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How to compute surface area of rising bubble

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Old   January 10, 2014, 09:52
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  #21
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Nazanin
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Originally Posted by Andrea_85 View Post
Hi all,

i guess that the total interfacial area can be simply calculated using:

\Sum_i=1:N \grad\alpha_i * \deltaV_i

where N is total numer of cells in your domain. This gives you an area in m^2, so if your case is 2-D and you just need the lenght of the interfacial line you have to normalized by the thickness.

This is consistent with the CSF method implemented in interFoam.

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andrea
Thank you very much for reply andrea..
Do you know how I can determine changing bubble diameter during run and relative velocity??
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Old   January 10, 2014, 10:06
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Hi,

supposing that your bubble remains a sphere (or circle in 2-D) and does not deform then if you have the surface area you can calculate the radius(diameter) using area formulas

2-D -> 2*Pi*R = surfaceArea/thickness
3-D -> 4*Pi*R^2 = surfaceArea

and what do you mean with "relative velocity"? Is it the mean rising velocity?
If yes, you can for example calculate the mean velocity of the center of mass which gives you the mean velocity of the rising bubble.

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Old   January 10, 2014, 10:17
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Quote:
Originally Posted by Andrea_85 View Post
Hi,

supposing that your bubble remains a sphere (or circle in 2-D) and does not deform then if you have the surface area you can calculate the radius(diameter) using area formulas

2-D -> 2*Pi*R = surfaceArea/thickness
3-D -> 4*Pi*R^2 = surfaceArea

and what do you mean with "relative velocity"? Is it the mean rising velocity?
If yes, you can for example calculate the mean velocity of the center of mass which gives you the mean velocity of the rising bubble.

best

andrea
Thank you very much.
If I want use your idea,should I writing code for my solver or I can use swak4foam?
relative velocity means:
that Ux Uy Uz is bubble velocty and Ul is local liquid velocity...
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Old   January 10, 2014, 10:36
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It depends what you want to do with diameter and velocity. Do you need them during the simulation, because for example they appear in some new equations you are solving or you just need them in the post-processing?
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Old   January 10, 2014, 10:44
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Originally Posted by Andrea_85 View Post
It depends what you want to do with diameter and velocity. Do you need them during the simulation, because for example they appear in some new equations you are solving or you just need them in the post-processing?
I want plot these parameters after simulation (post-prosessing) ..
I found in swak4Foam examples (capilaryRise-test case) that use simpleSwakFunctionObjects and swakFunctionObjects for compute some parameters like this but I dont know how determine for my case study??
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Old   January 12, 2014, 06:12
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Andrea Ferrari
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Hi,

i think the best would be write your own script that does all the calculations. Have a look in application/utilities/postprocessing.
There you have a lot of examples. You can modify the main part of one of those to read the correct quantities and print what you need.


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Old   January 22, 2014, 20:14
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Quote:
Originally Posted by Nazanin View Post
I want plot these parameters after simulation (post-prosessing) ..
I found in swak4Foam examples (capilaryRise-test case) that use simpleSwakFunctionObjects and swakFunctionObjects for compute some parameters like this but I dont know how determine for my case study??
I'm still unsure what the actual problem is:
- you have already done the simulation and want to do the calculation on the data on disc: funkyDoCalc might help you there (it can do all the things swakExpression can do)
- or you want to use swakExpression and are unclear about the actual expressions to use?
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