[whelk123]

Hello, I am trying to model the heat transfer within a hydrogen fuel cell and I keep getting the message ACCESS_VIOLATION when I try applying my UDF.
#include "udf.h"
DEFINE_INIT(init_func,d)
{
Domain *d;
Thread *t;
real sum_diss=0.;
cell_t c;
d = Get_Domain(1);
}
DEFINE_SOURCE(sink_mass, c, t, dS, eqn)
{
real sink_mass;
sink_mass=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros);
return sink_mass;

}
DEFINE_SOURCE(energy_source, c, t, dS, eqn)
{
real energy_source;
energy_source=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros)*deltah/mh2;
return energy_source;
}
DEFINE_EXECUTE_AT_END(execute_at_end)
{
real step =RP_Get_Real("physical-time-step");
Domain *domain = Get_Domain(1);
int ID=2;
Thread *t =Lookup_Thread(domain, ID);
cell_t c;
begin_c_loop(c,t)
{
double temper,P,hsmp,lnpeq,Peq, dxdt;
temper=C_T(c,t);
P=(C_R(c,t)*rgp*C_T(c,t)/mh2)*0.00001;


hsmp= C_UDMI(c,t, 1 )*(HsMmaxprim-hsurm)+hsurm;
lnpeq=A-B/temper+C*hsmp+D*pow(tan(pi*hsmp/2.0/HsMmaxprim),n)+E*pow(tan(pi*hsmp/2.0/HsMmaxprim),(-m));
Peq=exp(lnpeq);
C_UDMI(c,t,0)=mh2*Ca*exp(Ea/(rgp*temper))*log(P/Peq)/0.0166;
C_UDMI(c,t,1 )=C_UDMI(c,t,1 )+C_UDMI(c,t,0)*step;
}
end_c_loop(c,t)
}

I have defined things but didnt think that was important. Can anyone please tell me what is wrong with this code!! It is fairly urgent!
Thank you for any help

[dmoroian]

You have to check if the pointers are valid and if you have enough user defined memory allocated:

 
...
if (N_UDM > 0)
  sink_mass=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros); 
else
  Error("Not enough UDM's defined!\n");
return sink_mass; 
 
} 
...
if (N_UDM > 0)
  energy_source=-C_UDMI(c,t,0)*rau0*0.0166*(1-poros)/mh2;
else
  Error("Not enough UDM's defined!\n")
return energy_source; 
...
int ID=2; 
Thread *t =Lookup_Thread(domain, ID); 
cell_t c; 
if(NULL == t)
  Error("No such thread!\n");
...  
if (N_UDM < 2)
  Error("Not enough UDM's defined!\n")
C_UDMI(c,t,0)=mh2*Ca*exp(Ea/(rgp*temper))*log(P/Peq)/0.0166; 
C_UDMI(c,t,1 )=C_UDMI(c,t,1 )+C_UDMI(c,t,0)*step; 
...

[whelk123]

Thanks for your help. I seem to have fixed the code but when I try and hook the function into the model, the sources do not appear in the hooking function box. Any ideas?
Thanks again!

[dmoroian]

Originally Posted by whelk123

...
when I try and hook the function into the model, the sources do not appear in the hooking function box.
...

Which "hooking function box" are you talking about?
I suspect you're looking in the wrong place. Check section 6.2.19 in the User Defined Function Manual to see how sources are hooked in fluent.

[whelk123]

I have been following the instructions, but when going into the assigning hooks where you assign inital_func etc not all of my functions are there. The heat source appears but the energy source does not.