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moh January 7, 2004 02:58

emptyin the bottle
hello, when I empty the bottle from its fluid it shrink to inside how can I simulate this phenomena in star-cd? Thanx a lot.

F.K. January 7, 2004 03:13

Re: emptyin the bottle
You have to use STAR-CD and MPCCI in combination with a FEM tool.


Lars Ola Liavåg January 8, 2004 02:30

Re: emptyin the bottle
If you just calculate the hydrostatic pressure distribution in the filled bottle and apply that as a BC in a FEM calculation, you ought to get a good answer for the deformation caused by the liquid pressure. Why would you want to use CFD for this case at all?


Lars Ola

moh January 8, 2004 03:10

Re: emptyin the bottle
Thanx for answering me.

the problem when fluid fall down from the bottle a mount of air inter inside and make the value of presuure more than vacum and i dont know how to calculate this pressure if i can i will use it as BC and for me its better than make combination withh MPCCI cause i dont know this software

Lars Ola Liavåg January 9, 2004 02:43

Re: emptyin the bottle
If you have an opened bottle filled with liquid and standing on a table, the pressure acting on the inside wall will at any distance h below the liquid surface equal p_ambient + rho*g*h where rho is the liquid density and g is the acceleration of gravity.

Equally, if you turn the bottle upside down, the mean (ensemble average) pressure in the air above the surface should equal p_ambient - rho*g*H where H is the height of the liquid. Within the liquid, the pressure increases linearly to p_ambient towards the bottle opening.

Of course, if you empty the bottle, H will vary with time, and you will also see pressure fluctuations because of the bubbling of air into the bottle. If this is important to you, then CFD might be the answer, but even now only to get the pressure on the surface as BC's for the FEM calculation (I can't imagine a bottle in practice deforming so much that it is of importance to the pressure field). If you just need estimates, the hydrostatic pressure calculation should do fine.

Best regards,

Lars Ola

ze January 13, 2004 22:07

Re: emptyin the bottle

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