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May 6, 2009, 07:55 |
Cell skew Factor
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#1 |
Senior Member
Prapanch Nair
Join Date: Mar 2009
Location: Bangalore, India
Posts: 105
Rep Power: 17 |
Hi,
I would like to know what the term delta( cell skew factor ) means in the decomposeParDict file. It has a default value of 0.001. I understand cell skew factor as the product of the ratio of the opposite side lengths of a cell, and hence will be 1 for a parallelogram. But how would this affect the decomposition? Does Foam chose cells with the delta value as the processor boundaries? I have been getting a lot of instabilities while running in parallel, code crashes after 6000 iterations etc. But the code runs fine in series. Does this delta affect the stability in any way? Thank you Prapanj |
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June 14, 2010, 05:52 |
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#2 |
New Member
Duncan Roy van der Heul
Join Date: May 2010
Posts: 26
Rep Power: 16 |
I have exactly the same question.
Anyone? Regards, Duncan |
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May 23, 2011, 08:01 |
any news about delta (cell skew factor) ?
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#3 |
Member
José
Join Date: Jan 2011
Posts: 73
Rep Power: 15 |
Hi!,
did you get any news about delta (cell skew factor)? I am quite sure that this value affects the stability of the solution. Thanks, Greetings. José |
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May 23, 2012, 11:12 |
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#4 |
Member
Fabian E.
Join Date: Nov 2009
Posts: 38
Rep Power: 17 |
*push* Does anyone know an explanation?
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June 18, 2013, 09:30 |
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#5 |
Senior Member
Francois Beaubert
Join Date: Mar 2009
Location: Lille, France
Posts: 147
Rep Power: 17 |
up
Thanks |
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August 21, 2013, 11:53 |
cell skew value
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#6 |
Member
Jamal
Join Date: May 2012
Location: Freiburg
Posts: 54
Rep Power: 13 |
hello,
Now I am preparing a case to run in parallel. How the subdomain boundaries are defined in 'simple method' by individual solvers......does this delta (cell skew factor) has any influence on this decomposition. regards, Jamal |
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August 22, 2013, 08:05 |
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#7 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,981
Blog Entries: 45
Rep Power: 128 |
Greetings to all!
A test case would be nice, to make it easier to demonstrate the influence of this parameter "delta". At least in theory (and taking into account that I'm not an expert on this topic), the objective of this parameter is to avoid using the faces of highly skewed cells being used as the processor boundaries, since any solver treatment that could be done on those related cells, would be very difficult to do anything proper, since it would require cells from two or more processor sub-domains. Or if it is able to do anything proper, it'll take longer to run, since it will need several times more feedback from the other processors. Either way, if you have concerns about these kinds of cells, feel free to increase the value of "delta" to "0.01", to avoid those skewed cells/faces. In addition, use checkMesh to ascertain the worse scenario of skewed cells/faces your mesh has got. Best regards, Bruno
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August 25, 2013, 16:44 |
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#8 |
Senior Member
Mohsen KiaMansouri
Join Date: Jan 2010
Location: CFD Lab
Posts: 118
Rep Power: 16 |
Thanks Bruno for the useful explanations.
I just want to add that in my experience, using checkMesh for controlling the mesh quality is not always sufficient. Code:
checkMesh -allGeometry Foamers can check Code:
checkMesh -help
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“If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.” |
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Tags |
cell skew factor, decompose, delta, parallel |
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