[Gmsh] RE (second) wrong maximum-values in a contour plot coming from a .med-results-file

[Christophe Geuzaine]

On 07 Feb 2014, at 19:45, Johannes Ackva <johannes.ackva at code-aster.de> wrote:

> Hello Jean-Pierre and Christophe,
> 
> Jean-Pierre, yes Your Plot shows as max the maximum nodal value. And I
> verified now that this can be shown be using the "Adapt visualisation
> grid".
> 
> Christophe,
> thank You for Your background information. Let me please pose a next
> question: How can it be judged which is the true max value? And what
> does it mean if the max-values from different approximations are so
> different (194 vs 240): Mesh not fine enough? Or elm quality bad? Or both?
> 

It's not a problem: it's just that the maximum of a second order polynomial interpolated with Lagrange functions is not necessarily at one of the interpolation nodes. Consider a second order line element [0,1] with a middle node at 0.5. Assign values 1, 2 and 2 at the 3 nodes. The maximum is not 2 - but 2.125 (between the middle and the right node).

+----+-----+
0    0.5   1


> thank for very much, Best regards, Johannes_ACKVA
> 
> 
> www.code-aster.de
> 
> On 07/02/14 17:12, jean pierre aubry wrote:
>> with quadratic element
>> is not it that? 
>> enclosed pic
>> 
>> Adapt visualization grid
> <Screenshot.png><bado_segment45_post.resu>_______________________________________________
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine