  We investigate the regime of fully developed homogeneous and isotropic
turbulence of the Navier-Stokes (NS) equation in the presence of a stochastic
forcing, using the nonperturbative (functional) renormalization group (NPRG).
Within a simple approximation based on symmetries, we obtain the fixed point
solution of the NPRG flow equations that corresponds to fully developed
turbulence both in $d=2$ and $d=3$ dimensions. Deviations to the dimensional
scalings (Kolmogorov in $d=3$ or Kraichnan-Batchelor in $d=2$) are found for
the two-point functions. To further analyze these deviations, we derive exact
flow equations in the large wave-number limit, and show that the fixed point
does not entail the usual scale invariance, thereby identifying the mechanism
for the emergence of intermittency within the NPRG framework. The purpose of
this work is to provide a detailed basis for NPRG studies of NS turbulence, the
determination of the ensuing intermittency exponents is left for future work.
