mirror of https://github.com/lammps/lammps.git
git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@7206 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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sjplimp
parent
ac30ed30e3
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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>
|
||||
</CENTER>
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
<HR>
|
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|
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<H3>pair_style brownian command
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</H3>
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<H3>pair_style brownian/poly command
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</H3>
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<P><B>Syntax:</B>
|
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</P>
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||||
<PRE>pair_style style mu flaglog flagfld cutinner cutoff t_target seed
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</PRE>
|
||||
<UL><LI>style = <I>brownian</I> or <I>brownian/poly</I>
|
||||
<LI>mu = dynamic viscosity (dynamic viscosity units)
|
||||
<LI>flaglog = 0/1 log terms in the lubrication approximation on/off
|
||||
<LI>flagfld = 0/1 to include/exclude Fast Lubrication Dynamics effects
|
||||
<LI>cutinner = inner cutoff distance (distance units)
|
||||
<LI>cutoff = outer cutoff for interactions (distance units)
|
||||
<LI>t_target = target temp of the system (temperature units)
|
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<LI>seed = seed for the random number generator (positive integer)
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>pair_style brownian 1.5 1 1 2.01 2.5 2.0 5878567 (assuming radius=1)
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pair_coeff 1 1 2.05 2.8
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pair_coeff * *
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</PRE>
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<P><B>Description:</B>
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</P>
|
||||
<P>Styles <I>brownian</I> and <I>brownain/poly</I> compute Brownian forces and
|
||||
torques on finite-size particles. The former requires monodisperse
|
||||
spherical particles; the latter allows for polydisperse spherical
|
||||
particles.
|
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</P>
|
||||
<P>These pair styles are designed to be used with either the <A HREF = "pair_lubricate.html">pair_style
|
||||
lubricate</A> or <A HREF = "pair_lubricateU.html">pair_style
|
||||
lubricateU</A> commands to provide thermostatting
|
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when dissipative lubrication forces are acting. Thus the parameters
|
||||
<I>mu</I>, <I>flaglog</I>, <I>flagfld</I>, <I>cutinner</I>, and <I>cutoff</I> should be
|
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specified consistent with the settings in the lubrication pair styles.
|
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For details, refer to either of the lubrication pair styles.
|
||||
</P>
|
||||
<P>The <I>t_target</I> setting is used to specify the target temperature of
|
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the system. The random number <I>seed</I> is used to generate random
|
||||
numbers for the thermostatting procedure.
|
||||
</P>
|
||||
<P>The following coefficients must be defined for each pair of atoms
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types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
|
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above, or in the data file or restart files read by the
|
||||
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
|
||||
commands, or by mixing as described below:
|
||||
</P>
|
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<UL><LI>cutinner (distance units)
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<LI>cutoff (distance units)
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</UL>
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<P>The two coefficients are optional. If neither is specified, the two
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cutoffs specified in the pair_style command are used. Otherwise both
|
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must be specified.
|
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</P>
|
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<HR>
|
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|
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<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
|
||||
</P>
|
||||
<P>For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is <I>geometric</I>. See
|
||||
the "pair_modify" command for details.
|
||||
</P>
|
||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
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shift option for the energy of the pair interaction.
|
||||
</P>
|
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<P>The <A HREF = "pair_modify.html">pair_modify</A> table option is not relevant
|
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for this pair style.
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</P>
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||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
||||
tail option for adding long-range tail corrections to energy and
|
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pressure.
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||||
</P>
|
||||
<P>This pair style writes its information to <A HREF = "restart.html">binary restart
|
||||
files</A>, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
</P>
|
||||
<P>This pair style can only be used via the <I>pair</I> keyword of the
|
||||
<A HREF = "run_style.html">run_style respa</A> command. It does not support the
|
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<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P><B>Restrictions:</B>
|
||||
</P>
|
||||
<P>These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
|
||||
LAMMPS</A> section for more info.
|
||||
</P>
|
||||
<P>Only spherical monodisperse particles are allowed for pair_style
|
||||
brownian.
|
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</P>
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<P>Only spherical particles are allowed for pair_style brownian/poly.
|
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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 = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_lubricate.html">pair_style
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lubricate</A>, <A HREF = "pair_lubricateU.html">pair_style
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lubricateU</A>
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</P>
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<P><B>Default:</B> none
|
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</P>
|
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</HTML>
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|
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@ -0,0 +1,108 @@
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style brownian command :h3
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pair_style brownian/poly command :h3
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[Syntax:]
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pair_style style mu flaglog flagfld cutinner cutoff t_target seed :pre
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style = {brownian} or {brownian/poly}
|
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mu = dynamic viscosity (dynamic viscosity units)
|
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flaglog = 0/1 log terms in the lubrication approximation on/off
|
||||
flagfld = 0/1 to include/exclude Fast Lubrication Dynamics effects
|
||||
cutinner = inner cutoff distance (distance units)
|
||||
cutoff = outer cutoff for interactions (distance units)
|
||||
t_target = target temp of the system (temperature units)
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seed = seed for the random number generator (positive integer) :ul
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||||
|
||||
[Examples:]
|
||||
|
||||
pair_style brownian 1.5 1 1 2.01 2.5 2.0 5878567 (assuming radius=1)
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pair_coeff 1 1 2.05 2.8
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pair_coeff * * :pre
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||||
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[Description:]
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|
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Styles {brownian} and {brownain/poly} compute Brownian forces and
|
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torques on finite-size particles. The former requires monodisperse
|
||||
spherical particles; the latter allows for polydisperse spherical
|
||||
particles.
