Nonlinear dynamic response characteristics of a cube net cage integrated in a jacket foundation at various submerged...

With marine aquaculture and offshore wind development expanding toward deep and far offshore areas, multifunctional integrated structures attract increasing attention. This study investigates the hydrodynamic response of a suspended net cage supported by a jacket foundation under combined wave-current conditions, focusing on cage motions, cable tensions, and nonlinear behavior at different submerged depths. A flexible numerical model based on the lumped-mass method is developed and validated by physical model tests. Five submerged depths are considered: 0 m and 20%, 40%, 60%, and 80% of the cage depth. Results show that submerged depth strongly affects the critical instability current velocity and cage motion state. Greater submerged depth improves resistance to instability. The cage motion exhibits a three-stage evolution characterized by "no contact-contact-overturning", and the motion and nonlinear response of the bottom marker points vary significantly at different stages. The leeward cable also shows abrupt tension changes during instability due to bottom ring-jacket interaction.