jianmu
/
lammps
forked from lijiext/lammps
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Merge pull request #2698 from jtclemm/gran_attractive 

New option for granular pairstyles and updates to granular walls
This commit is contained in:
Axel Kohlmeyer 2021-04-07 16:02:57 -04:00 committed by GitHub
parent 5bdf032035 ea8277ce87
commit 3c5424722e
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
16 changed files with 262 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
doc/src/fix_wall_gran.rst
View File

@ -29,6 +29,7 @@ Syntax
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
optional keyword = *limit_damping*, limit damping to prevent attractive interaction
.. parsed-literal::
@ -95,7 +96,8 @@ 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*
The parameters *Kn*\ , *Kt*\ , *gamma_n*, *gamma_t*, *xmu*, *dampflag*,
and the optional keyword *limit_damping*
have the same meaning and units as those specified with the
:doc:`pair_style gran/\* <pair_gran>` commands. This means a NULL can be
used for either *Kt* or *gamma_t* as described on that page. If a

3
doc/src/fix_wall_gran_region.rst
View File

@ -181,7 +181,8 @@ radius - r = overlap of particle with wall, m_eff = mass of particle,
and the effective radius of contact is just the radius of the
particle.
The parameters *Kn*\ , *Kt*\ , *gamma_n*, *gamma_t*, *xmu* and *dampflag*
The parameters *Kn*\ , *Kt*\ , *gamma_n*, *gamma_t*, *xmu*, *dampflag*,
and the optional keyword *limit_damping*
have the same meaning and units as those specified with the
:doc:`pair_style gran/\* <pair_gran>` commands. This means a NULL can be
used for either *Kt* or *gamma_t* as described on that page. If a

17
doc/src/pair_gran.rst
View File

@ -26,7 +26,7 @@ Syntax
.. code-block:: LAMMPS
pair_style style Kn Kt gamma_n gamma_t xmu dampflag
pair_style style Kn Kt gamma_n gamma_t xmu dampflag keyword
* style = *gran/hooke* or *gran/hooke/history* or *gran/hertz/history*
* Kn = elastic constant for normal particle repulsion (force/distance units or pressure units - see discussion below)
@ -36,6 +36,13 @@ Syntax
* xmu = static yield criterion (unitless value between 0.0 and 1.0e4)
* dampflag = 0 or 1 if tangential damping force is excluded or included
* keyword = *limit_damping*
.. parsed-literal::
*limit_damping* value = none
limit damping to prevent attractive interaction
.. note::
Versions of LAMMPS before 9Jan09 had different style names for
@ -54,6 +61,8 @@ Examples
pair_style gran/hooke/history 200000.0 NULL 50.0 NULL 0.5 1
pair_style gran/hooke 200000.0 70000.0 50.0 30.0 0.5 0
pair_style gran/hooke 200000.0 70000.0 50.0 30.0 0.5 0 limit_damping
Description
"""""""""""
@ -208,6 +217,12 @@ potential is used as a sub-style of :doc:`pair_style hybrid <pair_hybrid>`, then
pair_coeff command to determine which atoms interact via a granular
potential.
If two particles are moving away from each other while in contact, there
is a possibility that the particles could experience an effective attractive
force due to damping. If the *limit_damping* keyword is used, this option
will zero out the normal component of the force if there is an effective
attractive force.
----------
.. include:: accel_styles.rst

16
doc/src/pair_granular.rst
View File

@ -24,7 +24,7 @@ Examples
pair_coeff * * hooke 1000.0 50.0 tangential linear_history 500.0 1.0 0.4 damping mass_velocity
pair_style granular
pair_coeff * * hertz 1000.0 50.0 tangential mindlin 1000.0 1.0 0.4
pair_coeff * * hertz 1000.0 50.0 tangential mindlin 1000.0 1.0 0.4 limit_damping
pair_style granular
pair_coeff * * hertz/material 1e8 0.3 0.3 tangential mindlin_rescale NULL 1.0 0.4 damping tsuji
@ -623,6 +623,14 @@ Finally, the twisting torque on each particle is given by:
----------
If two particles are moving away from each other while in contact, there
is a possibility that the particles could experience an effective attractive
force due to damping. If the optional *limit_damping* keyword is used, this option
will zero out the normal component of the force if there is an effective
attractive force. This keyword cannot be used with the JKR or DMT models.
----------
The *granular* pair style can reproduce the behavior of the
*pair gran/\** styles with the appropriate settings (some very
minor differences can be expected due to corrections in
@ -657,6 +665,12 @@ then LAMMPS will use that cutoff for the specified atom type
combination, and automatically set pairwise cutoffs for the remaining
atom types.
If two particles are moving away from each other while in contact, there
is a possibility that the particles could experience an effective attractive
force due to damping. If the *limit_damping* keyword is used, this option
will zero out the normal component of the force if there is an effective
attractive force. This keyword cannot be used with the JKR or DMT models.
----------
.. include:: accel_styles.rst

