Operational limits for floating-collar fish farms in waves and current, without and with well-boat presence

Dynamic response of a floating circular collar-type fish farm, without and with well-boat presence, in current, regular and irregular waves is analyzed. A modern design well boat and a realistic fish farm (with single cage) are considered. The latter comprises a floating collar, an elastic sinker tube, a flexible-closed net cage and a complex mooring system. The main purpose is to determine the operational conditions for the isolated fish farm and for the well boat-fish farm system. This study involves theoretical development, numerical investigations and analysis of experiments on a realistic fish-farm model (not carried out in this research). A time-domain numerical solver for the fish farm is developed with the different components modeled with the state-of-the-art theoretical and numerical formulations. For instance, the motions of the floating collar and the sinker tube are described by a curved beam equation with consideration of axial stiffness and curvature effects. In terms of the net cage, the net twines are modeled as linear elastic trusses. The hydrodynamic loads on the net cage are estimated by the screen-load model, which accounts for hydrodynamic net-shadow and Reynolds number effects. Proper strategies are suggested to deal with the coupling between the different components and a solution algorithm, with a criterion to prevent unphysical negative net tensions, is proposed. The modeling of the different components is validated by comparing against documented experiments, involving simplifications of the various components. The validated numerical tool is used to analyze a realistic aquaculture fish-farm system (with single cage). The mooring loads obtained from the numerical simulations are compared against available experimental data. Satisfactory agreement is demonstrated both in regular and irregular waves. A sensitivity analysis is also performed to identify important parameters influencing the mooring loads, showing which net cage related parameters are crucial. The operational limits of the fish farm are determined through systematic simulations in regular waves and current, indicating that the net volume reduction is the main constraint preventing the studied fish farm operating in more exposed regions. Theoretical models of a well boat operating at a fish farm in current and in long-crested irregular waves and current are also introduced. The transverse viscous loads on the boat are estimated based on the cross-flow principle and the