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COnvergence Problem !!!!

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Old   May 27, 2003, 12:30
Default COnvergence Problem !!!!
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I'm using VOF (water + air) model Geo-reconstruct, PISO, PRESTO, with good mesh (skewness <0.82)

The problem is : all equations converge very well whereas COntinuity still oscillating about 0.003!!! does any one know why? or how to resolve?

Thanks in advance

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Old   May 27, 2003, 14:37
Default Re: COnvergence Problem !!!!
Shiping Liu
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did you try smaller under-relaxation factors?
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Old   May 28, 2003, 02:56
Default Re: COnvergence Problem !!!!
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Hi Liu and all,

For which parameters should I reduce this under relaxation factors.

I worry that computation will become very much slow with a small time step (0.0001) and smaller under relaxation factors !!!

Is there any rules in modifying these under relaxation factors. I know only that for momentum and pressure , the sum should be 1 (0.3 + .07 for example)

Thanks In advance, Mohamed
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Old   May 28, 2003, 03:35
Default Re: COnvergence Problem !!!!
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I think the best for you is to chech the messages on forum - there has been A LOT of discusions about convergence with VOF model.

And don't play to much with undre relaxation...if you decerase them to much, your solution will converge but it will take a very long time and the solution might be wrong. I think 0.3 is the minimmunm.


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