We collect and discuss the results of our recent
studies which show evidence of the existence of
a whole family of self-sustaining motions in wallbounded
turbulent shear flows with scales ranging
from those of buffer-layer streaks to those of largescale
and very-large-scale motions in the outer layer.
The statistical and dynamical features of this family
of self-sustaining motions, which are associated with
streaks and quasi-streamwise vortices, are consistent
with those of Townsend’s attached eddies. Motions
at each relevant scale are able to sustain themselves
in the absence of forcing from larger- or smaller-scale
motions by extracting energy from the mean flow via
a coherent lift-up effect. The coherent self-sustaining
process is embedded in a set of invariant solutions of
the filtered Navier-Stokes equations which take into
full account the Reynolds stresses associated with the
residual smaller-scale motions.