Hydrodynamic characteristics of a structure passing through ice fields with varying ice particle sizes

The investigation of water entry behavior of structures in floating ice fields is essential for improving the safety and reliability of polar marine equipment deployment. In this study, a two-way coupled computational fluid dynamics-discrete element method framework is employed to simulate the vertical water entry of a structure under ice-free conditions and through fragmented ice fields with identical coverage density but varying particle sizes. The evolution of the cavity, flow field characteristics, ice response, and structural motion are analyzed. Results show that larger ice particles increase the effective inertia near the free surface and delay surface closure, thereby promoting cavity formation. As the free surface contracts, the Venturi effect intensifies, drawing a large volume of air rapidly into the cavity. This sustains and enlarges the cavity tail, thereby giving rise to flow phenomena such as necking, pinch-off, and surface wrinkling. Under a constant ice coverage density, the effect of ice particle size on cavity dimensions exhibits a saturation phenomenon, whereby further increases in particle size do not lead to a significant enlargement of the cavity's maximum cross-sectional dimension. During the water-entry of the structure through the ice field, the ice particles first disperse radially under impact and subsequently contract and converge toward the entry point during surface closure of the cavity, ultimately forming a crown splash. Additionally, the mass of ice impacted during entry governs the early-stage loads and motion characteristics, while subsequent dynamics are dominated by fluid forces.