This review systematically summarises the state-of-the-art modelling approaches for marine fish farming systems, encompassing experimental, numerical and analytical methods. It categorises key marine aquaculture structures, such as floating gravity cages, semi-submersible platforms, vessel-shaped cages and their inherent characteristics. Then it elaborates on core influencing parameters, including structural inherent factors and environmental parameters. Furthermore, the review identifies three major existing challenges: limitations of simplified calculation models, predominance of single-factor analysis and difficulties in establishing large-scale standardised databases for model validation and advanced algorithm application. Finally, this paper outlines prospective research directions to address these gaps, aiming to provide a comprehensive reference for optimising structural design, enhancing operational safety, and promoting the sustainable development of offshore marine aquaculture.
Efficient path planning for unmanned surface vehicles (USVs) is critical for autonomous maritime operations in complex environments. However, existing methods often struggle to balance path optimality with computational efficiency under multi-threat constraints. To tackle the challenging path planning problem for USVs in multi-threat maritime environments, this paper presents an adaptive inertia weight and triple learning factors-based competition of tribes and cooperation of members (AIWL-CTCM) algorithm. To enhance the efficiency of static path planning for USVs in complex maritime environments, the proposed AIWL-CTCM algorithm is designed to simultaneously achieving path optimality and navigation safety, thereby balancing multiple key performance criteria including path length, smoothness, collision avoidance, and convergence speed. The algorithm incorporates three key innovations. First, an adaptive inertia weight strategy that iteratively adjusts weights to improve convergence efficiency and solution quality. Second, a sine-acceleration-based optimization of the learning factors, alleviating the limitations imposed by static individual and tribal learning parameters. Third, a dynamic competition factor that varies with fitness values to accelerate the discovery of optimal solutions. Simulation results confirm that the AIWL-CTCM algorithm significantly surpasses the conventional CTCM and other benchmark optimization algorithms in terms of path planning accuracy, convergence speed, and stability.
The development of circular wave basins addresses limitations of traditional rectangular tanks in generating multi-directional waves and extreme sea states. However, specialized numerical tools for such basins remain scarce. This study presents an efficient three-dimensional time-domain numerical model based on potential flow theory and the boundary element method (BEM) for a circular basin with 50 wave-makers. Simulations for regular waves (wavelengths 0.6–2.0 m, steepness 3
Supercavitating vehicles offer considerable potential for high-speed underwater navigation owing to their low drag and high velocity. However, their guidance and control system design is significantly challenged by complex hydrodynamic interactions and pronounced nonlinearities. In this paper, the straight-line path-following problem for a supercavitating vehicle is investigated on the basis of a lateral dynamic model. An inner-loop yaw controller is designed by integrating a higher-order sliding mode control (HOSMC) scheme within an active disturbance rejection control (ADRC) framework. This combination compensates for system uncertainties and external disturbances while enhancing transient performance. Furthermore, a tail slanting force is introduced to attenuate planing force disturbances. For the outer loop, a line-of-sight (LOS) guidance law, which incorporates a reduced-order extended state observer (RESO) to estimate the sideslip angle, generates the yaw command to achieve path following. The finite-time convergence of the overall closed-loop system is rigorously proven using Lyapunov theory. The simulation results demonstrate that the proposed dual-loop guidance and control strategy delivers rapid, smooth, and accurate path tracking in the presence of uncertainties and disturbances, confirming its effectiveness and robustness.
The increasing availability of ship operational data from onboard sensors presents both opportunities and challenges for performance analysis and monitoring. This study proposes a robust ship operational data analysis (SODA) framework to enhance data usability through streamlined processing and analytical procedures. A key component of the framework is a novel metric to quantitatively evaluate the quality of the processed data, which offers a sophisticated tool to compare the performance of different ship operational data analysis strategies, thus is useful for the establishment of optimal data filtering and correction methods. The so-called information entropy weighted data quality index is formulated based on first principles, which systematically evaluates the processed data quality from three aspects: information richness, degree of data scattering, and the correlation between ship speed and engine power. Various filtering strategies and weather influence correction techniques adopted by ISO 15016 to enhance the reliability and consistency of performance metrics derived from the data are systematically investigated. Real-world operational data from a container ship are employed to validate the proposed framework, demonstrating notable improvements in data quality and consistency. The SODA framework can also facilitate the identification of long-term performance trends, highlighting its potential for supporting proactive maintenance planning. Results show that stricter filtering criteria are effective in reducing data scatter and uncertainty, but inevitably suffer from more severe loss of data richness. Milder filtering combined with weather influence corrections allows for more comprehensive trend analysis over extended periods. Overall, the proposed SODA framework provides a practical and robust solution for enhancing ship performance monitoring, enabling data-driven decision-making in maritime operations.
