Files
lammps/src/GRANULAR/fix_granular_mdr.cpp
2024-12-18 17:44:12 -07:00

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24 KiB
C++

/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
https://www.lammps.org/, Sandia National Laboratories
LAMMPS development team: developers@lammps.org
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing authors:
William Zunker (MIT), Sachith Dunatunga (MIT),
Dan Bolintineanu (SNL), Joel Clemmer (SNL)
----------------------------------------------------------------------- */
#include "fix_granular_mdr.h"
#include "atom.h"
#include "comm.h"
#include "error.h"
#include "fix_wall_gran_region.h"
#include "fix_neigh_history.h"
#include "force.h"
#include "granular_model.h"
#include "gran_sub_mod_normal.h"
#include "input.h"
#include "math_const.h"
#include "memory.h"
#include "modify.h"
#include "neigh_list.h"
#include "pair.h"
#include "pair_granular.h"
#include "region.h"
#include "update.h"
#include "variable.h"
#include <algorithm>
#include <iomanip>
#include <sstream>
using namespace LAMMPS_NS;
using namespace Granular_NS;
using namespace FixConst;
using MathConst::MY_PI;
enum {MEAN_SURF_DISP, RADIUS_UPDATE};
/* ---------------------------------------------------------------------- */
FixGranularMDR::FixGranularMDR(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
comm_forward = 20; // value needs to match number of values you communicate
id_fix = nullptr;
}
/* ---------------------------------------------------------------------- */
FixGranularMDR::~FixGranularMDR()
{
if (id_fix) modify->delete_fix(id_fix);
}
/* ---------------------------------------------------------------------- */
int FixGranularMDR::setmask()
{
int mask = 0;
mask |= PRE_FORCE | END_OF_STEP;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::post_constructor()
{
int tmp1, tmp2;
id_fix = utils::strdup("MDR_PARTICLE_HISTORY_VARIABLES");
modify->add_fix(fmt::format("{} all property/atom d_Ro d_Vcaps d_Vgeo d_Velas d_eps_bar d_dRnumerator d_dRdenominator d_Acon0 d_Acon1 d_Atot d_Atot_sum d_ddelta_bar d_psi d_psi_b d_history_setup_flag d_sigmaxx d_sigmayy d_sigmazz d_contacts d_adhesive_length ghost yes", id_fix));
int index_Ro = atom->find_custom("Ro",tmp1,tmp2);
int index_Vcaps = atom->find_custom("Vcaps",tmp1,tmp2);
int index_Vgeo = atom->find_custom("Vgeo",tmp1,tmp2);
int index_Velas = atom->find_custom("Velas",tmp1,tmp2);
int index_eps_bar = atom->find_custom("eps_bar",tmp1,tmp2);
int index_dRnumerator = atom->find_custom("dRnumerator",tmp1,tmp2);
int index_dRdenominator = atom->find_custom("dRdenominator",tmp1,tmp2);
int index_Acon0 = atom->find_custom("Acon0",tmp1,tmp2);
int index_Acon1 = atom->find_custom("Acon1",tmp1,tmp2);
int index_Atot = atom->find_custom("Atot",tmp1,tmp2);
int index_Atot_sum = atom->find_custom("Atot_sum",tmp1,tmp2);
int index_ddelta_bar = atom->find_custom("ddelta_bar",tmp1,tmp2);
int index_psi = atom->find_custom("psi",tmp1,tmp2);
