A strong nonlinear ice load has a significant impact on the resistance and power demand of polar transport ships under different drafts in brash ice channels. In this study, the CFD-DEM coupling method is used to investigate the self-propulsion performance of a full-scale polar transport ship in brash ice channels. The interactions between the full-scale polar transport ship, propeller, rudder, and brash ice are effectively simulated. First, the hydrodynamic performance of an open-water propeller is tested, and it is found that the numerical errors of efficiency and the experimental result are less than 8%. Then, the ice resistance, total thrust, effective power, delivered power, and propulsive efficiency of the polar transport ship under different draft conditions are studied, and the results are in good agreement with those of the self-propulsion model tests in the brash ice channel. Through a numerical simulation of self-propulsion in the brash ice channel, self-propulsion points under different drafts and brash ice thicknesses are obtained. It is found that the propeller rotation speed is closely related to the draft depth. Finally, experiments and numerical simulations of the total ice resistance are carried out under different brash ice thicknesses, and the results are consistent with those of the empirical formulas. The accuracy of the three empirical formulas under different drafts is compared. This research work determines the resistance, power demand, and propulsive efficiency of a polar transport ship under given ice conditions and speeds, as well as the self-propulsion points under different ice thicknesses. It is of great significance for the control of ships in polar navigation.

Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of pod thrusters under maneuvering conditions. The accuracy of the numerical method is verified based on a comprehensive convergence analysis and experimental comparison. A comparative analysis of the difference in thrust, moment and their coefficients between maneuvering and steady-state conditions is performed. Additionally, the impact of the advance number on the propeller hydrodynamic performance under maneuvering conditions is examined. The results demonstrate that the thrust coefficient and the torque coefficient of the propeller at positive and negative oblique flow angles exhibit asymmetry owing to the influence of the incoming flow velocity. Furthermore, the thrust and torque under maneuvering conditions increase significantly compared with those under the steady-state condition.

Rudder angle will change the flow field, resulting in different loads and interactions on the hull-propeller-rudder, which will affect the resistance and self-propulsion performance of the ship, and this effect will be amplified on the twin skeg ship. Resistance of the ship-rudder at the rudder angle of 0 ° -8 °, lift, moment, axial wake, the rudder profile velocity vector at the propeller shaft height, and the dynamic pressure distribution on the inner and outer surfaces of the rudder were simulated by CFD(Computational Fluid Dynamics) method, and verified by the EFD(Experimental Fluid Dynamics) method. Self-propulsion factors of the hull-propeller-rudder with rudder angle of 0 ° -6 ° were calculated by CFD method, and compared with the EFD results. Axial wake, dynamic pressure on the surface of the propeller and rudder and the velocity vector near the rudder, and the flow field and vorticity field of the hull-propeller-rudder were analyzed. The results showed that : 1 ) The CFD results had the same trend as the EFD results. When the rudder angle was 6 °, the total resistance of the ship-rudder was the smallest, and the resistance decreased by about 1%. 2 ) The change of rudder angle had little effect on the wake field in front, but it had a great influence on the flow field around the rudder, which in turn affected the resistance, lift and moment. 3 ) Self-propulsion performance was the best when the rudder angle was 4 °, and the self-propulsion power can decrease by about 4%, mainly due to the beneficial interaction between the propeller and the rudder. 4 ) Rudder angle had little effect on the surface pressure of the propeller, but it will slightly change the axial wake behind the propeller, and the dynamic pressure of the rudder was quite different. 5 ) When the rudder angle exceeded the optimal rudder angle of 4 °, the interaction between the hull-propeller-rudder became unfavorable, resulting in the chaos of the vorticity field and the overall performance degradation. For twin skeg ships, proper arrangement of rudder angle can effectively improve ship performance and achieve energy saving purpose.

In this paper, the uncertainty analysis method of ITTC (2017) for ship model self-propulsion tests was studied, and the shortcomings of the ITTC method were analyzed. Combined with the ship model self-propulsion tests carried out by SSSRI, an improved uncertainty analysis method was proposed. First of all, the ship model self-propulsion test process was combed to determine the