction ==

	The ~~[[XPIC Features\|~~XPIC(k)<ref name="XPIC"/> and FMPM(k)<ref name="FMPM"/> methods]] are advanced methods that filter out unwanted noise (in the null space) without damping out useful information. Their drawback is that they add calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using XPIC(k) or FMPM(k). The XPIC(k) and FMPM(k) methods can be done every time step or only on periodic time steps. This custom tasks adds XPIC(k) or FMPM(k) to any simulation and lets you select the frequency of those calculations.		The XPIC(k)<ref name="XPIC"/> and FMPM(k)<ref name="FMPM"/> methods are [[XPIC Features\|advanced methods]] that filter out unwanted noise (in the null space) without damping out useful information. Their drawback is that they add calculation time as order <tt>k</tt> increases. Many simulations (especially those with stability issues) will run better by using XPIC(k) or FMPM(k). The XPIC(k) and FMPM(k) methods can be done every time step or only on periodic time steps. This custom tasks adds XPIC(k) or FMPM(k) to any simulation and lets you select the frequency of those calculations.

	== Using FMPM(k) or XPIC(k) For Mechanics ==		== Using FMPM(k) or XPIC(k) For Mechanics ==