|
||||
|
||||
These pair styles are designed to be used with either the "pair_style
|
||||
lubricate"_pair_lubricate.html or "pair_style
|
||||
lubricateU"_pair_lubricateU.html commands to provide thermostatting
|
||||
when dissipative lubrication forces are acting. Thus the parameters
|
||||
{mu}, {flaglog}, {flagfld}, {cutinner}, and {cutoff} should be
|
||||
specified consistent with the settings in the lubrication pair styles.
|
||||
For details, refer to either of the lubrication pair styles.
|
||||
|
||||
The {t_target} setting is used to specify the target temperature of
|
||||
the system. The random number {seed} is used to generate random
|
||||
numbers for the thermostatting procedure.
|
||||
|
||||
The following coefficients must be defined for each pair of atoms
|
||||
types via the "pair_coeff"_pair_coeff.html command as in the examples
|
||||
above, or in the data file or restart files read by the
|
||||
"read_data"_read_data.html or "read_restart"_read_restart.html
|
||||
commands, or by mixing as described below:
|
||||
|
||||
cutinner (distance units)
|
||||
cutoff (distance units) :ul
|
||||
|
||||
The two coefficients are optional. If neither is specified, the two
|
||||
cutoffs specified in the pair_style command are used. Otherwise both
|
||||
must be specified.
|
||||
|
||||
:line
|
||||
|
||||
[Mixing, shift, table, tail correction, restart, rRESPA info]:
|
||||
|
||||
For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is {geometric}. See
|
||||
the "pair_modify" command for details.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
shift option for the energy of the pair interaction.
|
||||
|
||||
The "pair_modify"_pair_modify.html table option is not relevant
|
||||
for this pair style.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
tail option for adding long-range tail corrections to energy and
|
||||
pressure.
|
||||
|
||||
This pair style writes its information to "binary restart
|
||||
files"_restart.html, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
|
||||
This pair style can only be used via the {pair} keyword of the
|
||||
"run_style respa"_run_style.html command. It does not support the
|
||||
{inner}, {middle}, {outer} keywords.
|
||||
|
||||
:line
|
||||
|
||||
[Restrictions:]
|
||||
|
||||
These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the "Making
|
||||
LAMMPS"_Section_start.html#2_3 section for more info.
|
||||
|
||||
Only spherical monodisperse particles are allowed for pair_style
|
||||
brownian.
|
||||
|
||||
Only spherical particles are allowed for pair_style brownian/poly.
|
||||
|
||||
[Related commands:]
|
||||
|
||||
"pair_coeff"_pair_coeff.html, "pair_style
|
||||
lubricate"_pair_lubricate.html, "pair_style
|
||||
lubricateU"_pair_lubricateU.html
|
||||
|
||||
[Default:] none
|
||||
|
|
@ -0,0 +1,178 @@
|
|||
<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>pair_style lubricate command
|
||||
</H3>
|
||||
<H3>pair_style lubricate/poly command
|
||||
</H3>
|
||||
<P><B>Syntax:</B>
|
||||
</P>
|
||||
<PRE>pair_style style mu flaglog flagfld cutinner cutoff
|
||||
</PRE>
|
||||
<UL><LI>style = <I>lubricate</I> or <I>lubricate/poly</I>
|
||||
<LI>mu = dynamic viscosity (dynamic viscosity units)
|
||||
<LI>flaglog = 0/1 log terms in the lubrication approximation off/on
|
||||
<LI>flagfld = 0/1 to include/exclude Fast Lubrication Dynamics effects
|
||||
<LI>cutinner = inner cutoff distance (distance units)
|
||||
<LI>cutoff = outer cutoff for interactions (distance units)
|
||||
</UL>
|
||||
<P><B>Examples:</B> (all assume radius = 1)
|
||||
</P>
|
||||
<PRE>pair_style lubricate 1.5 1 1 2.01 2.5
|
||||
pair_coeff 1 1 2.05 2.8
|
||||
pair_coeff * *
|
||||
</PRE>
|
||||
<PRE>pair_style lubricate 1.5 1 1 2.01 2.5
|
||||
pair_coeff * *
|
||||
variable mu equal ramp(1,2)
|
||||
fix 1 all adapt 1 pair lubricate mu * * v_mu
|
||||
</PRE>
|
||||
<P><B>Description:</B>
|
||||
</P>
|
||||
<P>Styles <I>lubricate</I> and <I>lubricate/poly</I> compute hydrodynamic
|
||||
interactions between mono-disperse spherical particles in a pairwise
|
||||
fashion. The interactions have 2 components. The first is
|
||||
Ball-Melrose lubrication terms via the formulas in <A HREF = "#Ball">(Ball and
|
||||
Melrose)</A>
|
||||
</P>
|
||||
<CENTER><IMG SRC = "Eqs/pair_lubricate.jpg">
|
||||
</CENTER>
|
||||
<P>which represents the dissipation W between two nearby particles due to
|
||||
their relative velocities in the presence of a background solvent with
|
||||
viscosity mu. Note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
</P>
|
||||
<P>The Asq (squeeze) term is the strongest and is always included. It
|
||||
scales as 1/gap where gap is the separation between the surfaces of
|
||||
the 2 particles. The Ash (shear) and Apu (pump) terms are only
|
||||
include if <I>flaglog</I> is set to 1. Thy are the next strongest
|
||||
interactions, and the only other singular interaction, and scale as
|
||||
log(gap). The Atw (twist) term is currently not included. It is
|
||||
typically a very small contribution to the lubrication forces.
