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12
doc/angle_coeff.html
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@ -65,7 +65,12 @@ doc page for details.
<P>Here is an alphabetic list of angle styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command:
specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command.
</P>
<P>Note that there are also additional angle styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the angle section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<UL><LI><A HREF = "angle_none.html">angle_style none</A> - turn off angle interactions
<LI><A HREF = "angle_hybrid.html">angle_style hybrid</A> - define multiple styles of angle interactions
@ -79,11 +84,6 @@ specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command
<LI><A HREF = "angle_harmonic.html">angle_style harmonic</A> - harmonic angle
<LI><A HREF = "angle_table.html">angle_style table</A> - tabulated by angle
</UL>
<P>There are also additional angle styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the angle section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/angle_coeff.txt
View File

@ -62,7 +62,12 @@ doc page for details.
Here is an alphabetic list of angle styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "angle_coeff"_angle_coeff.html command:
specified by the associated "angle_coeff"_angle_coeff.html command.
Note that there are also additional angle styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the angle section of "this
page"_Section_commands.html#cmd_5.
"angle_style none"_angle_none.html - turn off angle interactions
"angle_style hybrid"_angle_hybrid.html - define multiple styles of angle interactions :ul
@ -76,11 +81,6 @@ specified by the associated "angle_coeff"_angle_coeff.html command:
"angle_style harmonic"_angle_harmonic.html - harmonic angle
"angle_style table"_angle_table.html - tabulated by angle :ul
There are also additional angle styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the angle section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

12
doc/angle_style.html
View File

@ -57,7 +57,12 @@ between the 3 atoms in the angle.
<P>Here is an alphabetic list of angle styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command:
specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command.
</P>
<P>Note that there are also additional angle styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the angle section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<UL><LI><A HREF = "angle_none.html">angle_style none</A> - turn off angle interactions
<LI><A HREF = "angle_hybrid.html">angle_style hybrid</A> - define multiple styles of angle interactions
@ -71,11 +76,6 @@ specified by the associated <A HREF = "angle_coeff.html">angle_coeff</A> command
<LI><A HREF = "angle_harmonic.html">angle_style harmonic</A> - harmonic angle
<LI><A HREF = "angle_table.html">angle_style table</A> - tabulated by angle
</UL>
<P>There are also additional angle styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the angle section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/angle_style.txt
View File

@ -55,7 +55,12 @@ between the 3 atoms in the angle.
Here is an alphabetic list of angle styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "angle_coeff"_angle_coeff.html command:
specified by the associated "angle_coeff"_angle_coeff.html command.
Note that there are also additional angle styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the angle section of "this
page"_Section_commands.html#cmd_5.
"angle_style none"_angle_none.html - turn off angle interactions
"angle_style hybrid"_angle_hybrid.html - define multiple styles of angle interactions :ul
@ -69,11 +74,6 @@ specified by the associated "angle_coeff"_angle_coeff.html command:
"angle_style harmonic"_angle_harmonic.html - harmonic angle
"angle_style table"_angle_table.html - tabulated by angle :ul
There are also additional angle styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the angle section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

12
doc/bond_coeff.html
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@ -61,7 +61,12 @@ corresponds to the 1st example above would be listed as
<P>Here is an alphabetic list of bond styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command:
specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command.
</P>
<P>Note that here are also additional bond styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the bond section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<UL><LI><A HREF = "bond_none.html">bond_style none</A> - turn off bonded interactions
<LI><A HREF = "bond_hybrid.html">bond_style hybrid</A> - define multiple styles of bond interactions
@ -75,11 +80,6 @@ specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command:
<LI><A HREF = "bond_quartic.html">bond_style quartic</A> - breakable quartic bond
<LI><A HREF = "bond_table.html">bond_style table</A> - tabulated by bond length
</UL>
<P>There are also additional bond styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the bond section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/bond_coeff.txt
View File

@ -58,7 +58,12 @@ corresponds to the 1st example above would be listed as
Here is an alphabetic list of bond styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "bond_coeff"_bond_coeff.html command:
specified by the associated "bond_coeff"_bond_coeff.html command.
Note that here are also additional bond styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the bond section of "this
page"_Section_commands.html#cmd_5.
"bond_style none"_bond_none.html - turn off bonded interactions
"bond_style hybrid"_bond_hybrid.html - define multiple styles of bond interactions :ul
@ -72,11 +77,6 @@ specified by the associated "bond_coeff"_bond_coeff.html command:
"bond_style quartic"_bond_quartic.html - breakable quartic bond
"bond_style table"_bond_table.html - tabulated by bond length :ul
There are also additional bond styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the bond section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

12
doc/bond_style.html
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@ -66,7 +66,12 @@ between the 2 atoms in the bond.
<P>Here is an alphabetic list of bond styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command:
specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command.
</P>
<P>Note that there are also additional bond styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the bond section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<UL><LI><A HREF = "bond_none.html">bond_style none</A> - turn off bonded interactions
<LI><A HREF = "bond_hybrid.html">bond_style hybrid</A> - define multiple styles of bond interactions
@ -80,11 +85,6 @@ specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command:
<LI><A HREF = "bond_quartic.html">bond_style quartic</A> - breakable quartic bond
<LI><A HREF = "bond_table.html">bond_style table</A> - tabulated by bond length
</UL>
<P>There are also additional bond styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the bond section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/bond_style.txt
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@ -63,7 +63,12 @@ between the 2 atoms in the bond.
Here is an alphabetic list of bond styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "bond_coeff"_bond_coeff.html command:
specified by the associated "bond_coeff"_bond_coeff.html command.
Note that there are also additional bond styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the bond section of "this
page"_Section_commands.html#cmd_5.
"bond_style none"_bond_none.html - turn off bonded interactions
"bond_style hybrid"_bond_hybrid.html - define multiple styles of bond interactions :ul
@ -77,11 +82,6 @@ specified by the associated "bond_coeff"_bond_coeff.html command:
"bond_style quartic"_bond_quartic.html - breakable quartic bond
"bond_style table"_bond_table.html - tabulated by bond length :ul
There are also additional bond styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the bond section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

12
doc/dihedral_coeff.html
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@ -67,7 +67,12 @@ page for details.
<P>Here is an alphabetic list of dihedral styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> command:
specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> command.
</P>
<P>Note that there are also additional dihedral styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the dihedral section of
<A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<UL><LI><A HREF = "dihedral_none.html">dihedral_style none</A> - turn off dihedral interactions
<LI><A HREF = "dihedral_hybrid.html">dihedral_style hybrid</A> - define multiple styles of dihedral interactions
@ -79,11 +84,6 @@ specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> c
<LI><A HREF = "dihedral_multi_harmonic.html">dihedral_style multi/harmonic</A> - multi-harmonic dihedral
<LI><A HREF = "dihedral_opls.html">dihedral_style opls</A> - OPLS dihedral
</UL>
<P>There are also additional dihedral styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the dihedral section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/dihedral_coeff.txt
View File

