Development and validation of an NDEM-based numerical model for ship maneuverability in level ice

A physics-based numerical model is developed to predict ship maneuverability in level ice by coupling the Non-smooth Discrete Element Method (NDEM) with the Maneuvering Modeling Group (MMG) framework. The model not only accounts for the key ice failure mechanisms of crushing and bending but also explicitly resolves the interaction between broken ice and ship hull. Meanwhile, it also incorporates fully dynamic, two-way coupling between ice-induced loads and ship motions. The model's accuracy in predicting ice forces and ice-induced moments was validated using two experiments: the straight-line motion of a cone-shaped structure and the constant-radius turning maneuver of the icebreaker Terry Fox. Following validation, the model is further applied to full-scale simulations of the USCGC Healy operating in level ice, where maneuvering coefficients are determined through a combination of CFD simulations and empirical methods. Parametric analysis of ice thickness, propeller revolution, and rudder angle reveals a strong dynamic coupling between ship kinematics and ice loads, and shows that propeller and rudder effects are markedly more pronounced in level ice than in calm water.