The contra-rotating rudder propeller has the characteristics of good maneuverability and high propulsion efficiency, which is usually applied in ship types, such as science research vessels and offshore engineering ships. The open-water characteristics of the contra-rotating rudder propeller are simulated by using the improved delayed detached eddy simulation (IDDES) method, with comparative analyses based on the model test results. The results show that the numerical simulation errors of the thrust coefficient and the torque coefficients of the propulsion unit at the design point are within 3%. It is observed that the rudder angle has smaller impact on the open-water characteristics of the front propeller but larger impact on those of the aft propeller based on the open-water tests under different rudder angles. The transverse force of propulsion unit is 0 at the rudder angle of 2.5° in the current case. The influence of the strut on the tip vortex of the front propeller is studied through the cavitation model test. The cavitation is significantly enhanced when the tip vortex of the front propeller meets the blades of the aft propeller or the tip vortex of the aft propeller. Based on the interaction of all components of the contra-rotating rudder propeller, the induced velocity correction coefficient is introduced to transform the design of the blades of the contra-rotating rudder propeller into the design of the blades under the given incoming flow condition.

The body-force method and the sliding mesh method are applied to numerical simulation of full-scale self-propulsion for a 9 400 TEU container vessel, respectively. The effects of the turbulence model, the meshing, the maximum number of the nonlinear iteration, the time step size, the geometrical parameter of the actuator disk and the size of the rotational domain on the calculation results are investigated successively. The key points affecting the calculation results and the corresponding optimal settings are determined by comparing with the model test results and the sea trial results, and the effectiveness of the self-propulsion numerical simulation at full-scale are validated. The propulsion factors and the flow field at the self-propulsion point of the two methods are analyzed and compared. It is found that both methods can predict the performance of the full-scale ship, but with different wake fields. The flow before the propeller disk of the two methods mainly differs in the axial and tangential flow, whereas the flow after the propeller disk mainly differs in the radial flow.

The hydrodynamic performances of a contra-rotating propeller and a contra-rotating rudder propeller are predicted by using the improved delay detached-eddy simulation (IDDES) model and sliding mesh method based on the OpenFOAM software. The thrust coefficients are analyzed by the fast Fourier transform (FFT) method. The numerically calculated thrust coefficients, torque coefficients and propulsion efficiencies of the contra-rotating propeller are compared with the model test results with the errors of 3%, 2% and 5%, respectively, indicating the validity of the numerical method. The numerical results of the contra-rotating rudder propeller show that the pressure drag is the main component of the drag of the pod and strut, and there is a reverse flow at the front of the strut. The strut, therefore, can be optimized from the two aspects. The strut and the pod can also reduce the vibration caused by the bearing force.