Fast prediction of underwater vehicle motion under internal solitary waves

To address the difficulty of achieving rapid motion prediction for underwater vehicles under internal solitary waves (ISWs) disturbances using conventional experimental and high-fidelity numerical approaches, this study proposes a fast prediction method by coupling the vertical plane motion equations of an underwater vehicle with an internal wave force prediction model. The goal is to achieve rapid prediction of the motion response of the navigation vehicle in an internal wave disturbance environment. Based on this method, motion responses under small-amplitude and large-amplitude ISWs were simulated and validated against high-precision CFD (computational fluid dynamics) results. For small-amplitude ISWs, the linear motion equations yield superior prediction accuracy in trajectory, attitude, and velocity. For large-amplitude ISWs, linear equations perform better in trajectory and early-stage pitch prediction, whereas nonlinear equations provide improved accuracy in late-stage pitch motion and vertical velocity prediction. The results demonstrate that the proposed method is particularly suitable for real-time prediction under small-amplitude ISW conditions, while further improvement is required for large-amplitude and highly nonlinear motion scenarios. This work provides an efficient tool for rapid motion prediction of underwater vehicles in ISW environments and supports operational safety in internal wave-affected regions.