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-   -   Two-Phase Homogeneous or Inhomogeneous model? (http://www.cfd-online.com/Forums/cfx/26536-two-phase-homogeneous-inhomogeneous-model.html)

 Miguel October 16, 2008 22:25

Two-Phase Homogeneous or Inhomogeneous model?

Hi

I'm simulating two-phase stratified flow with undefined interphase (interphase shape is part of the solution), but I`m confused about what model I must use: homogeneous or inhomogeneous model. I have read that homogeneous model is applicable to free surface flow, but I need to solve a transport equation for volumen fraction in order to tracking interphase shape, and homogeneous model isn't capable to do that.

Is the inhomogeneous model the right choise?

Miguel Baritto

 Glenn Horrocks October 17, 2008 00:22

Re: Two-Phase Homogeneous or Inhomogeneous model?

Hi,

The homogenous multiphase model does solve a VF equation. That's how it keeps track of the interface. The decision as to whether to use homogenous or non-h depends on whether there is an inter-phase slip. In free surface flow at any location the fluid is either one fluid or the other so homogeneous is suitable. If the phases mix but keep the same velocity field then homogeneous is still appropriate. Only if the phases mix and they have relative slip (eg bubbles going one way and water going another) do you go for inhomogeneous.

This is discussed in more detail in the documentation. Also note Rui (do a search on the forum) has found some exceptions to this which may or may not be appropriate to you.

Glenn Horrocks

 latslosh October 17, 2008 04:28

Re: Two-Phase Homogeneous or Inhomogeneous model?

Hi,

For a quick look on what might be the appropriate model, have a look at Christopher Brennen's book 'Fundamentals of Multiphase Flow' (do a google search - I think you can get it off the Caltech web site). Chapter 2.4 has got a few handy formulae for estimating if you need a homogeneeous or i-h multipahse model.

Cheers, latslosh.

 Miguel October 17, 2008 14:30

Re: Two-Phase Homogeneous or Inhomogeneous model?