抄録
The flow pattern at the later stage of the laminar-turbulent transition in a flat plate boundary layer was visualized in a water channel by hydrogen bubble technique, and wave forms of velocity fluctuations were recorded by a coated hot-wire probe, also the in-stants of taking pictures were recorded below the wave forms. The comparison between the flow patterns and the wave forms showed that the so-called spikes in wave forms occurred due to the induced velocity of hairpin eddies of small size, which were generated through the instability of the high shear layer at about a half depth of the boundary layer, and that the hairpin eddies increased in number in the streamwise direction. Eventually, a local turbulent flow was observed in a similar way to the experiments by Nishioka et al. in a plane Poiseuille flow. The local turbulent flow had, however, not the same features as a so-called turbulent spot generated by local large disturbances in a laminar boundary layer.
