# [Gmsh] Help with making a volume mesh

Vincent Huber vincent.huber at cemosis.fr
Sat Jan 30 15:08:54 CET 2016

```Hello Brian,

It is not crystal clear to me what you want to do.
But you’ll find in the following a working geometry (with comments).
By the way, I guess the wrong command on your code is the Layers in the
extrude section.
Last remark: I think it is easier to construct the first 2 volumes (say on
the left) and then make the symmetry.

I’m pretty sure you will reach your goal with that.

mcl = 0.25;
// You should consider using p1 = newp; Point (p1) = ...; p2 = newp
.... That helps a lot !
Point(1000) = {9.40, 5.5, 0, mcl};
Point(1003) = {9.40, 6.6, 0, mcl};
Point(1004) = {8.68, 6.6, 0, mcl};
Point(1005) = {7.91, 5.5, 0, mcl};
Point(1006) = {8.25, 6.6, 0, mcl};
Point(1007) = {7.83, 6.6, 0, mcl};
Point(1008) = {7.39, 6.6, 0, mcl};
Point(1009) = {6.84, 6.6, 0, mcl};
Point(1010) = {5.97, 6.6, 0, mcl};
Point(1011) = {4.89, 6.6, 0, mcl};
Point(1012) = {3.71, 6.6, 0, mcl};
Point(1013) = {3.43, 6.0, 0, mcl};
Point(1014) = {4.05, 5.5, 0, mcl};
Point(1015) = {5.45, 5.5, 0, mcl};
Point(1016) = {6.1, 5.5, 0, mcl};
Point(1017) = {6.93, 5.5, 0, mcl};
Point(1018) = {7.20, 5.5, 0, mcl};
Point(1019) = {7.52, 5.5, 0, mcl};
Point(1020) = {8.5, 5.5, 0, mcl};
Point(1021) = {9.4, 1.82, 0, mcl};
Point(1022) = {6.12, 2.27, 0, mcl};
Point(1023) = {3.22, 3.63, 0, mcl};
Point(1024) = {2.02, 6.11, 0, mcl};
Point(1025) = {3.15, 8.27, 0, mcl};
Point(1026) = {5.5, 9.0, 0, mcl};
Point(1027) = {8.2, 9.5, 0, mcl};
Point(1028) = {9.4, 9.75, 0, mcl};

// Idem here: l1 = newl; Line (l1) = ....
// First outer line
Line(1036) = {1003, 1004};
Spline(1037) = {1004, 1006, 1007, 1008, 1009};
Spline(1038) = {1009, 1010, 1011, 1012, 1013, 1014, 1015, 1016};
Line(1039) = {1016, 1017};
Line(1040) = {1017, 1018};
Spline(1041) = {1018, 1019, 1005, 1020};
Line(1042) = {1020, 1000};

//Second outer line
// I'll write FirstLL[] += newl; Spline(FirstLL[#FirstLL[]-1]) = ....
Spline(1030) = {1021, 1022, 1023, 1024, 1025, 1026};
Spline(1031) = {1026, 1027, 1028};

// Actually, we should duplicates contour by contour to let us write
// ll1 = newll; Line Loop(ll1) = {FirstLL[], ll1[]};
ll[] += Symmetry {1.0, 0.0, 0.0, -9.4} {
Duplicata{Line{1031,1030,1036,1037,1038,1039,1040,1041,1042};} };
For i In {0:#ll[]-1}
Printf("ll[%g] = %g",i,ll[i]);
EndFor

ll1 = newll; Line Loop(ll1) = {1030,1031,-1043,-1044};
ll2 = newll; Line Loop(ll2) =
{1036,1037,1038,1039,1040,1041,1042,-1051,-1050,-1049,-1048,-1047,-1046,-1045};

// Only two surfaces
// If you want 4 (to produce 4 volumes) you only have to modify the
upper line loops)
s1 = news; Plane Surface(s1) = {ll1,-ll2};
s2 = news; Plane Surface(s2) = {ll2};

// one extrusion to produce two volumes.
Extrude {0, 0, 10} {
Surface{s1,s2};
Layers{10};
Recombine;
}

All the best,

VH
​

2016-01-29 21:00 GMT+01:00 Brian Drawert <brian at drawert.net>:

> Hi Gmsh mailing list,
>
> I am kinda new to Gmsh, and have yet to find a good resource to answer my
> questions.  I am hoping that someone on the list can help me.
>
> I have attached a mesh.  It it, I am making a mesh that have 4 volumes,
> and is symmetric along the YZ plane, and uniform along the z-axis.  On each
> side, there is an inner volume that inside the outer volume.  I am drawing
> the points along the left z=0 surface, mirroring to the right side, then
> extruding the surfaces to make the volumes.  However, when try to mesh with
> a 3D mesh, I get lots of errors about “Could not find extruded vertex” (41
> errors), and I am not extruding the right side.  When this is done the mesh
> looks unphysical (see attached screenshot v2.11 on OSX).
>
> I also tried to make this mesh using a surface loop, but I was unable to
> figure out how to use translate or symmetry to duplicate a line loop, so I
> could not make a complete surface.
>
> Any assistance or pointers to where I might find documentation on how to
> compete this process would be greatly appreciated.
>
> Thanks,
>   Brian
>
>
>
>
>
>
> _______________________________________________
> gmsh mailing list
> gmsh at onelab.info
> http://onelab.info/mailman/listinfo/gmsh
>
>

--
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CeMoSiS <http://www.cemosis.fr> - vincent.huber at cemosis.fr
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