乱流斑点への遷移領域における不規則性の発達

概要

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A spot, generated by an artificial disturbance introduced into a laminar boundary layer, had a highly reproducibility in its velocity perturbations during the initial stage of its downstream development. Thus, we called it a ``laminar spot and investigated its downstream development in detail. The purpose of this study was to investigate the generation and the development of an irregularity observed in the velocity waves during the laminar-turbulent transition of the spot. The results obtained show that those irregularities appeared locally in the low-speed region away from the wall and spread wide close to the wall. In the beginning, lateral distortion of velocity profile due to the vortex-interaction caused the irregularity of the velocity-wave amplitude in the boundary between the low- and high-speed regions in the spot. In addition, the crossover of legs of the longitudinal vortices occurred incidentally in the spot and generated a local ejection of low-momentum fluid. Afterwards, some crossovers of legs were produced in a chain reaction. Consequently, the reproducibility in the velocity waves disappeared almost in the downstream and turbulent regions increased rapidly everywhere in the spot.
社団法人日本航空宇宙学会の論文
2010-07-05