Interaction of ships under navigation in ice conditions

At intensive winter navigation, the ships should separate under movement on opposite courses or make overtaking of slowly moving cargo vessels in the water areas covered with ice. Side force and yawing moment that appear on ship hull under these maneuvers, and it is necessary to allow them at ship traffic management.  At carrying of these maneuvers in the conditions of free from ice water area, the distortion of the structure of flow in changeable space between hulls of vessels produces the side force and yawing moment. In ice conditions, the ice floes between hulls and outside are the major factors defining values and direction of side force and yawing moment. Ice loads on the ship hull exceed considerably the loads caused by water flow around hull. Therefore, the side force and yawing moment exceed ones on free water surface. Experiments in ice basin performed early have shown that besides increase of side force and yawing moment modules the variation of their action directions occurs during the divergence of vessels. Paper contents the possible approach to the theoretical solution of problem in point, namely, parameterization of ice effect on vessel hull at interaction with opposite or overtaken ship. Forces affecting the hull are divided on two components: the effect of small ice floes on the outboard side of hull and additional resistance from ice cake on the inboard side of hull. Algorithm of this problem solution and some preliminary results of computations are presented in the paper.