@ -64,7 +64,12 @@ page for details.
Here is an alphabetic list of dihedral styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "dihedral_coeff"_dihedral_coeff.html command:
specified by the associated "dihedral_coeff"_dihedral_coeff.html command.
Note that there are also additional dihedral styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the dihedral section of
"this page"_Section_commands.html#cmd_5.
"dihedral_style none"_dihedral_none.html - turn off dihedral interactions
"dihedral_style hybrid"_dihedral_hybrid.html - define multiple styles of dihedral interactions :ul
@ -76,11 +81,6 @@ specified by the associated "dihedral_coeff"_dihedral_coeff.html command:
"dihedral_style multi/harmonic"_dihedral_multi_harmonic.html - multi-harmonic dihedral
"dihedral_style opls"_dihedral_opls.html - OPLS dihedral :ul
There are also additional dihedral styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the dihedral section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

12
doc/dihedral_style.html
View File

@ -74,7 +74,12 @@ torsions that contain the j-k bond in an i-j-k-l torsion.
<P>Here is an alphabetic list of dihedral styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> command:
specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> command.
</P>
<P>Note that there are also additional dihedral styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the dihedral section of
<A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<UL><LI><A HREF = "dihedral_none.html">dihedral_style none</A> - turn off dihedral interactions
<LI><A HREF = "dihedral_hybrid.html">dihedral_style hybrid</A> - define multiple styles of dihedral interactions
@ -86,11 +91,6 @@ specified by the associated <A HREF = "dihedral_coeff.html">dihedral_coeff</A> c
<LI><A HREF = "dihedral_multi_harmonic.html">dihedral_style multi/harmonic</A> - multi-harmonic dihedral
<LI><A HREF = "dihedral_opls.html">dihedral_style opls</A> - OPLS dihedral
</UL>
<P>There are also additional dihedral styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the dihedral section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/dihedral_style.txt
View File

@ -72,7 +72,12 @@ Some force fields let {n} be positive or negative which corresponds to
Here is an alphabetic list of dihedral styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "dihedral_coeff"_dihedral_coeff.html command:
specified by the associated "dihedral_coeff"_dihedral_coeff.html command.
Note that there are also additional dihedral styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the dihedral section of
"this page"_Section_commands.html#cmd_5.
"dihedral_style none"_dihedral_none.html - turn off dihedral interactions
"dihedral_style hybrid"_dihedral_hybrid.html - define multiple styles of dihedral interactions :ul
@ -84,11 +89,6 @@ specified by the associated "dihedral_coeff"_dihedral_coeff.html command:
"dihedral_style multi/harmonic"_dihedral_multi_harmonic.html - multi-harmonic dihedral
"dihedral_style opls"_dihedral_opls.html - OPLS dihedral :ul
There are also additional dihedral styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the dihedral section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

2
doc/fix_wall.html
View File

@ -192,7 +192,7 @@ fix 1 all wall xlo v_wiggle 1.0 1.0 2.5
fix 1 all wall xlo v_wiggle 1.0 1.0 2.5
</PRE>
<P>The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.
</P>

2
doc/fix_wall.txt
View File

@ -178,7 +178,7 @@ variable wiggle equal cwiggle(0.0,5.0,3.0)
fix 1 all wall xlo v_wiggle 1.0 1.0 2.5 :pre
The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.

