Ship maneuvering performance in waves has attracted much attention in recent years. One of main research efforts for this problem has been devoted to the high-accuracy computation of hydrodynamic forces and moments, as well as wave-induced motions, for ships performing maneuvering motions in waves. The objective of this article is to present a numerical study on the computation of the mean forces and moments, and wave-induced six degrees of freedom motions for a ship moving obliquely in regular head and beam waves. The RANS (Reynolds-Averaged Navier-Stokes) solver based on OpenFOAM is used for this purpose. The RANS computations herein are carried out in a horizontal coordinate system. The numerical wave maker with prescribing values of flow variables on the domain boundaries is applied for the wave generation in the computational domain. However, in order to prevent wave reflection, relaxed zones adjacent to the wave maker boundaries are set up. A new program module is inserted into OpenFOAM to update the flow velocity and wave evaluation on the wave-maker boundaries and in the relaxed zones during the RANS computation. The mesh deformation method is employed to allow the ship to perform motions in space. However, a virtual spring system is attached to the ship so as to restrain the surge, sway and yaw, while heave, pitch and roll are completely free, so that the ship is able to oscillate periodically around a certain position in space. The computed mean forces and moments with the inertia effects agree fairly well with the experimental data, and the computed wave-induced motions are also in quite reasonable agreement with the experimental data. This study shows a very successful computation, as well as the procedure of the RANS results processing.

Sampling method is an effective tool for building approximated models, which can improve the efficiency of hull form optimisation. A dynamic sampling method (DSM) is introduced herein to improve the accuracy and efficiency of the approximated model by considering the influences of sample quality measures in both input and output parameter spaces. The DSM uses leave-one-out to obtain an estimate of the cross-validation errors, which are maximised to determine the sample points in the design space. The variation is used for the calculation of continuous and multimodal regions. The proposed method is compared, using both numerical examples and hull form optimisation, with traditional sampling methods from the literature. The stem profile’s optimisation for KCS based on DSM and static sampling method is performed. And the optimised hull form with less ship resistance is obtained. The comparison results show that DSM performs better than the static sampling method. Abbreviations: AM: approximated models; ACE: accumulative error; AMDSM: approximated models based on dynamic sampling method; AMUD: approximated models based on uniform design; CAMM: continuous and multimodal; CF: covariance function; CFD: computational fluid dynamics; CV: cross validation; CVV: cross validation variance; DSM: dynamic sampling method; eLOO: leave-one-out error; LOO: leave-one-out; LHS: Latin Hypercube Sampling; MAPE: mean absolute predictive error; MCS: Monte Carlo Sampling; NN: neural network; RAAE: relative average absolute error; RMSE: root mean square error; SM: sampling methods; SP: sample points; SSM: static sampling method; TS: test samples; UDL: uniform design; VF: variation function.

Basis functions are key in constructing interpolation equations in hull surface modification based on radial basis functions (RBF) interpolation. However, few have studied the selection of basis functions in depth. By comparing several typical basis functions through a theoretical analysis and two-dimensional modification examples, the Wendland ψ3,1 (W) function is selected. The advantages of hull form surface modification based on W function interpolation are further validated through a case study. Finally, the modification method is used to optimize a trimaran model. An optimal hull form with fair lines is obtained, and its wave-making resistance coefficient and total resistance are reduced by 8.3% and 3.8%, respectively, compared to those of the original model. These findings not only further illustrate that the W function is relatively suitable for hull form surface modification, but also validate the feasibility and value of the RBF interpolation-based surface modification method in engineering practice.

This study investigates the hydrodynamic performance of ships entering a ship lift compartment that is under the influence of upstream channel geometry and proposes a mechanical traction scheme to enhance operational safety and efficiency. Utilizing a Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) approach with overlapping grid technology, numerical simulations were conducted for both single and grouped ships navigating through varying water depths, speeds, and shore distances. The results revealed significant transverse force oscillations near the floating navigation wall due to unilateral shore effects, posing risks of deviation. The cargo ship experienced drastic resistance fluctuations in shallow-to-very-shallow-water transitions, while tugboats were notably affected by hydrodynamic interactions during group entry. A mechanical traction system with a four-link robotic arm was designed and analyzed kinematically and statically, demonstrating structural feasibility under converted real-ship traction forces (55.1 kN). The key findings emphasize the need for collision avoidance measures in wall sections and validate the proposed traction scheme for safe and efficient ship entry/exit. This research provides critical insights for optimizing ship lift operations in restricted waters.

Hull form optimization is a key technical approach for developing energy-efficient ship hulls. However, selecting appropriate optimization parameters remains challenging. Traditional methods often rely heavily on designer experience, leading to subjective and inconsistent parameter choices. Consequently, optimization results vary significantly and lack generalizability. This study focuses on container ships, using the KCS model to investigate the impact of optimization parameter distribution and hull surface deformation on wave-making resistance. Through systematic analysis, an optimized parameter selection methodology is developed, resulting in significant improvements in wave-making resistance performance for container ships. Specifically, a 20.28% reduction in wave-making resistance and a −3.01% reduction in total resistance are achieved.

The hydrodynamic performance of the ship deteriorates as the cabin is damaged and takes in water owing to collisions, grounding, and striking a reef and so on. It will be a direct threat to the security of the ship. Once the damaged ship sinks, it will cause huge life and property damage as well as the pollution of the marine environment. The asymmetrical viscous flow around the damaged oil tanker is simulated. The simulation model is made by Gambit software, the viscous flow around damaged ship is simulated by solving RANS equations with FLUENT software. The typical damaged states of the oil tanker are considered, calculating its residual hydrodynamic performance , analyzing the effects of the breakage spot size and position to the flow and the hydrodynamic performance. To verify the simulation results, the correlative experiments are carried out. It indicates that the numerical results approximately match with the experimental results.