ABSTRACT
On the other hand, for singularly perturbed problems where some artificial
viscosity (or similar regularization) is usually employed, the idea of using only
a kind of subgrid viscosity (or subgrid regularization,) as in (3.16), is surely
appealing for its simplicity and rather wide range of applicability. However,
as we have seen, the choice of the subgrid artificial viscosity sa appears to be
crucial, and requires deeper investigations.
