| 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). ; 6, 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)
-
A novel method for the evaluation of ship berthing risk using AIS data
- 2024
-
Ingår i: Ocean Engineering. - 0029-8018. ; 293
-
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)
-
An overview of scholarly literature on navigation hazards in Arctic shipping routes
- 2024
-
Ingår i: Environmental Science and Pollution Research. - 0944-1344 .- 1614-7499. ; 31:28, s. 40419-40435
-
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.
-
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)
-
A comparison of ship manoeuvrability models to approximate ship navigation trajectories
- 2023
-
Ingår i: Ships and Offshore Structures. - : Taylor and Francis Ltd.. - 1744-5302 .- 1754-212X. ; 18:4, s. 550-557
-
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)
-
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)
-
Prediction of roll motion using fully nonlinear potential flow and ikeda’s method
- 2021
-
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)
-
System identification of a physics-informed ship model for better predictions in wind conditions
- 2024
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 310
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Tidskriftsartikel (refereegranskat)abstract
- System identification offers ways to obtain proper models describing a ship’s dynamics in real operational conditions but poses significant challenges, such as the multicollinearity and generality of the identified model. This paper proposes a new physics-informed ship manoeuvring model, where a deterministic semi-empirical rudder model has been added, to guide the identification towards a physically correct hydrodynamic model. This is an essential building block to distinguish the hydrodynamic modelling uncertainties from wind, waves, and currents – in real sea conditions – which is particularly important for ships with wind-assisted propulsion. In the physics-informed manoeuvring modelling framework, a systematical procedure is developed to establish various force/motion components within the manoeuvring system by inverse dynamics regression. The novel test case wind-powered pure car carrier (wPCC) assesses the physical correctness. First, a reference model, assumed to resemble the physically correct kinetics, is established via parameter identification on virtual captive tests. Then, the model tests are used to build both the physics-informed model and a physics-uninformed mathematical model for comparison. All models predicted the zigzag tests with satisfactory agreement. Thus, they can indeed be considered as being mathematically correct. However, introducing a semi-empirical rudder model seems to have guided the identification towards a more physically correct calm water hydrodynamic model, having lower multicollinearity and better generalization.
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| 9. |
- Alexandersson, Martin, et al.
(författare)
-
System identification of Vessel Manoeuvring Models
- 2022
-
Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 266
-
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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| 10. |
- Chen, Yuhan, 1995, et al.
(författare)
-
An Isochrone-Based Predictive Optimization for Efficient Ship Voyage Planning and Execution
- 2024
-
Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; In press
-
Tidskriftsartikel (refereegranskat)abstract
- A voyage optimization algorithm is an essential component in a ship’s routing concerning safety, energy efficiency, arrival punctuality, etc. In this study, predictive optimization is integrated with an Isochrone-based voyage optimization algorithm for energy-efficient sailing. Different waypoints generation and grid partition strategies in search spaces are proposed to achieve smooth convergence toward the destination, and costs ahead of the current sailing time stages are estimated in the cost function to avoid the local suboptimization. Based on these measures, this paper introduces the Isochrone-based predictive optimization (IPO) method that can achieve enhanced and robust performance in real-time multi-objective voyage optimization. The unrealistic routes with abrupt turns that occur in the traditional Isochrone and graph search methods are avoided. The IPO method can suggest energy-efficient routes in diverse sailing environments, while complying with punctuality requirements in voyage planning. Meanwhile, it requires a few computational resources that enable online and real-time adjustment during voyage execution, adapting to dynamic sailing environments. Its efficiency and effectiveness are demonstrated by six case study voyages from a chemical tanker with full-scale measurements, and further compared with other widely used voyage optimization methods. The results show that the proposed method can provide smooth routes with subtle turns with 5% fuel reduction on average for all case voyages, with around 40 seconds runtime.
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| 11. |
- Chen, Yuhan, 1995, et al.
