Failure analysis and load mitigation of underwater structures in floating offshore wind turbines

An innovative calculation framework has been developed to explore the thrilling aero-hydro-mooring-cable dynamics of a floating offshore wind turbine (FOWT) under extreme sea conditions, considering various dramatic failure scenarios of underwater structures. This groundbreaking approach combines cutting-edge numerical calculations using the vector form intrinsic finite element (VFIFE) method with a dynamic model experiment in a water tank to validate the numerical results. The study delves into the motion responses of the floating structures, the intense tensions of mooring lines and cables, and the stress distribution along the cable in two different failure scenarios: dragging anchor of mooring line and power cable breakage. To mitigate cable load and prevent breakage, a novel scheme of installing additional elastic supports at both ends of the cable is proposed. The optimal stiffness range of these elastic supports is determined through theoretical investigation based on an equivalent spring pendulum model, and its effectiveness is confirmed by comparing detailed VFIFE calculations with model experiment results. The findings demonstrate that the calculation framework excels in handling rigid-flexible coupling dynamic problems with sudden failure behavior, offering valuable insights for predicting and preventing underwater structure failures in extreme sea conditions for FOWTs. © 2025 Elsevier Ltd.