Numerical analysis of safety and stability of rotatable horizontal aquaculture cages

To reduce the overturning risk under extreme sea conditions, this study employs a numerical method to study and optimize the safety performance of a novel rotatable horizontal aquaculture cage (RHAC) system. The impact of buoyancy volumes on the net cage movements is analyzed using AQWA simulations and a tank experiment, indicating that the cage structure possesses a self-rotation capability under external forces. The cage rotation directions and velocities are controlled by adjusting the inflation state of the floating bodies, thereby flipping the fouled underside of the net upside down for subsequent cleaning. The effects of wave height, wind speed, and the arrangement of floating bodies on the dynamic behavior of the cage are analyzed systematically. Results show that the “single circular ring with 8 floating bodies” configuration offers superior stability, reducing approximate 75 % pitch amplitude compared with cages without floating bodies, and shows a decrease of about 4 % in longitudinal pitch angle compared with the other three configurations. Additionally, the six-degree-of-freedom motions are assessed under the four typical mooring failure states. Results show that chain breakage on one side leads to the most severe responses, inducing 90° yaw, doubling vertical heave, and 8-time longitudinal surge.