円管助走部流れにおける孤立乱流塊の発生条件(境界層・せん断流・遷移(3),一般講演)

概要

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Laminar-Turbulent transition of a boundary layer forced by a jet in the inlet region of a circular pipe was experimentally investigated. The jet was inserted radially from a small hole in the inlet region into the pipe flow periodically. Isolated turbulence patches were generated by the jets, then they propagated downstream. The threshold value of the jet flow rate to generate the turbulent patch was obtained. The threshold value was low when the jet duration was long. The threshold value varied as Re^<-1> at downstream position, though it changed as Re^<-4> just after the jet exit. The turbulence level was kept constant as the variation of jet flow rate, though the duration increased with the increase of jet flow rate. The turbulence level was kept constant as the variation of jet duration.
2010-09-09