[newGuyAtCFD]

Hello to all,


I am studying the inletOutlet boundary condition.


In the update coeffs there is:

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:


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:

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?