One degree-of-freedom vortex-induced vibrations at constant Reynolds number and mass-damping

Free vibration experiments of a circular cylinder undergoing vortex-induced vibrations are performed using a cyber–physical system. Amplitude, force and frequency response measurements for four cases of constant mass-damping (\(m^*\zeta\)) at a constant Reynolds number (\({Re} = U_\infty D/\nu\)) of 4000 are presented and compared to the literature values. The results show that mass ratio (\(m^*\)) is the dominant parameter governing the response in the initial branch, while \(m^*\zeta\) governs the amplitude response in the lower branch and desynchronization regions. In the upper branch, the Reynolds number and \(m^*\zeta\) both strongly affect the amplitude response. Following a decomposition of the total hydrodynamic force into added mass and circulatory components, it is shown that the circulatory force is strongly related to \(m^*\) in the initial branch, and \(m^*\zeta\) in the upper and lower branches. The total force is found to be insensitive to changes in \(m^*\) and \(m^*\zeta\) in the lower branch and desynchronization regions. An analysis of the extent of amplitude modulations is performed by comparing the amplitude response calculated by the highest \(10\%\) of peaks method and the mean of all peaks method. The results indicate that lower structural damping values lead to larger modulations in the initial and upper branch regions regardless of \(m^*\).