Near wall treatment (k and epsilon)

sagnikmazumdar · October 31, 2012, 14:58

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, 01:55

Yes. it can be done with the help of UDF

Far · November 1, 2012, 02:57

Quote:

Originally Posted by sagnikmazumdar

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, 10:02

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, 10:44

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

October 31, 2012, 14:58	Near wall treatment (k and epsilon)	#1
sagnikmazumdar New Member Sagnik Join Date: Oct 2012 Posts: 28 Rep Power: 13	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

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November 1, 2012, 01:55		#2
cfd seeker Senior Member Join Date: Mar 2011 Location: Germany Posts: 552 Rep Power: 20	Yes. it can be done with the help of UDF

November 1, 2012, 10:02		#4
sagnikmazumdar New Member Sagnik Join Date: Oct 2012 Posts: 28 Rep Power: 13	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?

November 1, 2012, 10:44		#5
sagnikmazumdar New Member Sagnik Join Date: Oct 2012 Posts: 28 Rep Power: 13	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