Numerical investigation on vortex-induced vibration of vertically suspended multilayer cables subjected to nonlinear shear flow

Suspended cables are susceptible to vortex-induced vibration (VIV) in the complex marine environment. Previous studies on the VIV response of suspended cables are relatively limited. This study focuses on the vertically suspended cables that connect the fixed wind turbine foundation to the cable buried under the seabed. Based on a well-verified FEM-FVM coupling model, the VIV response and stress distribution characteristics of the cables are investigated under the nonlinear shear flow conditions. It is found that the vibration process of the cable exhibits relatively stable single-mode characteristics at lower environmental velocities, while it is more prone to the multi-mode vibration response at higher environmental velocities. The cable is mainly dominated by the high-order frequency at the vibration amplitude peak, while it is mainly characterized by the low-order frequency at the vibration amplitude trough. A clear “O”-shaped vibration trajectory can be observed under the 1st-order vibration mode, but a chaotic and disordered vibration trajectory is shown under the blending of the 1st- and 2nd-order vibration modes. In addition, the cable is found to be susceptible to fatigue damage at the amplitude peak. The above conclusions can provide the technical support for the design of the suspended cables.