[Gmsh] hybrid prism/tetrahedrons mesh

[Hoessler, Julien]

Good afternoon everybody,
I am trying to build an unstructured tetrahedron mesh with a layer of=20
prisms on one of the delimiting surfaces. I thus extrude and recombine=20
all the surfacic zones of this wall to generate the layer. But when I=20
then mesh the rest of the volume with tetrahedrons, I end up with a=20
few groups of two triangles at the interface that seem to have been=20
recombined into a quad and splitted along the wrong diagonal (all the=20
nodes are matching). I have tried to remove the smoothing/optimisation=20
steps on the netgen/tetgen process, but it doesn't change much. Is=20
there a way to make the extrusion only after the end of the volumic=20
mesh of the tetrahedrons regions, or to avoid modifying the surfacic=20
meshes? Am I doing it the wrong way?
Thanks for your help

Best regards
Julien Hoessler

Below is the geo file:
//*********** PARAMS *************//
//Domain box
lx =3D 25;
ly =3D 25;
lz =3D 50;
//High resolution box
bz1 =3D 15;
bz2 =3D 30;
bx1 =3D 5;
bx2 =3D 0;
bx3 =3D 10;
bx4 =3D 2.5;
bx5 =3D 10;
by1 =3D 5;
by2 =3D 7.5;
by3 =3D 10;
//buffer box
dx =3D 2.5;
dy =3D 2.5;
dz =3D 2.5;
ryI =3D 7;
rb  =3D 1.00;
rb2 =3D 1.5;
rdI =3D 5;
rdO =3D 7.5;
//*********** POINTS *************//
//Points domain
Point(1) =3D {-lx,1,0,rdI};
Point(2) =3D {lx,1,0,rdI};
Point(3) =3D {lx,ly,0,rdI};
Point(4) =3D {-lx,ly,0,rdI};
Point(5) =3D {lx,1,lz,rdO};
Point(6) =3D {-lx,1,lz,rdO};
Point(7) =3D {-lx,ly,lz,rdO};
Point(8) =3D {lx,ly,lz,rdO};
//Points high resolution box
Point(9) =3D {-bx1,1,0,rb};
Point(10) =3D {bx1,1,0,rb};
Point(11) =3D {bx2,1,bz1,rb};
Point(12) =3D {bx3,1,bz1,rb};
Point(13) =3D {bx4,1,bz2,rb};
Point(14) =3D {bx5,1,bz2,rb};
Point(15) =3D {-bx1,by1,0,rb};
Point(16) =3D {bx1,by1,0,rb};
Point(17) =3D {bx2,by2,bz1,rb};
Point(18) =3D {bx3,by2,bz1,rb};
Point(19) =3D {bx4,by3,bz2,rb};
Point(20) =3D {bx5,by3,bz2,rb};
//Points buffer zone
Point(21) =3D {-bx1-dx,1,0,rb2};
Point(22) =3D {bx1+dx,1,0,rb2};
Point(23) =3D {bx2-dx,1,bz1,rb2};
Point(24) =3D {bx3+dx,1,bz1,rb2};
Point(25) =3D {bx4-dx,1,bz2+dz,rb2};
Point(26) =3D {bx5+dx,1,bz2+dz,rb2};
Point(27) =3D {-bx1-dx,by1+dy,0,rb2};
Point(28) =3D {bx1+dx,by1+dy,0,rb2};
Point(29) =3D {bx2-dx,by2+dy,bz1,rb2};
Point(30) =3D {bx3+dx,by2+dy,bz1,rb2};
Point(31) =3D {bx4-dx,by3+dy,bz2+dz,rb2};
Point(32) =3D {bx5+dx,by3+dy,bz2+dz,rb2};
//*********** LINES *************//
Line(1) =3D {2,22};
Line(2) =3D {22,10};
Line(3) =3D {10,9};
Line(4) =3D {9,21};
Line(5) =3D {21,1};
Line(6) =3D {1,4};
Line(7) =3D {4,3};
Line(8) =3D {3,2};
Line(9) =3D {2,5};
Line(10) =3D {5,8};
Line(11) =3D {8,7};
Line(12) =3D {5,6};
Line(13) =3D {6,7};
Line(14) =3D {7,4};
Line(15) =3D {1,6};
Line(16) =3D {22,24};
Line(17) =3D {26,24};
Line(18) =3D {26,25};
Line(19) =3D {25,23};
Line(20) =3D {23,21};
Line(21) =3D {21,27};
