2015-07-30 22:53:28 +08:00
<!DOCTYPE html>
<!-- [if IE 8]><html class="no - js lt - ie9" lang="en" > <![endif] -->
<!-- [if gt IE 8]><! --> < html class = "no-js" lang = "en" > <!-- <![endif] -->
< head >
< meta charset = "utf-8" >
< meta name = "viewport" content = "width=device-width, initial-scale=1.0" >
2015-12-21 23:20:41 +08:00
< title > pair_style lubricate command — LAMMPS documentation< / title >
2015-07-30 22:53:28 +08:00
< link rel = "stylesheet" href = "_static/css/theme.css" type = "text/css" / >
< link rel = "stylesheet" href = "_static/sphinxcontrib-images/LightBox2/lightbox2/css/lightbox.css" type = "text/css" / >
2015-12-21 23:20:41 +08:00
< link rel = "top" title = "LAMMPS documentation" href = "index.html" / >
2015-07-30 22:53:28 +08:00
< script src = "_static/js/modernizr.min.js" > < / script >
< / head >
< body class = "wy-body-for-nav" role = "document" >
< div class = "wy-grid-for-nav" >
< nav data-toggle = "wy-nav-shift" class = "wy-nav-side" >
< div class = "wy-side-nav-search" >
< a href = "Manual.html" class = "icon icon-home" > LAMMPS
< / a >
< div role = "search" >
< form id = "rtd-search-form" class = "wy-form" action = "search.html" method = "get" >
< input type = "text" name = "q" placeholder = "Search docs" / >
< input type = "hidden" name = "check_keywords" value = "yes" / >
< input type = "hidden" name = "area" value = "default" / >
< / form >
< / div >
< / div >
< div class = "wy-menu wy-menu-vertical" data-spy = "affix" role = "navigation" aria-label = "main navigation" >
< ul >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_intro.html" > 1. Introduction< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_start.html" > 2. Getting Started< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_commands.html" > 3. Commands< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_packages.html" > 4. Packages< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_accelerate.html" > 5. Accelerating LAMMPS performance< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_howto.html" > 6. How-to discussions< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_example.html" > 7. Example problems< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_perf.html" > 8. Performance & scalability< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_tools.html" > 9. Additional tools< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_modify.html" > 10. Modifying & extending LAMMPS< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_python.html" > 11. Python interface to LAMMPS< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_errors.html" > 12. Errors< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_history.html" > 13. Future and history< / a > < / li >
< / ul >
< / div >
< / nav >
< section data-toggle = "wy-nav-shift" class = "wy-nav-content-wrap" >
< nav class = "wy-nav-top" role = "navigation" aria-label = "top navigation" >
< i data-toggle = "wy-nav-top" class = "fa fa-bars" > < / i >
< a href = "Manual.html" > LAMMPS< / a >
< / nav >
< div class = "wy-nav-content" >
< div class = "rst-content" >
< div role = "navigation" aria-label = "breadcrumbs navigation" >
< ul class = "wy-breadcrumbs" >
< li > < a href = "Manual.html" > Docs< / a > » < / li >
< li > pair_style lubricate command< / li >
< li class = "wy-breadcrumbs-aside" >
< a href = "http://lammps.sandia.gov" > Website< / a >
< a href = "Section_commands.html#comm" > Commands< / a >
< / li >
< / ul >
< hr / >
< / div >
< div role = "main" class = "document" itemscope = "itemscope" itemtype = "http://schema.org/Article" >
< div itemprop = "articleBody" >
< div class = "section" id = "pair-style-lubricate-command" >
< span id = "index-0" > < / span > < h1 > pair_style lubricate command< a class = "headerlink" href = "#pair-style-lubricate-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< / div >
< div class = "section" id = "pair-style-lubricate-omp-command" >
< h1 > pair_style lubricate/omp command< a class = "headerlink" href = "#pair-style-lubricate-omp-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< / div >
