Wave-induced motions of and loads on a moored and articulated multibody offshore structure are numerically analyzed, where a coupled mooring-joint-viscous flow solver was used to account for mooring dynamics, joint restrictions, nonlinear rigid body motions, and viscous flow effects. The considered concepts consisted of two MFSs connected by two types of connections, namely a rigid joint and a flexible joint, and positioned by four symmetrical catenary mooring lines. The analyzed responses comprised multibody motions as well as associated forces acting in the hinged joints and the mooring lines. Results indicated that surge motions of the articulated bodies were almost identical to each other, whereas the effects of the joint on heave motions were not pronounced. However, highly dynamic pitch motions between two hinged MFSs were observed. Apart from motion responses, forces acting on the hinged joint and the mooring lines were estimated. The coupled mooring-joint-viscous flow solver demonstrated its capability to predict wave-induced motions of and loads on a moored multibody offshore structure articulated by various types of joints.

Vortex-induced vibration (VIV) of bluff bodies is one type of flow-induced vibration phenomenon, and the possibility of using it to harvest hydrokinetic energy from marine currents has recently been revealed. To develop an optimal harvester, various parameters such as mass ratio, structural stiffness, and inflow velocity need to be explored, resulting in a large number of test cases. This study primarily aims to examine the validity of a parameter optimization approach to maximize the energy capture efficiency using VIV. The Box–Behnken design response-surface method (RSM-BBD) applied in the present study, for an optimization purpose, allows for us to efficiently explore these parameters, consequently reducing the number of experiments. The proper combinations of these operating variables were then identified in this regard. Within this algorithm, the spring stiffness, the reduced velocity, and the vibrator diameter are set as level factors. Correspondingly, the energy conversion efficiency was taken as the observed value of the target. The predicted results were validated by comparing the optimized parameters to values collected from the literature, as well as to our simulations using a computational-fluid dynamics (CFD) model. Generally, the optimal operating conditions predicted using the response-surface method agreed well with those simulated using our CFD model. The number of experiments was successfully reduced somewhat, and the operating conditions that lead to the highest efficiency of energy harvesting using VIV were determined.

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There are no specific codes or rules for designing a new truss-floating tank aquaculture vessel developed in recent years. Moreover, relevant rules for ships and offshore structures are usually referred to in different design stages. However, the floating way and the structure of the truss-floating tank aquaculture vessel are different from those of any ship or offshore platform. According to the code of ship or ocean engineering, there will be significant errors in the design. Firstly, loads of vessels at different sea conditions are calculated using SESAM software. The stresses of the truss-floating tank aquaculture vessel are numerically simulated in accordance with the maximum loads. Furthermore, the global longitudinal strength can be evaluated. The sensitivity of the vessel’s strength to wave parameters is analysed. The research results can provide a valuable reference for designing a truss-floating tank aquaculture vessel.