334
doc/fix_wall_gran.html
View File

@ -13,7 +13,7 @@
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID wall/gran Kn Kt gamma_n gamma_t xmu dampflag wallstyle args keyword values ...
<PRE>fix ID group-ID wall/gran Kn Kt gamma_n gamma_t xmu dampflag style args ... keyword values ...
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
@ -31,48 +31,63 @@
<LI>dampflag = 0 or 1 if tangential damping force is excluded or included
<LI>wallstyle = <I>xplane</I> or <I>yplane</I> or <I>zplane</I> or <I>zcylinder</I>
<LI>one or more style/arg pairs may be appended
<LI>style = <I>xlo</I> or <I>xhi</I> or <I>ylo</I> or <I>yhi</I> or <I>zlo</I> or <I>zhi</I> or <I>zcylinder</I>
<LI>args = list of arguments for a particular style
<PRE> <I>xplane</I> or <I>yplane</I> or <I>zplane</I> args = lo hi
lo,hi = position of lower and upper plane (distance units), either can be NULL)
<I>zcylinder</I> args = radius
radius = cylinder radius (distance units)
<PRE> <I>xlo</I> or <I>xhi</I> or <I>ylo</I> or <I>yhi</I> or <I>zlo</I> or <I>zhi</I> args = coord vwall
coord = position of wall = constant or variable
constant = number like 0.0 or -30.0 (distance units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_x or v_wiggle
vwall = velocity of wall in normal direction = constant or variable
constant = number like 0.0 or 2.0 (velocity units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_vx or v_wiggle
<I>zcylinder</I> args = rad vrad
rad = radius of cylinder = constant or variable
constant = number like 0.0 or -30.0 (distance units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_rad or v_wiggle
vwall = velocity of radius in normal direction = constant or variable
constant = number like 0.0 or 2.0 (velocity units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_vrad or v_wiggle
</PRE>
<LI>zero or more keyword/value pairs may be appended to args
<LI>keyword = <I>wiggle</I> or <I>shear</I>
<LI>keyword = <I>shear</I> or <I>piston</I>
<PRE> <I>wiggle</I> values = dim amplitude period
dim = <I>x</I> or <I>y</I> or <I>z</I>
amplitude = size of oscillation (distance units)
period = time of oscillation (time units)
<I>shear</I> values = dim vshear
dim = <I>x</I> or <I>y</I> or <I>z</I>
vshear = magnitude of shear velocity (velocity units)
<PRE> <I>shear</I> values = dim vshear
dim = <I>x</I> or <I>y</I> or <I>z</I> or <I>theta</I>
vshear = shear velocity = constant or variable
constant = number like 2.0 or -2.0 (velocity units or radians/time units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_vshear or v_wiggle
<I>piston</I> values = pload pmass
pload = external load on piston = constant or variable
constant = number like 0.0 or 30.0 (force units)
variable = <A HREF = "variable.html">equal-style variable</A> like v_push or v_wiggle
pmass = piston mass (mass units)
</PRE>
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 xplane -10.0 10.0
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 zplane 0.0 NULL
fix 2 all wall/gran 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 wiggle z 3.0 2.0
<PRE>fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 xlo -10.0 0 xhi 10.0 0
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 zhi v_squeeze shear x v_ramp
fix 2 all wall/gran 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 0.0 piston -5000.0 1000.0
</PRE>
<P><B>Description:</B>
</P>
<P>Bound the simulation domain of a granular system with a frictional
wall. All particles in the group interact with the wall when they are
close enough to touch it.
<P>Bound the simulation domain of a granular system with one or more
frictional walls. All particles in the group interact with the wall
when they are close enough to touch it.
</P>
<P>The first set of parameters (Kn, Kt, gamma_n, gamma_t, xmu, and
dampflag) have the same meaning as those specified with the
<P>The first set of parameters (<I>Kn</I>, <I>Kt</I>, <I>gamma_n</I>, <I>gamma_t</I>, <I>xmu</I>,
and <I>dampflag</I>) have the same meaning as those specified with the
<A HREF = "pair_gran.html">pair_style granular</A> force fields. This means a NULL
can be used for either Kt or gamma_t as described on that page. If a
NULL is used for Kt, then a default value is used where Kt = 2/7 Kn.
If a NULL is used for gamma_t, then a default value is used where
gamma_t = 1/2 gamma_n.
can be used for either <I>Kt</I> or <I>gamma_t</I> as described on that page.
If a NULL is used for <I>Kt</I>, then a default value is used where <I>Kt</I> =
2/7 <I>Kn</I>. If a NULL is used for <I>gamma_t</I>, then a default value is
used where <I>gamma_t</I> = 1/2 <I>gamma_n</I>.
</P>
<P>The nature of the wall/particle interactions are determined by which
pair_style is used in your input script: <I>hooke</I>, <I>hooke/history</I>, or
@ -82,9 +97,9 @@ particles touching it is the same as the corresponding equation on the
the two particles going to infinite radius and mass (flat wall).
I.e. delta = radius - r = overlap of particle with wall, m_eff = mass
of particle, and sqrt(RiRj/Ri+Rj) becomes sqrt(radius of particle).
The units for Kn, Kt, gamma_n, and gamma_t are as described on that
doc page. The meaning of xmu and dampflag are also as described on
that page. Note that you can choose different values for these 6
The units for <I>Kn</I>, <I>Kt</I>, <I>gamma_n</I>, and <I>gamma_t</I> are as described on
that doc page. The meaning of xmu and dampflag are also as described
on that page. Note that you can choose different values for these 6
wall/particle coefficients than for particle/particle interactions, if
you wish your wall to interact differently with the particles, e.g. if
the wall is a different material.
@ -103,45 +118,211 @@ common case of a monodisperse system with particles of diameter 1, Kn,
Kt, gamma_n, and gamma_s should be set sqrt(2.0) larger than they were
previously.
</P>
<P>The <I>wallstyle</I> can be planar or cylindrical. The 3 planar options
specify a pair of walls in a dimension. Wall positions are given by
<I>lo</I> and <I>hi</I>. Either of the values can be specified as NULL if a
single wall is desired. For a <I>zcylinder</I> wallstyle, the cylinder's
axis is at x = y = 0.0, and the radius of the cylinder is specified.
<HR>
<P>One or more wall <I>styles</I> can be specified. The <I>xlo</I>, <I>xhi</I>, <I>ylo</I>,
<I>yhi</I>, <I>zlo</I>, <I>zhi</I> styles are planar faces that push particles back
into the box from one of their sides. E.g. the <I>xlo</I> wall should be
positioned to the left of all particles in the x dimension, so that it
pushes particles to the right, and conversely for the <I>xhi</I> wall. The
<I>zcylinder</I> style is a cylindrical shell with its axis along the
z-axis, centered at x = y = 0.0. The interior surface of the cylinder
