Mooring System Failure Detection Methods for Floating Offshore Wind Turbines Using Motion Measurement: Part 2 Numerical Simulation for Impact Assessment of Multiple Factors

Abstract For the large-scale deployment of floating offshore wind turbines (FOWTs), the establishment of appropriate inspection methods is required. There are concerns that the current inspection technologies and rules are costly while failing to sufficiently reduce mooring risks, making the development of new inspection and monitoring technologies a critical issue. The goal of this study is to develop a method for assessing the integrity of the mooring system in FOWTs by measuring floater motions. As an initial investigation, we propose a method to detect mooring line failures based on the floater motions. This approach utilizes environmental data to define an expected range of floater positions, which is then directly compared to the floater’s current position to detect any potential failures in the mooring system. Since this method is considered applicable to various kinds of FOWTs, it is necessary to individually evaluate the impact of multiple factors that determine the expected range of floater positions. Key factors include the types of external loads, mooring method, mooring configuration, and anticipated failure conditions. In this paper, we present an overview of the mooring system failure detection method and validate the existing numerical analysis method by comparing with the tank tests results using a 1/100 scaled FOWT model with two types of catenary mooring. Then, using the numerical analysis methods, an impact analysis of multiple factors is conducted. The main objective of this analysis is to clarify the effects of tidal current loads and the impact of changing the number of mooring lines on the expected range of floater positions. Our findings show that the tidal current loads could significantly affect the floater motion and that increasing the number of mooring lines reduces the floater displacement.