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-   -   [ICEM] Growth ratio ICEM (http://www.cfd-online.com/Forums/ansys-meshing/112710-growth-ratio-icem.html)

krembil February 3, 2013 13:38

Growth ratio ICEM
 
Hello,

How can I set a "real" growth ratio of, for example 20% growth, for hexa mesh in ICEM?
If bigeometric bunching law is set, for a given initial height there is a range of number of elements that could be applied for the same growth ratio. In other words, there is no unique number of elements for a given growth ratio.

Thanks!

energy382 February 4, 2013 09:18

Quote:

Originally Posted by krembil (Post 405770)
Hello,

How can I set a "real" growth ratio of, for example 20% growth, for hexa mesh in ICEM?
If bigeometric bunching law is set, for a given initial height there is a range of number of elements that could be applied for the same growth ratio. In other words, there is no unique number of elements for a given growth ratio.

Thanks!

depends on mesh law and if you determine spacing 1 (let's say your intitial height) and spacing 2.

so if you choose bigeometric as mesh law and set your spacing 1 to 0.1 and ratio 1 to 1.2, the nodes will be distributed on this edge with these settings.

BUT: if you set a spacing 2 to a determinated value (other than 0), Icem will retain the initial spacing 1 and spacing 2 and grow ratio, but the max. space will change OR, if it isn't possible (to less or to many nodes), you have to change to number of nodes to achieve the intended grow ratio.

PSYMN February 4, 2013 17:54

Krembil,

Bunching gives you too many controls, and
Quote:

with great power comes great responsibility...
So, you could specify a small initial size and a small growth ratio, but not enough nodes to make it mathematically work out... In which case, it would just increase your ratio so it works...

Inversely, you could put too many nodes, in which case, the ratio could drop down to 1 (uniform) and your initial height could even be reduced.

You could also be setting things up on one edge and copy to another with a different overall length and end up with a different effective ratio.

This is why there are two columns in the Hexa Parameters panel... The first is what you would like... So you could put something like ratio = 1.1 in there. The second column is what you get... so if you don't have enough nodes, you could see that as ratio = 1.8...

To make the two line up, you can increase the number of nodes until you see something similar in the second column.

Do you get it? Play with it a bit and you will. :cool:

krembil February 5, 2013 03:32

Thank you for your answer.
It's clear now.

Marijo


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