With the rapid development of offshore wind power industry, the protection of wind turbine foundations has become increasingly important in engineering practice. Based on wave diffraction theory in stratified waters, this paper employs the eigenfunction expansion method to derive analytical solutions for wave interaction with concentric arc-shaped structures. The dimensionless wave loads induced by surface wave and internal wave as well as the corresponding maximum wave elevation distributions are obtained. The results show that the double-layer arc structure exhibits superior wave attenuation performance compared to the single-layer configuration. In stratified fluids, the wave loads induced by surface wave and internal wave are of comparable magnitude, indicating that the influence of internal waves cannot be neglected. Parameters such as wave incident angle, water depth, porosity, arc angle, and radius ratio significantly affect wave loading characteristics. Proper selection of porosity and arc angle can further enhance wave attenuation performance and optimize construction costs.

With the continuous development of underwater detection technology towards low frequency domain, the sound absorption ability of conventional underwater acoustic coating needs to be significantly enhanced. In order to obtain better low-frequency sound absorption effect, a Topology-Shape-Topology (TST) optimization method is investigated in this paper. A new underwater acoustic coating is designed using the method which optimizes the distribution of materials in the anechoic layer. Compared with the traditional cavity-type acoustic coating, the acoustic structure designed by TST optimization method can achieve excellent sound absorption performance in the range of 200–1000 Hz. The peak value of sound absorption coefficient can come up to 0.9 at 321 Hz, and the average of sound absorption coefficient within the studied frequency range is above 0.8, resulting in an effective improvement of the low frequency sound absorption effect of the traditional underwater acoustic coating. Moreover, the underlying mechanism behind the sound absorption performance is revealed to obtain a further understanding of distribution regularities of materials. The study provides a new idea for the design of underwater acoustic coatings.

When an underwater vehicle navigates near a wall, the flow field around the underwater vehicle will be changed, which greatly affects its stability and maneuverability. Based on the CFD method, the hydrodynamic performance, including straight-ahead performance, oblique navigation performance, was analyzed under the conditions of near upper wall, bottom wall and vertical narrow channel. Finally, the following conclusions are drawn: when the underwater vehicle sails at a constant speed near the upper or bottom wall, it generates increased resistance, body suction and tail suction. When the vehicle approaching the upper wall at different distances, the directions of vertical force and pitching moment will be changed, and the ratio of direction transition interval is between 5-6 and 3-4, respectively. When the underwater vehicle sails at a constant speed near the vertical narrow channel, the influence of the wall effect on its vertical force and pitching moment has a relatively obvious competition relationship, and the competitive percentage accounts for about 50%. All hydrodynamic coefficients can be fitted by quadratic polynomials based on the reciprocal of the spacing ratio. The hydrodynamic coefficient of wall effect can be obtained from a graph by monitoring the combinations of different upper and lower spacing ratios when simulating the maneuverability of underwater vehicles.

Ship maneuverability is one of the most critical navigation performance of ships. The SIMMAN workshop is a systematic and authoritative international academic event focusing on the verification and validation of ship maneuvering prediction methods, which has garnered widespread attention worldwide. Based on a review of the SIMMAN workshop programs, latest developments, and related literature, this paper systematically summarizes the main research content, progress, and significant achievements of the three workshops. Furthermore, it analyzes the development trends and research directions in international ship maneuvering prediction methods and model test technologies as reflected by these workshops, and elucidates the insights they provide for the advancement of ship maneuverability testing and prediction methodologies.

The accurate prediction of bending stiffness and damage mode is important for understanding the bending mechanical behavior of reinforced thermoplastic pipe (RTP). Presently, adopting two-dimensional theoretical models, or simplifing three-dimensional stress state based on Lekhnitskii stress function, are the two main common approaches to analyse the bending performance of composite flexible pipes. The methods above, however are, difficult to accurately predict the stress distribution of each layer and the initial damage critical point of RTP under bending conditions. This paper firstly conducted geometric analysis of the section shape of RTP under bending conditions, and established a parametric representation method based on geometric analysis for the section deformation of each layer. Considering the nonlinear stiffness degradation of the material, a three-dimensional constitutive relationship of RTP was established. Then, combined with the virtual work principle, an analysis model for the bending mechanical properties of RTP was established. Further, the four-point bending test was carried out to verify the rationality of the theoretical model, and the influence of initial ovality and winding angle on the bending stiffness of RTP was analyzed. The results show good agreement between experimental data and theoretical model calculations. The bending stiffness of RTP is mainly affected by the winding angle and slightly affected by the initial ovality.

