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Re: CGNS mesh export doesn't work properly for hybrid meshes

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Re: CGNS mesh export doesn't work properly for hybrid meshes

Posted by Thomas Aumeier at September 08. 2016

Hi everybody,

For my calculations I create hybrid meshes with Salome-7.6.0 which consistsof hexahedral and tetrahedral elements as well as pyramids and prisms within the transition zones. But exporting a mesh with about 9 million volume elements into CGNS format takes more then 24 h !  As well as the file size of the exported mesh is quite high (more than 1GB) .

If I run "cgnscheck filename.cgns" (or adfviewer)  I am able to check the CGNS data file structure. Doing this I must recognize that for each pyramid element and its four neighbouring tetraheadral cells an own element set has been created, i.e. lets say 1000 hexahedral elemets are stored in one element set while 1000 pyramids are stored in 1000 element sets plus 1000 element sets for the four neighbouring tetras.

This behaviour can't be observed when using another meshing tool. Than all pyramids or prisms refer to only one element set in the CGNS data structure. I guess there must be something wrong in writing CGNS files when pyramids or/and prisms are involved.

Best regards

Thomas A.

 

The output of "cgnscheck" for a CGNS file consisting of tetras and pyramids is attached!

 

 

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Re: CGNS mesh export doesn't work properly for hybrid meshes

Posted by SMESH expert at September 09. 2016

Hello Thomas

According the log of cgnscheck the CGNS file is correct. The elements are exported in the order they were generated, that is why there are many element sets.

A low performance of CGNS export can be a subject of improvement.

Best regards

Edward

Re: CGNS mesh export doesn't work properly for hybrid meshes

Posted by Thomas Aumeier at September 12. 2016

Hello Edward,

what do you mean with "low performance of CGNS export"? I have no options to make some improvements for exporting CGNS data. If I use MED format I have no problems. The file size is small and it takes less then 2 minutes to export the mesh. But still, I need CGNS for the preprocessor!

Best regards

Thomas

 

Re: CGNS mesh export doesn't work properly for hybrid meshes

Posted by SMESH expert at September 14. 2016

Hello Thomas

"low performance of CGNS export" == 24h to export 9e6 elements. I will check if it is possible to improve this low speed.

Best regards

Edward

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