# Epsilon Boundary condition

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 February 3, 2014, 11:05 Epsilon Boundary condition #1 Member   Manan Join Date: Oct 2013 Location: Göteborg Posts: 37 Rep Power: 5 Hello I am trying to validate a new turbulence model (zeta f) and am solving for epsilon amongst the other variables. The epsilon equation that will be used is the one used in standard k-epsilon model. I want to make use of the formulation, epsilon @Y=0 is specified as 2*nu* sqr(d/dy(k^0.5)). (Turbulence models for Near Wall and Low Reynolds Number Flows: A Review, Patel et. al 1985) I don't understand though how I should specify this in OF? Epsilon @ the wall i.e. at Y=0, is a derivative of k, that is: it is using the value of k @wall and the the value of k @the first node. How do I instruct the solver to use these two values? Please let me know if I haven't made myself clear. Thanks.

 February 3, 2014, 11:43 #2 Senior Member   Bernhard Join Date: Sep 2009 Location: Delft Posts: 790 Rep Power: 14 Are you aware that the zeta-f0 model was already implemented in OpenFOAM by Mirza Popovac? See: http://openfoamwiki.net/index.php/Si...bulence_models Also, if you use the epsilon equation from the standard k-epsilon, you don't include any Low-Re modifications, which you would need. Maybe you want to start from the To answer your question: your best change is to start from the epsilonWallFunction, see how the loop over the faces is done and access of the field data, and adjust to your needs

 February 11, 2014, 07:48 #3 Member   Manan Join Date: Oct 2013 Location: Göteborg Posts: 37 Rep Power: 5 Hi Bernhard Thanks so much for your reply. I wasn't aware of the existence of the zeta-f formulation and had written my own code. Fortunately I have Popovac's code to compare it with now. Also, the tip about modifying the epsilonWallFunction is helpful. It did serve my need.

 February 11, 2014, 07:50 #4 Member   Manan Join Date: Oct 2013 Location: Göteborg Posts: 37 Rep Power: 5 One question though, when I try compiling Popovac's formulation of zeta-f, using wmake libso, I get the following error message: /chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/MakefileOptions:37: /chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/rules/linux64Gcc47/general: No such file or directory make: *** No rule to make target `/chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/rules/linux64Gcc47/general'. Stop. /chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/MakefileFiles:39: /chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/rules/linux64Gcc47/general: No such file or directory /chalmers/sw/unsup64/OpenFOAM/OpenFOAM-1.6-ext/wmake/MakefileFiles:40: linux64Gcc47DPOpt/options: No such file or directory make: *** No rule to make target `linux64Gcc47DPOpt/options'. Stop. wmake error: file 'Make/linux64Gcc47DPOpt/objectFiles' could not be created I figured out that there are only a few compilers available in the OF-1.6-ext folder (Gcc45, Gcc46) but not Gcc47. Is there any way to direct \$WM_COMPILER to seek Gcc46 (which is available), instead of adding the folder for Gcc 47 in the OF1.6-ext wmake folder explicitly?

 February 11, 2014, 08:12 #5 Member   Manan Join Date: Oct 2013 Location: Göteborg Posts: 37 Rep Power: 5 Figured it out. It was as simple as saying: export WM_COMPILER = Gcc46 Thanks!

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