|
||||
</P>
|
||||
<P><I>Cutinner</I> sets the minimum center-to-center separation that will be
|
||||
used in calculations irrespective of the actual separation. <I>Cutoff</I>
|
||||
is the maximum center-to-center separation at which an interaction is
|
||||
computed. Using a <I>cutoff</I> less than 3 radii is recommended if
|
||||
<I>flaglog</I> is set to 1.
|
||||
</P>
|
||||
<P>The other component is due to the Fast Lubrication Dynamics (FLD)
|
||||
approximation, described in <A HREF = "#Higdon">(Higdon)</A>, which can be
|
||||
represented by the following equation
|
||||
</P>
|
||||
<CENTER><IMG SRC = "Eqs/fld.jpg">
|
||||
</CENTER>
|
||||
<P>where U represents the velocities and angular velocities of the
|
||||
particles, U^<I>infty</I> represents the velocity and the angular velocity
|
||||
of the undisturbed fluid, and E^<I>infty</I> represents the rate of strain
|
||||
tensor of the undisturbed fluid with viscosity mu. Again, note that
|
||||
this is dynamic viscosity which has units of mass/distance/time, not
|
||||
kinematic viscosity.
|
||||
</P>
|
||||
<P>IMPORTANT NOTE: When using the FLD terms, these pair styles are
|
||||
designed to be used with explicit time integration and a
|
||||
correspondingly small timestep. Thus either <A HREF = "fix_nve_sphere.html">fix
|
||||
nve/sphere</A> or <A HREF = "fix_nve_asphere.html">fix
|
||||
nve/asphere</A> should be used for time integration.
|
||||
To perform implicit FLD, see the <A HREF = "pair_lubricateU.html">pair_style
|
||||
lubricateU</A> command.
|
||||
</P>
|
||||
<P>Style <I>lubricate</I> requires monodisperse spherical particles; style
|
||||
<I>lubricate/poly</I> allows for polydisperse spherical particles.
|
||||
</P>
|
||||
<P>The viscosity mu can be varied in a time-dependent manner over the
|
||||
course of a simluation, in which case in which case the pair_style
|
||||
setting for mu will be overridden. See the <A HREF = "fix_adapt.html">fix adapt</A>
|
||||
command for details.
|
||||
</P>
|
||||
<P>If the suspension is sheared via the <A HREF = "fix_deform.html">fix deform</A>
|
||||
command then the pair style uses the shear rate to adjust the
|
||||
hydrodynamic interactions accordingly.
|
||||
</P>
|
||||
<P>Since lubrication forces are dissipative, it is usually desirable to
|
||||
thermostat the system at a constant temperature. If Brownian motion
|
||||
(at a constant temperature) is desired, it can be set using the
|
||||
<A HREF = "pair_brownian.html">pair_style brownian</A> command. These pair styles
|
||||
and the <I>brownian</I> style should use consistent parameters for <I>mu</I>,
|
||||
<I>flaglog</I>, <I>flagfld</I>, <I>cutinner</I>, and <I>cutoff</I>.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P>The following coefficients must be defined for each pair of atoms
|
||||
types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
|
||||
above, or in the data file or restart files read by the
|
||||
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
|
||||
commands, or by mixing as described below:
|
||||
</P>
|
||||
<UL><LI>cutinner (distance units)
|
||||
<LI>cutoff (distance units)
|
||||
</UL>
|
||||
<P>The two coefficients are optional. If neither is specified, the two
|
||||
cutoffs specified in the pair_style command are used. Otherwise both
|
||||
must be specified.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
|
||||
</P>
|
||||
<P>For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is <I>geometric</I>. See
|
||||
the "pair_modify" command for details.
|
||||
</P>
|
||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
||||
shift option for the energy of the pair interaction.
|
||||
</P>
|
||||
<P>The <A HREF = "pair_modify.html">pair_modify</A> table option is not relevant
|
||||
for this pair style.
|
||||
</P>
|
||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
||||
tail option for adding long-range tail corrections to energy and
|
||||
pressure.
|
||||
</P>
|
||||
<P>This pair style writes its information to <A HREF = "restart.html">binary restart
|
||||
files</A>, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
</P>
|
||||
<P>This pair style can only be used via the <I>pair</I> keyword of the
|
||||
<A HREF = "run_style.html">run_style respa</A> command. It does not support the
|
||||
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P><B>Restrictions:</B>
|
||||
</P>
|
||||
<P>These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
|
||||
LAMMPS</A> section for more info.
|
||||
</P>
|
||||
<P>Only spherical monodisperse particles are allowed for pair_style
|
||||
lubricate.
|
||||
</P>
|
||||
<P>Only spherical particles are allowed for pair_style lubricate/poly.
