
[Sponsors] 
Confusion with magSqr in turbulence model kOmegaSST  OpenFOAM 2.2.x 

LinkBack  Thread Tools  Display Modes 
January 7, 2014, 09:01 
Confusion with magSqr in turbulence model kOmegaSST  OpenFOAM 2.2.x

#1 
Member
Join Date: Jul 2011
Posts: 50
Rep Power: 7 
For the incompressible RAS I would like to implement the komega 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 412413 the production G is defined as: Code:
const volScalarField S2(2*magSqr(symm(fvc::grad(U_)))); volScalarField G(GName(), nut_*S2); 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_)); Thanks in advance. Kind regards, Andreas Last edited by A_Pete; January 7, 2014 at 10:01. Reason: fvc:: missing in Eqn. 3 

January 7, 2014, 10:38 

#2 
Senior Member
Gerhard Holzinger
Join Date: Feb 2012
Location: Austria
Posts: 197
Rep Power: 17 
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. 

January 8, 2014, 02:27 

#3 
Member
Join Date: Jul 2011
Posts: 50
Rep Power: 7 
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! 

September 4, 2014, 04:36 

#4  
New Member
Join Date: Feb 2014
Posts: 1
Rep Power: 0 
Quote:
i would be interested on the whole "someMath" document Is there a chance i can get it? regards Michael 

September 18, 2014, 04:52 

#5 
Senior Member
Gerhard Holzinger
Join Date: Feb 2012
Location: Austria
Posts: 197
Rep Power: 17 
The whole document can be found here http://www.cfdonline.com/Forums/ope...openfoam.html


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
gammaReTheta turbulence model for predicting transitional flows  FelixL  OpenFOAM Programming & Development  114  July 6, 2016 07:10 
Implement an les turbulence model  pante  OpenFOAM Programming & Development  19  December 5, 2014 17:16 
Turbulent frequency equation for compressible kOmegaSST turbulence model  Bojan  OpenFOAM Programming & Development  1  September 6, 2013 06:45 
What model of turbulence choose to study an external aerodynamics case  raffale  OpenFOAM  0  August 23, 2012 05:45 
How can run MRFSimpleFoam with KOmegaSST turbulence model  waynezw0618  OpenFOAM Running, Solving & CFD  0  April 21, 2008 04:40 