166
src/GRANULAR/fix_wall_gran.cpp
View File

@ -54,7 +54,8 @@ enum {XPLANE=0,YPLANE=1,ZPLANE=2,ZCYLINDER,REGION};
enum {NONE,CONSTANT,EQUAL};
enum {DAMPING_NONE, VELOCITY, MASS_VELOCITY, VISCOELASTIC, TSUJI};
enum {TANGENTIAL_NONE, TANGENTIAL_NOHISTORY, TANGENTIAL_HISTORY,
TANGENTIAL_MINDLIN, TANGENTIAL_MINDLIN_RESCALE};
TANGENTIAL_MINDLIN, TANGENTIAL_MINDLIN_RESCALE,
TANGENTIAL_MINDLIN_FORCE, TANGENTIAL_MINDLIN_RESCALE_FORCE};
enum {TWIST_NONE, TWIST_SDS, TWIST_MARSHALL};
enum {ROLL_NONE, ROLL_SDS};
@ -70,6 +71,7 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
error->all(FLERR,"Fix wall/gran requires atom style sphere");
create_attribute = 1;
limit_damping = 0;
// set interaction style
// disable bonded/history option for now
@ -90,7 +92,6 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
// wall/particle coefficients
int iarg;
if (pairstyle != GRANULAR) {
size_history = 3;
if (narg < 11) error->all(FLERR,"Illegal fix wall/gran command");
@ -118,6 +119,12 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
kt /= force->nktv2p;
}
iarg = 10;
if (strcmp(arg[iarg],"limit_damping") == 0) {
limit_damping = 1;
iarg += 1;
}
} else {
iarg = 4;
damping_model = VISCOELASTIC;
@ -211,7 +218,9 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
iarg += 4;
} else if ((strcmp(arg[iarg+1], "linear_history") == 0) ||
(strcmp(arg[iarg+1], "mindlin") == 0) ||
(strcmp(arg[iarg+1], "mindlin_rescale") == 0)) {
(strcmp(arg[iarg+1], "mindlin_rescale") == 0) ||
(strcmp(arg[iarg+1], "mindlin/force") == 0) ||
(strcmp(arg[iarg+1], "mindlin_rescale/force") == 0)) {
if (iarg + 4 >= narg)
error->all(FLERR,"Illegal pair_coeff command, "
"not enough parameters provided for tangential model");
@ -221,8 +230,14 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
tangential_model = TANGENTIAL_MINDLIN;
else if (strcmp(arg[iarg+1], "mindlin_rescale") == 0)
tangential_model = TANGENTIAL_MINDLIN_RESCALE;
else if (strcmp(arg[iarg+1], "mindlin/force") == 0)
tangential_model = TANGENTIAL_MINDLIN_FORCE;
else if (strcmp(arg[iarg+1], "mindlin_rescale/force") == 0)
tangential_model = TANGENTIAL_MINDLIN_RESCALE_FORCE;
if ((tangential_model == TANGENTIAL_MINDLIN ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE) &&
tangential_model == TANGENTIAL_MINDLIN_RESCALE ||
tangential_model == TANGENTIAL_MINDLIN_FORCE ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE_FORCE) &&
(strcmp(arg[iarg+2], "NULL") == 0)) {
if (normal_model == NORMAL_HERTZ || normal_model == NORMAL_HOOKE) {
error->all(FLERR, "NULL setting for Mindlin tangential "
@ -293,13 +308,27 @@ FixWallGran::FixWallGran(LAMMPS *lmp, int narg, char **arg) :
strcmp(arg[iarg], "zcylinder") == 0 ||
strcmp(arg[iarg], "region") == 0) {
break;
} else if (strcmp(arg[iarg],"limit_damping") == 0) {
limit_damping = 1;
iarg += 1;
} else {
error->all(FLERR, "Illegal fix wall/gran command");
}
}
size_history = 3*tangential_history + 3*roll_history + twist_history;
//Unlike the pair style, the wall style does not have a 'touch'
//array. Hence, an additional entry in the history is used to
//determine if particles previously contacted for JKR cohesion purposes.
if (normal_model == JKR) size_history += 1;
