| Summary: | In earlier works by the present authors, it was shown that a large cross-flow excitation is induced to a circular cylinder by setting another cylinder downstream in a cruciform arrangement with a certain gap between them, caused by longitudinal vortices shedding periodically around the crossing. In this work, influence of the cross-sectional configuration of cylinders forming a cross on the longitudinal vortex excitation was investigated by wind tunnel experiments. Three systems, i.e. a two-circular-cylinder, a circular-cylinder/strip-plate and a square-cylinder/strip-plate system, with essentially equal structural parameters were compared. In the case of the circular-cylinder/strip-plate system, the trailing vortex excitation occurs over much wider velocity region, while the necklace vortex excitation is indefinite, as compared with the two-circular-cylinder system. In the case of the square-cylinder/strip-plate system, vortex excitation occurs in a certain velocity region of the galloping of single cylinder attributed to the necklace vortex.
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