forked from lijiext/lammps
95 lines
3.8 KiB
HTML
95 lines
3.8 KiB
HTML
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<HTML>
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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</CENTER>
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<HR>
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<H3>fix lb/viscous command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID lb/viscous
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<PRE>lb/viscous = style name of this fix command
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<P>fix 1 flow lb/viscous
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</P>
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<P><B>Description:</B>
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</P>
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<P>This fix is similar to the <A HREF = "fix_viscous.html">fix viscous</A> command, and
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is to be used in place of that command when a lattice-Boltzmann fluid
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is present, and the user wishes to integrate the particle motion using
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one of the built in LAMMPS integrators.
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</P>
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<P>This fix adds a force, F = - Gamma*(velocity-fluid_velocity), to each
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atom, where Gamma is the force coupling constant described in the
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<A HREF = "fix_lb_fluid.html">fix lb/fluid</A> command (which applies an equal and opposite
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force to the fluid).
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</P>
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<P>IMPORTANT NOTE: This fix should only be used in conjunction with one of the
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built in LAMMPS integrators; it should not be used with the
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<A HREF = "fix_lb_pc.html">fix lb/pc</A> or <A HREF = "fix_lb_rigid_pc_sphere.html">fix lb/rigid/pc/sphere</A> integrators,
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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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</P>
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<HR>
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<P>For further details, as well as descriptions and results of several test runs,
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see <A HREF = "#Mackay">Mackay et al.</A> [1] . Please include a citation to this
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paper if this fix is used in work contributing to published research.
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</P>
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<HR>
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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</P>
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<P>As described in the <A HREF = "fix_viscous.html">fix viscous</A> documentation:
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</P>
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<P>"No information about this fix is written to <A HREF = "restart.html">binary restart
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files</A>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
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are relevant to this fix. No global or per-atom quantities are stored
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by this fix for access by various <A HREF = "Section_howto.html#howto_15">output
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commands</A>. No parameter of this fix can
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be used with the <I>start/stop</I> keywords of the <A HREF = "run.html">run</A> command.
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</P>
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<P>The forces due to this fix are imposed during an energy minimization,
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invoked by the <A HREF = "minimize.html">minimize</A> command. This fix should only
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be used with damped dynamics minimizers that allow for
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non-conservative forces. See the <A HREF = "min_style.html">min_style</A> command
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for details."
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>Can only be used if a lattice-Boltzmann fluid has been created via the
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<A HREF = "fix_lb_fluid.html">fix lb/fluid</A> command, and must come after this command.
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</P>
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<P>This fix should not be used if either the <A HREF = "fix_lb_pc.html">fix lb/pc</A> or
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<A HREF = "fix_lb_rigid_pc_sphere.html">fix lb/rigid/pc/sphere</A> integrator is used.
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</P>
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<P> This fix can only be used if LAMMPS was built with the
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"fluid" package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info on packages.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "fix_lb_fluid.html">fix lb/fluid</A>, <A HREF = "fix_lb_pc.html">fix lb/pc</A>, <A HREF = "fix_lb_rigid_pc_sphere.html">fix lb/rigid/pc/sphere</A>
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</P>
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<P><B>Default:</B> none
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</P>
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<HR>
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<A NAME = "Mackay"></A>
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<P><B>[1] (Mackay et al.)</B> 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.
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</P>
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</HTML>
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