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Incorporating pyrolysis Model in chtMultiRegionFoam

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Old   July 11, 2020, 05:04
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Kumaresh
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Hi,
As per your explanation above, you have just one domain/region. Fluid/solid interaction takes place inside one domain. In your case, the source of energy is from fluid, thereby pyrolysing the solid, release the energy from solid and interacts with fluid itself.

So, you need to fix appropriate governing equations for fluid model with heat source terms. --> (1)
Accordingly, use coupled boundary condition to transfer energy from fluid to solid --> (2)
the necessary equations inside solid model simulates pyrolysis and release exothermic heat to fluid--> (3)

Here (1) and (3) solves fluid and solid model
(2) - Interactions using boundary (but there are more realistic models for interactions)

In case of multiregion models, (1) and (3) will be solved in separate domains. For multiregion models, OpenFOAM was constructed with block matrices (separate blocks to solve separate set of implicit/explicit equations for solid and fluid models).
Think from application point of view please. Consider a heated rod (solid) in the atmosphere (fluid), convection into acccount - perfectly 2 regions - equs. are solved separately in 2 regions.
Another example as same as yours, pyrolysis in the domain - interactions between solid and released pyrolytic gases - here it cant be multiregion problem, because both solid and fluid matters are investigated in the same domain.

Hope you are clear now. If not, let me know please. Kindly look into the examples of reactingMultiphaseEulerFoam
Thank you
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Old   July 11, 2020, 07:52
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Armin Alavi
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Hi,
Thank you very much, I am looking up the test cases of the solver you mentioned. I think I get what you mean. You suggest that solid and fluid are the parts of one computational domain but treated as two separate phases, Am I right? I don't have the experience with two fluid models such as Eulerian model. I worked VOF model (interFoam) that solves an averaged equation. I think in two fluid models, two equation are solved and they are linked together via source terms of momentum, energy and mass. Although I didn't understand one part,
Quote:
Accordingly, use coupled boundary condition to transfer energy from fluid to solid --> (2)
Is this statement true if I use only one computational domain? Aren't boundary conditions the coupling element between two separate regions?
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Old   July 11, 2020, 12:12
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Hello Armin,
Quote:
You suggest that solid and fluid are the parts of one computational domain but treated as two separate phases
Yes you are right here. Since you worked with VOF model, you might have better exposure to work with multiphase flow. With this move ahead, learn OpenFoam techniques then and there, you will find a way for sure.

Quote:
Accordingly, use coupled boundary condition to transfer energy from fluid to solid --> (2)
Sorry, I'm wrong here. Coupled boundary condition can be used between 2 or more regions only. In case of multiphase (1 domain) problem, there are many interactions models, which you might have verified. Should chose the interaction model legitimately depending upon the problem type.
Thank you
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Old   July 12, 2020, 08:53
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Armin Alavi
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Hello Kummi,
Thank you very much. I have a lot to do and experience with the vision you gave me. I will try my best to put that in work.
Best regards,
Armin
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