int index_psi_b = atom->find_custom("psi_b",tmp1,tmp2);
int index_history_setup_flag = atom->find_custom("history_setup_flag",tmp1,tmp2);
int index_sigmaxx = atom->find_custom("sigmaxx",tmp1,tmp2);
int index_sigmayy = atom->find_custom("sigmayy",tmp1,tmp2);
int index_sigmazz = atom->find_custom("sigmazz",tmp1,tmp2);
int index_contacts = atom->find_custom("contacts",tmp1,tmp2);
int index_adhesive_length = atom->find_custom("adhesive_length",tmp1,tmp2);
Ro = atom->dvector[index_Ro];
Vgeo = atom->dvector[index_Vgeo];
Velas = atom->dvector[index_Velas];
Vcaps = atom->dvector[index_Vcaps];
eps_bar = atom->dvector[index_eps_bar];
dRnumerator = atom->dvector[index_dRnumerator];
dRdenominator = atom->dvector[index_dRdenominator];
Acon0 = atom->dvector[index_Acon0];
Acon1 = atom->dvector[index_Acon1];
Atot = atom->dvector[index_Atot];
Atot_sum = atom->dvector[index_Atot_sum];
ddelta_bar = atom->dvector[index_ddelta_bar];
psi = atom->dvector[index_psi];
psi_b = atom->dvector[index_psi_b];
sigmaxx = atom->dvector[index_sigmaxx];
sigmayy = atom->dvector[index_sigmayy];
sigmazz = atom->dvector[index_sigmazz];
history_setup_flag = atom->dvector[index_history_setup_flag];
contacts = atom->dvector[index_contacts];
adhesive_length = atom->dvector[index_adhesive_length];
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::setup_pre_force(int /*vflag*/)
{
pre_force(0);
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::setup(int /*vflag*/)
{
end_of_step();
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::pre_force(int)
{
radius_update();
comm_stage = RADIUS_UPDATE;
comm->forward_comm(this, 20);
calculate_contact_penalty();
mean_surf_disp();
auto fix_list = modify->get_fix_by_style("wall/gran/region");
for (int w = 0; w < fix_list.size(); w++) {
update_fix_gran_wall(fix_list[w]);
}
comm_stage = MEAN_SURF_DISP;
comm->forward_comm(this, 1);
}
/* ---------------------------------------------------------------------- */
int FixGranularMDR::pack_forward_comm(int n, int *list, double *buf, int /*pbc_flag*/,int * /*pbc*/)
{
int m = 0;
if (comm_stage == RADIUS_UPDATE) {
for (int i = 0; i < n; i++) {
int j = list[i];
buf[m++] = Ro[j]; // 1
buf[m++] = Vgeo[j]; // 2
buf[m++] = Velas[j]; // 3
buf[m++] = Vcaps[j]; // 4
buf[m++] = eps_bar[j]; // 5
buf[m++] = dRnumerator[j]; // 6
buf[m++] = dRdenominator[j]; // 7
buf[m++] = Acon0[j]; // 8
buf[m++] = Acon1[j]; // 9
buf[m++] = Atot[j]; // 10
buf[m++] = Atot_sum[j]; // 11
buf[m++] = ddelta_bar[j]; // 12
buf[m++] = psi[j]; // 13
buf[m++] = psi_b[j]; // 14
buf[m++] = sigmaxx[j]; // 15
buf[m++] = sigmayy[j]; // 16
buf[m++] = sigmazz[j]; // 17
buf[m++] = history_setup_flag[j]; // 18
buf[m++] = contacts[j]; // 19
buf[m++] = adhesive_length[j]; // 20
}
} else {
for (int i = 0; i < n; i++) {
int j = list[i];
buf[m++] = ddelta_bar[j];
}
}
return m;
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::unpack_forward_comm(int n, int first, double *buf)
{
