A motion prediction method for damaged ships in waves considering internal flooding flow

To address the high computational costs associated with evaluating ship damage flooding and its motion responses in waves, a fast 6+N degrees of freedom (DOF) time-domain coupled motion simulation method based on three-dimensional potential flow theory and the equivalent lumped mass method is proposed. Validation through comparison with computational fluid dynamics (CFD) numerical simulations and physical model test results indicates that this simplified method can effectively predict the transient heeling and steady-state equilibrium postures of damaged ship in calm water. Under regular beam wave conditions, the method successfully captures the oscillation characteristics of the flooding water volume and the macroscopic response trends such as roll and heave during the early stages of damage flooding. Although the method exhibits certain limitations when dealing with severe shallow-water sloshing caused by damage openings above the waterline due to non-linear viscous dissipation,leading a slight overestimation of the steady-state roll and flooding volume—its overall computational efficiency and accuracy satisfy the practical engineering requirements for the rapid assessment of ship damage stability.