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ScalartranportFoam solving with chemical reaction

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Old   March 13, 2017, 02:43
Default ScalartranportFoam solving with chemical reaction
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Dear Foamers,

i have some trouble with solving the scalar transport equation in conjunction with a chemical reaction in the concentration field.

The simulation task sketches as follows:
Two Species are transported along a computational domain. When some amount of species A touches Species B a chemical reaction (sink in the concentration field) takes place. The simulation works for moderate Diffusion and chemical reaction strength. When the reaction strength is rised, the simulation is still stable, but there are heavy unphysical oscillations inside the domain. The oscillations come along the conncection lines with the underlying blocks of the block structured mesh.

The code is actually working, so in my opinion is seems like i took the wrong options for the simulation.

A picture of the error and of the used descritization schemes is included.

Has anyone a hint, how what could be the problem?

Regards

Christian
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Old   March 17, 2017, 03:19
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Hi Christian,

in which way you modeled the reaction? Is the sink term modeled as some reaction rate times the concentration (e.g. r_c*C, with C the concentration)?
Am I correct that the reaction rate is only non-zero at the interface?
If this is the case, you might have large jumps in the coefficients at the interface (when you switch on reaction) and this jumping coefficients can cause oscillations.

I started to model flow through a porous medium.
Here the resistance is added as source term in part of the domain. porousSimpleFoam produces velocity oscillations around the interface (see e.g. https://bugs.openfoam.org/view.php?id=134 ).

Therefore I guess that you might get the same problems with oscillations at your interface. I don't know if those oscillations at interface are a general problem of openFOAM. Maybe some more experienced user can give here more insight.

Regards

Sebastian
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chemical reactions, mass transfer, numerical error

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