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fix_lb_momentum.txt
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.. index:: fix lb/momentum
fix lb/momentum command
=======================
Syntax
""""""
.. parsed-literal::
fix ID group-ID lb/momentum nevery keyword values ...
* ID, group-ID are documented in the :doc:`fix <fix>` command
* lb/momentum = style name of this fix command
* nevery = adjust the momentum every this many timesteps
* zero or more keyword/value pairs may be appended
* keyword = *linear*
.. parsed-literal::
*linear* values = xflag yflag zflag
xflag,yflag,zflag = 0/1 to exclude/include each dimension.
Examples
""""""""
.. parsed-literal::
fix 1 sphere lb/momentum
fix 1 all lb/momentum linear 1 1 0
Description
"""""""""""
This fix is based on the :doc:`fix momentum <fix_momentum>` command, and
was created to be used in place of that command, when a
lattice-Boltzmann fluid is present.
Zero the total linear momentum of the system, including both the atoms
specified by group-ID and the lattice-Boltzmann fluid every nevery
timesteps. This is accomplished by adjusting the particle velocities
and the fluid velocities at each lattice site.
.. note::
This fix only considers the linear momentum of the system.
By default, the subtraction is performed for each dimension. This can
be changed by specifying the keyword *linear*\ , along with a set of
three flags set to 0/1 in order to exclude/ include the corresponding
dimension.
Restart, fix_modify, output, run start/stop, minimize info
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
No information about this fix is written to :doc:`binary restart files <restart>`. None of the :doc:`fix_modify <fix_modify>` options
are relevant to this fix. No global or per-atom quantities are stored
by this fix for access by various :ref:`output commands <4_15>`. No parameter of this fix can be
used with the *start/stop* keywords of the :doc:`run <run>` command.
This fix is not invoked during :doc:`energy minimization <minimize>`.
Restrictions
""""""""""""
Can only be used if a lattice-Boltzmann fluid has been created via the
:doc:`fix lb/fluid <fix_lb_fluid>` command, and must come after this
command.
This fix is part of the USER-LB package. It is only enabled if LAMMPS
was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info.
Related commands
""""""""""""""""
:doc:`fix momentum <fix_momentum>`, :doc:`fix lb/fluid <fix_lb_fluid>`
Default
"""""""
Zeros the total system linear momentum in each dimension.
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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