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-   -   Problem with multiphase flow - mixture model (http://www.cfd-online.com/Forums/fluent/81269-problem-multiphase-flow-mixture-model.html)

 Mat22 October 21, 2010 10:38

Problem with multiphase flow - mixture model

Hello guys,

I am actually trying to model the flow in a stirred tank filled by two fluids with different density but very close 1.072 and 1.1), my final goal is to estimate the time needed to homogeize the two liquids.
First, I calculated the steady flow in the tank with one fluid.
And I patched the second liquid in the tank where i wanted and I run an unsteady simulation solving only the volume fraction equation. (It is very similar to introduce a dyer in a converged flow fiield i think)
The problem is that there is absolutely no change in the distribution of the two phases. I guess it comes from the resolution of the volume fraction equation
If someone could help me with this, it would be very nice.

Thanks

Mat

 thecfduser October 25, 2010 06:18

Hi
u must know that multiphase models do not account for mass diffusion of a liquid in another: the 2 phase are immiscible.

Tell me :
1-wich phase are u simulating first? the heavier or the lighter?
2-ure second phase, are u patching it on the top or on the bottom of the tank?
3-Wich multiphase modeling are u using?
4-Wich turbulence model?
5-Did u verify that ure flow is really unsteady?
6-Why dont u use lagrangian model ?

 Mat22 October 27, 2010 03:07

Hi,

Thank you for answering my questions.
I called the fluent hotline after and I was told that the multiphase-mixture model is not wrong for my problem but is not the most appropriate, so, i changed to multi-species model, which works quite well.
I was also told that the mixture model is more for two phases where one is made of small spheres and so the model takes care of the drag and so on.

Mat

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