cosmetic reformatting of new GRANULAR files

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 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.

"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 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

"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.

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 wall/particle coefficients than for particle/particle

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:

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)

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 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.

"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

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

have the same meaning and units as those specified with the

"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

"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.

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

[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

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

  bigint time_origin;

  double kn,kt,gamman,gammat,xmu;

  //For granular

  //Model choices

  // for granular model choices

  int normal_model, damping_model;

  int tangential_model, roll_model, twist_model;

  int beyond_contact;

  //History flags

  // history flags

  int normal_history, tangential_history, roll_history, twist_history;

  //Indices of history entries

  // indices of history entries

  int normal_history_index;

  int tangential_history_index;

  int roll_history_index;

  int twist_history_index;

  //Material coefficients

  // material coefficients

  double Emod, poiss, Gmod;

  //Contact model coefficients

  // contact model coefficients

  double normal_coeffs[4];

  double tangential_coeffs[3];

  double roll_coeffs[3];

  double *mass_rigid;      // rigid mass for owned+ghost atoms

  int nmax;                // allocated size of mass_rigid

  // Store particle interactions

  // store particle interactions

  int store;

};