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fix_lb_momentum.html
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Mon, Nov 4, 17:45
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rLAMMPS lammps
fix_lb_momentum.html
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<HTML>
<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>
</CENTER>
<HR>
<H3>
fix lb/momentum command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
fix ID group-ID lb/momentum nevery keyword values ...
</PRE>
<UL><LI>
ID, group-ID are documented in the
<A
HREF =
"fix.html"
>
fix
</A>
command
<LI>
lb/momentum = style name of this fix command
<LI>
nevery = adjust the momentum every this many timesteps
<LI>
zero or more keyword/value pairs may be appended
<LI>
keyword =
<I>
linear
</I>
<PRE>
<I>
linear
</I>
values = xflag yflag zflag
xflag,yflag,zflag = 0/1 to exclude/include each dimension.
</PRE>
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
fix 1 sphere lb/momentum
fix 1 all lb/momentum linear 1 1 0
</PRE>
<P><B>
Description:
</B>
</P>
<P>
This fix is based on the
<A
HREF =
"fix_momentum.html"
>
fix momentum
</A>
command, and
was created to be used in place of that command, when a
lattice-Boltzmann fluid is present.
</P>
<P>
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.
</P>
<P>
NOTE: This fix only considers the linear momentum of the system.
</P>
<P>
By default, the subtraction is performed for each dimension. This can
be changed by specifying the keyword
<I>
linear
</I>
, along with a set of
three flags set to 0/1 in order to exclude/ include the corresponding
dimension.
</P>
<P><B>
Restart, fix_modify, output, run start/stop, minimize info:
</B>
</P>
<P>
No information about this fix is written to
<A
HREF =
"restart.html"
>
binary restart
files
</A>
. None of the
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
options
are relevant to this fix. No global or per-atom quantities are stored
by this fix for access by various
<A
HREF =
"Section_howto.html#4_15"
>
output
commands
</A>
. No parameter of this fix can be
used with the
<I>
start/stop
</I>
keywords of the
<A
HREF =
"run.html"
>
run
</A>
command.
This fix is not invoked during
<A
HREF =
"minimize.html"
>
energy minimization
</A>
.
</P>
<P><B>
Restrictions:
</B>
</P>
<P>
Can only be used if a lattice-Boltzmann fluid has been created via the
<A
HREF =
"fix_lb_fluid.html"
>
fix lb/fluid
</A>
command, and must come after this
command.
</P>
<P>
This fix is part of the USER-LB package. It is only enabled if LAMMPS
was built with that package. See the
<A
HREF =
"Section_start.html#start_3"
>
Making
LAMMPS
</A>
section for more info.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"fix_momentum.html"
>
fix momentum
</A>
,
<A
HREF =
"fix_lb_fluid.html"
>
fix lb/fluid
</A>
</P>
<P><B>
Default:
</B>
</P>
<P>
Zeros the total system linear momentum in each dimension.
</P>
</HTML>
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