查看更多>>摘要：Design waves have been used in the past for the probabilistic assessment of wave-induced loads and responses of offshore structures. Various response-conditioning techniques have been employed to determine suitable wave episodes, typically based on linear response transfer functions. Nevertheless, extreme events are not always driven by linear phenomena but can be triggered by near-resonant effects, as in the case of the slow-drift motions of moored floating bodies. Limited research has been devoted to addressing this class of responses using response-conditioned waves (RCW). This paper presents a new approach for deriving RCWs that accounts for combined wave-and low-frequency responses. Both the response amplitude operator (RAO) and the quadratic transfer function (QTF) are employed in an iterative response-conditioning procedure. That permits the identification of appropriate short-duration wave episodes that excite resonant slow-drift motions. These wave episodes are then used in a two-step multi-fidelity design wave methodology for the probabilistic evaluation of the fully nonlinear extreme responses. The proposed approach is validated experimentally for predicting the surge excursions of a moored container ship, and good agreement is found against Monte Carlo results in irregular waves.
查看更多>>摘要：The seismic stability of reinforced soil wall is a crucial field in the geotechnical engineering field when it is situated near the coastal area and subjected to coupled action of water waves and earthquake loading. The present study investigates the seismic internal stability of waterfront reinforced soil wall under the influence of non-breaking water waves considering cohesive frictional backfill. Limit equilibrium approach based on pseudo-static method is employed for assessing the equivalent tensile reinforcement coefficient and the length of each reinforcement layer embedded within the soil wall. Design charts are prepared for different soil and wave parameters like cohesion of soil, internal friction angle of soil, horizontal and vertical seismic acceleration coefficient, pore pressure ratio, height of water on both sides of wall, height of wave, duration of wave generation and wavelength. From the investigation it is observed that length of reinforcement within the failure zone is going to reduces with increase in the internal friction and cohesion values of soil. The stability of reinforced soil wall decreases significantly with increasing the seismic acceleration in both directions thus requiring more length of reinforcement and tensile strength to maintain the stability of soil wall. Present research addresses a critical gap by exploring the combined effect of seismic and wave loading on the internal stability of waterfront reinforced soil wall. Comparison of results with previous studies along with limitations are also highlighted in the present study.
查看更多>>摘要：With the expansion of industries and the increasing fuel consumption associated with international transportation, the efficient utilization of vehicles, particularly cargo ships, has become critically important. While numerous solutions have been proposed to address this issue, many are hindered by limitations such as inaccurate or incomplete models. This study employs a semi-empirical model to precisely estimate ship resistance to waves and other environmental factors. Subsequently, route optimization is conducted using a nonlinear surrogate model, focusing on ports designated for cargo delivery. In the second phase, the Vessel Routing Problem (VPR) for ships is addressed by incorporating factors such as refueling operations, time windows, and the allocation of 1 to 3 ships to a single origin and five destinations. This problem aims to design optimal routes to minimize operational costs, travel time, and emissions, while adhering to practical constraints such as fuel capacity and port scheduling. The findings demonstrate that route optimization can achieve a reduction of more than 7% on average in fuel consumption, travel distance, and journey time. Additionally, the analysis of various cargo delivery scenarios indicates that deploying a single ship for a limited number of destinations is more efficient compared to utilizing multiple ships. However, it is anticipated that increasing the number of ships relative to a limited number of destinations could yield exceptional outcomes.
查看更多>>摘要：With the widespread application of bubble lubrication technology in transport ships, the interaction between propellers and bubble flow has received increasing attention. Based on the Reynolds averaged equation and volume fraction equation, combined with slip mesh technology, a numerical calculation model for propellers in water air mixed fluids was established. On the basis of verifying the numerical calculation method of semi immersed propeller, uncertainty analysis is conducted on the flow characteristics of KP505 propeller, and the influence of ventilation position and ventilation volume on the open water performance of the propeller is explored. Further establish linear and nonlinear relationship models between ventilation rate and KP505 propeller propulsion performance, and construct an unstable surface model to describe the impact of ventilation position moving towards the blade tip on open water performance and ventilation rate. Research has shown that the ventilation position largely determines the gas transport effects of propeller tip vortices and hub vortices. As the ventilation rate increases, the tip vortices gradually evolve into vortex rings in the far field; When the ventilation position moves towards the blade tip, the wing tip vortex becomes the main path for bubble transport, which significantly affects the propulsion performance.
查看更多>>摘要：As the basis of the auto-pilot, it is crucial to improve the control accuracy and conciseness of the course tracking control technique. In this paper, a robust adaptive predefined performance control (PPC) scheme is proposed for the problem of course tracking control of unmanned surface vehicle (USV). For the uncertain nonlinear term and unknown marine disturbance, a novel upper bounded approximating technique and relative disturbance observer (DOB) are introduced, which obviously improve the designed conciseness and the sensitivity of the course tracking controller. Combining with the PPC method, the control accuracy and the convergence velocity the tracking error are increased. Besides, the problem of the uncertain actuator gain is considered with a newly adaptive technique. For the communication load from the controller to the actuator, a dynamic event-triggered control (DETC) technique is represented, where the transmission frequency of the control orders is reduced. The uniformly bound of the closed-loop system is proved via the Lyapunov stability theory. Besides, the effectiveness and feasibility of the proposed algorithm are verified through the comparative and practical experiments.
