Yun-Il Chu

Offshore aquaculture is gaining traction due to space limitations in nearshore waters, more pristine water, cooler temperatures, and better waste dispersal. This move has spurred the development of new technologies for offshore aquaculture. Despite the numerous analysis methods for designing aquaculture infrastructure, limitations and challenges remain in modeling the influence of fish cages on flow fields and in addressing fluid–structure interaction. This paper presents a comprehensive review of analysis methods and modeling techniques applied in the design of offshore aquaculture systems, emphasizing the structural reliability analysis. This review includes statistical and predictive analysis of extreme sea conditions, evaluation of environmental loads and hydrodynamic analysis, structural reliability modeling and assessment, and seabed geotechnical responses to mooring anchors. For each design consideration, the relevant theories and applicability are elaborated upon and discussed. This review provides valuable insights for engineers involved in the development and design of offshore aquaculture infrastructure.

Moving offshore for fish farming poses challenges due to the more energetic sea environment. In this paper, a novel offshore fish pen design named SeaFisher has been proposed. The SeaFisher comprises modular cubic pens that are assembled to form a large 2 × n array offshore fish pen. Its frame structure is made from HDPE, making it flexible and durable against the harsh sea environment. Specially tailored connection brackets and connector pods are designed to assemble bundles of HDPE pipes forming the SeaFisher structure. The SeaFisher is moored using a single point mooring to minimize environmental and collision loads, and for improved waste dispersal. More importantly, the SeaFisher possesses ballast tubes positioned on the top surface to allow it to submerge to a desired water depth to dodge the strong surface waves during severe weather events. This paper presents the engineering design details and hydroelastic analysis of the SeaFisher. Based on a hydrostatic analysis, suitable materials were chosen for the various components of the SeaFisher, and the components were appropriately sized up. By using the software AquaSim v.2.17.3, the SeaFisher’s hydroelastic responses under different sea-state conditions were investigated. It is found that the designed SeaFisher structure and mooring system are adequate with respect to strength and stiffness for the considered sea-state conditions of up to 8 m significant wave height and 0.8 m/s current speed. It is expected that the SeaFisher will be a game changer for offshore fish farming due to its cost-effectiveness and ability to survive in severe storms.

While moving fish farms to offshore sites can be a more sustainable way to expand farmed fish production, the fish pens have to contend with a harsher environment. Thus, it is necessary to draw on offshore engineering competences for designing and analysing the offshore fish farming infrastructure. This paper reviews existing design and analysis guidance from maritime classification and national/international authorities that can be applicable for offshore fish farms. Based on the existing design guidelines, a review of design criteria for offshore fish farms under the following subtopics is provided: design life, design environmental loads, combining environmental loads, and miscellaneous load conditions. This review on the global performance analysis procedures and methods is presented based on practices used for neighbouring industries, such as offshore oil and gas and wind energy production, under the following subtopics: hydrostatic analysis, hydrodynamic analysis, and mooring system analysis with introducing theoretical background and modelling techniques. This paper also highlights limitations and cautions when using these design and analysis methods. Providing this comprehensive information, as well as commentary on their applications, will help engineers and designers to develop offshore fish farming infrastructure with confidence.

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