NUMERICAL SIMULATION AND PREDICTIVE MODELING OF HYDRODYNAMIC LOADS ON A UUV IN BROKEN-ICE CONDITIONS

Unmanned underwater vehicles (UUVs) operating in marginal ice zones are affected by broken ice. Conventional dynamic models have difficulty accurately describing the complex interactions among the vehicle, the surrounding flow field, and broken ice. It is therefore necessary to investigate the forces associated with broken ice, clarify how these loads develop, and establish an efficient method for predicting them. In this study, a numerical model for calculating the forces acting on an underwater vehicle in a marginal ice zone is developed using a coupled computational fluid dynamics-discrete element method (CFD-DEM). The model is validated against experimental measurements of the ice resistance of a container ship model. Under three ice concentration conditions, the relative errors between the numerical and experimental results range from 4.79% to 8.49%. Representative conditions with different vehicle speeds, submergence depths, and broken-ice concentrations are then considered. The time-domain responses of the forces and moments acting on the vehicle are analyzed to identify their characteristics and how they vary under these conditions. On this basis, a predictive model for the forces associated with broken ice is established that accounts for the effects of multiple factors. Analytical expressions suitable for engineering calculations are also obtained, enabling a transition from high-fidelity numerical simulation to rapid load prediction. The results show that the forces associated with broken ice exhibit pronounced random fluctuations. Their amplitudes tend to decrease with increasing submergence depth, and this decrease is more pronounced at higher vehicle speeds. At the same submergence depth, the force amplitudes increase nonlinearly with the Froude number, with a sharper increase at smaller submergence depths. As broken-ice concentration increases, the load amplitudes and moments exhibit an overall, but non-monotonic, increasing trend. These findings provide a theoretical basis and supporting data for dynamic modeling, motion control, and safe navigation planning for underwater vehicles operating in marginal ice zones.