[Gmsh] 3D Optimization - Curl plugin

Christophe Geuzaine cgeuzaine at ulg.ac.be
Sun Mar 23 13:18:12 CET 2014

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.


> 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
> De informatie opgenomen in dit bericht kan vertrouwelijk zijn en is uitsluitend bestemd voor de geadresseerde. Indien u dit bericht onterecht ontvangt, wordt u verzocht de inhoud niet te gebruiken en de afzender direct te informeren door het bericht te retourneren. Het Universitair Medisch Centrum Utrecht is een publiekrechtelijke rechtspersoon in de zin van de W.H.W. (Wet Hoger Onderwijs en Wetenschappelijk Onderzoek) en staat geregistreerd bij de Kamer van Koophandel voor Midden-Nederland onder nr. 30244197.
> Denk s.v.p aan het milieu voor u deze e-mail afdrukt.
> This message may contain confidential information and is intended exclusively for the addressee. If you receive this message unintentionally, please do not use the contents but notify the sender immediately by return e-mail. University Medical Center Utrecht is a legal person by public law and is registered at the Chamber of Commerce for Midden-Nederland under no. 30244197.
> Please consider the environment before printing this e-mail.
> _______________________________________________
> gmsh mailing list
> gmsh at geuz.org
> http://www.geuz.org/mailman/listinfo/gmsh

Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science