Unverified Commit 30929d95 authored by Axel Kohlmeyer's avatar Axel Kohlmeyer Committed by GitHub
Browse files

Merge pull request #1342 from dsbolin/gran_mods 

New generalized granular pair style added
parents 93f53144 ab12a7c9

doc/src/Commands_fix.txt

+1 −1
Original line number Diff line number Diff line
@@ -224,7 +224,7 @@ OPT. 
"wall/body/polyhedron"_fix_wall_body_polyhedron.html,

"wall/colloid"_fix_wall.html,

"wall/ees"_fix_wall_ees.html,

"wall/gran (o)"_fix_wall_gran.html,

"wall/gran"_fix_wall_gran.html,

"wall/gran/region"_fix_wall_gran_region.html,

"wall/harmonic"_fix_wall.html,

"wall/lj1043"_fix_wall.html,

doc/src/fix_wall_gran.txt

+47 −54
Original line number Diff line number Diff line
@@ -7,22 +7,24 @@ 
:line



fix wall/gran command :h3

fix wall/gran/omp command :h3



[Syntax:]



fix ID group-ID wall/gran fstyle Kn Kt gamma_n gamma_t xmu dampflag wallstyle args keyword values ... :pre

fix ID group-ID wall/gran fstyle fstyle_params wallstyle 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

fstyle = style of force interactions between particles and wall :l

  possible choices: hooke, hooke/history, hertz/history :pre

Kn = elastic constant for normal particle repulsion (force/distance units or pressure units - see discussion below) :l

Kt = elastic constant for tangential contact (force/distance units or pressure units - see discussion below) :l

gamma_n = damping coefficient for collisions in normal direction (1/time units or 1/time-distance units - see discussion below) :l

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 value between 0.0 and 1.0e4) :l

dampflag = 0 or 1 if tangential damping force is excluded or included :l

  possible choices: hooke, hooke/history, hertz/history, granular :pre

fstyle_params = parameters associated with force interaction style :l

  For {hooke}, {hooke/history}, and {hertz/history}, {fstyle_params} are: 

	Kn = elastic constant for normal particle repulsion (force/distance units or pressure units - see discussion below) 

	Kt = elastic constant for tangential contact (force/distance units or pressure units - see discussion below) 

	gamma_n = damping coefficient for collisions in normal direction (1/time units or 1/time-distance units - see discussion below) 

	gamma_t = damping coefficient for collisions in tangential direction (1/time units or 1/time-distance units - see discussion below)  

	xmu = static yield criterion (unitless value between 0.0 and 1.0e4) 

	dampflag = 0 or 1 if tangential damping force is excluded or included :pre

  For {granular}, {fstyle_params} are set using the same syntax as for the {pair_coeff} command of "pair_style granular"_pair_granular.html :pre

wallstyle = {xplane} or {yplane} or {zplane} or {zcylinder} :l

args = list of arguments for a particular style :l

  {xplane} or {yplane} or {zplane} args = lo hi
@@ -44,7 +46,10 @@ keyword = {wiggle} or {shear} :l 


fix 1 all wall/gran hooke  200000.0 NULL 50.0 NULL 0.5 0 xplane -10.0 10.0

fix 1 all wall/gran hooke/history 200000.0 NULL 50.0 NULL 0.5 0 zplane 0.0 NULL

fix 2 all wall/gran hooke 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 wiggle z 3.0 2.0 :pre

fix 2 all wall/gran hooke 100000.0 20000.0 50.0 30.0 0.5 1 zcylinder 15.0 wiggle z 3.0 2.0 

fix 3 all wall/gran granular hooke 1000.0 50.0 tangential linear_nohistory 1.0 0.4 zplane 0.0 NULL

fix 4 all wall/gran granular jkr 1000.0 50.0 0.3 5.0 tangential mindlin 800.0 1.0 0.5 rolling sds 500.0 200.0 0.5 twisting marshall zcylinder 15.0 wiggle z 3.0 2.0

fix 5 all wall/gran granular dmt 1000.0 50.0 0.3 10.0 tangential mindlin 800.0 0.5 0.1 roll sds 500.0 200.0 0.1 twisting marshall zplane 0.0 NULL :pre



[Description:]
@@ -54,31 +59,40 @@ close enough to touch it. 


