[syavash]

Hi,

How can I incorporate SGS stress tensor in solver pimpleFoam?!

I have constructed "B" in createField.H as follows:

volSymmTensorField B
(
    IOobject
    (
        "B",
        runTime.timeName(),
        mesh,
        IOobject::NO_READ,
        IOobject::AUTO_WRITE
    ),
    mesh,
           dimensionedSymmTensor
      (
           "B", 
           dimPressure,
           symmTensor::zero
      )
);

In pimpleFoam.c, under turbulence->correct(); in the main time loop, I have added:

B = turbulence->B();

when I compile the code, I get the following error:

MypimpleFoam.C: In function ‘int main(int, char**)’:
MypimpleFoam.C:90:32: error: ‘class Foam::incompressible::turbulenceModel’ has no member named ‘B’
                B = turbulence->B();

I have checked calss turbulenceModel and B is not defined there.

I think B is defined in LESModel.H but when I try to include this file I get compilation errors, indicating that the file cannot be found.

Please help me to solve this problem.

Thanks,
Syavash

PS: I am using OF version 2.3.1

[beatlejuice]

Dear syavash,

could you please tell me what the SGS stress tensor B is ... or how it is defined?

This would help me a lot since I have to deal with it when using WALE LES model.

Thank you very much in advance!

cheers

[syavash]

Originally Posted by beatlejuice

Dear syavash,

could you please tell me what the SGS stress tensor B is ... or how it is defined?

This would help me a lot since I have to deal with it when using WALE LES model.

Thank you very much in advance!

cheers

Hi,

It is the sub-grid scale stress tensor usually defined in literature by tau_ij. It is often placed in the right hand side of momentum equation, undergoing divergence operator. I am sure you will find it in the common turbulence text books such as Pope or Sagaut.

Best regards,
Syavash

[beatlejuice]

Ahh I see ... the term "B" has unsettled me.

Thank you very much syavash for your fast response!

[kagen816]

Originally Posted by syavash

Hi,

It is the sub-grid scale stress tensor usually defined in literature by tau_ij. It is often placed in the right hand side of momentum equation, undergoing divergence operator. I am sure you will find it in the common turbulence text books such as Pope or Sagaut.

Best regards,
Syavash

Hi Syavash,

I saw the B in GenSGSstress but it does not say how to get this value. The subgrid model can get the Vsgs but how to get B. What's more, in the codes devReff() seems to be Subgrid stress and B is tau_kk? I am very confused.

[manafaero]

dear sir

do you find an answer that how B and Reff is related in LES. Please help

[syavash]

Originally Posted by kagen816

Hi Syavash,

I saw the B in GenSGSstress but it does not say how to get this value. The subgrid model can get the Vsgs but how to get B. What's more, in the codes devReff() seems to be Subgrid stress and B is tau_kk? I am very confused.

Hi kagen,

It might be a little late, but you can find more details in the LESpimpleFoam that I had previously shared out on github:

https://github.com/syavash20/TurbLab/tree/master/LESpimpleFoam

Best Regards,
Syavash

[manafaero]

Thankyou very much for your help sir

But can you tell me where exactly or how B is used to solve the equations. I can see Reff is used as a part of U equation but where is B used.

[syavash]

Originally Posted by manafaero

Thankyou very much for your help sir

But can you tell me where exactly or how B is used to solve the equations. I can see Reff is used as a part of U equation but where is B used.

B itself is an auxiliary quantity and is not included in primary momentum equations.

Best Regards,
Syavash

[manafaero]

sir,

As you know the smagorinsky constant Cs in OpenFOAM is defined as a function of Ce and Ck. But when i do the simulation for various combinations of Ck and Ce, that gives the same Cs, I am getting different results. So could you please tell me where else Ck and Ce is used other than in smagorinsky model. My problem is incompressible LES with standard smagorinsky model and vandriest delta.

Please help

Thanking you

[syavash]

Originally Posted by manafaero

sir,

As you know the smagorinsky constant Cs in OpenFOAM is defined as a function of Ce and Ck. But when i do the simulation for various combinations of Ck and Ce, that gives the same Cs, I am getting different results. So could you please tell me where else Ck and Ce is used other than in smagorinsky model. My problem is incompressible LES with standard smagorinsky model and vandriest delta.

Please help

Thanking you

Unfortunately I lack the experience of working with standard Smagorinsky model. However by looking at the source code I see that both ce and ck should be read from dictionary of LESproperties, something like the following should work:

SmagorinskyCoeffs
    {
      filter    simple;
      ck        0.094;
      ce        1.048;
    }

Best Regards,
Syavash

[manafaero]

dear sir

I think Ck is read from LESproperties and Ce is read from GenEddyvisc.C file. But i would like to know that if Ck and Ce is used anywhere else in incompressible LES with standard smagorinsky model when using a pisoFoam solver (openFOAM2.4x).