[Gmsh] Regular-triangle mesh generation problem

[Daniel Vieira Soares]

Hi David,

The .geo file has the following contents:

Point(1) = {0, 0, 0};
Point(2) = {4, 0, 0};
Point(3) = {0, 3, 0};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 1};
Line Loop(4) = {1, 2, 3};
Plane Surface(5) = {4};
Transfinite Line {1, 2, 3} = 2 Using Progression 1;
Transfinite Surface {5} = {1, 2, 3};

The process to achieve such meshes is:

1) Go to mesh menu
2) Click on "2D" once
3) Click on "Refine" 4 times
--> at this point, you have the regular mesh I want. But I don't know a way
to change the distribution of the nodes at the boundaries, like when using a
progression factor.
4) Click on "2D" again
--> now you have the mesh that gmsh usually creates, when defining 16
elements per boundary in the transfinite algorithm. Thy to change the line
"Transfinite Line {1, 2, 3} = 2 Using Progression 1;" to "Transfinite Line
{1, 2, 3} = 17 Using Progression 1;" and check the results with the 2D mesh.

In the end, all I want is to create a regular mesh where the elements are
defined like the first one, but starting from different distributions of the
boundary nodes.

Thanks for the quick answer.

Cheers,

Daniel

2009/2/13 David Colignon <David.Colignon at ulg.ac.be>

> Hi Daniel,
>
> can you send us the .geo file you used to produce triang02 ?
>
> Cheers,
>
> Dave
>
> --
> David Colignon, Ph.D.
> Collaborateur Logistique du F.R.S.-FNRS
> CÉCI - Consortium des Équipements de Calcul Intensif
> ACE - Applied & Computational Electromagnetics
> Sart-Tilman B28
> Université de Liège
> 4000 Liège - BELGIQUE
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>
>
>
> Daniel Vieira Soares wrote:
>
>> Hi,
>>
>> I am facing a problem when I try to create structured triangle meshes. I
>> want to produce a triangular mesh whose elements are defined by parallel
>> lines, or better, with lines that connect respective pairs from the boundary
>> - figure triang01.jpg attached shows that.
>>
>> When I create a transfinite triangular mesh with 16 elements (17 nodes)
>> per boundary, I usually get the elements of the mesh defined by baselines
>> that describe some sort of an arc around the first boundary point given to
>> the algorithm (shown in figure triang02.jpg attached is an example, when the
>> right angle node is the first point given to the transfinite surface
>> algorithm).
>>
>> The mesh in triang01.jpg is created by defining all transfinite lines with
>> 2 nodes, and then refining over and over. This obviously restrict my meshing
>> options (and isn't desirable), because this way I cannot define a
>> progression which the elements of some chosen boundary must obey.
>>
>> I don't really like the mesh created in the normal way (triang02.jpg)
>> because the elements around the "center" point (in this case, the right
>> angle node) are too narrow, or in another way, are too degenerated when
>> compared to other elements, and my simulation program is (too much) badly
>> affected by this.
>>
>> Can someone help me with this???
>>
>> Cheers,
>>
>> Daniel
>>
>> P.S. If there is any problem in accessing the images, I can put them
>> online in my webhost.
>>
>> ------------------------------------------------------------------------
>>
>>
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>>
>>
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>>
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>
>
>


-- 
Daniel Vieira Soares
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