十字交差二円柱から周期的に流出する縦渦による上流円柱の縦渦励振 : 縦渦励振に及ぼす構造減衰の影響(流体工学,流体機械)

概要

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The cross-flow oscillation behavior of the upstream cylinder in a criss-cross circular cylinder system was investigated using a wind tunnel. The trailing vortex is formed and shed periodically near the crossing when the gap-to-diameter ratio is 0.00 to 0.25, and the necklace vortex is shed when the gap-to-diameter ratio is 0.25 to 0.50. When the logarithmic damping factor is small, the oscillation amplitude is large over a wide range of the free stream velocity. In this velocity range, the shedding of the longitudinal vortices always synchronizes with the oscillation of the upstream cylinder, showing that the large oscillation is a vortex excitation. Increasing the logarithmic damping factor, the maximum oscillation amplitude becomes smaller and the excitation range becomes narrower. The maximum damping for the occurrence of the necklace vortex excitation is more than 2.5 times larger than that of Karman vortex excitation, while that of the trailing vortex excitation is the half of the Karman vortex excitation. The longitudinal vortex excitation regime is presented by a curve on the Scruton number-relative frequency deviation plane.
一般社団法人日本機械学会の論文
2003-01-25