Failure in Matching Tetrahedral Meshes

Coreform Cubit
#1

Coreform Cubit Version: 2022.11
Platform: Windows 10

Failure in Matching Tetrahedral Meshes
box2.e (98.1 KB)
box1.e (507.9 KB)

I want to match meshes from box1.e and box2.e at their command slide.
What am I doing wrong?

Cubit>import mesh "D:/Developments/FE_Runs/Sculpt/test/box1.e" no_geom unique_genesis_ids

Reading element block 1 with 16824 elements of type TETRA...

Successfully read 16824 elements for block 1.

The imported mesh entities are not owned by any geometry,

and have been placed in free_elements (Group 2).

To draw or list these elements, specify their ids or containing group.

To delete these elements, try 'delete mesh preview'.

Group size is too large to print all entity ids. Printing summary instead:

Group Entity 'free_elements' (Id = 2)

It owns/encloses 21511 entities: 3532 nodes, 705 edges, 450 tris, 16824 tets.

Finished Command: import mesh "D:/Developments/FE_Runs/Sculpt/test/box1.e" no_geom unique_genesis_ids

Cubit>import mesh "D:/Developments/FE_Runs/Sculpt/test/box2.e" no_geom unique_genesis_ids

Reading element block 1 with 3046 elements of type TETRA...

Successfully read 3046 elements for block 1.

The imported mesh entities are not owned by any geometry,

and have been placed in free_elements@A (Group 3).

To draw or list these elements, specify their ids or containing group.

To delete these elements, try 'delete mesh preview'.

Group size is too large to print all entity ids. Printing summary instead:

Group Entity 'free_elements@A' (Id = 3)

It owns/encloses 4105 entities: 723 nodes, 208 edges, 128 tris, 3046 tets.

Block collisions detected when importing Exodus file

ID in File Assigned ID Name in File Assigned Name

1 2

Finished Command: import mesh "D:/Developments/FE_Runs/Sculpt/test/box2.e" no_geom unique_genesis_ids

Cubit>draw sideset 2

Cubit>draw sideset 1 add

Cubit>Meshmatch tet sideset 1 onto sideset 2

ERROR: No acceptable triangles possible on surface!

WARNING: TetMeshMatchingTool::create_tri_mesh: Mesh regeneration failure...

ERROR: Tet Mesh Matching not successful...

Cubit>
#2

Hello,
when i look up in the manual it reads

The source sideset should be completely enclosed in the target sideset so that the boundaries of the two sidesets do not intersect.

I think the problem is that the boundaries of the two sidesets are matching.

when i try this, the matching works

reset
brick x 1 y 1 z 1
brick x 2 y 2 z 2
move Volume 2 x 1 include_merged 
move Volume 1 x -0.5 include_merged 
volume all scheme tet
volume 1 size 0.1
volume 2 size 0.2
sideset 1 add surface 6  
sideset 2 add surface 10  
mesh vol all
block 1 add volume 1
block 2 add volume 2
disassociate mesh from volume 1
delete volume 1
disassociate mesh from volume 2
delete volume 2
Meshmatch tet sideset 1 onto sideset 2

if i would do that for cubes of the same size, i get the same errors like you

1 Like
#3

Thank you @Norbert_Hofbauer. @karl also confirm what you found. Is there a minimum distance between these two boundaries must be at such that they are not considered intersected?

#4

As near as I can determine, the constraint is that the area of the triangle must be greater than 0. There is a machine epsilon tolerance to the numerical definition of 0. Also, the near zero area triangle will be the face of tetrahedron in your mesh. The Jacobian of that element will approach zero and your solver will either fail or give bad results in that area.

Karl