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-   -   VOF in CFX (http://www.cfd-online.com/Forums/cfx/97226-vof-cfx.html)

talebzarei February 12, 2012 16:20

VOF in CFX
 
I wanna to use from VOF framework in my gas-liquid system simulation but I couldnt active VOF in CFX software. How can I active VOF in CFX pre?. What should I do in Defult domain?

ghorrocks February 12, 2012 18:01

Do the tutorial on free surface flow over a bump - this will show how to set up VOF style simulations.

talebzarei February 13, 2012 16:10

Thanks
I will read this tutorial

aximefu February 25, 2012 23:04

Quote:

Originally Posted by ghorrocks (Post 344040)
Do the tutorial on free surface flow over a bump - this will show how to set up VOF style simulations.

Then which one is about the euler-euler model? Thanks!

ghorrocks February 26, 2012 05:10

Can't remember off the top of my head (I do not have CFX in front of me). Just go through the contents page of the tutorial documentation and the eular-eular examples should be obvious.

aximefu February 26, 2012 09:03

Quote:

Originally Posted by ghorrocks (Post 346325)
Can't remember off the top of my head (I do not have CFX in front of me). Just go through the contents page of the tutorial documentation and the eular-eular examples should be obvious.

OK, I will find it out.
Another question: do you have some material about the difinition and distinguish of eular-eular、VOF or Euler lagrange or where I can download some?
Recently, I am working on phase change in heat pipe, and confused about the models used in CFD multiphase flow simulation.
Thanks!

ghorrocks February 26, 2012 18:04

I think the documentation has comments on selecting multiphase models. Try the modelling one.

The line between the multiphase models is blurry and for many models a number of multiphase approaches will work.

* Free surface modelling + homogeneous equations - two or more phases have a resolvable interface and never mix at a scale smaller than the mesh.
* Free surface modelling + inhomogeneous equations - two or phases have a resolvable interface but sometimes mix at a scale smaller than the mesh.
* Eular-Eular modelling - No resolvable interface so all mixing is at a scale smaller then the mesh.
* Particle tracking - individual phase bits (eg sand, bubbles in water, droplets in air) can be tracked in the continuous phase as a discrete particles.

Note the mesh size comes into the choice - whether the phases are mixed at a level you mesh can resolve. This means you have to be careful with mesh refinement studies and excessive mesh refinement as you may change the regime you are operating in.

aximefu March 2, 2012 03:46

Quote:

Originally Posted by ghorrocks (Post 346370)
I think the documentation has comments on selecting multiphase models. Try the modelling one.

The line between the multiphase models is blurry and for many models a number of multiphase approaches will work.

* Free surface modelling + homogeneous equations - two or more phases have a resolvable interface and never mix at a scale smaller than the mesh.
* Free surface modelling + inhomogeneous equations - two or phases have a resolvable interface but sometimes mix at a scale smaller than the mesh.
* Eular-Eular modelling - No resolvable interface so all mixing is at a scale smaller then the mesh.
* Particle tracking - individual phase bits (eg sand, bubbles in water, droplets in air) can be tracked in the continuous phase as a discrete particles.

Note the mesh size comes into the choice - whether the phases are mixed at a level you mesh can resolve. This means you have to be careful with mesh refinement studies and excessive mesh refinement as you may change the regime you are operating in.

Thank you for your answer!
I have read the Help file for CFX,and I think the model -free surface modeling+ inhomogeneous model you mentioned is equivalent to particle model or mixture model, so which model in cfx is equivalent to the model "eular-eular modeling"?
Do you know something about it? If you do, pls tell me. Thanks!

PS:
In Fluent, There are two Multiphase Models:Euler-lagrange model and Euler-euler model. Euler-euler model has three sub-model: VOF, mixture and euler, corresponding to specific different settings.
Is there have the similar sketch of Multiphase models in CFX?

ghorrocks March 2, 2012 07:54

I have no idea what the Fluent terms are referring to. I will leave it up to you to compare the documentation and see which options are equivalent.

aximefu March 2, 2012 10:26

I will have a try!

Gandhi March 28, 2012 04:42

Multi phase combustion using CFX
 
How to do Homogeneous chemical reaction in cfx
like when liquid sodium reacts with water vapour hydrogen bubble is generated, it has to to be separate phase. plz help me in doing this in CFX or Fluent

ghorrocks March 29, 2012 05:53

I think you will have to ask CFX support for an example file of this sort of simulation.


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