I’m working on a mesh with bent pipes inserted into a rectangular shape. I made divisions in the geometry so that it had hexahedra in the model, although I have a problem when trying to make the 3D mesh. I want the mesh to be hexahedral, so I select the Hexahedron algorithm for 3D, Quadrangle mapping for 2D, and Wire Discretization for 1D. When I try to calculate the mesh, I receive the error message for the Hexa_3D algorithm #530(Solid) subshape “Invalid input mesh. Can’t find 8 corners of a block by 2D mesh.” Do you have any suggestions on how I can fix this?
Hello Belisario,
You need to be sure that your geometry is box like, or be able to be decomposed into box like sub parts. I can also suggest for you to try Body fitting algorithm with optimal axes set, this may result in a purely hexahedral mesh if your geometry is regular enough, or try the same body fitting algorithm with quanta option, this will completely eliminate polyhedrons in the boundary if any. You might also try to use extrussion 3D algorithm to get a purely hexahedral mesh.
Regards,
Cesar
Hello everybody,
I have the same problem, “Invalid input mesh. Can’t find 8 corners of a block by 2D mesh”. However, I use box like shape (for a ship bulbus).
Any ideas why it doesnt work?
I attach the script
study.py (4.4 KB)
you attached an script that imports a geometry but you did not share the geometry. can you post it please?
Hello Franco,
You are absolutely right, I apologise,
Please find attached both below:
bulbus.stp (49.4 KB)
study.py (2.0 KB)
Thank you,
you need to define correctly your mesh.
I assume for the geometry that you want to mesh with struc meshing.
for this you do a global hex mesh for the complete compound 3D
global 2D quad for the compound
and 1D submeshes of each propagation group (for a cube it would be 3 groups X, Y and Z) and give the number of elements. if you want to control the correctly the mesh size. the boundary layer addition with struc meshes fails or colapses quite often (in this case it will work as your external nodes have the correct valence) but would not keep this workflow (of adding the BL) with the hypothesis as you risk of find yourself in cases where it does not work.
regards
Dear Franco,
Thank you for your quick reply,
Yes, I want to do it with stactured mesh. However, it fails, returning the below:
It doesnt recognize the shape with the negative volume (ship bulbus). In the future, I will need to mesh all the gemoetry of the ship, but for now I want to mesh only around the bulbus.
I used Hexahedron (i,j,k) for 3D algorithm, Quadrangle: Mapping for 2D algorithm and Wire Discretizarion with Number of segments for 1D algorithm. Unfortunately, the 3D algorithm does not recognize my shape as a "box’’ and it doesnt continye.
I tried using compounds (with Operations - > Blocks - > Propagate it broke into 6 pieces), made the submeshes, but it didnt work.
I think the problem is with the overall geometry that has to be separated into pieces so the software recognizes blocks.
You uploaded the study with the wrong geometry so I did not had a look at the step file. You need always to divide your cad into blocks with 6 faces and 8 vertexes.
1 Like
I apologise my dear,
I will upload the correct tomorrow and if you have the time and kindness you can have a look on them.
Good day everyone,
I managed to create a mesh on my ship bulbus geometry, using Hexahedron (i,j,k) for 3D algorithm, Quandrangle Mapping for 2D and Wire Discretisation for 1D.
Through my CAD program, I extruded the bulbus surface along y-axis, created a a 3D rectangular shape in the center of the 3D shape and and then devided the extruded bulbus shape into an additional four parts. Each part is connected with two vertices of the extruded shape.
This way I managed to create five blocks that contain 6 faces and 8 vertexes eachs, as @franco.ota mentioned above.
Below there is a view of my mesh:
Of course, for full ship simulations the domain around the bulbus must be created, but it is quite easy as a rectangular block with one face being the same face as the front face of the bulbus can be created. Also other paerts of the ship can be devided into box like blocks and construct the whole domain for ship simulations.
Also you may find attached the study:
Study1.hdf (2.9 MB)