[Gmsh] Cannot mesh this simple example

[Christophe Geuzaine]

Loïc Le Guyader wrote:
> Hi all,
> 
> I try to play with gmsh, and I start with this simple example:
> Point(1) = {16.0,0.0,0.0,1.0};
> Point(2) = {-16.0,0.0,0.0,1.0};
> Point(3) = {0.0,4.0,0.0,1.0};
> Point(4) = {0.0,-4.0,0.0,1.0};
> Point(5) = {0.0,0.0,0.0,1.0};
> Ellipse(1) = {2,5,1,3};
> Ellipse(2) = {1,5,2,3};
> Ellipse(3) = {1,5,2,4};
> Ellipse(4) = {2,5,1,4};
> Line Loop(5) = {2,-1,4,-3};
> Plane Surface(6) = {5};
> Extrude Surface {6, {0.0,0.0,0.008}};
> Surface Loop(29) = {28,15,-6,19,23,27};
> Volume(30) = {29};
> 
> But unfortunately, after a long time and consumming all the memory,
> gmsh crashe, filling at the same time his console with a lot of:
> unable to add point xxx (will try it later)
> 
> I think it's because my size are tricky (the ellipse is really thin),
> but I'm sorry, this is what I'm studying :-(
> 
> Hope someone can help.

You're right, it's due to the very thin region: Gmsh does not manage to 
build the initial mesh.

I will put this example in our bug directory. In the meantime you should 
probably just use an extruded mesh for such regions, e.g.:

Point(1) = {16.0,0.0,0.0,1.0};
Point(2) = {-16.0,0.0,0.0,1.0};
Point(3) = {0.0,4.0,0.0,1.0};
Point(4) = {0.0,-4.0,0.0,1.0};
Point(5) = {0.0,0.0,0.0,1.0};
Ellipse(1) = {2,5,1,3};
Ellipse(2) = {1,5,2,3};
Ellipse(3) = {1,5,2,4};
Ellipse(4) = {2,5,1,4};
Line Loop(5) = {-2,1,-4,3};
Plane Surface(6) = {5};
Extrude Surface {6, {0.0,0.0,0.008}}{Layers{1,1};};


Christophe

-- 
Christophe Geuzaine
Applied and Computational Mathematics, Caltech
geuzaine at acm.caltech.edu - http://geuz.org