  Large Eddy Simulation (LES) is a very useful tool when simulating turbulent
flows if we are only interested in its "larger" scales. One of the possible
ways to derive the LES equations is to apply a filter operator to the
Navier-Stokes equations, obtaining a new equation governing the behavior of the
filtered velocity. This approach introduces in the equations the so called
subgrid-scale tensor, that must be expressed in terms of the filtered velocity
to close the problem. One of the most popular models is that proposed by
Smagorinsky, where the subgrid-scale tensor is modeled by introducing an eddy
viscosity.
  In this work, we shall propose a new approximation to this problem by
applying the filter, not to the Navier-Stokes equations, but to a generalized
version of them with nonlinear viscosity. That is, we shall introduce a
nonlinear viscosity, not as a procedure to close the subgrid-scale tensor, but
as part of the model itself (see below). Consequently, we shall need a
different method to close the subgrid-scale tensor, and we shall use the Clark
approximation, where the Taylor expansion of the subgrid-scale tensor is
computed.
