Re: [Libmesh-users] gmsh reader of lower-dimensional elements - gmsh_io.C

[mlesueur <mar...@ec...>]

Hi John,
Sorry for the delay, I was away for the two last weeks.
Thanks for your help, here is one sample gmsh file.
Did you have time to look at the documentation ?

If you find my solution reasonable, is there a way to include it in 
Libmesh ? For everyone to use.
Cheers,

Martin

Le 13/08/2015 01:30, John Peterson a écrit :
>
>
> On Mon, Aug 10, 2015 at 11:02 PM, mlesueur 
> <mar...@ec... 
> <mailto:mar...@ec...>> wrote:
>
>     Hi everyone,
>     I am using Moose Framework I have been working on getting a mesh that
>     can be read by libmesh, with 2D fractures in a 3D rock matrix.
>     I am using the .msh format for my mesh. The gmsh reader of Moose
>     wasn't
>     able to recognize those 2D blocks in a 3D domain as it only assigned
>     them as sidesets.
>
>
> Yes, that was the initial design we went with, as lower-dimensional 
> elements seemed to be the natural way that Gmsh specified BCs.
>
>     So I changed a bit the file gmsh_io.C and it's now working for me. In
>     order to do that however, I had to add a keyword in my Gmsh file in
>     order to treat it slightly differently in the gmsh_io.C reader
>     function.
>     My question to the list is therefore simple: which solution do you
>     recommend to make this work in the proper way?
>
>
> I see that you've made your changes available via github 
> (https://github.com/pou036/redback/wiki/gmsh_io.C) so I'll take a 
> look.  Can you please also post a (small!) sample modified gmsh file 
> that works with your modified reader?
>
>     My current hack is to add an extra keyword in the .msh file in the
>     $PhyisicalNames paragraph, at the end of the line defining the tag
>     that
>     we want to consider as a lower dimensional block (instead of a
>     sideset).
>     Since the gmsh_io.C reader function doesn't currently use that
>     information, it's not breaking anything. Also, Gmsh itself doesn't
>     seem
>     to bother and can still read the file. But I understand that it might
>     not be the best solution since it changes (very slightly) the official
>     Gmsh format...
>
>
> This seems like a reasonable approach to me as far as the file format 
> is concerned.  As I understand it, the tags are for user-specified 
> information, so declaring that a set of lower-dimensional elements are 
> actually elements and not sidesets is a reasonable use case.
>
> However, this doesn't seem particularly convenient from your (and your 
> users') point of view, since you have to manually edit the Gmsh file 
> for it to work...?  I guess it's a question of how you use Gmsh.  What 
> you are doing may not be supported through the GUI, but I suspect it 
> could be scripted.  From what I recall, Gmsh is fairly scriptable...
>
>
>     By the way, what is the proper way to compile a single file in the
>     libmesh subdirectory?
>
>
> Just run 'make install' from your libmesh directory. It should detect 
> any files that changed, rebuild them, and install them to the 
> appropriate location.
>
> --
> John
>