E114 球後流における渦放出周波数のレイノルズ数依存性

概要

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Reynolds number dependence of vortex shedding was experimentally investigated in a wake of a sphere for Re=1717∿20000. Vortical structure was obtained through a smokewire visualization and multi-hotwire measurement and the Strohal number also was evaluated by spectral analysis. For the Reynolds number from 800 to 6528,the spectral analysis on the velocity fluctuation showed the existence of two dominant frequencies; the high mode and the low mode. The high-mode Strohal number corresponding to the shedding frequency of a hairpin-like vortex increased discontinuously with the Reynolds number. The large-scale structure which corresponds to the low-mode Strohal number was composed of several hairpin-like vortices. A number of the hairpin-like vortices in the each large-scale structure increased with the Reynolds number. For the higher Reynolds number range of Re>6528,the high-mode Strohal number disappeared and the hairpin vortices in the each large-scale structure transited to turbulence through their mutual interaction. At Re=20000,the large-scale structure became staggeredly arranged and passed alternately on the opposite sides of the sphere wake.
日本流体力学会の論文
2002-07-23