Contour plot for quadratic elements

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mvscheven
Posts: 16
Joined: Thu Dec 04, 2014 4:26 pm
Location: Stuttgart, Germany

Contour plot for quadratic elements

Post by mvscheven »

Hello,

we are using quadratic elements to approximate curved structures and are quite surprised that the contour plot does not support quadratic elements (see picture).
Is there some way to get usable contour plots for quadratic elements?

Regards
Malte
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escolano
Posts: 1918
Joined: Sun Sep 05, 1982 10:51 pm

Re: Contour plot for quadratic elements

Post by escolano »

Quadratic elements could be shown:
a) Ignoring the quadratic nodes, taking into account only the first 'linear' corner nodes.+
b) Taking into account also the quadratic nodes, but then the elements are not drawn really quadric (curved), but only splitting the element into linear sub-elements (e.g. a quadratic square of 9 nodes is drawn as 8 linear triangles with the same nodes)

Draw the elements really curved could be very expensive, and GiD wants to handle millions of elements in real time.
For academic case it is usual to have few elements of big size, but for more industrial cases meshes require finer meshes to capture the physical behavior, and then an element drawn as linear or as quadratic is indistingishhable visually (use quadratic mesh is more important to capture the result that to approximate better a curved shape)

On the other hand Draw curved line-elements is not expensive, then there is an option to do it (like your image).

You can also draw quatratic line-elements linearized (a quadratic 3-noded element drawn splitting in 2 linear elements of 2 nodes), then at least surfaces and curves are drawn in the same way.
Utilities->Preferences... - Graphical - Appareance - Draw quadratic elements=As lines
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