# [Gmsh] hybrid hexa/tetra mesh generation

Thomas Unfer thomas.unfer at laposte.net
Mon Oct 17 10:15:01 CEST 2016

```Hi,

I would like to generate a mesh with a structured hexahedral zone linked
to an unstructured tetrahedral zone
(see .geo attached). At some point I expect some nice pyramidal cells to
appear in the boundary region...

The problem is that Delaunay algorithm don't make it conforming and a
warning appears saying to turn to Frontal...
and Frontal says it can't do it with quadrangles on the boundary. Is
there a workaround?

Thanks,

Thomas
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h = 0.1;
Point(1) = {0, 0, 0, h};
Point(2) = {1, 0, 0, h};
Point(3) = {1, 1, 0, h};
Point(4) = {0, 1, 0, h};
Point(5) = {0, 0, 1, h};
Point(6) = {1, 0, 1, h};
Point(7) = {1, 1, 1, h};
Point(8) = {0, 1, 1, h};

Point(100)={1, 0, 0, h};
Point(101)={2, 0, 0, h};
Point(102)={2, 1, 0, h};
Point(103)={1, 1, 0, h};
Point(104)={1, 0, 1, h};
Point(105)={2, 0, 1, h};
Point(106)={2, 1, 1, h};
Point(107)={1, 1, 1, h};

Line(1) = {1, 2};
Line(100)={100,101};
Line(2) = {2, 3};
Line(101)={101,102};
Line(3) = {3, 4};
Line(102)={102,103};
Line(4) = {4, 1};
Line(103)={103,100};
Line(5) = {5, 6};
Line(104)={104,105};
Line(6) = {6, 7};
Line(105)={105,106};
Line(7) = {7, 8};
Line(106)={106,107};
Line(8) = {8, 5};
Line(107)={107,104};
Line(9) = {3, 7};
Line(108)={102,106};
Line(10) = {4, 8};
Line(109)={103,107};
Line(11) = {1, 5};
Line(110)={100,104};
Line(12) = {2, 6};
Line(111)={101,105};
Line Loop(13) = {2, 9, -6, -12};
Line Loop(112)={101,108,-105,-111};
Plane Surface(14) = {13};
Plane Surface(113)={112};
Line Loop(15) = {9, 7, -10, -3};
Line Loop(114)={108,106,-109,-102};
Plane Surface(16) = {15};
Plane Surface(115)={114};
Line Loop(17) = {4, 11, -8, -10};
Line Loop(116)={103,110,-107,-109};
Plane Surface(18) = {17};
Plane Surface(117)={116};
Line Loop(19) = {4, 1, 2, 3};
Line Loop(118)={103,100,101,102};
Plane Surface(20) = {19};
Plane Surface(119)={118};
Line Loop(21) = {1, 12, -5, -11};
Line Loop(120)={100,111,-104,-110};
Plane Surface(22) = {21};
Plane Surface(121)={120};
Line Loop(23) = {7, 8, 5, 6};
Line Loop(122)={106,107,104,105};
Plane Surface(24) = {23};
Plane Surface(123)={122};
Surface Loop(25) = {14, 20, 18, 22, 24, 16};
Surface Loop(124)={113,119,117,121,123,115};
Volume(26) = {25};
Volume(125)={124};

Transfinite Line{2, 9, -6, -12}=1/h+1;
Transfinite Surface{14};
Recombine Surface{14};
Transfinite Line{9, 7, -10, -3}=1/h+1;
Transfinite Surface{16};
Recombine Surface{16};
Transfinite Line{4, 11, -8, -10}=1/h+1;
Transfinite Surface{18};
Recombine Surface{18};
Transfinite Line{4, 1, 2, 3}=1/h+1;
Transfinite Surface{20};
Recombine Surface{20};
Transfinite Line{1, 12, -5, -11}=1/h+1;
Transfinite Surface{22};
Recombine Surface{22};
Transfinite Line{7, 8, 5, 6}=1/h+1;
Transfinite Surface{24};
Recombine Surface{24};

Transfinite Volume{26};
Recombine Volume{26};Coherence;
```