|
||||
</P>
|
||||
<P><B>Related commands:</B>
|
||||
</P>
|
||||
<P><A HREF = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_lubricateU.html">pair_style
|
||||
lubricateU</A>
|
||||
</P>
|
||||
<P><B>Default:</B> none
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<A NAME = "Ball"></A>
|
||||
|
||||
<P><B>(Ball)</B> Ball and Melrose, Physica A, 247, 444-472 (1997).
|
||||
</P>
|
||||
<A NAME = "Higdon"></A>
|
||||
|
||||
<P><B>(Higdon)</B> Amit and Higdon, Phys Rev E (2010).
|
||||
</P>
|
||||
</HTML>
|
||||
|
|
@ -0,0 +1,170 @@
|
|||
"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)
|
||||
|
||||
:line
|
||||
|
||||
pair_style lubricate command :h3
|
||||
pair_style lubricate/poly command :h3
|
||||
|
||||
[Syntax:]
|
||||
|
||||
pair_style style mu flaglog flagfld cutinner cutoff :pre
|
||||
|
||||
style = {lubricate} or {lubricate/poly}
|
||||
mu = dynamic viscosity (dynamic viscosity units)
|
||||
flaglog = 0/1 log terms in the lubrication approximation off/on
|
||||
flagfld = 0/1 to include/exclude Fast Lubrication Dynamics effects
|
||||
cutinner = inner cutoff distance (distance units)
|
||||
cutoff = outer cutoff for interactions (distance units) :ul
|
||||
|
||||
[Examples:] (all assume radius = 1)
|
||||
|
||||
pair_style lubricate 1.5 1 1 2.01 2.5
|
||||
pair_coeff 1 1 2.05 2.8
|
||||
pair_coeff * * :pre
|
||||
|
||||
pair_style lubricate 1.5 1 1 2.01 2.5
|
||||
pair_coeff * *
|
||||
variable mu equal ramp(1,2)
|
||||
fix 1 all adapt 1 pair lubricate mu * * v_mu :pre
|
||||
|
||||
[Description:]
|
||||
|
||||
Styles {lubricate} and {lubricate/poly} compute hydrodynamic
|
||||
interactions between mono-disperse spherical particles in a pairwise
|
||||
fashion. The interactions have 2 components. The first is
|
||||
Ball-Melrose lubrication terms via the formulas in "(Ball and
|
||||
Melrose)"_#Ball
|
||||
|
||||
:c,image(Eqs/pair_lubricate.jpg)
|
||||
|
||||
which represents the dissipation W between two nearby particles due to
|
||||
their relative velocities in the presence of a background solvent with
|
||||
viscosity mu. Note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
|
||||
The Asq (squeeze) term is the strongest and is always included. It
|
||||
scales as 1/gap where gap is the separation between the surfaces of
|
||||
the 2 particles. The Ash (shear) and Apu (pump) terms are only
|
||||
include if {flaglog} is set to 1. Thy are the next strongest
|
||||
interactions, and the only other singular interaction, and scale as
|
||||
log(gap). The Atw (twist) term is currently not included. It is
|
||||
typically a very small contribution to the lubrication forces.
|
||||
|
||||
{Cutinner} sets the minimum center-to-center separation that will be
|
||||
used in calculations irrespective of the actual separation. {Cutoff}
|
||||
is the maximum center-to-center separation at which an interaction is
|
||||
computed. Using a {cutoff} less than 3 radii is recommended if
|
||||
{flaglog} is set to 1.
|
||||
|
||||
The other component is due to the Fast Lubrication Dynamics (FLD)
|
||||
approximation, described in "(Higdon)"_#Higdon, which can be
|
||||
represented by the following equation
|
||||
|
||||
:c,image(Eqs/fld.jpg)
|
||||
|
||||
where U represents the velocities and angular velocities of the
|
||||
particles, U^{infty} represents the velocity and the angular velocity
|
||||
of the undisturbed fluid, and E^{infty} represents the rate of strain
|
||||
tensor of the undisturbed fluid with viscosity mu. Again, note that
|
||||
this is dynamic viscosity which has units of mass/distance/time, not
|
||||
kinematic viscosity.
|
||||
|
||||
IMPORTANT NOTE: When using the FLD terms, these pair styles are
|
||||
designed to be used with explicit time integration and a
|
||||
correspondingly small timestep. Thus either "fix
|
||||
nve/sphere"_fix_nve_sphere.html or "fix
|
||||
nve/asphere"_fix_nve_asphere.html should be used for time integration.
|
||||
To perform implicit FLD, see the "pair_style
|
||||
lubricateU"_pair_lubricateU.html command.
|
||||
|
||||
Style {lubricate} requires monodisperse spherical particles; style
|
||||
{lubricate/poly} allows for polydisperse spherical particles.
|
||||
|
||||
The viscosity mu can be varied in a time-dependent manner over the
|
||||
course of a simluation, in which case in which case the pair_style
|
||||
setting for mu will be overridden. See the "fix adapt"_fix_adapt.html
|
||||
command for details.
|
||||
|
||||
If the suspension is sheared via the "fix deform"_fix_deform.html
|
||||
command then the pair style uses the shear rate to adjust the
|
||||
hydrodynamic interactions accordingly.
