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Subgrid Viscosity - modifying Smagorinsky

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Old   January 27, 2022, 20:41
Thumbs up Subgrid Viscosity - modifying Smagorinsky
  #1
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Carl Dahmen
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Hello Foamer!

I am working with CFDEM, but my question is OpenFOAM related.
My aim is to modify the Smagorinsky turbulence model and implement a viscosity that depends on the local voidfraction according to Batchelor and Green (1972) as: nu_t = nu*(a*(1-voidfraction)+b*(1-voidfraction)^2)

Since my OpenFOAM knowledge is lacking, have I tried to follow the Smagorinsky model as closely as I can and followed guides to implement a new turbelence model. But my problem comes down to accessing the voidfraction, I assume this can be done by using IOobject but I do not know how.

Here is my code (Protected Member Functions):

Code:
template<class BasicTurbulenceModel>
tmp<volScalarField> BatchelorGreen<BasicTurbulenceModel>::k
(
    const tmp<volScalarField>& voidfrac
) const
{
    volScalarField solidfrac(scalar(1)-voidfrac);

    volScalarField c1(nu_*a_*solidfrac);
    volScalarField c2(nu_*b_*sqr(solidfrac));

    return tmp<volScalarField>
    (
        new volScalarField
        (
            IOobject
            (
                IOobject::groupName("k", this->U_.group()),
                this->runTime_.timeName(),
                this->mesh_
            ),
            c1+c2
        )
    );
}

template<class BasicTurbulenceModel>
void BatchelorGreen<BasicTurbulenceModel>::correctNut()
{
    new volScalarField
    (
	IOobject
	(
	    IOobject::groupName("voidfraction", this->U_.group()),
	    this->runTime_.timeName(),
	    this->mesh_,
	    IOobject::MUST_READ,
	    IOobject::NO_WRITE
	)
    )
	
    volScalarField k(this->k(this->voidfraction_)); 

    this->nut_ = k;
    fv::options::New(this->mesh_).correct(this->nut_);

    BasicTurbulenceModel::correctNut();
}
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Old   January 30, 2022, 17:31
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  #2
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Carl Dahmen
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Hey!


My code runs now, need to verify the result. It is attached for anyone interested.




Code:
\*---------------------------------------------------------------------------*/

#include "BatchelorGreen.H"
#include "fvOptions.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

namespace Foam
{
namespace LESModels
{

// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //

template<class BasicTurbulenceModel>
tmp<volScalarField> BatchelorGreen<BasicTurbulenceModel>::k
(
    const tmp<volScalarField>& voidfrac
) const
{
    volScalarField solidfrac(scalar(1)-voidfrac);

    volScalarField c1(a_*solidfrac+b_*sqr(solidfrac));

    return tmp<volScalarField>
    (
        new volScalarField
        (
            IOobject
            (
                IOobject::groupName("k", this->U_.group()),
                this->runTime_.timeName(),
                this->mesh_
            ),
            c1
        )
    );
}

template<class BasicTurbulenceModel>
void BatchelorGreen<BasicTurbulenceModel>::correctNut()
{
    
    volScalarField k(voidfraction_); 

    this->nut_ = this->nu()*k;
    fv::options::New(this->mesh_).correct(this->nut_);

    BasicTurbulenceModel::correctNut();
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

template<class BasicTurbulenceModel>
BatchelorGreen<BasicTurbulenceModel>::BatchelorGreen
(
    const alphaField& alpha,
    const rhoField& rho,
    const volVectorField& U,
    const surfaceScalarField& alphaRhoPhi,
    const surfaceScalarField& phi,
    const transportModel& transport,
    const word& propertiesName,
    const word& type
)
:
    LESeddyViscosity<BasicTurbulenceModel>
    (
        type,
        alpha,
        rho,
        U,
        alphaRhoPhi,
        phi,
        transport,
        propertiesName
    ),

    a_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "a",
            this->coeffDict_,
            2.5
        )
    ),

    b_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "b",
            this->coeffDict_,
            7.6
        )
    ),

    voidfraction_
    (
    IOobject
    (
        "voidfraction",
        this->runTime_.timeName(),
            this->mesh_,
        IOobject::MUST_READ,
        IOobject::NO_WRITE
    ),
    this->mesh_
    )

{
    if (type == typeName)
    {
        this->printCoeffs(type);
    }
}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class BasicTurbulenceModel>
bool BatchelorGreen<BasicTurbulenceModel>::read()
{
    if (LESeddyViscosity<BasicTurbulenceModel>::read())
    {
        a_.readIfPresent(this->coeffDict());
    b_.readIfPresent(this->coeffDict());

        return true;
    }
    else
    {
        return false;
    }
}



template<class BasicTurbulenceModel>
void BatchelorGreen<BasicTurbulenceModel>::correct()
{
    LESeddyViscosity<BasicTurbulenceModel>::correct();
    correctNut();
}


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace LESModels
} // End namespace Foam

Last edited by carlDahmen; January 30, 2022 at 20:14.
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Old   January 31, 2022, 18:25
Default It doesn't work
  #3
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Carl Dahmen
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Seems like the voidfraction is not updated, how do I declare it in the Header file?
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Old   February 3, 2022, 12:17
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Josh Williams
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Quote:
Originally Posted by carlDahmen View Post
Seems like the voidfraction is not updated, how do I declare it in the Header file?
In your header file you can put

Code:
volVectorField UsTilde_;



Or in your *.C file you can put somewhere
Code:
    const volScalarField& voidFraction = mesh.lookupObject<volScalarField>("voidFraction");
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Old   February 3, 2022, 20:11
Default Error message
  #5
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Carl Dahmen
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Thank you for your answer!

I have put in my correctNut() in the *.C file:
Code:
const volScalarField& voidfraction_ = this->mesh().lookupObject<volScalarField>("voidfraction");
But I get the error message:
Quote:
error: expected primary-expression before '>' token
Do you now what's wrong?
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Old   February 3, 2022, 20:49
Default Solved it!
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Carl Dahmen
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It's a template class and I needed:

Code:
const volScalarField& voidfraction_ = this->mesh().template lookupObject<volScalarField>("voidfraction");
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