The nature of the wall/particle interactions are determined by the

{fstyle} setting.  It can be any of the styles defined by the

"pair_style granular"_pair_gran.html commands.  Currently this is

{hooke}, {hooke/history}, or {hertz/history}.  The equation for the

force between the wall and particles touching it is the same as the

corresponding equation on the "pair_style granular"_pair_gran.html doc

page, in the limit of one of the two particles going to infinite

radius and mass (flat wall).  Specifically, delta = radius - r =

overlap of particle with wall, m_eff = mass of particle, and the

effective radius of contact = RiRj/Ri+Rj is just the radius of the

particle.

"pair_style gran/*"_pair_gran.html or the more general "pair_style

granular"_pair_granular.html" commands.  Currently the options are

{hooke}, {hooke/history}, or {hertz/history} for the former, and

{granular} with all the possible options of the associated

{pair_coeff} command for the latter.  The equation for the force

between the wall and particles touching it is the same as the

corresponding equation on the "pair_style gran/*"_pair_gran.html and

"pair_style_granular"_pair_granular.html doc pages, in the limit of

one of the two particles going to infinite radius and mass (flat

wall).  Specifically, delta = radius - r = overlap of particle with

wall, m_eff = mass of particle, and the effective radius of contact =

RiRj/Ri+Rj is set to the radius of the particle.



The parameters {Kn}, {Kt}, {gamma_n}, {gamma_t}, {xmu} and {dampflag}

have the same meaning and units as those specified with the

"pair_style granular"_pair_gran.html commands.  This means a NULL can

be used for either {Kt} or {gamma_t} as described on that page.  If a

"pair_style gran/*"_pair_gran.html commands.  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}.



All the model choices for cohesion, tangential friction, rolling

friction and twisting friction supported by the "pair_style

granular"_pair_granular.html through its {pair_coeff} command are also

supported for walls. These are discussed in greater detail on the doc

page for "pair_style granular"_pair_granular.html.



Note that you can choose a different force styles and/or different

values for the 6 wall/particle coefficients than for particle/particle

values for the wall/particle coefficients than for particle/particle

interactions.  E.g. if you wish to model the wall as a different

material.



NOTE: As discussed on the doc page for "pair_style

granular"_pair_gran.html, versions of LAMMPS before 9Jan09 used a

gran/*"_pair_gran.html, versions of LAMMPS before 9Jan09 used a

different equation for Hertzian interactions.  This means Hertizian

wall/particle interactions have also changed.  They now include a

sqrt(radius) term which was not present before.  Also the previous
@@ -108,14 +122,14 @@ Optionally, the wall can be moving, if the {wiggle} or {shear} 
keywords are appended.  Both keywords cannot be used together.



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.

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.



Each timestep, the position of a wiggled wall in the appropriate {dim}

is set according to this equation:
@@ -137,28 +151,6 @@ 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.



:line



Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are

functionally the same as the corresponding style without the suffix.

They have been optimized to run faster, depending on your available

hardware, as discussed on the "Speed packages"_Speed_packages.html doc

page.  The accelerated styles take the same arguments and should

produce the same results, except for round-off and precision issues.



These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,

USER-OMP and OPT packages, respectively.  They are only enabled if

LAMMPS was built with those packages.  See the "Build

package"_Build_package.html doc page for more info.



You can specify the accelerated styles explicitly in your input script

by including their suffix, or you can use the "-suffix command-line

switch"_Run_options.html when you invoke LAMMPS, or you can use the

"suffix"_suffix.html command in your input script.



See the "Speed packages"_Speed_packages.html doc page for more

instructions on how to use the accelerated styles effectively.