(författare)
-
Different strategies to improve isochrone voyage optimization algorithm
- 2023
-
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
-
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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| 12. |
- Chen, Yuhan, 1995, et al.
(författare)
-
Strategies to improve the isochrone algorithm for ship voyage optimisation
- 2024
-
Ingår i: Ships and Offshore Structures. - 1754-212X .- 1744-5302. ; In Press
-
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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| 13. |
- Daiyong, Zhang, 1991, et al.
(författare)
-
A comparison of ship maneuverability models to approximate ship navigation trajectories
- 2021
-
Ingår i: Proceedings of The 6th International Conference on Ships and Offshore Structures (ICSOS 2021). ; , s. 1-9
-
Konferensbidrag (refereegranskat)abstract
- For optimal control of unmanned surface vehicles (USVs), it is essential to understand the maneuverability of the USVs. In this study, two well-recognized maneuverability models are compared for their capability to predict the trajectories of a simulation and an experiment ship models. The parameters of these maneuverability models are estimated by a statistical learning method. The goodness of the two models for describing a simulated merchant ship’s maneuverability is firstly studied using her simulated trajectories. Finally, the capability of those modelling methods is further investigated using experimental tests of a ship model at an open lake. The experimental tests can model a bit “real” sailing conditions to a USV with wind and drift effects. Finally, some modification and improvement techniques are suggested to accurately derive her maneuverability model based on experimental data.
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| 14. |
- Daiyong, Zhang, 1991, et al.
(författare)
-
Sensitive analysis of voyage optimization algorithms for ship voyage planning
- 2021
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; , s. 2772-2779
-
Konferensbidrag (refereegranskat)abstract
- Voyage optimization systems search for a ship's potential sailing area by estimating ETA, fuel consumption, fatigue, etc., along sailing area. However, the reliability of a voyage optimization system may be affected by different uncertainties, such as weather forecast input, ship performance models, and parameter settings in optimization algorithms. This study investigates voyage planning uncertainties associated with parameter setting of four optimization algorithms. Half years’ full-scale measurement of a containership sailing in the North Atlantic is used to study the sensitivities of voyage optimization due to parameter settings of the algorithms. Important parameter settings are summarized from the sensitivity analysis.
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| 15. |
- Dang, Z., et al.
(författare)
-
Prediction of fatigue crack propagation in bulb-flat by experimental and numerical method
- 2018
-
Ingår i: Chuan Bo Li Xue/Journal of Ship Mechanics. - 1007-7294. ; 22:7, s. 873-881
-
Tidskriftsartikel (refereegranskat)abstract
- The fatigue crack propagation in the bulb-flat, which is widely used in ship and bridge engineer ing, is one of the basic parameters for structures'fatigue life prediction. In this paper, the shape of a three dimensional surface crack in full-scale bulb-flat was measured and estimated by Nominalization Crack Opening Displacement (NCOD) method. Then the obtained crack shape was used to predict the fatigue crack propagation in the bulb-flat based on the two dimensional Paris formula and the Linear Finite Element Analysis (LFEA) method. Finally, the predicted fatigue crack propagation was verified by the full-scale fa tigue test on a typical ship structure in detail. This method proposed in this paper may provide reference to the definition of failure criterion of bulb-flat.
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| 16. |
- Eriksson, Leif, 1970, et al.
(författare)
-
EONav - Copernicus Data in Support of Maritime Route Optimization
- 2018
-
Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS). ; 2018-July, s. 5606-5609
-
Konferensbidrag (refereegranskat)abstract
- The EONav ship routing service uses near real time observations of ocean surface currents, waves, wind and sea ice conditions, in conjunction with forecasts from numerical weather and ocean models, to plan the optimal route for a vessel. Products from the Copernicus Marine Environment Monitoring Service (CMEMS) and several national weather services are used together with in-house products developed for Synthetic Aperture Radar (SAR) data from satellites such as Sentinel-1, Radarsat-2 and COSMO-SkyMed. A novel data selection algorithm automatically ranks the various data sets and combines them to provide the most reliable met-ocean information. A sail plan optimized e.g. to reduce fuel consumption is determined based on the met-ocean information and is communicated to the ships to assist captains in selecting the best route and speed pattern to their destination.