int m = 0;
int last = first + n;
if (comm_stage == RADIUS_UPDATE) {
for (int i = first; i < last; i++) {
Ro[i] = buf[m++]; // 1
Vgeo[i] = buf[m++]; // 2
Velas[i] = buf[m++]; // 3
Vcaps[i] = buf[m++]; // 4
eps_bar[i] = buf[m++]; // 5
dRnumerator[i] = buf[m++]; // 6
dRdenominator[i] = buf[m++]; // 7
Acon0[i] = buf[m++]; // 8
Acon1[i] = buf[m++]; // 9
Atot[i] = buf[m++]; // 10
Atot_sum[i] = buf[m++]; // 11
ddelta_bar[i] = buf[m++]; // 12
psi[i] = buf[m++]; // 13
psi_b[i] = buf[m++]; // 14
sigmaxx[i] = buf[m++]; // 15
sigmayy[i] = buf[m++]; // 16
sigmazz[i] = buf[m++]; // 17
history_setup_flag[i] = buf[m++]; // 18
contacts[i] = buf[m++]; // 19
adhesive_length[i] = buf[m++]; // 20
}
} else {
for (int i = first; i < last; i++) {
ddelta_bar[i] = buf[m++];
}
}
}
/* ---------------------------------------------------------------------- */
void FixGranularMDR::end_of_step()
{
// update the apparent radius of every particle
double *radius = atom->radius;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++) {
const double R = radius[i];
Atot[i] = 4.0*MY_PI*pow(R,2.0) + Atot_sum[i];
const double Vo = 4.0/3.0*MY_PI*pow(Ro[i],3.0);
const double Vgeoi = 4.0/3.0*MY_PI*pow(R,3.0) - Vcaps[i];
Vgeo[i] = std::min(Vgeoi,Vo);
const double Afree = Atot[i] - Acon1[i];
psi[i] = Afree/Atot[i];
const double dR = std::max(dRnumerator[i]/(dRdenominator[i] - 4.0*MY_PI*pow(R,2.0)),0.0);
if (psi_b[i] < psi[i]) {
if ((radius[i] + dR) < (1.5*Ro[i])) radius[i] += dR;
}
Velas[i] = Vo*(1.0 + eps_bar[i]);
Vcaps[i] = 0.0;
eps_bar[i] = 0.0;
dRnumerator[i] = 0.0;
dRdenominator[i] = 0.0;
Acon0[i] = Acon1[i];
Acon1[i] = 0.0;
Atot_sum[i] = 0.0;
ddelta_bar[i] = 0.0;
}
comm_stage = RADIUS_UPDATE;
comm->forward_comm(this, 20);
}
/* ----------------------------------------------------------------------
calculate updated radius for atoms
------------------------------------------------------------------------- */
void FixGranularMDR::radius_update()
{
PairGranular * pair = dynamic_cast<PairGranular *>(force->pair_match("granular",1));
class GranularModel* model;
class GranularModel** models_list = pair->models_list;
class GranSubModNormalMDR* norm_model = nullptr;
for (int i = 0; i < pair->nmodels; i++) {
model = models_list[i];
if (model->normal_model->name == "mdr") norm_model = dynamic_cast<GranSubModNormalMDR *>(model->normal_model);
}
if (norm_model == nullptr) error->all(FLERR, "Did not find mdr model");
double *radius = atom->radius;
int nlocal = atom->nlocal;
for (int i = 0; i < nlocal; i++) {
if (history_setup_flag[i] < 1e-16) {
Ro[i] = radius[i];
Vgeo[i] = 4.0/3.0*MY_PI*pow(Ro[i],3.0);
Velas[i] = 4.0/3.0*MY_PI*pow(Ro[i],3.0);
Atot[i] = 4.0*MY_PI*pow(Ro[i],2.0);
psi[i] = 1.0;
psi_b[i] = norm_model->psi_b;
history_setup_flag[i] = 1.0;
}
sigmaxx[i] = 0.0;
sigmayy[i] = 0.0;
sigmazz[i] = 0.0;
contacts[i] = 0.0;
adhesive_length[i] = 0.0;
}
}
/* ----------------------------------------------------------------------
...
