Obtain a compatible mesh between two isolated volumes.

[Rolando]

Dear all,

Here is my problem, I have one volume (composed by thin beam and column elements) partially embedded within another volume (a geometry of a building, certainly irregular). As I understand, both volumes are treated as "isolated" and have each one a corresponding layer. I imported them as IGES file from AutoCAD file. My question is: how can I obtain a compatible mesh between them without executing any boolean operation to join?

I did unstructured meshing as default and there are no connections between nodes in the interface of the volumes. Also, I need to keep each volume information as (node locations, elements, etc) and this seems to be lost when I joined volumes.

I would really appreciate your help with this!!!

[escolano]

It seems that do you have two independent and overlapped volumes, the mesh will be also two independent and overlapped tetrahedra.

It is necessary that the surfaces of the two volumes are a single surface shared by both volumes.
This require do the intersection and split of the intersecting surfaces (and the curves).
(if fact these are some of the operations that a boolean operation must do)

If do you want attach a zip of the model to have a look.

[Rolando]

Dear @escolano,

Thanks for your comment! I am not really sure what tool can I use to hare surfaces between both volumes. I attached you the file, so you can take a look.

I'd really appreciate if you can provide me some more clues to solve this mesh.

Thanks again!

[escolano]

In this case the model is good, because the volumes really are not overlapped,
and it is not necessary do calculate intersections, split entities, etc.
But each volume has its own copy of the surfaces, lines and points, without share it with the neighbor volume.
You can simply to a
Geometry->Edit->Collapse->Model
with a appropriated tolerance, the default automatic value seems ok (Utilities->Preferences... Import and export->Import tolerance)
this will join points, close than the tolerance distance, and also lines and surfaces.

I attach my model, it has assigned 'Mesh->Unstructured->Sizes by chordal error=0.02' (to set a finer size to the curved columns)

Mallado_RecDominica_INTERV_Ene2022_collapsed.zip

(3.75 MiB) Downloaded 562 times

It is meshed with Tetgen volume mesher (Preferences... Meshing->Structuration type)
and general mesh size=1.0
(the attached model don't include the mesh, to avoid a file of big size)

[Rolando]

Thanks a lot for your response and shared model!

I'll take a look to build the mesh following your recommendations and I hope it works fine at last!

Thanks a lot again!

[spiceagent11]

I try to create a quadrilateral mesh for a fill section on a foundation with different size (small size at the middle, under the fill and big size outside of the fill).

I can't find the correct way to have a good quadrilateral meshing. I don't know if the best way to do that is to create many section element?

[escolano]

You can assign mesh sizes to the points, lines,
and set in preferences some parameters like the 'transition mesh size', that controls how fast the mesh size grows or decrease

Take into account that the mesh generation first generate the mesh of the boundary, then these boundary mesh sizes are crucial, and probably won't be possible to decrease in the center so much as you want.

To have more meshing control you can split your surface, then you will be able to set a small size to some parts.

[Rolando]

Dear escolano,

I have thoroughly reviewed the model and followed the instructions as you kindly suggested. In a general sense, there is a big improvement in the connections of mostly all nodes-elements between the involved volumes.

However, I've been struggling with the remaining disconnections, trying with different configurations in preferences, but still, there are certain surface not fully connected (as I attached in the documents).

Do you have any suggestions about this?

Thanks a lot for your help.

Rolando,

[escolano]

The mesh is not conformal in this part because the surfaces are not divided by the line and then the entities are not shared
The geometry is not connected, ant then the mesh is not connected.

You must split the surface
menu: Geometry->Edit->Divide surface->Split
And select the surface to be splitted (the gray one), and then the collection on lines that separate the surface in two regions (the lines of intersection with the green surface)

Then the old surface is replaced two new surfaces (and the volume is updated with the new surfaces)

Now do you have two ‘equal surfaces’ overlapped, to have a single surface shared by both volumes use the collapse of surfaces:
(with a small tolerance, e.g. using the default automatic import tolerance of preferences)

menu: Geometry->Edit->Collapse->Surfaces
and select the two surfaces.

[Rolando]

Thanks escolano,

I think it worked! I'm going for further analysis and hopes it runs right !

Many thanks for your assistance!