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-   -   [ICEM] Hex-Core disconected (http://www.cfd-online.com/Forums/ansys-meshing/95396-hex-core-disconected.html)

max3.2 December 15, 2011 12:18

Hex-Core disconected
 
Hey Guys,

I'm trying to mesh a duct flow with tets, prisms and hexa core. Everytime I try to do so, the hexa-core seems to be disconnected from the outside prisms. Theres's just a free space in the cut plane and the hexa elements are way to big. Mesh checks confirms unconnected faces.
I can't find any way around it, anyone knows what could possibly be wrong?

Cheers
Max

max3.2 December 15, 2011 12:45

little update: if i do the hex first, prism wont work but hex does. other way around its prisms but no hex

PSYMN December 19, 2011 11:37

Recommend Change Mesh Type => 12 Tetra to 1 Hexa instead.
 
Hex core works by deleting the prisms, meshing the region with a cartesian fill, then deleting the hexas that intersect the surrounding elements and then filling the gap with a delaunay tetra fill (gives you pyramids where needed).

The size of the Cartesian mesh is set by the size on the volume part (this is one of the few times that size on a volume part is used). If your hexas are too large, you could reduce this size.

The delaunay fill can fail for several reasons including too much of a size jump between the hexas and the surrounding elements or due to hanging nodes on the external surface of the hexa core block.

Personally, I avoid use of hexa core. I do not find it to be robust.

Instead, I suggest you use Octree Tetra. Then run an editing step to change mesh type and convert 12 tetras to 1 hexa. This will give you what you are really looking for.

Note: Prism is insterted post tetra and can only move tetras out of the way. It must be run before either Hexa Core or Tet to Hex conversion...

max3.2 December 25, 2011 14:42

Hey,
Thank you that works fine now. Is the he a size only determined by the gets or is there a way to change them once they are created?

PSYMN January 3, 2012 16:01

When you are converting tet to hex, the size of the hexas is determined by the size of the tetras...


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