[Marc10]

Hi!

I am trying to implement a boundary condition based on the Navier slip model, where the velocity at the wall is a function of the velocity gradient at the wall:

U = ls * du/dn

For this, I have to access du/dn (the velocity gradient normal to the wall) in the field. Is there a function for this similar to this->patchInternalField()? As a starting point I use the partialSlip bc from OpenFoam.

template<class Type>
void Foam::partialSlipFvPatchField<Type>::evaluate
(
    const Pstream::commsTypes
)
{
    if (!this->updated())
    {
        this->updateCoeffs();
    }

    tmp<vectorField> nHat = this->patch().nf();

    Field<Type>::operator=
    (
        (1.0 - valueFraction_)
       *transform(I - sqr(nHat), this->patchInternalField())
    );

    transformFvPatchField<Type>::evaluate();
}

Here I guess I just have to replace the operator= argument with the above equation. But how can I access or calculate the gradient at or in the cell next to the wall?

I appreciate any help! Thank you!

marc