I wrote a udf file to calculate temperature gradient, But I recieved a fatal error....

I wrote this:

.

.

.

#include"udf.h"

#include"sg.h"

DEFINE_ADJUST(Direct, d)

{

int ID=10;

float T_i=300.0,T_f=500.0;

float ds, A_by_es, flux = 0.0;

float H_flux[1],A[ND_ND], es[ND_ND], dr0[ND_ND],GR[ND_ND];

face_t f;

cell_t c0,c;

Thread *t0, *t;

t = Lookup_Thread(d, ID);

begin_f_loop(f, t)

{

BOUNDARY_FACE_GEOMETRY(f, t, A, ds, es, A_by_es, dr0);

c0 = F_C0(f, t);

t0 = THREAD_T0(t);

GR[0]= C_T_RG(c0, t0)[0];

GR[1]= C_T_RG(c0, t0)[1];

flux += NV_DOT(GR, es);

}

end_f_loop(f, t)

H_flux[0] = (202.4*flux)/(T_f - T_i);

}