  Turbulent stripe, which would occur in turbulent channel flows at
transitional Reynolds numbers, was studied experimentally by flow visualization
using reflective flake particles. In a range of bulk mean Reynolds number Re =
1700-2000, the turbulent stripe was observed to be inclined at angles of 20-30
degree against the streamwise direction, and its streamwise wave length was
about 60 times of the channel half width ($\delta$). The longitudinal streaks
with the spanwise spacing of 1.6$\delta$ were found in the quasi-laminar
regions. The critical Reynolds number was Re = 1300. Time traces of the
streamwise velocity were measured by laser Doppler velocimetry, revealing
similarity to the equilibrium turbulent puff in the transitional pipe flow.
