Ice loads and ice-induced vibrations of offshore wind turbine based on coupled DEM-FEM simulations

The drifting sea ice is a significant factor affecting the structural design and operation of offshore wind turbine (OWT) in cold regions. The extreme load and ice-induced vibration produced by sea ice can cause significant harm to the structures of OWT. In this study, a "strong" coupled model of the discrete element method (DEM) and finite element method (FEM) was adopted to investigate the impact of ice load and ice-induced vibration on the monopile foundation of OWT during the crushing process of sea ice. The sea ice and OWT were simulated through spherical particles in a parallel bonding mode and the Euler-Bernoulli beam element, respectively, and a "coupling" bridge was built to handle and transfer the DEM and FEM calculation parameters to achieve the "strong" coupling between the two methods. Subsequently, to examine the validity of the coupled DEM-FEM method in calculating the ice load on OWT, the ice load history and probability distribution obtained from a test in a 3-MW OWT model at Tianjin University as well as numerical simulation were compared and analyzed. In several simulations of the interaction between a 3.3-MW OWT and sea ice under various drifting speeds and thickness, some numerical results, such as ice load form, ice-induced vibration response of various parts, and mode of sea ice failure, were analyzed in several simulations. The simulation results obtained in this study primarily describe the phenomenon of the overall structural response of OWT to first-order vibration frequency and the conditions required for their generation. Therefore, the method and conclusions of this study provide a useful reference for the anti-icing design and anti-icing performance evaluation of monopile OWT in icy regions.