Prediction Method of Ice Resistance and Propulsion Power for Polar Ships

Polar ships need to meet stringent safety and environmental requirements.Usually those ships are classified by diferent ice classes based on ice operation capability.However,the polar ships are also trapped by severe ice condition due to low propulsion power.Therefore,it is a realistic question to design the appropriate minimum propulsion power for ice operation.This paper focuses on the ice resistance and its related propulsion power for the ships with polar code(PC)classes.In consideration of seven typical polar ice conditions related to the PC rule of International Association of Classification Societies(IACS),a prediction method of ice resistance is developed by Lindqvist's model.The results are compared with those of Lindqvist's model and Riska's model by using two real ship lines.The comparison among propulsion requirements of representative classification societies is made,and a formula of minimum propulsion power is presented on the basis of ice resistance by revised Finnish-Swedish Ice Class Rules(FSICR)method.The results are verified by the actual values from seven ice class ships.A relatively good agreement is achieved.As a conclusion,the presented prediction method of ice resistance and minimum propulsion power is recommended for evaluation of ice resistance and its related propulsion power during the process of developing polar ships.

Prediction of added resistance of a ship in waves at low speed

This paper presents predictions of the added resistance of a ship in waves at a low speed according to the IMO minimum propulsion power requirement by a hybrid Taylor expansion boundary element method(TEBEM).The flow domain is divided into two parts:the inner domain and the outer domain.The first-order TEBEM with a simple Green function is used for the solution in the inner domain and the zero order TEBEM with a transient free surface Green function is used for the solution in the outer domain.The TEBEM is applied in the numerical prediction of the motions and the added resistance in waves for three new designed commercial ships.The numerical results are compared with those obtained from the seakeeping model tests.It is shown that the prediction of the ship motions and the added resistance in waves are in good agreement with the experimental results.The comparison also indicates that the accuracy of the motion estimation is crucial for the prediction of the wave added resistance.In general,the TEBEM enjoys a satisfactory accuracy and efficiency to predict the added resistance in waves at a low speed according to the IMO minimum propulsion power requirement.