Damping cable-based vibration control of pile-supported offshore wind turbine tower

Abstract

The towers of pile-supported offshore wind turbines (OWTs) are prone to large-amplitude, multi-modal vibrations due to their low inherent damping and high flexibility, and softer foundation compared to onshore wind turbines. To suppress arbitrary-modal vibrations of the tower, a novel damping cable energy dissipation system is proposed, which converts the angular displacement of the bending vibrations into linear displacement, thereby driving the viscous damper to dissipate vibrational energy. Firstly, a third-order dynamic differential equation for the foundation-tower-damping cable is established, which simulates the rotational constraint of the flexible foundation on the tower using a torsional spring. Based on this, an analytical solution for the additional damping ratio provided by the damping cable is derived. Secondly, model experiments are validated the effectiveness of the damping cable in suppressing vibrations. Additionally, the influence of rotational constraint stiffness on the vibration reduction effect is analyzed. Finally, the effectiveness of the damping cable in suppressing vortex-induced vibrations (VIV) is examined using a coupled tower-wake oscillator model, and the numerical simulation is used to simulate the effect of vibration damping under wave loading. The study results indicate that, with a low damping coefficient, the damping cable can effectively suppress arbitrary-modal vibrations. Additionally, a decrease in the rotational constraint stiffness can enhance the damping effect of the damping cable.