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volume force on dispersed phase only?

Posted 23 févr. 2010, 09:41 UTC−5 Version 4.0a 7 Replies

David Roos Launchbury
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hi everyone

i am relatively new to comsol and ran into a perhaps simple problem:

i'm simulating a two-phase mixture model in the chemical engineering module. i want the dispersed solid phase to be influenced by a volume force from another physics model.

if i specify that force in the physics tab of my mixture subdomain, obviously the entire fluid is influenced by this force (same if i apply gravity). is it possible to specify that force so that only the dispersed phase is influenced and not the continuous phase?

any help would be greatly appreciated.

greetings
dave
7 Replies Last Post 2 juil. 2013, 17:20 UTC−4
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Hello David Roos Launchbury

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Ostahie Narcis
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Posted: 1 decade ago 11 févr. 2011, 03:48 UTC−5
Hi!

I am interested about the same problem. Have you solved with the subdomain force for mixture?

Thanks!
Narcis
Hi! I am interested about the same problem. Have you solved with the subdomain force for mixture? Thanks! Narcis
Osameh Ghazian
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Posted: 1 decade ago 14 mars 2011, 10:24 UTC−4
hi

I have the same problem. I want to simulate water droplet in oil with the gravity force just applied to the water droplet.
how can i do this ??
hi I have the same problem. I want to simulate water droplet in oil with the gravity force just applied to the water droplet. how can i do this ??
Ostahie Narcis
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Posted: 1 decade ago 15 mars 2011, 02:29 UTC−4
There is an example for gravity, for particle sedimentation. Look on Comsol model library. Removing Contaminants in a Secondary Sedimentation Clarifier.
There is an example for gravity, for particle sedimentation. Look on Comsol model library. Removing Contaminants in a Secondary Sedimentation Clarifier.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 15 mars 2011, 04:40 UTC−4
Hi

I'm not sure I fully understand your issue (I do not have any geo-science module) but if you apply a body load you give the formula for a mesh element item of size dx*dy*dz, hence "solid.rho*g_const" in [N/m^3] for a gravity load (density) in structural

Now your "solid.rho" is to be understood as a "solid.rho_i(x,y,z)", where the subscript "_i" stands for the specific geometrical Element index, and the (x,y,z) is the field representation, as the density is not necessarily constant in the model over a given volume.

So if you have two fractions of material you need to add a Boolean or a "ratio" value to the equation to get it to only consider the desired item(s) inside the mesh element

--
Good luck
Ivar
Hi I'm not sure I fully understand your issue (I do not have any geo-science module) but if you apply a body load you give the formula for a mesh element item of size dx*dy*dz, hence "solid.rho*g_const" in [N/m^3] for a gravity load (density) in structural Now your "solid.rho" is to be understood as a "solid.rho_i(x,y,z)", where the subscript "_i" stands for the specific geometrical Element index, and the (x,y,z) is the field representation, as the density is not necessarily constant in the model over a given volume. So if you have two fractions of material you need to add a Boolean or a "ratio" value to the equation to get it to only consider the desired item(s) inside the mesh element -- Good luck Ivar
Certified Consultant
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Posted: 1 decade ago 15 mars 2011, 05:19 UTC−4
If you have gravity as the driving force for phase separation, the sedimentation example is the right way to go, as Osahie correctly points out. The COMSOL Mixture Model in the CFD module has built-in functionality for this (through the Hadamard-Rybczynski or Schiller-Naumann slip models).

If you however want another physical force than gravity on one of the phases you have to set "Slip-model: User defined", and type in your own force model.

--
Niklas
If you have gravity as the driving force for phase separation, the sedimentation example is the right way to go, as Osahie correctly points out. The COMSOL Mixture Model in the CFD module has built-in functionality for this (through the Hadamard-Rybczynski or Schiller-Naumann slip models). If you however want another physical force than gravity on one of the phases you have to set "Slip-model: User defined", and type in your own force model. -- Niklas
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 15 mars 2011, 05:46 UTC−4
Hi Niklas

That is what I expected, in the geo-science you have some nice advanced models set-up in your physics.

There were some similar question raised at the last Paris conference from a Norwegian COMSOL user, hope he is listening too ;)

-
Good luck
Ivar
Hi Niklas That is what I expected, in the geo-science you have some nice advanced models set-up in your physics. There were some similar question raised at the last Paris conference from a Norwegian COMSOL user, hope he is listening too ;) - Good luck Ivar
Herek Clack
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Posted: 1 decade ago 2 juil. 2013, 17:20 UTC−4
Thanks so very much for this insight. I'd gotten quite far down a model development path carrying the implicit assumption that I could apply a variety of forces in the mm module similarly to the fpt module. Nearly had a heart attack when I saw that I couldn't, but this resolves the issue.

Most valuable post I've found so far on the COMSOL forums. If there isn't already, there should be an "FAQ" or "Expert Knowledge Base" area of the site for such valuable posts.

+1

HC
Thanks so very much for this insight. I'd gotten quite far down a model development path carrying the implicit assumption that I could apply a variety of forces in the mm module similarly to the fpt module. Nearly had a heart attack when I saw that I couldn't, but this resolves the issue. Most valuable post I've found so far on the COMSOL forums. If there isn't already, there should be an "FAQ" or "Expert Knowledge Base" area of the site for such valuable posts. +1 HC

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