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-   -   Near wall treatment (k and epsilon) (http://www.cfd-online.com/Forums/fluent/108755-near-wall-treatment-k-epsilon.html)

sagnikmazumdar October 31, 2012 15:58

Near wall treatment (k and epsilon)
 
Hi, I want to set dk/dn = 0 and depsilon/dn = 0 at the walls in Fluent where 'k' = turbulent kinetic energy and 'epsilon' is the rate of dissipation of turbulent kinetic energy. I wonder if it can be done !

Thanks
Sagnik

cfd seeker November 1, 2012 02:55

Yes. it can be done with the help of UDF

Far November 1, 2012 03:57

Quote:

Originally Posted by sagnikmazumdar (Post 389561)
Hi, I want to set dk/dn = 0 and depsilon/dn = 0 at the walls in Fluent where 'k' = turbulent kinetic energy and 'epsilon' is the rate of dissipation of turbulent kinetic energy. I wonder if it can be done !

Thanks
Sagnik

What are the default boundary conditions in Fluent for these variables at wall? And why you want to set these boundary conditions?

sagnikmazumdar November 1, 2012 11:02

Hi cfd seeker, I understand there is a udf function called "DEFINE_WALL_FUNCTIONS". But that does not allow you to specify gradients of k and epsilon. Can you be a bit more specific about what UDF and whether you have seen anybody implementing it?

sagnikmazumdar November 1, 2012 11:44

Hi far,

The default boundary conditions can be viewed at:

http://hpce.iitm.ac.in/website//Manu...ug/node510.htm


For the test case that we are designing we want to see whether it is important to model the wall properly to get the global flow features right ?

Thanks
Sagnik


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