Numerical investigation on the interaction between internal solitary wave and self-propelled submersible

Abstract

Internal solitary waves (ISWs) often seriously threaten the survivability of the underwater submersible. Most of the existing investigations focus on the interaction between ISWs and fixed or suspended submersibles. However, the investigation on the interaction between ISWs and self-propelled submersibles is still scarce, which is a more realistic case in the marine engineering. In this paper, a three-dimensional numerical model for the interaction between ISW and self-propelled submersible is developed. Based on the extended Korteweg–de Vries (eKdV) theory, the ISW is generated in a two-layer fluid numerical wave tank by solving the Navier–Stokes (N–S) equation. By introducing the hydrodynamic loadings provided by the ISW environment into the standard operation equation of the submersible, the six degrees-of-freedom motions of the submersible can be obtained. The dynamic overset mesh technology is adopted to simulate the motions of the self-propelled submersible in the ISW fluid field. The present numerical model is validated by comparing with the experiment on a submerged cylinder in the ISW environment. Using this numerical model, we compare the interaction effects of the fixed, suspended, or the self-propelled submersible in ISW and discuss the influences of propulsive forces of the self-propelled submersible on ISW–structure interaction effects. The numerical results show that the loadings and movements of the submersible change remarkably in the surge, heave, and pitch direction. Especially, the submersible with high propulsive forces can pierce the wave surface and reach a large pitch angle with the amplitude of 36°, which further results in a 35% motion speed decrease in the initial propulsion direction.