pushes particles towards the x = y = 0.0 center axis. The <I>zcylinder</I>
style cannot be specified with any of the <I>xlo</I>, <I>xhi</I>, <I>ylo</I>, <I>yhi</I>
styles, but if can be with the <I>zlo</I> or <I>zhi</I> styles.
</P>
<P>Optionally, the wall can be moving, if the <I>wiggle</I> or <I>shear</I>
keywords are appended. Both keywords cannot be used together.
<HR>
<P>For the planer wall styles, <I>coord</I> and <I>vwall</I> arguments are
specified. These are the position and normal velocity of the wall. A
positive velocity means the wall is moving in the positive direction
in the normal dimension, e.g. +x for a <I>xlo</I> or <I>xhi</I> wall. Either or
both of the <I>coord</I> and <I>vwall</I> arguments can be specified as a
constant value or a variable. Note that the force exerted by a wall
on granular particles depends on the velocity of the wall, in both the
normal and tangential directions, so it is important to set <I>vwall</I>
consistent with the <I>coord</I> argument.
</P>
<P>For the <I>wiggle</I> keyword, the wall oscillates sinusoidally, similar to
the oscillations of particles which can be specified by the
<A HREF = "fix_move.html">fix_move</A> command. This is useful in packing
simulations of granular particles. The arguments to the <I>wiggle</I>
keyword specify a dimension for the motion, as well as it's
<I>amplitude</I> and <I>period</I>. Note that if the dimension is in the plane
of the wall, this is effectively a shearing motion. If the dimension
is perpendicular to the wall, it is more of a shaking motion. A
<I>zcylinder</I> wall can only be wiggled in the z dimension.
<P>If a numeric constant is specified for <I>coord</I> then the wall is placed
at that position in the appropriate dimension (x, y, or z) and will
never move. Likewise if a constant is specified for <I>vwall</I>, then the
normal velocity of the wall is set to that value and will never
change.
</P>
<P>Each timestep, the position of a wiggled wall in the appropriate <I>dim</I>
is set according to this equation:
<P>If <I>coord</I> or <I>vwall</I> is a variable, it should be specified as v_name,
where name is an <A HREF = "variable.html">equal-style variable</A> name. In this
case the variable is evaluated each timestep and the result becomes
the current position or normal velocity of the wall. Equal-style
variables can specify formulas with various mathematical functions,
and include <A HREF = "thermo_style.html">thermo_style</A> command keywords for the
simulation box parameters and timestep and elapsed time. Thus it is
easy to specify a time-dependent wall position and velocity.
</P>
<PRE>position = coord + A - A cos (omega * delta)
<P>If <I>coord</I> is specified as a constant, then <I>vwall</I> must be specified
as 0.0. If <I>coord</I> is specified as a variable, then <I>vwall</I> must be a
non-zero constant or a variable. If <I>vwall</I> is specified as a
non-zero constant or variable and <I>coord</I> as a constant, then <I>coord</I>
is treated as the initial position of the wall, and the wall position
is updated each timestep by dt*v_current, where dt = the timestep, and
v_current = the current normal velocity.
</P>
<HR>
<P>For the <I>zcylinder</I> wall style, <I>rad</I> and <I>vrad</I> arguments are
specified. These are the radius and radial velocity of the cylinder.
A positive velocity means the radius is growing. Either or both of
the <I>rad</I> and <I>vrad</I> arguments can be specified as a constant value or
a variable. Note that the force exerted by the wall of the cylinder
on granular particles depends on the velocity of the wall, in both the
normal (radial) and tangential directions, so it is important to set
<I>vrad</I> consistent with the <I>rad</I> argument.
</P>
<P>If a numeric constant is specified for <I>rad</I> then the cylinder will
have a fixed radius. Likewise if a constant is specified for <I>vrad</I>,
then the radial velocity of the cylinder is set to that value and will
never change.
</P>
<P>If <I>rad</I> or <I>vrad</I> is a variable, it should be specified as
v_name, where name is an <A HREF = "variable.html">equal-style variable</A> name.
In this case the variable is evaluated each timestep and the result
becomes the current radius or radial velocity of the cylinder.
Equal-style variables can specify formulas with various mathematical
functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
keywords for the simulation box parameters and timestep and elapsed
time. Thus it is easy to specify a time-dependent cylinder radius and
velocity.
</P>
<P>If <I>rad</I> is specified as a constant, then <I>vrad</I> must be specified as
0.0. If <I>rad</I> is specified as a variable, then <I>vrad</I> must be a
non-zero constant or a variable. If <I>vrad</I> is specified as a non-zero
constant or variable and <I>rad</I> as a constant, then <I>rad</I> is treated as
the initial radius of the wall, and the radius is updated each
timestep by dt*v_current, where dt = the timestep, and v_current = the
current radial velocity.
</P>
<HR>
<P>Here are examples of variable definitions that move the wall position
in a time-dependent fashion using equal-style
<A HREF = "variable.html">variables</A>. They also specify the correct normal
velocity of the wall based on the time derivative of the position.
</P>
<PRE>variable ramp equal ramp(0,10)
variable vnorm equal 10/(10000*dt) # 10000 step run
fix 1 all wall/gran ... xlo v_ramp v_vnorm
</PRE>
<P>where <I>coord</I> is the specified initial position of the wall, <I>A</I> is
the <I>amplitude</I>, <I>omega</I> is 2 PI / <I>period</I>, and <I>delta</I> is the time
elapsed since the fix was specified. The velocity of the wall is set
to the derivative of this expression.
<PRE>variable linear equal vdisplace(0,20)
fix 1 all wall/gran ... xlo v_linear 20
</PRE>
<PRE>variable omega equal 2*PI/3.0
variable wiggle equal swiggle(0.0,5.0,3.0)
variable vwiggle equal "5.0 * v_omega * cos(v_omega*(timestep-startstep)*dt)"
fix 1 all wall/gran ... xlo v_wiggle v_vwiggle
</PRE>
<PRE>variable omega equal 2*PI/3.0
variable wiggle equal cwiggle(0.0,5.0,3.0)
variable vwiggle equal "5.0 * v_omega * sin(v_omega*(timestep-startstep)*dt)"
fix 1 all wall/gran ... xlo v_wiggle v_vwiggle
</PRE>
<P>The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.
</P>
<P>For the <I>shear</I> keyword, the wall moves continuously in the specified
dimension with velocity <I>vshear</I>. The dimension must be tangential to
walls with a planar <I>wallstyle</I>, e.g. in the <I>y</I> or <I>z</I> directions for
an <I>xplane</I> wall. For <I>zcylinder</I> walls, a dimension of <I>z</I> means the
cylinder is moving in the z-direction along it's axis. A dimension of
<I>x</I> or <I>y</I> means the cylinder is spinning around the z-axis, either in