------------------------------------------------------------------------- */
void FixGranularMDR::calculate_contact_penalty()
{
FixNeighHistory * fix_history = dynamic_cast<FixNeighHistory *>(modify->get_fix_by_id("NEIGH_HISTORY_GRANULAR"));
PairGranular * pair = dynamic_cast<PairGranular *>(force->pair_match("granular",1));
NeighList * list = pair->list;
const int size_history = pair->get_size_history();
int i,j,k,lv1,ii,jj,inum,jnum,itype,jtype,ktype;
int *ilist,*jlist,*numneigh,**firstneigh;
int *touch,**firsttouch;
double *history_ij,*history_ik,*history_jk,*history_kj,*allhistory,*allhistory_j,*allhistory_k,**firsthistory;
bool touchflag = false;
double **x = atom->x;
int *type = atom->type;
double *radius = atom->radius;
int nlocal = atom->nlocal;
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
firsttouch = fix_history->firstflag;
firsthistory = fix_history->firstvalue;
// contact penalty calculation
for (int ii = 0; ii < inum; ii++) {
const int i = ilist[ii];
const double xtmp = x[i][0];
const double ytmp = x[i][1];
const double ztmp = x[i][2];
allhistory = firsthistory[i];
double radi = radius[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for (int jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
jtype = type[j];
double radj = radius[j];
const double delx_ij = x[j][0] - xtmp;
const double dely_ij = x[j][1] - ytmp;
const double delz_ij = x[j][2] - ztmp;
const double rsq_ij = delx_ij*delx_ij + dely_ij*dely_ij + delz_ij*delz_ij;
const double r_ij = sqrt(rsq_ij);
const double rinv_ij = 1.0/r_ij;
const double radsum_ij = radi + radj;
const double deltan_ij = radsum_ij - r_ij;
if (deltan_ij >= 0.0) {
for (int kk = jj; kk < jnum; kk++) {
k = jlist[kk];
k &= NEIGHMASK;
ktype = type[k];
if (kk != jj) {
const double delx_ik = x[k][0] - xtmp;
const double dely_ik = x[k][1] - ytmp;
const double delz_ik = x[k][2] - ztmp;
const double rsq_ik = delx_ik*delx_ik + dely_ik*dely_ik + delz_ik*delz_ik;
const double r_ik = sqrt(rsq_ik);
const double rinv_ik = 1.0/r_ik;
const double radk = radius[k];
const double radsum_ik = radi + radk;
const double deltan_ik = radsum_ik - r_ik;
const double delx_jk = x[k][0] - x[j][0];
const double dely_jk = x[k][1] - x[j][1];
const double delz_jk = x[k][2] - x[j][2];
const double rsq_jk = delx_jk*delx_jk + dely_jk*dely_jk + delz_jk*delz_jk;
const double r_jk = sqrt(rsq_jk);
const double rinv_jk = 1.0/r_jk;
const double radsum_jk = radj + radk;
const double deltan_jk = radsum_jk - r_jk;
if (deltan_ik >= 0.0 && deltan_jk >= 0.0) {
// pull ij history
history_ij = &allhistory[size_history * jj];
double * pij = &history_ij[22]; // penalty for contact i and j
// pull ik history
history_ik = &allhistory[size_history * kk];
double * pik = &history_ik[22]; // penalty for contact i and k
// we don't know if who owns the contact ahead of time, k might be in j's neigbor list or vice versa,
// so we need to manually search to figure out the owner check if k is in the neighbor list of j
double * pjk = NULL;
int * const jklist = firstneigh[j];
const int jknum = numneigh[j];
for (int jk = 0; jk < jknum; jk++) {
const int kneigh = jklist[jk] & NEIGHMASK;
if (k == kneigh) {
allhistory_j = firsthistory[j];
history_jk = &allhistory_j[size_history * jk];
pjk = &history_jk[22]; // penalty for contact j and k
break;
}
}
// check if j is in the neighbor list of k
if (pjk == NULL) {
int * const kjlist = firstneigh[k];
const int kjnum = numneigh[k];
for (int kj = 0; kj < kjnum; kj++) {
const int jneigh = kjlist[kj] & NEIGHMASK;
if (j == jneigh) {
allhistory_k = firsthistory[k];
history_kj = &allhistory_k[size_history * kj];
pjk = &history_kj[22]; // penalty for contact j and k
break;
}
}
}
std::vector<double> distances = {r_ij,r_ik,r_jk};
