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fix_lb_momentum.cpp
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Sun, Jul 7, 12:57

fix_lb_momentum.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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing authors: Frances Mackay, Santtu Ollila, Colin Denniston (UWO)
Based on fix_momentum,
Contributing author: Naveen Michaud-Agrawal (Johns Hopkins U)
------------------------------------------------------------------------- */
#include "stdlib.h"
#include "string.h"
#include "fix_lb_momentum.h"
#include "atom.h"
#include "domain.h"
#include "group.h"
#include "error.h"
#include "fix_lb_fluid.h"
#include "modify.h"
#include "comm.h"
using namespace LAMMPS_NS;
using namespace FixConst;
/* ---------------------------------------------------------------------- */
FixLbMomentum::FixLbMomentum(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg < 4) error->all(FLERR,"Illegal fix lb/momentum command");
nevery = atoi(arg[3]);
if (nevery <= 0) error->all(FLERR,"Illegal fix lb/momentum command");
linear = 1;
xflag = 1;
yflag = 1;
zflag = 1;
int iarg = 4;
while (iarg < narg) {
if (strcmp(arg[iarg],"linear") == 0) {
if (iarg+4 > narg) error->all(FLERR,"Illegal fix lb/momentum command");
linear = 1;
xflag = atoi(arg[iarg+1]);
yflag = atoi(arg[iarg+2]);
zflag = atoi(arg[iarg+3]);
iarg += 4;
} else error->all(FLERR,"Illegal fix lb/momentum command");
}
if (linear == 0)
error->all(FLERR,"Illegal fix lb/momentum command");
if (linear)
if (xflag < 0 || xflag > 1 || yflag < 0 || yflag > 1 ||
zflag < 0 || zflag > 1) error->all(FLERR,"Illegal fix lb/momentum command");
// cannot have 0 atoms in group
if (group->count(igroup) == 0.0)
error->all(FLERR,"Fix lb/momentum group has no atoms");
for(int ifix=0; ifix<modify->nfix; ifix++)
if(strcmp(modify->fix[ifix]->style,"lb/fluid")==0)
fix_lb_fluid = (FixLbFluid *)modify->fix[ifix];
}
/* ---------------------------------------------------------------------- */
int FixLbMomentum::setmask()
{
int mask = 0;
mask |= END_OF_STEP;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixLbMomentum::init()
{
masstotal = group->mass(igroup);
}
/* ---------------------------------------------------------------------- */
void FixLbMomentum::end_of_step()
{
double masslb,masslbloc;
double momentumlbloc[3],momentumlb[3];
double vcmtotal[3];
int numvel = fix_lb_fluid->numvel;
double etacov[numvel];
double rho;
if (linear) {
double vcm[3];
group->vcm(igroup,masstotal,vcm);
// adjust velocities by vcm to zero linear momentum
// only adjust a component if flag is set
double **v = atom->v;
int *mask = atom->mask;
int nlocal = atom->nlocal;
int typeLB = fix_lb_fluid->typeLB;
int subNbx = fix_lb_fluid->subNbx;
int subNby = fix_lb_fluid->subNby;
int subNbz = fix_lb_fluid->subNbz;
double ***density_lb = fix_lb_fluid->density_lb;
double ****f_lb = fix_lb_fluid->f_lb;
double ****u_lb = fix_lb_fluid->u_lb;
double dm_lb = fix_lb_fluid->dm_lb;
double dx_lb = fix_lb_fluid->dx_lb;
double dt_lb = fix_lb_fluid->dt_lb;
double *Ng_lb = fix_lb_fluid->Ng_lb;
double *w_lb = fix_lb_fluid->w_lb;
double **mg_lb = fix_lb_fluid->mg_lb;
double ucmx,ucmy,ucmz;
//Calculate the total fluid mass and momentum.
