T-Junction Solid without Free Edges

Altair Forum User

Hi!

I'm a HM beginner and I have a problem with my model. My aim is to build and to mesh a simple cuboid. Its top surf should consists of 3 quad-elements (with T-junction). The other 5 surfaces should just be single quad-elements in the initial configuration. The meshing of the cuboid shoud be done withTetras (the top surface with the T-junction have remain the same over volume mesh).

First, I created the 4 corner points of the cuboid. Then I created the 6 surfaces via (2D->plane) and meshed them with one element per  surface. To archieve the T-junction in the surface on the top of the cuboid i splitted the surface and merged 2 of the 4 elements.

Unfortunately after getting the equivalence nodes, there are still free edges on this surface (c.f picture). I tried to avoid this by creating additional nodes. But i still have the same problem.

 

It would be great, if somebody can help me. Is there another (maybe better) possibility to create and mesh such a cuboid?

 

Thanks for your help, and sorry for my newbie-questions!

 

 

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Altair Forum User

Hi,

 

First rule for generating a tetra mesh: no T-connections or edges, meaning, the 2d-mesh should form a closed volume with no t-junctions.

 

for your particular problem, if the 'surface mesh' option doesn't work, use the 'ruled' option in the 2-d panel.

 

Then if required you can project the nodes on to the surface (with ruled option the generated mesh is not associated with the underlying geometry), but in your case this may not be required since all

 

the cube surfaces are perfectly plane and perpendicular to each other. Once you are done with all the surfaces, use the 'tetramesh' option in the 3-d panel.

 

Hope this helps.

Altair Forum User

Hi,

 

First, thanks for your help. I'm not sure if I understood you correctly. Is it possible to get a tetra mesh from a surface with T-junction with use of the 'ruled' option??? I created the same cuboid with this option instead of 'planes' and got the same result as before: There are free edges in the top surface (see picture above). So I'm not able to perform the tetra mesh (volume is not enclosed).
Did i forget any step? Is there another possibility to get a volumetric mesh with a T-Junction in one of the 2D-meshs (The other 2D mehs and the volume mesh could be arbitrary 'ugly'). I need this as one of the first steps for a proejct at university. Unfortunately there is no HM-expert in the institut.

 

It would be great, if you, or someone else, could help me again.