Offshore platforms operating in complex marine environments, particularly under typhoon conditions, face severe and rapidly evolving risks. To address this issue, this paper proposes a method for risk assessment, visualization and evolution analysis based on a cloud model and Markov Chain Monte Carlo (MCMC). First, an offshore platform risk assessment indicator system is constructed covering four dimensions: personnel, platform, environment and management. The comprehensive weights of these indicators are determined using the FAHP-DEMATEL method. Then, a comprehensive risk assessment and its visualization for offshore platforms is achieved through the cloud model which has advantages in handling risk ambiguity and randomness. Subsequently, the outputs of the cloud model are used as input parameters to the MCMC model to analyze the dynamic risk evolution process of offshore platforms under typhoon disturbances. Finally, the combined methods are applied to a platform in the South China Sea and its calculation results demonstrate that the dynamic risk evolution throughout the entire process of a typhoon’s passage can be effectively assessed and visually displayed. The proposed methods in this paper provide a scientific basis for maritime authorities to formulate efficient safety supervision strategies, such as precise risk control of offshore platforms at different time intervals, which are of great significance for ensuring the safe and stable operation of offshore platforms under typhoon weather.
In busy and complex maritime areas, navigation safety is of paramount importance, and predicting vessel trajectory accurately and identifying potential collision risk in advance is one of the effective means. Existing methods often struggle to capture the intricate spatial interactions and nonlinear temporal dependencies of vessels. To address this challenge, we proposed a novel trajectory prediction model based on an improved spatial-temporal graph multi-attention network, VTP-STGMAN. First, we revise the calculation of distance to the closest point of approach (DCPA), and navigational metrics, including the revised DCPA, time to the closest point of approach (TCPA) and actual distances among vessels, are applied to redesign the calculation method of the attention score in the graph attention network (GAT). The improved GAT model can extract the spatial features of multiple vessel trajectories accurately. Secondly, we integrate an attention mechanism with the temporal convolutional network (TCN) to adaptively capture nonlinear temporal correlation of trajectories. Finally, the probability distribution of the future trajectory rather than a deterministic trajectory of a vessel is predicted. It can reflect the inherent uncertainty of ship motion in the real world more accurately, and allow the collision avoidance decision system to minimize the risk expectation based on multiple high probability trajectories. Numerous experiments are conducted on real-world automatic identification system (AIS) data from Zhoushan (China) and Denmark. Evaluated results demonstrate that VTP-STGMAN can significantly outperform state-of-the-art baselines, reducing average displacement error (ADE) and final displacement error (FDE) by 23.6
Submerged breakwaters are widely used for coastal protection due to their relatively lower environmental impact compared with emerged structures; however, their hydrodynamic performance strongly depends on their geometric configuration. The present study investigates the hydrodynamic performance of porous submerged breakwaters with two geometric configurations: a tandem trapezoidal arrangement and a multi-slope profile. The analysis is carried out using the boundary element method (BEM) based on linear wave theory for water of finite depth. The hydrodynamic behaviour of the breakwaters is evaluated using wave-structure interaction parameters, including the reflection coefficient, transmission coefficient, and energy dissipation coefficient, which describe the proportions of incident wave energy reflected, transmitted, and dissipated by the structure. In addition, wave-induced horizontal forces acting on individual structural components are examined. In the case of the multi-slope configuration, the influence of geometric parameters such as the relative height of the stepped segments and the bottom width on wave attenuation characteristics is analyzed. Further, for the tandem configuration, the effects of the front and rear breakwater heights, as well as the spacing between the two units, are investigated. A detailed convergence study is conducted to ensure numerical accuracy, and the numerical model is validated through comparison with results available in the existing literature. The results indicate that both configurations are effective in attenuating wave energy, while the tandem porous breakwater provides greater flexibility in controlling wave transmission and dissipation through appropriate selection of spacing and breakwater heights. The findings provide useful design insights for optimizing porous submerged breakwaters and contribute to an improved understanding of wave attenuation mechanisms in complex submerged breakwater configurations for coastal and harbour protection.
