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-   -   wall function and grid independency????? (http://www.cfd-online.com/Forums/fluent/42641-wall-function-grid-independency.html)

scott October 22, 2006 07:42

wall function and grid independency?????
 
I am new ,very new I have question about turbulence modeling and mesh independency.

I am using k-epsilon and wall functions to resolve the flow. Now I have to optimize the mesh for my case. 1-when the wall function is valide? i read the manual and i I didn't understand: i follow y+ or y star

2-How can I attin the grid independency ? 3- y+ satisfated imply that i have an independent mesh est regards


Ralf Schmidt October 23, 2006 08:47

Re: wall function and grid independency?????
 
http://www.cfd-online.com/Forum/flue...cgi?read=42778

scott October 23, 2006 17:25

Re: wall function and grid independency?????
 
i read the help but i haven't understand

hugo October 26, 2006 12:31

Re: wall function and grid independency?????
 
When the wall function is valide?,

When the normal stresses are negligible. for example in straight ducts.

In curve ducts like a 90 degrees bend, the normal stresses are important and the wall function is not correct.

if you use wall function you need to check the Y plus and in this case the Y plus must be close 20 or 30

if you don't use wall function Y plus must be close 1



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