[ChRiZZ]

Hi everyone!
I have a problem in UDF in steam conversion of methane. The problem in 2D, transient, when hydrogen appears and is carried away from the generation zone, an error occurs. Could you please suggest what is wrong with my UDF?

#include "udf.h"

#define A1 2.448e6
#define H1 1.165e8

DEFINE_VR_RATE(vol_reac_rate,c,t,r,wk,yk,rate,rr_t )
{
real ci, prod, K1, DEN;
int i;

if (!strcmp(r->name, "reaction-1"))
{
prod = 1.;

K1 = A1 * exp( - H1 / (UNIVERSAL_GAS_CONSTANT * C_T(c,t)));

if (yk[2]==0)
DEN = 1;
else
DEN = pow((1 + K1*wk[2]*yk[0]/(yk[2]*wk[0])),2.0);

for(i = 0; i < r->n_reactants; i++)
{
ci = C_R(c,t) * yk[r->reactant[i]] / wk[r->reactant[i]];
prod *= pow(ci, r->exp_reactant[i]);
}

for(i = 0; i < r->n_products; i++)
{
if (yk[r->product[i]]==0)
prod *= 1;
else
{
ci = C_R(c,t) * yk[r->product[i]] / wk[r->product[i]];
prod *= pow(ci, r->exp_product[i]);
}
}


*rate = r->A * exp( - r->E / (UNIVERSAL_GAS_CONSTANT * C_T(c,t))) *
pow(C_T(c,t), r->b) * prod / DEN;

*rr_t = *rate;
}
else
{

prod = 1.;
for(i = 0; i < r->n_reactants; i++)
{
ci = C_R(c,t) * yk[r->reactant[i]] / wk[r->reactant[i]];
prod *= pow(ci, r->exp_reactant[i]);
}
*rate = r->A * exp( - r->E / (UNIVERSAL_GAS_CONSTANT * C_T(c,t))) *
pow(C_T(c,t), r->b) * prod;

*rr_t = *rate;
}
}

Thank you, everyone.