Numerical Simulation of Brash Ice

Abstract

Numerical Simulation of Brash Ice is a research project carried out to develop a numerical tool, which is capable of simulating the ships navigating through a brash ice channel. The tool is based on Discrete Element Method and current version is simulating the problem in model scale due to ease of validation. Properties of the ice channel, 3D mesh of structure, propeller characteristics and open water resistance data have to be input to the code. Output consists of numerical results of ice loads on ship, ship velocity and acceleration, pitch and roll angles of ship and graphical output of interaction of ice particles with ship. In order to calibrate the parameters of the code, standard cylinder experiment was simulated and results were compared with the experimental results. Different parameters of the simulation were changed and sensitivity of the results were studied. Graphical output of the simulation was also compared with underwater camera footage. General behaviour of the ice particles were identical in the vicinity of the structure. However the ice loads on structure had discrepancies. Simulation of an Ice Class Tanker was also carried out. Simulation parameters were set to match the actual ship model experiment. Results were compared with experimental values and under water videos. In this case also ice loads tend to be higher than expected. However particle behaviour near hull is acceptable. Cause for high ice loads was identified as deficiency in modelling the behaviour of far field ice particles in current tool. Simulation tend to overestimate the particle motions in far field due to the deficiencies in implemented friction model. (Cundall-Strack Friction). Therefore more work has to be done in order to improve the friction model in simulation environment. Further a more complex Ice-Structure interaction algorithm can improve the quality of results as well. In conclusion the current tool is suitable for obtaining qualitative results on ship navigating in brash ice channel in early design stage. Specially to visualize the ice particle flow around ship hull and identify possible concentration of ice particles especially around appendages