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| 17. |
- Fu, Thomas, et al.
(författare)
-
Report from ISSC Technical Committee I.1 - Environment
- 2018
-
Ingår i: Proceedings of the 20th International Ship and Offshore Structures Congress (ISSC 2018). - 9781643680545 ; 3, s. 3-12
-
Konferensbidrag (refereegranskat)abstract
- Concern for descriptions of the ocean environment, especially with respect to wave, current and wind, in deep and shallow waters, and ice, as a basis for the determination of environmental loads for structural design. Attention shall be given to statistical description of these and other related phenomena relevant to the safe design and operation of ships and offshore structures. The committee is encouraged to cooperate with the corresponding ITTC committee.
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| 18. |
- Gracia, Luis De, et al.
(författare)
-
A study on the difference in wave statistics based on storm model for the ship structural assessment
- 2020
-
Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. ; 2A-2020
-
Konferensbidrag (refereegranskat)abstract
- Ocean-going vessels are under the continuous influence on the effect of the weather, e.g. wind, waves, ocean currents. Since the weather conditions are random in nature, there are situations where the shipmaster changes the ship speed or/and heading of the original sailing path to avoid harsh weather conditions according to his judgment, experience and/or using voyage optimization systems (e.g. weather routing systems). However, ship operators hardly prioritize the ship fatigue routing in their operations. It is preferable to consider the effect of different wave environment due to ship operation in the design process to make a more rational ship design of the structural members. In this study, sailing paths are planned, adopting voyage optimization in order to reduce the probability of encountering severe sea conditions and the minimization of the fatigue accumulation in ship structures. Short-sea sequences are generated by a statistical wave storm model. The storm profiles are determined by using the cumulative frequency of short-seas which are experienced in the different voyages optimized by the algorithm. The influence of the difference in short-seas encountered by the target ship following the optimized voyages on the cumulative damage is demonstrated by a container vessel, which also considers a weather routing system in her operations. Full-scale measurement data for two years' voyages are considered for the verification. The benefits of using voyages optimization systems focus on reducing fatigue damage to mitigate the risk of structural failure is discussed.
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| 19. |
- Gracia, Luis De, et al.
(författare)
-
Comparative Study on Two Statistical Wave Load Models and Their Application to Fatigue Assessment
- 2019
-
Ingår i: Annual meeting / The Japan Society of Naval Architects and Ocean Engineers. ; Vol.28
-
Konferensbidrag (refereegranskat)abstract
- The shipbuilding industry has been under constant development. Nowadays, bigger and lighter ships are sailing worldwide shipping routes, and one of the crucial structural problems to be challenged is the fatigue damage to the hull structure. Ships structures should be safe and reliable against different kinds of fractures e.g., brittle fracture, fatigue failure, buckling, plastic collapse, among others. The corrosion, welding defects, material properties, wave load computations, etc, generally include large uncertainties in the ship fatigue analysis. In particular, large uncertainties are associated with the difference of the provided from actual wave environments encountered by a ship. These uncertainties may lead to fatigue cracks initiated much earlier than expected. The wave scatter diagrams, generally provided by the class rules guidelines, indicate the long-term probability distribution of waves at a specific sea area. Therefore, the actual wave environment encountered by individual ships may be not consistent with that provided by the class rule guidelines that are unlikely to consider operational conditions for individual ships. Therefore, a reliable description of the wave environments encountered by the ship during her service life is essential for the accurate fatigue assessment of ship structures. Statistical wave load models have been developed to model wave environments along ship arbitrary routes based on diverse wave data, e.g., onboard observations, satellite measurements, buoy data, and reanalysis data, etc. The wave information generated by the wave models could be useful for ship fatigue assessment and extreme loading predictions. This study presents two statistical wave models, one is based on wave scatter data extracted from reanalysis dataset along ship routes and the other is based on the Spatio-temporal correlation of wave from reanalysis and satellite measurements. A series of full-scale measurement data collected in a 2800TEU container carrier, when sailing in the North Atlantic during 2008, are used to validate the capabilities to describe the statistical properties of the wave conditions generated by the wave models. The stochastic nature and the statistical characteristics of sea states generated from the two wave models are compared with oceanographic information extracted from oceanographic reanalysis database data, actual onboard measurement and that provided by classification society guidelines for ship fatigue assessment. Finally, to present the applicability of the statistical wave models for the fatigue assessment of ship structures a simplified ship structural detail is selected. Based on the sea environments and stress histories generated by the two models, both the conventional high cycle fatigue life prediction and crack propagation method are demonstrated and compared with the results obtained from measured stress in the same containership.
