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Eulerian + Multi-Fluid VOF Model + Species transfer

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Old   May 20, 2020, 11:44
Question Eulerian + Multi-Fluid VOF Model + Species transfer
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Hello all!


I am running a simulation in which I have a simple cube completely filled with water, except for a bubble of air I have patched in a corner.


Air is defined as a mixture (N2 + O2) and the water is defined as another mixture (N2+O2+H2O_liquid). The goal of the case is to simulate the species transfer setting a Henry constant and a diffusion coefficient, until the bubble completely dissapears.



It is working, but not quite as expected.


To develop the starting DAT file, I have made a patch and let it run without species transfer, so that the bubble would get the correct shape due to the contact angle and the surface tension.


Every cell has the variables of pressure, phase-1 velocities, phase-2 velocities, O2 and N2 fractions for the phase-1 (air), the phase-2 (water) fractions for O2, N2 and H2O(liquid), and the VOF values.



After letting the case run without species transfer, the N2 fraction in the water phase makes sense (it has the constant value in those cells where the water VOF is 1, and 0 in the rest). However, the N2 fraction in the air phase makes no sense (it has the constant correct value in those cells where the air VOF is 1, good, but in the rest it has a weird shape instead of being 0). See pictures.



Because how it develops once the species transfer is activated, I would say it has an impact, but I don't know.


The ultimate question is: can I simply don't care about the species values of air, in those cells where the water VOF value is 1, and viceversa?


And why when I try to patch the value that is wrong, it simply doesn't work????????? It stays all the same.


I hope you can bring some light to my dispair time...


Thanks in advance.


PS: The pictures of the case:


VOF


N2 in water


N2 in air - Wrong

Last edited by HHOS; May 20, 2020 at 11:51. Reason: Forgot about trying to patch.
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Old   May 29, 2020, 07:32
Default Multi phase- Multi species
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Hello,

I am a solving a multiphase multi-species problem with phase 1 has 4 species and phase 2 has 2 species. The species balance is defined by source terms and no reaction is defined.

One of the species in phase 2 is dependent on the concentration of a species in phase 1.

Please help me with how to extract a mass fraction of components from each phase specifically.

I have read the UDF manual but getting regular error. Used THREAD_SUB_THREADS(t); macro for defining it.



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Old   May 29, 2020, 09:39
Default Species Fraction
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Mass fractions of species are fetched using C_YI. The second argument of this macro is a Thread pointer. This pointer can point to either primary phase thread or secondary phase thread.
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Old   June 1, 2020, 09:33
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Quote:
Originally Posted by vinerm View Post
Mass fractions of species are fetched using C_YI. The second argument of this macro is a Thread pointer. This pointer can point to either primary phase thread or secondary phase thread.
Thank you for your reply.

I am trying the same way you have suggested. And I am hooking source term for each component in the corresponding phase under cell zone option. But getting error in the first iteration itself. Since one of the components in the secondary phase is depending on the mass fraction of a component in phase 1, Will this be the reason for the error? because when source term is hooked to a phase will it restrict the C_YI reading to that phase itself?
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Old   June 2, 2020, 16:41
Default Mass Fraction
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You have to provide Thread corresponding to the correct phase to C_YI. If the Thread belongs to secondary phase, then mass fractions from the secondary phase will be returned and if the Thread belongs to primary phase, then mass fractions from the primary phase will be returned.
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Old   June 9, 2020, 01:01
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Quote:
Originally Posted by vinerm View Post
You have to provide Thread corresponding to the correct phase to C_YI. If the Thread belongs to secondary phase, then mass fractions from the secondary phase will be returned and if the Thread belongs to primary phase, then mass fractions from the primary phase will be returned.
I have tried in the similar way. I have shared some details with you in PM . Please check once.


Thanks in advance
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