UDF memory assignment
 

Hello,

In Fluent I'm trying to move a wall by saying that the new wall position should be an old wall position plus a deformation. The UDF is below. However, I can't get Fluent to read in the node positions or displacements correctly.

For example for the position of node 86 which is specified by this line in the file "node_original.txt": 86,4.539341e-03,2.096552e-03,1.979483e-01 Fluent tells me the position is: 86,1.098238e-21,2.626260e-24,1.243272e-08

And for a displacement in the file "disp.txt" which should be: 6.980200e-06, 7.436000e-08, -6.986600e-07 Fluent says it is: 3.673734e-44, 4.929700e-60, -2.875845e-52

I think this has something to do with the way the variable type has been declared at the beginning of the function or the way the type has been declared when the files are read in. But I really can't figure out what is wrong.

I'm working in double precision.

Any advice would be much appreciated!

Thanks, Kate

DEFINE_GRID_MOTION(grid_motion,domain,dt,time,dtim e) { int j; int i; int n; FILE *fd;

real dx[1202]; real dy[1202]; real dz[1202]; int a[7147]; real x[7147]; real y[7147]; real z[7147]; face_t f; Thread *thread = DT_THREAD(dt); Node *v;

char filename[20]; memset(filename,21,0);

sprintf(filename,"disp.txt");

fd = fopen(filename, "r");

for (j=1; j<1202; j++)

fscanf(fd,"%e, %e, %e\n", &dx[j], &dy[j], &dz[j]);

fclose(fd);

printf("%e, %e, %e\n", dx[1], dy[1], dz[1]);

fd = fopen("node_original.txt", "r");

for (j=1; j<7147; j++)

fscanf(fd,"%d,%e,%e,%e\n", &a[j], &x[j] ,&y[j], &z[j]);

fclose(fd);

printf("%d,%e,%e,%e\n", a[1], x[1] ,y[1], z[1]);

i = 0;

begin_f_loop (f, thread)

{

f_node_loop (f, thread, n)

{

v = F_NODE (f, thread, n);

i = i+1;

NODE_X(v) = x[i] + dx[a[i]];

NODE_Y(v) = y[i] + dy[a[i]];

NODE_Z(v) = z[i] + dz[a[i]];

}

}

end_f_loop (f, thread)

}