[Gmsh] Defining Physical Surface

[Christophe Geuzaine]

> On 1 Dec 2018, at 12:46, Tom Peachey <tcp.free at gmail.com> wrote:
> 
> 
> I am planning to run OpenFoam batch jobs, airfoil simulations, using gmsh for the meshing. For this I need to automate the creation of .geo files. It’s straightforward, following the Ingram tutorial
> https://community.dur.ac.uk/g.l.ingram/download/gmshtutorial2012.pdf
>  until the final stage where one defines the “Physical Surfaces”
> Physical Surface("back") = {1027};
> presumably  a surface created by the previous “Extrude” command. As Ingram says: “Finding the number associated with a particular surface is a bit of a pain.” It seems he uses the gmsh GUI which is not available in my automated scenario.
> 
> The Octave code by César A. Vecchio Toloy gives some more detail:
> fprintf (fid, 'j5[] = Extrude {0,0,%.10g} {Surface{5};Layers{1};Recombine;};\n', cuerda/10);
> fprintf (fid, 'j6[] = Extrude {0,0,%.10g} {Surface{6};Layers{1};Recombine;};\n', cuerda/10);
> followed by
> fprintf (fid, 'Physical Surface("inlet") = {j5[5],j6[5]};\n');
> But again it is not clear how to choose the correct components of j5 and j6.

Extrude returns the list of generated entities: the “top” of the extruded entity at index 0 and the extruded entity at index 1, followed by the “sides” of the extruded entity at indices 2, 3, etc. 

http://gmsh.info/dev/doc/texinfo/gmsh.html#Extrusions

Christophe


> 
> Any help greatly appreciated.
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine