Flow-induced vibration of an elastically sphere at high combined mass-damping parameter

The paper reports the results of the experimental analysis on the transverse flow-induced vibration of an elastically mounted rigid sphere in a free surface flow. Simultaneous displacement and velocity measurements have been used to describe the free vibrations. Experiments have been performed referring to low mass ratio value (m*), high combined massdamping parameter (m*ζ), small amplitude (A/D<1) and low values of relative submergence (ratio between water depth and sphere diameter). Preliminary results compared to the literature case studies suggest a different behaviour between the test case of the sphere and those referred to the cylinder mainly concerning the lock-in and hysteresis phenomena.