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Old   November 17, 2003, 13:22
Default vof and small bubbles
  #1
frankastell
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hi everyone, i'm working with VOF to simulate the rise of air bubbles in water, but with small bubbles (d<2mm) it doesn't function. with the bigger ones every thing is ok. i try with and without surface tension. do you know if VOF has problems with small particles? thanks a lot.
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Old   November 17, 2003, 15:58
Default Re: vof and small bubbles
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Easycad
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Hi

Why dont you use DPM? I think it is more appropriate
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Old   November 18, 2003, 07:35
Default Re: vof and small bubbles
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mateus
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Hi!

Grid resolution might be a problem...do you have fine enough grid for so small particles? Maybe it's really better to work with DPM - it depends what you're interested in...

Regards

MATEUS
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Old   November 18, 2003, 07:52
Default Re: vof and small bubbles
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frankastell
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thank you for your attention!!!

i'm testing VOF for my thesis. i'm simulating bubbles with different diameters but always with 300 cells/bubble. i tried to simulate the small ones also with 900 cells/bubble but i didn't see any change in the rise velocity. the problem is that this kind of bubble accelerates just until 6 cm/s and it assumes a non spherical shape: in the reality, i.e. a 1 mm bubble is spherical and it has a terminal velocity near 30 cm/s. any idea? do i have to conclude that VOF isn't able to predict the comportment of this kind of particles? thanks a lot.

regards.
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Old   November 19, 2003, 03:10
Default Re: vof and small bubbles
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ROOZBEH
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Hi;

Dear mateus;

Whould you pay attention to my new message in this page!

Recently the new version of fluent is avalable for me. But I am working with it with no success! What settings are required in this new version.(modification pressure limit?_modification of termination criteria?_ ....)
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Old   December 11, 2003, 11:28
Default Re: vof and small bubbles
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richard
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hi, frankastell, what is the mean of 300cells/bubbles?is there 300 cells in a bubble?and what is the mean of terminal velocity? I don't catch what you say, would you please tell me more clearly?
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