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Microchannel flow interfoam. (results far away from theoritical answers)

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Old   June 15, 2015, 10:03
Default Microchannel flow interfoam. (results far away from theoritical answers)
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Hi Foamers;

I am using interfoam solver for a studying microchannel flow application case. I started with the paper of Duong, M. Kreutzer et al which looks like a simple basic case. Even they make use of the general interFoam but an older version (1.6 or so).

In their paper they plot an interesting graph between the Ca number and the thickness of the lubricating film. (i.e theres a relation between the thickness of the lubricating film and the flow velocity). Irrespective of the lubricating film thickness, I get a constant value(4.7e-7 microm) for a specific velocity. My Ca = 0.01 which is quite high.

I used the same sort of grid refinement and all values as described in the paper but their values are much closer to the theoretical values unlike mine which is 3 micrometers.

Are anyone working over this topic? I even tried to reduce the concentration of the bubble to see if the thickness matches but always it just has a very small lubricating thickness and this is far from theoretical value.

Attached are some files related to the simulation results and theoretical values. If anything fishy I will keep updated.

Any help would be highly appreciated.

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File Type: jpg figure2.jpg (42.0 KB, 43 views)
File Type: jpg figure3.jpg (15.6 KB, 42 views)
File Type: jpg figure4.jpg (16.9 KB, 31 views)
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Old   June 24, 2015, 12:09
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hi Foamers;

MAy be this could be something useful for others working with micro-channel flows.
Well, i was quite tired of working with this and the best way is to get back to the very first step.

So, the first step:
I considered both fluids are of same phase.
Example: water drop in carrier water system and carried out several simulation. The results are in good agreement with the numerical and also physical behaviors. Here, though both fluids are seen as same phases i introduce a very small amount of surface tension to have a Ca number. Else it would be infinite and useless for comparison.

Later, as this is perfect with the 1phase system i extended this to the 2phase system.

Then i found a silly rather precious mistake with the fluid being injected.
NOTE: In this step the setFieldsDict and the injection of required fluid under analysis should be checked thoroughly. Else you interchange the results and get the exact opposite behavior.

Now, an interesting finding for either a 1phase or 2phase system is that, your lubricating film thickness varies because of 3 factors, viscosity, velocity and surface tension. {even gravity but i make analysis over e-6m channels so, i always neglect it}.

How do you resolve the cells in order to get the accurate results? Either go for very fine cells(problems with spurious currents) and very high computational cost or take local refinement(as mentioned in many papers) and get closer to accuracy? {What is the use of local refinement when lubricating film thickness is large?}

I tried dividing the domain into several blocks and carry over the experiments but none works well for very high Ca numbers.

Maybe if anyone has an idea i would be happy if you share it else if i find something interesting i will keep updated.

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