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lammps/src/fix_gravity.cpp
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fix_gravity.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
www.cs.sandia.gov/~sjplimp/lammps.html
Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
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 "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "fix_gravity.h"
#include "atom.h"
#include "update.h"
#include "error.h"
/* ---------------------------------------------------------------------- */
FixGravity::FixGravity(int narg, char **arg) : Fix(narg, arg)
{
if (narg < 4) error->all("Illegal fix gravity command");
if (strcmp(arg[3],"chute") == 0) {
if (narg != 5) error->all("Illegal fix gravity command");
if (atom->check_style("granular") == 0)
error->all("Must use fix gravity chute with atom style granular");
dynamic = 0;
granular = 1;
phi = 0.0;
theta = 180.0 - atof(arg[4]);
} else if (strcmp(arg[3],"spherical") == 0) {
if (narg != 6) error->all("Illegal fix gravity command");
if (atom->check_style("granular") == 0)
error->all("Must use fix gravity spherical with atom style granular");
dynamic = 0;
granular = 1;
phi = atof(arg[4]);
theta = atof(arg[5]);
} else if (strcmp(arg[3],"gradient") == 0) {
if (narg != 8) error->all("Illegal fix gravity command");
if (atom->check_style("granular") == 0)
error->all("Must use fix gravity gradient with atom style granular");
dynamic = 1;
granular = 1;
phi = atof(arg[4]);
theta = atof(arg[5]);
phigrad = atof(arg[6]);
thetagrad = atof(arg[7]);
} else if (strcmp(arg[3],"vector") == 0) {
if (narg != 8) error->all("Illegal fix gravity command");
if (atom->check_style("granular") != 0)
error->all("Cannot use fix gravity vector with atom style granular");
dynamic = 0;
granular = 0;
magnitude = atof(arg[4]);
xdir = atof(arg[5]);
ydir = atof(arg[6]);
zdir = atof(arg[7]);
} else error->all("Illegal fix gravity command");
double PI = 2.0 * asin(1.0);
degree2rad = 2.0*PI / 360.0;
time_initial = update->ntimestep;
}
/* ---------------------------------------------------------------------- */
int FixGravity::setmask()
{
int mask = 0;
mask |= POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixGravity::init()
{
dt = update->dt;
if (granular) {
xgrav = sin(degree2rad * theta) * cos(degree2rad * phi);
ygrav = sin(degree2rad * theta) * sin(degree2rad * phi);
zgrav = cos(degree2rad * theta);
} else {
double length = sqrt(xdir*xdir + ydir*ydir + zdir*zdir);
xgrav = magnitude * xdir/length;
ygrav = magnitude * ydir/length;
zgrav = magnitude * zdir/length;
}
}
/* ---------------------------------------------------------------------- */
void FixGravity::setup()
{
post_force(1);
}
/* ---------------------------------------------------------------------- */
void FixGravity::post_force(int vflag)
{
// update direction of gravity vector if dynamic
if (dynamic) {
double phi_current = degree2rad *
(phi + (update->ntimestep-time_initial)*dt*phigrad*360.0);
double theta_current = degree2rad *
(theta + (update->ntimestep-time_initial)*dt*thetagrad*360.0);
xgrav = sin(theta_current) * cos(phi_current);
ygrav = sin(theta_current) * sin(phi_current);
zgrav = cos(theta_current);
}
double **f = atom->f;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *mask = atom->mask;
int *type = atom->type;
int nlocal = atom->nlocal;
double massone;
if (granular) {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
f[i][0] += rmass[i]*xgrav;
f[i][1] += rmass[i]*ygrav;
f[i][2] += rmass[i]*zgrav;
}
} else {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
massone = mass[type[i]];
f[i][0] += massone*xgrav;
f[i][1] += massone*ygrav;
f[i][2] += massone*zgrav;
}
}
}
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