Numerical Study of HDPE Unmanned Surface Vehicle Resistance in Discrete Floe Ice

Discrete floe ice increases the propulsion resistance of small unmanned surface vehicles (USVs) and generates impulsive bow and side loads. For high-density polyethylene (HDPE) USVs, these loads govern propulsion demand and provide inputs for structural assessment. Existing studies address floe-ice resistance of conventional ships and HDPE material behaviour separately. Using the geometry of an HDPE USV, this study combined the Reynolds-averaged Navier–Stokes (RANS) equations, volume-of-fluid (VOF) method, and discrete element method (DEM). The model computed open-water resistance and longitudinal loads under varying speed, ice concentration, and ice thickness. The numerical method was assessed against KRISO Container Ship (KCS) experiments in open water and floe ice. Open-water resistance increased from 49.2 to 230.7 N between 2 and 4 kn. At a 60% ice concentration and 0.02 m ice thickness, the mean total load increased from 125.6 to 428.9 N over this range. Increasing speed raised both fluid resistance and contact force, whereas higher concentration and thickness primarily increased contact force; the peak load reached 929.2 N at 0.04 m thickness. These fixed-attitude predictions provide comparative load estimates for propulsion assessment and subsequent structural analysis of the HDPE USV.