|
||||
|
||||
Since lubrication forces are dissipative, it is usually desirable to
|
||||
thermostat the system at a constant temperature. If Brownian motion
|
||||
(at a constant temperature) is desired, it can be set using the
|
||||
"pair_style brownian"_pair_brownian.html command. These pair styles
|
||||
and the {brownian} style should use consistent parameters for {mu},
|
||||
{flaglog}, {flagfld}, {cutinner}, and {cutoff}.
|
||||
|
||||
:line
|
||||
|
||||
The following coefficients must be defined for each pair of atoms
|
||||
types via the "pair_coeff"_pair_coeff.html command as in the examples
|
||||
above, or in the data file or restart files read by the
|
||||
"read_data"_read_data.html or "read_restart"_read_restart.html
|
||||
commands, or by mixing as described below:
|
||||
|
||||
cutinner (distance units)
|
||||
cutoff (distance units) :ul
|
||||
|
||||
The two coefficients are optional. If neither is specified, the two
|
||||
cutoffs specified in the pair_style command are used. Otherwise both
|
||||
must be specified.
|
||||
|
||||
:line
|
||||
|
||||
[Mixing, shift, table, tail correction, restart, rRESPA info]:
|
||||
|
||||
For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is {geometric}. See
|
||||
the "pair_modify" command for details.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
shift option for the energy of the pair interaction.
|
||||
|
||||
The "pair_modify"_pair_modify.html table option is not relevant
|
||||
for this pair style.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
tail option for adding long-range tail corrections to energy and
|
||||
pressure.
|
||||
|
||||
This pair style writes its information to "binary restart
|
||||
files"_restart.html, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
|
||||
This pair style can only be used via the {pair} keyword of the
|
||||
"run_style respa"_run_style.html command. It does not support the
|
||||
{inner}, {middle}, {outer} keywords.
|
||||
|
||||
:line
|
||||
|
||||
[Restrictions:]
|
||||
|
||||
These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the "Making
|
||||
LAMMPS"_Section_start.html#2_3 section for more info.
|
||||
|
||||
Only spherical monodisperse particles are allowed for pair_style
|
||||
lubricate.
|
||||
|
||||
Only spherical particles are allowed for pair_style lubricate/poly.
|
||||
|
||||
[Related commands:]
|
||||
|
||||
"pair_coeff"_pair_coeff.html, "pair_style
|
||||
lubricateU"_pair_lubricateU.html
|
||||
|
||||
[Default:] none
|
||||
|
||||
:line
|
||||
|
||||
:link(Ball)
|
||||
[(Ball)] Ball and Melrose, Physica A, 247, 444-472 (1997).
|
||||
|
||||
:link(Higdon)
|
||||
[(Higdon)] Amit and Higdon, Phys Rev E (2010).
|
||||
|
|
@ -0,0 +1,199 @@
|
|||
<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>pair_style lubricateU command
|
||||
</H3>
|
||||
<H3>pair_style lubricateU/poly command
|
||||
</H3>
|
||||
<P><B>Syntax:</B>
|
||||
</P>
|
||||
<PRE>pair_style style mu flaglog cutinner cutoff gdot
|
||||
</PRE>
|
||||
<UL><LI>style = <I>lubricateU</I> or <I>lubricateU/poly</I>
|
||||
<LI>mu = dynamic viscosity (dynamic viscosity units)
|
||||
<LI>flaglog = 0/1 log terms in the lubrication approximation on/off
|
||||
<LI>cutinner = inner cut off distance (distance units)
|
||||
<LI>cutoff = outer cutoff for interactions (distance units)
|
||||
<LI>gdot = shear rate (1/time units)
|
||||
</UL>
|
||||
<P><B>Examples:</B> (all assume radius = 1)
|
||||
</P>
|
||||
<PRE>pair_style lubricateU 1.5 1 2.01 2.5 0.01
|
||||
pair_coeff 1 1 2.05 2.8
|
||||
pair_coeff * *
|
||||
</PRE>
|
||||
<P><B>Description:</B>
|
||||
</P>
|
||||
<P>Styles <I>lubricateU</I> and <I>lubricateU/poly</I> compute velocities and
|
||||
angular velocities such that the hydrodynamic interaction balances the
|
||||
force and torque due to all other types of interactions.
|
||||
</P>
|
||||
<P>The interactions have 2 components. The first is
|
||||
Ball-Melrose lubrication terms via the formulas in <A HREF = "#Ball">(Ball and
|
||||
Melrose)</A>
|
||||
</P>
|
||||
<CENTER><IMG SRC = "Eqs/pair_lubricate.jpg">
|
||||
</CENTER>
|
||||
<P>which represents the dissipation W between two nearby particles due to
|
||||
their relative velocities in the presence of a background solvent with
|
||||
viscosity mu. Note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
</P>
|
||||
<P>The Asq (squeeze) term is the strongest and is always included. It
|
||||
scales as 1/gap where gap is the separation between the surfaces of
|
||||
the 2 particles. The Ash (shear) and Apu (pump) terms are only
|
||||
include if <I>flaglog</I> is set to 1. Thy are the next strongest
|
||||
interactions, and the only other singular interaction, and scale as
|
||||
log(gap). The Atw (twist) term is currently not included. It is
|
||||
typically a very small contribution to the lubrication forces.
