At present, open ocean aquafarm should be developed to settle the problems which occur in the inshore aquaculture. Accurate computation of force and deformations on feeder vessel and cages under wave and current loads is a key element when designing mooring systems for fish farms. In the present study, with a new type of coupled feeder vessel and cages system as the object of the research, considering the environmental load and the cages dimension parameters as well as the effect on the performance of the system, the Morison equation, A new Cd determination formulation, on-site test and numerical simulation methods are used, and a safety assessment method for the system design is given under the effect of mooring tension and cage volume deformation failure. The main contents are the numerical model is developed by using the commercial software OrcaFlex, the dynamic responds of the vessel are calculated by using ANSYS-AQWA software, first- and second-order wave forces are included in the calculations, Morison equation is used to compute the drag force on line elements representing the net, drag coefficients are determined at every time step in the simulation considering the relative normal velocity between the structural elements and the fluid flow. Based on the numerical model, a simple but effective simulation method is set up to reduce design costs, save concept design time, and avoid the labor of flume tank tests. Finally, a safety evaluation method which is required in the cage system design for aqua-farm has been presented in this paper.
Nowadays, the fish industry is considering moving aquaculture further offshore where water quality and space availability favor production intensification. Growing fish offshore in exposed waters, however, brings a new challenge to the industry. The feeder vessel, cages, mooring systems and auxiliary equipment need to withstand a harsh environment with a full range of loading conditions such as strong waves, currents and storms. In offshore location, a fish farm must be able to operate under minimal human intervention, in higher sea states with stronger mooring (Taeho et al 2013).
