[SARAHAVASHI]

hello everyone
i want to write a udf which explains the zeta potential by temprature as this equation :zeta potantial=-0.2*temprature-78.2
and then i want to replace it into this udf instead of ...
can anybody tell me how to write this and add to this part please
thank u a lot
#include "udf.h"

DEFINE_PROFILE(slip_ncond_x,face_thread,i)
// x velocity for non conductive wall
{
face_t f;
cell_t neig;
Thread *cell_thread;
Domain *domain = Get_Domain(1);
real vel,normal_magnitude,E_normal_x,E_normal_y,E_repai red_x,E_repaired_y;
real NV_VEC(A);
real mu=0.001003;
real eps0=8.85e-12;
real eps=80.1;
real zeta_p=..........;

//cell_thread=THREAD_T1(face_thread);
cell_thread=THREAD_T0(face_thread);

begin_f_loop(f,face_thread)
{
neig=F_C0(f,face_thread);
// Repair E component values............................................ .................................................. ...
F_AREA(A,f,face_thread);
//Message("x is %g\n", A[0]);

normal_magnitude=pow( pow(A[0],2)+pow(A[1],2),0.5);

if ( NULL != THREAD_STORAGE(cell_thread,SV_UDS_I(0)) && NULL != T_STORAGE_R_NV(cell_thread,SV_UDSI_G(0)) )
{
E_normal_x=ND_DOT(-C_UDSI_G(neig,cell_thread,0)[0],-C_UDSI_G(neig,cell_thread,0)[1],0,A[0],A[1],0)/pow(normal_magnitude,2)*A[0];
E_normal_y=ND_DOT(-C_UDSI_G(neig,cell_thread,0)[0],-C_UDSI_G(neig,cell_thread,0)[1],0,A[0],A[1],0)/pow(normal_magnitude,2)*A[1];

E_repaired_x=-C_UDSI_G(neig,cell_thread,0)[0]-E_normal_x;
E_repaired_y=-C_UDSI_G(neig,cell_thread,0)[1]-E_normal_y;
}
else
E_repaired_x = 0 ;
//.................................................. .................................................. ........................
F_PROFILE(f,face_thread,i)=-eps0*eps*zeta_p*E_repaired_x/mu;
}
end_f_loop(f,face_thread)
}