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-   -   Face handedness problem appears (http://www.cfd-online.com/Forums/fluent/36463-face-handedness-problem-appears.html)

michael April 22, 2005 09:08

Face handedness problem appears
 
Hi guys,

What can be a reason of left handedness faces existance in transient(sliding meshes) calculation? The problem didn't exist on the beginning. When I read the msh file everything was ok. Now when I check the grid, the warning appears (left hendedness faces). I have checked saved cas and dat files and some of them can be repaired and some of them not. How to avoid such problem?

zxaar April 22, 2005 09:15

Re: Face handedness problem appears
 
this is a bug with fluent , whether some people agree on this or not, i took up this issue with fluent asia pacific and the advice they gave me is that between the sliding interface keep a very little space, i don't know how much space they want me to keep , i never tried this way.

for my cases to avoid this problem, i usually mesh the slidign interfaces as same distribution (all the nodes fall on respective nodes) then when i define interface between them i never get this message (so if u can afford to make such mesh try this this always works),

otherwise the handedness problem appears just after the definition of interface

michael April 22, 2005 09:48

Re: Face handedness problem appears
 
Thanks for your really fast response Zxaar. It is very helpful for me.

best regards


ej April 22, 2005 12:22

Re: Face handedness problem appears
 
This has been a long standing problem with sliding mesh.

You can try reversing the order that you choose the interface pairs. I believe Fluent recommends choosing the interface with the smaller cells first. They have also told me that how you build the geometry can have an effect...starting from a circular volume as opposed to sweeping an arc, making a face etc. Never really believed that one.

The best way to prevent it is to have the mating interface meshes have very similar face sizes and of low slewness. Both important for accuracy anyway.


galeazzo April 25, 2005 12:33

Re: Face handedness problem appears
 
Hi,

You can try a Fluent built-in command to repair the face handedness... but it doesn´t work always:

grid > modify-zones > repair-face-handedness

Rajesh G May 13, 2005 21:32

Re: Face handedness problem appears
 
When I use the repair command, my grid checking is found fine. But when I start calculation its shows the message of negative volumes. I think there are no negative volumes before I repair the face handedness. Could you please help me to fix this problem?


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