Line(22) =3D {27,29};
Line(23) =3D {29,31};
Line(24) =3D {31,32};
Line(25) =3D {32,26};
Line(26) =3D {25,31};
Line(27) =3D {23,29};
Line(28) =3D {30,24};
Line(29) =3D {22,28};
Line(30) =3D {28,27};
Line(31) =3D {28,30};
Line(32) =3D {30,32};
Line(33) =3D {30,29};
Line(34) =3D {8,3};
Line(35) =3D {10,16};
Line(36) =3D {16,15};
Line(37) =3D {15,9};
Line(38) =3D {12,18};
Line(39) =3D {17,11};
Line(40) =3D {10,12};
Line(41) =3D {9,11};
Line(42) =3D {12,14};
Line(43) =3D {14,13};
Line(44) =3D {13,11};
Line(45) =3D {17,19};
Line(46) =3D {19,20};
Line(47) =3D {20,18};
Line(48) =3D {19,13};
Line(49) =3D {14,20};
Line(50) =3D {17,15};
Line(51) =3D {16,18};
//*********** SURFACES *************//
Line Loop(52) =3D {1,16,-17,18,19,20,5,15,-12,-9};
Plane Surface(53) =3D {52};
Line Loop(54) =3D {2,40,42,43,44,-41,4,-20,-19,-18,17,-16};
Plane Surface(55) =3D {54};
Line Loop(56) =3D {40,42,43,44,-41,-3};
Plane Surface(57) =3D {56};
Line Loop(58) =3D {35,36,37,-3};
Plane Surface(59) =3D {58};
Line Loop(60) =3D {35,51,-38,-40};
Plane Surface(61) =3D {60};
Line Loop(62) =3D {47,-38,42,49};
Plane Surface(63) =3D {62};
Line Loop(64) =3D {46,-49,43,-48};
Plane Surface(65) =3D {64};
Line Loop(66) =3D {44,-39,45,48};
Plane Surface(67) =3D {66};
Line Loop(68) =3D {50,37,41,-39};
Plane Surface(69) =3D {68};
Line Loop(70) =3D {2,35,36,37,4,21,-30,-29};
Plane Surface(71) =3D {70};
Line Loop(72) =3D {50,-36,51,-47,-46,-45};
Plane Surface(73) =3D {72};
Line Loop(74) =3D {20,21,22,-27};
Plane Surface(75) =3D {74};
Line Loop(76) =3D {23,-26,19,27};
Plane Surface(77) =3D {76};
Line Loop(78) =3D {18,26,24,25};
Plane Surface(79) =3D {78};
Line Loop(80) =3D {32,25,17,-28};
Plane Surface(81) =3D {80};
Line Loop(82) =3D {31,28,-16,29};
Plane Surface(83) =3D {82};
Line Loop(84) =3D {30,22,-33,-31};
Plane Surface(85) =3D {84};
Line Loop(86) =3D {32,-24,-23,-33};
Plane Surface(87) =3D {86};
Line Loop(88) =3D {6,7,8,1,29,30,-21,5};
Plane Surface(89) =3D {88};
Line Loop(90) =3D {14,-6,15,13};
Plane Surface(91) =3D {90};
Line Loop(92) =3D {11,-13,-12,10};
Plane Surface(93) =3D {92};
Line Loop(94) =3D {10,34,8,9};
Plane Surface(95) =3D {94};
Line Loop(96) =3D {34,-7,-14,-11};
Plane Surface(97) =3D {96};
//*********** VOLUMES *************//
Surface Loop(98) =3D {53,89,91,97,95,93,77,87,81,79,83,85,75};
Volume(99) =3D {98};
Surface Loop(100) =3D {79,77,87,81,83,85,75,55,71,63,73,69,67,65,61};
Volume(101) =3D {100};
Surface Loop(102) =3D {65,73,69,67,61,63,57,59};
Volume(103) =3D {102};
//*********** EXTRUSIONS *************//
outv[]=3D Extrude {0,-1,0}{ Surface{53,55,57}; Layers{2};};
//*********** B CONDITIONS *************//
Physical Surface(101) =3D {155,249,217};
Physical Surface(102) =3D {91,146,154,95,89,71,59,248,172,196,142,118};
Physical Surface(100) =3D {97};
Physical Surface(103) =3D {93,150};
Physical Volume(150) =3D {105,104,103,106,101,99};