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| 20. |
- Gracia, Luis De, et al.
(författare)
-
Comparison of two statistical wave models for fatigue and fracture analysis of ship structures
- 2019
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; Vol.187
-
Tidskriftsartikel (refereegranskat)abstract
- Ocean crossing ship structures are continuously suffering from wave loads when sailing at sea. The wave loads cause large variation of structural stresses, leading to fatigue accumulation in ship structures. For the fatigue life prediction of ship structures, it is important to obtain both the long-term distribution and the time history of wave-induced loads. An essential step is to get reliable wave statistics and accurate description of the stochastic nature of sea state along a ship’s sailing routes during her service time. Generally, the wave statistics are pro- vided by the classification societies as a joint probability of significant wave height and mean wave period, also known as wave scatter diagram. In addition, different statistical wave models have been developed to describe wave environments along arbitrary shipping routes based on different data sources, e.g., hindcast data, satellite measurements, buoys, etc. In this paper, two statistical wave models based on hindcast data and satellite wave measurements are briefly introduced and compared with the wave measurements carried out by onboard radar. Both of the wave models are then used to generate the wave environments along given shipping routes. The effectiveness of the wave models is demonstrated by comparing the stochastic nature and the statistical char- acteristics of simulated sea state histories with those of the source oceanographic data. Finally, an application of the wave model to the fatigue assessment is presented.
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| 21. |
- Gracia, Luis De, et al.
(författare)
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Influence of different wave load sequence models on fatigue life prediction of ship structures based on fracture mechanics approach
- 2016
-
Ingår i: Proceedings of the ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering (OMAE2016) in Busan, Korea, June 19-24, 2016. - 9780791849941 ; 3
-
Konferensbidrag (refereegranskat)abstract
- FCP (Fatigue Crack Propagation) based fatigue assessments of a welded joint in a 2800 TEU container ship which sails on North Atlantic routes are performed. The Great-circle course with small variation of relative heading angle and a southerly course with large variation of relative heading angle are considered. Short sea sequences are generated by using ‘storm model’ developed by Osaka University and ‘spatio-temporal model’ developed by Chalmers University. Sea keeping analyses are performed for both cases wherein the variation in wave direction’s occurrence probability is considered (‘real headings model’) or not (‘all-headings model’). FCP analyses are performed considering plasticity-induced crack closure by using FASTRAN-II. Fatigue crack propagation lives and characteristics of crack propagation retardation due to excessive loads are compared. Based these results, the influence of the difference in load sequence model on FCP-based fatigue assessment result is discussed.
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| 22. |
- Guo, Xiaodong, et al.
