A Discrete Element Model for Brash Ice Simulations

Most merchant ships operating in the cold regions are not able to break ice themselves, they can only navigate in the broken ice, the so-called brash ice channels. Today’s standard requires a model test in real brash ice conditions to be carried out and realistic additional resistances to be estimated from this. The problem is that they can only be performed at the end of the design process. The possibility of changing the ship design within the development process can only be guaranteed by using a simulation tool, based on the Discrete Element Method. The problem with the development of this numerical simulation is the correctness of the mapping of the physical behaviour of brash ice. The physical models used are often simplified and not sufficient to represent the complex mechanical behaviour of brash ice. Thus, another problem with the use of numerical simulation is the selection of the correct parameters to describe the mechanical behaviour. A concrete definition of the used material parameters does not exist and the experimental tests for the determination of the physical properties are often complex and not standardized. This paper examines the mechanical behaviour of brash ice and the descriptive parameters of each ice rubble. On this basis, the physical behaviour in nature is compared with the model used in numerical simulation. As a result, physical inconsistencies are determined and new solution approaches are proposed, for example in the form of a new contact model, an extension of the friction model or a change of the descriptive particle shape.