|
||||
</P>
|
||||
<P><I>Cutinner</I> sets the minimum center-to-center separation that will be
|
||||
used in calculations irrespective of the actual separation. <I>Cutoff</I>
|
||||
is the maximum center-to-center separation at which an interaction is
|
||||
computed. Using a <I>cutoff</I> less than 3 radii is recommended if
|
||||
<I>flaglog</I> is set to 1.
|
||||
</P>
|
||||
<P>The other component is due to the Fast Lubrication Dynamics (FLD)
|
||||
approximation, described in <A HREF = "#Higdon">(Higdon)</A>. The equation being
|
||||
solved to balance the forces and torques is
|
||||
</P>
|
||||
<CENTER><IMG SRC = "Eqs/fld2.jpg">
|
||||
</CENTER>
|
||||
<P>where U represents the velocities and angular velocities of the
|
||||
particles, U<I>infty</I> represents the velocities and the angular
|
||||
velocities of the undisturbed fluid, and E<I>infty</I> represents the rate
|
||||
of strain tensor of the undisturbed fluid flow with viscosity mu.
|
||||
Again, note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
</P>
|
||||
<P>F<I>rest</I> represents the forces and torques due to all other types of
|
||||
interactions, e.g. Brownian, electrostatic etc. Note that this
|
||||
algorithm neglects the inertial terms, thereby removing the
|
||||
restriction of resolving the small interial time scale, which may not
|
||||
be of interest for colloidal particles. This pair style solves for
|
||||
the velocity such that the hydrodynamic force balances all other types
|
||||
of forces, thereby resulting in a net zero force (zero inertia limit).
|
||||
When defining this pair style, it must be defined last so that when
|
||||
this style is invoked all other types of forces have already been
|
||||
computed. For the same reason, it won't work if additional non-pair
|
||||
styles are defined (such as bond or Kspace forces) as they are
|
||||
calculated in LAMMPS after the pairwise interactions have been
|
||||
computed.
|
||||
</P>
|
||||
<P>IMPORTANT NOTE: When using these styles, the these pair styles are
|
||||
designed to be used with implicit time integration and a
|
||||
correspondingly larger timestep. Thus either <A HREF = "fix_nve_noforce.html">fix
|
||||
nve/noforce</A> should be used for spherical
|
||||
particles defined via <A HREF = "atom_style.html">atom_style sphere</A> or <A HREF = "fix_nve_asphere_noforce.html">fix
|
||||
nve/asphere/noforce</A> should be used for
|
||||
spherical particles defined via <A HREF = "atom_style.html">atom_style
|
||||
ellipsoid</A>. This is because the velocity and angular
|
||||
momentum of each particle is set by the pair style, and should not be
|
||||
reset by the time integration fix.
|
||||
</P>
|
||||
<P>Style <I>lubricateU</I> requires monodisperse spherical particles; style
|
||||
<I>lubricateU/poly</I> allows for polydisperse spherical particles.
|
||||
</P>
|
||||
<P>If the suspension is sheared via the <A HREF = "fix_deform.html">fix deform</A>
|
||||
command then the pair style uses the shear rate to adjust the
|
||||
hydrodynamic interactions accordingly.
|
||||
</P>
|
||||
<P>Since lubrication forces are dissipative, it is usually desirable to
|
||||
thermostat the system at a constant temperature. If Brownian motion
|
||||
(at a constant temperature) is desired, it can be set using the
|
||||
<A HREF = "pair_brownian.html">pair_style brownian</A> command. These pair styles
|
||||
and the <I>brownian</I> style should use consistent parameters for <I>mu</I>,
|
||||
<I>flaglog</I>, <I>flagfld = 1</I>, <I>cutinner</I>, and <I>cutoff</I>.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P>The following coefficients must be defined for each pair of atoms
|
||||
types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
|
||||
above, or in the data file or restart files read by the
|
||||
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
|
||||
commands, or by mixing as described below:
|
||||
</P>
|
||||
<UL><LI>cutinner (distance units)
|
||||
<LI>cutoff (distance units)
|
||||
</UL>
|
||||
<P>The two coefficients are optional. If neither is specified, the two
|
||||
cutoffs specified in the pair_style command are used. Otherwise both
|
||||
must be specified.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
|
||||
</P>
|
||||
<P>For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is <I>geometric</I>. See
|
||||
the "pair_modify" command for details.
|
||||
</P>
|
||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
||||
shift option for the energy of the pair interaction.
|
||||
</P>
|
||||
<P>The <A HREF = "pair_modify.html">pair_modify</A> table option is not relevant
|
||||
for this pair style.
|
||||
</P>
|
||||
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
|
||||
tail option for adding long-range tail corrections to energy and
|
||||
pressure.
|
||||
</P>
|
||||
<P>This pair style writes its information to <A HREF = "restart.html">binary restart
|
||||
files</A>, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
</P>
|
||||
<P>This pair style can only be used via the <I>pair</I> keyword of the
|
||||
<A HREF = "run_style.html">run_style respa</A> command. It does not support the
|
||||
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P><B>Restrictions:</B>
|
||||
</P>
|
||||
<P>These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
|
||||
LAMMPS</A> section for more info.
