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paritition coefficient

Posted 2011年1月18日 GMT-5 13:51 Computational Fluid Dynamics (CFD), Chemical Reaction Engineering, Parameters, Variables, & Functions, Studies & Solvers Version 4.1 2 Replies

Melissa Rice
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Hello all

I was wondering, how can I implement a partitioning of a dependent variable (say concentration) at the internal boundary of two assemblies. For example c1=2*c2 where c1 is concentration in domain 1 and c2 in domain 2. I tried using identity pair/contact pair but it seems to be in vain. Any suggestions will be greatly appreciated

thanks
2 Replies Last Post 2011年1月18日 GMT-5 17:17
Melissa Rice
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Posted: 1 decade ago 2011年1月18日 GMT-5 14:36
I managed to find a solution. I did not want to delete the post since it might be helpful to others out here. If you want to partition the variable at the interface of the two domains, you need to force the flux to be continuous by declaring boundary conditions using the stiff spring method. Therefore the flux in the first domain will be N=M*(c2-K*c1) and the flux in the other domain would be N=M*(Kc1-c2), where K is the partition coefficient and M is a (nonphysical) velocity large enough to let the concentration differences in the brackets approach zero. There is a model example called "dialysis" under separation processes. It is very clearly mentioned in that file.
I managed to find a solution. I did not want to delete the post since it might be helpful to others out here. If you want to partition the variable at the interface of the two domains, you need to force the flux to be continuous by declaring boundary conditions using the stiff spring method. Therefore the flux in the first domain will be N=M*(c2-K*c1) and the flux in the other domain would be N=M*(Kc1-c2), where K is the partition coefficient and M is a (nonphysical) velocity large enough to let the concentration differences in the brackets approach zero. There is a model example called "dialysis" under separation processes. It is very clearly mentioned in that file.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2011年1月18日 GMT-5 17:17
Hi

I'm not a "chemistry module" expert, but isnt there a flux discontinuity BC doing what you want ?
it's for internal boundaries I suppose in union mode, but if you take a look at the equations you might find out how to define your assembly BC

And then there is a pair-flux discontinuity for assembly mode too

But if you have 2 species, can you linked them ? I'm havent tried those physics for quite some time, and not in v4 anyhow, cannot propose more
--
Good luck
Ivar
Hi I'm not a "chemistry module" expert, but isnt there a flux discontinuity BC doing what you want ? it's for internal boundaries I suppose in union mode, but if you take a look at the equations you might find out how to define your assembly BC And then there is a pair-flux discontinuity for assembly mode too But if you have 2 species, can you linked them ? I'm havent tried those physics for quite some time, and not in v4 anyhow, cannot propose more -- Good luck Ivar

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