(författare)
-
Energy management system for hybrid ship: Status and perspectives
- 2024
-
Ingår i: Ocean Engineering. - 0029-8018. ; 310
-
Forskningsöversikt (refereegranskat)abstract
- With the growing concerns over energy scarcity and environmental degradation, multi-energy hybrid propulsion systems are emerging as a vital innovation for the future of maritime transport. This paper collects related literature on intelligent hybrid power marine energy management systems from the Web of Science database and provides a comprehensive review of the design phase to operation. Based on this, future research directions are proposed for both the academic community and practitioners. Hybrid smart ships employ optimization models with objectives such as lowering operating costs, meeting emission standards, or improving performance, and the design of efficient algorithms is a hot research topic in the field of green shipping. Future research directions include adopting high-tech technologies, such as big data and artificial intelligence, to design hybrid control strategies, developing integrated control of multiple systems and multi-objective optimization models, and acquiring and predicting real-time navigation environments.
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| 23. |
- Han, Jiru, et al.
(författare)
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An Artificial Potential Field Model for the Risk Assessment of Icebreaker Escort Operations
- 2022
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; , s. 1295-1302
-
Konferensbidrag (refereegranskat)abstract
- The icebreaker escort operations are typical navigation models in Arctic shipping. The current studies mainly focus on analyzing and quantifying the ship navigation risk for icebreaker escort operations concerning ship-to-ship collision avoidance. However, scenarios of ship stuck in sea ice are also interested and lacking study. To this end, we proposed a risk assessment model based on the artificial potential field theory, including two parts: a) the icebreaker risk field and b) the sea ice risk field. The icebreaker risk field describes the ship-to-ship collision risk, while the sea ice risk field describes the risk of ships stuck in sea ice. The proposed model can determine fleet members’ minimum and maximum safety distances to enhance the safety of Arctic fleet shipping.
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| 24. |
- He, Yapeng, et al.
(författare)
-
Two-phase energy efficiency optimisation for ships using parallel hybrid electric propulsion system
- 2021
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- Developing a green, intelligent, and efficient power system is an important way for the shipping industry to respond to increasingly stringent emission regulations, and to achieve improvements in energy conservation and efficiency. In this study, a two-phase energy efficiency optimisation method is proposed for reducing energy consumption. The method comprises a combination of speed optimisation and energy management. On the demand side, the minimum accumulated power consumption required by the propeller is set as the objective function for the speed optimisation model, whereas on the supply side, the lowest cost of energy consumed by the hybrid power system is set as the objective function for the energy management model. An inland parallel hybrid electric powered bulk carrier is selected for a case study of the two-phase energy efficiency optimisation method. The optimisation results are compared with the energy consumption data of a bulk carrier under normal working conditions. The results show that the proposed method can reduce the energy consumption by 2.60% and 9.86% in the westbound and eastbound voyages, respectively. Accordingly, this study can provide methodological support for inland hybrid-powered ships aiming to achieve intelligent energy efficiency management.
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| 25. |
- Hildeman, Anders, 1984, et al.
(författare)
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An evaluation of conditional spatial predictions of significant wave height based on the nonstationary spde model
- 2020
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; 2020-October, s. 2176-2183
-
Konferensbidrag (refereegranskat)abstract
- The sea state plays an important role in offshore-and marine operations. It affects both direct costs as well as risks for human and/or material loss. A better understanding of the present-, near-future-, and far-future sea states will increase efficiency and safety in shipping since it allow a ship to reroute to a safer and/or more cost effective route. In the offshore industry it allows for minimizing downtime and aids in planning the construction of new offshore sites. Due to the complex nature of the sea state, its spatial distribution over a large region of ocean should be modeled using a probabilistic model. In this way, uncertainties due to lack of information and/or computing power can be quantified and decisions can be taken based on both what is known and what is not known. We analyze such a spatial probabilistic model in order to assess its ability to predict the significant wave height in the whole north Atlantic based only on measurements on a small line path, i.e., conditional prediction. This work is relevant for several applications, for instance data assimilation, oceanographic forecasting, and routing of ships.
