[Gmsh] 3D Optimization - Curl plugin

[Christophe Geuzaine]

On 21 Mar 2014, at 08:53, Mandija, S. <S.Mandija at umcutrecht.nl> wrote:

> Dear all GMSH users,
> 
> I am writing you because I have found an issue running the CURL plugin.
> In order to show you the problem I discovered, I have enclosed a picture in the email. 
> I noticed that if I don't optimize a 3D mesh (left column in the picture) I have almost the same calculated field for each node as if I optimize the mesh (right column in the picture). The calculated field is just a mathematical combination of the geometrical position of the points (for example, for one point the X component of the field is the sum of the geometrical position on the Y and Z axis of that point).
> Then, if I do the CURL of the field calculated on each node I have a corrected shape if the mesh was previously optimized (right part in the figure). If the mesh was instead not optimized (left part in the picture) I have some spikes that compromise the result although the other arrows are correctly oriented.
> 
> At this point I was wondering if there is a problem on the curl plugin or if I should always optimize a mesh using optimize3D and Netgen optimization in order to have reliable results while running nabla operations.
> If it is so, why optimization is so important before running nabla operations like the curl?
> 

Hi Stefano - Without optimization, the mesh can contain bad quality elements (e.g. almost flat tetrahedra). This leads to bad accuracy when computing the curl. You can check the quality of the mesh with Tools->Statistics.

Christophe


> I thank you for your time in advance.
> 
> Best regards,
> Stefano
> 
> 
>      
> Stefano Mandija M.Sc.|PhD Student|Imaging Division|University Medical Center Utrecht
> Heidelberglaan 100|3584 CX Utrecht|The Netherlands|Visiting address: Q04.4.302|Tel.: +31 88 7569649
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine