This study is an investigation into cyberattacks on autonomous vessels, focusing on previous “real-world” cyberattacks and their consequences. The future of commercial and noncommercial shipping is moving toward autonomous vessels. Autonomous ships can provide significant financial and logistical benefits for shipping companies and their stakeholders. However, these vessels suffer from shortcomings concerning cybersecurity. Previous cyberattacks are investigated to understand how the command system of an autonomous ship is infiltrated, the consequences of an attack, and the shortfalls of the security of the vessel. This aim is achieved via a literature review concerning cyberattacks on autonomous vessels with a focus on sources indicating how the security systems of previous vessels were breached, the consequence of said cyberattacks, and their capability for recovery. Sources used include Web of Science, Scopus, Google Scholar, Mendeley, Zotero, SciFinder, broadsheet, and newspaper articles. The results of the literature review showed that autonomous vessels are significantly vulnerable to cyberattacks. Autonomous vessels were determined to have relatively easy-to-breach security systems. In most cases, the consequences of a cyberattack had a negative financial impact, a loss of cargo, and a potential breach of oceanic airspace, resulting in military action. The vessels analyzed were left “dead in the water” until they were recovered, and after a severe attack, the affected shipping company servers suffered potential weeklong incapacitation. This study also aims to fill the gaps in the transport industry and maritime market concerning the security of autonomous vessels and viable recovery procedures.

Researchers often explore metaheuristic algorithms for their studies. These algorithms possess unique features for solving optimization problems and are usually developed on the basis of real-world natural phenomena or animal and insect behavior. Numerous fields have benefited from metaheuristic algorithms for solving real-world optimization problems. As a renewable energy source, offshore wind energy is a rapidly developing subject of research, attracting considerable interest worldwide. However, designing offshore wind turbine systems can be challenging because of the large space of design parameters and different environmental conditions, and the optimization of offshore wind turbines can be extremely expensive. Nevertheless, advanced optimization methods can help to overcome these challenges. This study explores the use of metaheuristic algorithms in optimizing the design of wind turbines, including wind farm layout and wind turbine blades. Given that offshore wind energy relies more heavily on subsidies than fossil fuel-based energy sources, lowering the costs for future projects, particularly by developing new technologies and optimizing existing methods, is crucial.

Wave breaking at the bow of a high-speed ship is of great importance to the hydrodynamic performance of high-speed ships, accompanied by complex flow field deformation. In this study, the smoothed particle hydrodynamics (SPH) method under the Lagrange framework is adopted to simulate the breaking bow wave of the KCS ship model. In order to improve the computational efficiency, the inflow and outflow boundary model is used to establish a numerical tank of current, and a numerical treatment for free surface separation is implemented. Numerical simulations are carried out at Fr = 0.35, 0.40, 0.5, 0.6, and different types of wave breaking such as spilling breaker, plunging breaker, and scars are captured by the SPH method, which is consistent with the experimental result, demonstrating that the present SPH method can be robust and reliable in accurately predicting the breaking bow wave phenomenon of high-speed ships. Furthermore, the wave elevation and velocity field in the bow wave region are analyzed, and the evolution of the bow wave breaking is provided.

To explore the water entry flow and impact load characteristics of northern gannets, we conducted water entry experiments using a northern gannet’s head model based on three-dimensional (3D) printing and several cone models under different Froude numbers. A high-speed camera was used to capture flow images, and an inertial measurement unit (IMU) was used to record the water entry impact loads. The results indicate that the geometric topology of the model considerably influenced the water entry flow and impact load. Specifically, the northern gannet’s head model created a smaller water entry splash crown, cavity geometry, and impact load compared with the cone models of similar sizes.

