# simpleFoam with Launder-Sharma Model

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 March 1, 2010, 11:53 simpleFoam with Launder-Sharma Model #1 New Member   June Join Date: Dec 2009 Posts: 18 Rep Power: 9 Sponsored Links Hello everyone, I'm a new user with openfoam. Now i want to use simpleFoam with Launder-Sharma Low-Re Model. There's only one time step calculated. Then a erro as below is displayed. // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 Reading field p Reading field U Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting RAS turbulence model LaunderSharmaKE LaunderSharmaKECoeffs { Cmu 0.09; C1 1.44; C2 1.92; sigmaEps 1.3; } Starting time loop Time = 0.1 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0606568, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.995352, Final residual = 0.0222388, No Iterations 1 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.00735996, No Iterations 6 DICPCG: Solving for p, Initial residual = 0.00365507, Final residual = 3.33199e-05, No Iterations 63 DICPCG: Solving for p, Initial residual = 2.37913e-05, Final residual = 8.92903e-07, No Iterations 30 time step continuity errors : sum local = 4.57548e-05, global = -4.42317e-06, cumulative = -4.42317e-06 #0 Foam::error:rintStack(Foam::Ostream&) in "/usr/local/OpenFOAM/1.6/lib/linux64GccDPOpt/libOpenFOAM.so" #1 Foam::sigFpe::sigFpeHandler(int) in "/usr/local/OpenFOAM/1.6/lib/linux64GccDPOpt/libOpenFOAM.so" #2 __restore_rt at sigaction.c:0 #3 Foam::divide(Foam::Field&, Foam::UList const&, Foam::UList const&) in "/usr/local/OpenFOAM/1.6/lib/li #4 void Foam::divide(Foam::GeometricField&, Foam::sh> const&, Foam::GeometricField const&) in "/usr/local/OpenFOAM/1.6/lib/linux64GccDPO #5 Foam::tmp > Foam:perator/ > const&, Foam::GeometricField const&) in "/usr/local/OpenFOAM/1 #6 Foam::incompressible::RASModels::LaunderSharmaKE:: correct() in "/usr/local/OpenFOAM/1.6/lib/linux64GccDPOpt/libincompressible #7 main in "/usr/local/OpenFOAM/1.6/applications/bin/linux64GccDPOpt/simpleFoam" #8 __libc_start_main in "/lib64/libc.so.6" #9 _start at /usr/src/packages/BUILD/glibc-2.9/csu/../sysdeps/x86_64/elf/start.S:116 Floating exception I cann't get any useful information from the erro. The p, U, k, nut, epsilon are gaven as boundary condition. My question is, can simpleFoam be used with LS Model or did I do something wrong?

 March 2, 2010, 04:07 #2 Member   Join Date: Apr 2009 Location: Karlsruhe, Germany Posts: 96 Rep Power: 10 Hi, simpleFoam is able to use LaunderSharma, look at following posting: http://www.cfd-online.com/Forums/ope...us-values.html You must be careful with your inlet bc's for k and epsilon. Regards Thomas

 March 2, 2010, 08:23 #3 New Member   June Join Date: Dec 2009 Posts: 18 Rep Power: 9 Hi Thomas, Thanks for the reply. why cannot i set the k and epsilon not equal 0 for the boundary condition at wall? That was the problem of me. Regards Yang Last edited by examosty; March 2, 2010 at 12:07.

 March 3, 2010, 03:35 #4 Member   Join Date: Apr 2009 Location: Karlsruhe, Germany Posts: 96 Rep Power: 10 I think you are not allowed to divide through zero.

March 3, 2010, 03:47
#5
Member

Primoz Ternik
Join Date: Apr 2009
Location: Maribor, Slovenia
Posts: 65
Rep Power: 10
Quote:
 Originally Posted by examosty Hi Thomas, Thanks for the reply. why cannot i set the k and epsilon not equal 0 for the boundary condition at wall? That was the problem of me. Regards Yang
Hi Examosty,

why would you set non-zero values at solid walls for k and epsilon? Launder-Sharma turbulence model is so called "low reynolds number" closure ad its damping function, values of constants, etc. are derived on the basis of zero values for k and epsilon (at solid walls)!

I really suggest that you grab your hands on the following book David C. Wilcox, Turbulence Modelling For CFD

Cheers,
Primoz

March 3, 2010, 07:16
#6
New Member

June
Join Date: Dec 2009
Posts: 18
Rep Power: 9
Quote:
 Originally Posted by ternik Hi Examosty, why would you set non-zero values at solid walls for k and epsilon? Launder-Sharma turbulence model is so called "low reynolds number" closure ad its damping function, values of constants, etc. are derived on the basis of zero values for k and epsilon (at solid walls)! I really suggest that you grab your hands on the following book David C. Wilcox, Turbulence Modelling For CFD Cheers, Primoz
Hi Primoz,
that's what i thought and what i did, set k and epsilon at solid wall equal 0. Then the error as i've replayed in the beginning occurred. As Thomas said, it's a problem of dividing through zero.
Regards,
June

March 3, 2010, 08:01
#7
Member

Primoz Ternik
Join Date: Apr 2009
Location: Maribor, Slovenia
Posts: 65
Rep Power: 10
Quote:
 Originally Posted by examosty Hi Primoz, that's what i thought and what i did, set k and epsilon at solid wall equal 0. Then the error as i've replayed in the beginning occurred. As Thomas said, it's a problem of dividing through zero. Regards, June
now I am getting the point! I do not know exactly how the Launder-Shrama is incorporated in OpenFoam, but "the general" theory for solid wall behaviour is (at lest I think so):
• since there are no velocity fluctuations in a near wall region (viscous forces are predominant) the turbulence kinetic energy is 0 at solid wall
• for dissipation of turbulence kinetic energy "low Re" closures solves "modified" equation for epsilon
epsilon_mod=epsilon-D
• so actually, you are prescribing boundary conditions for "modified epsilon", which is zero at solid wall
Hope this helps,
Primoz

May 30, 2015, 11:34
#8
New Member

Ricardo Ferreira
Join Date: May 2015
Posts: 15
Rep Power: 4
Hello Foamers!
I'm a new user in OpenFoam. I appreciate your helps and tips and I'm gratefull for that. My problem is incompressible flow through radial diffuser with low Reynolds number. I want to use LaunderSharmaKE turb. model without wall functions.

1) I deleted nut file and k and epsilon files were setted with fixedValue for wall boundary conditions. The k and epsilon values on the wall I fixed with zero and close to zero (1e-10). In these two situations floting point exception ocurred.

2) Can someone check my attachement files to find out if I made a mistake?

3) I don't understand what "value" below Intensity really does mean. The value of turb. kinetic energy (k) will be calculated based on turb. intensity, so why set this value? Please, can someone clear it me?

inlet
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.03;
value uniform 0.3;
}

Thanks!
Attached Files
 LaunderSharmaKE.zip (26.7 KB, 40 views)

Last edited by RLFerreira; June 1, 2015 at 20:21.

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