How to make the connection between the surface and the body when it is divided

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Amors
Posts: 18
Joined: Mon Jun 19, 2023 1:34 am

How to make the connection between the surface and the body when it is divided

Post by Amors »

Hi, sir
Hello, I want to use Delauny grid for subdivision of the entire model. I have to encrypt the center of the surface and then subdivision. However, after I finish subdivision, the middle surface has no correlation with the grid subdivided by the upper and lower bodies. In other words, the grid of the generated body is based on the plane where two entities intersect, but I don't know how to establish such a connection. Below, I have provided a schematic diagram of the model I want to make, could you provide some guidance? At the same time, I would like to ask whether GID software can provide the division of V grid.
Thank you,
Best regrads.
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escolano
Posts: 1938
Joined: Sun Sep 05, 1982 10:51 pm

Re: How to make the connection between the surface and the body when it is divided

Post by escolano »

Sorry, I don't understand your question at all.

In GiD the normal approach is to create a geometry and then generate the mesh (Delaunay or other method, in general advancing front provide better mesh quality)

You must create a volume with a hole, and create other volume filling the hole.
and the surfaces between them must be the same, not duplicated, then the mesh of both volumes is conformal.
If a collection of surfaces divide a volume in two or more regions, and use this to split the volume in two volumes.
Geometry->Edit->Divide->Volume->Split

Why to divide the mesh?
You can simply assign the required mesh sizes to the entities and generate the mesh you want.

In general with GiD it's unrecommended to do 'manual' operations in the mesh, but you can split a selection of elements, and its edges will be divided in two. Boundary conditions are in theory preserved (applied to the new elements or its faces)
Mesh->Edit mesh->Split
Amors
Posts: 18
Joined: Mon Jun 19, 2023 1:34 am

Re: How to make the connection between the surface and the body when it is divided

Post by Amors »

Thank you very mesh for your advice

I can talk about what I want again. I have two volumes, named as A and B and all meshed by Tetgen scheme, and they can be assigned into two layers. Now, I want to insert a "surface" C, on the top left corner of the picture, into the interface between two volume. So, I should have three layers that are volume A, surface C, and volume B from top to bottom of model. However, I have no idea to implement the work of surface C. Further, I need to consider the meshing strategy of the surface C, such as the region of triangle need to be finely discretized. Whether I need to treat the interfaces between the volume A and surface C, and the surface C and volume B? I require some advice and guidance.

Best wishes
Amors
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escolano
Posts: 1938
Joined: Sun Sep 05, 1982 10:51 pm

Re: How to make the connection between the surface and the body when it is divided

Post by escolano »

I continue without understanding your questions at all,
attach the GiD zip model with the complete geometry that you want to reach.

In general GiD works creating a geometry, and then GiD mesh it, all in a step, not in increasing steps.

GiD has inside a Tetgen to mesh, but i have the impression that you are using some tetgen as external mesher, and are importing his meshes. Then GiD is not able to modify these meshes to insert other parts, must create a geometry a generate a completely new mesh.

And it is not possible to generate a mesh of a volume with a 'embedded surface'. The volume mesh won't fit this surface. The surface must belong to the boundary of the volume (must split the volume in two volumes, creating extra auxiliary surfaces if require to separe in tho volumes)
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escolano
Posts: 1938
Joined: Sun Sep 05, 1982 10:51 pm

Re: How to make the connection between the surface and the body when it is divided

Post by escolano »

Reading once more your question, maybe you simply want two volumes, with the same surface (and its lines and points( shape duplicated, one for each volume,
and then want also an extra 'GiD contact volume' between the two surfaces on the same 3D location. This pseudo-volume has 0 width, and is a way to force a 1-1 relationship between the mesh of both surfaces, and additionally can generate flat elements (prisms if surfaces have triangles), that some simulation codes use to describe the contact between both volumes.

You cannot use any mesh as starting model, must have geometry.

Simply create both volumes, without share any entity
(if share entities can use Geometry->Edit->Uncollapse->Volumes)
the create the contact volume
Geometry->Create->Contact->Volume
and select the two 'equal surfaces'
and then generate the mesh (with the GiD mesher that you prefer)
Before can assign mesh sizes to geometrical entities to have a finer mesh in some regions
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