Very strange problem with sphere meshing

Discussion about meshing issues.

Very strange problem with sphere meshing

Postby hngnet » Wed Dec 20, 2017 8:54 am

Dear all,

I have Trelis 16.3, 16.0 and Cubit 13.2. When I try to mesh a sphere with a simple journal commands:

create sphere radius 4
volume 1 size 0.8
volume 1 scheme Sphere
mesh volume 1

Trelis give very strange mesh. As I posted previously, nonplanar faces are also visible everywhere! But with the Cubit 13.2, I get correct mesh. Please see attached figures. What is so stange to me is that even if I change the mesh size, mesh in the trelis remains unchanged! Can anyone or anyone from the support team help on this please?

Best,
HNG
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hngnet
 
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Re: Very strange problem with sphere meshing

Postby csimsoft Moderator » Wed Dec 20, 2017 12:20 pm

It looks like the default sphere scheme values changed sometime after Cubit 13.2, because this same behavior is also in Cubit 15.4 and Trelis 16.4. The defaults are now:

Volume 1 meshing scheme set to Sphere
graded_interval = 2 (Default)
az_interval = 8 (Default)
bias = 0.397887 (Default)
fraction = 0.500000 (Default)
max_smooth_iterations = 0 (Default)


You should change these values to the values below to get the similar sphere mesh you got in 13.2.

Volume 1 meshing scheme set to Sphere
graded_interval = 6 (Default)
az_interval = 32 (Default)
bias = 0.75 (Default)
fraction = 0.250000 (Default)
max_smooth_iterations = 0 (Default)

The new journal commands would be:

reset
create sphere radius 4
volume 1 size 0.8
volume 1 scheme Sphere graded_interval 6 az_interval 32 bias 0.75 fraction .25
mesh volume 1

More information about the parameters can be found here:

http://csimsoft.com/help/trelishelp.htm ... sphere.htm
csimsoft
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Re: Very strange problem with sphere meshing

Postby hngnet » Wed Dec 20, 2017 2:29 pm

Thank you so very much! I now got the finer mesh, but some elements have nonplanar faces. Please see attached figure. I plotted those coordinates in matlab, they are indeed NOT planar. This causes a serious problem when computing Jacobian in FEM/SEM. Do you have any suggestion?

Best,
HNG
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hngnet
 
Posts: 11
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