Ship propagation through ice field

Summary. Ships navigate often on the ice covered waters of the Baltic Sea independently without ice breaker convoy. At first, ship bow enters into contact with the edge of ice field, then penetrates into ice by breaking the ice edge and propagates further through ice field. During the breaking process ice sheet exerts contact pressure onto ship hull obstructing thus its propagation. When a ship moves straight forward the contact area is relatively small and does not exceed ship width. When a ship turns within ice sheet its whole side runs into ice and contact area rises. This process is studied numerically in this paper. Ship hull is presented as a rigid body with its mass concentrated at its centre of gravity. Ship movements in space are also defined by three degrees of freedom at this point. Ice sheet is modelled as a thin deformable shell with modified Drucker-Prager material model assigned to ice. When shear strain in an element reaches a certain level this element fails and is removed from the finite element mesh. Contact pressure along the ship hull due to ice is integrated to the centre of gravity of ship hull in the form of resultant forces and moments. It is shown that ice breaking is a random process and time history of reaction forces presents a series of high peaks of very short duration. It is shown whether the ship can overcome ice field resistance with given mass and velocity or will the ship stop in ice. Frequency of major ice force peaks depends on velocity of the ship propagation: the greater the velocity, the greater the frequency.