| 1. |
- Prasetyo, Fredhi Agung, 1980, et al.
(författare)
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Analysis of crack retardation effects and crack path in ship structure members on different routes
- 2013
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Ingår i: Proceedings of The 13th International Conference on Fracture (ICF13). ; , s. 1-9
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Konferensbidrag (refereegranskat)abstract
- The ship size has been rapidly increased in recent years. Consequently, many aspects of ship structural safety have been concerned, i.e. fatigue strength. Since fatigue cracks are found in the early stage of a ship’s service life, it might be that the classical cumulative fatigue rule is insufficient to consider the effects of many uncertain factors, such as variable wave environment loads. The wave load history hinges on the short-sea history. It means that the accuracy of fatigue assessment is affected by the used wave model. There are several established wave models, which could be used to simulate wave load history as in the real ocean conditions. In this paper, wave load histories of a 2800TEU container ship are generated by two different wave models. It is used for crack propagation analysis in the changing routes and trades. The result in the simulated crack propagation lives is examined and discussed.
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| 2. |
- Lin, B., et al.
(författare)
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A novel method for the evaluation of ship berthing risk using AIS data
- 2024
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Ingår i: Ocean Engineering. - 0029-8018. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of ship berthing risk, encompassing the potential for berthing collisions and unforeseen events, holds paramount importance in the realm of waterway traffic management and maritime surveillance. However, existing methods for analyzing ship berthing risk suffer from limitations in terms of timeliness, comprehensiveness and data accessibility. Therefore, this paper presents a novel approach to ship berthing risk assessment. The proposed method relies on Automatic Identification System (AIS) data and takes into consideration information related to the ship, berth, and environmental factors. It calculates crucial parameters, including the vertical distance between the ship and the berth, berthing speed, berthing angle and real-time distance between the ship and the berth, utilizing the AIS data and the berth location. Furthermore, environmental disturbance data pertaining to the ship's berthing environment is integrated with AIS data. Subsequently, we introduce the Improved Bossel Model considering Catastrophe (IBM-CC) to evaluate ship berthing risk in real-time. Finally, the proposed method was validated using actual ship berthing data and various simulation scenarios. The results demonstrate that our proposed method accurately assesses real-time ship berthing risk under diverse scenarios, offering a novel approach for the real-time and precise quantitative assessment of ship berthing risk.
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| 3. |
- Lin, B., et al.
(författare)
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An overview of scholarly literature on navigation hazards in Arctic shipping routes
- 2023
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Ingår i: Environmental Science and Pollution Research. - 0944-1344 .- 1614-7499. ; In Press
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Forskningsöversikt (refereegranskat)abstract
- Maritime transport plays a crucial role in international trade. As the number and tonnage of ships continue to increase, traditional shipping routes are becoming progressively congested. The development of Arctic shipping routes has the potential to significantly improve trade efficiency and decrease reliance on traditional shipping routes. At the same time, the harsh navigation conditions in the Arctic pose a huge challenge to ships crossing the Arctic shipping routes. To address the above issues, this paper reviews the natural, navigational environment and unique navigational modes of ships in the Arctic shipping routes. Furthermore, the navigational risks caused by factors including low temperature, sea ice, poor visibility, communication, lack of infrastructure, lack of navigational experience, lack of historical data, high collision risk, and complex navigational environment are summarized and analyzed, providing a reference for researchers and policymakers to conduct research related to Arctic shipping routes.
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| 4. |
- Mao, Wengang, 1980, et al.
(författare)
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Machine Learning to predict a ship's fuel consumption in seaways
- 2016
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Ingår i: 13th International Symposium on Practical Design of Ships and Other Floating Structures, PRADS 2016; Hotel Crowne PlazaCopenhagen; Denmark; 4 September 2016 through 8 September 2016.
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Konferensbidrag (refereegranskat)abstract
- Fatigue cracks can be observed quite frequently on today’s ocean crossing vessels. To ensure the safety of ship structures sailing in the sea, it is important to know the residual fatigue life of these damaged ship structures. In this case, the fracture mechanics theory is often employed to estimate how fast these cracks can propagate along ship structures. However, large uncertainties are always associated with the crack prediction and residual fatigue life analysis. In this study, two uncertainties sources will be investigated, i.e. the reliability of encountered wave environments connected with shipload determinations and different fracture estimation methods for crack propagation analysis. Firstly, different available codes based on fracture mechanic theory are used to compute the stress intensity factor related parameters for crack propagation analysis. The analysis is carried out for both 2D and 3D cases of some typical ship structural details. The comparison is presented to illustrate the uncertainties of crack propagation analysis related with different codes. Furthermore, it is assumed that the structural details will undertake dynamic loading from a containership operated in the North Atlantic. A statistical wave model is used to generate wave environments along recorded ship routes for different years. The uncertainties of crack growth analysis related with encountered weather environments is also investigated in the study. The comparison of these two uncertainties indicated the requirement of further development for the fracture mechanics theory and associated numerical codes, as well as the reliable life-cycle encountered weather environments.
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| 5. |
- Alexandersson, Martin, et al.
(författare)
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A comparison of ship manoeuvrability models to approximate ship navigation trajectories
- 2023
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Ingår i: Ships and Offshore Structures. - : Taylor and Francis Ltd.. - 1744-5302 .- 1754-212X. ; 18:4, s. 550-557
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Tidskriftsartikel (refereegranskat)abstract
- It is essential to describe a ship’s manoeuvrability for various applications, e.g. optimal control of unmanned surface vehicles (USVs). In this study, the capability of two recognised manoeuvrability models to predict ships’ trajectories is investigated based on both simulation and open-water experiment test data. The parameters of these models are estimated by a statistical learning method. The goodness of the two estimated models for describing a merchant ship’s manoeuvrability is first studied using her manoeuvring simulation data. Then, experimental manoeuvring tests to use a USV in open water with wind and drifting effects are used to check the conventional model identification procedures. Finally, some modifications and adjustments are proposed to improve the conventional procedures. It shows that the proposed procedures can accurately derive the ship’s manoeuvrability based on experimental data. © 2022 The Author(s).
