[Gmsh] Control mesh size through API

[Bin Wen]

I also have figured out that the unexpected small element size is somehow
the result of the large size of the domain I am trying to discretize. When
I try to mesh a 1x1 square, the mesh control works perfectly. However, when
I enlarge the square to 100x100, the mesh control does not perform
properly. I did set the characteristic length according to the domain size.
Not sure if there is any parameter that I should notice in order to correct
this size effect. Thanks

2014-12-11 10:00 GMT-06:00 Bin Wen <dracifer at gmail.com>:

> I have figured out how to control mesh using background fields through
> API. But have another question.
>
> I am trying to mesh a complex shaped polygon (many edges) using triangle
> elements. And I expect to have fine mesh close to the zigzag boundary but
> coarse mesh in the middle of the domain. I am using the background field to
> control the element size. All those methods in t10 (Attractor+Threshold,
> MathEval, Box) work well on the rectangle domain that I used for test.
> However, they do not give me expected results on the real shape. All
> methods generate very dense mesh through out the domain (the element size
> in the middle is a little bit larger than the boundary, but they are too
> small comparing with what I specified).
>
> One reason I could guess is that the boundary of the polygon is composed
> of a set of short segments. Therefore, they make the initial element small.
> But I suppose that should only make the elements near the boundary to be
> small. I expect the mesh in the middle of the domain to be very coarse. I
> have disabled CharacteristicLengthExtendFromBoundary option.
>
> I really appreciated if you could shed any light on this. Many thanks.
>
> Bin
>
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