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lammps/src/USER-SPH/pair_sph_idealgas.cpp
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pair_sph_idealgas.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
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.
------------------------------------------------------------------------- */
#include <math.h>
#include <stdlib.h>
#include "pair_sph_idealgas.h"
#include "atom.h"
#include "force.h"
#include "comm.h"
#include "neigh_list.h"
#include "memory.h"
#include "error.h"
#include "domain.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairSPHIdealGas::PairSPHIdealGas(LAMMPS *lmp) : Pair(lmp)
{
restartinfo = 0;
}
/* ---------------------------------------------------------------------- */
PairSPHIdealGas::~PairSPHIdealGas() {
if (allocated) {
memory->destroy(setflag);
memory->destroy(cutsq);
memory->destroy(cut);
memory->destroy(viscosity);
}
}
/* ---------------------------------------------------------------------- */
void PairSPHIdealGas::compute(int eflag, int vflag) {
int i, j, ii, jj, inum, jnum, itype, jtype;
double xtmp, ytmp, ztmp, delx, dely, delz, fpair;
int *ilist, *jlist, *numneigh, **firstneigh;
double vxtmp, vytmp, vztmp, imass, jmass, fi, fj, fvisc, h, ih, ihsq;
double rsq, wfd, delVdotDelR, mu, deltaE, ci, cj;
if (eflag || vflag)
ev_setup(eflag, vflag);
else
evflag = vflag_fdotr = 0;
double **v = atom->vest;
double **x = atom->x;
double **f = atom->f;
double *rho = atom->rho;
double *mass = atom->mass;
double *de = atom->de;
double *e = atom->e;
double *drho = atom->drho;
int *type = atom->type;
int nlocal = atom->nlocal;
int newton_pair = force->newton_pair;
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
vxtmp = v[i][0];
vytmp = v[i][1];
vztmp = v[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
imass = mass[itype];
fi = 0.4 * e[i] / imass / rho[i]; // ideal gas EOS; this expression is fi = pressure / rho^2
ci = sqrt(0.4*e[i]/imass); // speed of sound with heat capacity ratio gamma=1.4
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
j &= NEIGHMASK;
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx * delx + dely * dely + delz * delz;
jtype = type[j];
jmass = mass[jtype];
if (rsq < cutsq[itype][jtype]) {
h = cut[itype][jtype];
ih = 1. / h;
ihsq = ih * ih;
wfd = h - sqrt(rsq);
if (domain->dimension == 3) {
// Lucy Kernel, 3d
// Note that wfd, the derivative of the weight function with respect to r,
// is lacking a factor of r.
// The missing factor of r is recovered by
// (1) using delV . delX instead of delV . (delX/r) and
// (2) using f[i][0] += delx * fpair instead of f[i][0] += (delx/r) * fpair
wfd = -25.066903536973515383e0 * wfd * wfd * ihsq * ihsq * ihsq * ih;
} else {
// Lucy Kernel, 2d
wfd = -19.098593171027440292e0 * wfd * wfd * ihsq * ihsq * ihsq;
}
fj = 0.4 * e[j] / jmass / rho[j];
// dot product of velocity delta and distance vector
delVdotDelR = delx * (vxtmp - v[j][0]) + dely * (vytmp - v[j][1])
+ delz * (vztmp - v[j][2]);
// artificial viscosity (Monaghan 1992)
if (delVdotDelR < 0.) {
cj = sqrt(0.4*e[j]/jmass);
mu = h * delVdotDelR / (rsq + 0.01 * h * h);
fvisc = -viscosity[itype][jtype] * (ci + cj) * mu / (rho[i] + rho[j]);
} else {
fvisc = 0.;
}
// total pair force & thermal energy increment
fpair = -imass * jmass * (fi + fj + fvisc) * wfd;
deltaE = -0.5 * fpair * delVdotDelR;
f[i][0] += delx * fpair;
f[i][1] += dely * fpair;
f[i][2] += delz * fpair;
// and change in density
drho[i] += jmass * delVdotDelR * wfd;
// change in thermal energy
de[i] += deltaE;
if (newton_pair || j < nlocal) {
f[j][0] -= delx * fpair;
f[j][1] -= dely * fpair;
f[j][2] -= delz * fpair;
de[j] += deltaE;
drho[j] += imass * delVdotDelR * wfd;
}
if (evflag)
ev_tally(i, j, nlocal, newton_pair, 0.0, 0.0, fpair, delx, dely, delz);
if (evflag)
ev_tally(i, j, nlocal, newton_pair, 0.0, 0.0, fpair, delx, dely,
delz);
}
}
}
if (vflag_fdotr) virial_fdotr_compute();
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void PairSPHIdealGas::allocate() {
allocated = 1;
int n = atom->ntypes;
memory->create(setflag, n + 1, n + 1, "pair:setflag");
for (int i = 1; i <= n; i++)
for (int j = i; j <= n; j++)
setflag[i][j] = 0;
memory->create(cutsq, n + 1, n + 1, "pair:cutsq");
memory->create(cut, n + 1, n + 1, "pair:cut");
memory->create(viscosity, n + 1, n + 1, "pair:viscosity");
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairSPHIdealGas::settings(int narg, char **arg) {
if (narg != 0)
error->all(FLERR,
"Illegal number of setting arguments for pair_style sph/idealgas");
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairSPHIdealGas::coeff(int narg, char **arg) {
if (narg != 4)
error->all(FLERR,"Incorrect number of args for pair_style sph/idealgas coefficients");
if (!allocated)
allocate();
int ilo, ihi, jlo, jhi;
force->bounds(arg[0], atom->ntypes, ilo, ihi);
force->bounds(arg[1], atom->ntypes, jlo, jhi);
double viscosity_one = force->numeric(FLERR,arg[2]);
double cut_one = force->numeric(FLERR,arg[3]);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
viscosity[i][j] = viscosity_one;
//printf("setting cut[%d][%d] = %f\n", i, j, cut_one);
cut[i][j] = cut_one;
setflag[i][j] = 1;
count++;
}
}
if (count == 0)
error->all(FLERR,"Incorrect args for pair sph/idealgas coefficients");
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double PairSPHIdealGas::init_one(int i, int j) {
if (setflag[i][j] == 0) {
error->all(FLERR,"All pair sph/idealgas coeffs are not set");
}
cut[j][i] = cut[i][j];
return cut[i][j];
}
/* ---------------------------------------------------------------------- */
double PairSPHIdealGas::single(int i, int j, int itype, int jtype,
double rsq, double factor_coul, double factor_lj, double &fforce) {
fforce = 0.0;
return 0.0;
}
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