[Gmsh] 2D refinement around a line

Geordie McBain gdmcbain at freeshell.org
Thu Mar 10 23:47:08 CET 2011


2011/3/11 GERALD sophie DSNA/CC <sophie.gerald at onera.fr>:
> Good evening,
>
> I work with the "gmsh-2.5.0-Linux" version of your software. By the way,
> congratulations for what you are doing!
>
> I am tring to construct a mesh around an object. It is a 2D unstructured
> mesh. The file .geo is in attachement and works well.
> First question: Because I impose a number of points on the object, is the
> caracteristic mesh size "poids1" working anymore? I mean is the transfinite
> command interacting with the caracteristic mesh size command or is it
> erasing it?
>
> Now I would like to make a refinement around line number 104 (x~=0.6).  See:
> Line(104).
> I can not find the best way to do it. I have tried:
> i- "transfinite command" but "the software" doesn't take care of what is
> writting. See: Transfinite Line (104)
> ii- "attractor command" but on the "forum on internet" you say that it is
> not complety operational.
> iii- To redefine a surface. See: Plane Surface(1001). That is to say I try
> to refine between x=[0.5,0.7]. But with this way I have two meshes and no
> continuity between the interfaces issued from the first mesh and the second
> one (I mean I don't want to split my interfaces from the first mesh in two
> lines at the connection surfaces!).
> Thus second question is : How is the best way to do what I want: to make a
> refinement around line number 104?

Does the attached Object.geo do what you want?

In modifying Obeject_GERALD.geo, I broke up the spline along the
extrados and made the lines emanating from Point 201 have feet at
points of the spline, then the two triangles adjoining the attractor,
Line 104, were made Plane Surfaces, and finally the rest of the domain
excluding these two surfaces, was made into a third Plane Surface.

I too remember reading a disclaimer about Attractor, can't remember
where, but I've found it to work well in these situations.  See also
http://www.geuz.org/pipermail/gmsh/2011/006166.html. I didn't use
Transfinite here.
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