Tip amplitudes of an isolated cantilever cruciform cylinder were measured, varying flow velocity approaching the cylinder and flow angles with 0° and 45° to a water test channel in order to investigate the vibration behavior and critical velocity for bending vibration. Flow velocity varied from about 0.4 m/s to 3.3 m/s, which corresponds to from 0.4 to 3.0 in reduced form using wing length of cruciform cylinder and from 1.6×104 to 1.4×105 in Reynolds number. The amplitudes were measured using strain gauges installed at the cylinder. In the case of 45°, it was observed that the amplitudes increased drastically in two regions. One region was from 0.65 to 1.0 in reduced velocity and oscillating direction is drag direction; the other was from 1.0 to 1.6 and oscillating direction is lift direction. On the other hand, such large amplitude vibration was not observed in the case of 0°. According to previous study on Strouhal number of vortex shedding from a cruciform cylinder, Strouhal numbers are 0.2 and 0.9. Therefore, this large amplitude vibration is not thought to be due to the resonance with the vortex shedding.

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