Dynamic Simulation Procedure of Mooring System for a Floating Offshore Wind Turbine Platform

Mounting a wind turbine on a floating platform allows the wind power generation more efficient and economically feasible in deeper water areas. For a floating offshore wind turbine (FOWT) system, a suitable mooring system is essential to ensure a safe and reliable operation of the entire system. However, during the design phase of a mooring system, various designs and its detailed parameters can quickly rack up the total number of simulations needed. In this study, a design procedure was proposed to capture various simulation stages and critical checkpoints for design validations of mooring systems. After identifying relevant design and evaluation parameters for the mooring system, the design procedure begins with free decay analyses and restoring performance assessments of the moored FOWT system to evaluate the intrinsic characteristics of each design candidates. In the second stage of the design workflow, 1-hr time domain simulations of the entire system were performed to eliminate design candidates that are prone to mooring slack events or any other vulnerable responses. Finally, the most suitable design of the mooring system was selected based on 3-hr simulations for the environmental conditions of 50-year return period. In the present study, design of a mooring system for the University of Maine VolturnUS-S reference platform supporting the International Energy Agency 15-MW reference wind turbine was chosen as the case study to demonstrate the proposed design procedure. The initial design matrix consists of two mooring patterns, four mooring chain diameters, and five mooring line lengths. The simulated results showed that the proposed procedure can be used as a guideline to quickly narrow down to a smaller group of feasible designs. The design process will also contribute to form the basis to develop a semi-automated mooring design tool in the future.