VALIDATION OF NUMERICAL ESTIMATION OF BRASH ICE CHANNEL RESISTANCE WITH MODEL TEST

摘要

Finnish-Swedish ice class rules require resistance estimation of ship navigation in a brash ice channel with a certain condition. The resistance is often evaluated by model experiments. We have been developing a numerical estimation method on the basis of physically-based modelling. The developed method can evaluate ship resistance qualitatively, but quantitative estimation and validation were insufficient. To validate the numerical evaluation method, we conduct numerical simulations of model tests and compare results with model test results by Wang et al. (IJOPE (19), 2009, 206-213). We develop a numerical model of model CCGS Terry Fox that was used in Wang et al. (2009). Simulation conditions were prepared to simulate the model test. The size of ice pieces is 99 mm×99 mm×23 mm, and the number of ice pieces is 96000. Four carriage velocities are examined: 0.10 m/s, 0.30 m/s, 0.55 m/s and 0.71 m/s; these correspond to those of the model tests. As a result, the resistances are close each other. At carriage velocities 0.10 m/s, 0.55 m/s and 0.71 m/s, the simulation results are in agreement with experimental results within the limits of plus-or-minus standard deviations. At carriage velocity 0.30 m/s, the simulation result is lower than the experimental results minus the standard deviation, although these are close each other. The tendencies of relationship between the carriage velocity and resistance are, however, somewhat different between the simulations and the experiments. In the numerical simulations, unphysical adhesion of ice pieces on the ship hull at the bottom and unphysical oscillations are observed. At this time, we do not know how to fix the above issues.