Discussion Forum

Hello,

I need to know if I can add a starting concentration for a variable in the Reacting Flow in Porous Media, that will then change via the Reactions Node. The Initial Values Node does not seem to do that.. does anyone know if there is another way to give a domain an initial value?

I am trying to simulate 2 reactions occurring in a packed bed- the consumption of a chemical (ac), and the growth of the biomass that is consuming the chemical (ac).
There are 2 reactions:

R_ac = -k_rate*X*(ac/(ac+K_ac))
R_X = Y*-rfds.R_ac-(m*X)

where k_rate, K_ac, Y, and m are constants. The consumption of the chemical, ac, is dependent on the concentration of biomass, and the growth of the biomass depends on the rate of ac consumption. Is there a way to implement this successfully?
Also in case of negative concentration I introduced a variable B = max(eps^2,X) , which I used in my reactions in place of X.
The R_ac, R_X, and X go to essentially zero (e-38). I added an initial concentration for the X but it did not seem to matter. I would like to somehow add a starting concentration of biomass to the domain of the model, but cannot see a way to do that since the initial conditions node does not seem to do that.
One thing that does give me reasonable numbers is to set one of the boundaries with a constant concentration using the concentration node within reacting flow in porous media, but then that boundary will not change with the rest of the model. I would prefer NOT to take this route.

Do you have any other suggestions of advice on how to do this?
Thank you,
Kelley Rabjohns