[Restart, fix_modify, output, run start/stop, minimize info:]



This fix writes the shear friction state of atoms interacting with the
@@ -188,6 +180,7 @@ Any dimension (xyz) that has a granular wall must be non-periodic. 


"fix move"_fix_move.html,

"fix wall/gran/region"_fix_wall_gran_region.html,

"pair_style granular"_pair_gran.html

"pair_style gran/*"_pair_gran.html

"pair_style granular"_pair_granular.html



[Default:] none

doc/src/fix_wall_gran_region.txt

+46 −30
Original line number Diff line number Diff line
@@ -10,24 +10,30 @@ fix wall/gran/region command :h3 


[Syntax:]



fix ID group-ID wall/gran/region fstyle Kn Kt gamma_n gamma_t xmu dampflag wallstyle regionID :pre

fix ID group-ID wall/gran/region fstyle fstyle_params wallstyle regionID :pre



ID, group-ID are documented in "fix"_fix.html command :ulb,l

wall/region = style name of this fix command :l

fstyle = style of force interactions between particles and wall :l

  possible choices: hooke, hooke/history, hertz/history :pre

Kn = elastic constant for normal particle repulsion (force/distance units or pressure units - see discussion below) :l

Kt = elastic constant for tangential contact (force/distance units or pressure units - see discussion below) :l

gamma_n = damping coefficient for collisions in normal direction (1/time units or 1/time-distance units - see discussion below) :l

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 value between 0.0 and 1.0e4) :l

dampflag = 0 or 1 if tangential damping force is excluded or included :l

  possible choices: hooke, hooke/history, hertz/history, granular :pre

fstyle_params = parameters associated with force interaction style :l

  For {hooke}, {hooke/history}, and {hertz/history}, {fstyle_params} are: 

	Kn = elastic constant for normal particle repulsion (force/distance units or pressure units - see discussion below) 

	Kt = elastic constant for tangential contact (force/distance units or pressure units - see discussion below) 

	gamma_n = damping coefficient for collisions in normal direction (1/time units or 1/time-distance units - see discussion below) 

	gamma_t = damping coefficient for collisions in tangential direction (1/time units or 1/time-distance units - see discussion below)  

	xmu = static yield criterion (unitless value between 0.0 and 1.0e4) 

	dampflag = 0 or 1 if tangential damping force is excluded or included :pre

  For {granular}, {fstyle_params} are set using the same syntax as for the {pair_coeff} command of "pair_style granular"_pair_granular.html :pre

wallstyle = region (see "fix wall/gran"_fix_wall_gran.html for options for other kinds of walls) :l

region-ID = region whose boundary will act as wall :l,ule



[Examples:]



fix wall all wall/gran/region hooke/history 1000.0 200.0 200.0 100.0 0.5 1 region myCone :pre

fix wall all wall/gran/region hooke/history 1000.0 200.0 200.0 100.0 0.5 1 region myCone 

fix 3 all wall/gran/region granular hooke 1000.0 50.0 tangential linear_nohistory 1.0 0.4 region myBox

fix 4 all wall/gran/region granular jkr 1000.0 50.0 tangential linear_history 800.0 1.0 0.5 rolling sds 500.0 200.0 0.5 twisting marshall region myCone

fix 5 all wall/gran/region granular dmt 1000.0 50.0 0.3 10.0 tangential linear_history 800.0 0.5 0.1 roll sds 500.0 200.0 0.1 twisting marshall region myCone :pre



[Description:]
@@ -42,8 +48,8 @@ Here are snapshots of example models using this command. 
Corresponding input scripts can be found in examples/granregion.

Click on the images to see a bigger picture.  Movies of these

simulations are "here on the Movies

page"_http://lammps.sandia.gov/movies.html#granregion of the

LAMMPS web site.

page"_http://lammps.sandia.gov/movies.html#granregion of the LAMMPS

web site.



:image(JPG/gran_funnel_small.jpg,JPG/gran_funnel.png)

:image(JPG/gran_mixer_small.jpg,JPG/gran_mixer.png)
@@ -123,12 +129,16 @@ to make the two faces differ by epsilon in their position. 