the clockwise direction for <I>vshear</I> > 0 or counter-clockwise for
<I>vshear</I> < 0. In this case, <I>vshear</I> is the tangential velocity of
the wall at whatever <I>radius</I> has been defined.
<P>The swiggle(c0,A,period) function causes the wall position to
oscillate sinusoidally according to this equation, where omega = 2 PI
/ period:
</P>
<PRE>position = c0 + A sin(omega*delta)
</PRE>
<P>The cwiggle(c0,A,period) function causes the wall position to
oscillate sinusoidally according to this equation, which will have an
initial wall velocity of 0.0, and thus may impose a gentler
perturbation on the particles:
</P>
<PRE>position = c0 + A (1 - cos(omega*delta))
</PRE>
<HR>
<P>The optional keywords <I>shear</I> and <I>piston</I> are applied to all the
specified wall styles. If you need to apply different options to
different wall styles, then you should use multiple fix wall/gran
commands.
</P>
<HR>
<P>The <I>shear</I> keyword allows specification of one or two tangential
velocities for planar or <I>zcylinder</I> walls. The <I>dim</I> value specifies
the velocity direction. <I>X</I>, <I>y</I>, and <I>z</I> can be used for planar
walls, but not for the direction normal to the wall. <I>Z</I> and <I>theta</I>
can be used for a <I>zcylinder</I> wall. <I>Theta</I> is the azimuthal angle in
the xy plane, i.e. a rotation of the cylinder about its vertical z
axis. Note that a positive theta velocity means increasing theta,
i.e. rotation in a counter-clockwise direction when looking down on
the xy plane from above.
</P>
<P><I>Vshear</I> is the magnitude of the shear velocity and can be specified
as a numeric constant or variable. The units of <I>vshear</I> are velocity
units for dim = <I>x</I>, <I>y</I>, or <I>z</I>. They are units of radians/time for
<I>dim</I> = <I>theta</I>.
</P>
<P>If a numeric constant is used, then then the shear velocity will never
change. If <I>vshear</I> is a variable, it should be specified as v_name,
where name is an <A HREF = "variable.html">equal-style variable</A> name. In this
case the variable is evaluated each timestep and the result becomes
the current shear velocity. Equal-style variables can specify
formulas with various mathematical functions, and include
<A HREF = "thermo_style.html">thermo_style</A> command keywords for the simulation
box parameters and timestep and elapsed time. Thus it is easy to
specify a time-dependent shear velocity.
</P>
<HR>
<P>The <I>piston</I> keyword allows specification of an external loading force
on the wall, which is opposed by granular particles pushing back
against the load. The wall position and normal velocity adjust
dynamically in response to these 2 opposing forces.
</P>
<P><I>Pload</I> is the magnitude of the loading force and can be specified as
a numeric constant or variable. This force must have a value less
than 0.0 which means that it is directed inward towards the particles.
Thus for a <I>xlo</I> wall, a negative values is a force in the +x
direction. For a <I>xhi</I> wall a negative values is a force in the -x
direction. For a <I>zcylinder</I> wall, a negative value is a force
towards the center z axis of the cylinder.
</P>
<P>If a numeric constant is used for <I>pload</I>, then then the load force
will never change. If <I>pload</I> is a variable, it should be specified
as v_name, where name is an <A HREF = "variable.html">equal-style variable</A> name.
In this case the variable is evaluated each timestep and the result
becomes the current load force. Equal-style variables can specify
formulas with various mathematical functions, and include
<A HREF = "thermo_style.html">thermo_style</A> command keywords for the simulation
box parameters and timestep and elapsed time. Thus it is easy to
specify a time-dependent load force.
</P>
<P>When the <I>piston</I> keyword is used, the <I>coord</I> and <I>vwall</I> arguemnts
for each wall style (or <I>rad</I> and <I>vrad</I> arguments for a <I>zcylinder</I>
style) must be numeric constants and are treated as initial values of
the position/radius and velocity/radial-velocity. The initial values
are updated every timestep by integrating these equations in a
velocity-Verlet fashion:
</P>
<PRE>vwall_new = vwall + dt * (Fload + Fparticles) / pmass
xwall_new = xwall + dt * vwall_new
</PRE>
<P>Fload and Fparticles are the force on the wall due to the external
load and interactions with particles respectively. Fparticles is
always a positive value, representing particles pushing outward on the
wall (-x direction for a <I>xlo</I> wall, +x direction for a <I>xhi</I> wall,
radially outward for a <I>zylinder</I> wall). Thus Fload and Fparticles
will always have opposite signs. <I>Pmass</I> is the mass of the wall, as
specified with the <I>piston</I> keyword. Xwall and Vwall are the wall
position (or radius) and normal velocity (or radial velocity) on the
previous timestep. Xwall_new and vwall_new are the updated values.
</P>
<HR>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>This fix writes the shear friction state of atoms interacting with the
@ -152,10 +333,31 @@ info on how to re-specify a fix in an input script that reads a
restart file, so that the operation of the fix continues in an
uninterrupted fashion.
</P>
<P>The fix does not write any information about the walls (e,g, position
or velocity) to the restart file. It is up to you to insure that fix
wall/gran commands you re-specify in a restart input script are
consistent with the previous simulation.
</P>
<P>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#howto_15">output commands</A>. No
parameter of this fix can be used with the <I>start/stop</I> keywords of
fix.
</P>
<P>This fix computes a global vector of values, which can be accessed by
various <A HREF = "Section_howto.html#howto_15">output commands</A>. The length of
the vector is 4*Nstyle, where Nstyle is the number of styles
specified.
</P>
<P>The 4 values (per style) are as follows:
</P>
<PRE>(1) position (or radius) of wall (distance units)
(2) normal (or radial) velocity of wall (velocity or radians/time units)
(3) positive force on wall due to particles (force units)
(4) negative force on wall due to external load (force units)
</PRE>
<P>The sign conventions for these values are as described above. The 4th
value will be 0.0 if the <I>piston</I> keyword is not used. The vector
values calculated by this fix are "extensive".
</P>
<P>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>
@ -171,6 +373,8 @@ LAMMPS</A> section for more info.
</P>
<P><A HREF = "fix_move.html">fix_move</A>, <A HREF = "pair_gran.html">pair_style granular</A>
</P>
<P><B>Default:</B> none
<P><B>Default:</B>
</P>
<P>The default shear velocities are 0.0.
</P>
</HTML>