Shaped charges are important in marine engineering, yet the effects of external media and liner geometry on jet formation and penetration remain unclear. This study combines experiments and simulations to systematically investigate jet mechanisms and penetration in water, oil, and air. The work highlights how detonation-wave reflection, transmission, and superposition at medium interfaces influence jet formation, establishes a mapping between jet velocity segments and the liner’s initial position, and proposes a segment-based method to quantify penetration contribution. Results show that the ambient-medium effect is controlled by the impedance ratio: higher impedance increases jet velocity, effective mass fraction, penetration depth, and kinetic energy, while reducing perforation diameter. Increasing liner wall thickness lowers jet-tip velocity, effective length and mass fractions, penetration depth, and kinetic energy, but enlarges perforation diameter. Decreasing the liner cone angle increases the maximum jet-tip velocity but reduces the effective-segment length fraction; effective mass and total kinetic energy vary non-monotonically with cone angle, peaking near 55°, while both perforation diameter and penetration depth decrease as the cone angle increases.
To address the challenges posed by large tidal ranges and shallow-water conditions on the performance of nearshore breakwaters, this study proposes a closely spaced inclined-pile breakwater (CSIPB), based on the engineering needs of a new energy project in the Nangang area of Tianjin Port. Hydrodynamic experiments were conducted using a 1:25 scale three-dimensional physical model in an L-shaped wave basin, at various water depths, wave heights, and wave period conditions. The wave transmission, reflection, and energy dissipation characteristics of the structure were systematically evaluated, and its harmonic response characteristics were analyzed using fast Fourier transform. The results indicate that the CSIPB exhibits strong adaptability to tidal variations. Wave energy dissipation dominates at high water levels, whereas wave reflection becomes the primary response under low water levels. Harmonic analysis further reveals that high-frequency harmonic components are mainly reflected back toward the incident side and become increasingly pronounced with increasing wave height and wave period. At shallow-water irregular wave conditions, although the effectiveness of the breakwater in controlling high-frequency wave components is reduced, the structure remains capable of effectively attenuating fundamental-frequency wave energy. Based on these findings, the proposed CSIPB is suitable for typical shallow marine environments with large tidal ranges and demonstrates good adaptability across a range of operational conditions.
With onshore resources increasingly depleted, marine oil and gas exploration carries critical strategic value. Airgun sources remain the dominant choice for marine seismic surveys, primarily because they introduce less disturbance to the marine environment compared to alternative energy sources. During operation, the airgun source generates high-energy shock waves and an airgun bubble, which impose impact loads on the floating structure suspending it. To investigate the interaction mechanism of the airgun shock wave on the floating structure and its dynamic impact response, common floating structure configurations are first simplified into models. Theoretical methods are employed to calculate the shock wave loads of the airgun source under various operating cases, and the load characteristics are compared and analyzed for different airgun immersion depths, working pressures, and volumes. Subsequently, based on the acoustic-structure coupling method, the dynamic impact response of the floating structure is analyzed under varying airgun immersion depths, working pressures, and airgun volumes, and the relationships between parameters such as immersion depth and the stress-strain state of the floating structure, as well as the displacements at its center and ends, are summarized. Recommendations are proposed for improving the floating structure used with the airgun source and optimizing its deployment method, and minimum recommended thickness curves for the floating structure under specified impact environments are provided. Finally, the dynamic behavior of the floater is examined for different structural configurations, to provide a basis for geophysical practitioners in selecting suitable floating structures matched to specific airgun source configurations.
Fuel optimization in maritime transportation has always been one of the primary concerns for shipping companies. In this study, we focus on improving the propulsion system of the KRISO Container Ship (KCS) vessel. Using the computational fluid dynamics (CFD) software Star-CCM+, different rudder designs are evaluated to assess their effectiveness, and the optimal distance between the propeller and rudder is investigated. The results indicate that variations in rudder design and propeller - rudder spacing not only significantly reduce hydrodynamic resistance but also enhance the vessel’s maneuvering performance.
