With the rapid development of the transportation industry, ship-bridge collision accidents occur from time to time and bring about loss of life and property. Ship-bridge anticollision facilities can reduce the damage of ships while protecting the bridge structure. In view of the shortcomings of traditional steel box, such as high stiffness and unchangeable protection position, a new self-floating ship-bridge anti-collision device is designed based on gradient foam aluminum composite sandwich structure. A ship-anticollision device-bridge pier collision model considering pile-water-soil coupling effect was established by finite element software LS-DYNA. The damage characteristics of ship-anticollision device-pier under typical collision loads were studied, and the crashworthiness of anticollision device under cases with different ship speed and ship collision angle were evaluated. The results show that the anticollision device has excellent buffering and energy absorption characteristics, which can effectively reduce the peak value of collision force, prolong the collision time, reduce the damage of pier and effectively reduce the damage of bow structure.

A marine riser usually works in the form of multiple riser clusters. The hydrodynamic interference characteristics between adjacent risers are obviously seen, and the interference can accelerate the fatigue damage. Therefore, it is meaningful to investigate the vortex-shedding patterns and the hydrodynamic interference characteristics of twin cylinders in order to ensure safe operation of risers. This study was aimd to parametrically investigate flows around twin moving cylinders at a staggered arrangement by a ghost cell method, in which, the incompressible Navier-Stokes equations were solved on a Cartesian staggered grid by using an in-house developed time semi-implicit finite difference method. A ghost cell method was used to enforce the no-slip boundary conditions. A radial basis iso-surface function was used to track the moving boundary implicitly and identify the properties of background grid. Based on the present numerical model, flows around twin forced moving cylinders at a staggered arrangement were simulated. Vortex patterns and force coefficients were analyzed under different gaps and oscillation frequencies. Typical interference phenomena such as synchronized, deflected and merged vortex patterns were observed. The results can provide theoretical guidance for the arrangement optimization of the riser clusters.

Based on the SPH numerical simulation method, this paper presents an analysis of the wave variation of regular and irregular waves propagating along an inshore island reef with a floating structure, and the dynamic response of a tethered floating structure under the island reef topography, respectively. The results show that the floating structure attenuates irregular waves better than regular waves when a tethered floating structure is installed in front of the shore reef, and changes in wave height have little effect on the attenuation of floating structure wave height. However, changes in wave period have a greater impact on the attenuation effect of the floating structure, and the floating structure is less effective in attenuating the wave height of long-period waves. The maximum vertical displacement, maximum longitudinal rocking angle and maximum transverse oscillation values of the floating structure all show an increasing trend with wave height increasing under different regular wave height conditions, with the maximum longitudinal rocking angle being the most sensitive to changes in wave height and the maximum vertical displacement being the least sensitive.

An eccentric semi-submersible foundation was proposed considering the characteristic of wind energy direction concentration in actual environment. AQWA-Fast software was used to establish the floating wind coupling analysis model, and the kinematic response characteristics of symmetric and eccentric wind turbine were compared and analyzed under different incident angles of wind waves. The results show that the variation of wave incidence angle hardly affects the average motion response value and average power generation of the floating wind turbine. When the incident angles of wind and wave are the same, the eccentric platform has better motion performance in terms of sway, roll, and yaw degrees of freedom, and to some extent the mooring tension is reduced. When the wave incidence angle constantly changes, the eccentric design will improve the motion performance in terms of sway, roll, pitch, and yaw degrees of freedom. In addition, the eccentric floating wind turbine has better comprehensive power generation performance.

With the development of high flow turbopumps, the size and speed of impellers have increased rapidly, resulting in the coupling vibration phenomenon of the turbopump. In order to keep the turbopump running smoothly and reduce its vibration and noise, the coupling dynamics characteristics of the turbopump rotor system were studied in this paper. Firstly, based on the simplified finite element model of the turbopump, it was found that when the rotor frequencies of different orders approach each other in the Campbell chart, two coupling characteristics phenomena of curve turning and merging would occur. Further analysis of the rotor modes conducted for the coupling characteristic phenomenon showed the different orders of the coupling characteristic modes would affect each other. Secondly, a two-degree-of-freedom system was used to simulate the coupling characteristics of the rotor, and then the effects of coupling degree, damping and gyroscopic torque on the characteristics were analyzed. Finally, investigation on the coupling dynamic characteristics of the two-degree-of-freedom system revealed that the dynamic response would change abruptly when the curve turning and merging occurred, leading to the increase of the coupling vibration amplitude and even the instability of the system. The research results could provide theoretical guidance for the safe and stable operation of rotor systems.

