Prediction of the ice resistance of icebreakers using explicit finite element analyses with a real-time load control technique

Abstract

This paper proposes a simulation technique to real-time control hydrostatic and hydrodynamic forces acting on pack ices depending on a user-subroutine of an explicit finite element code. By controlling the buoyancy for the wet elements, the hydrostatic force was possible in terms of a nonlinear restoring force. The hydrodynamic force acting on a pack ice was expressed as a drag force. The CFD analyses for a single pack ice under constant surge speed were carried out to estimate the total resistance and accordingly to calibrate the average drag coefficient. The proposed approach with the average drag coefficient produced same results with the CFD analyses. The user subroutine with the drag coefficient was used to simulate the towing tests of an icebreaker in the pack ice condition. There were different ice resistances between the test and simulations. This forced to recalibrate the drag coefficient considering the difference of the stiffnesses in the towing test and simulations. After recalibration of the drag coefficient to 2.0, there were successful coincidences between the towing tests and simulations in terms of the ice resistances. The radiation effects were critical in the motion of pack ice, so the radiation force should be considered for future study.