Discrete Element Simulation of Ships Navigating Through Brash Ice Channels

Abstract

The paper describes a simulation tool for simulating the transit of ships through brash ice channels, based on the Discrete Element Method (DEM). Fundamentals of the method are given, including contact detection and forces calculation. Artificial brash ice channels are created in the simulation domain by the so-called floating-up technique. Hull geometry is introduced into the model, handling non-convex bodies as composites of convex bodies. Hydrostatic properties are calculated according to the actual draft, pitch, and roll angles. In order to calibrate the parameters of the code, a standard cylinder experiment is simulated and the results are compared with the experimental model test results. Graphical output of the simulation is also compared with underwater camera footage. General behavior of the ice particles is identical in the vicinity of the structure. However, ice loads on the structure exhibit some discrepancies. Simulation of an Ice Class Tanker was also carried out, and the results were compared with experimental model test values and under water videos. In this case, ice loads tend to be higher than expected. However, particle behavior near hull is very satisfactory. The cause for high ice loads is identified to be deficiencies in modelling the behavior of far field ice particles in the current tool. The simulation tends to overestimate the particle motions in far field due to the deficiencies in the implemented friction model (Cundall-Strack Friction). The current tool is suitable for obtaining qualitative results on ships navigating in brash ice channel in the early design stage; especially to visualize the ice particle flow around ship hull and identify possible concentration of ice particles especially around appendages.