auto maxElement = std::max_element(distances.begin(), distances.end());
double maxValue = *maxElement;
int maxIndex = std::distance(distances.begin(), maxElement);
if (maxIndex == 0) { // the central particle is k
const double enx_ki = -delx_ik * rinv_ik;
const double eny_ki = -dely_ik * rinv_ik;
const double enz_ki = -delz_ik * rinv_ik;
const double enx_kj = -delx_jk * rinv_jk;
const double eny_kj = -dely_jk * rinv_jk;
const double enz_kj = -delz_jk * rinv_jk;
const double alpha = std::acos(enx_ki*enx_kj + eny_ki*eny_kj + enz_ki*enz_kj);
pij[0] += 1.0/( 1.0 + std::exp(-50.0*(alpha/MY_PI - 1.0/2.0)));
} else if (maxIndex == 1) { // the central particle is j
const double enx_ji = -delx_ij * rinv_ij;
const double eny_ji = -dely_ij * rinv_ij;
const double enz_ji = -delz_ij * rinv_ij;
const double enx_jk = delx_jk * rinv_jk;
const double eny_jk = dely_jk * rinv_jk;
const double enz_jk = delz_jk * rinv_jk;
const double alpha = std::acos(enx_ji*enx_jk + eny_ji*eny_jk + enz_ji*enz_jk);
pik[0] += 1.0/( 1.0 + std::exp(-50.0*(alpha/MY_PI - 1.0/2.0)));
} else { // the central particle is i
if (j < atom->nlocal || k < atom->nlocal) {
const double enx_ij = delx_ij * rinv_ij;
const double eny_ij = dely_ij * rinv_ij;
const double enz_ij = delz_ij * rinv_ij;
const double enx_ik = delx_ik * rinv_ik;
const double eny_ik = dely_ik * rinv_ik;
const double enz_ik = delz_ik * rinv_ik;
const double alpha = std::acos(enx_ij*enx_ik + eny_ij*eny_ik + enz_ij*enz_ik);
pjk[0] += 1.0/( 1.0 + std::exp(-50.0*(alpha/MY_PI - 1.0/2.0)));
}
}
}
}
}
}
}
}
}
/* ----------------------------------------------------------------------
...
------------------------------------------------------------------------- */
void FixGranularMDR::mean_surf_disp()
{
FixNeighHistory * fix_history = dynamic_cast<FixNeighHistory *>(modify->get_fix_by_id("NEIGH_HISTORY_GRANULAR"));
PairGranular * pair = dynamic_cast<PairGranular *>(force->pair_match("granular",1));
NeighList * list = pair->list;
const int size_history = pair->get_size_history();
int i,j,k,ii,jj,inum,jnum,itype,jtype;
int *ilist,*jlist,*numneigh,**firstneigh;
int *touch,**firsttouch;
double *history,*allhistory,**firsthistory;
bool touchflag = false;
class GranularModel* model;
class GranularModel** models_list = pair->models_list;
int ** types_indices = pair->types_indices;
double **x = atom->x;
int *type = atom->type;
double *radius = atom->radius;
int nlocal = atom->nlocal;
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
firsttouch = fix_history->firstflag;
firsthistory = fix_history->firstvalue;
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
itype = type[i];
touch = firsttouch[i];
allhistory = firsthistory[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
jtype = type[j];
model = models_list[types_indices[itype][jtype]];
// Reset model and copy initial geometric data
model->xi = x[i];
model->xj = x[j];
model->radi = radius[i];
model->radj = radius[j];
model->i = i;
model->j = j;
model->touch = touch[jj];
touchflag = model->check_contact();
// is it necessary to clear the history here???
if (!touchflag) {
touch[jj] = 0;
history = &allhistory[size_history * jj];
for (k = 0; k < size_history; k++) history[k] = 0.0;
continue;
}
touch[jj] = 1;
history = &allhistory[size_history * jj];
model->history = history;
const double delta = model->radsum - sqrt(model->rsq);
const int delta_offset_0 = 0; // apparent overlap
const int delta_offset_1 = 1;
const int Ac_offset_0 = 18; // contact area
const int Ac_offset_1 = 19;
const int deltamax_offset_ = 23;
const int deltap_offset_0 = 24;
const int deltap_offset_1 = 25;
double deltamax = history[deltamax_offset_];
double deltap0 = history[deltap_offset_0];
double deltap1 = history[deltap_offset_1];