if (tangential_model == TANGENTIAL_MINDLIN_RESCALE) size_history += 1;
if (tangential_model == TANGENTIAL_MINDLIN_RESCALE ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE_FORCE) size_history += 1;
if (limit_damping && normal_model == JKR)
error->all(FLERR,"Illegal pair_coeff command, "
"cannot limit damping with JRK model");
if (limit_damping && normal_model == DMT)
error->all(FLERR,"Illegal pair_coeff command, "
"Cannot limit damping with DMT model");
}
// wallstyle args
@ -475,6 +504,7 @@ void FixWallGran::init()
if (modify->fix[i]->rigid_flag) break;
if (i < modify->nfix) fix_rigid = modify->fix[i];
if(pairstyle == GRANULAR) {
tangential_history_index = 0;
if (roll_history) {
if (tangential_history) roll_history_index = 3;
@ -495,7 +525,8 @@ void FixWallGran::init()
roll_history_index += 1;
twist_history_index += 1;
}
if (tangential_model == TANGENTIAL_MINDLIN_RESCALE) {
if (tangential_model == TANGENTIAL_MINDLIN_RESCALE ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE_FORCE) {
roll_history_index += 1;
twist_history_index += 1;
}
@ -507,6 +538,7 @@ void FixWallGran::init()
4.8218*pow(cor,6);
}
}
}
/* ---------------------------------------------------------------------- */
@ -762,6 +794,7 @@ void FixWallGran::hooke(double rsq, double dx, double dy, double dz,
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radius-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -854,6 +887,7 @@ void FixWallGran::hooke_history(double rsq, double dx, double dy, double dz,
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radius-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -985,6 +1019,7 @@ void FixWallGran::hertz_history(double rsq, double dx, double dy, double dz,
if (rwall == 0.0) polyhertz = sqrt((radius-r)*radius);
else polyhertz = sqrt((radius-r)*radius*rwall/(rwall+radius));
ccel *= polyhertz;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -1103,7 +1138,8 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
double signtwist, magtwist, magtortwist, Mtcrit;
double tortwist1, tortwist2, tortwist3;
double shrmag,rsht;
double shrmag,rsht,prjmag;
bool frameupdate;
r = sqrt(rsq);
E = normal_coeffs[0];
@ -1178,11 +1214,18 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
Fdamp = -damp_normal_prefactor*vnnr;
Fntot = Fne + Fdamp;
if (limit_damping && (Fntot < 0.0)) Fntot = 0.0;
//****************************************
// tangential force, including history effects
//****************************************
// For linear, mindlin, mindlin_rescale:
// history = cumulative tangential displacement
//
// For mindlin/force, mindlin_rescale/force:
// history = cumulative tangential elastic force
// tangential component
vt1 = vr1 - vn1;
vt2 = vr2 - vn2;
@ -1224,69 +1267,115 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
int thist2 = thist1 + 1;
if (tangential_history) {
if (tangential_model == TANGENTIAL_MINDLIN) {
if (tangential_model == TANGENTIAL_MINDLIN ||
tangential_model == TANGENTIAL_MINDLIN_FORCE) {
k_tangential *= a;
}
else if (tangential_model == TANGENTIAL_MINDLIN_RESCALE) {
else if (tangential_model ==
TANGENTIAL_MINDLIN_RESCALE ||
tangential_model ==
TANGENTIAL_MINDLIN_RESCALE_FORCE){
k_tangential *= a;
