  Time irreversibility is a distinctive feature of non-equilibrium phenomena
such as turbulent flows, where irreversibility is mainly associated with an
energy cascade process. An Eulerian, multiscale analysis of time
irreversibility in wall-bounded turbulence is proposed in this study, which
differs from previous works relying on a Lagrangian approach and mainly
focusing on homogeneous turbulence. Outcomes reveal a strong connection between
irreversibility levels and coherent structures in both turbulent channel and
boundary layer flows. In the near-wall region, irreversibility is directly
related to the inner spectral peak originating from small-scale turbulent
structures in the buffer layer. Conversely, stronger irreversibility is found
in correspondence of the outer spectral peak originating from larger turbulent
flow scales far from the wall. Our results represent a first effort to
characterize Eulerian TI in wall-bounded turbulent flows, thus paving the way
for new developments in wall-turbulence modeling and control accounting for
broken temporal symmetry.
