Water tunnel experiments on transverse-galloping of cantilevered rectangular and D-section prisms

Abstract

In the case of an elastically mounted rectangular prism with a side ratio of less than D/H = 0.5 (where D: depth of a bluff body in the flow direction, H: height of a bluff body normal to the flow direction), it is well known that low-speed galloping appears at a lower reduced velocity than the resonant reduced velocity. In order to investigate the effects of the geometric shape of the bluff body's cross section on the flow-induced transverse vibration, we performed free-vibration tests of cantilevered prisms with two kinds of cross sections, i.e., rectangular and D-section prisms. The effects of the side ratio D/H and the turbulence intensity of the free stream on the flow-induced vibration were also investigated. The response amplitude of the transverse vibration increases with a decrease in the side ratio. The response amplitude of a D-section prism with D/H = 0.23 vibrates at a lower reduced velocity than a rectangular prism with D/H = 0.2, and the increment rate of the response amplitude for a D-section prism with D/H = 0.23 is higher than that of the other prisms. It is found that the free- vibration characteristics of rectangular and D-section prisms are influenced by the high turbulence of the free stream.