< div class = "section" id = "pair-style-lubricate-poly-command" >
< h1 > pair_style lubricate/poly command< a class = "headerlink" href = "#pair-style-lubricate-poly-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< / div >
< div class = "section" id = "pair-style-lubricate-poly-omp-command" >
< h1 > pair_style lubricate/poly/omp command< a class = "headerlink" href = "#pair-style-lubricate-poly-omp-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< div class = "section" id = "syntax" >
< h2 > Syntax< a class = "headerlink" href = "#syntax" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-python" > < div class = "highlight" > < pre > pair_style style mu flaglog flagfld cutinner cutoff flagHI flagVF
< / pre > < / div >
< / div >
< ul class = "simple" >
< li > style = < em > lubricate< / em > or < em > lubricate/poly< / em > < / li >
< li > mu = dynamic viscosity (dynamic viscosity units)< / li >
< li > flaglog = 0/1 to exclude/include log terms in the lubrication approximation< / li >
< li > flagfld = 0/1 to exclude/include Fast Lubrication Dynamics (FLD) effects< / li >
< li > cutinner = inner cutoff distance (distance units)< / li >
< li > cutoff = outer cutoff for interactions (distance units)< / li >
< li > flagHI (optional) = 0/1 to exclude/include 1/r hydrodynamic interactions< / li >
< li > flagVF (optional) = 0/1 to exclude/include volume fraction corrections in the long-range isotropic terms< / li >
< / ul >
< p > < strong > Examples:< / strong > (all assume radius = 1)< / p >
< div class = "highlight-python" > < div class = "highlight" > < pre > pair_style lubricate 1.5 1 1 2.01 2.5
2011-10-27 00:59:49 +08:00
pair_coeff 1 1 2.05 2.8
2015-07-30 22:53:28 +08:00
pair_coeff * *
< / pre > < / div >
< / div >
< div class = "highlight-python" > < div class = "highlight" > < pre > pair_style lubricate 1.5 1 1 2.01 2.5
2011-10-27 00:59:49 +08:00
pair_coeff * *
variable mu equal ramp(1,2)
2015-07-30 22:53:28 +08:00
fix 1 all adapt 1 pair lubricate mu * * v_mu
< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "description" >
< h2 > Description< a class = "headerlink" href = "#description" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > Styles < em > lubricate< / em > and < em > lubricate/poly< / em > compute hydrodynamic
2011-10-27 00:59:49 +08:00
interactions between mono-disperse spherical particles in a pairwise
fashion. The interactions have 2 components. The first is
2015-07-30 22:53:28 +08:00
Ball-Melrose lubrication terms via the formulas in < a class = "reference internal" href = "pair_lubricateU.html#ball" > < span > (Ball and Melrose)< / span > < / a > < / p >
< img alt = "_images/pair_lubricate.jpg" class = "align-center" src = "_images/pair_lubricate.jpg" / >
< p > which represents the dissipation W between two nearby particles due to
2011-10-27 00:59:49 +08:00
their relative velocities in the presence of a background solvent with
2015-07-30 22:53:28 +08:00
viscosity < em > mu< / em > . 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 included if < em > flagHI< / em > is
2012-05-24 01:47:58 +08:00
set to 1 (default). It scales as 1/gap where gap is the separation
between the surfaces of the 2 particles. The Ash (shear) and Apu
2015-07-30 22:53:28 +08:00
(pump) terms are only included if < em > flaglog< / em > is set to 1. They are the
2012-05-24 01:47:58 +08:00
next strongest interactions, and the only other singular interaction,
2015-07-30 22:53:28 +08:00
and scale as log(gap). Note that < em > flaglog< / em > = 1 and < em > flagHI< / em > = 0 is
invalid, and will result in a warning message, after which < em > flagHI< / em > will
2012-05-24 01:47:58 +08:00
be set to 1. The Atw (twist) term is currently not included. It is
2015-07-30 22:53:28 +08:00
typically a very small contribution to the lubrication forces.< / p >
< p > The < em > flagHI< / em > and < em > flagVF< / em > settings are optional. Neither should be
