Concern over the Vortex-induced Motions (VIM) acting on offshore structures, with special focus on monocolumn and spar platforms, mooring systems have crucial importance on system movements; the system has thus been transformed into a concept study herein. A floating and rigid circular cylinder with low aspect ratio (L/D = 2) was used in the experiments carried out to investigate the influence of stiffness ratio (kx/ky) on Vortex-Induced Vibration (VIV). The cylinder was mounted in an elastic base composed of four springs with differences in in-line and transverse stiffness, defining: kx/ky ≅ 0.3, 0.5, 1.0, 2.0 and 3.0. The Reynolds number analysed belongs to a range between 0.2 · 104 and 2 · 104. Some good qualitative and quantitative agreements are found for in-line amplitudes, and higher kx/ky systems demonstrate significant oscillation for low relative velocities. This variation can be seen and justified when the XY-plane trajectories were plotted. When kx/ky is defined as 2 and 3, the traditional VIV 8-shape is illustrated for reduced velocities between 3 and 6. In contrast, the other stiffness systems do not show significant movements and, consequently, a negligible XY shape. Roll and pitch degrees of freedom have shown the motions coupled with the transverse and the in-line motions respectively. Moreover, the yaw motion did not present considerable angles. kx/ky = 2 has presented the highest lift force coefficients, without a great difference from the other aspects ratios, though. The drag force coefficient showed constant values for kx/ky = 2 and 3, the smallest results were observed for the system kx/ky = 3.

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