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blacksoil2012 November 27, 2013 18:11

Mixture model + VOF?
I noticed that in Fluent, you have to first choose which multiphase model you want to use: VOF, Eulerian, or mixture. Once selected, the remaining settings will be under that specified multiphase framework.

However, I'm wondering about the possibility of doing having more than one multiphase method in one simulation. For example, for an open-channel slurry flow, where I have air-water free surface, which is natural to use VOF; On the other hand, in slurry I have solid particles that tend to settle down. For the particle-water system, I would like to use mixture model.

What do I do?

Right now, I see I may just choose the mixture model, by specifying water as the primary phase, and air and solid particles as secondary phase, with the secondary phases all having a "diameter". Of course, for air this diameter value will be artificial. I haven't started the simulation so am not sure whether it works (mainly whether this all mixture multiphase approach will work to resolve the water-air free surface).

On the other hand, in CFX, it seems like that the mixture model can be used together with other multiphase models, since there the mixture model uses only one phase("variable composition mixture"), which comprises of several components. Corresponding to my case, the components there will be my particles of different size. And I can have another phase air, and the interaction between the air phase and this "variable composition mixture" phase can have the free surface model, while inside the variable composition mixture phase I can select the algebraic slip model. So in summary, CFX seems to be natural to combine the algebraic slip mixture model with any other multiphase model; WHILE in Fluent it seems that I cannot do that.

Anybody familiar with this can give some comments? I think my case is somewhat related with open-channel hydraulics and sedimentation.

Thank you very much and have a nice Thanksgiving!

Zaktatir November 30, 2013 08:51


that's a very interesting simulation you are now struggling with.

VOF mixutre are one fluid formulation and that's why not appropriate for flows where phases separates and interpentrate each other.

For your Case: The Full eulerian approach with zonal discretisation: there you select the order of your volume discretisation: 0- For slurry regions till 2 for free surfaces. There you may use the multi-Fluid-VOf approach

Look into zonal handling in the documentation: there you find a discreption..

mostafa_zeynalabedini February 9, 2014 00:59

hello all
I want to use two multiphase model in one simulation. I mean VOF for gas and mixture fluid to find the interface and mixture model for the mixture fluid. Is there any option in FLUENT or CFX to do that using the FLUENT own models?
I think also about using VOF as a Platform in solving and use UDS to model the mixture phase. But in this way I should develop a UDS for mixture model that could not be as good as FLUENT own model!

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