[lvanlee]

It was a simulation about mold electromagnetic stirring in continuous casting.
I worked out the lorentz force from Ansys Maxwell, now I want to add the lorentz force as source terms using the DEFINE_SOURCE macro.
First, I got the cell centroid coordinates of the model mesh with the UDF.
#include"udf.h"
FILE*fout;float xx[ND_ND];

DEFINE_ON_DEMAND(get_coords)
{
Domain *domain;
face_t f; cell_t c;Thread *t;
domain=Get_Domain(1);
t=Lookup_Thread(domain,2);
fout=fopen("coordinates.out","w");

if (fout==NULL)
Message("Can't open the file");

else

{ begin_c_loop(c,t)

{ C_CENTROID(xx,c,t);
fprintf(fout,"%d %g %g %g\n",c,xx[0],xx[1],xx[2]);
}
end_c_loop(c,t)

fprintf(fout,"\n");
fclose(fout);
}
}
From this I get the coordinates.out, and I worked out the lorentz force on every coordinate as a constant.

Then I need to put the lorentz force on every coordinate as a momentum source.
This is the udf that I worte, but I don't know whether it could match the grids or not.(one-to-one correspondence)

#include "udf.h"
#define cnum 83325 /*number of cell*/
float fx[cnum],fy[cnum],cn[cnum],fz[cnum];
DEFINE_ON_DEMAND(getmagforce)
{ FILE *file;
int i;
file=fopen("lforce.txt","r"); /*external files*/
if (file==NULL)
{Message("Can't open file");}
else
{
for(i=1;i<=cnum;i++)

{ fscanf(file,"%f",&cn[i]);
fscanf(file,"%f",&fx[i]);
fscanf(file,"%f",&fy[i]);
fscanf(file,"%f",&fz[i]);
}
fclose(file);
}

}


DEFINE_SOURCE(x_momentum_source,c,t,dS,eqn)
{int m;
real source;
m=c+1;
source=fx[m];
dS[eqn]=0;
return source;
}

DEFINE_SOURCE(y_momentum_source,c,t,dS,eqn)
{int m;
real source;
m=c+1;
source=fy[m];
dS[eqn]=0;
return source;
}


DEFINE_SOURCE(z_momentum_source,c,t,dS,eqn)
{int m;
real source;
m=c+1;
source=fz[m];
dS[eqn]=0;
return source;
}

Plz help me! Thanks very much!