[Gmsh] GMSH failure in meshing - Unable to recover mesh, etc.

[Christophe Geuzaine]

Hi Franz,

I can indeed reproduce the issue on Windows (the Mac and Linux versions work fine). We have seen problems like this (accuracy problems leading to meshing failure with large element size gradients) for a while on Windows, but have not yet found a fix. They might be related to the behavior of the robust geometrical predicates, but we haven't been able to pinpoint the issue.

Christophe


> On 12 May 2017, at 10:16, Bormann, F. <F.Bormann at tue.nl> wrote:
> 
> Hi,
> I run currently into problems when I want to mesh my model.
>  
> I have two large equally sized connected 2D domains of total size LxH. Due to my problem I need a high resolution at following points:
>  
> 1.       Small area around Joint line of both domains between a<=x<=L  with a>0
> 2.       Small circle around point at x=L and y=H/2
> 3.       Small area around line x=L and H/2-b<y<H/2+b, where b is small in comparison with H
>  
> For the refinements I use the Attractor and Threshold fields with a combined Field = Min. The minimum mesh size is 0.125 for refinement 2 and 0.25 for refinements 1 and 3.
>  
> I have run the meshing procedure with 5 variations. 4 of those failed. The only parameters I varied are the: Length, height, maximum element size and (for the successful simulation) as well the parameter a. The model size varies between 4000x1600 and 6000x2000. And the maximum element size between 50 and 100.
>  
> Depending on the different variations I get different failure modes.
> 1.       Warning: Skipping bad triangle; Error: Unable to recover an edge. – only one of the domains is meshed
> 2.       GMSH crashes
> 3.       For Meshing of both domains – Error: Identical points in triangulation; Error: Unable to recover an edge. Increasing Mesh.RandomFactor does not help
> 4.       Error: Unable to recover an edge. – only one of the domains is meshed
>  
> The .geo files are attached with the suffix corresponding to the failure mode. Suffix 5 corresponds to the working mesh generation.
>  
> Here I used GMSH version 2.12.0 and 3.0.1. The operating system is Windows 7, 64-bit.
>  
> What is the reason behind the failure and is there a way to remedy the problem? It would really help me a lot.
>  
> Thanks already in advance.
>  
> Cheers,
> Franz
>  
> <Bug_Meshing_4.geo><Bug_Meshing_1.geo><Bug_Meshing_2.geo><Bug_Meshing_3.geo><Bug_Meshing_5.geo>_______________________________________________
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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