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Old   January 18, 2005, 06:05
Default Dynamic Meshing Problems
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Shuto
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Hi, I am moving a small body rapidly across a large domain and using dynamic meshing to accomplish this. I have the following problems: 1. Using a low spring constant for smoothing improves cells close to the body but cells farther out become compressed and highly skewed. A high spring constant creates many enlarged and poor quality cells close to the body. 2. The regions adjacent to the body always develop many highly skewed cells, reducing max skewness means that many miniscule cells appear. Neither is satisfactory. 3. Regardless of any parameter I change, remeshing always introduces large, often double-sized cells at random locations. Sometimes these heal, sometimes they don't. Can anyone offer any advice on improving Fluent's remeshing behaviour? I have been through all the notes and every tutorial available and still cannot solve these issues.

Regards, Shuto.
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Old   January 19, 2005, 17:58
Default Re: Dynamic Meshing Problems
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CFDtoy
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hello Shuto,

Try to reduce the minimum and maximum volume consideration in the dynamic meshing procedure.

in the volume statistics grid check procedure) if you get

minimum cell volume = a e-15 maximum cell volume = b e-011

what do u use in the remeshing procedure? Perhaps looking at that I might help you.

CFDtoy
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Old   January 19, 2005, 21:07
Default Re: Dynamic Meshing Problems
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Shuto
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Hi CFDtoy,

I am able to control the behaviour by using very low max and min but this vastly slows down the remeshing as all the larger cells farther out are marked for remeshing every time. It is so slow it can take a few minutes just to remesh once.

From the lecture notes and tutorials it should be possible to control the cell size adequately using size function parameters but I just can't seem to get it to work.

In the case you asked about I would use 0.99a e-15 and 1.01b e-11 and try to make the size function control the size this way. I tend to use a low max skew (0.3 to 0.4) as this seems to prevent large cells forming.

Thanks,

J.
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Old   January 19, 2005, 21:09
Default Re: Dynamic Meshing Problems
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CFDtoy
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your skewness is very low..allow till 0.6..although large cells may be formed with skewed. I always use the remesh options. Kinda works...

CFDtoy
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