implement roughness boundary conditions for Spalart-Allmaras
 

Hello, all

I'm a new foamer and need help on this problem.

I'm trying to apply the roughness boundary condition on the wall with S-A model.

the wall boundary condition will be : d(nutilda)/dn=nutilda/(d_+0.03*hs)
where d_ is the distance to the wall, which is a variable in the S_A model
hs is the roughness height

my question is howI can implement this new boundary condition.
here is my thought:
there is one basic fixedGradient boundary condition which maybe is a good prototype for me. I will change the evaluate member function in order to get value of (nutilda/(d_+0.03*hs)) for the gradient of nutilda , but I'm so clumsy at C++ and FOAM right now and don't know how to make it happen.

here is the evaluate function:
__________________________________________________ _______________________
template<class Type>
void fixedGradientFvPatchField<Type>::evaluate(const Pstream::commsTypes)
{
if (!this->updated())
{
this->updateCoeffs();
}

Field<Type>::operator=
(
this->patchInternalField() + gradient_/this->patch().deltaCoeffs()
);

fvPatchField<Type>::evaluate();
}
__________________________________________________ ________________________

Thank you all
Wei