查看更多>>摘要：Underwater gliders (UGs) are widely deployed in oceanographic observation owing to their long endurance. However, with their low speed and saw-tooth pathway, UGs will face serious challenges when operating in areas of strong currents and shallow water. To improve the environmental adaptability of UGs, we present a water-jet propulsion module (WJPM) design in this paper. Compared with propellers, the WJPM is integrated inside the streamlined shell at the stern of UGs without additional attached bodies, thus avoiding the drag generated by the thruster during the gliding process. The integrated structure, hydraulic components, and drive system design of the WJPM are presented. Using the surrogate-based optimization (SBO) method, the optimized design of the integrated flow channel is accomplished. Finally, the tank test and field experiments of the hybrid-driven underwater glider (HDUG) integrated with the WJPM are accomplished. The test results show that the WJPM can significantly improve the maneuverability and environmental adaptability of the HDUG, and the maximum speed of the gliders can reach 2.31 m/s.
Zyczkowski, MarcinKrata, PrzemyslawSzozda, Zbigniew
1.1-1.21页
查看更多>>摘要：The paper presents an innovative approach to ship route planning, with a Decision Support System (DSS) at its core. DSS integrates deterministic algorithms with safety constraints based on the Second Generation Intact Stability Criteria (SGISC), particularly the Operational Guidance (OG) implementing the SGSIC Level 2 assessment. A distinctive feature of the proposed method is the use of machine learning to create a surrogate model capable of supporting the identification of hazardous conditions and enhance adaptive decision-making. Combined with graph-based algorithms, this allows DSS to generate optimal routes that comply with the most modern stability standards. The system not only plans safe and efficient routes but also supports operational decisions by linking weather forecasts with the ship's dynamic stability. The methodology was tested using a computer model of the training vessel Horyzont II, covering failure modes such as surf-riding, parametric rolling, pure loss of stability, excessive acceleration, and synchronous rolling. The results demonstrate the system's effectiveness under various sea conditions and its potential to reduce accident risks. By integrating machine learning with route optimization and stability assessment, the proposed solution contributes to the development of intelligent navigation tools for both conventional and future autonomous vessels.
查看更多>>摘要：The caisson breakwater, known for its outstanding hydraulic performance and structural stability, has become an important coastal protection structure. The present work introduces a weir-type caisson breakwater, which features efficient energy dissipation mechanisms that can significantly enhance the utilisation of marine space. Physical model tests were conducted to evaluate and compare the hydraulic performances and wave pressure distribution of two types of weir-type caisson breakwater, impermeable and permeable, under a wide range of regular wave conditions. Notably, the free exchange of seawater between the seaward and landward sides is achieved by the perforated rear wall of the permeable structure, with three typical porosity levels. The results indicate that both types of structures exhibit excellent hydraulic efficiency in wave reflection, transmission and energy dissipation, and the permeable structure with a rear wall porosity of 20% is particularly pronounced. The different processes of wave-structure interaction lead to more improved wave pressure and wave force characteristics on the permeable structure's rear wall. Furthermore, both types of structures can be optimised under the same design parameter (B/L of approximately 0.190) based on wave properties. The findings obtained from this study have the potential to further promote the design and application of novel breakwaters.
查看更多>>摘要：The mixing mechanisms of density-stratified fluids in natural and engineered aquatic systems play critical roles in ecological and engineering management. This study investigated the mixing processes of the density fields induced by ship motion in a two-layer density-stratified environment through laboratory experiments. A controlled experimental setup comprising a plexiglass flume and a ship model system was employed, integrating particle image velocimetry and planar laser-induced fluorescence techniques to synchronously measure velocity and density fields and analyze the temporal evolution of mixing under varying ship speeds. Three distinct mixing stages were observed: pre-ship entry, dominated by molecular diffusion across a stable interface; ship passage, compressing the light fluid layer while preserving stratification; and post-ship wake, characterized by turbulent entrainment and mixing driven by wake disturbances. Results showed that higher ship speeds amplified the turbulence intensity and density change rate, prolonging fluid entrainment and mixing duration. Quantitative analysis demonstrated a linear increase in the peak density change rates and turbulence intensity with ship speed, with extended decay times, due to enhanced wake energy. Furthermore, the turbulence decay followed an exponential power law, reflecting energy dissipation modulated by stratification. These findings provide valuable theoretical insights for optimizing vessel operations and mitigation measures in stratified waterways.
查看更多>>摘要：The design of new ships is a process that requires knowledge of several aspects of naval architecture and marine engineering. During the early design stage, one of the first issues that designers should face is the preliminary estimation of the vessel's main dimensions, respecting the desiderata of the ship owner. Therefore, it is relevant to provide designers with suitable tools that may help estimate the principal dimensions, consider conventional methods and investigate the applicability of modern techniques based on machine learning. The present work focuses on applying different regression techniques to a database of RoPax vessels, finding mathematical instruments to evaluate the ship's main dimensions. Conventional regression techniques are first investigated here to compare with the existing formulae provided by other databases. The study is then extended by applying multiple linear regression and forest tree algorithms, seeking an improvement of conventional formulations available in the literature. The results highlight how the most modern regression techniques allow for better coverage of the design space, allowing the use of more than one input to obtain the final dimensions.
NETL
NSTL
Elsevier