[kandelabr]

Hello.

This doesn't really belong to OpenFOAM and snappyHexMesh but this is the most relevant forum I can think of.

I'm preparing STL files for multiregion snappy with salome. I Import STEP assembly, explode it to solids and do a Partition. Then I create volume groups for each of the solids and face groups from volume groups (the standard procedure, I guess? Or is there a simpler method?).

My problem is that some of the faces are misteriously missing from the face groups. See the attached images.

Has anyone had similar issues? Where do I even begin with the troubleshooting?

Thanks!

[time-]

Hi,
try to explode the partition into solids and create face groups from those.
In SMESH you will make a group on geometry also for volumes, selecting the exploded solids.

By the way, what do you use as base for partition? As the very model is already exploded I guess you build a primitive to use partition on to obtain fluid volume. Is it correct?

In the second pic you highlighted only 3 "missing" surfaces, but I guess all the caps are missing, correct? In this case another thing you could try is to repair the model (try glue edges / glue faces) just to be sure the geometry is a single piece.

One last thing: what shape type did you select in the partition menu? Be sure to select solid and not compsolid.

Anyways, without knowing exactly all the steps you did I can't say more.

Bye

[kandelabr]

Originally Posted by time-

Hi,
try to explode the partition into solids and create face groups from those.
In SMESH you will make a group on geometry also for volumes, selecting the exploded solids.

Yes! That did the trick, thank you! I use salome only to prepare STL files for snappy so I only create a 2D mesh to export to STL. Volume groups don't work on 2D meshes.

Originally Posted by time-

By the way, what do you use as base for partition? As the very model is already exploded I guess you build a primitive to use partition on to obtain fluid volume. Is it correct?

I use a list of solids which I extracted from a STEP file. I could add fluid regions or not but STEP does not divide the surfaces where different parts are in contact. That's why I need a partition in the first place.

Originally Posted by time-

In the second pic you highlighted only 3 "missing" surfaces, but I guess all the caps are missing, correct? In this case another thing you could try is to repair the model (try glue edges / glue faces) just to be sure the geometry is a single piece.

Yes, all the surfaces are missing and this is not the only part with such issues. Repairing the model did not work because i guess it wasn't broken in the first place.

Originally Posted by time-

One last thing: what shape type did you select in the partition menu? Be sure to select solid and not compsolid.

Anyways, without knowing exactly all the steps you did I can't say more.

Yes, solid is what I selected.
You need say no more, you got it right in the first try

Thank you very much!

[time-]

Originally Posted by kandelabr

I use a list of solids which I extracted from a STEP file. I could add fluid regions or not but STEP does not divide the surfaces where different parts are in contact. That's why I need a partition in the first place.

STEP format is indeed suitable for non-manifold models.

I don't know which CAD software you are using, I work mostly with Rhino6 so I can speak only for my specific case but usually I do split my model using feature edges and then rejoin (not fusing, just joining) everything together.

When I import the resulting step file into Salome I get a single solid (or shell) but I can explode it into single parts.

Splitting is like partitioning in Rhino and joining is kinda compound feature.

Keep in mind I always work with surfaces and not solids, but I always get a watertight solid when I import the step into Salome.

I dropped Inventor due to license costs so I don't know if inventor/solidworks work the same way rhino does.

Bye

[kandelabr]

I use Creo and i'm almost certain there's no such option. I could split surfaces by hand but here's a complex assembly of 60+ objects which I have no intention to tamper with by hand.

I'm writing a script to automate the salome process so I need simple and reliable steps. So far it looks like it can be done

[kandelabr]

FYI, in the end I couldn't get it to work with face groups so I chose a different approach:

1. import STEP assembly
2. explode it to solids
3. create a partition from solids
4. assign volume groups
5. mesh the partition
6. create submeshes on volume groups
7. export submeshes
8. I avoided creating face groups and it seems to work OK for the
9. geometries that were causing trouble.

Thank you for your help.

[Tryphena]

Originally Posted by kandelabr

FYI, in the end I couldn't get it to work with face groups so I chose a different approach:

1. import STEP assembly
2. explode it to solids
3. create a partition from solids
4. assign volume groups
5. mesh the partition
6. create submeshes on volume groups
7. export submeshes
8. I avoided creating face groups and it seems to work OK for the
9. geometries that were causing trouble.

Thank you for your help.

Hi Kandelabr,
I have similar problem to yours. But I am dealing with STL file. I could not explode it to solids. Do you have any idea about how to deal with STL assembly? Thank you.



Regards,
Tongfen

[kandelabr]

in my experience salome is terrible with STLs but my experience is very limited. maybe you could try with blender, at least that's where i would start...

[Tryphena]

Hi Kandelabr,
Actually I build my objects in Blender, and export to STL file to Salome. Salome could not recognize different objects.



Can you take a look at my post:
How to create Volume group from STL file of assembly


Thanks.

Regards,
Tryphena