Issue with "Create Boundary Mesh" and Unexpected Extra Elements in GiD

[Kaveh111]

Hello,

I encountered a problem when using the "Create Boundary Mesh" feature. After generating the boundary mesh, I exported the output using GiD Mesh, then manually removed the internal tetrahedral elements from the exported file, retaining only the triangular elements on the surfaces. I intend to keep only the surface mesh.

However, after re-importing this modified file back into GiD, I noticed an issue. When I cut through the model, in addition to the expected surface triangles, there are many extra elements that I do not recognize or understand. The outer layer looks fine (see Figure 02), but as shown in Figure 03 (interior layer), numerous unexpected elements appear within the model.

Could you please help me identify the cause of this issue and suggest a way to fix it?

Thank you in advance.

Best regards,
Kaveh

[escolano]

Maybe you did manually something wrong editing the mesh file.
To have only the boundary mesh and delete the volume mesh you don't need to export and to complicated tasks.
Simply create a new layer, that is set as 'layer to use'
then create the boundary mesh, will be created in this layer
then can select and delete the rest of layers to delte all its entities
(or delete the volume elements selecting them, it is easier setting off the layer with the triangles)
or while selecting elements to delete can use a filter
filter:elementtype=tetrahedra
and then will select only tetras, not triangles, also if are in the same layer

[Kaveh111]

I encountered a problem while using the "Create Boundary Mesh" feature.

The second time I used it, I created a new layer and set it as the "Layer to Use." I then created the boundary mesh, which was successfully generated in this new layer. After that, I was able to select and delete the other layers to remove all their entities.

However, after making these changes, I noticed the same issue again. I expected the software to consider only the triangular elements (free faces) when generating the boundary mesh. Instead, it seems to include some elements from inside the volume.

I’ve uploaded an image showing the problem.

Could you please help me identify the cause of this issue and suggest a possible solution?

[escolano]

Attach a zip with your GiD model with the volume mesh (before create the boundary mesh)