[Persil]

Hello everyone,

I generated 2 .dbs-files with 180.000 and 160.000 elements. I export them as .msh for later use with fluent. But first when importing both back into Gambit to rearange them a bit, they both increase in element numbers to 179.000 and 202.000

why does that happen? Is that just the difference between .dbs and .msh? My first guess was, that it should keep the number of elements it has as .dbs

[-mAx-]

why don't you re-open the dbs file, and re-export another msh file.
I am also septic with msh import from Gambit

[Persil]

I don't see the difference between your mentioned re-opening and the things I did...

there are 2 dbs-files, I export a mesh each

then open a new file and import both meshes separetely, create groups, rearange them and then export 1 mesh-file... works fine, except the differences in the amount of elements, which I have no explanation for

[-mAx-]

why are you using 2 dbs files?
At the end you get 2 msh files which won't be connected.
If you are working with sliding mesh, I can understand the use of both dbs file.
...
Are your both mesh files connected?
...
what kind of group operations are you using, and for what?
...
As I said mesh import in Gambit isn't comfortable, and I am not surprised of your issue. I had also some issues on surfaces which are merged, etc...

[Persil]

I use 2 dbs files because 1 is a blade and 1 a vane, which I will need later on... right now I want to combine them to 1 stage to get 1 mesh-file for the whole stage, do you see a better way to generate this mesh?

after importing the 2 mesh-files, each becomes a group and then I align them, via translating and rotating... no connected geometry enabled

later in fluent I will create mixing planes between the vane and blade...

[-mAx-]

build all your geometry and mesh all within one dbs file
If you still have real geometries (no virtual entities), you may export the geometry with step file (the splits etc SHOULD remain).
Then you can use the .jou of the dbs to remesh the geometry (in the new dbs)
But if you have a nice hexa mesh with lots of splits, I am not sure you want to remesh all your stuff (if the journal file failed)

Else you can keep your method: just note the translations and rotations vector, then open one dbs and adjust the position of the mesh (with vectors you noticed). In that way you can import both mesh in fluent, and they shlould be aligned.

[Persil]

Using just 1 dbs-file does not seem possible for me in this case, because those 2 files are just the beginning... in the end it will be 10 dbs-files with a mesh each

I may try to align the meshes in fluent... although I don't know if I can apply the translation/rotation that easily, because in Gambit I did it from vertex to vertex

but back to my original question: is that increase in elements when importing mesh in gambit just an unexplainable error? or do you know what Gambit is doing at that point?

[-mAx-]

Originally Posted by Persil

but back to my original question: is that increase in elements when importing mesh in gambit just an unexplainable error? or do you know what Gambit is doing at that point?

No I don't know what Gambit is doing really while importing mesh file.
Check if it doesn't create other kind of element (tetra-pyramid, etc...)
Check also number of surfaces
Don't you see any difference on your mesh?
Check also number of cells once imported in Fluent (check Mesh)

[Persil]

there are no changes concerning topology or even element type, all elements behave and stay hexahedral

the funny thing is, that even though when importing the mesh Gambit displays that there are 202.000 elements... but when checking the grid, the original element amount is shown (see attachment)... where do those non-existing 20.000 elements come from and are they even there?

[-mAx-]

Gambit reads 202.000 elements while importing, but it doesn't mean it writes those 202.000 elements. You can see also it creates some nodes, edges and faces, which mean it modifies the grid (the question is why)
Try to import this mesh in Fluent and run a check mesh (and compare the numbers you get)

[ghost82]

If you have 2 msh files you can use tgrid to open the first mesh and then add the second one, and finally export one total msh file.

Daniele