CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   Yplus values (http://www.cfd-online.com/Forums/cfx/26761-yplus-values.html)

Matteo December 4, 2008 06:03

Yplus values
 
Hi there! I'm simulating an application and I can't find the right model to validate it. It has been sperimentally tested giving a value. I'm trying different models(BSL,SST and so on), but I don't exactly know which Yplus values they need. Is there any one who could help me? I would need all the yplus needed by the models. Thanks!

pratik mehta December 4, 2008 12:33

Re: Yplus values
 
Hi,

All you need to follow is to which wall function you should use, depending on your grid resolution , you can decide that. I think SST model is good

i hope this helps

Glenn Horrocks December 4, 2008 18:54

Re: Yplus values
 
Hi,

epsilon based models should have y+>11 as they use wall functions. Models in this class are k-epsilon, and RSM models using an epsilon equation.

omega based models should have y+=1 or thereabouts as the integrate to the wall. Models in this class are k-omega and RSM models with an omega equation.

The SST model is a bit of a special case in that it transitions nicely from wall functions to integrating to the wall so you should be able to use any y+ and it should be OK - with all the normal provisos for turbulence modelling.

Regards, Glenn Horrocks

CycLone December 5, 2008 00:19

Re: Yplus values
 
See ANSYS CFX-Solver Modeling Guide > Turbulence and Near-Wall Modeling > Modeling Flow Near the Wall in the CFX documentation. The documentation is very good on this topic and goes in to great detail on what you need to do and why you need to do it.

-CycLone


All times are GMT -4. The time now is 09:08.