[Gmsh] Question about mesh refinement with stating of characteristic lengths

[David Colignon]

Hi,

it doesn't work because a dummy point is not enough, the dummy point must be part of a dummy line, which must be part of a dummy surface.

Or you can have a look at:

http://www.geuz.org/pipermail/gmsh/2008/003141.html

Cheers,

Dave

-- 
David Colignon, Ph.D.
Collaborateur Logistique F.R.S.-FNRS (Equipements de Calcul Intensif)
ACE - Applied & Computational Electromagnetics
Institut Montefiore B28
Université de Liège
4000 Liège - BELGIQUE
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Moritz Nadler wrote:
> Hallo ,
> 
> 
> while creating my second mesh with gmesh I ran a problem:
> 
> I have created a mesh with
> gmsh -rand 1.e-8 lightmillPeriodic.geo -2
> and this .geo file:
> 
> //begin file
> highPr = 0.000015;
> midPr = 0.0002;
> lowPr = 0.0006;
> vLowPr = 0.001;
> 
> Point(1) = {0,0,0,highPr};
> Point(2) = {0.25E-2,0,0,midPr};
> Point(3) = {0.5E-2,0,0,highPr};
> Point(4) = {0.5E-2,0.025E-2,0,highPr};
> Point(5) = {0.75E-2,0.025E-2,0,midPr};
> Point(6) = {2.25E-2,0.025E-2,0,midPr};
> Point(7) = {2.5E-2,0.025E-2,0,highPr};
> Point(8) = {2.5E-2,0,0,highPr};
> Point(9) = {2.75E-2,0,0,midPr};
> Point(10) = {4E-2,0,0,lowPr};
> Point(11) = {9.5E-2,0,0,vLowPr};
> Point(13) = {0,9.525E-2,0,vLowPr};
> Point(14) = {0,4.025E-2,0,lowPr};
> Point(15) = {0,2.775E-2,0,midPr};
> Point(16) = {0,2.525E-2,0,highPr};
> Point(17) = {0,2.275E-2,0,midPr};
> Point(18) = {0,0.775E-2,0,midPr};
> Point(19) = {0,0.525E-2,0,highPr};
> Point(20) = {0,0.275E-2,0,midPr};
> Point(21) = {0,0.025E-2,0,highPr};
> 
> // dummy point to lower the mesh density in this area (does not work)
> Point(22) = {0.25E-2,0.275E-2,0,midPr};
> 
> Line(1) = {1,2};
> Line(2) = {2,3};
> Line(3) = {3,4};
> Line(4) = {4,5};
> Line(5) = {5,6};
> Line(6) = {6,7};
> Line(7) = {7,8};
> Line(8) = {8,9};
> Line(9) = {9,10};
> Line(10) = {10,11};
> //Line(11) = {11,12};
> //Line(12) = {12,13};
> Circle(11) = {11,1,13};
> Line(13) = {13,14};
> Line(14) = {14,15};
> Line(15) = {15,16};
> Line(16) = {16,17};
> Line(17) = {17,18};
> Line(18) = {18,19};
> Line(19) = {19,20};
> Line(20) = {20,21};
> Line(21) = {21,1};
> 
> Line Loop(22) = {1,2,3,4,5,6,7,8,9,10,11,13,14,15,16,17,18,19,20,21};
> Plane Surface(23) = {22};
> // end file
> 
> But as it is stated in the gmsh manual
> "The size of the mesh elements will
> then be computed by linearly interpolating these characteristic lengths on the 
> initial
> mesh (see Section 1.2 [Mesh], page 3). This might sometimes lead to over-refinement
> in some areas"
> 
> it did lead to some over-refinement in areas where I do not need a high mesh density
> 
> so I wanted to:
> "so that you may have to add “dummy” geometrical entities in the model
> in order to get the desired element sizes."
> 
> so I added a first dummy point (the point with the comment in my .geo file) with 
> a lower ch. length to lower the mesh density in that area but the point is 
> totally ignored by the meshing routine; it is not even used as a node.
> 
> 
> I hope I could explain what I want to do my question then is of course:
> what to do to do it right?
> 
> 
> Thanks very much and
> 
> kind regards
> 
> 
> Moritz Nadler
> 
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