# [Gmsh] Characteristic length

Jö Fahlke jorrit at jorrit.de
Mon Aug 20 22:58:32 CEST 2012

```Am Mon, 20. Aug 2012, 20:53:23 +0200 schrieb Christophe Geuzaine:
> On 20 Aug 2012, at 17:50, Andres Gonzalez Estrada <agestrada at gmail.com> wrote:
>
> > Does anyone have a clue about how gmsh interpret the characteristic lenght?. The problem has been described before in several post with no successful reply, e.g.:
> >
>
> Hi Jo - it's the length of mesh edges.

It wasn't me who asked the question this time -- but I'll join the discussion
anyway.

I'm assuming you mean the characteristic length is an upper limit for the edge
length.  But that can't be true, or at least there is something missing.  In
3D, if I remember correctly, the maximum edge length is usually something like
twice the characteristic length.

To illustrate, please find attached the simple example
unit-square.{geo,msh,pdf}.  The mesh was generated with gmsh 2.6.1.dfsg-3 from
Debian.  The unit square has a side length of 1, and I used a characteristic
length of 0.1 (by setting the characteristic length at the Points).  As you
can see, each side of the unit square is devided into 9 segments, which means
the size of at least one of the segments must be larger than the
characteristic length.

Regards,
Jö.

--
Jorrit (Jö) Fahlke, Interdisciplinary Center for Scientific Computing,
Heidelberg University, Im Neuenheimer Feld 368, D-69120 Heidelberg
Tel: +49 6221 54 8890 Fax: +49 6221 54 8884

[Zum Thema GNOME 3]
(15:11:22) marina: linus ist auf meiner seite
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Point(1) = {0, 0, 0, 0.1};
Extrude {1, 0, 0} {
Point{1};
}
Extrude {0, 1, 0} {
Line{1};
}
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