A panel method for modelling level ice actions on moored ships. Part 1: Local ice force formulation

Model tests of a moored ship in level ice have been performed. The experimental setup made it possible to measure interaction forces between the ice and the ship's bow area. These kinds of measurements are for the first time reported in the literature. Methods for constructing local ice forces based on observations from the model tests are introduced. The ice-hull interaction is separated into ice breaking, rotation and sliding phases. It is assumed that breaking and rotation occur in the vicinity of the waterline and that the main sliding phase occurs under water. A simplified formulation for forces near the waterline caused by breaking and rotation of ice floes is based on four random variables. An algorithm to extract these variables from the measured data is given. Probability distributions are fitted to the random variables and the distributions are analysed with respect to effects of the mooring stiffness and the ice drift speed. The difference between the constructed and the measured ice forces in terms of mean values and standard deviations are small. A Coulomb friction model is assumed for the friction forces on the wet part of the bow. The friction coefficient is assumed to be stochastic and is extracted from the measurements. Even though the assumed friction model is simplified, it closely resembles the measured forces. The model is applied to study the dynamic response of a moored realistic hull in a separate paper. (C) 2010 Elsevier B.V. All rights reserved.