The present study investigates the effect of moorings on hybrid floating breakwaters of different configurations based on potential flow theory. The mooring analysis is performed for the regular wave incidence for five different shapes of hybrid floating breakwaters, namely, rectangular, box, H, Π, and trapezoidal, integrated with a single J-shaped oscillating water column (OWC). The mooring lines are considered to be nonlinear catenary sections that are analysed for open mooring and cross mooring configuration. The hydrodynamic analysis is performed using Ansys-AQWA and the effectiveness of the moorings is evaluated in terms of the mooring line tension and the floating structure’s motion response, and comparisons are made for the influence of different mooring configurations and the implications of changing the design of the hybrid floating breakwater. The regular gravity wave frequency range is taken into consideration and the hydrodynamic properties are reported for the entire range of regular wave frequencies. Additionally, for a few chosen wave frequencies the analysis of structural forces and moment is performed for long and short waves. The study suggests that a hydrodynamically stable hybrid floating structure integrated with an oscillating water column can provide good and effective wave energy conversion and wave attenuation. Thus, with the help of the findings of the present study, the researchers will be able to examine the stability of hybrid floating breakwater structures under the action of regular waves with normal incidence.

Addressing the ongoing challenge of enhancing propulsion efficiency in rim-driven thrusters (RDTs), a novel energy-saving appendage was designed to mitigate energy dissipation and improve efficiency. Computational fluid dynamics was utilized to examine the disparities in open-water performance between RDTs with and without this appendage. The Reynolds-Averaged Navier-Stokes equations were solved using the Moving Reference Frame approach within the established STAR-CCM+ software. The accuracy of these methodologies was confirmed through a comparison of numerical simulations with experimental data. A meticulous analysis evaluated the alterations in propulsion efficiency of RDTs pre- and post-appendage integration across various advance coefficients. Additionally, a comprehensive assessment of thrust and torque coefficient distributions facilitated a comprehensive understanding of the appendage’s energy-saving potential. Results demonstrated that the new appendage diminishes the diffusive wake behind the rotor disk, fostering a more uniform flow distribution. A notable reduction in the low-pressure zone on the rotor blade’s thrust side was observed, accompanied by an elevation in the high-pressure area. This generated a distinct pressure disparity between the blade’s thrust and suction sides, mitigating the low-pressure region at the blade tip and reducing the likelihood of cavitation. The manuscript further elucidates the rationale behind these alterations, providing detailed insights into flow field dynamics.

This study analyzes the hydrodynamic performance of an H-shaped pile-restrained composite breakwater integrated with a pair of horizontal plates placed on the seaside and the leeside of the breakwater. The wave interaction with the H-shaped breakwater is examined by analyzing the wave reflection, transmission, and dissipation coefficients. Additionally, the horizontal wave force coefficients are evaluated to analyze the effectiveness of the horizontal plates when integrated with the main structure. The primary structural parameters directly affect the performance of the composite breakwater and are varied within the feasible range of nondimensional wave numbers, relative spacings, and incident wave angles. This study presents a comparative analysis of the arrangement of the horizontal plates in terms of spacing and inclinations inward and outward to the breakwater using a multidomain boundary element method (BEM). The variation of the structural parameters proposes suitable dimensions for integrated H-shaped breakwater with horizontal plates that provide optimal performance in shallow and deep-water regions. The optimum plate porosity, dimensions of the H-shaped structure, inclinations, and spacing between the plate and breakwater are thoroughly discussed. This study shows that impermeable plates are the excellent means to control the wave force in the intermediate water depth regions than in deep-water regions at resisting wave force. The wave force coefficient on the breakwater is significantly larger than that on the seaside plates. Interestingly, inward-inclined plates perform most efficiently at angles greater than 5°, except in deep-water regions where horizontal plates perform better. In addition, this study noted that regardless of water depth, the outward-inclined plates are the least effective in reflecting the incident wave energy. This study will help plan the layout of suitable composite structures for efficient near-shore and offshore harbor protection according to the site criteria and environmental conditions.

The rotation of a ship’s propeller can accelerate the water flow around it, which puts pressure on seabed particles. Continuous pressure on the seabed can significantly trigger erosion and sedimentation of coastal waters. Considering the impact that can be caused, the ship’s propeller rotation limit needs to be determined to avoid damage to the aquatic ecosystem. This research determines the threshold of ship propeller rotation based on the water flow velocity characteristic. Research has been carried out at the Hydrodynamics Laboratory on several variations of propeller rotation R_rmp (r/min) and water depth using empirical approaches, numerical simulations, and scale model experiments. Analysis based on general standard criteria for erosion and sedimentation shows that a propeller with a diameter (D_p) of 1.5 m is safe for propeller rotation at 25 r/min at all water depths. Then, the propeller rotation of 75 r/min is safe for a distance between the propeller axis and the bottom of the water equal to D_p. Meanwhile, rotation at 120 r/min is safe at a minimum distance of 1.5 D_p, and 230 r/min is safe for a minimum distance of 2.0 D_p. The propeller rotation threshold criteria are essential to determining the new under-keel clearance for environmentally friendly ship operations. Threshold values vary based on seabed particle type and water depth.

