平面壁上の有限長円柱の渦流出に及ぼす縦横比の影響

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This paper describes the formation and decay of vortex shedding and turbulent eddies from a circular cylinder of finite length placed on a ground plane. The experiment was carried out in an N. P. L. blowdown-type wind tunnel having a working section of 500mm×500mm×2000mm in size at the Reynolds number 2.5×10^4. The power spectrum, auto-correlation and space-correlation were measured and the Strouhal number was determined. The vortices of two types shed from a circular cylinder have also been observed. As a result, it was found that (i) the vortices shed from a circular cylinder are arch vortices for H/D=1 and 2, and change into Karman vortices at H/D=4〜7; (ii) the number of turbulent eddies of a large scale contained in the turbulent near wake increases as the downstream distance increases, and the scale of eddies in the near wake enlarges with an increase in the value of H/D.
1991-05-25