Abstract
The velocity fluctuations in the boundary layer around the separation point and in the near-wake of a cylinder were measured at Re = 3.7 × 104 ∼2.8 × 105. All the phenomena found seem to be interpreted by (1) the oscillation fore and aft of the separation point, (2) the transverse oscillation of the separated shear layer, (3) the temporary immersion in the ``tongue'' of potential flow and (4) the oscillation in the plane of the axis of wake vortex.