DISCRETE ELEMENT ANALYSIS OF ICE RESISTANCES AND SIX-DEGREES-OF-FREEDOM MOTION RESPONSE OF SHIPS IN ICE-COVERED REGIONS

The ice resistance is an important factor in the navigation process of ships in ice areas, which brings serious challenges to the navigation performance and navigation safety of ships. In this study, the dilated polyhedron based discrete element method (DPDEM) is used to establish a three-dimensional discrete element method (DEM) of the ice-ship dynamic interaction process, based on the approximate relationship between ship propulsion power and propulsion force, and considering propeller thrust, ice load, rudder force and hydrodynamic load separately, the ice resistance and motion response of 6-DOF nonlinear manoeuvre straight navigate of constant power icebreaker are calculated. In order to verify the reliability of the DEM, the results of DUBROVIN and LINDQVIST ice resistance formulas in a broken ice region and a flat ice region were compared and analyzed. Based on the simulation results of the ice resistance on ship under different propulsion power and complex ice conditions, the influencing factors of ship speed are analyzed. Accordingly, the simulation results of ship motion response in ice areas, such as ship heave, roll and pitch, and the prediction results of ice-breaking performance of polar ships are analyzed. Finally, the ice load and the motion response both in a broken ice field and in a level ice one are compared and analyzed. This method can effectively calculate the ice resistance of ship, and the simulation results can provide an important reference for the motion response and navigation safety early-warning of ships in ice-covered regions.