: As environmental regulations from the International Maritime Organization (IMO) become increasingly stringent, the adoption of liquefied natural gas (LNG)-fueled vessels has accelerated, highlighting the need for safe and efficient LNG bunkering infrastructure. To ensure secure simultaneous operations (SIMOPS) during bunkering, it is essential to evaluate the hydrodynamic loads exerted on moored ships by passing vessels in confined waters. This study investigated these interactions using a computational fluid dynamics (CFD) approach. Unsteady Reynolds-Averaged Navier – Stokes simulations with an overset mesh, implemented in STAR-CCM+, were validated against benchmark model test data obtained from the International Conference on Ship Manoeuvring in Shallow and Confined Water. The numerical analysis examined surge, sway, and yaw responses of moored ships, along with free-surface elevations and pressure distributions. Parametric studies systematically explored the effects of passing ship speed, lateral clearance, water depth, and quay wall gap. The results show that hydrodynamic loads increase sharply with higher passing speeds, shallower water depth, and reduced separation distances, while quay wall effects remain relatively minor. These findings demonstrate that moored ship safety is highly sensitive to operational and geometric parameters of passing ships. This research provides quantitative insights for developing practical design and operational guidelines to ensure safe SIMOPS in ports.
Seongjin Song, D. Jung, Jae Hwan Jung· 한국해양공학회지· 0 citations
During offshore wind turbine maintenance operations, maintenance vessels typically rely on transfer gangways to achieve safe transfer of personnel from the vessel to the wind turbine. With the development of offshore wind farms toward far sea areas, working sea state conditions have become increasingly complex. In recent years, the application of large-scale active wave compensation (AWC) transfer gangways has mitigated the adverse effects of ship motions on transfer operations to a certain extent, but the problem of limited motion ranges of each gangway joint has also emerged as a prominent issue. Under complex sea state conditions, if the station-keeping position of the maintenance vessel is improperly selected, joint limit violations may occur during the gangway compensation process, thereby posing safety risks. To address the above problems, this paper develops a novel geometric-envelope-based analytical method for operational sea states and ranges that explicitly accounts for gangway joint constraints and wave-induced vessel motions to meet the safety requirements of large-scale gangways. Subject to the motion constraints of gangway joints, to ensure that the initially selected station-keeping position of the vessel satisfies the requirements for safe gangway transfer, the feasible domain and motion range of the gangway base point under different sea states are obtained. By solving for the solutions where the motion range of the base point lies entirely within the feasible domain, feasible schemes for vessel station-keeping operations under different sea states are derived. The results show that the gangway can operate safely under sea states 3 and 4 but fails under sea state 5. The allowable height difference between the transfer point and the gangway base is [−2.7 m, 8.7 m] for sea state 3 and [1.8 m, 3.5 m] for sea state 4. The operational area on the horizontal plane presents a partial ring shape, and the ring width first increases and then decreases with increasing height difference. Finally, random numerical examples are designed to demonstrate the applicability and internal consistency of the proposed analytical method.
Wen-hua Wang, Zhibin Wang, Binbin Jing et al.· Journal of Marine Science an...· 0 citations
Developing autonomous navigation systems for small fishing vessels is required to improve path-tracking robustness and mitigate severe wave-induced roll motions. This study proposes a Deep Q-Network (DQN)-based operational path planning methodology that explicitly incorporates roll motion reduction into the reward function, combining a maneuvering model with hydrodynamic analyses. Simulation results under varying wave directions and heights demonstrate that the vessel actively adjusts its heading to minimize the roll response. Based on statistical evaluations across five independent runs, the proposed model effectively reduced the average and maximum roll responses by an average of 3% and 2%, respectively, under the evaluated wave headings at a wave height of 1.0 m, while maintaining operational path tracking, despite a slight increase in the total operational path length. Future research will focus on integrating complex environmental conditions with wind and current, and performing the model test for the validation of the established DQN model.
