Experimental investigation of downstream cylinder vibrations caused by FIV in the presence of upstream stationary cylinder

Abstract

The mechanism of flow induced vibrations (FIV) exists in many engineering applications and plays a significant role. In offshore engineering, the risers subjected to flow induced vibrations. In this study, two circular cylinders of different diameters are arranged in tandem manner. In cross-flow transverse direction, the upstream cylinder is fixed, while the downstream cylinder is subjected to vibrations. This study carries out experiments in wind tunnel, which focuses on significant vibration-galloping. Variable mass-damping ratio is used to achieve the critical velocity corresponding to onset galloping vibration. In the present study, the diameter ratio is 0.4 and the gap L is 1.5D, and 3.5D. In the wind tunnel experiments, by changing the mass of the vibrating cylinder, the corresponding values of damping ratio, results in variable mass damping ratio m*ζ. For each value of m*ζ, the amplitude, frequency at every reduced velocity will be obtained at first, the critical velocity and stability map will be summarized. At static area between lock-in and galloping (desynchronization branch), a uniform initial displacement was set to get the total damping ratio. This study also investigates the relationship among the total damping ratio, m*ζ and critical velocity.