Cavitation is a special physical phenomenon that exists in fluids, and the cavitation model is a key technology in cavitation flow calculation, which describes the cavitation phase transition process. The rate of cavitation phase transition is directly related to the nucleus density. In this paper, the R-P equation and nucleus transport equation are used to improve the bubble dynamics-based cavitation model, so that the new model includes the influence of nucleus density evolution with the cavitation process. The improved cavitation model can effectively simulate the collapse process of two-dimensional vapor bubbles. In the final stage of vapor bubble collapse, the evolution of gas phase volume occupancy can reach 0 in a limited time while maintaining the stability of the calculation process. The simulation results are in better agreement with the theoretical results.

The interaction between waves and marine structures involves complex geometric boundaries, wave impacting, overtopping. To accurately simulate this complex phenomenon, DualSPHysics is employed to build a numerical wave flume based on Smoothed Particle Hydrodynamics (SPH), which is a grid-free particle method. In order to validate the accuracy of the model, regular waves are generated by a piston-type wavemaker. By analyzing the wave height with different particle spacing, the model was demonstrated that it can generate stable regular waves. Furthermore, the impact of regular waves on a vertical wall is simulated with the model. Under the action of wave impact and inertial force of the water, the pressure at different positions on the vertical wall shows the following characteristics: it quickly reaches the peak in a short time, then decreases, increases again, and finally decreases. The time series of pressure have a saddle shape. By comparing the wave shape and velocity field at the same time, it is found that the angle between the wave and the vertical wall, as well as the water head rise, are the main factors leading to this saddle-shaped pressure curve.

The machining deformation of a large pressure cylindrical shell might affect its subsequent machining accuracy and application requirements. A large titanium alloy pressure cylindrical shell after deformation was studied in this paper. Based on the thermal elastic-plastic and creep finite element theory, the numerical simulation of thermal correction of the deformation correction process of the cylindrical shell was carried out through the calibration tooling and thermal correction method. The results show that the error of elliptic end calibration of the deformed large titanium alloy pressure cylindrical shell is controlled within 1%, which could meet the engineering requirements. The overall calibration effect achieved with the calibration tooling of ring-shaped is better, and the error is reduced by 0.2% compared to the calibration tooling of cross-shaped. The holding time, heating rate and cooling rate of heat treatment have little effect on the calibration effect of the deformed cylindrical shell, while the spring stiffness has a great influence. Finally, a set of good heat treatment straightening process for large pressure cylindrical shell was obtained.

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.

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.

Considering the directional differences in the distribution of environmental conditions, the directional design criteria can be adopted as long as no jeopardizing to the structure reliability is introduced. Compared with the omnidirectional design condition, the directional criteria can optimize the structural design by redistributing the exceedance probability on all directional sectors. The directional design conditions that meet the requirements of the target reliabilities can be determined by the iterative method proposed in this paper, and the optimal structural design and the corresponding directional design condition can be determined by design analysis and comparison for specific structures. The statistical uncertainty impact caused by distribution fitting and large extrapolation needs to be carefully considered, and using the proposed "combination method" to derive the environmental condition distribution is an effective solution to reduce this impact.

Large Eddy Simulation (LES) method was employed to simulate the pressure fluctuations on the wall of NACA 0015 hydrofoil. The spatio-temporal correlation characteristics were studied using wavenumber-frequency spectrum (WFS), and six empirical models were used to predict the WFS on the hydrofoil. The results show that at zero angle of attack, as the position of sensors moves towards the trailing edge, the dimensionless convection velocity gradually approaches the theoretical predicted value of 0.7. At the same incoming velocity, the spectral level of the WFS at the ridge increases with the increase of the angle of attack. The predictions of the six empirical models show differences from the simulation results, with the Efimtsov model having the minimum values and the Ffowcs-Williams model having the maximum values. The simulation results fall between the predicted values of the Efimtsov model and those of the Corcos model.

The wall pressure fluctuation of the turbulent boundary layer (TBL) is a primary source of flow-induced vibration noise. Due to their broadband and highly chaotic features, it is difficult to accurately capture the complex spatio-temporal variations of the phenomenon. To analyze these intricate characteristics, the wavenumber-frequency spectrum is needed. And both experimental and theoretical modeling in this field have become critical research topics. This paper investigated the convection velocity characteristics of the TBL wall pressure fluctuations wavenumber-frequency spectrum. In the low-speed wind tunnel experiments a linear array of pressure sensors was used to measure TBL wall pressure fluctuations. The cross-spectral matrix (CSM) method was adopted to derive the wavenumber-frequency spectrum, obtaining the convection velocity at various wind speeds. Concurrently, hot-wire anemometer measurements were made for boundary layer parameters, which were normalized to analyze convection velocity characteristics. The new convection velocity prediction model was developed and applied to the classical Chase I wavenumber-frequency spectrum model. Comparisons with experimental data showed strong agreement between the convection ridge in Chase I model and measurements, validating the new model’s broad applicability across wind speeds and frequencies. This study provides new theoretical insights and technical pathways for TBL wall-pressure wavenumber-frequency spectrum modeling and ship noise control technology.