Numerical and experimental study of the seakeeping performance for a novel fish farming vessel considering nets

To improve the economic feasibility of offshore aquaculture, this study proposes a novel concept of fish farming vessel which is retrofitted by an old bulk carrier. Large open farming tanks has been created by replacing the side hull plates with rigid metal nets and retaining the transverse bulkhead. The seakeeping performance of the vessel is evaluated through numerical simulations which are validated against experimental results. A numerical model based on the potential flow based boundary element method is developed using panel elements for the hull and dipole elements for the nets. The effects of net solidity ratio and wave slope variation on seakeeping performance are analyzed. Results show that increasing solidity ratio leads to higher peaks near the natural frequencies in the Response Amplitude Operators (RAOs). Besides, the installation of net generally reduces RAOs due to wave energy dissipation through nets and decreased wave excitation. Comparisons with experimental results from free decay, regular waves, and white noise waves tests demonstrate good agreement in terms of natural frequencies and trends of RAOs. Discrepancies in natural frequencies, especially in pitch motion, are attributed to the underestimation of added mass in the numerical model. The findings validate the feasibility of using dipole elements to represent net structures and underscore the importance of accounting for wave slope in seakeeping analysis of net-integrated offshore structures.