[Gmsh] small gap mesh

[Christophe Geuzaine]

Christophe Geuzaine wrote:
> ZhouBin wrote:
>> Dear Christophe,
>>
>> Thank you very much for your patience. I have made one solution to my 
>> last problem: put fine mesh around the circles.
>>
>> However, as you could see from my latest version (.geo file), I have 
>> some circles which are close to the boundary, the mesh is so skewed.
>>
>> Since I  remember, Gmsh starts from line-->face-->volume, I really do to 
>> know how to deal with these circles. (I do not want to decrease the 
>> characteristic length for the whole domain, because of such close, small 
>> gap).
>>
>> Here I would like to send you my geo file, dear Christophe, if you have 
>> time, would you mind to take a look?
> 
> The problem lies in the accuracy of the 1D mesh algorithm. You can
> increase it with "Mesh.LcIntegrationPrecision=1.e-12;".
> 
> If this is too slow, you could also define attractors on the boundary.
> 

Or, cheaper, subdivide the long lines into smaller ones. For example,
you could replace the bottom of the rectangle with

p1 = 2;
For i In {10 : 349 : 5}
  p2 = newp;
  Point(p2) = {i, 0, 0};
  Line(newl) = {p1,p2};
  p1 = p2;
EndFor
Line(newl) = {p1,3};



>> Really appreciate your great advice.
>>
>> Best regards,
>>
>> Bin
>>
>>
>> ------------------------------------------------------------------------
>> From: zhoubinwx at hotmail.com
>> To: cgeuzaine at ulg.ac.be
>> CC: gmsh at geuz.org
>> Subject: RE: [Gmsh] aspect ratio error
>> Date: Sat, 15 Nov 2008 12:37:45 +0100
>>
>> Dear Christophe,
>>
>> I have a problem to control "aspect ratio".
>>
>> Here I attach the geo file, after generating the mesh using Gmsh, I use 
>> OpenFOAM to check the mesh, but I find that the aspect ratio is about 
>> 14. My professor suggests me to use aspect ratio =2.
>>
>> Could you please give me some hints about how to generate mesh with 
>> given aspect ratio?
>>
>> Best regards,
>>
>> bin
>>
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> 
> 


-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine