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3D Mesh with hexahedra elements (basic question)

Posted: Tue Mar 26, 2019 10:25 pm
by Jaem
Hello, I am new in GID and I am trying to use it to generate meshes for finite element purposes. I am interested in hexahedra elements and I tried a very simple, example (i.e. a cube). To do that I created first a square using the line option in GID, then I converted this to a surface and after that I used the utility/copy tool to extrude the surface to a volume.
For the meshing I specified the element as a hexahedra and then tried to do the meshing, but I get the following message: "Volume number 1 can only be meshed with tetrahedra, and it has other element type assigned" and the mesh is not generated.
My understanding is that I should be able to do 3D meshes with hexahedra elements, but I am not sure what I am missing. Please could you offer some advice on this.
I also attach the message from GID
Thank you

Re: 3D Mesh with hexahedra elements (basic question)

Posted: Wed Mar 27, 2019 8:33 am
by abelcs
you can generate hexahedra elements within GiD if the volumes are structured or semi-structured. To do so, you need to specify one of this kind of structured type to the volume in Mesh menu.
Structured volume must have 6 contour surfaces which must be able to be meshed in a structured way (4-sided surfaces).
Semi-structured volumes must have a prismatic topology, so as the mesh is structured in the prismatic direction and the tops may have structured or unstructured mesh.
In your case (a cube), it always can be set as structured or semi-structured.