Resistance prediction of double acting tanker in ice condition

Abstract

An icebreaker ship should have ice bow design at its stem part. It should have ice bow design because a common bow design has high resistance when sailing in open water. In order to solve the problem, previous researchers had introduced a Double-Acting Tanker (DAT) which is able to sail astern on sea surface covered by ice and sailing ahead in open water. The main problems are liaised with hull, ice, and propeller interactions during the DAT ship sailing astern which is very complex and simulation software is unable to simulate. In addition, the model scale test in the towing tank needs a full scale data of ice resistance. The aim of this work was to propose an empirical method to predict the resistance of DAT based on Koto method. The resistance components were water resistance, friction resistance, momentum resistance, immersion resistance and breaking resistance. The dimensionless constants for each resistance component were determined by using multiple regression variables. The forward sailing resistance of a DAT model was simulated at 0.4 m/s, 0.5 m/s and 0.6 m/s to predict the suction force of the propeller disc effect when DAT sailing at 1.8 m/s, 2.4 m/s and 2.7 m/s in iced sea surface condition. DAT resistance was predicted using the Finite Element Method (FEM) in Eulerian-Lagrangian Coupled theory (CEL) to detect the interactions between ship and ice sheets. The results showed that the ice sheet warms up when DAT sails forward and the ice sheet bends when DAT sails astern. The required force to break the ice sheet when sailing astern is less than the one sailing forward because of the critical bended length is shorter than normal bended length. The simulation results using the proposed empirical method show a good agreement with the experimental data. A total of 60% drag decreased when DAT sails backward. The significance of this study is the complexity of the astern sailing was explained clearly when the resistance of DAT was predicted by using empirical method.