Suppression of flow-induced vibration of a circular cylinder by means of a flexible sheet

In this study, the suppression of flow-induced vibration of an elastically supported circular cylinder by attachment of a flexible sheet was investigated experimentally. In particular, the dependence of flow-induced vibration characteristics of the circular cylinder upon the flow velocity was investigated in detail by axially attaching the flexible poly-ethylene sheet to the cylinder surface. The characteristics of the flow-induced vibration of the cylinder were investigated by changing the attachment angle theta and the length / of the flexible sheet (rectangular type) as experimental parameters in various combinations. The angle theta was set at five different angles, 90 degrees, 45 degrees, 0 degrees, -45 degrees and -90 degrees. The angle's base point was the back side stagnation point of the cylinder. The length / of the flexible sheet varied from 0.5 to 3.0 times of the cylinder's diameter at the interval of 0.5 times. The width T of the flexible sheet along the span of the cylinder also varied in 7 cases from 1.0L to 0.4L (L is the length of the cylinder) in order to discover the minimum width of the sheet necessary to effectively suppress the flow-induced vibration of the cylinder. Furthermore, the flexible sheet of the minimum width was split into 2 to 5 pieces and attached to the cylinder, and changes in the flow-induced vibration characteristics were investigated. Also, vibration characteristics were investigated for a flexible sheet in the shape of an isosceles triangle. As a result, the optimal length / and minimum width T of the flexible rectangular sheet were found to be 2 similar to 2.5D and 0.7L, respectively, to suppress the flow-induced vibration of the cylinder. Most importantly, it was found that the sheet located at the back side stagnation point can suppress the flow-induced vibration generated by any directional flow to strike the front surface of the cylinder.