Influence of a cruciform arrangement downstream strip-plate on crossflow vibration of a square cylinder

Koide, Mizuyasu and Kato, Naoto and Yamada, Shuichi and Kawabata, Yusuke and Takahashi, Tsutomu and Shirakashi, Masataka (2007) Influence of a cruciform arrangement downstream strip-plate on crossflow vibration of a square cylinder. JOURNAL OF COMPUTATIONAL AND APPLIED MECHANICS, 8 (2). pp. 135-148. ISSN 1586-2070

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Abstract

In earlier works, the present authors found that the Kármán vortex excitation of a circular cylinder is effectively suppressed by setting another cylinder in cruciform arrangement downstream with a gap-to-diameter ratio s/d less than 0.5, and that new vortex excitations are induced by two types of longitudinal vortices shedding periodically near the cross in higher velocity ranges. In this work, influence of a strip-plate set downstream in cruciform arrangement on the vibration of a square cylinder is investigated by wind tunnel experiment. The Kármán vortex excitation is well suppressed by the strip-plate with a width w equal to the side of square d when s/d < 2. The galloping is also completely suppressed by the plate when s/d < 4, except the range of 1 < s/d < 2. In the latter range of s/d, a new vibration occurs and its maximum amplitude at s/d around 1.3 is double the original galloping. Flow visualization by tuft grid and velocity measurement show that this vibration is caused by the longitudinal vortex shedding periodically near the cross which synchronizes with the cylinder motion, similar to the case of a two-circular-cylinder system.

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