Janghoon Seo, B. Koo, Bong-Ju Kim et al.· Applied Sciences· 0 citations
The radio altimeter is an important navigation instrument on an aircraft, capable of accurately measuring the aircraft's true height above the ground or sea to ensure safe flight. This capability is crucial for ensuring normal flight operations, especially during critical phases such as takeoff, approach, and landing. Polar terrain is complex and continually changing. The vast, endless ice fields, crisscrossing glacier crevasses, towering icebergs, and weather conditions all add significant uncertainty to air travel. In such environments, the aircraft's navigation system is particularly important as a core device to ensure flight safety. This article provides a brief overview of the aircraft radio altimeter system. Using data and observations from production flight tests, it studies the specific challenges posed by radio altimeter failures encountered during these critical validation flights. The study synthesizes these findings and proposes a relatively general troubleshooting approach to address such issues. Furthermore, the effectiveness of this method has been rigorously validated through its application in solving a complex real-world radar altimeter failure case.
Unknown authors· SAE technical paper series· 0 citations
Man Overboard (MOB) incidents require rapid rescue operations because delayed response significantly reduces the probability of victim survival. Conventional life buoys provide flotation assistance but cannot autonomously approach the victim, resulting in rescue operations that rely heavily on manual intervention by the ship's crew. This study aims to design and evaluate Varuna Buoy, an autonomous maritime rescue vehicle employing the Point-to-Point Navigation method to improve rescue response effectiveness. The proposed system integrates an ESP32 microcontroller, Neo-6M GPS receiver, HW127 digital compass, BTS7960 motor driver, modified bilge pump thrusters, and LoRa wireless communication module. Navigation is performed by combining Haversine distance estimation, azimuth bearing calculation, and differential thrust control to continuously minimize heading error while navigating toward predetermined target coordinates. The system was evaluated through ten autonomous navigation experiments conducted under two different initial heading scenarios at Ketintang Lake, Universitas Negeri Surabaya. Experimental results showed that the proposed system successfully navigated toward the target with final distances ranging from 1.27 m to 2.62 m, achieving a 70% navigation success rate based on a predefined stopping threshold of 2 m. Furthermore, the LoRa communication system achieved an average latency of 1.06 s, enabling reliable near real-time telemetry. These findings demonstrate that the proposed autonomous navigation system provides a practical and effective solution for maritime rescue applications and offers a promising foundation for future autonomous rescue vehicle development.
H. Eyrlangga· Indonesian Journal of Engine...· 0 citations
With the rapid advancement of intelligent shipping, autonomous navigation in complex and confined waters has become a critical challenge. This study aims to develop a robust autonomous navigation decision-making method to address the combined effects of tidal variations, water depth gradients, and restricted maneuvering ability in shallow waters. A digital traffic environment is constructed by fusing real-time automatic identification system (AIS) data with electronic chart display and information system (ECDIS) information and incorporating tidal effects, thereby enabling spatiotemporal situational awareness for autonomous navigation decision-making. The methodology quantitatively interprets collision avoidance rules and navigational best practices to determine optimal maneuvering thresholds for typical encounter scenarios in restricted waters. By coupling ship kinematic characteristics with bathymetric features, a three-dimensional ship domain model is developed, incorporating squat effects and under-keel clearance requirements, whereas a risk quantification algorithm accounts for water depth gradient transitions. The experimental results show that this method performs reliably in complex shallow waters. The proposed
perception-decision-execution-feedback
framework enables rapid information updates and allows the system to adapt to uncoordinated actions of target ships, handle residual errors, maintain a safe distance between ships, and reduce potential collision risk. A virtual-real integrated scenario based on AIS and ECDIS data is established to systematically validate the proposed method. It provides reliable theoretical and methodological support for the theoretical research and engineering application of autonomous navigation technology in complex shallow waters.
Kexin Xu, Yixiong He, Xingya Zhao et al.· ASCE-ASME Journal of Risk an...· 0 citations
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