wall functions for RAS models

Epf · April 7, 2010, 08:43

Hi everyone,

is there a way to turn off the wall functions for the turbulent quantities in OpenFOAM 1.6? I'm a bit confused about this. I know that the RAS-models should be used with wall functions. But i want to compare the result with and without them to see the difference. Together with refining of my mesh.

Thank you in advance, Eric

farbfilm · April 8, 2010, 04:48

Hi,

maybe you can use "calculated" instead of (for example) "nutWallFunction" in the nut-file of your 0-directory!
But I'm not sure...

farbfilm · April 8, 2010, 05:00

Hi,

I tested it in the pitzDaily-tutorial and it worked (but I didn't checked the results)!
I think you also have to change the boundary conditions for k and epsilon in 0-directory! I used zeroGradient instead of kqRWallFunction and epsilonWallFunction!

cboss · April 8, 2010, 12:14

Hi,

you can use several provided RANS turbulence models without (log-law) wall functions. At least on can use the k-omega and k-omega-SST models. There is also a modified k-epsilon model for that purpose, the launder sharma KE.

If you are using the k-omega-SST model, I can tell you my setup for low-Re wall-treatment.
For boundary conditions at the wall, k=0, mut=0, omega=omegaWallFunction.

Note, that there is a new omegaWallFunction (very nice!) for low-Re wall-treatment. Therefore have a look at this thread.
http://www.cfd-online.com/Forums/ope...megasst-2.html

April 7, 2010, 08:43	wall functions for RAS models	#1
Epf New Member Join Date: Mar 2010 Posts: 6 Rep Power: 16	Hi everyone, is there a way to turn off the wall functions for the turbulent quantities in OpenFOAM 1.6? I'm a bit confused about this. I know that the RAS-models should be used with wall functions. But i want to compare the result with and without them to see the difference. Together with refining of my mesh. Thank you in advance, Eric

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April 8, 2010, 04:48		#2
farbfilm Member Michael Join Date: Mar 2009 Posts: 48 Rep Power: 17	Hi, maybe you can use "calculated" instead of (for example) "nutWallFunction" in the nut-file of your 0-directory! But I'm not sure...

April 8, 2010, 05:00		#3
farbfilm Member Michael Join Date: Mar 2009 Posts: 48 Rep Power: 17	Hi, I tested it in the pitzDaily-tutorial and it worked (but I didn't checked the results)! I think you also have to change the boundary conditions for k and epsilon in 0-directory! I used zeroGradient instead of kqRWallFunction and epsilonWallFunction!

April 8, 2010, 12:14		#4
cboss New Member Join Date: Feb 2010 Posts: 24 Rep Power: 16	Hi, you can use several provided RANS turbulence models without (log-law) wall functions. At least on can use the k-omega and k-omega-SST models. There is also a modified k-epsilon model for that purpose, the launder sharma KE. If you are using the k-omega-SST model, I can tell you my setup for low-Re wall-treatment. For boundary conditions at the wall, k=0, mut=0, omega=omegaWallFunction. Note, that there is a new omegaWallFunction (very nice!) for low-Re wall-treatment. Therefore have a look at this thread. http://www.cfd-online.com/Forums/ope...megasst-2.html