4035 層流斑点の乱流斑点への遷移(G05-8 境界層・はく離,G05 流体工学)  [in Japanese] 4035 Transition of a Laminar Spot into a Turbulent Spot  [in Japanese]

It was known that disturbance, introduced artificially into a supercritical laminar boundary layer along a flat plate by a small jet, is still laminar during the initial stage of its downstream evolution. Thus, we named it a laminar spot because it resembled a turbulent spot. Measurements using a 16ch rake-type probe have shown that in the first stage of its downstream evolution, a spot grew at about 5°in spanwise. After then, it developed with the same growth angle, about 10°, as that of a turbulent spot. However, the velocity profile of the spot has still kept the feature of a laminar spot. The purpose of this study was to investigate a transition of a laminar spot into a turbulent spot using a new type parallel hot-wire probe. From results obtained, we found that low-speed region at the tail of the spot develops downstream and a strong turbulence occurs suddenly in this region.