Influence of floating ice on water entry cavity evolution and impact load characteristics of a vehicle

Floating ice is extensively distributed in polar regions and exerts a substantial influence on the water entry process of underwater vehicles. This study numerically investigates the cavity evolution and impact load characteristics of a revolved-body vehicle during vertical water entry conditions, for scenarios where floating ice is present. A coupled computational fluid dynamic (CFD) and finite element method (FEM) framework is adopted for the simulations. Idealized disc-shaped floating ice with fixed thickness is used, and ice fracture is not considered in the simulations. Three key parameters are considered: the relative position between the vehicle and the ice ( L p , lateral offset between their centres), the number of floating ice pieces (N, number of simulated floating-ice fragments), and the gap distance under non-collision conditions (no direct vehicle-ice contact). The numerical method is validated against experimental data. The results indicate that when L p < 1, the cavity undergoes secondary expansion induced by collision with floating ice, thereby delaying cavity closure. Within the investigated parameter range, the highest impact pressure peak occurs at the minimum studied relative-position value L p = 0.25, where the peak impact pressure is 30.9% higher than that in the non-collision case. An increase in the number of ice fragments promotes cavity expansion while elevating impact loads simultaneously. When N = 4, the peak drag coefficient is more than twice that under ice-free conditions. As L p rises to 2, floating ice no longer affects the water entry process. These findings provide a reference for the design and safety assessment of polar detection equipment operating in ice-covered waters.