In this paper, a numerical study is performed to investigate the hydrodynamic responses of a floating platform equipped with a heave plate adjacent to a partially reflective vertical wall. Based on the linear potential flow theory, a three-dimensional (3D) boundary element method (BEM) model, incorporating an image Green’s function, is developed to solve the wave radiation/diffraction problem in the presence of a partially reflective wall. The results confirm the efficacy of the heave plate, and the hydrodynamic response is governed by the reflection coefficient of the coast and the dimensionless distance between the coast and the platform (C/Wb, where C and Wb are the offshore distance and the width of the floating platform). Compared with open water conditions, the increasing of reflection coeffect suppresses surge motion but amplifies heave motion in the lower frequency region (ω < 0.5 rad/s). Moreover, the surge motion in the lower frequency range increases and the peak heave motion decreases as C/Wb increases within the range of 0.5–3 rad/s.
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.
The water exit of a floating sphere with low constant accelerations is discussed in this study. Experiments are conducted to investigate the evolution of the free surface and the hydrodynamic loads during the water exit process. Once the sphere’s bottom lifts off the mean free surface, a layer of water adheres to the sphere and is carried upward due to inertia, forming a water column beneath it. Under the influence of gravity, this water column elongates and narrows, ultimately collapsing. The qualitative influence of the vertical acceleration on the water column is discussed. To verify and validate the experimental hydrodynamic loads, the Computational Fluid Dynamics (CFD) method is utilized. The numerical results obtained from CFD are in good agreement with the experimental results, and show the viscous effect has a negligible influence on the hydrodynamic loads during the water exit of the floating sphere. Assuming potential flow, a theoretical model is proposed for the analysis of the hydrodynamic loads. This model shows that the vertical hydrodynamic loads can be approximated by the buoyancy force and the added mass force. The added mass force is related to the acceleration of the body. When the acceleration is significantly less than gravitational acceleration, the buoyancy force dominates during the early stages of the water exit process. Furthermore, in the presence of ambient waves, the wave excitation loads must also be taken into account.
Peridynamics (PD), which underpins many meshfree methods, has found widespread applications in fracture mechanics. However, its accuracy in simulating shear behavior remains limited, particularly for mixed-mode fracture problems. To address this, we propose a modified formulation of ordinary state-based PD (OSPD) that incorporates bond rotation behavior, including shear deformation and rigid body rotation (RBR). Using the peridynamic differential operator, the stress-free RBR component is identified and removed from the total displacement. The enhanced formulation is validated through classical benchmark problems, with stress intensity factors evaluated using the interaction integral method. Numerical results demonstrate excellent agreement with reference solutions from the literature and the original OSPD model, confirming the improved accuracy of the modified OSPD model. Notably, the modified model exhibits superior performance in simulating shear deformation, establishing its reliability in mixed-mode fracture analysis.
Biomimicry provides a design framework that emulates biological characteristics to exploit their functional advantages. This study presents a biomimetic-based aerodynamic assessment of wing-in-ground (WiG) configurations inspired by flying animals, including birds and mammals, using computational fluid dynamics (CFD). Three biomimetic wing models were developed by translating biological characteristics—such as body size, wing geometry, and flight behavior—into engineering design parameters relevant to near-surface flight. Numerical simulations were performed to evaluate lift, drag, lift-to-drag ratio, and trim stability under various operating conditions. The results demonstrate that each biomimetic configuration exhibits distinct aerodynamic performance consistent with its biological inspiration. The brown pelican-inspired model achieved the highest lift force, reaching approximately 68 kN, reflecting its natural adaptation for efficient lift generation near the surface. In contrast, the sugar glider-inspired model produced the lowest lift, approximately 37 kN, corresponding to its lightweight gliding characteristics. Overall, the findings confirm that biomimicry provides a rational and effective framework for preliminary WiG craft design, enabling aerodynamic performance to be systematically tailored through biologically inspired geometrical adaptations.
The instantaneous speed of diesel engines contains an abundance of information, regarding fuel supply stability and individual cylinder performance. Real-time acquisition of accurate instantaneous speed is crucial for monitoring cylinder-to-cylinder uniformity, diagnosing faults, and enabling precise speed control in marine diesel engines. However, measurement noise distorts the signal, which makes it significantly difficult to monitor the effective information in the actual operation. To address this challenge, this paper proposes a novel real-time filtering method using an extended Kalman filter (EKF). According to the characteristics of crankshaft instantaneous speed of diesel engine, a dedicated state-space model is derived. The EKF utilizes the model to perform real-time feedback and rolling optimization effectively suppressing noise. The performance of the method proposed is validated using both simulated signals and experimental data from a four-cylinder marine diesel engine. Simulation and experimental results demonstrate that the coefficient of determination R2 between the estimated and actual speed reaches 99.83%, while the signal-to-noise ratio (SNR) improves by above 10% on average across different operating conditions. This enhancement enables reliable real-time engine state monitoring and control.
