Numerical investigation on hydrodynamic responses of a rotatable aquaculture cage under correlated wind-wave-current loads

To address persistent challenges in aquaculture systems , particularly biofouling-induced reductions in water exchange efficiency and net structural degradation, this study introduces an innovative horizontally rotatable cage design. The proposed configuration incorporates bilateral airbag modules mounted on cage pressure rings, engineered to generate controlled asymmetric torque for facilitating autonomous cage rotation. The study employed a nonlinear finite element method combined with the Morison equation and the Screen model to analyze the hydrodynamic response of the cage under the combined effects of wind, waves, and currents. The numerical model's reliability was rigorously validated through benchmarking against experimental hydrodynamic data from conventional gravity cage systems. Comparative analyses revealed that under a wave height of 1.25 m, the vertical displacement of the cage at a wave period of 3.2 s was 23 % less than that at a wave period of 7.5 s, while the anchor chain tension increased by 37.5 %. Under extreme sea conditions, the axial force of the center lever was maximized when the wave direction was 0°, enhancing the cage's self-rotation effect. When the wave direction was 90°, the displacement amplitude was maximized, but the figure-eight mooring system was still able to maintain the stability of the cage. • A new rotatable aquaculture cage is designed. It uses airbags to enable self-rotation and reducing the net biofouling. • The rotational performances of the aquaculture cage are verified through theoretical model and hydrodynamic test. • The hydrodynamic responses under correlated wind-wave-current loads are analyzed using nonlinear finite element methods.