Dynamic response of novel offshore wind turbine with shear-thickening-fluid damper

As offshore wind power advances from nearshore to deep-sea areas, the floating offshore wind turbines (FOWTs) have emerged as the most promising wind power technology. The towering profiles of FOWTs make them prone to vibrations under the complex dynamic wind, wave and current loads, leading to fatigue damage accumulation and risk of fracture. This paper innovatively proposes replacing the traditional tuned mass or liquid dampers with shear-thickening fluid (STF) damper to control motion of the spar-type FOWTs and prolong its service life. The deformation equation of spar-type FOWT subjected to time-varying aero-hydro-servo-elastic loadings is derived based on the Lagrange's equation. The nonlinear deformation induced by STF is formulated via Ritz method and solved by Newton-Raphson iterative method. Based on the obtained displacement fields, the fatigue life is evaluated using the classical Paris’ law. A simple and useful fatigue life formula with respect to velocity of wind is given. The analysis demonstrates that the incorporation of STF can significantly reduce tower deformation and effectively improve fatigue life of FOWT. As the increase of fluctuation period of wind, deformation of the STF-equipped FOWT tends to converge with that of a system mounted with Newtonian fluid of equal weight. A lower installation position of STF results in a better kinetic stability and a longer fatigue life. The relative improvement in fatigue life achieved by STF over Newtonian fluid increases with the initial crack length but hardly varies with stress ratio and wind velocity. This work provides a new design strategy for vibration reduction and service life extension of offshore floating wind turbines.