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

Abstract

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 $$m^*$$ .