if (delta > deltamax) deltamax = delta;
double delta0old = history[delta_offset_0];
double delta1old = history[delta_offset_1];
int i0;
int i1;
if (atom->tag[i] > atom->tag[j]) {
i0 = i;
i1 = j;
} else {
i0 = j;
i1 = i;
}
double R0 = radius[i0];
double R1 = radius[i1];
double delta_geo0;
double delta_geo1;
double deltaOpt1 = deltamax*(deltamax - 2.0*R1)/(2.0*(deltamax - R0 - R1));
double deltaOpt2 = deltamax*(deltamax - 2.0*R0)/(2.0*(deltamax - R0 - R1));
(R0 < R1) ? delta_geo0 = MAX(deltaOpt1,deltaOpt2) : delta_geo0 = MIN(deltaOpt1,deltaOpt2);
(R0 < R1) ? delta_geo1 = MIN(deltaOpt1,deltaOpt2) : delta_geo1 = MAX(deltaOpt1,deltaOpt2);
double overlap_limit = 0.75;
if (delta_geo0/R0 > overlap_limit) {
delta_geo0 = R0*overlap_limit;
delta_geo1 = deltamax - delta_geo0;
} else if (delta_geo1/R1 > overlap_limit) {
delta_geo1 = R1*overlap_limit;
delta_geo0 = deltamax - delta_geo1;
}
double deltap = deltap0 + deltap1;
double delta0 = delta_geo0 + (deltap0 - delta_geo0)/(deltap - deltamax)*(delta-deltamax);
double delta1 = delta_geo1 + (deltap1 - delta_geo1)/(deltap - deltamax)*(delta-deltamax);
double ddel0 = delta0 - delta0old;
double ddel1 = delta1 - delta1old;
if (Acon0[i0] != 0.0) {
const double Ac_offset0 = history[Ac_offset_0];
ddelta_bar[i0] += Ac_offset0/Acon0[i0]*ddel0;
}
if (Acon0[i1] != 0.0) {
const double Ac_offset1 = history[Ac_offset_1];
ddelta_bar[i1] += Ac_offset1/Acon0[i1]*ddel1;
}
}
}
}
/* ----------------------------------------------------------------------
Update instance of fix gran/wall
------------------------------------------------------------------------- */
void FixGranularMDR::update_fix_gran_wall(Fix* fix_in)
{
FixWallGranRegion* fix = dynamic_cast<FixWallGranRegion*>(fix_in);
GranularModel * model = fix->model;
Region * region = fix->region;
const int size_history = model->size_history;
int i, m, nc, iwall;
double vwall[3];
bool touchflag = false;
int history_update = 1;
model->history_update = history_update;
int regiondynamic = region->dynamic_check();
if (!regiondynamic) vwall[0] = vwall[1] = vwall[2] = 00;
double **x = atom->x;
double *radius = atom->radius;
int *mask = atom->mask;
int nlocal = atom->nlocal;
if (regiondynamic) {
region->prematch();
region->set_velocity();
}
if (fix->peratom_flag) fix->clear_stored_contacts();
model->radj = 0.0;
for (i = 0; i < nlocal; i++) {
if (!(mask[i] & groupbit)) continue;
if (! region->match(x[i][0], x[i][1], x[i][2])) continue;
nc = region->surface(x[i][0], x[i][1], x[i][2], radius[i] + model->pulloff_distance(radius[i], 0.0));
if (nc == 0) {
fix->ncontact[i] = 0;
continue;
}
if (nc == 1) {
fix->c2r[0] = 0;
iwall = region->contact[0].iwall;
if (fix->ncontact[i] == 0) {
fix->ncontact[i] = 1;
fix->walls[i][0] = iwall;
for (m = 0; m < size_history; m++) fix->history_many[i][0][m] = 0.0;
} else if (fix->ncontact[i] > 1 || iwall != fix->walls[i][0])
fix->update_contacts(i, nc);
} else
fix->update_contacts(i, nc);
// process current contacts
for (int ic = 0; ic < nc; ic++) {
// Reset model and copy initial geometric data
model->dx[0] = region->contact[ic].delx;
model->dx[1] = region->contact[ic].dely;
model->dx[2] = region->contact[ic].delz;
model->radi = radius[i];
model->radj = region->contact[ic].radius;
model->r = region->contact[ic].r;
if (model->beyond_contact) model->touch = fix->history_many[i][fix->c2r[ic]][0];
touchflag = model->check_contact();
const double wij = 1.0;
if (Acon0[i] != 0.0) {
const double delta = model->radsum - model->r;
const double delta_offset0 = fix->history_many[i][fix->c2r[ic]][0];
const double ddelta = delta - delta_offset0;
const double Ac_offset0 = fix->history_many[i][fix->c2r[ic]][18];
ddelta_bar[i] += wij*Ac_offset0/Acon0[i]*ddelta;
}
}
}
}