Finding protective methods that reduce the forces acting on coastal walls can increase their lifespan and minimize their deterioration. Therefore, by utilizing various protective methods that have a mitigating role and can be applied in front of coastal walls, significant effects can be achieved in reducing the destructive forces acting on them. Thus, through conducting various research studies considering distance, coverage, and arrangement, the best and most optimal combination of structural elements should be determined to serve as a foundation for constructing improved protective coverings in front of coastal walls. In this research, by performing various experiments and changing parameters, including different protection structures, changing the design parameters, and changing the characteristics of the waves on the coastal wall, and by direct measurement, the incoming forces will be analyzed more precisely. In this research, a load cell device was used to experimentally assess the wave force that was applied to the coastal wall. A knife-edge flume, a special kind of flume, was used for this. An electronic dynamometer (load cell) was used to measure the wave force directly. The wave force exerted on the coastal wall was measured directly and calculated using the Morrison equation in all experiments at four wave heights: 18, 15, 12, and 8 cm. Furthermore, protective structures were utilized in various configurations, including sloping surfaces with different angles, stepped structures with varying step sizes, riprap coverings with different grain sizes, and submerged breakwaters at different distances and depths. According to the experiments, Morison’s equation does not provide acceptable results for protective structures attached to the coastal wall. Moreover, the results indicate that the best wave force dissipation is achieved with the submerged breakwater and riprap protective structure. Additionally, in the case of the submerged breakwater, the Morrison equation and the direct measurement method show the highest level of correlation.
Cycloidal propellers (CPs) are an unconventional propulsion system that combines high manoeuvrability with complex unsteady hydrodynamics, making them attractive for specialized marine applications such as dynamic positioning. Despite their potential, only limited experimental and numerical data exist, and almost no information is available on cavitation phenomena and their effect on performance, despite the large angles of attack typically experienced by CP blades. To address this gap, the present study numerically investigates CP performance with emphasis on thrust generation, efficiency, and cavitation dynamics. A RANS-based CFD approach coupled with a simplified cavity model is used to capture the unsteady flow structures and vapor cavity evolution around the rotating blades. Results highlight the role of eccentricity, of the pivot point location as well as of the number of blades on non-cavitating and cavitating performances, investigated at several advance coefficients and cavitation indexes. Comparisons between three- and six-blade configurations further reveal how blade count and cascade effects modulate force peaks and bubble transitions. The findings contribute to understanding the behaviour of CP under realistic operating conditions, offering guidance for future developments in this type of high-performance propulsion system.
Trajectory prediction of supercavitating vehicles remains challenging due to complex hydrodynamics and limited observation. To address the restricted field of view in optical measurement and the insufficient accuracy of the adopted numerical model, this study proposes a hybrid regression framework. It integrates time-frequency domain features with physical constraints from impact points. Using multi-view high-speed camera data and simulation results, key features reflecting dynamics such as tail-slap are extracted through piecewise alignment and error frequency-domain analysis. A hybrid feature space is constructed from time-domain polynomials and frequency-domain basis functions, and features are fused via ridge regression. Experimental validation shows that the proposed method achieves high-accuracy trajectory reconstruction. The overall root-mean-square error is reduced from 0.562 m to 0.005 6 m, an improvement of about 99
Ocean waves induce cavitation asymmetry and unsteady loads for underwater-launched vehicles during water exit, yet the quantitative regulation mechanism of wave height remains unclear. A numerical wave tank coupling VOF-LES, fifth-order Stokes wave and dynamic fluid-body interaction models is established. Results show that increasing wave height drastically enhances crest-phase cavitation asymmetry by raising the positive effective angle of attack to 2.64°, compressing upstream cavities while making downstream cavities expand, rupture and detach. Pressure fluctuations shift from concentrated peaks to dispersed high-frequency pulses, and the downstream collapse pressure peak reaches 6 times that of the upstream side. This intensifies lateral load asynchrony, causing significant vehicle yaw along wave propagation with largely increased lateral displacement and deflection angle. In contrast, the trough phase only shows a slight rise in the absolute negative effective angle, with weak cavitation asymmetry, uniform pressure distribution and superior disturbance resistance. The trough phase effectively mitigates high-pressure impacts from asymmetric cavitation collapse. This work reveals the phase-dependent regulation of wave height on cavitation and hydrodynamics, providing quantitative guidance for launch stability optimization.