The design of a ship is a process facilitated by different parallel departments. Specialists from various disciplines jointly work on a project, eventually covering the entire process. Though simultaneously, these disciplines are often subject to a hierarchy, either clearly defined or dictated by necessity. Within these branches, despite a growing interest in enhancing the comfort on board ships, noise and vibration design is among the most sacrificed. Compared to hydrodynamic or structural modifications, efforts devoted to improving vibrational comfort are generally slightly impactful and costly. Consequently, these improvements are often relegated to the final stages of the design procedure. The underestimation of noise and vibrational comfort design can generate serious, unexpected issues emerging only in the advanced phases of the ship’s life, and post-construction interventions are often needed. This case is exemplified in the current study, where the crew of the research vessel Mintis, a catamaran-type hull, reported discomfort in the navigation wheelhouse. A measurement campaign was set up to assess the complaints of the operating personnel regarding the high vibrational levels. Subsequent to the measurements, a numerical simulation, specifically comprising a modal analysis, was conducted to investigate the nature of the disturbance and distinguish the underlying mechanism at its origin. This paper meticulously presents and discusses the strategy undertaken to analyze and solve the vibrational problem encountered on board, with particular attention to the criteria and the modeling considerations adopted.

Flexible risers are crucial pieces of equipment for moving output fluids from wells to platforms during the extraction of oil and gas from deep-sea resources. One of the causes of collapse in these pipes is the high hydrostatic pressure applied to risers in deep water. The innermost layer of a riser, known as the carcass layer, plays a critical role in resistance to external pressure. In this study, we investigated the collapse (nonlinear buckling) of a riser under external pressure, and a novel design based on the structure of a beetle’s exoskeleton was used to increase the load capacity of the carcass layer. This type of beetle skeleton is constructed in such a way that it creates strong connections among the various parts of the external skeleton to considerably enhance strength against external pressure while allowing necessary movements. To assess the performance of the design in comparison with the original design, we examined the nonlinear buckling of the new structure under external pressure. Through genetic algorithm optimization, design parameters were obtained, and the maximum strength before collapse was determined. Results show that the critical pressure in the new design substantially increases relative to that in the original design.

The sloshing in a tank with a specific geometric shape containing fluid was modeled numerically to reduce its effects by applying a porous medium to the tank wall. The thickness and position of the porous layer and the geometric shape of the tank were investigated as the main parameters to select an optimal approach to reduce the effects of sloshing. Different fluid tank filling percentages (H_w/H_tot) were evaluated. Results indicate that performance at H_w/H_tot = 0.33 and two tank modes with and without a porous environment layer have the greatest impact on reducing sloshing. A thickness of 30 cm and placement on the side walls are determined to be the ideal thickness and location of the porous layer. A porous layer with a thickness (t) relative to the tank length at the middle (L_m), t/L_m= 0.1 applied to the side walls of the tank effectively reduces the pressure by 65%. This study provided suggestions for the aspect ratio of a chamfered tank designed against sloshing.

The wave interaction with stratified porous structure combined with a surface-piercing porous block in a stepped seabed is analysed based on the small amplitude wave theory. The study is performed to analyse the effectiveness of partial porous structure in increasing the wave attenuation in the nearshore regions consisting of stratified porous structures of different configurations using the eigenfunction expansion method and orthogonal mode-coupling relation. The hydrodynamic characteristics such as wave reflection coefficient, transmission coefficient, dissipation coefficient, wave force impact and surface elevation are investigated due to the presence of both horizontally and vertically stratified porous structures. The effect of varying porosity, structural width, angle of incidence, wavelength and length between the porous block and stratified structure is examined. The numerical results are validated with the results available in the literature. The present study illustrates that the presence of the stratified structure decreases wave transmission and efficient wave attenuation can also be easily achieved. The wave force acting on stratified structure can be decreased if the structure is combined with wider surface-piercing porous blocks. Further, the presence of stratified porous structure combined with porous block helps in creating a tranquil zone in the leeside of the structure. The combination of vertical and horizontal stratified porous structure with surface-piercing porous block is intended to be an effective solution for the protection of coastal facilities.

