[Gmsh] characteristic length; algorithms

[Christophe Geuzaine]

Constanze Bausch wrote:
> Christoph,
> 
>  
> 
> thanks for your reply. When I change the characteristic length factor 
> for example to 0.5, I do understand, that the mesh size is going to be a 
> half smaller.
> 
> But how comes off the first mesh size, which is used? How is 
> characteristic length defined?  
> 

When no characteristic length is given (e.g. with step files), Gmsh uses 
the size of the object divided by 10. Once you set at least one char. 
length (on a geometry point, using a background mesh, etc.), then this 
default is ignored.

>  
> 
> I’m doing some evaluation and describing of mesh generation tools for my 
> diploma thesis. Therefore I also describe meshing algorithms that are used.
> 
> In your tool “Delaunay” for surface meshing is still experimental, as 
> you say. I would like to know, which algorithm is meant by “MeshAdapt”. 
> Maybe you can recommend an article about it?

This algorithm implements an original surface meshing strategy based on 
the concept of local mesh modifications, which hasn't been published yet.
> 
> And I noticed that every new mesh has a different structure, even though 
> the same parameters are used. Is the reason based on an algorithm, which 
> creates new points by coincidence?

Yes, the algorithm is randomized.



> 
>  
> 
> Thank you very much for your effort!
> 
> Constanze
> 
>  
> 
>  
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine