Modelling the hydrodynamic effects associated with station-keeping in broken ice

•The hydrodynamic effects are important for station-keeping in icy waters.•A floating structure induces flows that may affect the motion of ice nearby.•The proposed models predict the drifts of broken ice around a structure.

Complex hydrodynamic effects occur when ocean currents interact with a marine structure in the presence of a broken ice cover. Significantly different flow regimes are observed upstream and downstream of the structure. On the upstream side, broken ice driven by the flow tends to accumulate, thus exerting additional loads on the structure. On the downstream side, periodic fluid flow contributes to the spreading of broken ice in the wake. An approach to analysing ice motions on both sides of a structure is developed by applying appropriate numerical models. A potential flow model is employed to predict the ice motion upstream of the structure, and a vortex element method is adopted to simulate the vortical flows that transport broken ice downstream in the wake. The ice is considered either as an ensemble of discrete rigid bodies or as a collection of particles suspended on the water surface; both represent an ice cover broken by gravity waves and/or as a result of interaction with icebreaking vessels. However, waves, wind and any mechanical interactions that may cause failure or deformation of the ice are not modelled.The simulations reveal that the hydrodynamic interactions between a structure and upstream ice floes in loose ice fields may change drift velocities by more than 20%, whereas the periodic flow downstream of the structure in dense broken ice may cause rapid clogging of the channel behind the structure. These results emphasise the importance of including hydrodynamic models in simulation tools intended for modelling ice-structure interactions in icy waters, and the present study suggests how the fluid dynamics can be taken into account when modelling the dynamics of an ice field.