masslbloc = 0.0;
momentumlbloc[0] = momentumlbloc[1] = momentumlbloc[2] = 0.0;
for(int i = 1; i<subNbx-1; i++)
for(int j = 1; j<subNby-1; j++)
for(int k = 1; k<subNbz-1; k++){
masslbloc += density_lb[i][j][k];
momentumlbloc[0] += density_lb[i][j][k]*u_lb[i][j][k][0];
momentumlbloc[1] += density_lb[i][j][k]*u_lb[i][j][k][1];
momentumlbloc[2] += density_lb[i][j][k]*u_lb[i][j][k][2];
}
MPI_Allreduce(&masslbloc,&masslb,1,MPI_DOUBLE,MPI_SUM,world);
MPI_Allreduce(&momentumlbloc[0],&momentumlb[0],3,MPI_DOUBLE,MPI_SUM,world);
momentumlb[0] *= dm_lb*dx_lb/dt_lb;
momentumlb[1] *= dm_lb*dx_lb/dt_lb;
momentumlb[2] *= dm_lb*dx_lb/dt_lb;
masslb *= dm_lb;
//Calculate the center of mass velocity of the entire system.
vcmtotal[0] = (masstotal*vcm[0] + momentumlb[0])/(masslb + masstotal);
vcmtotal[1] = (masstotal*vcm[1] + momentumlb[1])/(masslb + masstotal);
vcmtotal[2] = (masstotal*vcm[2] + momentumlb[2])/(masslb + masstotal);
//Subtract vcm from the particles.
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
if (xflag) v[i][0] -= vcmtotal[0];
if (yflag) v[i][1] -= vcmtotal[1];
if (zflag) v[i][2] -= vcmtotal[2];
}
vcmtotal[0] *= dt_lb/dx_lb;
vcmtotal[1] *= dt_lb/dx_lb;
vcmtotal[2] *= dt_lb/dx_lb;
ucmx = ucmy = ucmz = 0.0;
double density_old;
double u_old[3];
int **e = fix_lb_fluid->e;
//Subtract vcm from the fluid.
for(int i=0; i<subNbx; i++)
for(int j=0; j<subNby; j++)
for(int k=0; k<subNbz; k++){
rho = density_lb[i][j][k];
if(xflag) ucmx = vcmtotal[0];
if(yflag) ucmy = vcmtotal[1];
if(zflag) ucmz = vcmtotal[2];
if(numvel==15){
etacov[0]=0.0;
etacov[1]=rho*ucmx;
etacov[2]=rho*ucmy;
etacov[3]=rho*ucmz;
etacov[4]=rho*(2.*u_lb[i][j][k][0]*ucmx-ucmx*ucmx);
etacov[5]=rho*(2.*u_lb[i][j][k][1]*ucmy-ucmy*ucmy);
etacov[6]=rho*(2.*u_lb[i][j][k][2]*ucmz-ucmz*ucmz);
etacov[7]=rho*(u_lb[i][j][k][0]*ucmy+u_lb[i][j][k][1]*ucmx-ucmx*ucmy);
etacov[8]=rho*(u_lb[i][j][k][1]*ucmz+u_lb[i][j][k][2]*ucmy-ucmy*ucmz);
etacov[9]=rho*(u_lb[i][j][k][0]*ucmz+u_lb[i][j][k][2]*ucmx-ucmx*ucmz);
etacov[10]=0.0;
etacov[11]=0.0;
etacov[12]=0.0;
etacov[13]=rho*(u_lb[i][j][k][0]*u_lb[i][j][k][1]*ucmz+u_lb[i][j][k][0]*ucmy*u_lb[i][j][k][2]-
u_lb[i][j][k][0]*ucmy*ucmz+ucmx*u_lb[i][j][k][1]*u_lb[i][j][k][2]-
ucmx*u_lb[i][j][k][1]*ucmz-ucmx*ucmy*u_lb[i][j][k][2]+
ucmx*ucmy*ucmz);
etacov[14]=0.0;
}else{
etacov[0] = 0.0;
etacov[1] = rho*ucmx;
etacov[2] = rho*ucmy;
etacov[3] = rho*ucmz;
etacov[4]=rho*(2.*u_lb[i][j][k][0]*ucmx-ucmx*ucmx);
etacov[5]=rho*(2.*u_lb[i][j][k][1]*ucmy-ucmy*ucmy);
etacov[6]=rho*(2.*u_lb[i][j][k][2]*ucmz-ucmz*ucmz);
etacov[7]=rho*(u_lb[i][j][k][0]*ucmy+u_lb[i][j][k][1]*ucmx-ucmx*ucmy);
