CFD Online Discussion Forums - operator= in inletOutlet boundary condition

Hello to all,

I am studying the inletOutlet boundary condition.

In the update coeffs there is:

Code:



template<class Type>

void Foam::inletOutletFvPatchField<Type>::updateCoeffs()

{

    if (this->updated())

    {

        return;

    }



    const Field<scalar>& phip =

        this->patch().template lookupPatchField<surfaceScalarField, scalar>

        (

            phiName_

        );



    this->valueFraction() = 1.0 - pos0(phip);



    mixedFvPatchField<Type>::updateCoeffs();

}

The assignment of the value fraction is given by the pos0 function which will return 1 if phi>=0 else it will be 0.

The mixed boundary condition is given by:
$\phi_f = w\phi_{ref} + (1-w)(\phi_C + \Delta\nabla \phi_{ref})$

This means that, when I have positive flux I will get fixedGradient and when I get negative flux I will get fixed value.

However, there is the existance of a operator= in the function which will be called e.g, in the PEqn.H when the velocity is reconstructed.

And it is defined as:

Code:

template<class Type>

void Foam::inletOutletFvPatchField<Type>::operator=

(

    const fvPatchField<Type>& ptf

)

{

    fvPatchField<Type>::operator=

    (

        this->valueFraction()*this->refValue()

        + (1 - this->valueFraction())*ptf

    );

}

Why is this needed?