Objectives With the increasing demand for polar navigation and polar ship design, the influence of bow geometry on ice-going performance has received growing attention. Since the ice-clearing process is closely associated with broken-ice motion near the bow, this study investigates the influence of key bow geometric parameters on the ice-clearing resistance of a heavy icebreaker with a straight stempost.

Methods A numerical simulation model is developed by combining the circumferential crack method and the non-smooth discrete element method to describe the interaction among the ship, level ice, and broken ice. The circumferential crack method is used to simulate the failure of level ice and the generation of broken ice pieces during the icebreaking stage, while the non-smooth discrete element method is adopted to calculate the subsequent motion, collision, and contact loads of broken ice during the ice-clearing stage. In the model, broken ice is treated as rigid bodies, and the effects of gravity, buoyancy, hydrodynamic forces, and collision forces are considered. Towing simulations are then carried out under typical level-ice conditions. To conduct the parametric analysis, a fully parametric modeling method is applied to a U.S. Coast Guard heavy icebreaker selected as the parent ship. The bow geometry is reconstructed through characteristic curves and surface-generation techniques, with the stem angle and waterline entrance angle taken as independent parameters. On this basis, a series of hull forms with different bow geometric features is generated, and the effects of these parameters on the ice-clearing resistance of the heavy icebreaker with a straight stempost are systematically analyzed.

Results The numerical results under towing conditions are compared with model-test data, and the error is less than 10%, which verifies the reliability of the proposed numerical model. The simulation also reproduces the main characteristics of broken-ice motion around the hull. Level ice first fails near the stem and shoulder regions, and the generated broken ice pieces then rotate, slide along the bow and side hull, and are finally discharged toward both sides or the stern. The parametric results show that the stem angle has a significant influence on ice-clearing resistance. With the increase in stem angle, the ice-clearing resistance generally presents a nonlinear increasing trend. This is mainly because a larger stem angle increases the rotation angle of broken ice near the waterline and enlarges the longitudinal component of the normal collision force acting on the bow. However, when both the stem angle and waterline entrance angle are relatively small, the resistance may show a slight decreasing tendency with increasing stem angle. The influence of the waterline entrance angle is more complex and is closely related to the form of the fore waterline. To further describe the bow waterline form, the waterline fullness within the first quarter breadth is introduced. As the fullness increases, the waterline gradually changes from a straight form to a slightly convex form and then to a convex form, while the ice-clearing resistance first decreases, then increases, and finally decreases again. Furthermore, a coefficient k is introduced to comprehensively reflect the influence of the stem angle and waterline shape. With the increase in k, the ice-clearing resistance first decreases slightly and then increases gradually.

Conclusions The results indicate that the ice-clearing resistance of a heavy icebreaker with a straight stempost is strongly affected by bow geometric parameters, and the influence is nonlinear. The proposed method can effectively describe the relationship between bow-line variation, broken-ice motion, and ice-clearing load. It provides a theoretical basis and a practical numerical tool for assessing ice-clearing capability and optimizing bow lines in polar vessel design.