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-   -   ce and ck in ‘oneEqEddy’ (http://www.cfd-online.com/Forums/openfoam/122024-ce-ck-oneeqeddy.html)

zxj160 August 10, 2013 10:54

ce and ck in ‘oneEqEddy’
 
Dear foamers,

I want to modify the value of ce and ck in the LES model (i.e. oneEqEddy) and implement a new turbulent model. I found the declaration of ck_ and its value in the 'oneEqEddy.C'. But where can I find the declaration of ce?

My best regards,
Jian

cfdonline2mohsen August 11, 2013 17:10

Dear Jian
I remember that I changed the value of Cs in the standard smagorinsky model once to Cs=0.12 by using the relationship between Cs and ce and ck. (I can't remember now but you can find this relationship in turbulence books)
I remember that only one of the coefficients (ce or ck) were defined in the .c code (probably ck_ that is defined in the code) and the other coefficient (probably ce) were defined in one of the #.H that exists at the beginning of the code.
because Ce will be used by the other turbulence models; so changing its value will affect the other models.
so it is better to derive the new value for ck for your desired Cs by using the relationship between Cs and ce and ck and change cK in this code rather than changing Ce.

zxj160 August 13, 2013 07:37

Dear Kia,

I find a way to modified these value without changing the source code. But I am not sure whether it is right.

Just add the following lines in the 'LESProperties' file under the constant directory.

....

LESModel oneEqEddy;

delta cubeRootVol;

printCoeffs on;

cubeRootVolCoeffs
{
deltaCoeff 1;
}

oneEqEddyCoeffs
{
ck 0.08;
ce 1.05;
}

....


My best regards,
Jian

cfdonline2mohsen August 13, 2013 08:49

Thanks Jian
I did not notice that!!
that was tricky:):):)
at the beginning of the run; OpenFOAM writes the solver that you use and the turbulence models coefficients at your computer's screen.
does it print this new values of ce and ck that is specified in oneEqEddyCoeffs?

zxj160 August 13, 2013 08:53

Dear Kia,

Yes, I think so. The new values are outputted at the beginning of the run. So I guess it should work properly.

My best regards,
Jian


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