Macro-Models for Anchor and Chain-Soil Interaction in Floating Offshore Wind Analyses

Abstract

Abstract A numerical formulation is introduced for modelling the dynamic interaction between the mooring line (chain) and the soil, extending to the connection point at the anchor (pad-eye) in a fully integrated analysis of an offshore wind turbine generator, floating support structure and mooring system including the anchors. The anchors and the segments of the mooring line in contact with the soil are modelled by macro-models. The macro-models describe the coupled non-linear relationship between incremental displacements and the resultant soil reaction forces at each node along the mooring line in contact with the soil and at the pad-eye in a 3-dimensional space. The calibration of the input for two distinct types of anchors - suction caisson anchors and fluke anchors in clays, is presented. By implementing these macro-models into a tool for simulating the dynamic behavior of the floating offshore wind turbine, the design process of the anchors can be faster and more accurate. Importantly, a holistic approach to the mooring system design, including the interaction with the soil, has the potential to optimize the design and reduce the costs. It also enables the prediction of the potential development of complex mechanisms such as seabed trenches during repeated motion of the mooring line in contact with the soil. An example is briefly presented to demonstrate the application of this integrated analysis of floating offshore wind turbines, emphasizing the additional input required.