Experimental Testing and Calibrated Mechanical-Hydrodynamic Modelling of Net for a Modular Fish Pen

Abstract This study presents a calibrated net model for accurately analyzing a lightweight modular fish pen. The fish pen utilizes a commercial PET monofilament net, known for its high strength and antifouling properties. The mechanical properties of the net are examined through physical testing. Owing to its orthotropic behavior, in-plane tensile tests were conducted in two orthogonal directions, while out-of-plane properties were assessed using a central patch load with deformation measurements at multiple points. Additionally, out-of-plane tests were performed on the net with localized damage to evaluate strength reduction due to wear and tear. Results indicate that the net’s tensile modulus in the longitudinal direction is 5 to 15 times greater than in the transverse direction, with a breaking force approximately four times higher. The out-of-plane test indicates a breaking force of 14.1kN for the unabraded net, while the abraded net experienced a 72% reduction in strength. The experimental test results were used to model the net within the commercial software AquaSim. The findings highlight that for planar nets restrained on all edges, a nonlinear deformation model calibrated by experimental results is essential; otherwise, deformation predictions will be significantly inaccurate.