Ridge resistance of ships: DEM study

Ice ridges are the most severe, but common, first-year ice condition. Understanding ice ridge resistance on ships is important since the ice-going ships often encounter ridges. Ridges may not always stop a ship, but they will reduce the velocity and thus affect the transportation efficiency. Ridge keel resistance has been earlier studied using experiments and analytical and numerical models. In analytical approaches, ridge keels are assumed to have a geometry of a semi-infinite rubble field, with an infinite width and a finite depth.
Here we use 3D discrete element method to simulate a ship penetration through a non-cohesive ridge keel. Our approach allows detailed analysis on the ridge keel resistance records and ridge keel behavior during ship penetration. We show that the ridge width affects ridge resistance. The peak resistance values increase with the ridge width, but the rate of the increase is not constant. The peak ridge resistance values in our simulations with the widest ridges compare well with semi-infinite ridge models. In brief, our results demonstrate that ridge resistance models must account for the ridge width, yet there are no previous analytical models that consider this effect.