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| 26. |
- Hjorth Simonsen, Martin, 1988, et al.
(författare)
-
State-of-the-art within ship weather routing
- 2015
-
Ingår i: Proceedings of The ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2015). - 9780791856499 ; 3, s. 1-11
-
Konferensbidrag (refereegranskat)abstract
- Increased fuel prices and public awareness of environment impacts from shipping have attracted large efforts in maritime sector to increase its energy efficiency as a factor of competitiveness. Weather routing has become a recognized measure, which can partly help to achieve the targets as well as enhancing safety. A routing system requires a reliable optimization algorithm to consider a ship’s operational costs, expected time of arrival, and cargo safety etc. simultaneously. Hence, the service provided by a weather routing system is highly dependent on a properly selected optimization algorithm and associated input parameters. In this paper the concept of weather routing is broken down into many elements for further analysis. Focus is given to algorithms, constraints and weather forecasts used in the optimized routing plan. Two different aspects of state-of-the-art have been considered. The first is a study of software already in use and the second is a study of methods investigated in the research community. Furthermore, this paper also provides examples of development trends, for example the fatigue based routing, and the risk based routing, as well as its integration with onboard monitoring systems for more reliable weather and ship specific response information.
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| 27. |
- Huang, Hui, et al.
(författare)
-
Experimental and numerical investigation of a gouging heat source model and gouging/welding residual stress and deformation
- 2024
-
Ingår i: Journal of Manufacturing Processes. - 1526-6125. ; 110, s. 101-113
-
Tidskriftsartikel (refereegranskat)abstract
- Gouging is generally used for groove preparation of multi-pass welding and repair welding. Arc gouging is one of the most efficient gouging methods which utilizes an arc heat source and a trailing air blower. To date, the heat effects from the arc gouging are not clear especially when it is coupled with subsequent welding. In this study, a new heat source model considering the blown molten metal as well as the increased heat transfer by the blowing air was proposed. A 3D finite element model for gouging and welding was employed to analyze the thermal behavior, welding distortion and residual stresses. The transient temperature predicted by the proposed heat source model has good agreement with thermocouple measurements, both featuring multiple peaks in the thermal profile. The predicted distortion and residual stress due to gouging show similar trends as those in experiment. The proposed analysis approach can provide necessary insights, with high accuracy, in the evaluation of welding distortion and residual stresses in practical manufacturing.
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| 28. |
- Lang, Xiao, 1992, et al.
(författare)
-
A Machine Learning Ship’s Speed Over Ground Prediction Model and Sailing Time Control Strategy
- 2022
-
Ingår i: International Journal of Offshore and Polar Engineering. - : International Society of Offshore and Polar Engineers. - 1053-5381. ; 32:4, s. 386-393
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a machine learning–based ship speed over a ground prediction model, driven by the eXtreme Gradient Boosting (XGBoost) algorithm. The data set is acquired from a world-sailing chemical tanker with five years of full-scale measurements. The model is trained using encountered metocean environments and ship operation profiles in two scenarios: through propeller revolutions per minute (RPM) or propulsion power. This model is further combined with the particle swarm optimization algorithm to integrate a sailing time control method. It optimizes constant RPM or power operation strategy to meet the requirements of a fixed estimated time of arrival.
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| 29. |
- Lang, Xiao, 1992, et al.
(författare)
-
A Machine Learning Ship's Speed Prediction Model and Sailing Time Control Strategy
- 2022
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; , s. 3598-3605
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes a machine learning based ship speed over ground prediction model, driven by the eXtreme Gradient Boosting (XGBoost) algorithm. The dataset is acquired from a world-sailing chemical tanker with five years of full-scale measurements. The model is trained using encountered metocean environments and ship operation profiles in two scenarios, i.e., through RPM or propulsion power. This model is further combined with the particle swarm optimization (PSO) algorithm to integrate a sailing time control method. It optimizes constant RPM or power operation strategy to meet the requirements of fixed ETA.