used, or both must be defined.< / p >
< p > < em > Cutinner< / em > sets the minimum center-to-center separation that will be
used in calculations irrespective of the actual separation. < em > Cutoff< / em >
2011-10-27 00:59:49 +08:00
is the maximum center-to-center separation at which an interaction is
2015-07-30 22:53:28 +08:00
computed. Using a < em > cutoff< / em > less than 3 radii is recommended if
< em > flaglog< / em > is set to 1.< / p >
< p > The other component is due to the Fast Lubrication Dynamics (FLD)
approximation, described in < a class = "reference internal" href = "pair_lubricateU.html#kumar" > < span > (Kumar)< / span > < / a > , which can be
represented by the following equation< / p >
< img alt = "_images/fld.jpg" class = "align-center" src = "_images/fld.jpg" / >
< p > 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 < em > mu< / em > . Again, note that
2011-10-27 00:59:49 +08:00
this is dynamic viscosity which has units of mass/distance/time, not
2012-05-24 01:47:58 +08:00
kinematic viscosity. Volume fraction corrections to R_FU are included
2015-07-30 22:53:28 +08:00
as long as < em > flagVF< / em > is set to 1 (default).< / p >
2015-12-11 01:23:56 +08:00
< div class = "admonition note" >
< p class = "first admonition-title" > Note< / p >
< p class = "last" > 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 class = "reference internal" href = "fix_nve_sphere.html" > < em > fix nve/sphere< / em > < / a > or < a class = "reference internal" href = "fix_nve_asphere.html" > < em > fix nve/asphere< / em > < / a > should be used for time integration.
2015-07-30 22:53:28 +08:00
To perform implicit FLD, see the < a class = "reference internal" href = "pair_lubricateU.html" > < em > pair_style lubricateU< / em > < / a > command.< / p >
< / div >
< p > Style < em > lubricate< / em > requires monodisperse spherical particles; style
< em > lubricate/poly< / em > allows for polydisperse spherical particles.< / p >
< p > The viscosity < em > mu< / em > can be varied in a time-dependent manner over the
2011-10-27 00:59:49 +08:00
course of a simluation, in which case in which case the pair_style
2015-07-30 22:53:28 +08:00
setting for < em > mu< / em > will be overridden. See the < a class = "reference internal" href = "fix_adapt.html" > < em > fix adapt< / em > < / a >
command for details.< / p >
< p > If the suspension is sheared via the < a class = "reference internal" href = "fix_deform.html" > < em > fix deform< / em > < / a >
2011-10-27 00:59:49 +08:00
command then the pair style uses the shear rate to adjust the
2012-05-24 01:47:58 +08:00
hydrodynamic interactions accordingly. Volume changes due to fix
deform are accounted for when computing the volume fraction
2015-07-30 22:53:28 +08:00
corrections to R_FU.< / p >
< p > When computing the volume fraction corrections to R_FU, the presence
2012-05-24 01:47:58 +08:00
of walls (whether moving or stationary) will affect the volume
fraction available to colloidal particles. This is currently accounted
2015-07-30 22:53:28 +08:00
for with the following types of walls: < a class = "reference internal" href = "fix_wall.html" > < em > wall/lj93< / em > < / a > ,
< a class = "reference internal" href = "fix_wall.html" > < em > wall/lj126< / em > < / a > , < a class = "reference internal" href = "fix_wall.html" > < em > wall/colloid< / em > < / a > , and
< a class = "reference internal" href = "fix_wall.html" > < em > wall/harmonic< / em > < / a > . For these wall styles, the correct
2012-05-24 01:47:58 +08:00
volume fraction will be used when walls do not coincide with the box
boundary, as well as when walls move and thereby cause a change in the
volume fraction. Other wall styles will still work, but they will
result in the volume fraction being computed based on the box
2015-07-30 22:53:28 +08:00
boundaries.< / p >
< p > Since lubrication forces are dissipative, it is usually desirable to
2012-05-24 01:47:58 +08:00
thermostat the system at a constant temperature. If Brownian motion
