Time-domain analysis of vortex-induced vibrations of lazy-wave dynamic power cables with curvature-dependent bending stiffness

In this paper, vortex-induced vibrations of a lazy-wave dynamic power cable were simulated using a time-domain VIV model in RIFLEX. The effects of curvature-dependent bending stiffness, discrete buoyancy modules, current speed, current profile, and inflow angle on the VIV response were investigated. A discrete buoyancy module representation was introduced by converting the distributed buoyancy section of the reference model into discrete buoyancy modules while preserving the overall buoyancy effect. The VIV force model was applied to the bare cable elements, whereas the buoyancy module elements were represented using Morison-type drag and inertia loads with local bending stiffness. The results showed that the buoyancy modules in the Hog section modified the spatial peak pattern and vibration transmission along the cable. The Stick, Slip, and Bilinear bending stiffness models were then compared under uniform and sheared current conditions. The Slip model produced shorter spatial wavelengths, higher response orders, and higher frequency content than the Stick model. The Bilinear model showed curvature-dependent response characteristics rather than a simple intermediate behavior between the two limiting stiffness models. Curvature exceedance and wavelet analyses further showed that the Hog section, oblique inflow, and current shear produce localized and time-varying VIV response characteristics. These findings demonstrate the advantage of time-domain Bilinear modeling in capturing localized stiffness transitions and the resulting non-stationary VIV characteristics compared with constant Stick or Slip stiffness assumptions.