[CIG-SEISMO] specfem2d basin model mesh generation

[cristini]

Hello,

This is not a problem with the python script but with your geometry file 
which is not correct. In particular, the definition of the top line is 
not good, the top line is the assembly of all lines you called 'Top of 
the box'. I enclose the corrected geometry file.
Then I guess that the run of the script will be ok.
Let me know if this is not the case.

Best regards

Paul
Le 19/02/2014 08:49, Phil Cummins a écrit :
> Hello,
>
> I'm new to specfem2d and am trying to help a student use it to do 2D 
> modelling of seismic waves in a sedimentary basin. We started by 
> trying to make a mesh of a simple, rectangular basin (see attached 
> figure, whole domain is 30 km x 5 km, basin is 20km x 1 km). We used 
> Gmsh so that we can have much smaller elements in the basin than 
> outside. The only way we were able to get this to work with Gmsh was 
> to define a rectangular domain, cut out a hole where the basin is, 
> then insert a 2nd rectangular domain for the basin, and finally 
> recombine the surfaces interior and exterior to the basin. (see 
> attached .geo file if your interested - I know it sounds more 
> calculated than it should be).
>
> At the end of the day, when we use the script LibGmsh2Specfem.py to 
> convert the gmsh output to specfem2d format, we appear to lose all the 
> elements in the basin, and none of the elements are recognized as 
> being along the free surface.
>
> I would be very grateful if anyone could show us what we are doing 
> wrong. What might work better though, is to have a simple example to 
> follow. Has anyone worked on a similar problem and if so would they be 
> willing to send me their gmsh (or perhaps cubit) file that I could use 
> as an example?
>
> Many thanks,
>
> - Phil
>
>
>
>
> _______________________________________________
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-- 
*--------------------------------------------------------------------------*
  Paul CRISTINI  Charge de Recherche CNRS / CNRS Research Scientist
  --------
  CNRS - Laboratoire de Mecanique et d'Acoustique (UPR 7051)

  31 chemin Joseph Aiguier, F-13402 Marseille Cedex 20 - France
  mailto: cristini at lma.cnrs-mrs.fr
  phone number: +33 (0)4 91 16 42 89
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cl__1 = 150;
cl__2 = 50;
Point(1) = {0, 0, 0, 150};
Point(2) = {30000, -5000, 0, 150};
Point(3) = {30000, 0, 0, 150};
Point(4) = {0, -5000, 0, 150};
Point(5) = {7500, 0, 0, 150};
Point(6) = {22500, 0, 0, 150};
Point(7) = {22500, -1000, 0, 150};
Point(8) = {7500, -1000, 0, 150};
Point(9) = {7500, 0, 0, 50};
Point(10) = {22500, 0, 0, 50};
Point(11) = {22500, -1000, 0, 50};
Point(12) = {7500, -1000, 0, 50};
// Left wall
Line(1) = {1, 4};
// Bottom of the box
Line(2) = {4, 2};
//Right wall
Line(3) = {2, 3};
//Top of the box
Line(4) = {3, 6};
// Right Boundary
Line(5) = {6, 7};
// Lower Boundary
Line(6) = {7, 8};
// Left Boundary
Line(7) = {8, 5};
//Top of the box
Line(8) = {5, 1};
// Top of the box
Line(9) = {9, 10};
//Lower Boundary
Line(10) = {11, 12};
// Left Boundary
Line(11) = {9, 12};
// Right Boundary
Line(12) = {10, 11};
Line Loop(14) = {9, 12, 10, -11};
// overlying box
Plane Surface(14) = {14};
// underlying box
Line Loop(16) = {8, 1, 2, 3, 4, 5, 6, 7};
Plane Surface(16) = {16};
Recombine Surface{14,16};
Mesh.SubdivisionAlgorithm=1;
Physical Line("Top") = {8,9,4};
Physical Line("Left") = {1};
Physical Line("Bottom") = {2};
Physical Line("Right") = {3};
Physical Surface("M1") = {14};
Physical Surface("M2") = {16};