if (a < history[3]) { //On unloading, rescale the shear displacements
// on unloading, rescale the shear displacements/force
if (a < history[thist2+1]) {
double factor = a/history[thist2+1];
history[thist0] *= factor;
history[thist1] *= factor;
history[thist2] *= factor;
}
}
shrmag = sqrt(history[thist0]*history[thist0] +
history[thist1]*history[thist1] +
history[thist2]*history[thist2]);
// rotate and update displacements.
// see e.g. eq. 17 of Luding, Gran. Matter 2008, v10,p235
if (history_update) {
rsht = history[thist0]*nx + history[thist1]*ny + history[thist2]*nz;
if (fabs(rsht) < EPSILON) rsht = 0;
if (rsht > 0) {
// if rhst == shrmag, contacting pair has rotated 90 deg in one step,
// in which case you deserve a crash!
scalefac = shrmag/(shrmag - rsht);
if (tangential_model == TANGENTIAL_MINDLIN_FORCE ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE_FORCE)
frameupdate = fabs(rsht) > EPSILON*Fscrit;
else
frameupdate = fabs(rsht)*k_tangential > EPSILON*Fscrit;
if (frameupdate) {
shrmag = sqrt(history[thist0]*history[thist0] +
history[thist1]*history[thist1] +
history[thist2]*history[thist2]);
// projection
history[thist0] -= rsht*nx;
history[thist1] -= rsht*ny;
history[thist2] -= rsht*nz;
// also rescale to preserve magnitude
prjmag = sqrt(history[thist0]*history[thist0] +
history[thist1]*history[thist1] + history[thist2]*history[thist2]);
if (prjmag > 0) scalefac = shrmag/prjmag;
else scalefac = 0;
history[thist0] *= scalefac;
history[thist1] *= scalefac;
history[thist2] *= scalefac;
}
// update history
if (tangential_model == TANGENTIAL_HISTORY ||
tangential_model == TANGENTIAL_MINDLIN ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE) {
history[thist0] += vtr1*dt;
history[thist1] += vtr2*dt;
history[thist2] += vtr3*dt;
} else{
// tangential force
// see e.g. eq. 18 of Thornton et al, Pow. Tech. 2013, v223,p30-46
history[thist0] -= k_tangential*vtr1*dt;
history[thist1] -= k_tangential*vtr2*dt;
history[thist2] -= k_tangential*vtr3*dt;
}
if (tangential_model == TANGENTIAL_MINDLIN_RESCALE ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE_FORCE)
history[thist2+1] = a;
}
// tangential forces = history + tangential velocity damping
if (tangential_model == TANGENTIAL_HISTORY ||
tangential_model == TANGENTIAL_MINDLIN ||
tangential_model == TANGENTIAL_MINDLIN_RESCALE) {
fs1 = -k_tangential*history[thist0] - damp_tangential*vtr1;
fs2 = -k_tangential*history[thist1] - damp_tangential*vtr2;
fs3 = -k_tangential*history[thist2] - damp_tangential*vtr3;
} else {
fs1 = history[thist0] - damp_tangential*vtr1;
fs2 = history[thist1] - damp_tangential*vtr2;
fs3 = history[thist2] - damp_tangential*vtr3;
}
// rescale frictional displacements and forces if needed
Fscrit = tangential_coeffs[2] * Fncrit;
fs = sqrt(fs1*fs1 + fs2*fs2 + fs3*fs3);
if (fs > Fscrit) {
shrmag = sqrt(history[thist0]*history[thist0] +
history[thist1]*history[thist1] +
history[thist2]*history[thist2]);
if (shrmag != 0.0) {
if (tangential_model == TANGENTIAL_HISTORY ||
tangential_model == TANGENTIAL_MINDLIN ||
tangential_model ==
TANGENTIAL_MINDLIN_RESCALE) {
history[thist0] = -1.0/k_tangential*(Fscrit*fs1/fs +
damp_tangential*vtr1);
history[thist1] = -1.0/k_tangential*(Fscrit*fs2/fs +
