Wind Tunnel Experiments on Vortex-Induced Vibration of a High Mass-Ratio Flexible Circular Cylinder

Vortex-induced vibration (VIV) of a fully submerged, highly-flexible circular cylinder placed horizontally in the test-section of a subsonic wind tunnel is studied experimentally. The cylinder is tension-dominated with an aspect ratio of 47 and a high mass ratio of 120. Two synchronized high speed cameras recorded the oscillations of the cylinder in the crossflow and inline direction for a reduced velocity range of U*=3.6-63, corresponding to a Reynolds number range of Re=187-1530. Continuous response of the cylinder is reconstructed from limited number of measurement points based on modal expansion theorem modified using Modal Assurance Criterion. Previous studies on VIV of flexible cylinder are carried out either on low mass ratio cylinders in water tunnel or low aspect ratio cylinders with high mass ratio in wind tunnel. Owing to the high-flexibility of the cylinder used in the current experiment, mono- and multi-frequency responses as well as transition from low mode numbers to high mode numbers for a high mass ratio and high aspect ratio flexible cylinder are observed. The dynamic response of the cylinder is also compared to those of a low mass ratio flexible cylinder in the similar Reynolds number range tested.