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-   -   [ICEM] Aspect ratio vs quality of a tetra mesh (https://www.cfd-online.com/Forums/ansys-meshing/106962-aspect-ratio-vs-quality-tetra-mesh.html)

 vmlxb6 September 13, 2012 09:17

Aspect ratio vs quality of a tetra mesh

Hello,

I have this geometry where I have used tetra meshing throughout. When I checked the histogram of quality values I found that majority of my elements are
between 0.45 to 1 how ever the histogram of aspect ratio looks different. My question is how is quality defined in ICEM.
The documentation says for a tetra element, the quality is calculated as the aspect ratio of the tetra element. So that means histogram of quality and aspect ratio should be the same. I would appreciate if someone could throw some light on this.
Also when can an individual tell that the tetra mesh is good enough. Is there a general criteria used ?

Thank you very much for all your help. appreciate.

 FVH September 17, 2012 08:28

Hi vmlxb6,

My question is almost the same and at the moment i'm trying to find out why the histogramm of aspect ratio is so different to the histogramm of quality. Do you know how quality is defined in Icem? What is the general criteria?
Thank you for your help

 vmlxb6 September 17, 2012 11:05

Hello FVH,

We both have the same question presently. Hopefully someone can answer to all our query.

-vmlxb6

 FVH September 18, 2012 05:35

Hi vmlxb6,

It is reallyy difficult to get an answer for this question but at least i found a little help in the icemhelp guide. On page 395 and the following you will find some definition. The criterion quality is calculated differently for each element type. For quad and hexa., the quality is calculated as the determinant. A determinant value of 1 would indicate a perfectly regular mesh element, 0 would indicate an element degenerate in one or more edges.

 BrolY September 25, 2012 09:51

It's because you check the quality for tetra, but also for tri or even penta (if you have some).
Go to Edit Mesh -> Display Mesh Quality ->
Select only the tetra, and check for quality and aspect ratio.
You will find the same histogram.

The aspect ratio is only calculated for tri and tetra.
But quality is also calculated for penta.

 vmlxb6 September 25, 2012 13:21

@ Broly

That was very helpful. Thank you very much.

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