In order to investigate the hydrodynamic performance of ships in restricted channel of polar regions, a hybrid Green’s function method based on three-dimensional potential flow theory was established, in which, the free-surface Green’s function was taken as the kernel function in the fluid domain of channel. The ice sheet on both sides of the channel was modeled as a thin elastic plate. The ice-surface Green’s function, which automatically satisfies the ice-covered water surface, seabed and radiation conditions, was adopted in the fluid domain below the ice. The boundary integral equations were established with the two kernel functions above respectively. To improve the efficiency of computation, the influence coefficients related to the wave component of the ice-surface Green’s function were obtained based on its analytical integral over vertical line segment. On the basis of above method, a computer program was developed. By taking a barge with available computational data as the research object, the effects of control surface length and mesh density on the convergence of calculation were first discussed, and the reliability of the method and program was verified. Then further calculations and analysis were conducted on the hydrodynamic coefficients under different channel widths and ice thicknesses. From the numerical results the oscillatory phenomenon was observed in the hydrodynamic forces of the ship in water channel confined by ice sheets. And with the decrease of channel width and increase of ice thickness, the oscillation becomes stronger.

Numerical modelling based on Navier-Stokes equations and model experiment for studying liquid sloshing have the limits of low computational efficiency and high economic cost. Therefore, to predict the hydrodynamic pressure and wave height, the time-histories to numerical and experimental results were reconstructed in this paper through the neural network model. The total numerical and experimental pressures and free surface elevations were taken as training samples, and CNN, RNN and LSTM with strong repretational ability were used to reproduce the sloshing responses. The internal structural parameters of the neural network were systematically adjusted, besides, the errors and correlations between the predicted and actual values were analyzed. The results show that the error is lower than 4% and the correlations of both RNN and LSTM reach 0.88, which is in general superior to CNN, and that LSTM is optimal in predicting the long sequence data. Overall, three surrogate models can well predict the sloshing wave height and pressure, and are promising in the study of liquid sloshing.

In this paper, a fast prediction model was established for ship motion and load based on Gated Recurrent Neural Networks (GRU). GRU neural network is a concise and efficient recurrent neural network that captures the temporal information of training samples to establish a model for predicting unknown samples. The forecast model consisted of two independent GRU neural networks used to predict ship motion and load respectively. The historical ship pitch and heave data were jointly used as the input of the motion prediction model to predict the ship pitch and heave in the next few seconds. The motion prediction results were used as the input of the load prediction model to achieve the prediction of the vertical bending moment in the midship. The method was validated through model test data, and the results showed that the prediction results at different lead times were in good agreement with the test results in terms of amplitude and phase, verifying the feasibility of the established ship motion and load prediction model.

The additional strengthening effect caused by the non-proportionality of loading-path under cyclic loading is an important factor that shortens fatigue life of material. To solve this issue, the plane of maximum shear strain amplitude was treated as the critical plane, and the non-proportionality of material and loading-path were both considered. A new non-proportionality factor was introduced to quantify the impact of non-proportionality loading on fatigue life of material based on the equivalent strain model and critical interface theory. Secondly, the damage mechanism and fatigue failure mode of the specimen were also considered, the maximum normal stress on the critical plane was adopted to characterize its contribution to fatigue failure. On this basis, a multiaxial fatigue life prediction model was proposed by combining the non-proportional factors. Finally, the proposed model was verified by using the fatigue test data of four materials under multiaxial loading, and the prediction results were compared with five proposed models. The results show that the proposed model can effectively improve the fatigue life prediction accuracy under non-proportional loads compared with the existing models.

This paper aims to propose an improved theory of homogenization for acoustic coatings, the acoustic coating with periodic cavities can be considered equivalent to a uniform layer, thus improving the computational efficiency of sound absorption. Based on the traditional homogenization theory, parameters of equivalent density, modulus, and thickness for the acoustic coating by are derived incorporating the potential flow theory and the Minnaert resonance scattering theory. The sound absorption coefficient of the coating is then obtained through analytical calculation. This paper specifically addresses the effectiveness, efficiency, and adaptability of the proposed algorithm, thus offering technical support for accurately predicting the sound absorption coefficient of acoustic coatings within the middle and low-frequency range.