|
||||
</P>
|
||||
<P>Currently, these pair styles assume that all other types of
|
||||
forces/torques on the particles have been already been computed when
|
||||
it is invoked. This requires this style to be defined as the last of
|
||||
the pair styles, and that no fixes apply additional constraint forces.
|
||||
One exception is the <A HREF = "fix_wall.html">fix wall/colloid</A> command, which
|
||||
has an "fld" option to apply its wall forces correctly.
|
||||
</P>
|
||||
<P>Only spherical monodisperse particles are allowed for pair_style
|
||||
lubricateU.
|
||||
</P>
|
||||
<P>Only spherical particles are allowed for pair_style lubricateU/poly.
|
||||
</P>
|
||||
<P>For sheared suspensions, it is assumed that the shearing is done in
|
||||
the xy plane, with x being the velocity direction and y being the
|
||||
velocity-gradient direction. In this case, one must use <A HREF = "fix_deform.html">fix
|
||||
deform</A> with the same rate of shear (erate).
|
||||
</P>
|
||||
<P><B>Related commands:</B>
|
||||
</P>
|
||||
<P><A HREF = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_lubricate.html">pair_style
|
||||
lubricate</A>
|
||||
</P>
|
||||
<P><B>Default:</B> none
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<A NAME = "Ball"></A>
|
||||
|
||||
<P><B>(Ball)</B> Ball and Melrose, Physica A, 247, 444-472 (1997).
|
||||
</P>
|
||||
<A NAME = "Higdon"></A>
|
||||
|
||||
<P><B>(Higdon)</B> Amit and Higdon, Phys Rev E (2010).
|
||||
</P>
|
||||
</HTML>
|
||||
|
|
@ -0,0 +1,191 @@
|
|||
"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)
|
||||
|
||||
:line
|
||||
|
||||
pair_style lubricateU command :h3
|
||||
pair_style lubricateU/poly command :h3
|
||||
|
||||
[Syntax:]
|
||||
|
||||
pair_style style mu flaglog cutinner cutoff gdot :pre
|
||||
|
||||
style = {lubricateU} or {lubricateU/poly}
|
||||
mu = dynamic viscosity (dynamic viscosity units)
|
||||
flaglog = 0/1 log terms in the lubrication approximation on/off
|
||||
cutinner = inner cut off distance (distance units)
|
||||
cutoff = outer cutoff for interactions (distance units)
|
||||
gdot = shear rate (1/time units) :ul
|
||||
|
||||
[Examples:] (all assume radius = 1)
|
||||
|
||||
pair_style lubricateU 1.5 1 2.01 2.5 0.01
|
||||
pair_coeff 1 1 2.05 2.8
|
||||
pair_coeff * * :pre
|
||||
|
||||
[Description:]
|
||||
|
||||
Styles {lubricateU} and {lubricateU/poly} compute velocities and
|
||||
angular velocities such that the hydrodynamic interaction balances the
|
||||
force and torque due to all other types of interactions.
|
||||
|
||||
The interactions have 2 components. The first is
|
||||
Ball-Melrose lubrication terms via the formulas in "(Ball and
|
||||
Melrose)"_#Ball
|
||||
|
||||
:c,image(Eqs/pair_lubricate.jpg)
|
||||
|
||||
which represents the dissipation W between two nearby particles due to
|
||||
their relative velocities in the presence of a background solvent with
|
||||
viscosity mu. Note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
|
||||
The Asq (squeeze) term is the strongest and is always included. It
|
||||
scales as 1/gap where gap is the separation between the surfaces of
|
||||
the 2 particles. The Ash (shear) and Apu (pump) terms are only
|
||||
include if {flaglog} is set to 1. Thy are the next strongest
|
||||
interactions, and the only other singular interaction, and scale as
|
||||
log(gap). The Atw (twist) term is currently not included. It is
|
||||
typically a very small contribution to the lubrication forces.
|
||||
|
||||
{Cutinner} sets the minimum center-to-center separation that will be
|
||||
used in calculations irrespective of the actual separation. {Cutoff}
|
||||
is the maximum center-to-center separation at which an interaction is
|
||||
computed. Using a {cutoff} less than 3 radii is recommended if
|
||||
{flaglog} is set to 1.
|
||||
|
||||
The other component is due to the Fast Lubrication Dynamics (FLD)
|
||||
approximation, described in "(Higdon)"_#Higdon. The equation being
|
||||
solved to balance the forces and torques is
|
||||
|
||||
:c,image(Eqs/fld2.jpg)
|
||||
|
||||
where U represents the velocities and angular velocities of the
|
||||
particles, U{infty} represents the velocities and the angular
|
||||
velocities of the undisturbed fluid, and E{infty} represents the rate
|
||||
of strain tensor of the undisturbed fluid flow with viscosity mu.
|
||||
Again, note that this is dynamic viscosity which has units of
|
||||
mass/distance/time, not kinematic viscosity.
|
||||
|
||||
F{rest} represents the forces and torques due to all other types of
|
||||
interactions, e.g. Brownian, electrostatic etc. Note that this
|
||||
algorithm neglects the inertial terms, thereby removing the
|
||||
restriction of resolving the small interial time scale, which may not
|
||||
be of interest for colloidal particles. This pair style solves for
|
||||
the velocity such that the hydrodynamic force balances all other types
|
||||
of forces, thereby resulting in a net zero force (zero inertia limit).
