[Nia]

Hello everybody,

I am currently trying to use the DEFINE_VR_RATE to simulate CO2 dissociation in water, but it does not seem to work.

I have a 2D eulerian simulation with :

• (CO2+air) mixture velocity inlet that provide gazeous co2 as secondary phase;
• (H2O(l) + CO2(l) + H+ + HCO3-) mixture as primary phase;
• A non-linearized mass transfer UDF adapted from DEFINE_MASS_TRANSFER (which is working) to input the co2 transfer from gas phase to liquid phase respecting the Higbie model.

The next step of my simulation is to describe the dissociation of CO2 (aq) to H+ and HCO3-. I tried to realize this step with the DEFINE_VR_RATE as follow :

DEFINE_VR_RATE(CO2_reaction2, c, t, r, mole_weight, species_mf, rate, rr_t)
{

real yco2  = species_mf[0];        /*  molar fraction of CO2     */
real yHCO3 = species_mf[1];     /*  molar fraction of HCO3- */
real yH    = species_mf[2];       /*  molar fraction of H+      */

real Mco2  = mole_weight[0];     /*  molar mass of CO2        */
real MHCO3 = mole_weight[1];  /*  molar mass of HCO3-    */
real MH    = mole_weight[2];    /*  molar mass of H+         */

real Kco2, Kd, a; 
real vofl= C_VOF(c,t); 
real vofg=1-vofl;
 
Kco2   = 3.665e-02; 
Kd     = 74866.11;

a =(C_R(c,t)*yH/MH)*gamma;   /*  activity of H+  */  

  	
*rate = Kco2*C_R(c,t)*yco2/Mco2 - Kd*a*(C_R(c,t)*yHCO3/MHCO3);

*rr_t = *rate; 

  
}

The problem is that the H+ and HCO3- concentrations do not vary over time when this udf is compiled, even from visual studio prompt.

Maybe my mistake is my understanding of this function, and maybe it should be coupled with the DEFINE_SOURCE function?

If any one have any idea..

Thank you.

[Nia]

Hi everybody,

In case this situation would happen again, here is the error in my simulation: the mixtures were based on "inert mixture" rather than on "template mixture", which prevented the reaction from taking place. The latter having been renamed since, the error was not obvious...
Hopefully this will help other people.