damp_tangential*vtr2);
history[thist2] = -1.0/k_tangential*(Fscrit*fs3/fs +
damp_tangential*vtr3);
} else {
history[thist0] = Fscrit*fs1/fs + damp_tangential*vtr1;
history[thist1] = Fscrit*fs2/fs + damp_tangential*vtr2;
history[thist2] = Fscrit*fs3/fs + damp_tangential*vtr3;
}
fs1 *= Fscrit/fs;
fs2 *= Fscrit/fs;
fs3 *= Fscrit/fs;
} else fs1 = fs2 = fs3 = 0.0;
}
} else { // classic pair gran/hooke (no history)
fs = meff*damp_tangential*vrel;
if (vrel != 0.0) Ft = MIN(Fne,fs) / vrel;
fs = damp_tangential*vrel;
if (vrel != 0.0) Ft = MIN(Fscrit,fs) / vrel;
else Ft = 0.0;
fs1 = -Ft*vtr1;
fs2 = -Ft*vtr2;
@ -1297,14 +1386,14 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
// rolling resistance
//****************************************
if (roll_model != ROLL_NONE || twist_model != NONE) {
if (roll_model != ROLL_NONE || twist_model != TWIST_NONE) {
relrot1 = omega[0];
relrot2 = omega[1];
relrot3 = omega[2];
}
if (roll_model != ROLL_NONE) {
// rolling velocity, see eq. 31 of Wang et al, Particuology v 23, p 49 (2015)
// rolling velocity,
// see eq. 31 of Wang et al, Particuology v 23, p 49 (2015)
// This is different from the Marshall papers,
// which use the Bagi/Kuhn formulation
// for rolling velocity (see Wang et al for why the latter is wrong)
@ -1316,21 +1405,29 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
int rhist1 = rhist0 + 1;
int rhist2 = rhist1 + 1;
// rolling displacement
k_roll = roll_coeffs[0];
damp_roll = roll_coeffs[1];
Frcrit = roll_coeffs[2] * Fncrit;
if (history_update) {
rolldotn = history[rhist0]*nx + history[rhist1]*ny + history[rhist2]*nz;
frameupdate = fabs(rolldotn)*k_roll > EPSILON*Frcrit;
if (frameupdate) { // rotate into tangential plane
rollmag = sqrt(history[rhist0]*history[rhist0] +
history[rhist1]*history[rhist1] +
history[rhist2]*history[rhist2]);
rolldotn = history[rhist0]*nx + history[rhist1]*ny + history[rhist2]*nz;
if (history_update) {
if (fabs(rolldotn) < EPSILON) rolldotn = 0;
if (rolldotn > 0) { // rotate into tangential plane
scalefac = rollmag/(rollmag - rolldotn);
// projection
history[rhist0] -= rolldotn*nx;
history[rhist1] -= rolldotn*ny;
history[rhist2] -= rolldotn*nz;
// also rescale to preserve magnitude
prjmag = sqrt(history[rhist0]*history[rhist0] +
history[rhist1]*history[rhist1] +
history[rhist2]*history[rhist2]);
if (prjmag > 0) scalefac = rollmag/prjmag;
else scalefac = 0;
history[rhist0] *= scalefac;
history[rhist1] *= scalefac;
history[rhist2] *= scalefac;
@ -1340,17 +1437,16 @@ void FixWallGran::granular(double rsq, double dx, double dy, double dz,
history[rhist2] += vrl3*dt;
}
k_roll = roll_coeffs[0];
damp_roll = roll_coeffs[1];
fr1 = -k_roll*history[rhist0] - damp_roll*vrl1;
fr2 = -k_roll*history[rhist1] - damp_roll*vrl2;
fr3 = -k_roll*history[rhist2] - damp_roll*vrl3;
// rescale frictional displacements and forces if needed
Frcrit = roll_coeffs[2] * Fncrit;
fr = sqrt(fr1*fr1 + fr2*fr2 + fr3*fr3);
if (fr > Frcrit) {
rollmag = sqrt(history[rhist0]*history[rhist0] +
history[rhist1]*history[rhist1] +
history[rhist2]*history[rhist2]);
if (rollmag != 0.0) {
history[rhist0] = -1.0/k_roll*(Frcrit*fr1/fr + damp_roll*vrl1);
history[rhist1] = -1.0/k_roll*(Frcrit*fr2/fr + damp_roll*vrl2);

