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relative threshold for contact frame update based on tangential critical force

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This commit is contained in:
Jibril B. Coulibaly
2020-08-21 13:20:53 -05:00
parent ee6ef98b9b
commit 921b6d8135
1 changed files with 47 additions and 37 deletions
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84
src/GRANULAR/pair_granular.cpp
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@ -177,6 +177,7 @@ void PairGranular::compute(int eflag, int vflag)
double tortwist1, tortwist2, tortwist3;
double shrmag,rsht,prjmag;
bool frameupdate;
int *ilist,*jlist,*numneigh,**firstneigh;
int *touch,**firsttouch;
double *history,*allhistory,**firsthistory;
@ -441,22 +442,29 @@ void PairGranular::compute(int eflag, int vflag)
// see e.g. eq. 17 of Luding, Gran. Matter 2008, v10,p235
if (historyupdate) {
rsht = history[0]*nx + history[1]*ny + history[2]*nz;
shrmag = sqrt(history[0]*history[0] + history[1]*history[1] +
history[2]*history[2]);
// projection
history[0] -= rsht*nx;
history[1] -= rsht*ny;
history[2] -= rsht*nz;
// also rescale to preserve magnitude
prjmag = sqrt(history[0]*history[0] + history[1]*history[1] +
history[2]*history[2]);
if (prjmag > 0) scalefac = shrmag/prjmag;
else scalefac = 0;
history[0] *= scalefac;
history[1] *= scalefac;
history[2] *= scalefac;
if (tangential_model[itype][jtype] == TANGENTIAL_MINDLIN_FORCE ||
tangential_model[itype][jtype] ==
TANGENTIAL_MINDLIN_RESCALE_FORCE)
frameupdate = fabs(rsht) < EPSILON*Fscrit;
else
frameupdate = fabs(rsht)*k_tangential < EPSILON*Fscrit;
if (frameupdate) {
shrmag = sqrt(history[0]*history[0] + history[1]*history[1] +
history[2]*history[2]);
// projection
history[0] -= rsht*nx;
history[1] -= rsht*ny;
history[2] -= rsht*nz;
// also rescale to preserve magnitude
prjmag = sqrt(history[0]*history[0] + history[1]*history[1] +
history[2]*history[2]);
if (prjmag > 0) scalefac = shrmag/prjmag;
else scalefac = 0;
history[0] *= scalefac;
history[1] *= scalefac;
history[2] *= scalefac;
}
// update history
if (tangential_model[itype][jtype] == TANGENTIAL_HISTORY ||
tangential_model[itype][jtype] == TANGENTIAL_MINDLIN ||
@ -553,39 +561,41 @@ void PairGranular::compute(int eflag, int vflag)
int rhist1 = rhist0 + 1;
int rhist2 = rhist1 + 1;
rolldotn = history[rhist0]*nx + history[rhist1]*ny + history[rhist2]*nz;
if (historyupdate) {
// rotate into tangential plane
rollmag = sqrt(history[rhist0]*history[rhist0] +
history[rhist1]*history[rhist1] +
history[rhist2]*history[rhist2]);
// 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;
k_roll = roll_coeffs[itype][jtype][0];
damp_roll = roll_coeffs[itype][jtype][1];
Frcrit = roll_coeffs[itype][jtype][2] * Fncrit;
if (historyupdate) {
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]);
// 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;
}
history[rhist0] += vrl1*dt;
history[rhist1] += vrl2*dt;
history[rhist2] += vrl3*dt;
}
k_roll = roll_coeffs[itype][jtype][0];
damp_roll = roll_coeffs[itype][jtype][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[itype][jtype][2] * Fncrit;
fr = sqrt(fr1*fr1 + fr2*fr2 + fr3*fr3);
if (fr > Frcrit) {