The problem for interactional flows between the ship hull and the propeller is studied by computational fluid dynamics (CFD) simulators with the RANS-based computational model. In this paper, we mainly emphasize the modelling of the propeller, by introduction of a multiple reference frame (MRF) approach and an overset mesh method. Importantly, the effects of a free-surface on the interactions are taken into account by the VOF method. By comparison with the experimental data for the standard model KRISO container ship (KCS), both technologies for the treatment of the propeller can capture its movement in open water like the ship resistance and self-propulsion, including the distributions of the pressure on the hull surface, streamline at the stern and the ship boundary layer caused by propeller suction. Interestingly, the results of the thrust and torque agree well with such both approaches, although the hull resistance is overestimated by the MRF method, resulting in substantial calculation errors of the prediction of the self-propulsion coefficients. Within the framework of these techniques, the MRF method trends to be higher efficiency in computations but conversely for the overset mesh method there exists higher accuracy. By visualization of the motions that describe the physics of the interaction between the ship hull and propeller, it has been shown that the simulators can capture most of the significant features in ship-propeller interactions with a free-surface.
The interaction among ship, propeller and rudder is one of the most complex ship hydrodynamic problems. The flow around the propeller behind a moving ship is completely different from that in open water with a uniform inlet flow condition. At the same time, velocity distribution of flow around the hull is affected by the rotating propeller.
The turning rudder adds more complexity to the system. The changes of rudder attitude lead to the change of ship motions, which further affect the flow field around the ship hull and the propeller. The interactions between the ship hull, the propeller and the rudder are coupled, and ignoring one of these factors eventually affects the simulation results. In addition, the high-speed rotation of the propeller generates cavitation and complex flow field at the rear of the hull, which will also bring unprecedented challenges to the study of such problems.