Learning Forum

[Jiacheng lyu]

Hi, guys. Recently, I plan to define pre-exponential factors for limited rate reactions through UDF. The UDF can be compiled and mounted, but the reaction cannot proceed. Hoping to get the reason? The reactant is kerosene. The UDF code is as follows:

include "udf.h"
DEFINE_VR_RATE(rate_bfer,c,t,r,wk,yk,rate,rr_t)
{
/*If more than one reaction is defined, it is necessary to distinguish
between these using the names of the reactions. */
    if (!strcmp(r->name, "reaction-1"))
    {
        real ci, prod, er, pef_1;
        int i;
        er = (yk[r->reactant[0]] / wk[r->reactant[0]]) / (fabsf(yk[r->reactant[1]] / wk[r->reactant[1]]) + 1e-9);
        pef_1 = r->A * er;
            /* Calculate Arrhenius reaction rate */
        prod = 1.0;
        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]);
        }
        *rate = pef_1 * exp(- r->E / (UNIVERSAL_GAS_CONSTANT * C_T(c,t))) * prod;
        /* without pow(C_T(c,t), r->b)*/
        /* *rr_t = *rate;*/
    /* Reaction 1 */
    }
    else if (!strcmp(r->name, "reaction-2"))
    {
        real ci, prod, er, pef_2;
        int i;
        er = (yk[r->reactant[0]] / wk[r->reactant[0]]) / (fabsf(yk[r->reactant[1]] / wk[r->reactant[1]]) + 1e-9);
        pef_2 = r->A * er;
            /* Calculate Arrhenius reaction rate */
        prod = 1.0;
        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]);
        }
        *rate = pef_2 * exp(- r->E / (UNIVERSAL_GAS_CONSTANT * C_T(c,t))) * prod;
        /* without pow(C_T(c,t), r->b)*/
        /* *rr_t = *rate;*/
    /* Reaction 2 */
    }
}

[Rob]

If you add some message lines into the UDF are they triggered? You need to figure out if the UDF is doing something unexpected re the maths or if it's not working at all. 

[Jiacheng lyu]

I don't think the udf is working so I'm hoping to find the way to make it work. Any suggestions?

[Rob]

Add in some messages to see if it's triggering but not doing anything or not triggering etc.