Influence of Cross-Sectional Configuration on the Longitudinal Vortex Excitation of the Upstream Cylinder in Cruciform Two-Cylinder System

Abstract

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.

Keywords

• flow induced vibration
• flow control
• flow visualization
• wind tunnel experiment
• vibration suppression
• vibration generation