Numerical Simulation of Rectangle Ice Floes Movement Using a Distributed Mass/Discrete Floe Model

Abstract

A new model, named “Distributed Mass/Discrete Floe model” is proposed for numerical simulation of short term and narrow area pack ice movement. This model possesses the advantages of both the continuum and the discrete element ones: it can express the discrete nature of pack ice which is difficult for a continuum model to treat, and it can realize much shorter computation time than a discrete element model. The pack ice is divided into ice floe bunches in which the floes, assumed to be distributed uniformly, are modeled as inelastic rectangles floating on the water. The ice interaction forces are formulated from the relation between the impulse on the bunch and the variation of the bunch momentum. The ocean flow is calculated by a multi-layer model simultaneously with the ice floe movement. The model formulation and the improvement of the computation accuracy are described in detail.The computations were made for simplified ocean conditions driven by a uniform wind field in the marginal ice zones between the coast and offshore. The results showed some characteristics of ice and water combined flow and force acting on an ocean structure, as follows;1. The water surface velocity distribution is distorted by the difference in the shear stress between the water/ice interface and the water/air interface. This causes the diffusion of pack ice.3. In the case of no major current for a deep ocean, the water surface velocity can be determined from the computation only for a scale of the Ekman layer. If the water depth is less than the scale of Ekman layer, the direction of water surface flow, which is essential for the ice flow calculation, is highly affected by the water depth.3. Many spike-like peaks appeard in the time variation of ice load on an ocean structure. This is caused by the discrete nature of the present model. Also, the results showed the rational movement of pack ice around the structure.