正浮力後流の三次元熱流動解析 : 第2報,等温後流の三次元構造(熱工学,内燃機関,動力など)

概要

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The isothermal wake from a circular cylinder at the Reynolds number Re=300 was analyzed by a DNS computation, computed results were discussed, and features of 3 D motion were elucidated as follows: Qualitative features of the vorticities ω_x, ω_y with the upward direction and the horizontal directions and the velocity w in the cylinder axis direction were revealed by an analogy of the vorticity ω_z in the cylinder axis direction. The vortex dislocation was visualized in the farwake streaklines, had a band spectrum of time trace of the upward velocity, and was found to be resulted from the w motion. A mechanism of the vortex dislocation was made clear by the w motion which was different between the nearwake with f_p=f_<wake> and farwake with f_p=2f_<wake>, here f_p is the dominant frequency and f_<wake> is the wake frequency. The wave lengths of ω_x and ω_y were 1, i. e. the B mode oscillation, in the nearwake, and 2, i. e. the C mode oscillation, in the farwake. The 3D oscillation in the isothermal Karman vortex street at Re=300 was therefore composed of the B mode with the wave length 1 in the nearwake and the C* mode with both the length 2 and the vortex dislocation in the farwake.
一般社団法人日本機械学会の論文
2004-05-25