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MusigFoam for complete evaporation

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Old   May 16, 2010, 13:20
Question MusigFoam for complete evaporation
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Robert Langner
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Hi foamers!

If I'm not on the wrong track:
- musigFoam is a multiphase Euler approach
- and Euler needs at least one continuous phase.

But needs Euler one (=always the same) continuous phase or just one (unspecific)?

For instance: If I might have a complete evaporation where the old liquid continuous phase breaks up but a new gas phase become persistent.
Do I receive reasonable results in that case or better use other approaches?

Thanks in advance,
Robert
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Old   May 16, 2010, 14:46
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Holger Marschall
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Hi,

Quote:
Originally Posted by Robat View Post
If I'm not on the wrong track:
- musigFoam is a multiphase Euler approach
- and Euler needs at least one continuous phase.
You are right

Quote:
Originally Posted by Robat View Post
But needs Euler one (=always the same) continuous phase or just one (unspecific)?
The problem does not lie in the method itself as it is based upon the concept of interpenetrating continua - a quite general concept. As such (a priori) the role of the phases is absolutely interchangeable. However, due to averaging you end up with unclosed terms in your governing equations which represent the interphase exchange of mass, momentum and such... And to model these unclosed terms reasonable you might want to base your model on the presumption that say phase a is disperse while b is continuous.

Quote:
Originally Posted by Robat View Post
For instance: If I might have a complete evaporation where the old liquid continuous phase breaks up but a new gas phase become persistent.
Do I receive reasonable results in that case or better use other approaches?
Generally I would say the Eulerian-Eulerian approach is the right one being the most flexible. However, flexibility comes at one price to pay: You need to model - appropriately and at best on a physical sound basis.

Do you consider this evaporation process starting within the bulk phase (homogeneous/heterogeneous nucleation)?

best,
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Old   May 17, 2010, 05:02
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Robert Langner
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Thanks for your quick reply.

Summed up: musigFoam is generally suitable for that but it's reasonable to define a continuous phase.

Quote:
Originally Posted by holger_marschall View Post

Do you consider this evaporation process starting within the bulk phase (homogeneous/heterogeneous nucleation)?

best,
My fluid heats from normal liquid to overheated gas. The evaporator is pretty complex shaped so I need to split the struktur an calculate it step by step. In result I can't presumpt the flow regime for every step and with it don't know which phase is locally continuous.


Besides that the micro scale seems to make me much more trouble. Yesterday I tried a shot in the dark but as I scaled down my mesh (to 4mm channel diameter): checkMesh shew me some inverted face pyramids as my cell sizes droped below 1Ám.

Are there any limits for cell sizes around Ám scale ?

Regards,
Robert
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