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Old   February 3, 2014, 10:05
Default Epsilon Boundary condition
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Manan
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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.
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Old   February 3, 2014, 10:43
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Bernhard
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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
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Old   February 11, 2014, 06:48
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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.
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Old   February 11, 2014, 06:50
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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?
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Old   February 11, 2014, 07:12
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Figured it out. It was as simple as saying:

export WM_COMPILER = Gcc46

Thanks!
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