1
src/GRANULAR/fix_wall_gran.h
View File

@ -73,6 +73,7 @@ class FixWallGran : public Fix {
// for granular model choices
int normal_model, damping_model;
int tangential_model, roll_model, twist_model;
int limit_damping;
// history flags
int normal_history, tangential_history, roll_history, twist_history;

10
src/GRANULAR/pair_gran_hertz_history.cpp
View File

@ -181,6 +181,7 @@ void PairGranHertzHistory::compute(int eflag, int vflag)
ccel = kn*(radsum-r)*rinv - damp;
polyhertz = sqrt((radsum-r)*radi*radj / radsum);
ccel *= polyhertz;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -277,7 +278,7 @@ void PairGranHertzHistory::compute(int eflag, int vflag)
void PairGranHertzHistory::settings(int narg, char **arg)
{
if (narg != 6) error->all(FLERR,"Illegal pair_style command");
if (narg != 6 && narg != 7) error->all(FLERR,"Illegal pair_style command");
kn = utils::numeric(FLERR,arg[0],false,lmp);
if (strcmp(arg[1],"NULL") == 0) kt = kn * 2.0/7.0;
@ -295,6 +296,12 @@ void PairGranHertzHistory::settings(int narg, char **arg)
xmu < 0.0 || xmu > 10000.0 || dampflag < 0 || dampflag > 1)
error->all(FLERR,"Illegal pair_style command");
limit_damping = 0;
if (narg == 7) {
if (strcmp(arg[6], "limit_damping") == 0) limit_damping = 1;
else error->all(FLERR,"Illegal pair_style command");
}
// convert Kn and Kt from pressure units to force/distance^2
kn /= force->nktv2p;
@ -388,6 +395,7 @@ double PairGranHertzHistory::single(int i, int j, int /*itype*/, int /*jtype*/,
ccel = kn*(radsum-r)*rinv - damp;
polyhertz = sqrt((radsum-r)*radi*radj / radsum);
ccel *= polyhertz;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

2
src/GRANULAR/pair_gran_hooke.cpp
View File

@ -158,6 +158,7 @@ void PairGranHooke::compute(int eflag, int vflag)
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -299,6 +300,7 @@ double PairGranHooke::single(int i, int j, int /*itype*/, int /*jtype*/, double
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

10
src/GRANULAR/pair_gran_hooke_history.cpp
View File

@ -237,6 +237,7 @@ void PairGranHookeHistory::compute(int eflag, int vflag)
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities
@ -356,7 +357,7 @@ void PairGranHookeHistory::allocate()
void PairGranHookeHistory::settings(int narg, char **arg)
{
if (narg != 6) error->all(FLERR,"Illegal pair_style command");
if (narg != 6 && narg != 7) error->all(FLERR,"Illegal pair_style command");
kn = utils::numeric(FLERR,arg[0],false,lmp);
if (strcmp(arg[1],"NULL") == 0) kt = kn * 2.0/7.0;
@ -370,6 +371,12 @@ void PairGranHookeHistory::settings(int narg, char **arg)
dampflag = utils::inumeric(FLERR,arg[5],false,lmp);
if (dampflag == 0) gammat = 0.0;
limit_damping = 0;
if (narg == 7) {
if (strcmp(arg[6], "limit_damping") == 0) limit_damping = 1;
else error->all(FLERR,"Illegal pair_style command");
}
if (kn < 0.0 || kt < 0.0 || gamman < 0.0 || gammat < 0.0 ||
xmu < 0.0 || xmu > 10000.0 || dampflag < 0 || dampflag > 1)
error->all(FLERR,"Illegal pair_style command");
@ -686,6 +693,7 @@ double PairGranHookeHistory::single(int i, int j, int /*itype*/, int /*jtype*/,
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if(limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

1
src/GRANULAR/pair_gran_hooke_history.h
View File

@ -49,6 +49,7 @@ class PairGranHookeHistory : public Pair {
double dt;
int freeze_group_bit;
int history;
int limit_damping;
int neighprev;
double *onerad_dynamic,*onerad_frozen;

