[Gmsh] Retaining a Specified Surface mesh

[Hines, Albert M.]

I am working with multiple materials and need to maintain a coincident interface between them. How do I impose, rather than request, the triangular surface mesh? I thought I might just remove line 5 in the following msh file, but that doesn't work properly. Sorry if the solution should be so obvious.

Albert Hines 

------    Command file:
gmsh -3 -optimize -o foo3d.mesh foo.geo

------    geo file:
Merge "foo.msh";
Surface Loop(1) = {0};
Volume(2) = {1};
Physical Volume(3) = {2};
Physical Surface(4) = {0};
Physical Volume(5) = {2};
Physical Volume(6) = {2};

------    Example msh file:
$MeshFormat
2 0 8
$EndMeshFormat
$Nodes
81
1 0.00 14.950374 4.67 
2 40.00 14.950374 4.67 
3 40.00 14.950374 32.67 
4 0.00 46.894374 32.67 
5 40.00 46.894374 4.67 
6 0.00 46.894374 4.67 
7 0.00 14.950374 32.67 
8 40.00 46.894374 32.67 
9 26.156733 38.802862 4.67 
10 13.232826 27.886074 32.67 
11 13.901681 23.087227 4.67 
12 13.898714 38.756954 32.67 
13 31.371396 14.950374 18.666042 
14 0.00 36.246374 4.67 
15 0.00 25.598374 4.67 
16 0.00 14.950374 18.67 
17 13.333333 14.950374 4.67 
18 8.675905 14.950374 18.665986 
19 26.67 14.950374 4.67 
20 20.073706 14.950374 18.628897 
21 0.00 30.922374 18.67 
22 0.00 36.246374 32.67 
23 0.00 25.598374 32.67 
24 13.238040 33.953158 4.67 
25 26.766683 27.896308 4.67 
26 26.67 14.950374 32.67 
27 26.038735 23.131066 32.67 
28 8.674856 46.894374 18.666020 
29 40.00 25.598374 4.67 
30 40.00 14.950374 18.67 
31 40.00 36.246374 4.67 
32 40.00 25.598374 32.67 
33 40.00 30.922374 18.67 
34 0.00 22.533610 16.548446 
35 0.00 39.311139 20.784887 
36 26.780767 33.944022 32.67 
37 13.333333 14.950374 32.67 
38 40.00 21.860046 18.67 
39 32.498627 39.013604 26.888102 
40 40.00 39.984702 18.67 
41 7.325423 38.776059 25.983796 
42 32.873119 38.957417 10.389433 
43 31.370351 46.894374 18.666070 
44 40.00 36.246374 32.67 
45 20.070431 46.894374 18.630690 
46 26.771601 24.635792 27.351513 
47 13.333333 46.894374 4.67 
48 13.333333 46.894374 32.67 
49 26.67 46.894374 32.67 
50 0.00 46.894374 18.67 
51 26.67 46.894374 4.67 
52 40.00 46.894374 18.67 
53 32.670101 22.999166 25.986060 
54 7.552356 22.793872 27.028598 
55 7.666118 38.781489 11.287107 
56 7.085597 22.816802 10.432222 
57 32.332081 22.990342 11.289589 
58 31.784001 27.906110 11.024495 
59 33.737651 39.532733 18.660776 
60 20.173019 38.401052 10.247800 
61 8.832577 30.842009 10.072787 
62 19.723145 22.565474 10.780383 
63 33.814744 22.290879 18.608319 
64 32.648119 31.002834 26.512222 
65 34.518094 33.044349 20.645245 
66 34.331170 33.492149 14.808686 
67 34.391818 27.389065 21.534335 
68 34.957037 27.921636 16.051564 
69 7.361153 30.784268 26.512409 
70 19.897685 39.097561 26.767356 
71 17.461577 22.580041 26.834627 
72 23.682731 31.804076 27.828776 
73 14.522371 31.251126 27.838004 
74 6.258268 22.245022 18.759467 
75 6.178561 39.484080 18.605181 
76 5.151544 27.999832 16.883967 
77 5.106018 34.149606 18.448810 
78 14.436685 21.277825 18.334327 
79 24.421351 21.058309 18.872031 
80 25.185021 40.346122 18.538136 
81 15.219453 40.083006 18.517528 
$EndNodes
$Elements
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$EndElements