The development and utilization of wave energy, heralded as a potential leading source of clean energy worldwide, have garnered considerable attention from the global research community. Among the diverse array of wave energy converters (WECs), the raft-type WEC stands out for its potential to efficiently harness and utilize wave energy, offering high energy conversion rates and a broad frequency response range. This paper delves into the evaluation of a raft-type WEC’s performance in various mooring configurations under different wave conditions. Our analysis primarily focuses on the dynamics of the two-body WEC using a weakly nonlinear three-dimensional potential flow solver. The considered device comprises two interconnected floating barges, incorporating a power take-off system at the hinged connection point. This investigation involves the use of equivalent linear damping to model the power take-off (PTO) system. To validate the numerical simulations, we conduct physical model experiments with WECs. Additionally, the coupling of the raft-type WEC’s dynamics and its mooring dynamics was examined, highlighting the performance differences between various mooring systems through a comparative analysis.

A truss-floating aquaculture vessel is an innovative addition to the aquaculture industry, characterized by its large, porous, ship-shaped structure. It differs from traditional ships, offshore structures, and individual net cages. Due to its distinctive features, a large-scale truss-floating aquaculture vessel requires dedicated hydrodynamic and structural analysis, which is the primary focus of this paper. Our study starts with the calculation of wave loads acting on the vessel using the equivalent design wave method. Subsequently, it delves into the analysis of structural characteristics and stress distribution of the truss-floating aquaculture vessel, upon which structural optimization is performed. To determine the optimal design variables, a sensitivity analysis of the truss members is carried out using a parametric research method. Finally, the structure with multiple objectives is optimized using two distinct approaches: the adaptive simulated annealing algorithm (ASA) and the multi-island genetic algorithm (MIGA). The results reveal that prior to optimization, there is a risk of buckling and yielding damage occurring at various connections within the vessel structure. After optimization, the structural strength is significantly improved, accompanied by a reduction in the total weight of the vessel. This study offers a valuable reference for the design and structural safety assessment of this innovative truss-floating tank-type aquaculture vessel.

The increasing global need for renewable energy has rendered the development of offshore wind energy extremely significant. In areas where ocean depths exceed 50 meters, conventional permanent foundations become economically unfeasible, becoming floating offshore wind turbines (FOWTs) a superior alternative. Simultaneously, the development of marine resources in offshore areas has failed to meet increasing market demand, necessitating the urgent expansion of aquaculture fisheries into deeper waters. This research developed a fully integrated model of a cage platform, net system, and mooring system, compatible with the NREL 5MW wind turbine. Numerical simulation methods, based on potential flow theory and Morrison’s equation, are utilized to examine the motion response characteristics of the coupled system under various sea conditions. The study results demonstrate that the net, acting as a damping element, significantly decreased the system’s motion response and enhanced its stability. The system’s dynamic response is influenced by wave height and period in both regular and irregular wave circumstances, particularly under extreme sea conditions. Furthermore, the net’s presence minimally affects the wind turbine’s power output while contributing to the mitigation of power fluctuations. The examination of complex environmental circumstances influenced by wind, waves, and currents reveals that a rise in current velocity markedly changes the system’s surge motion trend, although it has little impact on power output. The work establishes a theoretical framework for the design and optimization of deep-sea wind-fishery integrated systems, providing insights into the maximization of marine resource utilization and the commercial deployment of wind energy.

The survivability of raft-type wave energy converters under extreme sea states remains a key challenge for their practical deployment. In this study, focused waves are adopted to represent extreme wave events, and the hydrodynamic responses and load characteristics of a dual-raft wave energy converter are investigated using a validated numerical model. After validation against physical model measurements, which show close agreement in wave elevation and motion responses, the model is used to systematically examine the effects of wave amplitude, peak frequency, and inter-raft spacing on the system dynamics. The results show that a peak frequency of 0.7 Hz induces multibody coupled resonance, leading to the maximum motion responses and hinge forces. A spacing of 0.4 m produces the largest pitch response, while a spacing of 0.3 m results in the maximum hinge load, indicating enhanced relative motion but increased structural demand. Reducing the spacing to 0.2 m results in more stable responses and lower loads, whereas increasing the spacing to 0.6 m weakens motion coupling and increases the static bending moment. The different peak magnitudes of the fore and aft mooring forces at the same spacing further indicate that mooring-load assessment should be performed separately for the two rafts. These findings provide practical guidance for survivability-oriented spacing design and load mitigation of raft-type WECs under extreme wave conditions.