Experimental and Numerical Evaluation of Fish-School Protection Configurations for a Semi-Submersible Truss Aquaculture Platform Under Severe Regular Waves

Fish–net contact is a practical concern for exposed offshore aquaculture platforms during severe waves, yet it is seldom assessed together with platform hydrodynamics and mooring response. This study compares two protection strategies for a semi-submersible truss aquaculture platform: add-on flow-guiding structures fitted with hoods and side baffles, and a deepened-netting configuration. Tests on a 1:50 physical model under severe regular waves measured fish-school-boundary displacement, platform surge, heave and pitch, and mooring-line tension. The maximum horizontal displacement of the upwave school boundary served as an engineering proxy for the school’s tendency to approach the netting. Frequency-domain ANSYS-AQWA calculations were also used to compare wave excitation, added mass, and radiation damping. The flow-guiding structures generally reduced school-boundary displacement, but they often increased surge and mooring demand, revealing a trade-off between reduced school-boundary approach and station keeping. Under the tested conditions, the deepened-netting configuration reduced school-boundary displacement, platform motion, and mooring tension. Its fish-school response cannot, however, be attributed to netting depth alone because culture volume increased while stocking density decreased. These results provide a joint assessment of fish-school response, platform motion, and mooring load for the proposed configurations. The findings are limited to the tested severe regular waves and require validation under irregular waves, combined waves and currents, and full-scale conditions.