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.
Deep Reinforcement Learning (DRL) offers a powerful, model-free, and data-driven approach for the navigation and control of Autonomous Surface Vessels (ASVs). The primary challenge, however, lies in the extensive training required for an agent to converge to an effective policy within a complex simulation, leading to significant computational overhead. This paper presents a multi-stage training framework that uses Transfer Learning to pass knowledge between different simulation models, resulting in a highly robust DRL controller for ASVs. The proposed framework utilizes the Deep Deterministic Policy Gradient (DDPG) algorithm to develop the data-driven controller. First, a foundational policy is efficiently learned using a simplified first-order Nomoto dynamics and second-order Nomoto dynamics, which captures the fundamental vessel dynamics. This pre-trained policy is then transferred to a complex, nonlinear Manoeuvring Modelling Group (MMG) model, significantly accelerating training convergence. Subsequently, the agent is fine-tuned within the MMG simulation with environmental disturbances. The models are evaluated on various trajectories during testing to ensure robust performance. The accuracy of the DRL controller is assessed by measuring heading error (eψ) and cross-track error (ye). A traditional Proportional-Integral-Derivative (PID) controller is implemented and compared to benchmark the DRL controller’s effectiveness, to highlight the relative advantages and limitations of each approach.
This study presents the design and development of an electric-powered workboat for application in a hydro-floating solar hybrid system, with the objective of supporting the operation and maintenance of such systems through efficient and environmentally friendly transportation. The research addresses key design challenges, including stability, maneuverability, and the integration of renewable energy sources. Computational Fluid Dynamics (CFD) simulations were employed to analyze resistance, wave patterns, and effective power, while Maxsurf software was used to evaluate vessel stability. The results indicate that the electric-powered workboat achieves a maximum speed of 21 km/h and demonstrates optimal energy efficiency at operating speeds of 18–19 km/h. In addition, assessments of noise levels, wave patterns, and environmental performance were conducted within the context of the Hydro-Floating Solar Hybrid System at Sirindhorn Dam. The findings confirm the feasibility and effectiveness of electric-powered workboats utilizing renewable energy sources, highlighting their potential contribution to sustainable waterway transportation infrastructure.
The hull structure may collapse or deform severely under fire conditions. In this study, the safety of a ship’s cabin structure under fire is evaluated using a dual-zone large eddy fire scenario simulation method and a sequential thermo-mechanical coupling analysis method. Taking a three-compartment section of a naval surface ship as a case study, a machinery room fire scenario was simulated and the fire temperature field was analyzed. Through a dedicated data interface, the full-field time-varying temperature loads were mapped to the finite element model of the compartment section, thereby achieving thermo-mechanical coupled analysis of the cabin structure. The effects of thermal expansion on the hull structure under rising fire temperatures were considered in the evaluation of the residual load-bearing capacity of the cabin. The results indicate that the residual load-bearing capacity of the compartment is closely linked to the fire development stage. Temperature not only significantly affects the mechanical properties of steel but also influences the structural load-bearing capacity through thermally stresses.
To advance shipping decarbonization, hydrogen is increasingly recognized as a viable zero-carbon fuel. Currently, a hydrogen/diesel dual-fuel medium-speed engine represents an optimal prime mover for ships. However, challenges such as the large cylinder dimensions of marine medium-speed engines and the low temperatures at the combustion chamber walls can hinder efficient flame propagation, leading to the emission of unburnt hydrogen. This not only diminishes the engine’s mechanical output but also poses significant safety risks. To address these issues, this study employs computational fluid dynamics (CFD) modelling to explore optimal diesel injection strategies that minimize unburnt hydrogen emissions in such engines. Specifically, this research examines the impacts of the diesel injection start angle, spray tilt angle, and injection duration on hydrogen combustion efficiency. The findings reveal that fine-tuning injection parameters substantially lower the fraction of unburned hydrogen. Adjusting the injection timing from 9.5°CA BTDC to 49.5°CA BTDC decreases the unburnt hydrogen fraction from 50% to 3%. Furthermore, modifying the spray tilt angle from 75.5° to 55.5° further decreases it to 2%, while shortening the injection duration from 35°CA to 34°CA achieves the lowest unburnt hydrogen fraction at just 1%. These results underscore the effectiveness of diesel injection strategies in optimizing the combustion in hydrogen/diesel dual-fuel marine medium-speed engines, offering a pathway for similar applications in the sector.