[ADI]

Hello All,
I am fairly new to using UDF along with Fluent. I am trying to model reduction of CO2 with coal or Carbon. The reation rate is defined using Langmuir-Henselwood formulation and I am trying to do that with the UDF because most of the Species Transport models use the Arrhenius rate equation.

My question is, how do I use concentrations of the species' as my variable in the code.

Here is the code I have so far (fairly simple and premature):


#include "udf.h"

#define K 1000
#define K2 0.508
#define Mtot 84.

DEFINE_VR_RATE(lang_hens_reac_rate,c,t,r,mole_weig ht,species_mf,rate,rr_t, yi)
{
real s1 = species_mf[0];
real s2 = specief_mf[1];
real mw1 = mole_weight[0];
real mw2 = mole_weight[1];

if (FLUID_THREAD_P(t) && THREAD_VAR(t).fluid.porous)
*rate = K2*mw1/(1+K*(mw1+mw2));
else
*rate = 0.;

*rr_t = *rate;
}

However, all the mw variables need to be concentrations. Please help me as soon as possible as I am running out of ideas and options

I found this piece of code that people are using to obtain concentration:

ci = yi[dindex][sp_id]*C_R(c,t_reactant)/mw[dindex][sp_id];
ci = MAX(ci,SMALL_S);

But i have no idea what all those arguements and variables and syntax are. Please help

The basic equation for calculating the reaction rate is:
rate = K2*[species 2]/(1+K*([species1]+[species2]))

where K and K2 are constants given and the objects in the square brackets are obviously concentrations that I need.