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-   -   Bubble!!!!!!!!!!!!!!!!!!! help me (http://www.cfd-online.com/Forums/fluent/101824-bubble-help-me.html)

adambarfi May 15, 2012 05:46

Bubble!!!!!!!!!!!!!!!!!!! help me
 
Hi everybody,

I want to analyze the bubble growing in a liquid.

please help me what should I do? and what is the mechanism of dynamic meshing? can I use dynamic meshes for this problem?How?

I want to compare my results with the results of Rayleigh-Plesset Equation.

thank you.

adambarfi May 21, 2012 04:49

Is here anybody answer my question??!?!?!?!? please.

ghost82 May 21, 2012 05:13

Hi adambarfi,
In the past I tried the simulation of a single water-vapor bubble imploding in water under constant pressure (2D simulation, axisymmetric).
It's not that easy...I tried to simulate the implosion with VOF model, by paching the liquid domain with a semicircle of vapor (d=100 micron), but my resuts were not good..
Attention has to be paid to the grid, it has to be very refined at the liquid-solid interface, as the gradients are very large.
I read that Matevz has successfully simulated a bubble imploding under sinusoidal pressure wave (produced by ultrasounds): you can check his new website:
http://www2.arnes.si/~mdula/index.html

adambarfi May 22, 2012 02:01

Quote:

Originally Posted by ghost82 (Post 362141)
Hi adambarfi,
In the past I tried the simulation of a single water-vapor bubble imploding in water under constant pressure (2D simulation, axisymmetric).
It's not that easy...I tried to simulate the implosion with VOF model, by paching the liquid domain with a semicircle of vapor (d=100 micron), but my resuts were not good..
Attention has to be paid to the grid, it has to be very refined at the liquid-solid interface, as the gradients are very large.
I read that Matevz has successfully simulated a bubble imploding under sinusoidal pressure wave (produced by ultrasounds): you can check his new website:
http://www2.arnes.si/~mdula/index.html

Thank you ghost

ndabir July 12, 2012 18:39

Hi Mostafa,

have you solved your problem? I am doing the same kind of simulation. here are some comments on your simulation:

1)you can start with very fine mesh near the bubble (like 200000) and less mesh at far regions.

2)use patching to set pressure and temperature to inside the bubble.

3) use double precision method

4) use these solution methods: simple, gauss cell based, presto, first order, geo reconstruct

5) reduce the URF to low amounts like 0.5. for pressure to 0.2 or even lower

6) use VOF with default settings

7)do not use time steps smaller than 1e-10

hope I these helps. I have simulated the bubble growth successfully butwhen it comes to bubble collapse, my simulation diverges. If you have solved your problem, do you have any idea what should I do to get rid of divergence?

adambarfi July 17, 2012 04:50

thank you ndabir,
I will try it and tell you the results.


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