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| 30. |
- Lang, Xiao, 1992, et al.
(författare)
-
A Practical Speed Loss Prediction Model at Arbitrary Wave Heading for Ship Voyage Optimization
- 2021
-
Ingår i: Journal of Marine Science and Application. - : Springer Science and Business Media LLC. - 1993-5048 .- 1671-9433. ; 20:3, s. 410-425
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading. In the model, the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed. A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation. The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles. The full-scale measurements from three different types of ships, i.e., a PCTC, a container ship, and a chemical tanker, are used to validate the proposed model for speed loss prediction in irregular waves. The effect of the improved model for speed loss prediction on a ship’s voyage optimization is also investigated. The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves.
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| 31. |
- Lang, Xiao, 1992, et al.
(författare)
-
A semi-empirical model for ship speed loss prediction at head sea and its validation by full-scale measurements
- 2020
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a semi-empirical model to estimate a ship’s speed loss at head sea. In the model, the formulas to estimate a ship’s added resistance due to waves have been further developed to better consider the ship hull forms, in addition to other main particulars. Based on the model experimental tests of 11 ships in regular head waves, the new formulas have more flexible forms and can better fit the test results than other similar models. In addition, this model proposes a significant wave height based correction factor multiplied to the conventional integration to compute wave resistance in irregular waves. This factor is supposed to consider the impact of coupled ship motions in high waves on a ship’s added resistance due to waves. The model is validated by the full-scale measurement from two vessels, a PCTC and a chemical tanker. The encountered weather conditions along the sailing routes are extracted from the reanalysis metocean data. The results indicate that the proposed model can provide quite accurate predictions of ship speed loss in head sea operations.
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| 32. |
- Lang, Xiao, 1992, et al.
(författare)
-
A Simplified Ship Wave Induced Added Resistance Calculation Method and Full-scale Measurements Validation in Head Sea
- 2020
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; 2020-October, s. 3394-3402
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we introduce a semi-empirical head wave added resistance calculation formula. The formula considers the ship hull forms as well as the main particulars and was verified by the available experimental data in the regular wave. One PCTC full-scale measurements were carried out to perform the added resistance validation in the irregular sea, with a newly proposed wave height correction factor. The encountered weather conditions were extracted from the reanalysis metocean data. The result indicated that the proposed formula has achieved reasonable accuracy with fast calculation, and was discussed with regards to uncertainties and prediction capacity.
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| 33. |
- Lang, Xiao, 1992, et al.
(författare)
-
An Indirect Measurement Methodology to Identify Fatigue Damage in The Structure of a 2800TEU Container Ship
- 2024
-
Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. ; Volume 2: Structures, Safety, and Reliability
-
Konferensbidrag (refereegranskat)abstract
- Ships endure fatigue damage from continuous wave-induced stress. The spectral method, despite being a standard assessment tool, is fraught with uncertainties. However, a large segment of today’s maritime vessels abstains from embedding continuous, life-cycle-spanning sensor systems to monitor fatigue damage accumulation. This lacuna precipitates pronounced ambiguities in maintenance prediction, highlighting the urgent need for a rigorously systematic approach to address this knowledge void. To address these issues, this paper introduces a machine learning-based indirect measurement method for evaluating fatigue damage in a 2800TEU container vessel. Utilizing three years of cross-Atlantic voyage data, the study aims to predict fatigue damage more accurately. Our method, which leverages available navigational and environmental data, circumvents the need for intricate sensors. We benchmark our model’s predictions against full-scale measurements and conventional approaches, scrutinizing the accuracy and reliability of each. This indirect strategy not only promises to enhance maritime safety through a more lucid understanding of fatigue accumulation but also supports maintenance planning by estimating long-term fatigue impact. This research posits a simpler yet potentially more efficacious alternative for the surveillance and management of fatigue in maritime vessels.
