In ship design optimization, uncertainties in design variables or operational environments may prevent the ship performance from achieving the optimal objectives under the design conditions, and even lead to drastic performance deviations, causing the original design scheme to fail. The uncertainty-based design optimization method has been introduced into the ship design in order to mitigate the influence of uncertainties on the ship performance and enhance the robustness and reliability of ship design schemes. A mathematical model for the ship design optimization under the influence of uncertainties is established, along with its corresponding solution process. This method is then applied to the design optimization of a bulk carrier. The optimization results show that compared with the deterministic optimization scheme, the uncertainty-based optimization scheme is superior, and its robustness and reliability have been significantly improved.

The cavitation of a push-type ducted azimuth propulsor with the design target of balancing the large thrust under bollard condition and the required speed is numerically simulated under the maximum speed condition and the bollard conditions by using the Reynolds-Averaged Navier-Stokes (RANS) method with the SST k-ω model and Schnerr-Sauer cavitation model. The calculated cavitation pattern is generally in accordance with the experimental results. It captures the sheet cavitation on the back blade, the blade face cavitation, the tip-vortex cavitation and the tip-leakage cavitation. The propeller-hull vortex (PHV) cavitation is observed due to the close distance between the strut and the duct and ducted propeller. The correlation between the distance of the strut and the ducted propeller and the strength of the PHV is then analyzed to propose the distance that can suppress the generation of the PHV. The distance which is greater than 0.35D can basically eliminate the PHV. It provides an important support for the optimization design of the ducted azimuth propulsor based on the cavitation performance.

This paper focuses on the fluid-structure interaction (FSI) phenomena occurring during the operation of the composite rotor blades of the underwater vehicle thruster. The bidirectional FSI numerical method based on the finite element method (FEM) in ABAQUS and the computational fluid dynamics (CFD) method in STAR CCM+ has been used to calculate and analyze the open water performance, pressure distribution, blade deformation and stress of the composite blades in unsteady flow field under different advance coefficients. In addition, two solutions for negative volume mesh are proposed. The results show that the FSI effect on the composite rotor can cause partial thrust loss, and the vibration frequency of the composite blades in the FSI process mainly concentrates near the first-order blade frequency. When the advance coefficient is lower, it is also observed that the larger the axial load on the blades, the greater the axial deformation, and vice versa. The maximum stress caused by the FSI effect occurs on the root of the pressure side of the blade and the smaller the advance coefficients, the greater the maximum stress. The FSI effect is significant under low advanced coefficients. Both solutions can effectively solve the negative volume mesh problem.