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ladybug-tools / butterfly

:butterfly: A light python API for creating and running OpenFoam cases for CFD simulation.
http://ladybug-tools.github.io/butterfly.html
GNU General Public License v3.0
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CheckMesh Maximum Skewness #237

Open MikkiSeidenschnur opened 7 years ago

MikkiSeidenschnur commented 7 years ago

Hi Guys

I know this is probably more appropriate on the CFDOnline Forum, but I think that @TheodoreGalanos or @thinklikeanarchitect might be able to answer this one.

I'm wondering how the MaxInternalSkewness for checkMesh can be higher than one. For instance in https://cfd.direct/openfoam/user-guide/snappyHexMesh/#x26-1930005.4.8 they say that the maximum allowed Skewness is 4 (I know that for commercial software like Fluent 1 is the maximum)

What I'm asking is: How does checkMesh for SHM actually calculate the internalCellSkewness? Because I cannot for the life of me find out why it is possible to have something higher than 1 :).

I hope you can help me out here, let me know if I'm not formulating the question to an understandable level.

Best regards Mikki Seidenschnur

TheodoreGalanos commented 7 years ago

Hi @MikkiSeidenschnur If I understand correctly what you are referring to take a look at page 51.

https://openfoamwiki.net/images/f/f0/Final-AndrewJacksonSlidesOFW7.pdf

MikkiSeidenschnur commented 7 years ago

@TheodoreGalanos Yes, so that is actually the part where I'm in doubt - So that's what I'm getting at: How can the skewness actually be higher than 1, because for me that would mean that the magnitude(di)>magnitude(ci)? Is that even possible?

hrobeers commented 5 years ago

The skewness value reported by checkMesh is calculated differently than is done by most others (paraview, fluent, ...).

For the same structured 2D mesh I got the following max skewness: