Particle-based numerical simulation of continuous ice-breaking process by an icebreaker

Abstract

The continuous ice-breaking capacity of an icebreaker is an important indicator of its efficiency. The ice resistance encountered by an icebreaker has a significant influence on its continuous ice-breaking capacity. In this study, we develop a numerical model based on the moving particle semi-implicit (MPS) method, which is a particle method based on continuum mechanics, for predicting the ice resistance encountered by icebreakers during continuous ice-breaking operations. Before fracture, the ice is assumed to be a linear elastic material, and the maximum tensile stress theory is used as the fracture criterion. A scalar function composed of the first principal stress gradient and the first eigenvector of the stress tensor is introduced to express the relative positions of the new crack and corresponding particle pair. As the hull is represented by polygons and the ice fragments are represented by particles, the collision points between the hull and the ice, i.e., between polygons and particles, is determined using a novel search algorithm that expands a cell linked-list algorithm. The collisions between individual ice fragments and between the hull and an ice fragment are considered using a particle-based model that is a modified form of the Hertz contact model. The proposed algorithm was verified using experimental data obtained from three-point bending tests on model and freshwater ice specimens that were performed by the Korea Research Institute of Ships and Ocean Engineering (KRISO) and Korea Maritime and Ocean University (KMOU), respectively. The verification process revealed that the closer the properties of the ice to the linear elastic properties assumed in the numerical model, the higher the accuracy of the proposed algorithm. The verified algorithm was used to predict the ice resistance encountered by a model icebreaker during a continuous ice-breaking process. A series of convergence and parametric tests were performed for the main parameters of the continuous ice-breaking simulation, and the experimental results obtained by KRISO were used for comparison. The maximum relative errors from experiment were approximately 12% and 30% under free (Fr) and semi-fixed (SF) side boundary conditions, respectively. The proposed numerical algorithm can successfully predict the ice resistance encountered by an icebreaker and the occurrence of near- and far-field fractures during a continuous ice-breaking process.