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Old   November 4, 2005, 21:46
Default VOF for hours
John Collins
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Hi All,

I'm running VOF using CFD-ACE+. The transient simulation takes long time to cross a few seconds of problem. But my problem has to run for 24 - 48 hours and so the computational time will be in weeks.

Does anyone know how to speeden up VOF simulation. In CFD-ACE+ there are a few parameters such as Target CFL and dt. I want to know whether they can be cleverly adjusted.

Thanks in advance.

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Old   November 5, 2005, 11:01
Default Re: VOF for hours
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Hi, John,

Does surface tension effect dominante your flow problem? How about density ratio? Minimum length of the cells is another issue.

For most of my free surface problems, that is, moderate surface tension + ~0.01 mm length + density ration of 1000 (air/water), the delta is usually in the 10e-5 range.

In general, you want CFL to be less than 0.5. Try to increase CFL to see if you solution is still reasonable.

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Old   November 6, 2005, 14:59
Default Re: VOF for hours
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I do not think this problem can solved very well. 24-48 hours is not a very long time. The more your experience, the less time you use.
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Old   November 8, 2005, 16:11
Default Re: VOF for hours
John Collins
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The surface tension is acting on a 4mm radius capillary and density ratio of 1000 (air/water).

The geometry is a U tube with both the arms are connected by a narrow (0.003mm radius)capillary. The height of 3mm water column is slowly levelling up due to its weight.

The time taken for both the levels of the U tube to become equal is around 24-48 hours.

Since there is not much change in the successive steps of the VOF simulation,I want to accelerate it.

Thanks John
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