A panel method for modelling level ice actions on moored ships. Part 2: Simulations

摘要

A semi-empirical method for calculating local ice forces on moored ships was described in Part 1 and is implemented for a real hull in this article. The method splits the ice actions into actions in the vicinity of the waterline caused by breaking of intact ice and rotation of broken ice floes, and actions below the waterline caused by ice-hull friction. The hull was discretized into flat panels and ice forces were calculated for each panel and summed to obtain the total ice action. The resolution of the discretization was studied and stable results were obtained with relatively few panels. The model was compared with model test data and satisfactory agreement was found for the mean mooring forces. Surge oscillations were larger in the simulations than in the model tests, probably due to underestimated ice-induced damping forces in the simulations. The dynamic surge response of the ship was investigated by varying the ice drift speed and the surge natural period. The coefficient of variation for the surge motions was largest for speeds around 0.10-0.15 m/s for all surge natural periods. The importance of parameterizing the ice forces in terms of the penetration of the ship into the ice is highlighted, as this strongly affects the dynamic response of moored ships in level ice. The model can be applied in studies of dynamic response of moored ships in level ice with constant drift direction and it can be extended to variable ice drift direction.