[Gmsh] Gmsh Issue for constraint volume meshing

[Christophe Geuzaine]

> On 14 Oct 2019, at 11:35, Sanghavi, Chaitanya <chaitanya.sanghavi at siemens.com> wrote:
> 
>  
>  
> Dear Sir,
>  
> Good morning, 
>  
> I would like to generate a 3D mesh for a cube from a predefined 2D surface mesh on one of the faces of the 3D cube.
>  
> This is very similar to the post below, and I was made aware that this functionality is included in the latest Gmsh version.
>  
> Link : http://onelab.info/pipermail/gmsh/2006/001866.html
>  
> I tried this methodology, without much success. 
>  
> The process I try:
>  
> 	• Create a Duct.geo file which meshes a unit sized cube 1x1x1 [m] and produces mesh.msh file.
>  
> <image002.jpg>
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> 	• Create a surface mesh which contains the nodes, elements, physical surfaces.  (duct_interface.msh)
>  
>  
> 	• Merge the .msh file into the another geo file, Liner.geo. Importing this file in the latest version of Gmsh results in some errors, LinerLog. These errors or bugs are due to lack of default options specification in the geo file. 

The errors are harmless: they are due to the fact that you have a Gmsh option file with deprecated options on your system. You remove the option file with "Help->Restore all options to default settings".

> However I see the mesh imported on the surface.
>  
> <image008.jpg>
> 	• Generate a surface mesh with the above file. This produces a surface mesh without any issues and warnings and also avoids meshing on the pre-defined discrete surface mesh.
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> <image009.jpg>
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>  
> 	• Meshing in produces errors saying the element facet intersect.  (Refer ErrorBug file)
>  

The mesh you are loading does not contain the full topology: in particular it does not contain the boundary (curve) mesh of the square. When you mesh the geometry you thus indeed generate overlapping meshes, which will prevent 3D meshing.

Christophe


>  
> I have one question regarding this: 
>  
> 	• Is there a way to use the nodes defined in the duct_interface.msh to define the line  and surface loops for the second geometry ?
> I can see the nodes duplicated in the surface mesh.
>  
> Could this be the reason to not produce the volume mesh in the second cube ?
>  
>  
> I would like to thank and appreciate your efforts for the help provided.
>  
>  
> Regards
> Chaitanya
>  
>  
>  
>  
> <mesh.msh><duct_interface.msh><Liner.geo><LinerLog><ErrorBug>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine