forked from lijiext/lammps
69 lines
1.8 KiB
Plaintext
69 lines
1.8 KiB
Plaintext
.. index:: fix smd/adjust_dt
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fix smd/adjust_dt command
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=========================
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Syntax
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""""""
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.. parsed-literal::
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fix ID group-ID smd/adjust_dt arg
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* smd/adjust_dt = style name of this fix command
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* arg = *s_fact*
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.. parsed-literal::
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*s_fact* = safety factor
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Examples
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""""""""
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.. parsed-literal::
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fix 1 all smd/adjust_dt 0.1
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Description
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"""""""""""
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The fix calculates a new stable time increment for use with the SMD time integrators.
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The stable time increment is based on multiple conditions. For the SPH pair styles, a
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CFL criterion (Courant, Friedrichs & Lewy, 1928) is evaluated, which determines the the speed of
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sound cannot propagate further than a typical spacing between particles within a single time step to ensure
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no information is lost. For the contact pair styles, a linear analysis of the pair potential determines a
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stable maximum time step.
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This fix inquires the minimum stable time increment across all particles contained in the group for which this
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fix is defined. An additional safety factor *s_fact* is applied to the time increment.
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See `this PDF guide <USER/smd/SMD_LAMMPS_userguide.pdf>`_ to use Smooth Mach Dynamics in LAMMPS.
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Restart, fix_modify, output, run start/stop, minimize info
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""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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Currently, no part of USER-SMD supports restarting nor minimization.
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Restrictions
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""""""""""""
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This fix is part of the USER-SMD package. It is only enabled if
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LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>`
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section for more info.
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Related commands
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""""""""""""""""
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:doc:`smd/tlsph_dt <compute_smd_tlsph_dt>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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