etacov[8]=rho*(u_lb[i][j][k][0]*ucmz+u_lb[i][j][k][2]*ucmx-ucmx*ucmz);
etacov[9]=rho*(u_lb[i][j][k][1]*ucmz+u_lb[i][j][k][2]*ucmy-ucmy*ucmz);
etacov[10] = 0.0;
etacov[11] = 0.0;
etacov[12] = 0.0;
etacov[13] = 0.0;
etacov[14] = 0.0;
etacov[15] = 0.0;
etacov[16] = 0.0;
etacov[17] = 0.0;
etacov[18] = 0.0;
}
for(int l=0; l<numvel; l++)
for(int ii=0; ii<numvel; ii++){
f_lb[i][j][k][l] -= w_lb[l]*mg_lb[ii][l]*etacov[ii]*Ng_lb[ii];
}
if(typeLB == 2){
double ****feqold = fix_lb_fluid->feqold;
double ****feqoldn = fix_lb_fluid->feqoldn;
density_old = 0.0;
u_old[0] = u_old[1] = u_old[2] = 0.0;
for(int l=0; l<numvel; l++){
density_old += feqold[i][j][k][l];
u_old[0] += feqold[i][j][k][l]*e[l][0];
u_old[1] += feqold[i][j][k][l]*e[l][1];
u_old[2] += feqold[i][j][k][l]*e[l][2];
}
u_old[0] = u_old[0]/density_old;
u_old[1] = u_old[1]/density_old;
u_old[2] = u_old[2]/density_old;
if(numvel==15){
etacov[0]=0.0;
etacov[1]=density_old*ucmx;
etacov[2]=density_old*ucmy;
etacov[3]=density_old*ucmz;
etacov[4]=density_old*(2.*u_old[0]*ucmx-ucmx*ucmx);
etacov[5]=density_old*(2.*u_old[1]*ucmy-ucmy*ucmy);
etacov[6]=density_old*(2.*u_old[2]*ucmz-ucmz*ucmz);
etacov[7]=density_old*(u_old[0]*ucmy+u_old[1]*ucmx-ucmx*ucmy);
etacov[8]=density_old*(u_old[1]*ucmz+u_old[2]*ucmy-ucmy*ucmz);
etacov[9]=density_old*(u_old[0]*ucmz+u_old[2]*ucmx-ucmx*ucmz);
etacov[10]=0.0;
etacov[11]=0.0;
etacov[12]=0.0;
etacov[13]=density_old*(u_old[0]*u_old[1]*ucmz+u_old[0]*ucmy*u_old[2]-
u_old[0]*ucmy*ucmz+ucmx*u_old[1]*u_old[2]-
ucmx*u_old[1]*ucmz-ucmx*ucmy*u_old[2]+
ucmx*ucmy*ucmz);
etacov[14]=0.0;
}else{
etacov[0] = 0.0;
etacov[1] = density_old*ucmx;
etacov[2] = density_old*ucmy;
etacov[3] = density_old*ucmz;
etacov[4] = density_old*(2.*u_lb[i][j][k][0]*ucmx-ucmx*ucmx);
etacov[5] = density_old*(2.*u_lb[i][j][k][1]*ucmy-ucmy*ucmy);
etacov[6] = density_old*(2.*u_lb[i][j][k][2]*ucmz-ucmz*ucmz);
etacov[7] = density_old*(u_lb[i][j][k][0]*ucmy+u_lb[i][j][k][1]*ucmx-ucmx*ucmy);
etacov[8] = density_old*(u_lb[i][j][k][0]*ucmz+u_lb[i][j][k][2]*ucmx-ucmx*ucmz);
etacov[9] = density_old*(u_lb[i][j][k][1]*ucmz+u_lb[i][j][k][2]*ucmy-ucmy*ucmz);
etacov[10] = 0.0;
etacov[11] = 0.0;
etacov[12] = 0.0;
etacov[13] = 0.0;
etacov[14] = 0.0;
etacov[15] = 0.0;
etacov[16] = 0.0;
etacov[17] = 0.0;
etacov[18] = 0.0;
}
for(int l=0; l<numvel; l++)
for(int ii=0; ii<numvel; ii++){
feqold[i][j][k][l] -= w_lb[l]*mg_lb[ii][l]*etacov[ii]*Ng_lb[ii];
feqoldn[i][j][k][l] -= w_lb[l]*mg_lb[ii][l]*etacov[ii]*Ng_lb[ii];
}
}
}
}
fix_lb_fluid->parametercalc_full();
}

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