Learning Forum

[Alina Larin]

I am trying to mesh an artery in Ansys Meshing and get this weirdly shaped elements. I have tried about everything, but nothing helps. Any ideas how to fix it?

[NickFL]

Have a look at your geometry there. One possible solution if you don't want to go back to DesignModeler / SpaceClaim is to use Virtual Topology to merge faces. My expectation is there are a couple of short edges or hard points there that you will want to remove.

[Alina Larin]

Thank you for your fast reply. Actually there is no edges there. I just don't get it, why is this happening..

[NickFL]

There must be a folded face or hard points or something there. Otherwise, the Mesher would have nothing to seed. Another approach would be to use the Patch Independent tet mesh method. Are you familiar? Basically this will mesh the volume and then projects it to the surfaces. If you adjust the settings a bit, you should be able to have this ignore this thin line/point/whatever it is. To use it, add a Method with Type-> Tetrahedrons and then change the Algorithm from Patch Conforming to Patch Independent.

[Alina Larin]

Thnk you very much. Yes I tried to use patch independent meshing, but every time I am trying the computer get stucked. I have returned to spaceclaim and splitted this face multiple times. And it helped!

[Rob]

Have a look for hard edges and/or a kink in the surface. The mesh thinks there is something there that needs resolving. 

[Alina Larin]

Thank you you Rob. The face has indeed number of kinks. So I have splitted the face in Spaceclaim and it helped!

[Rob]

OK. If you're using Fluent also see if the geometry does the same in Fluent Meshing. Where did the geometry come from? It looks vaguely organic. 

[Alina Larin]

It is CT scan of some vein. Originally the geometry was in STL format and I performed reverse engineering in SpaceCaim using Auto Skin.

[NickFL]

Yes STL sometimes will have floating triangles with incorrect outward pointing normals. They often require a lot of time to get cleaned up, although the aforementioned SpaceClaim makes it much better than it used to be.

[Rob]

It's sometimes better to talk to whoever did the segmentation of the MRI scan if you can. The two packages/developers that I'm aware of have surface remeshing options that may make life a little easier. 

https://www.ansys.com/partner-ecosystem/technology-partners/materialise

https://www.ansys.com/partner-ecosystem/technology-partners/synopsys

[Alina Larin]

Thank you very much for your help!