This paper is concerned with a study of wave propagation due to scattering of an obliquely incident wave by a porous vertical plate with non-uniform porosity which is completely submerged in water of finite depth. The problem is formulated in terms of a Fredholm integral equation of the second kind in difference in potential across the barrier. The integral equation is then solved using two methods: the boundary element method and the collocation method. The reflection coefficients, transmission coefficient, and amount of energy dissipation are evaluated using the solution of the integral equation. It is observed that non-uniform porosity of a barrier has significant effect on the reflection of waves and energy dissipation compared to a barrier with uniform porosity. The dissipation of the wave energy by a non-uniform porous barrier can be enhanced and can be made larger than that of a barrier with uniform porosity, by suitable choice of non-uniform porosity distribution in the barrier. This has an important bearing on reducing the wave power and thereby protecting the shore line from coastal erosion. Also, an obliquely incident wave reduces reflection and dissipation while increasing transmission of wave energy as compared to a normally incident wave.

The behavior of a chemical tanker (CT) in extreme waves was discussed in detail, that is, in terms of rigid body heave and pitch motions, vertical bending moments (VBMs) amidships, green water, and slamming impacts through the analysis of the experimental data from model tests. Regular wave tests conducted for two wave steepness showed that the increase in wave steepness caused the increase in the asymmetry between hogging and sagging moments and the contribution of green water on deck to the decrease in vertical wave bending moments. Random uncertainty analysis of statistical values in irregular wave tests with various seeds revealed slight experimental uncertainties on motions and VBMs and slightly higher errors in slamming pressure peaks. With the increase in forward speed, experimental uncertainty on slamming pressures at the bow increased. Breather solutions of the nonlinear Schr?dinger equation applied to generate tailored extreme waves of certain critical wavelengths showed a good performance in terms of ship response, and it was further verified for the CT.

Challenges associated with path-following control for commercial displacement vessels under varying loading and draught conditions are addressed in this study. Adaptive control with the adaptation law technique is used to mitigate the adverse effects of uncertainty and unmodeled parameters on path-following, particularly in the presence of ocean disturbances. The proposed adaptive path-following control estimates the effect of unmodeled parameters and dynamic behavior by the state estimator. Then, the proposed structure adjusts the gains of the L1 controller. The indirect L1 control is used in the main controller, and stability proof is provided based on Lyapunov theory. The adaptive path-following control is proposed for the underactuated-very large crude carrier 2 (VLCC2) as a benchmark vessel. Hydrodynamic coefficients for full load and ballast conditions are determined using empirical formulas. Simulations are conducted in these loading conditions, accounting for a two-knot ocean current, two-knot wind, and waves up to sea state 5. Results highlight that the fixed structure, such as the PID controller, fails to deliver satisfactory performance due to significant variations in the vessel’s mass, inertia, and draught. By contrast, the adaptive path-following control demonstrates robustness under varying conditions by effectively estimating the vessel’s unmodeled parameters.

With the increasing utilization of liquefied natural gas (LNG) as a marine fuel, the safety and reliability of shore-based LNG bunkering operations have become vital concerns. Human factors are crucial to the successful execution of these operations. However, predicting human reliability in such complex scenarios remains challenging. This paper focuses on the prediction of human reliability analysis (HRA) for shore-based LNG bunkering operations on tanker ships to address the aforementioned gap. Practical approaches to predicting HRA under the success likelihood index method (SLIM) and an improved Z-numbers approach are both adopted in this paper. SLIM provides a powerful tool to calculate human error, while the improved Z-numbers can address uncertainty and improve the reliability of qualitative expert judgments. Results show that the reliability of shore-based LNG bunkering operations is 0.861. In addition to its robust theoretical contribution, this research provides substantial practical contributions to LNG ship owners, ship superintendents, safety inspectors, and shore-based and ship crew for enhancing safety at the operational level and efficiency of shore-based LNG bunkering operations.