332
doc/fix_wall_gran.txt
View File

@ -10,7 +10,7 @@ fix wall/gran command :h3
[Syntax:]
fix ID group-ID wall/gran Kn Kt gamma_n gamma_t xmu dampflag wallstyle args keyword values ... :pre
fix ID group-ID wall/gran Kn Kt gamma_n gamma_t xmu dampflag style args ... keyword values ... :pre
ID, group-ID are documented in "fix"_fix.html command :ulb,l
wall/gran = style name of this fix command :l
@ -20,42 +20,56 @@ gamma_n = damping coefficient for collisions in normal direction (1/time units o
gamma_t = damping coefficient for collisions in tangential direction (1/time units or 1/time-distance units - see discussion below) :l
xmu = static yield criterion (unitless fraction between 0.0 and 1.0) :l
dampflag = 0 or 1 if tangential damping force is excluded or included :l
wallstyle = {xplane} or {yplane} or {zplane} or {zcylinder} :l
one or more style/arg pairs may be appended :l
style = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi} or {zcylinder} :l
args = list of arguments for a particular style :l
{xplane} or {yplane} or {zplane} args = lo hi
lo,hi = position of lower and upper plane (distance units), either can be NULL)
{zcylinder} args = radius
radius = cylinder radius (distance units) :pre
{xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi} args = coord vwall
coord = position of wall = constant or variable
constant = number like 0.0 or -30.0 (distance units)
variable = "equal-style variable"_variable.html like v_x or v_wiggle
vwall = velocity of wall in normal direction = constant or variable
constant = number like 0.0 or 2.0 (velocity units)
variable = "equal-style variable"_variable.html like v_vx or v_wiggle
{zcylinder} args = rad vrad
rad = radius of cylinder = constant or variable
constant = number like 0.0 or -30.0 (distance units)
variable = "equal-style variable"_variable.html like v_rad or v_wiggle
vwall = velocity of radius in normal direction = constant or variable
constant = number like 0.0 or 2.0 (velocity units)
variable = "equal-style variable"_variable.html like v_vrad or v_wiggle :pre
zero or more keyword/value pairs may be appended to args :l
keyword = {wiggle} or {shear} :l
{wiggle} values = dim amplitude period
dim = {x} or {y} or {z}
amplitude = size of oscillation (distance units)
period = time of oscillation (time units)
keyword = {shear} or {piston} :l
{shear} values = dim vshear
dim = {x} or {y} or {z}
vshear = magnitude of shear velocity (velocity units) :pre
dim = {x} or {y} or {z} or {theta}
vshear = shear velocity = constant or variable
constant = number like 2.0 or -2.0 (velocity units or radians/time units)
variable = "equal-style variable"_variable.html like v_vshear or v_wiggle
{piston} values = pload pmass
pload = external load on piston = constant or variable
constant = number like 0.0 or 30.0 (force units)
variable = "equal-style variable"_variable.html like v_push or v_wiggle
pmass = piston mass (mass units) :pre
:ule
[Examples:]
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 xplane -10.0 10.0
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 zplane 0.0 NULL
fix 2 all wall/gran 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 wiggle z 3.0 2.0 :pre
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 xlo -10.0 0 xhi 10.0 0
fix 1 all wall/gran 200000.0 NULL 50.0 NULL 0.5 0 zhi v_squeeze shear x v_ramp
fix 2 all wall/gran 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 0.0 piston -5000.0 1000.0 :pre
[Description:]
Bound the simulation domain of a granular system with a frictional
wall. All particles in the group interact with the wall when they are
close enough to touch it.
Bound the simulation domain of a granular system with one or more
frictional walls. All particles in the group interact with the wall
when they are close enough to touch it.
The first set of parameters (Kn, Kt, gamma_n, gamma_t, xmu, and
dampflag) have the same meaning as those specified with the
The first set of parameters ({Kn}, {Kt}, {gamma_n}, {gamma_t}, {xmu},
and {dampflag}) have the same meaning as those specified with the
"pair_style granular"_pair_gran.html force fields. This means a NULL
can be used for either Kt or gamma_t as described on that page. If a
NULL is used for Kt, then a default value is used where Kt = 2/7 Kn.
If a NULL is used for gamma_t, then a default value is used where
gamma_t = 1/2 gamma_n.
can be used for either {Kt} or {gamma_t} as described on that page.
If a NULL is used for {Kt}, then a default value is used where {Kt} =
2/7 {Kn}. If a NULL is used for {gamma_t}, then a default value is
used where {gamma_t} = 1/2 {gamma_n}.
The nature of the wall/particle interactions are determined by which
pair_style is used in your input script: {hooke}, {hooke/history}, or
@ -65,9 +79,9 @@ particles touching it is the same as the corresponding equation on the
the two particles going to infinite radius and mass (flat wall).
I.e. delta = radius - r = overlap of particle with wall, m_eff = mass
of particle, and sqrt(RiRj/Ri+Rj) becomes sqrt(radius of particle).
The units for Kn, Kt, gamma_n, and gamma_t are as described on that
doc page. The meaning of xmu and dampflag are also as described on
that page. Note that you can choose different values for these 6
The units for {Kn}, {Kt}, {gamma_n}, and {gamma_t} are as described on
that doc page. The meaning of xmu and dampflag are also as described
on that page. Note that you can choose different values for these 6
wall/particle coefficients than for particle/particle interactions, if
you wish your wall to interact differently with the particles, e.g. if
the wall is a different material.
@ -86,44 +100,211 @@ common case of a monodisperse system with particles of diameter 1, Kn,
Kt, gamma_n, and gamma_s should be set sqrt(2.0) larger than they were
previously.
The {wallstyle} can be planar or cylindrical. The 3 planar options
specify a pair of walls in a dimension. Wall positions are given by
{lo} and {hi}. Either of the values can be specified as NULL if a
single wall is desired. For a {zcylinder} wallstyle, the cylinder's
axis is at x = y = 0.0, and the radius of the cylinder is specified.
:line
Optionally, the wall can be moving, if the {wiggle} or {shear}
keywords are appended. Both keywords cannot be used together.
One or more wall {styles} can be specified. The {xlo}, {xhi}, {ylo},
{yhi}, {zlo}, {zhi} styles are planar faces that push particles back
into the box from one of their sides. E.g. the {xlo} wall should be
positioned to the left of all particles in the x dimension, so that it
pushes particles to the right, and conversely for the {xhi} wall. The
{zcylinder} style is a cylindrical shell with its axis along the
z-axis, centered at x = y = 0.0. The interior surface of the cylinder
pushes particles towards the x = y = 0.0 center axis. The {zcylinder}
style cannot be specified with any of the {xlo}, {xhi}, {ylo}, {yhi}
styles, but if can be with the {zlo} or {zhi} styles.
For the {wiggle} keyword, the wall oscillates sinusoidally, similar to
the oscillations of particles which can be specified by the
"fix_move"_fix_move.html command. This is useful in packing
simulations of granular particles. The arguments to the {wiggle}
keyword specify a dimension for the motion, as well as it's
{amplitude} and {period}. Note that if the dimension is in the plane
of the wall, this is effectively a shearing motion. If the dimension
is perpendicular to the wall, it is more of a shaking motion. A
{zcylinder} wall can only be wiggled in the z dimension.
:line
Each timestep, the position of a wiggled wall in the appropriate {dim}
is set according to this equation:
For the planer wall styles, {coord} and {vwall} arguments are
specified. These are the position and normal velocity of the wall. A
positive velocity means the wall is moving in the positive direction
in the normal dimension, e.g. +x for a {xlo} or {xhi} wall. Either or
both of the {coord} and {vwall} arguments can be specified as a
constant value or a variable. Note that the force exerted by a wall
on granular particles depends on the velocity of the wall, in both the
normal and tangential directions, so it is important to set {vwall}
consistent with the {coord} argument.
position = coord + A - A cos (omega * delta) :pre
If a numeric constant is specified for {coord} then the wall is placed
at that position in the appropriate dimension (x, y, or z) and will
never move. Likewise if a constant is specified for {vwall}, then the
normal velocity of the wall is set to that value and will never
change.
where {coord} is the specified initial position of the wall, {A} is
the {amplitude}, {omega} is 2 PI / {period}, and {delta} is the time
elapsed since the fix was specified. The velocity of the wall is set
to the derivative of this expression.
If {coord} or {vwall} is a variable, it should be specified as v_name,
where name is an "equal-style variable"_variable.html name. In this
case the variable is evaluated each timestep and the result becomes
the current position or normal velocity of the wall. Equal-style
variables can specify formulas with various mathematical functions,
and include "thermo_style"_thermo_style.html command keywords for the
simulation box parameters and timestep and elapsed time. Thus it is
easy to specify a time-dependent wall position and velocity.
For the {shear} keyword, the wall moves continuously in the specified
dimension with velocity {vshear}. The dimension must be tangential to
walls with a planar {wallstyle}, e.g. in the {y} or {z} directions for
