後流中に置かれた円柱まわりの流れ : 静止の時の抵抗とストローハル数

概要

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Pressure distribution, drag coefficient and Strouhal number of tandem circular cylinders were measured in a wind tunnel. Furthermore, we simulated flow beyond the critical Reynolds number, using surface roughness. Flow-characteristics around a downstream cylinder immersed in a wake of an identical cylinder were investigated in detail. We found that at subcritical Reynolds numbers, a wake behind the downstream cylinder consists of two kinds of predominant componets with different frequencies, i. e. one component due to a vortex-street shed from an upstream cylinder (Strouhal number, S_t=0.2) and the other due to a vortex formed just behind the downstream cylider (s_t=0.12-0.18). At high subcritical Reynolds numbers, a reduction in the drag force on the downstream cylinder becomes more apparent with an increase of Reynolds number and is clearly due to the influences of turbulence in the wake, which results in a strong dependence of the drag force upon Reynolds number. It was found, in addition, that the Strouhal number of the downstream cylinder changes from 0.18 to 0.3 with an increase of Reynolds number, although the Strouhal number of the upstream cylinder is 0.2. In the transcritical region simulated with the aid of surface roughness, the drag force on the cylinder in a wake is no longer dependent upon Reynolds number.
一般社団法人日本機械学会の論文
1984-10-25