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[ICEM] Negative Volumes & 7 node HEXA elements

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Old   September 16, 2010, 09:34
Default Negative Volumes & 7 node HEXA elements
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Tim Hannah
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Hey guys,

I thought I had finally figured out my turbine blade blocking, my pre-mesh looked good.

I went ahead and tried to export my mesh to Fluent V6 and got this error: "Error : Fluent format does not support 7 node HEXA elements."

My understanding is that this is caused by degenerate elements or elements with negative volume?

I did a pre-mesh quality check on Volume and it said I had some 800,000 elements with negative volume, I clicked on the histogram to check which elements where causing the difficulties and for some reason it displays all of these elements which are outside of my geometry??

I attached some pictures to hopefully give a clearer understanding of my problem.

I would really appreciate any help, this is a thesis project with not long to the deadline.

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File Type: jpg negative volumes.jpg (89.0 KB, 57 views)
File Type: jpg blocking.jpg (43.4 KB, 44 views)
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Old   September 21, 2010, 12:45
Default Vorfn and 2 Pyramids.
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Simon Pereira
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Perhaps you had the VORFN material active when you created/output your mesh? Make sure it is not active (turn off the part in the model tree) and try again. ICEM CFD maintains these outer blocks in order to maintain index connectivity, etc. But you don't want them active during the conversion from premesh or output to solver. If you do, ICEM CFD will think they are another volume material and will output them.

For those of you with 7 noded elements inside your volume of interest, we added an option at 12.1 (under settings => Hexa Mixed) that will automatically convert these into two pyramids so that your solver won't mind it.
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