VIVs of a circular cylinder with a downstream strip-plate in cruciform arrangement

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• 作者：Naoto Kato^a ; ^{note@cc.utsunomiya-u.ac.jp} ; Mizuyasu Koide^b ; Tsutomu Takahashi^c ; Masataka Shirakash^c
• 关键词：Flow-induced vibration ; Wind tunnel experiment ; Vortex excitation ; Longitudinal vortex ; Vibration control
• 刊名：Journal of Fluids and Structures
• 出版年：2012
• 期刊代码：187_08899746
• 类别：et
• 出版时间：April, 2012
• 卷：30
• 期：Complete
• 页码：97-114
• 文件大小：2890 K

摘要

Earlier wind tunnel experiments by the present authors on the transverse vibration of a circular cylinder with a downstream counterpart in cruciform arrangement showed that either of the two longitudinal vortices - trailing or necklace vortices, depending on the gap-to-diameter ratio s/d - induces a resonant oscillation, like the K谩rm谩n-vortex-induced vibration (KVIV). In this study, the downstream cylinder is replaced by a strip plate with a width w comparable in magnitude with the cylinder diameter d, expecting that interference of a plate would be stronger than that of a circular cylinder. The characteristics of longitudinal vortices and VIV of the upstream cylinder are investigated through wind tunnel experiments over the range of Reynolds number 3 000鈭?2 000, as well as a visualization experiment in a water tunnel at around Re=1 700. When the system is fixed, the two longitudinal vortices (trailing and necklace) shed periodically over respective ranges of s/d for plates with 0.5鈮?em>w/d鈮?.62, while the trailing vortex sheds periodically but the necklace vortex is not observed for plates with 0.75鈮?em>w/d鈮?.0. When the cylinder is elastically supported for transverse vibration, the plate effectively suppresses KVIV, at distances further downstream for larger w/d plates. An unexpected effect is that KVIV is enhanced by the plate with 0.5鈮?em>w/d鈮?.0 over a certain range of s/d. The two longitudinal vortices induce resonant vibrations under conditions of w/d and s/d correlating with their characteristics for the fixed system. The velocity ranges of the trailing vortices are much wider than for the case of the two-circular-cylinder system. The effects of the downstream plate on VIV can be utilized for oscillation control, i.e., not only to suppress but also to induce oscillations for beneficial purposes.