"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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fix lb/viscous command :h3

[Syntax:]

fix ID group-ID lb/viscous :pre
  
ID, group-ID are documented in "fix"_fix.html command
lb/viscous = style name of this fix command :ul

[Examples:]

fix 1 flow lb/viscous 

[Description:]

This fix is similar to the "fix viscous"_fix_viscous.html command, and
is to be used in place of that command when a lattice-Boltzmann fluid
is present, and the user wishes to integrate the particle motion using
one of the built in LAMMPS integrators.

This fix adds a force, F = - Gamma*(velocity-fluid_velocity), to each
atom, where Gamma is the force coupling constant described in the "fix
lb/fluid"_fix_lb_fluid.html command (which applies an equal and
opposite force to the fluid).

IMPORTANT NOTE: This fix should only be used in conjunction with one
of the built in LAMMPS integrators; it should not be used with the
"fix lb/pc"_fix_lb_pc.html or "fix
lb/rigid/pc/sphere"_fix_lb_rigid_pc_sphere.html integrators, which
already include the hydrodynamic forces.  These latter fixes should
only be used if the force coupling constant has been set by the user
(instead of using the default value); if the default force coupling
value is used, then this fix provides the only method for adding the
hydrodynamic forces to the particles.

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For further details, as well as descriptions and results of several
test runs, see "Mackay et al."_#Mackay.  Please include a citation to
this paper if this fix is used in work contributing to published
research.

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[Restart, fix_modify, output, run start/stop, minimize info:]

As described in the "fix viscous"_fix_viscous.html documentation:

"No information about this fix is written to "binary restart
files"_restart.html.  None of the "fix_modify"_fix_modify.html options
are relevant to this fix.  No global or per-atom quantities are stored
by this fix for access by various "output
commands"_Section_howto.html#howto_15.  No parameter of this fix can
be used with the {start/stop} keywords of the "run"_run.html command.

The forces due to this fix are imposed during an energy minimization,
invoked by the "minimize"_minimize.html command.  This fix should only
be used with damped dynamics minimizers that allow for
non-conservative forces.  See the "min_style"_min_style.html command
for details."

[Restrictions:]

This fix is part of the USER-LB package.  It is only enabled if LAMMPS
was built with that package.  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.

Can only be used if a lattice-Boltzmann fluid has been created via the
"fix lb/fluid"_fix_lb_fluid.html command, and must come after this
command.

This fix should not be used if either the "fix lb/pc"_fix_lb_pc.html
or "fix lb/rigid/pc/sphere"_fix_lb_rigid_pc_sphere.html integrator is
used.

[Related commands:]

"fix lb/fluid"_fix_lb_fluid.html, "fix lb/pc"_fix_lb_pc.html, "fix
lb/rigid/pc/sphere"_fix_lb_rigid_pc_sphere.html

[Default:] none

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:link(Mackay) 
[(Mackay et al.)] Mackay, F. E., Ollila, S.T.T., and Denniston, C., Hydrodynamic Forces Implemented into LAMMPS through a lattice-Boltzmann fluid, Computer Physics Communications 184 (2013) 2021-2031.
