[BIANBOSHEN]

Dear all,
Now I am writing an UDF to define a energy source for cell that are adjacent to wall. The purpose is to add the heat transfer from wall to droplet in mist flow. Following is my UDF code. But after 12 iterations ，there is an error saying Error: > (greater-than): invalid argument : wrong type Error Object: 1.#inf.
I will be sincerely appreciate if you can solve my provblem.
Here is the code
DEFINE_SOURCE(liq_enrg_src, c, sec_th, dS, eqn)
{

Thread *mix_th, *pri_th, *t;
Domain *domain=Get_Domain(1);
int zone_ID=18;/*wall ID*/
real m_dot_d=0;
real kd;
real Cnt;
real a;
real Area[ND_ND];
real b;
real d;
real vg;
real Reg;
real tr;
real Enrg_Source=0;
face_t f;
mix_th = THREAD_SUPER_THREAD(sec_th);
pri_th = THREAD_SUB_THREAD(mix_th,0);
t=Lookup_Thread(domain,zone_ID);
begin_f_loop(f, t)
{
if(c == F_C0(f,t))
{
Cnt=(1.0-C_VOF(c,pri_th))*C_R(c,sec_th);
a=Cnt/C_R(c,pri_th);
if(a<0.3)
{
kd=0.18*sqrt(0.026/(C_R(c,pri_th)*0.008));
}
else
{
kd=pow(a,-0.85)*sqrt(0.026/(C_R(c,pri_th)*0.008));
}
m_dot_d=kd*Cnt;
vg=sqrt(pow(C_U(c,pri_th),2)+pow(C_V(c,pri_th),2)+ pow(C_W(c,pri_th),2));

Reg=C_R(c,pri_th)*vg*0.008/C_MU_L(c,pri_th);

d=0.00796*0.026/C_R(c,pri_th)/pow(C_VOF(c,pri_th)*vg,2)*pow(Reg,2/3)*pow(C_R(c,pri_th)/C_R(c,sec_th),-1/3)*pow(C_MU_L(c,pri_th)/C_MU_L(c,sec_th),2/3);

tr=3.14*sqrt(C_R(c,sec_th)*d*d*d/16/0.026);

b=pow(18*pow(C_K_L(c,pri_th)*tr,3)*C_R(c,pri_th)*L AT_HT*pow(m_dot_d,5)/pow(C_R(c,sec_th),4)/C_MU_EFF(c,pri_th)/(1.0-C_VOF(c,pri_th))/(F_T(f,t)-T_SAT),0.25);
F_AREA(Area,f,t);
Enrg_Source=(F_T(f,t)-T_SAT)*b/C_VOLUME(c,mix_th)/(1-C_VOF(c, pri_th))*NV_MAG(Area);
dS[eqn]=0;
//Enrg_Source=2;
return Enrg_Source;
}
}
end_f_loop(f, t)
}