Time-domain numerical simulation of the motion of small floating bodies drifting in waves

Theoretical and experimental investigations have been conducted to examine the behaviour of small icebergs and bergy bits in unidirectional regular waves. A nonlinear time-domain method based on the equivalent motion concept and a corresponding computational algorithm are presented for predicting the motion and trajectory of small ice masses drifting in an open seaway and near a gravity base platform. The general equations of motion of a rigid body are applied, and the wave forces are determined as the sum of the resultant of wave-induced pressures integrated over the instantaneous wetted surface of the body (the Froude-Krylov forces) and the flow disturbance induced by the presence of the body as determined by the equivalent motion method. The algorithm is used to predict the motion and trajectories of free drifting and towed spherical models in small and large amplitude waves. The computed values are found to be in good qualitative and quantitative agreement with the experimental measurements outside the heave resonance range where the motions are over-predicted. The motions of the ice mass are also simulated near a cylindrical gravity platform taking into account the effect of the waves diffracted by the structure. Large heave motions are predicted in close vicinity of the platform. In addition to instances where collisions were predicted, the ice drifted around or maintained a stationary position in front of the structure. It is concluded that the method can be applied to provide predictions of the kinematic parameters of motion of small bodies drifting in waves