2011-10-27 00:59:49 +08:00
(at a constant temperature) is desired, it can be set using the
2015-07-30 22:53:28 +08:00
< a class = "reference internal" href = "pair_brownian.html" > < em > pair_style brownian< / em > < / a > command. These pair styles
and the brownian style should use consistent parameters for < em > mu< / em > ,
< em > flaglog< / em > , < em > flagfld< / em > , < em > cutinner< / em > , < em > cutoff< / em > , < em > flagHI< / em > and < em > flagVF< / em > .< / p >
< hr class = "docutils" / >
< p > The following coefficients must be defined for each pair of atoms
types via the < a class = "reference internal" href = "pair_coeff.html" > < em > pair_coeff< / em > < / a > command as in the examples
2011-10-27 00:59:49 +08:00
above, or in the data file or restart files read by the
2015-07-30 22:53:28 +08:00
< a class = "reference internal" href = "read_data.html" > < em > read_data< / em > < / a > or < a class = "reference internal" href = "read_restart.html" > < em > read_restart< / em > < / a >
commands, or by mixing as described below:< / p >
< ul class = "simple" >
< li > cutinner (distance units)< / li >
< li > cutoff (distance units)< / li >
< / ul >
< p > The two coefficients are optional. If neither is specified, the two
2011-10-27 00:59:49 +08:00
cutoffs specified in the pair_style command are used. Otherwise both
2015-07-30 22:53:28 +08:00
must be specified.< / p >
< hr class = "docutils" / >
< p > Styles with a < em > cuda< / em > , < em > gpu< / em > , < em > intel< / em > , < em > kk< / em > , < em > omp< / em > , or < em > opt< / em > suffix are
2014-08-15 00:30:25 +08:00
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
2015-07-30 22:53:28 +08:00
hardware, as discussed in < a class = "reference internal" href = "Section_accelerate.html" > < em > this section< / em > < / a > of
2014-08-15 00:30:25 +08:00
the manual. The accelerated styles take the same arguments and should
2015-07-30 22:53:28 +08:00
produce the same results, except for round-off and precision issues.< / p >
< p > These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
2014-08-15 00:30:25 +08:00
KOKKOS, USER-OMP and OPT packages, respectively. They are only
2015-07-30 22:53:28 +08:00
enabled if LAMMPS was built with those packages. See the < a class = "reference internal" href = "Section_start.html#start-3" > < span > Making LAMMPS< / span > < / a > section for more info.< / p >
< p > You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the < a class = "reference internal" href = "Section_start.html#start-7" > < span > -suffix command-line switch< / span > < / a > when you invoke LAMMPS, or you can
use the < a class = "reference internal" href = "suffix.html" > < em > suffix< / em > < / a > command in your input script.< / p >
< p > See < a class = "reference internal" href = "Section_accelerate.html" > < em > this section< / em > < / a > of the manual for more
instructions on how to use the accelerated styles effectively.< / p >
< hr class = "docutils" / >
< p > < strong > Mixing, shift, table, tail correction, restart, rRESPA info< / strong > :< / 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 < em > geometric< / em > . See
the “ pair_modify” command for details.< / p >
< p > This pair style does not support the < a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a >
shift option for the energy of the pair interaction.< / p >
< p > The < a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a > table option is not relevant
for this pair style.< / p >
< p > This pair style does not support the < a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a >
2011-10-27 00:59:49 +08:00
tail option for adding long-range tail corrections to energy and
2015-07-30 22:53:28 +08:00
pressure.< / p >
< p > This pair style writes its information to < a class = "reference internal" href = "restart.html" > < em > binary restart files< / em > < / 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 < em > pair< / em > keyword of the
