Study of the response characteristics of a spread moored FPSO in the bidirectional sea state. (15th November 2022)

• Record Type: Journal Article
• Authors: Huang, Yucu; He, Yanping; Liu, Yadong; Qiu, Ming; Li, Mingzhi; Luo, Ziliang; Xu, Jia
• Is Part Of: Ocean engineering. Volume 264(2022)
• Publication Date: 2022-11-15
• Subjects: FPSO -- Spread moored -- Motion response -- Slow drift force -- Bidirectional sea state; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.112453
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: The difference frequency wave drift force may excite large resonant responses for a moored FPSO in horizontal motions, so the moored FPSO responds in both low frequency motion and wave frequency motion generally. In this study, the parameter sensitivity analysis is carried out to investigate the motion response characteristics of a spread moored FPSO in the bidirectional sea state comprised of wind sea and swell. The effects of water depth, loading condition, existence of mooring system, numerical method, sea state type, significant wave height and wave direction on the motion responses are studied in numerical simulation. The research shows that the wave frequency motion responses of FPSO are dominated by swell, and the low frequency motion responses are contributed from both wind sea and swell in the bidirectional sea state. The motion responses are proved to be affected indistinctively by the change of loading condition. The change of water depth affects the motion responses in some degrees. The responses of FPSO in roll can be enlarged by the spread mooring system, and the enlargement becomes more significant if the spread mooring system is arranged in deep water with large pretension force for the mooring lines. Highlights: A validation study is conducted to verify the numerical method of the hydrodynamic calculations for FPSO. The low frequency responses of FPSO in surge and sway increase remarkably with the decrease of water depth. The existence of spread mooring system affects the motion responses of FPSO in roll, especially in deep water. The wave frequency motion responses are dominated by swell while the low frequency ones are contributed from wind sea and swell. The horizontal motions are resulted from the coupling of low frequency drift motions and wave frequency oscillations.