• Ocean Systems Engineering
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• v.14 no.3
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• pp.211-235
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• 2024

Th COP28 has emphasized the governments to speed up the transition away from fossil fuels to renewables such as wind and solar power in their next round of climate commitments. The steady and less turbulent wind over the ocean draws increased attention of governments, industries and researchers on exploring advanced technologies to extract energy from offshore wind. The present study numerically investigates the hydrodynamic behavior of a SPAR-type Floating Offshore Wind Turbine (FOWT) under various wave conditions and mooring line configurations. One of the major focuses of this study is investigating a freak wave's impact on a FOWT and determining its extreme responses. The study investigates the structural response under various wave impact for different configurations of mooring lines. The present study examines the wave-structure interaction under regular and freak wave conditions using numerical modelling approach. During the study, it is ensured that the natural frequency and wave induced motions of SPAR are inline with the experimental studies; thereby increasing the confidence in using the numerical model and domain for this investigation. The study considers the behaviour of slack and taut mooring arrangements under these wave conditions. The study observed that a taut mooring configuration can be efficient in restraining the FOWT motions, especially under a freak wave scenario. The Froude-Krylov force shows a non-linearity due to the non-uniform profile of the platform under all wave conditions. Overall, the study contributes to determining the performance of the mooring configurations under different wave conditions.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.4
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• pp.286-303
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• 2002

Korea Ocean Research and Development Institute (KORDI) has attempted moored current measurements since 1978. This note describes mooring types and failures of moorings deployed in coastal and continental shelf regions around Korea. Taut-wire U-type mooring lines and trawl-resistant bottom mounts have been mainly used in shallow seas. In order to avoid the failure of moorings in the shallow seas, it is needed to (1) design a proper mooring plan considering local mooring environments including fishing activities and (2) use adequate mooring equipments and parts considering mooring period, depth, and other factors that could affect the mooring unexpectedly.

• Ocean Systems Engineering
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• v.14 no.2
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• pp.171-210
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• 2024

This paper focuses on the rigorous and holistic fatigue analysis of mooring chains for a deep draft semi-submersible platform in the challenging environment of the central Gulf of Mexico (GoM). Known for severe hurricanes and strong loop/eddy currents, this region significantly impacts offshore structures and their mooring systems, necessitating robust designs capable of withstanding extreme wind, wave and current conditions. Wave scatter and current bin diagrams are utilized to assess the probabilistic distribution of waves and currents, crucial for calculating mooring chain fatigue. The study evaluates the effects of Vortex Induced Motion (VIM), Out-of-Plane-Bending (OPB), and In-Plane-Bending (IPB) on mooring fatigue, alongside extreme single events such as 100-year hurricanes and loop/eddy currents including ramp-up and ramp-down phases, to ensure resilient mooring design. A detailed case study of a deep draft semi-submersible platform with 16 semi-taut moorings in 2,500 meters of water depth in the central GoM provides insights into the relative contributions of wave scatter diagram, VIMs from current bin diagram, the combined stresses of OPB/IPB/TT and extreme single events. By comparing these factors, the study aims to enhance understanding and optimize mooring system design for safety, reliability, and cost-effectiveness in offshore operations within the central GoM. The paper addresses a research gap by proposing a holistic approach that integrates findings from various contributions to advance current practices in mooring design. It presents a comprehensive framework for fatigue analysis and design optimization of mooring systems in the central GoM, emphasizing the critical importance of considering environmental conditions, OPB/IPB moments, and extreme single events to ensure the safety and reliability of mooring systems for offshore platforms.