an {xplane} wall. For {zcylinder} walls, a dimension of {z} means the
cylinder is moving in the z-direction along it's axis. A dimension of
{x} or {y} means the cylinder is spinning around the z-axis, either in
the clockwise direction for {vshear} > 0 or counter-clockwise for
{vshear} < 0. In this case, {vshear} is the tangential velocity of
the wall at whatever {radius} has been defined.
If {coord} is specified as a constant, then {vwall} must be specified
as 0.0. If {coord} is specified as a variable, then {vwall} must be a
non-zero constant or a variable. If {vwall} is specified as a
non-zero constant or variable and {coord} as a constant, then {coord}
is treated as the initial position of the wall, and the wall position
is updated each timestep by dt*v_current, where dt = the timestep, and
v_current = the current normal velocity.
:line
For the {zcylinder} wall style, {rad} and {vrad} arguments are
specified. These are the radius and radial velocity of the cylinder.
A positive velocity means the radius is growing. Either or both of
the {rad} and {vrad} arguments can be specified as a constant value or
a variable. Note that the force exerted by the wall of the cylinder
on granular particles depends on the velocity of the wall, in both the
normal (radial) and tangential directions, so it is important to set
{vrad} consistent with the {rad} argument.
If a numeric constant is specified for {rad} then the cylinder will
have a fixed radius. Likewise if a constant is specified for {vrad},
then the radial velocity of the cylinder is set to that value and will
never change.
If {rad} or {vrad} is a variable, it should be specified as
v_name, where name is an "equal-style variable"_variable.html name.
In this case the variable is evaluated each timestep and the result
becomes the current radius or radial velocity of the cylinder.
Equal-style variables can specify formulas with various mathematical
functions, and include "thermo_style"_thermo_style.html command
keywords for the simulation box parameters and timestep and elapsed
time. Thus it is easy to specify a time-dependent cylinder radius and
velocity.
If {rad} is specified as a constant, then {vrad} must be specified as
0.0. If {rad} is specified as a variable, then {vrad} must be a
non-zero constant or a variable. If {vrad} is specified as a non-zero
constant or variable and {rad} as a constant, then {rad} is treated as
the initial radius of the wall, and the radius is updated each
timestep by dt*v_current, where dt = the timestep, and v_current = the
current radial velocity.
:line
Here are examples of variable definitions that move the wall position
in a time-dependent fashion using equal-style
"variables"_variable.html. They also specify the correct normal
velocity of the wall based on the time derivative of the position.
variable ramp equal ramp(0,10)
variable vnorm equal 10/(10000*dt) # 10000 step run
fix 1 all wall/gran ... xlo v_ramp v_vnorm :pre
variable linear equal vdisplace(0,20)
fix 1 all wall/gran ... xlo v_linear 20 :pre
variable omega equal 2*PI/3.0
variable wiggle equal swiggle(0.0,5.0,3.0)
variable vwiggle equal "5.0 * v_omega * cos(v_omega*(timestep-startstep)*dt)"
fix 1 all wall/gran ... xlo v_wiggle v_vwiggle :pre
variable omega equal 2*PI/3.0
variable wiggle equal cwiggle(0.0,5.0,3.0)
variable vwiggle equal "5.0 * v_omega * sin(v_omega*(timestep-startstep)*dt)"
fix 1 all wall/gran ... xlo v_wiggle v_vwiggle :pre
The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.
The swiggle(c0,A,period) function causes the wall position to
oscillate sinusoidally according to this equation, where omega = 2 PI
/ period:
position = c0 + A sin(omega*delta) :pre
The cwiggle(c0,A,period) function causes the wall position to
oscillate sinusoidally according to this equation, which will have an
initial wall velocity of 0.0, and thus may impose a gentler
perturbation on the particles:
position = c0 + A (1 - cos(omega*delta)) :pre
:line
The optional keywords {shear} and {piston} are applied to all the
specified wall styles. If you need to apply different options to
different wall styles, then you should use multiple fix wall/gran
commands.
:line
The {shear} keyword allows specification of one or two tangential
velocities for planar or {zcylinder} walls. The {dim} value specifies
the velocity direction. {X}, {y}, and {z} can be used for planar
walls, but not for the direction normal to the wall. {Z} and {theta}
can be used for a {zcylinder} wall. {Theta} is the azimuthal angle in
the xy plane, i.e. a rotation of the cylinder about its vertical z
axis. Note that a positive theta velocity means increasing theta,
i.e. rotation in a counter-clockwise direction when looking down on
the xy plane from above.
{Vshear} is the magnitude of the shear velocity and can be specified
as a numeric constant or variable. The units of {vshear} are velocity
units for dim = {x}, {y}, or {z}. They are units of radians/time for
{dim} = {theta}.
If a numeric constant is used, then then the shear velocity will never
change. If {vshear} is a variable, it should be specified as v_name,
where name is an "equal-style variable"_variable.html name. In this
case the variable is evaluated each timestep and the result becomes
the current shear velocity. Equal-style variables can specify
formulas with various mathematical functions, and include
"thermo_style"_thermo_style.html command keywords for the simulation
box parameters and timestep and elapsed time. Thus it is easy to
specify a time-dependent shear velocity.
:line
The {piston} keyword allows specification of an external loading force
on the wall, which is opposed by granular particles pushing back
against the load. The wall position and normal velocity adjust
dynamically in response to these 2 opposing forces.
{Pload} is the magnitude of the loading force and can be specified as
a numeric constant or variable. This force must have a value less
than 0.0 which means that it is directed inward towards the particles.
Thus for a {xlo} wall, a negative values is a force in the +x
direction. For a {xhi} wall a negative values is a force in the -x
direction. For a {zcylinder} wall, a negative value is a force
towards the center z axis of the cylinder.
If a numeric constant is used for {pload}, then then the load force
will never change. If {pload} is a variable, it should be specified
as v_name, where name is an "equal-style variable"_variable.html name.
In this case the variable is evaluated each timestep and the result
becomes the current load force. Equal-style variables can specify
formulas with various mathematical functions, and include
"thermo_style"_thermo_style.html command keywords for the simulation
box parameters and timestep and elapsed time. Thus it is easy to
specify a time-dependent load force.
When the {piston} keyword is used, the {coord} and {vwall} arguemnts
for each wall style (or {rad} and {vrad} arguments for a {zcylinder}
style) must be numeric constants and are treated as initial values of
the position/radius and velocity/radial-velocity. The initial values
are updated every timestep by integrating these equations in a
velocity-Verlet fashion:
vwall_new = vwall + dt * (Fload + Fparticles) / pmass
xwall_new = xwall + dt * vwall_new :pre
Fload and Fparticles are the force on the wall due to the external
load and interactions with particles respectively. Fparticles is
always a positive value, representing particles pushing outward on the
wall (-x direction for a {xlo} wall, +x direction for a {xhi} wall,
radially outward for a {zylinder} wall). Thus Fload and Fparticles
will always have opposite signs. {Pmass} is the mass of the wall, as
specified with the {piston} keyword. Xwall and Vwall are the wall
position (or radius) and normal velocity (or radial velocity) on the
previous timestep. Xwall_new and vwall_new are the updated values.
:line
[Restart, fix_modify, output, run start/stop, minimize info:]
@ -135,10 +316,31 @@ info on how to re-specify a fix in an input script that reads a
restart file, so that the operation of the fix continues in an
uninterrupted fashion.
The fix does not write any information about the walls (e,g, position
or velocity) to the restart file. It is up to you to insure that fix
wall/gran commands you re-specify in a restart input script are
consistent with the previous simulation.
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
fix.
This fix computes a global vector of values, which can be accessed by
various "output commands"_Section_howto.html#howto_15. The length of
the vector is 4*Nstyle, where Nstyle is the number of styles
specified.
The 4 values (per style) are as follows:
(1) position (or radius) of wall (distance units)
(2) normal (or radial) velocity of wall (velocity or radians/time units)
(3) positive force on wall due to particles (force units)
(4) negative force on wall due to external load (force units) :pre
The sign conventions for these values are as described above. The 4th
value will be 0.0 if the {piston} keyword is not used. The vector
values calculated by this fix are "extensive".
No parameter of this fix can be used with the {start/stop} keywords of
the "run"_run.html command. This fix is not invoked during "energy
minimization"_minimize.html.
@ -154,4 +356,6 @@ Any dimension (xyz) that has a granular wall must be non-periodic.
"fix_move"_fix_move.html, "pair_style granular"_pair_gran.html
[Default:] none
[Default:]
The default shear velocities are 0.0.