43
src/GRANULAR/pair_granular.cpp
View File

@ -81,6 +81,8 @@ PairGranular::PairGranular(LAMMPS *lmp) : Pair(lmp)
maxrad_dynamic = nullptr;
maxrad_frozen = nullptr;
limit_damping = nullptr;
history_transfer_factors = nullptr;
dt = update->dt;
@ -130,6 +132,7 @@ PairGranular::~PairGranular()
memory->destroy(tangential_model);
memory->destroy(roll_model);
memory->destroy(twist_model);
memory->destroy(limit_damping);
delete [] onerad_dynamic;
delete [] onerad_frozen;
@ -364,12 +367,13 @@ void PairGranular::compute(int eflag, int vflag)
damp_normal = a*meff;
} else if (damping_model[itype][jtype] == TSUJI) {
damp_normal = sqrt(meff*knfac);
}
} else damp_normal = 0.0;
damp_normal_prefactor = normal_coeffs[itype][jtype][1]*damp_normal;
Fdamp = -damp_normal_prefactor*vnnr;
Fntot = Fne + Fdamp;
if (limit_damping[itype][jtype] && (Fntot < 0.0)) Fntot = 0.0;
//****************************************
// tangential force, including history effects
@ -540,20 +544,17 @@ void PairGranular::compute(int eflag, int vflag)
relrot1 = omega[i][0] - omega[j][0];
relrot2 = omega[i][1] - omega[j][1];
relrot3 = omega[i][2] - omega[j][2];
// rolling velocity,
// see eq. 31 of Wang et al, Particuology v 23, p 49 (2015)
// this is different from the Marshall papers,
// which use the Bagi/Kuhn formulation
// for rolling velocity (see Wang et al for why the latter is wrong)
// - 0.5*((radj-radi)/radsum)*vtr1;
// - 0.5*((radj-radi)/radsum)*vtr2;
// - 0.5*((radj-radi)/radsum)*vtr3;
}
//****************************************
// rolling resistance
//****************************************
if (roll_model[itype][jtype] != ROLL_NONE) {
// rolling velocity,
// see eq. 31 of Wang et al, Particuology v 23, p 49 (2015)
// this is different from the Marshall papers,
// which use the Bagi/Kuhn formulation
// for rolling velocity (see Wang et al for why the latter is wrong)
vrl1 = Reff*(relrot2*nz - relrot3*ny);
vrl2 = Reff*(relrot3*nx - relrot1*nz);
vrl3 = Reff*(relrot1*ny - relrot2*nx);
@ -740,6 +741,7 @@ void PairGranular::allocate()
memory->create(tangential_model,n+1,n+1,"pair:tangential_model");
memory->create(roll_model,n+1,n+1,"pair:roll_model");
memory->create(twist_model,n+1,n+1,"pair:twist_model");
memory->create(limit_damping,n+1,n+1,"pair:limit_damping");
onerad_dynamic = new double[n+1];
onerad_frozen = new double[n+1];
@ -793,6 +795,7 @@ void PairGranular::coeff(int narg, char **arg)
roll_model_one = ROLL_NONE;
twist_model_one = TWIST_NONE;
damping_model_one = VISCOELASTIC;
int ld_flag = 0;
int iarg = 2;
while (iarg < narg) {
@ -967,12 +970,15 @@ void PairGranular::coeff(int narg, char **arg)
error->all(FLERR, "Illegal pair_coeff command, not enough parameters");
cutoff_one = utils::numeric(FLERR,arg[iarg+1],false,lmp);
iarg += 2;
} else error->all(FLERR, "Illegal pair coeff command");
} else if (strcmp(arg[iarg], "limit_damping") == 0) {
ld_flag = 1;
iarg += 1;
} else error->all(FLERR, "Illegal pair_coeff command");
}
// error not to specify normal or tangential model
if ((normal_model_one < 0) || (tangential_model_one < 0))
error->all(FLERR, "Illegal pair coeff command, "
error->all(FLERR, "Illegal pair_coeff command, "
"must specify normal or tangential contact model");
int count = 0;
@ -984,6 +990,14 @@ void PairGranular::coeff(int narg, char **arg)
27.467*powint(cor,4)-18.022*powint(cor,5)+4.8218*powint(cor,6);
} else damp = normal_coeffs_one[1];
if (ld_flag && normal_model_one == JKR)
error->all(FLERR,"Illegal pair_coeff command, "
"Cannot limit damping with JKR model");
if (ld_flag && normal_model_one == DMT)
error->all(FLERR,"Illegal pair_coeff command, "
"Cannot limit damping with DMT model");
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
normal_model[i][j] = normal_model[j][i] = normal_model_one;
@ -1026,11 +1040,14 @@ void PairGranular::coeff(int narg, char **arg)
cutoff_type[i][j] = cutoff_type[j][i] = cutoff_one;
limit_damping[i][j] = limit_damping[j][i] = ld_flag;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
}
@ -1303,6 +1320,7 @@ void PairGranular::write_restart(FILE *fp)
fwrite(&tangential_model[i][j],sizeof(int),1,fp);
fwrite(&roll_model[i][j],sizeof(int),1,fp);
fwrite(&twist_model[i][j],sizeof(int),1,fp);
fwrite(&limit_damping[i][j],sizeof(int),1,fp);
fwrite(normal_coeffs[i][j],sizeof(double),4,fp);
fwrite(tangential_coeffs[i][j],sizeof(double),3,fp);
fwrite(roll_coeffs[i][j],sizeof(double),3,fp);
@ -1333,6 +1351,7 @@ void PairGranular::read_restart(FILE *fp)
utils::sfread(FLERR,&tangential_model[i][j],sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,&roll_model[i][j],sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,&twist_model[i][j],sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,&limit_damping[i][j],sizeof(int),1,fp,nullptr,error);
utils::sfread(FLERR,normal_coeffs[i][j],sizeof(double),4,fp,nullptr,error);
utils::sfread(FLERR,tangential_coeffs[i][j],sizeof(double),3,fp,nullptr,error);
utils::sfread(FLERR,roll_coeffs[i][j],sizeof(double),3,fp,nullptr,error);
@ -1344,6 +1363,7 @@ void PairGranular::read_restart(FILE *fp)
MPI_Bcast(&tangential_model[i][j],1,MPI_INT,0,world);
MPI_Bcast(&roll_model[i][j],1,MPI_INT,0,world);
MPI_Bcast(&twist_model[i][j],1,MPI_INT,0,world);
MPI_Bcast(&limit_damping[i][j],1,MPI_INT,0,world);
MPI_Bcast(normal_coeffs[i][j],4,MPI_DOUBLE,0,world);
MPI_Bcast(tangential_coeffs[i][j],3,MPI_DOUBLE,0,world);
MPI_Bcast(roll_coeffs[i][j],3,MPI_DOUBLE,0,world);
@ -1529,6 +1549,7 @@ double PairGranular::single(int i, int j, int itype, int jtype,
Fdamp = -damp_normal_prefactor*vnnr;
Fntot = Fne + Fdamp;
if (limit_damping[itype][jtype] && (Fntot < 0.0)) Fntot = 0.0;
jnum = list->numneigh[i];
jlist = list->firstneigh[i];

