[Gmsh] Mesh error

[Sabrina Zacarias]

You’re absolutely right, thank you. I’d like to make a follow up question, if I may (hopefully not as stupid as the previous one): 

In my model I merge several volumes using BooleanUnion. The difficulty is that after this command, the tags of the surfaces are lost. (And  I need them to define physical surfaces). Is there a workaround or a way of forcing the tags to not change? 

What I would like in the end is to have a physical surface which is the group of all surfaces in the same plane. Is there maybe a smarter way or a built-in command in which I can achieve this without needing to make a list the list of all the surfaces by hand?

Thank you so much for your support,

Sabrina
-- 
Sabrina Zacarias
Institut für Kernphysik
Technische Universität Darmstadt
S2|14 / office 319
Schlossgartenstr. 9

64289 Darmstadt

Office: +49 6151 16 23589

> On 29. Mar 2020, at 22:28, Christophe Geuzaine <cgeuzaine at uliege.be> wrote:
> 
> 
> 
>> On 29 Mar 2020, at 12:24, Sabrina Zacarias <szacarias at ikp.tu-darmstadt.de <mailto:szacarias at ikp.tu-darmstadt.de>> wrote:
>> 
>> Dear all,
>> 
>> I am a bit confused with the output of the meshing of my model and would really appreciate a piece of advise:
>> 
>> My geometry consists of an axial section of a cylinder (which plays the role of the air surrounding my model ) containing several (sections of) rings, which are electrodes, plus two (sections of ) disks, which are the cathode and anode. The fact that these are sections and not complete cylindrical pieces is to make the meshing faster. And the post processing software can handle it.
>> 
>> Anyway, In the real model  I need to use ~200 electrodes.  So far I have not been able to achieve a mesh without errors. I get ‘Unable to recover the edge XX on curve XX (on surface XX )’, and also   ’No elements in volume XX’. 
>> 
> 
> With Nel = 200 your geometry is invalid (it auto-intersects), whereas with Nel = 20 it is correct.
> 
> Christophe
> <intersect.png>
> 
>> What I find confusing is that when I reduce the number of electrodes x10 lower, without changing anything else, the meshing is correct. 
>> 
>> I am obviously missing something or not approaching the problem the right way. I attach the .geo files if someone could please take a look. 
>> 
>> Best regards,
>> 
>> Sabrina
>> 
>> <3d_main.geo>
>> <f_box.geo>
>> <f_electrode.geo>
>> <f_plates.geo>
>> 
>> — 
>> Sabrina Zacarias
>> Institut für Kernphysik
>> Technische Universität Darmstadt
>> S2|14 / office 319
>> Schlossgartenstr. 9
>> 
>> 64289 Darmstadt
>> 
>> Office: +49 6151 16 23589
>> 
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> 
> — 
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science 
> http://www.montefiore.ulg.ac.be/~geuzaine <http://www.montefiore.ulg.ac.be/~geuzaine>
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