The nature of the wall/particle interactions are determined by the

{fstyle} setting.  It can be any of the styles defined by the

"pair_style granular"_pair_gran.html commands.  Currently this is

{hooke}, {hooke/history}, or {hertz/history}.  The equation for the

force between the wall and particles touching it is the same as the

corresponding equation on the "pair_style granular"_pair_gran.html doc

page, but the effective radius is calculated using the radius of the

particle and the radius of curvature of the wall at the contact point.

"pair_style gran/*"_pair_gran.html or the more general "pair_style

granular"_pair_granular.html" commands.  Currently the options are

{hooke}, {hooke/history}, or {hertz/history} for the former, and

{granular} with all the possible options of the associated

{pair_coeff} command for the latter.  The equation for the force

between the wall and particles touching it is the same as the

corresponding equation on the "pair_style gran/*"_pair_gran.html and

"pair_style_granular"_pair_granular.html doc pages, but the effective

radius is calculated using the radius of the particle and the radius

of curvature of the wall at the contact point.



Specifically, delta = radius - r = overlap of particle with wall,

m_eff = mass of particle, and RiRj/Ri+Rj is the effective radius, with
@@ -141,12 +151,18 @@ particle. 


The parameters {Kn}, {Kt}, {gamma_n}, {gamma_t}, {xmu} and {dampflag}

have the same meaning and units as those specified with the

"pair_style granular"_pair_gran.html commands.  This means a NULL can

be used for either {Kt} or {gamma_t} as described on that page.  If a

"pair_style gran/*"_pair_gran.html commands.  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}.



All the model choices for cohesion, tangential friction, rolling

friction and twisting friction supported by the "pair_style

granular"_pair_granular.html through its {pair_coeff} command are also

supported for walls. These are discussed in greater detail on the doc

page for "pair_style granular"_pair_granular.html.



Note that you can choose a different force styles and/or different

values for the 6 wall/particle coefficients than for particle/particle

interactions.  E.g. if you wish to model the wall as a different
@@ -154,9 +170,9 @@ material. 


[Restart, fix_modify, output, run start/stop, minimize info:]



Similar to "fix wall/gran"_fix_wall_gran.html command, this fix

writes the shear friction state of atoms interacting with the wall to

"binary restart files"_restart.html, so that a simulation can continue

Similar to "fix wall/gran"_fix_wall_gran.html command, this fix writes

the shear friction state of atoms interacting with the wall to "binary

restart files"_restart.html, so that a simulation can continue

correctly if granular potentials with shear "history" effects are

being used.  This fix also includes info about a moving region in the

restart file.  See the "read_restart"_read_restart.html command for
@@ -170,14 +186,14 @@ So you must re-define your region and if it is a moving region, define 
its motion attributes in a way that is consistent with the simulation

that wrote the restart file.  In particular, if you want to change the

region motion attributes (e.g. its velocity), then you should ensure

the position/orientation of the region at the initial restart

timestep is the same as it was on the timestep the restart file was

written.  If this is not possible, you may need to ignore info in the

restart file by defining a new fix wall/gran/region command in your

restart script, e.g. with a different fix ID.  Or if you want to keep

the shear history info but discard the region motion information, you

can use the same fix ID for fix wall/gran/region, but assign it a

region with a different region ID.

the position/orientation of the region at the initial restart timestep

is the same as it was on the timestep the restart file was written.

If this is not possible, you may need to ignore info in the restart

file by defining a new fix wall/gran/region command in your restart

script, e.g. with a different fix ID.  Or if you want to keep the

shear history info but discard the region motion information, you can

use the same fix ID for fix wall/gran/region, but assign it a region

with a different region ID.



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

doc/src/lammps.book

+1 −0
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@@ -580,6 +580,7 @@ pair_extep.html 
pair_gauss.html

pair_gayberne.html

pair_gran.html

pair_granular.html

pair_gromacs.html

pair_gw.html

pair_ilp_graphene_hbn.html

doc/src/pair_granular.txt

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