Fabian wrote:
Hi,
I just saw the geometry and wonder, if there is a chance to extrude the
sure: cf. attached file.
surfaces and create a transfinite volume?
It's probably not working due to more than six surfaces building the
volumen!? Would be nice, if this would work, though...
Fabian
Christophe Geuzaine wrote:
Durufle Marc wrote:
Hi,
I have two questions :
1- How do you create hybrid meshes in 2-D (quad-dominant with a few
triangles) ?
Until now, I am using the Recombine option, but often I get non-convex
quadrilaterals.
In the picture attached to this message, you can see that two elements
(in black) are non-convex
quads and that's a problem ... So, often I change the characterisc
length in the hope that I will have only
fine quadrilaterals. Is it possible to require that all quadrilaterals
are convex ?
Yes. In your file you use
Recombine Surface {1,s0[0]} = 100;
which means that you allow quads with angles between 90-100 and 90+100
degrees (which does not make sense).
Use
Recombine Surface {1,s0[0]} = 45;
instead, which will allow angles between 90-45=45 and 90+45=135 degrees.
(45 is the default if you don't specify anything, i.e., with just
"Recombine Surface {1,s0[0]}".)
We are working on an automatic full quad algorithm, but it's not ready
yet. In the meantime for simple geometries you could also use
Transfinite meshes to generate a full quad mesh (see attached file).
2- In 3-D, when I try "Recombine Volume", it doesn't work. So, how is it
possible with gmsh
to create 3-D hexahedral-dominant meshes (with some tets, pyramids and
wedges) ?
Non. Your only choices for generating hex/prism/pyramid meshes are
extruded (see "Extrude Surface") or transfinite (see "Transfinite
Volume") grids.
Thank you for your help.
PS : I am using gmsh 2.24
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--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine
// The simplest construction of Gmsh's scripting language is the
// `affectation'. The following command defines a new variable `lc':
// lc va etre la longueur caractéristique dans tout le maillage
lc = 0.1;
a = 0.5; b = 1.76776695296637;
// a = 0.5; b = 1.25;
//a = 0.3125; b = 1.39754248593736;
// a = 1.0; b = 2.5;
c = 0.5;
d = 0.5;
Point(1) = {0.0, b, 0.0, lc};
Point(2) = {a, 0.0, 0.0, 0.8*lc} ;
Point(3) = {0.0, 0.0, 0.0, lc};
Point(4) = {a+c, 0, 0.0, 0.8*lc};
Point(5) = {a+c, b+d, 0.0, lc} ;
Point(6) = {0, b+d, 0.0, lc} ;
Line(1) = {2,4} ;
Line(2) = {4,5} ;
Line(3) = {6,5} ;
Line(4) = {1,6} ;
Ellipse(5) = {1,3,2,2};
Line Loop(1) = {1,2,-3,-4,5} ;
e0[] = Symmetry{0.0,1.0,0.0,0.0}{ Duplicata{ Line{5}; } };
e1[] = Symmetry{0.0,1.0,0.0,0.0}{ Duplicata{ Line{2}; Line{3}; } };
Physical Line(1) = {5,e0[0]};
Physical Line(3) = {2,3,e1[0],e1[1]};
Plane Surface(1) = {1} ;
s0[] = Symmetry{0.0,1.0,0.0,0.0}{ Duplicata{ Surface{1}; } };
Physical Surface(1) = {1,s0[0]};
n1 = 20;
n2 = 10;
n3 = 40;
Transfinite Line {3, 1, 8} = n1;
Transfinite Line {4, 13} = n2;
Transfinite Line {5, 6} = n3;
Transfinite Line {2, 7} = n2 + n3 - 1;
Transfinite Surface {1} = {2, 4, 5, 6};
Transfinite Surface {s0[0]} = {12, 9, 4, 2};
Mesh.Smoothing = 10;
Recombine Surface {1,s0[0]};
aa[] = Extrude {0, 0, 1} { Surface{9, 1}; Layers{5}; Recombine; };
Extrude{ {0, 0, 1} , {0,0,1} , {0.5,-1,0} , Pi/8 } { Surface{aa[0]}; Layers{5};
Recombine; }
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