Vortex-induced vibration(VIV)of an underwater manipulator in pulsating flow presents a notable engineering problem in precise control due to the velocity variation in the flow.This study investigates the VIV response of an underwater manipulator subjected to pulsating flow,focusing on how different postures affect the behavior of the system.The effects of pulsating parameters and manipulator arrangement on the hydrodynamic coefficient,vibration response,motion trajectory,and vortex shedding behaviors were analyzed.Results indicated that the cross-flow vibration displacement in pulsating flow increased by 32.14％compared to uniform flow,inducing a shift in the motion trajectory from a crescent shape to a sideward vase shape.In the absence of interference between the upper and lower arms,the lift coefficient of the manipulator substantially increased with rising pulsating frequency,reaching a maximum increment of 67.0％.This increase in the lift coefficient led to a 67.05％rise in the vibration frequency of the manipulator in the in-line direction.As the pulsating amplitude increased,the drag coefficient of the underwater manipulator rose by 36.79％,but the vibration frequency in the cross-flow direction decreased by 56.26％.Additionally,when the upper and lower arms remained in a state of mutual interference,the cross-flow vibration amplitudes of the upper and lower arms were approximately 1.84 and 4.82 times higher in a circular-elliptical arrangement compared to an elliptical-circular arrangement,respectively.Consequently,the flow field shifted from a P+S pattern to a disordered pattern,disrupting the regularity of the motion trajectory.
This special issue collects selected papers previously presented at the 2024 Innovation & Cooperation in Naval Architec-ture & Marine Engineering (ICNAME 2024) Conference,which was held at Harbin Engineering University from August 22-25,2024. From the 200 papers presented at the Conference,a selected list was chosen to be part of this special issue.The process of selecting those papers took a bit too long,and some of the initially chosen authors did not want to submit their papers to this special issue for various reasons. The submitted papers went through the Journal's normal review pro-cess,and the approved ones are included in this special issue.
The objective of this study is to simulate the free-fall launch of a lifeboat and to analyse its trajectory, pitch angle, velocity, acceleration, and pressure dynamics using Open Field Operation and Manipulation (OpenFOAM). Utilising the overset grid technique, which is well-suited for handling the expected large motions, the study employs multi-phase simulations based on the volume of fluid method. A series of 21 simulations is conducted, varying initial pitch angles and three different drop heights to thoroughly examine the lifeboat’s behaviour under various conditions. The analysis of pressure across multiple points along the same transversal and longitudinal planes reveals two significant pressure peaks: one at the bow during water entry and another at the stern, occurring after a secondary water entry triggered by turn-back spins due to restoring moments. Pressure contours indicate that the keel experiences the highest loads, highlighting it as a critical area of concern. Additionally, the kinematics of each scenario is analysed to determine which initial pitch angle would allow the lifeboat to distance itself most effectively from potential hazards without additional impulse. This aspect of the study aims to identify optimal launch conditions that enhance safety and minimise risk during emergency deployments.
This paper proposes a Bayesian Network-based framework for risk assessment and probability estimation of vessel-platform allision accidents, using a novel technique that derives probabilities from incidental data. A dataset of 557 allision incidents collected from multiple open source agencies is analysed to identify causation patterns. Basic causes could only be determined for 375 incidents, with supply vessels involved in 61% of cases. Statistical analysis revealed that vessel type and the month of occurrences are significantly associated, and most incidents arose during cargo transfer operations. Fixed installation accounted for the majority of allisions with moving vessels, and human error emerged as the leading contributor (30%). Building on these insights, a Bayesian Network model is developed incorporating 42 identified causes, three causal factors and four consequence levels. Using a recent probabilistic approach, probabilities of basic causes are derived from annual allision occurrence rates. The BN model is then applied to predict annual allision probabilities and to conduct sensitivity analyses. Results show that weather-related causes and misalignment errors exert the strongest influences on accident probabilities. The methodology is transparent and holistic in providing better discernment of the causation probability of allision accidents.
