# [ICEM] Prism Mesh on a semisphere

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June 2, 2013, 13:27
Prism Mesh on a semisphere
#1
Member

W.N. Anderson
Join Date: Jul 2010
Location: Zürich, Switzerland
Posts: 46
Rep Power: 8
Why does ICEM produce an erroneous Prismmesh on this simple semisphere?

Replay script and graphical result attached.
Attached Images
 brokenPrism.jpg (92.9 KB, 39 views)
Attached Files
 test.rpl.txt (15.8 KB, 7 views)

 June 2, 2013, 18:12 #2 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,366 Blog Entries: 23 Rep Power: 21 the problem resides in the geometry. make sure all the surfaces are checked for prism... You can share your project so we can investigate with you... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/NEbygB Ali

 June 2, 2013, 18:15 #3 Member   W.N. Anderson Join Date: Jul 2010 Location: Zürich, Switzerland Posts: 46 Rep Power: 8 Thank you diamondx. In fact, i have found a different but related problem. The symmetry surface and the ball must share an intersection curve. They hadn't before. Once the intersection curve between the symmetry plane and the ball was implemented (Geometry->Curve->Intersection of Surfaces), the mesh looks quite normal.

June 2, 2013, 21:11
#4
Retired from CFD Online

Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,660
Blog Entries: 1
Rep Power: 38
Yes, but the fix is simpler than that...

The bad intersection caused the problem...
Will_Anderson_Prism_1.jpg
This is because your small circle was offset a bit, which crumbled the edges so prisms couldn't form.

Here you can see that the prisms are fine away from the bad edge...
Will_Anderson_Prism_2.jpg
See here in the script... Why did you set the center of the sphere 1 unit below the symmetry plane?
Will_Anderson_Prism_3.jpg
Once I fixed that first line (to go from 0 to 1 instead of -1 to 0), it worked no problem...
Will_Anderson_Prism_4.jpg
Attached Files
 test.rpl.txt (15.8 KB, 5 views)
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 June 2, 2013, 23:30 #5 Member   W.N. Anderson Join Date: Jul 2010 Location: Zürich, Switzerland Posts: 46 Rep Power: 8 Thanks Simon. Why did I offset the sphere center by 1 mm? In order to be more sure that the surfaces intersected. Thanks everyone.

June 3, 2013, 10:31
#6
Retired from CFD Online

Simon Pereira
Join Date: Mar 2009
Location: Ann Arbor, MI
Posts: 2,660
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Rep Power: 38
Quote:
 Originally Posted by Will Anderson Thanks Simon. Why did I offset the sphere center by 1 mm? In order to be more sure that the surfaces intersected. Thanks everyone.
OK, but it was probably unnecessary. ICEM CFD can handle some misalignment, but in this case, it was just too great compared to the mesh size.
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