KR347: How do we post-process forward and backward rates of a reversible reaction in CFX.


A reversible Reaction can be set in CFX via two methods:

(a) Explicitly giving the forward and backward Rate
(b) Equilibrium Option

The `{Reaction}.Molar Reaction Rate` reported by CFX is the effective net rate (forward ` backward) for a reversible reaction. When the backward rate dominates it will be negative.

In the solver we currently only calculate the net rate.

If one needs to post-process forward and backward reaction rates separately, then the best solution is to setup the reversible reaction as two separate reactions; one forward and one backward. Of course, this is not possible when using the `Equilibrium` option for the backward rate.
However, this can be worked around as follows (need to do this for each reaction with equilibrium backward rate):

(1) Setup the desired reversible reaction with forward and backward reaction rates either via "Equilibrium option" or by explicitly giving the "forward and backward rates".
(2) Add a second `dummy` reaction, which is a copy of the first reaction but with the following differences:

- Set stoichiometric coefficients to zero for all reactants and products
- Make sure reaction orders are specified for all reactants (important!), if unknown set equal to stoichiometric coefficient.
- Disable the backward reaction rate by un-checking the box for `Backward Reaction Rate`

Because all stoichiometric coefficients in the `dummy` reaction are zero, it will not generate any source terms. However, a reaction rate will be calculated and written to the result file ` this reaction rate will be equal to the forward reaction of the `real` reaction.
The backward reaction rate can then be calculated as ({real reaction}.Molar Reaction Rate ` {dummy reaction}.Molar Reaction Rate).





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