  In this work, we carried out direct numerical simulations in large channel
domains and studied the kinematics and dynamics of fully localised turbulent
bands at Reynolds number Re = 750. Our results show that the downstream end of
the band features fast streak generation and travels into the adjacent laminar
flow, whereas streaks at the upstream end continually and relatively more
slowly decay. This asymmetry is responsible for the transverse growth of the
band. We particularly investigated the mechanism of streak generation at the
downstream end, which engines the growth of the band. We identified a spanwise
inflectional instability associated with the local mean flow near the
downstream end and our results strongly suggest that this instability is
responsible for the streak generation and ultimately for the growth of the
band. Based on our study, we propose a possible self-sustaining mechanism of
fully localised turbulent bands at low Reynolds numbers in channel flow.