This study presents an optimisation-based approach for determining controller gains in ship path-following under varying sea states, wave, and wind directions. The dynamic Line of Sight approach is used to regulate the rudder angle and guide the Esso Osaka ship along the desired path. Gains are optimised using a genetic algorithm and a comprehensive cost function. The analysis covers a range of wave attack directions and sea states to evaluate the controller performance. Results demonstrate effective convergence to the desired path, although a steady-state error persists. Heading and rudder angle performance analyses show successful convergence and dynamic adjustments of the rudder angle to compensate for deviations. The findings underscore the influence of wave and wind conditions on ship performance and highlight the need for precise gain tuning. This research contributes insights into optimising and evaluating path-following controllers for ship navigation.

The path-following control design for an autonomous underwater vehicle (AUV) requires prior full or partial knowledge about the mathematical model defined through Newton’s second law based on a geometrical investigation. AUV dynamics are highly nonlinear and time-varying, facing unpredictable disturbances due to AUVs operating in deep, hazardous oceanic environments. Consequently, navigation guidance and control systems for AUVs must learn and adapt to the time-varying dynamics of the nonlinear fully coupled vehicle model in the presence of highly unstructured underwater operating conditions. Many control engineers focus on the application of robust model-free adaptive control techniques in AUV maneuvers. Hence, the main goal is to design a novel salp swarm optimization of super twisting algorithm-based secondorder sliding mode controller for the planar path-following control of an AUV through regulation of the heading angle parameter. The finite time for tracking error convergence in the horizontal plane is provided through the control structure architecture, particularly for lateral deviations from the desired path. The proposed control law is designed such that it steers a robotic vehicle to track a predefined planar path at a constant speed determined by an end-user, without any temporal specification. Finally, the efficacy and tracking accuracy are evaluated through comparative analysis based on simulation and experimental hardware-in-loop assessment without violating the input constraints. Moreover, the proposed control law can handle parametric uncertainties and unpredictable disturbances such as ocean currents, wind, and measurement noise.

This work proposes an innovative approach to evaluate the functional characteristics of a heterogeneous underwater wireless acoustic sensor network (UWASN) using a stochastic model and the network connectivity criterion. The connectivity criterion is probabilistic and considers inherently distinct groups of parameters: technical parameters that determine the network function at specific levels of the communication stack and physical parameters that describe the environment in the water area. The proposed approach enables researchers to evaluate the network characteristics in terms of energy efficiency and reliability while considering specific network and environmental parameters. Moreover, this approach is a simple and convenient tool for analyzing the effectiveness of protocols in various open systems interconnection model levels. It is possible to assess the potential capabilities of any protocol and include it in the proposed model. This work presents the results of modeling the critical characteristics of heterogeneous three-dimensional UWASNs of different scales consisting of stationary sensors and a wave glider as a mobile gateway, using specific protocols as examples. Several alternative routes for the wave glider are considered to optimize the network’s functional capabilities. Optimal trajectories of the wave glider’s movement have been determined in terms of ensuring the efficiency and reliability of the hybrid UWASN at various scales. In the context of the problem, an evaluation of different reference node placement was to ensure message transmission to a mobile gateway. The best location of reference nodes has been found.

The movements and intentions of other ships can be determined by gathering and examining ship sound signals. The extraction and analysis of ship sound signals fundamentally support the autonomous navigation of intelligent ships. Mel scale frequency cepstral coefficient (MFCC) feature parameters are improved and optimized to form NewMFCC by introducing second-order difference and wavelet packet decomposition transformation methods in this paper. Transforming sound signals into a feature vector that fully describes the dynamic characteristics of ship sound signals and the high- and low-frequency information solves the problem of the inability to transport ordinary sound signals directly as signals for training in machine learning models. Radial basis function kernels are used to conduct support vector machine classifier simulation experiments. Five types of sound signals, namely, one type of ship sound signals and four types of interference sound signals, are categorized and identified as classification targets to verify the feasibility of the classification of ship sound signals and interference signals. The proposed method improves classification accuracy by approximately 15%.