Numerical investigation on motion responses of high-speed self-propelled submersible subject to internal solitary wave

Internal solitary waves (ISWs) pose a significant threat to underwater submersibles. Unlike low-speed submersibles in the ISW field, the high-speed submersibles form a large pitching angle, which is more dangerous for submersible maneuverability. However, the mechanisms behind the interaction between ISWs and high-speed submersibles still remain unexplored. In this work, the three-dimensional numerical model for ISW–structure interaction is used to investigate the motion response characteristics of high-speed submersibles in the ISW field. Based on the extended Korteweg–de Vries (eKdV) theory, the ISW is generated in a two-layer numerical tank by enforcing velocity inlet boundaries. The ISW evolution is obtained by solving the Navier–Stokes equations. The motion of the self-propelled submersible is simulated by solving the equation of motion of the submersible. Using this model, numerical investigation on the ISW and high-speed submersible interaction is performed. The effects of submersible depth, self-recovery stiffness, and ISW amplitude on the motion response of the high-speed submersible are analyzed systematically. When the initial position of the submersible is above the ISW trough and the initial depth is close to the trough depth, the submersible may pierce through the ISW surface, which further results in the formation of a large pitching angle, motion stall and “falling deep.” It is difficult for the submersibles with the low recovery stiffness to maintain or control the navigation trajectory. They would undergo the large pitching angle and even impact on the seabed.