|
||||
When defining this pair style, it must be defined last so that when
|
||||
this style is invoked all other types of forces have already been
|
||||
computed. For the same reason, it won't work if additional non-pair
|
||||
styles are defined (such as bond or Kspace forces) as they are
|
||||
calculated in LAMMPS after the pairwise interactions have been
|
||||
computed.
|
||||
|
||||
IMPORTANT NOTE: When using these styles, the these pair styles are
|
||||
designed to be used with implicit time integration and a
|
||||
correspondingly larger timestep. Thus either "fix
|
||||
nve/noforce"_fix_nve_noforce.html should be used for spherical
|
||||
particles defined via "atom_style sphere"_atom_style.html or "fix
|
||||
nve/asphere/noforce"_fix_nve_asphere_noforce.html should be used for
|
||||
spherical particles defined via "atom_style
|
||||
ellipsoid"_atom_style.html. This is because the velocity and angular
|
||||
momentum of each particle is set by the pair style, and should not be
|
||||
reset by the time integration fix.
|
||||
|
||||
Style {lubricateU} requires monodisperse spherical particles; style
|
||||
{lubricateU/poly} allows for polydisperse spherical particles.
|
||||
|
||||
If the suspension is sheared via the "fix deform"_fix_deform.html
|
||||
command then the pair style uses the shear rate to adjust the
|
||||
hydrodynamic interactions accordingly.
|
||||
|
||||
Since lubrication forces are dissipative, it is usually desirable to
|
||||
thermostat the system at a constant temperature. If Brownian motion
|
||||
(at a constant temperature) is desired, it can be set using the
|
||||
"pair_style brownian"_pair_brownian.html command. These pair styles
|
||||
and the {brownian} style should use consistent parameters for {mu},
|
||||
{flaglog}, {flagfld = 1}, {cutinner}, and {cutoff}.
|
||||
|
||||
:line
|
||||
|
||||
The following coefficients must be defined for each pair of atoms
|
||||
types via the "pair_coeff"_pair_coeff.html command as in the examples
|
||||
above, or in the data file or restart files read by the
|
||||
"read_data"_read_data.html or "read_restart"_read_restart.html
|
||||
commands, or by mixing as described below:
|
||||
|
||||
cutinner (distance units)
|
||||
cutoff (distance units) :ul
|
||||
|
||||
The two coefficients are optional. If neither is specified, the two
|
||||
cutoffs specified in the pair_style command are used. Otherwise both
|
||||
must be specified.
|
||||
|
||||
:line
|
||||
|
||||
[Mixing, shift, table, tail correction, restart, rRESPA info]:
|
||||
|
||||
For atom type pairs I,J and I != J, the two cutoff distances for this
|
||||
pair style can be mixed. The default mix value is {geometric}. See
|
||||
the "pair_modify" command for details.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
shift option for the energy of the pair interaction.
|
||||
|
||||
The "pair_modify"_pair_modify.html table option is not relevant
|
||||
for this pair style.
|
||||
|
||||
This pair style does not support the "pair_modify"_pair_modify.html
|
||||
tail option for adding long-range tail corrections to energy and
|
||||
pressure.
|
||||
|
||||
This pair style writes its information to "binary restart
|
||||
files"_restart.html, so pair_style and pair_coeff commands do not need
|
||||
to be specified in an input script that reads a restart file.
|
||||
|
||||
This pair style can only be used via the {pair} keyword of the
|
||||
"run_style respa"_run_style.html command. It does not support the
|
||||
{inner}, {middle}, {outer} keywords.
|
||||
|
||||
:line
|
||||
|
||||
[Restrictions:]
|
||||
|
||||
These styles are part of the FLD package. They are only enabled if
|
||||
LAMMPS was built with that package. See the "Making
|
||||
LAMMPS"_Section_start.html#2_3 section for more info.
|
||||
|
||||
Currently, these pair styles assume that all other types of
|
||||
forces/torques on the particles have been already been computed when
|
||||
it is invoked. This requires this style to be defined as the last of
|
||||
the pair styles, and that no fixes apply additional constraint forces.
|
||||
One exception is the "fix wall/colloid"_fix_wall.html command, which
|
||||
has an "fld" option to apply its wall forces correctly.
|
||||
|
||||
Only spherical monodisperse particles are allowed for pair_style
|
||||
lubricateU.
|
||||
|
||||
Only spherical particles are allowed for pair_style lubricateU/poly.
|
||||
|
||||
For sheared suspensions, it is assumed that the shearing is done in
|
||||
the xy plane, with x being the velocity direction and y being the
|
||||
velocity-gradient direction. In this case, one must use "fix
|
||||
deform"_fix_deform.html with the same rate of shear (erate).
|
||||
|
||||
[Related commands:]
|
||||
|
||||
"pair_coeff"_pair_coeff.html, "pair_style
|
||||
lubricate"_pair_lubricate.html
|
||||
|
||||
[Default:] none
|
||||
|
||||
:line
|
||||
|
||||
:link(Ball)
|
||||
[(Ball)] Ball and Melrose, Physica A, 247, 444-472 (1997).
|
||||
|
||||
:link(Higdon)
|
||||
[(Higdon)] Amit and Higdon, Phys Rev E (2010).
|
||||
Loading…
Reference in New Issue