1
src/GRANULAR/pair_granular.h
View File

@ -70,6 +70,7 @@ class PairGranular : public Pair {
// model choices
int **normal_model, **damping_model;
int **tangential_model, **roll_model, **twist_model;
int **limit_damping;
// history flags
int normal_history, tangential_history, roll_history, twist_history;

1
src/KOKKOS/pair_gran_hooke_history_kokkos.cpp
View File

@ -392,6 +392,7 @@ void PairGranHookeHistoryKokkos<DeviceType>::operator()(TagPairGranHookeHistoryC
F_FLOAT damp = meff*gamman*vnnr*rsqinv;
F_FLOAT ccel = kn*(radsum-r)*rinv - damp;
if(limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

1
src/USER-OMP/pair_gran_hertz_history_omp.cpp
View File

@ -224,6 +224,7 @@ void PairGranHertzHistoryOMP::eval(int iifrom, int iito, ThrData * const thr)
ccel = kn*(radsum-r)*rinv - damp;
polyhertz = sqrt((radsum-r)*radi*radj / radsum);
ccel *= polyhertz;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

1
src/USER-OMP/pair_gran_hooke_history_omp.cpp
View File

@ -223,6 +223,7 @@ void PairGranHookeHistoryOMP::eval(int iifrom, int iito, ThrData * const thr)
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities

1
src/USER-OMP/pair_gran_hooke_omp.cpp
View File

@ -197,6 +197,7 @@ void PairGranHookeOMP::eval(int iifrom, int iito, ThrData * const thr)
damp = meff*gamman*vnnr*rsqinv;
ccel = kn*(radsum-r)*rinv - damp;
if (limit_damping && (ccel < 0.0)) ccel = 0.0;
// relative velocities