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| 6. |
- Alexandersson, Martin, et al.
(författare)
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Analysis of roll damping model scale data
- 2021
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Ingår i: Ships and Offshore Structures. - : Taylor and Francis Ltd.. - 1744-5302 .- 1754-212X. ; 16:S1, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- Having an accurate prediction of ship roll damping is crucial when analysing roll motions. In this paper, the simplified Ikeda method (SI-method) is compared with the original Ikeda method. The methods are compared using results from a database of roll decay tests carried out on modern merchant ships and a smaller set of predictions in which the original Ikeda method was used. It was found that most of the ships in the database had dimensions outside the limits of the SI-method. Thus, the SI-method showed poor agreement with model tests outside its limits but acceptable agreement for ships within limits. It was found that the deviations were caused by extrapolation errors of the wave-damping in the SI-method. Two ways to improve the accuracy of the SI-method were proposed based on regression, which gave about the same accuracy as the original Ikeda method. © 2021 The Author(s).
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| 7. |
- Alexandersson, Martin, et al.
(författare)
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Prediction of roll motion using fully nonlinear potential flow and ikeda’s method
- 2021
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Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - : International Society of Offshore and Polar Engineers. - 1098-6189 .- 1555-1792. - 9781880653821 ; , s. 1670-1679
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Konferensbidrag (refereegranskat)abstract
- Getting the best possible accuracy with the lowest possible computational cost is an important factor in the early design stage of ships. Potential flow-based analysis presents such a solution for seakeeping analyses. The accuracy of roll motion in potential flow is however not so good, due to the large influence from vicsous roll damping, which is missing in these calculations. This paper proposes a hybrid method, as a solution to this problem, where the viscous roll damping from Ikeda’s semi-empirical method is injected into an existing 3D unsteady fully nonlinear potential flow (FNPF) method. The hybrid method is investigated using roll decay tests with the KVLCC2 test case. This investigation shows that the accuracy of simulated roll motions is significantly improved and also shows good agreement with the corresponding roll decay model tests.
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| 8. |
- Alexandersson, Martin, et al.
(författare)
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System identification of Vessel Manoeuvring Models
- 2022
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 266
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Tidskriftsartikel (refereegranskat)abstract
- Identifying the ship's maneuvering dynamics can build models for ship maneuverability predictions with a wide range of useful applications. A majority of the publications in this field are based on simulated data. In this paper model test data is used. The identification process can be decomposed into finding a suitable manoeuvring model for the hydrodynamic forces and to correctly handle errors from the measurement noise. A parameter estimation is proposed to identify the hydrodynamic derivatives. The most suitable manoeuvring model is found using the parameter estimation with cross-validation on a set of competing manoeuvring models. The parameter estimation uses inverse dynamics regression and Extended Kalman filter (EKF) with a Rauch Tung Striebel (RTS) smoother. Two case study vessels, wPCC and KVLCC2, with very different maneuverability characteristics are used to demonstrate and validate the proposed method. Turning circle predictions with the robust manoeuvring models, trained on zigzag model tests, show good agreement with the corresponding model test results for both ships. © 2022 The Author(s)
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| 9. |
- Chen, Yuhan, 1995, et al.
(författare)
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Different strategies to improve isochrone voyage optimization algorithm
- 2023
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Ingår i: Advances in the Analysis and Design of Marine Structures - Proceedings of the 9th International Conference on Marine Structures (MARSTRUCT 2023). - London : CRC Press. - 9781032506364 - 9781032506364 ; , s. 53-61
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Konferensbidrag (refereegranskat)abstract
- Voyage optimization can be essential in ship routing for autonomous and intelligent operations. Various optimization algorithms were proposed to search for optimal ship routing with minimized fuel consumption and accurate arrival time. In this paper, the Isochrone method, which is well-known for its robustness and efficiency, is further improved by different strategies to inherit the original capability of computation efficiency, and overcome its incompetence of multi-objective optimization, reliable convergence for approaching destination, and feasibility for practical navigation. Especially an innovative way of searching at a late stage is proposed, as well as a flexible evaluation of cost functions according to different optimization objectives. The improved Isochrone method can fast optimize a shipping route with multi-objective purposes, such as accurate expected time of arrival and minimum fuel consumption. The effectiveness and efficiency of different improved Isochrone methods are verified by several North Atlantic voyages collected by a chemical tanker.
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| 10. |
- Chen, Yuhan, 1995, et al.
(författare)
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Strategies to improve the isochrone algorithm for ship voyage optimisation
- 2024
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Ingår i: Ships and Offshore Structures. - 1754-212X .- 1744-5302. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- An optimisation algorithm is an essential part of voyage planning systems to achieve autonomous and intelligent operations. Various algorithms have been proposed for voyage planning to minimise fuel consumption and increase punctuality. Among them, the isochrone method has been recognised for its robustness and efficiency in voyage optimizations. This paper improves it to overcome its incompetence in multi-objective optimisation and reliable route convergence towards the destination. Five improved methods are proposed and compared, to investigate the most effective enhancing strategy to achieve robustness and practicality in real-time application. By changing search space after the middle stage of the voyage, and formulating an augmented cost function to refine search criteria according to different optimisation objectives, one improved isochrone method (named Isochrone-A*) shows more competitive capability, with potential in real-time implementations. The effectiveness and efficiency of these five improved strategies are compared using four ocean-crossing voyages collected by a chemical tanker.
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