Objective This study aims to investigate the multi-body hydrodynamic interaction mechanisms during offshore lifting operations of aquaculture net cages in wind-fishery integration systems. By integrating numerical simulations and dynamic analysis methods, this study systematically investigates the coupled dynamic response characteristics during the cage-carrier vessel separation process to reveal its dynamic evolution patterns and key influence mechanisms.
Method Based on potential flow theory, a fully coupled dynamic analysis model of crane vessel-net cage-semi-submersible barge was established for a marine ranch project in Guangdong. The complete lifting process was dynamically simulated using SESAM software. Five typical operating sea states were configured to investigate the influence of wave parameters on the system's motion response under combined wave-current-wind actions.
Result The results demonstrate that wave period dominates the system stability. Under short-period conditions, the system maintains stable motion with relatively small horizontal relative displacements, while long-period conditions excite low-frequency resonance, leading to significant slow-drift motions. Vertical response analysis reveals that long-period waves cause severe relative displacement fluctuations between the cage and semi-submersible vessel, with actual displacement amplitudes doubling the preset safety target of 2.045 m. Quantitative analysis further indicates that when significant wave height increases from 1.0 m to 1.5 m, the actual displacement amplitude increases by approximately 20% relative to the target displacement of 2.045 m, demonstrating that its influence is significantly weaker than the displacement variations induced by wave period changes. The complete dynamic simulation successfully captures the continuous dynamic response characteristics during the lifting process.
Conclusion This research clarifies the influence mechanisms of wave parameters on the cage lifting process, identifying wave period as the crucial factor for operational safety. An operation window assessment method incorporating multi-body coupling effects is established, proposing a safety criterion with peak period not exceeding six seconds as the core requirement. The findings provide theoretical foundation for safe installation of marine ranch net cages and offer valuable references for similar offshore lifting operations.
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