Mass ratio effect on vortex induced vibration of a flexibly mounted circular cylinder, an experimental study

The effect of mass ratio (m∗ = the mass of oscillating body/the mass of displaced fluid) on vortex induced vibration of an elastically mounted rigid circular cylinder over a wide range of Reynolds numbers (1.7 × 104 < Re < 7 × 104) in a high damping system is studied in this paper. The cylinder is limited to a transverse oscillation and is carried inside a 14 m long water channel for constant velocities. The amplitude of response depends on various parameters such as mass ratio, damping ratio, natural frequency of system and Reynolds number. Here we considered three different circular cylinders with the same diameter and length, but distinct masses (m∗ = 1.6, 2.3 and 3.4). The experiments carried out in a towing-tank water channel and the following results achieved: the peak amplitude of oscillation principally depends on the mass ratio and it increases with decrease of m∗. For systems with constant mass-damping parameters, by reducing the mass ratio, the maximum amplitude of oscillation remains constant, while the range of synchronization increases considerably. Higher Reynolds numbers in our experiments led to reach the same maximum amplitude of oscillation as some of the previous studies (A∗ = 1), even with higher mass-damping parameter (m∗ζ) in our system. The high damping in our experiments, resulted in disappearance of the lower branch in the amplitude response graphs.