In this paper, an underwater explosion acoustic-structure interaction numerical model of air-backed glass fiber reinforced composite foam sandwich panel is established using a nonlinear finite element software ABAQUS. The damage characteristics of composite foam sandwich panel under underwater explosion are investigated. Full-scale air-backed composite foam sandwich panel underwater explosion experiments were conducted in a large-scale explosion pool, which validated the accuracy of the acoustic-structure interaction numerical model. The results indicate that under underwater explosion loading, the air-backed composite foam sandwich panel primarily experiences delamination damage. The damage is concentrated at the center of the panel and along the surrounding boundaries. As the shock factor increases, the damage of the cohesive layer gradually extends inward from the surrounding boundaries. As the foam core density increases, the impact resistance of the composite foam sandwich panel progressively improves.

This paper focuses on a numerical algorithm for analyzing flow-induced noise of composite plates. In this study, a method based on the superposition of uncorrelated plane waves was proposed to synthesize turbulent fluctuating pressure and calculate flow-induced noise using the finite element acoustic-vibration coupling module. The detailed theory and procedures of this algorithm were provided for rectangular plates as an example. The computational results were compared with analytical theory to validate the accuracy of the algorithm. Based on the wave number filtering principle, the criteria for selecting the truncation wave number was given, and the algorithm was compared with traditional methods in terms of computational efficiency, demonstrating the advantages of the algorithm in computational efficiency and accuracy. Finally, the mechanism of flow-induced noise generation in composite plate structures with acoustic coating was analyzed in this paper using the proposed algorithm, providing theoretical support for reducing flow-induced noise of underwater vehicles.

To solve the trajectory tracking problem of Unmanned Surface Vehicle (USV) when the parameters of model are uncertain, this paper designs a trajectory tracking strategy for USV based on adaptive control and non-dominated fast sorting multi-objective genetic algorithm (NSGA II). Firstly, a three degree of freedom USV kinematic and dynamic model is established. Secondly, based on Lyapunov theory, an online parameter estimation strategy and an adaptive trajectory tracking controller are designed for model parameters with uncertainty, and the convergence of trajectory tracking error is proved based on Lyapunov theory. Subsequently, to obtain the optimal values of a large number of controller parameters that require manual setting in the controller, a multi-objective controller parameter optimization model is established with the objectives of minimizing tracking error and minimizing control input. By solving the controller parameter optimization model through NSGA II, the optimal controller parameters are obtained, thereby enhancing the controller performance. Finally, numerical simulation experiments are conducted, and the experimental results verify the effectiveness of the trajectory tracking control algorithm.

At high subcritical Reynolds numbers, the flow past the circular cylinder has two types of complex flow phenomena, namely massive separation flow and shear layer transition. The traditional Improved Detached Eddy Simulation method (IDDES) is based on a fully turbulent assumption and is not suitable for dealing with transition. Meanwhile, the transition models (TRANS) based on the RANS method are incompetent to simulate the three-dimensional turbulent structure caused by massive separation. Therefore, this article integrates the IDDES approach with the TRANS model to develop an IDDES-Tr model capable of simultaneously resolving massive flow separation and shear layer transition. Numerical simulations were conducted for flow around a cylinder at a high subcritical Reynolds number of Re=1.4×10⁵, with results subsequently validated against experimental data. The comparison demonstrates a strong agreement between the simulation and experimental data, indicating that the IDDES-Tr model accurately captures the features of flow around a cylinder at high subcritical Reynolds numbers. In other words, the new model can effectively simulate simultaneously massive separation and shear layer transition.

Liquid sloshing is prone to occur in liquid cargo ships under the action of wind and waves, and the impact generated by the sloshing will damage the compartment structure, which is one of the important factors inducing safety accidents. Therefore, it is crucial to understand the sloshing phenomenon and propose an efficient anti-sloshing structure. In this study, a new type of floating baffle is proposed, which can provide a better anti-sloshing effect under different filling rates compared with traditional fixed baffle. Sloshing under high-risk filling rate is investigated by numerical simulation based on STAR-CCM+, focusing on floating baffles with different sizes and angles, and the optimal structure of the baffle is selected by analyzing the wave surface displacement, baffle velocity, wave profile, and fluid flow pattern with velocity vector magnitude. The results show that floating baffle can effectively suppress the sloshing by coupling various sloshing mechanisms, its web can cut the free liquid surface in time to suppress the sloshing, and the end of its bottom flange can generate vortex to effectively dissipate the fluid energy, and the heave motion of the baffle can change the trajectory of the fluid mass point under the free surface to reduce the impact on the compartment wall, which further enhances the anti-sloshing effect.