udf code:hydrogenation raction
 

Hai folks
I am new to this fluent UDF coding and I would like to write a UDF for energy source term for hydrogen absorption in metal hydride.
The equations used in this reaction are given below

ds=ρ_s⋅wt⋅(1-ε)([h+T_s (C_pg-C_ps )]/M_g )).dX/dt

dX/dt=C_a⋅(((p-p_eq ))/p_eq )⋅(exp((-E_a)/(R_g*T_s )))⋅2/3⋅((1-X)^(2/3)/(1-(1-X)^(1/3) ))

X=1-[1-√({C_a *(((P-P_eq ))/P_eq )*(e^(((-E_a)/(R_g*T_s )) ) )*t} )]^3

Peq=(h/(R_g T_s ))-(s/R_g )*〖10〗^5

I wrote udf but,,I found some errors when it interpreted .the udf code and errors are given, I really expect some advice...

#include "udf.h"

#define h -75000 //(J/mol)
#define s -135.6 //(J/mol.K)
#define Rg 8.314 //(J/mol.K)
#define Ca 2.9e8 //(1/s)
#define Ea 124 //(J/mol)
#define rho_s 1800 //(kg/m3)
#define epsilon 0.31
#define Cpg 14000 //J/(kg.K)
#define Cps 1545 //J/(kg.K)
#define por 0.5
#define wt 0.06
#define M_g 0.002 //kg/mol

DEFINE_ON_DEMAND(Pellet)
{
Domain *d;
int zone_id=5;
Thread *t = Lookup_Thread(d,zone_id);
cell_t c;
d = Get_Domain(1); /* Get the domain using ANSYS Fluent utility */
thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
C_UDMI(c,t,0) = 0;
}
end_c_loop(c,t)
}
}
DEFINE_ADJUST(ReactionR,d)
{
int zone_id=5;
Thread *t = Lookup_Thread(d,zone_id);
cell_t c;
real P_eq;
real dxdt;
real physical_dt;
real cond;
real ts;
real P;
ts=C_T(c,t);
P=C_P(c,t) /* get cell pressure */

thread_loop_c(t,d)
{
begin_c_loop(c,t)
{
P_eq=exp((h/(Rg*ts))- (s/Rg))*pow(10,5);
C_UDMI(c,t,1)=P_eq; /* calculate equilibrium pressure*/
cond=(P/C_UDMI(c,t,1))-1;
if(cond>0)
{
physical_dt=RP_Get_Real("physical time step")
C_UDMI(c,t,2)=1-pow((1-(sqrt(Ca*((P/C_UDMI(c,t,1))-1)* exp(-Ea/(Rg*ts)))* physical_dt)),3);/* calculate reacted fraction*/
dxdt=(2/3)*Ca*((P/C_UDMI(c,t,1))-1)*exp(-Ea/(Rg*ts))*((pow((1-C_UDMI(c,t,2)),(2/3)))/(1-(pow((1-C_UDMI(c,t,2)),(1/3)))));/* calculate reacted fraction*/
}
else
{
dxdt=0;
}
C_UDMI(c,t,3)=dxdt;
}
end_c_loop(c,t)
}
}
DEFINE_SOURCE(heat_generation,c,t,ds,eqn)
{
real q_a;
q_a=((rho_s*wt*(1-por)*(h+ (ts*( Cpg- Cps))))/ M_g)* C_UDMI(c,t,3);
ds[eqn]=0;
C_UDMI(c,t,4)=q_a; /* Memory allocation for storing 'heat generation' */
return q_a;
}

The errors are
1. line 46: parse error.
2. line 46: parse error.
3.c_loop_last: undeclared variable

Thank you

You missed the ; after P=C_P(c,t).

Do not use the // for comments in udf. Some compilers don't understand it. Only use /* */.

thanks for the reply.
I have changed the udf as per your direction but still experiencing one error.
Error: received a fatal signal (Segmentation fault).

Error: received a fatal signal (Segmentation fault).
Error Object: #f

any help??

Have you defined the UDM in fluent?

yes, I have assigned 4 udms.:confused:

You need 5 UDMs

(UDM-0, UDM-1, UDM-2, UDM-3, UDM-4)

Thank you.
I changed UDM to 5...but still error persists..:(

Are you sure that the zone_id is correct?

physical_dt=RP_Get_Real("physical time step")
Is also missing ;