2
doc/fix_wall_reflect.html
View File

@ -118,7 +118,7 @@ fix 1 all wall/reflect xlo v_wiggle
fix 1 all wall/reflect xlo v_wiggle
</PRE>
<P>The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.
</P>

2
doc/fix_wall_reflect.txt
View File

@ -107,7 +107,7 @@ variable wiggle equal cwiggle(0.0,5.0,3.0)
fix 1 all wall/reflect xlo v_wiggle :pre
The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The vdisplace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.

2
doc/fix_wall_srd.html
View File

@ -151,7 +151,7 @@ fix 1 all wall/srd xlo v_wiggle
fix 1 all wall/srd xlo v_wiggle
</PRE>
<P>The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The displace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.
</P>

2
doc/fix_wall_srd.txt
View File

@ -141,7 +141,7 @@ variable wiggle equal cwiggle(0.0,5.0,3.0)
fix 1 all wall/srd xlo v_wiggle :pre
The ramp(lo,hi) function adjusts the wall position linearly from lo to
hi over the course of a run. The linear(c0,velocity) function does
hi over the course of a run. The displace(c0,velocity) function does
something similar using the equation position = c0 + velocity*delta,
where delta is the elapsed time.

12
doc/improper_coeff.html
View File

@ -67,7 +67,12 @@ page for details.
<P>Here is an alphabetic list of improper styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> command:
specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> command.
</P>
<P>Note that there are also additional improper styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the improper section of
<A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<UL><LI><A HREF = "improper_none.html">improper_style none</A> - turn off improper interactions
<LI><A HREF = "improper_hybrid.html">improper_style hybrid</A> - define multiple styles of improper interactions
@ -77,11 +82,6 @@ specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> c
<LI><A HREF = "improper_harmonic.html">improper_style harmonic</A> - harmonic improper
<LI><A HREF = "improper_umbrella.html">improper_style umbrella</A> - DREIDING improper
</UL>
<P>There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

12
doc/improper_coeff.txt
View File

@ -64,7 +64,12 @@ page for details.
Here is an alphabetic list of improper styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "improper_coeff"_improper_coeff.html command:
specified by the associated "improper_coeff"_improper_coeff.html command.
Note that there are also additional improper styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the improper section of
"this page"_Section_commands.html#cmd_5.
"improper_style none"_improper_none.html - turn off improper interactions
"improper_style hybrid"_improper_hybrid.html - define multiple styles of improper interactions :ul
@ -74,11 +79,6 @@ specified by the associated "improper_coeff"_improper_coeff.html command:
"improper_style harmonic"_improper_harmonic.html - harmonic improper
"improper_style umbrella"_improper_umbrella.html - DREIDING improper :ul
There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

17
doc/improper_style.html
View File

@ -57,9 +57,15 @@ exist between a group of 4 bonded atoms.
</P>
<HR>
<P>Here is an alphabetic list of improper styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> command:
<P>Here is an alphabetic list of improper styles defined in LAMMPS.
Click on the style to display the formula it computes and coefficients
specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A>
command.
</P>
<P>There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<UL><LI><A HREF = "improper_none.html">improper_style none</A> - turn off improper interactions
<LI><A HREF = "improper_hybrid.html">improper_style hybrid</A> - define multiple styles of improper interactions
@ -69,11 +75,6 @@ specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> c
<LI><A HREF = "improper_harmonic.html">improper_style harmonic</A> - harmonic improper
<LI><A HREF = "improper_umbrella.html">improper_style umbrella</A> - DREIDING improper
</UL>
<P>There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

17
doc/improper_style.txt
View File

@ -54,9 +54,15 @@ exist between a group of 4 bonded atoms.
:line
Here is an alphabetic list of improper styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated "improper_coeff"_improper_coeff.html command:
Here is an alphabetic list of improper styles defined in LAMMPS.
Click on the style to display the formula it computes and coefficients
specified by the associated "improper_coeff"_improper_coeff.html
command.
There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of "this
page"_Section_commands.html#cmd_5.
"improper_style none"_improper_none.html - turn off improper interactions
"improper_style hybrid"_improper_hybrid.html - define multiple styles of improper interactions :ul
@ -66,11 +72,6 @@ specified by the associated "improper_coeff"_improper_coeff.html command:
"improper_style harmonic"_improper_harmonic.html - harmonic improper
"improper_style umbrella"_improper_umbrella.html - DREIDING improper :ul
There are also additional improper styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the improper section of "this
page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

22
doc/pair_coeff.html
View File

@ -82,7 +82,17 @@ the doc page for the potential.
<P>Here is an alphabetic list of pair styles defined in LAMMPS. Click on
the style to display the formula it computes, arguments specified in
the pair_style command, and coefficients specified by the associated
<A HREF = "pair_coeff.html">pair_coeff</A> command:
<A HREF = "pair_coeff.html">pair_coeff</A> command.
</P>
<P>Note that there are also additional pair styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the pair section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<P>There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of <A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<UL><LI><A HREF = "pair_hybrid.html">pair_style hybrid</A> - multiple styles of pairwise interactions
<LI><A HREF = "pair_hybrid.html">pair_style hybrid/overlay</A> - multiple styles of superposed pairwise interactions
@ -156,16 +166,6 @@ the pair_style command, and coefficients specified by the associated
<LI><A HREF = "pair_yukawa.html">pair_style yukawa</A> - Yukawa potential
<LI><A HREF = "pair_yukawa_colloid.html">pair_style yukawa/colloid</A> - screened Yukawa potential for finite-size particles
</UL>
<P>There are also additional pair styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the pair section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<P>There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of <A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

22
doc/pair_coeff.txt
View File

@ -79,7 +79,17 @@ the doc page for the potential.
Here is an alphabetic list of pair styles defined in LAMMPS. Click on
the style to display the formula it computes, arguments specified in
the pair_style command, and coefficients specified by the associated
"pair_coeff"_pair_coeff.html command:
"pair_coeff"_pair_coeff.html command.
Note that there are also additional pair styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the pair section of "this
page"_Section_commands.html#cmd_5.
There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of "this page"_Section_commands.html#cmd_5.
"pair_style hybrid"_pair_hybrid.html - multiple styles of pairwise interactions
"pair_style hybrid/overlay"_pair_hybrid.html - multiple styles of superposed pairwise interactions :ul
@ -153,16 +163,6 @@ the pair_style command, and coefficients specified by the associated
"pair_style yukawa"_pair_yukawa.html - Yukawa potential
"pair_style yukawa/colloid"_pair_yukawa_colloid.html - screened Yukawa potential for finite-size particles :ul
There are also additional pair styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the pair section of "this
page"_Section_commands.html#cmd_5.
There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of "this page"_Section_commands.html#cmd_5.
:line
[Restrictions:]

22
doc/pair_style.html
View File

@ -83,7 +83,17 @@ previously specified pair_coeff values.
<P>Here is an alphabetic list of pair styles defined in LAMMPS. Click on
the style to display the formula it computes, arguments specified in
the pair_style command, and coefficients specified by the associated
<A HREF = "pair_coeff.html">pair_coeff</A> command:
<A HREF = "pair_coeff.html">pair_coeff</A> command.
</P>
<P>Note that there are also additional pair styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the pair section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<P>There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of <A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<UL><LI><A HREF = "pair_none.html">pair_style none</A> - turn off pairwise interactions
<LI><A HREF = "pair_hybrid.html">pair_style hybrid</A> - multiple styles of pairwise interactions
@ -158,16 +168,6 @@ the pair_style command, and coefficients specified by the associated
<LI><A HREF = "pair_yukawa.html">pair_style yukawa</A> - Yukawa potential
<LI><A HREF = "pair_yukawa_colloid.html">pair_style yukawa/colloid</A> - screened Yukawa potential for finite-size particles
</UL>
<P>There are also additional pair styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the pair section of <A HREF = "Section_commands.html#cmd_5">this
page</A>.
</P>
<P>There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of <A HREF = "Section_commands.html#cmd_5">this page</A>.
</P>
<HR>
<P><B>Restrictions:</B>

22
doc/pair_style.txt
View File

@ -80,7 +80,17 @@ previously specified pair_coeff values.
Here is an alphabetic list of pair styles defined in LAMMPS. Click on
the style to display the formula it computes, arguments specified in
the pair_style command, and coefficients specified by the associated
"pair_coeff"_pair_coeff.html command:
"pair_coeff"_pair_coeff.html command.
Note that there are also additional pair styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the pair section of "this
page"_Section_commands.html#cmd_5.
There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of "this page"_Section_commands.html#cmd_5.
"pair_style none"_pair_none.html - turn off pairwise interactions
"pair_style hybrid"_pair_hybrid.html - multiple styles of pairwise interactions
@ -155,16 +165,6 @@ the pair_style command, and coefficients specified by the associated
"pair_style yukawa"_pair_yukawa.html - Yukawa potential
"pair_style yukawa/colloid"_pair_yukawa_colloid.html - screened Yukawa potential for finite-size particles :ul
There are also additional pair styles submitted by users which are
included in the LAMMPS distribution. The list of these with links to
the individual styles are given in the pair section of "this
page"_Section_commands.html#cmd_5.
There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs and GPUs. The list
of these with links to the individual styles are given in the pair
section of "this page"_Section_commands.html#cmd_5.
:line
[Restrictions:]