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Model experiments on the transient response of a floating ice sheet to an advancing icebreaker were carried out in two dimensions in order to provide information on the actual icebreaking phenomenon associated with ships advancing in level ice. The response consists of two parts:the dynamic bending of the ice sheet to flexural failure; andthe rotation of the broken ice slab until the slab is parallel to the bow plate of the advancing vessel. A theoretical approach to calculate the transient response of the floating ice sheet is presented. The theory is based on the assumption of potential flow with a relatively complicated boundary condition on the ice sheet-fluid surface. The numerical solution is based on an initial-value approach. The kinematic and dynamic boundary conditions on the ice sheet-fluid boundary are used to advance the solution in time. The predicted results are compared to the experimental ones to evaluate the validity of the theoretical assumptions made. In most cases close agreement between experiments and theory is demonstrated. Together with the experiments, the numerical model developed is able to clarify several physical phenomena contributing to icebreaking resistance at the waterline of a vessel advancing in level ice.

Ice loads on the design waterline (DWL) of several vessels were computed with the program Venice to obtain ice load distributions on ship hulls advancing straight ahead in level ice. The purpose is to obtain the spatial distribution of ice loads on the ship hulls in level ice, including the information on how the ice loads vary as functions of ship speed or ice thickness. For one ship hull the computed ice loads were compared with ice load distributions measured in model scale. The computed distributions were also compared with the design line load distributions used in the Finnish-Swedish ice rules and in the Polar Class rules. Some clear differences were found.

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