A floe-resolved multi-velocity-field material point method for ship–ice interaction, resistance prediction, and collision mechanism analysis in fragmented ice fields

To describe independent floe motion, ship–ice contact, floe–floe interaction, local accumulation, and unsteady resistance in fragmented ice, this study develops a floe-resolved multi-velocity-field material point method. Individual floes are assigned persistent identities, and a floe-separated grid-transfer scheme is introduced to reduce nonphysical momentum mixing through the shared background grid. Convex-prismatic contact proxies, axis-aligned bounding box (AABB) and spatial-hash broad-phase screening, Gilbert–Johnson–Keerthi (GJK) and expanding polytope algorithm (EPA) narrow-phase detection, and impulse-based contact correction are combined to resolve floe interactions. Comparison with published KRISO Container Ship (KCS) model tests shows that, under the investigated model-scale conditions, the simulations reproduce representative floe accumulation, sliding, rotation, localized overturning, and lateral clearing, while capturing the overall increase in mean resistance with ship speed and ice concentration. Higher ice concentration is associated with stronger accumulation and higher resistance, whereas increasing ship speed enhances momentum exchange and transient fluctuations. Contact-network analysis further shows that high-resistance stages generally coincide with larger connected floe groups, extended contact chains, and increased bow-region ice content. The framework provides a unified basis for fragmented-ice resistance analysis and floe-scale interaction interpretation.