[AMitgM95]

How to implement mixture fraction formulation in reactingFoam?

[adhiraj]

I calculate mixture fraction using Bilger's formula in OpenFOAM 2.3.x, as here:

https://github.com/adhiraj-dasgupta/...ixtureFraction

Maybe you can use this utility as a guide?

[AMitgM95]

Dear Adhiraj

First of all thanks for the reply and the code.
I have implemented the mixture fraction formulation onto OpenFOAM code.

But now I want to add the conserved equation of the mixture fraction in the code, can you help me for that?

[adhiraj]

It should be easy top add an equation for mixture fraction (just a passive scalar), unless I am missing something.

Can you provide more details about what you are trying to implement, and if you are running into any errors?

[AMitgM95]

I want to add this particular conserved mixture fraction equation (without closing term) by replacing the species conservation equation.

https://drive.google.com/file/d/1BON...Q4Zyrtvff/view

[adhiraj]

This looks straightforward to implement. What errors did you get?

[AMitgM95]

as I told by replacing the species conservation equation

, so how to make it possible that is the main thing, means directly we need mixture fraction

[adhiraj]

There are tutorials available to add an equation for a scalar in OpenFOAM. For example, see here:

https://openfoamwiki.net/index.php/H...perature_field

Study this and then adapt it to your needs.

[AMitgM95]

I will try
Thanks.

[aurore_boreality]

Hi Adhiraj

Thank you for your utility. I adapted your code for OF-5.x, as attached.

What if I am considering premixed ch4/air combustion?
How must the fuel and oxidizer species be set in the dictionary?

Thanks,
Aurore

[adhiraj]

Does mixture fraction make sense for premixed flames?

[dscian]

There is a patch contribution of mixture fraction functionObject by a user in the issue tracking system of openfoam.org.


https://bugs.openfoam.org/view.php?id=3411

[aurore_boreality]

Originally Posted by adhiraj

Does mixture fraction make sense for premixed flames?

My initial idea was to qualitatively visualize the phase boundary between unburnt and burnt gaseous phase by the mixture fraction, as you proposed.

As expected, the utility calculates a more less uniform distribution in the combustion chamber.

Anyway, using the simple relationship Zst = 1/(1+phi) (phi denotes a local equivalence ratio) provided a proper estimation.

Thanks.
Aurore.

[adhiraj]

Originally Posted by aurore_boreality

My initial idea was to qualitatively visualize the phase boundary between unburnt and burnt gaseous phase by the mixture fraction, as you proposed.

I am a little confused here: what did I propose?

Also, how can mixture fraction determine whether the point is on the burnt-gas side or the fresh gas side? Isn't that the role of progress variable?

[aurore_boreality]

Originally Posted by adhiraj

I am a little confused here: what did I propose?

Also, how can mixture fraction determine whether the point is on the burnt-gas side or the fresh gas side? Isn't that the role of progress variable?

Maybe I did not express myself properly. I tried to visualize the burnt/unburnt boundary by means of the utility which you provided. But this is obviously not possible.

Progress variable is a good spot.

[HPE]

FYI: BilgerMixtureFraction function object.