Investigation on dynamic performance of semi-submersible aquaculture platform in two mooring forms

The mooring system, as a crucial component of aquaculture platform, plays a pivotal role in limiting overall motion of aquaculture platform. In the present study, a combined approach utilizing potential flow theory and the Morison equation is employed to investigate the impact of regular waves on the dynamic response of a semisubmersible aquaculture platform in linear elastic mooring and nonlinear catenary mooring. In terms of linear elastic mooring, the aquaculture platform experiences intense dynamic responses at wave frequencies between 0.25 Hz and 0.30 Hz. For nonlinear catenary mooring, the maximum mooring forces, heave, and pitch motions appear between 0.30 Hz and 0.45 Hz, with the maximum surge motion occurring at 0.1 Hz. It is evident that the wave frequencies corresponding to the maximum dynamic responses in nonlinear catenary mooring conditions are higher than those in linear elastic conditions, except for surge motion. Furthermore, the mooring forces and pitch motion in linear elastic mooring conditions are significantly higher than those in nonlinear catenary mooring conditions, while the differences in maximum surge motion and heave motion are minimal. Therefore, nonlinear catenary mooring forms are preferred for overall platform stability in the design of mooring systems of practical marine aquaculture platforms. However, given the different wave frequency ranges associated with the maximum dynamic responses in the two mooring forms, the selection of mooring forms should also consider the prevalent wave frequency range in the actual marine environment.