< a class = "reference internal" href = "run_style.html" > < em > run_style respa< / em > < / a > command. It does not support the
< em > inner< / em > , < em > middle< / em > , < em > outer< / em > keywords.< / p >
< / div >
< hr class = "docutils" / >
< div class = "section" id = "restrictions" >
< h2 > Restrictions< a class = "headerlink" href = "#restrictions" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > These styles are part of the FLD package. They are only enabled if
LAMMPS was built with that package. See the < span class = "xref std std-ref" > Making LAMMPS< / span > 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 > These pair styles will not restart exactly when using the
< a class = "reference internal" href = "read_restart.html" > < em > read_restart< / em > < / a > command, though they should provide
2012-06-19 07:15:48 +08:00
statistically similar results. This is because the forces they
compute depend on atom velocities. See the
2015-07-30 22:53:28 +08:00
< a class = "reference internal" href = "read_restart.html" > < em > read_restart< / em > < / a > command for more details.< / p >
< / div >
< div class = "section" id = "related-commands" >
< h2 > Related commands< a class = "headerlink" href = "#related-commands" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > < a class = "reference internal" href = "pair_coeff.html" > < em > pair_coeff< / em > < / a > , < a class = "reference internal" href = "pair_lubricateU.html" > < em > pair_style lubricateU< / em > < / a > < / p >
< / div >
< div class = "section" id = "default" >
< h2 > Default< a class = "headerlink" href = "#default" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > The default settings for the optional args are flagHI = 1 and flagVF =
1.< / p >
< hr class = "docutils" / >
< p id = "ball" > < strong > (Ball)< / strong > Ball and Melrose, Physica A, 247, 444-472 (1997).< / p >
< p id = "kumar" > < strong > (Kumar)< / strong > Kumar and Higdon, Phys Rev E, 82, 051401 (2010). See also
his thesis for more details: A. Kumar, “ Microscale Dynamics in
Suspensions of Non-spherical Particles” , Thesis, University of
2013-05-30 22:10:30 +08:00
Illinois Urbana-Champaign,
2015-07-30 22:53:28 +08:00
(2010). (< a class = "reference external" href = "https://www.ideals.illinois.edu/handle/2142/16032" > https://www.ideals.illinois.edu/handle/2142/16032< / a > )< / p >
< / div >
< / div >
< / div >
< / div >
< footer >
< hr / >
< div role = "contentinfo" >
< p >
2015-12-11 01:23:56 +08:00
© Copyright 2013 Sandia Corporation.
2015-07-30 22:53:28 +08:00
< / p >
< / div >
Built with < a href = "http://sphinx-doc.org/" > Sphinx< / a > using a < a href = "https://github.com/snide/sphinx_rtd_theme" > theme< / a > provided by < a href = "https://readthedocs.org" > Read the Docs< / a > .
< / footer >
< / div >
< / div >
< / section >
< / div >
< script type = "text/javascript" >
var DOCUMENTATION_OPTIONS = {
URL_ROOT:'./',
2015-12-21 23:20:41 +08:00
VERSION:'',
2015-07-30 22:53:28 +08:00
COLLAPSE_INDEX:false,
FILE_SUFFIX:'.html',
HAS_SOURCE: true
};
< / script >
< script type = "text/javascript" src = "_static/jquery.js" > < / script >
< script type = "text/javascript" src = "_static/underscore.js" > < / script >
< script type = "text/javascript" src = "_static/doctools.js" > < / script >
< script type = "text/javascript" src = "https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" > < / script >
< script type = "text/javascript" src = "_static/sphinxcontrib-images/LightBox2/lightbox2/js/jquery-1.11.0.min.js" > < / script >
< script type = "text/javascript" src = "_static/sphinxcontrib-images/LightBox2/lightbox2/js/lightbox.min.js" > < / script >
< script type = "text/javascript" src = "_static/sphinxcontrib-images/LightBox2/lightbox2-customize/jquery-noconflict.js" > < / script >
< script type = "text/javascript" src = "_static/js/theme.js" > < / script >
< script type = "text/javascript" >
jQuery(function () {
SphinxRtdTheme.StickyNav.enable();
});
< / script >
< / body >
< / html >
