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Confusion with magSqr in turbulence model kOmegaSST - OpenFOAM 2.2.x

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Old   January 7, 2014, 09:01
Default Confusion with magSqr in turbulence model kOmegaSST - OpenFOAM 2.2.x
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For the incompressible RAS I would like to implement the k-omega SST turbulence model by Menter with the vorticity source term. You can find the theory on it here: http://turbmodels.larc.nasa.gov/sst.html
So I had a look at the standard kOmegaSST turbulence model which is implemented into OpenFOAM. The only thing I have to change is the production of turbulent kinetic energy. In the kOmegaSST.C on lines 412-413 the production G is defined as:

Code:
const volScalarField S2(2*magSqr(symm(fvc::grad(U_))));
volScalarField G(GName(), nut_*S2);
Eqn. 1

But I can't really make the conversion to the standard formula that I know, which will look like this for incompressible RAS:

G=nut*dUi/dxj*(dUi/dxj+dUj/dxi)
Eqn. 2

So my question is why is there a magSqr in Eqn. 1? This looks different from the definition that I know.

Shouldn't it be more like this:
Code:
const volScalarField S(2*mag(symm(fvc::grad(U_))));
volScalarField G(GName(), nut_*S*fvc::grad(U_));
Eqn. 3


Thanks in advance.

Kind regards,
Andreas

Last edited by A_Pete; January 7, 2014 at 10:01. Reason: fvc:: missing in Eqn. 3
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Old   January 7, 2014, 10:38
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Hi,

take a look at the attached pdf. In Sect. 39.4.7 I do the math to look whether the formular for the production term for the turbulent kinetic energy of the kEpsilon model in OpenFOAM is equal to the formula stated in the book of Ferzinger.

The equations you posted look the same as they are in the question I answered.
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File Type: pdf someMath.pdf (96.2 KB, 91 views)
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Old   January 8, 2014, 02:27
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Hi Gerhard and thank you very much for your answer,

yes the equations of Ferziger, Perić is the same that I stated, as well as the implementation in OpenFOAM. This is the proof I was looking for!
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Old   September 4, 2014, 05:36
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Quote:
Originally Posted by GerhardHolzinger View Post
Hi,

take a look at the attached pdf. In Sect. 39.4.7 I do the math to look whether the formular for the production term for the turbulent kinetic energy of the kEpsilon model in OpenFOAM is equal to the formula stated in the book of Ferzinger.

The equations you posted look the same as they are in the question I answered.
Hi Gerhard,

i would be interested on the whole "someMath" document Is there a chance i can get it?

regards Michael
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Old   September 18, 2014, 05:52
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The whole document can be found here Humble Homegrown Knowledge Collection on OpenFOAM
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