UDF Wall functions in Fluent

syler3321 · June 15, 2011, 16:45

Hi,
I was reading the manuals for Fluent's UDF and chanced upon the wall function. This is what it said. Your UDF will
need to compute the real value of the wall functions U+, dU+, and dY+ for laminar and
turbulent regions and return them to the solver.
My question is: what is dU+ and dY+?
Also are these the only things i have to worry about when defining my own wall functions? I think i might have to alter the shear stress as well dont i?
Please help.
Regards
Ralph

grayback87 · June 17, 2013, 05:34

I have the same problem, because I need to model de shear stress with a function like this one:

Tau = Cd*rho*U^2

How can I do this?
It should be very simple, however I don't know how.
Here is the example of fluent.
http://www.sharcnet.ca/Software/Flue...wall-functions

And here the definition of the wall function by Launder and Spalding.
http://ta.twi.tudelft.nl/isnas/isnas...al/node48.html

But with this information I am not able to do the wall function that I need.

¿Someone could help ?

m zahid · September 20, 2014, 13:37

hi,

anybody know the meaning of DUPLUS and D2PLUS. these terms are used in UDF wall function example and also why the equation of both terms are different,

thanks
zahid

June 15, 2011, 16:45	UDF Wall functions in Fluent	#1
syler3321 Member ralph Join Date: Jun 2010 Location: Calgary Alberta Posts: 38 Rep Power: 16	Hi, I was reading the manuals for Fluent's UDF and chanced upon the wall function. This is what it said. Your UDF will need to compute the real value of the wall functions U+, dU+, and dY+ for laminar and turbulent regions and return them to the solver. My question is: what is dU+ and dY+? Also are these the only things i have to worry about when defining my own wall functions? I think i might have to alter the shear stress as well dont i? Please help. Regards Ralph

September 20, 2014, 13:37	meaning of DUPLUS and D2PLUS	#3
m zahid Member Qureshi M Z I Join Date: Sep 2013 Posts: 81 Rep Power: 13	hi, anybody know the meaning of DUPLUS and D2PLUS. these terms are used in UDF wall function example and also why the equation of both terms are different, thanks zahid

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June 17, 2013, 05:34		#2
grayback87 New Member Join Date: Dec 2011 Location: Spain Posts: 25 Rep Power: 15	I have the same problem, because I need to model de shear stress with a function like this one: Tau = CdrhoU^2 How can I do this? It should be very simple, however I don't know how. Here is the example of fluent. http://www.sharcnet.ca/Software/Flue...wall-functions And here the definition of the wall function by Launder and Spalding. http://ta.twi.tudelft.nl/isnas/isnas...al/node48.html But with this information I am not able to do the wall function that I need. ¿Someone could help ?