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| 34. |
- Lang, Xiao, 1992, et al.
(författare)
-
Benchmark Study of Supervised Machine Learning Methods for a Ship’s Speed-Power Prediction at Sea
- 2021
-
Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. ; 6
-
Konferensbidrag (refereegranskat)abstract
- The development and evaluation of energy efficiency measures to reduce air emissions from shipping strongly depends on reliable description of a ship’s performance when sailing at sea. Normally, model tests and semi-empirical formulas are used to model a ship's performance but they are either expensive or lack accuracy. Nowadays, a lot of ship performance-related parameters have been recorded during a ship's sailing, and different data driven machine learning methods have been applied for the ship speed-power modelling. This paper compares different supervised machine learning algorithms, i.e., eXtreme Gradient Boosting (XGBoost), neural network, support vector machine, and some statistical regression methods, for the ship speed-power modelling. A worldwide sailing chemical tanker with full-scale measurements is employed as the case study vessel. A general data pre-processing method for the machine learning is presented. The machine learning models are trained using measurement data including ship operation profiles and encountered metocean conditions. Through the benchmark study, the pros and cons of different machine learning methods for the ship’s speed-power performance modelling are identified. The accuracy of various algorithms based models for ship performance during individual voyages is also investigated.
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| 35. |
- Lang, Xiao, 1992, et al.
(författare)
-
Comparison between Full-scale Measurements and Theoretical Fuel Consumption Model in a Real Arctic Ship Navigation
- 2019
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. - 9781880653852 ; 1, s. 886-892
-
Konferensbidrag (refereegranskat)abstract
- Due to the global warming and the continuous decline of Arctic sea ice, maritime transport in the Arctic region has been increased dramatically. While operating in the Arctic area, ships face regular environment loads and ice loads synchronously, the consideration of ice resistance is essential for the fuel consumption estimation in the ice-covered water voyage. In this paper, a theoretical fuel consumption model is proposed based on empirical method for ship sailing through the Arctic route. The results are compared with the full-scale measurements in a real Arctic ship navigation, and discussed with regards to uncertainties and the prediction capacity of the fuel consumption model. The encountered sea states and ice thickness are constructed by hindcast reanalysis data and climate model projections.
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| 36. |
- Lang, Xiao, 1992, et al.
(författare)
-
Comparison of supervised machine learning methods to predict ship propulsion power at sea
- 2022
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 245
-
Tidskriftsartikel (refereegranskat)abstract
- As the shipping moves towards digitization, a large amount of ship energy performance-related information collected during a ship's sailing provides opportunities to derive data-driven performance models using different machine learning algorithms. This paper compares several typical supervised machine learning algorithms, i.e., eXtreme Gradient Boosting (XGBoost), artificial neural network, support vector machine, and statistical regression methods, for the ship speed–power modeling. First, a general data pre-processing framework is presented. The different machine learning based models are trained by both ship operational parameters and encountered metocean conditions. Based on the full-scale measurement data collected at two types of worldwide sailing ships, the pros and cons of different machine learning algorithms for the ship's speed–power performance modeling are compared. Finally, the best performed XGboost model is chosen to analyze the sensitivity due to the amount of available ship data, assumed time period for each stationary waypoint (data sample) used for the model training, and their impact on online performance prediction.
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| 37. |
- Lang, Xiao, 1992, et al.
(författare)
-
Data-driven ship fatigue assessment based on pitch and heave motions
- 2023
-
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 ; , s. 95-103
-
Konferensbidrag (refereegranskat)abstract
- Ocean-crossing ship structures continuously suffer from wave-induced loads when sailing at sea. The encountered wave loads cause significant variations in ship structural stresses, leading to accumulated fatigue damage. It is common today to use the spectral method for direct fatigue calculation when evaluating ship fatigue, where large inherent uncertainties still exist. This paper investigates the machine learning technique to establish model for a 2800TEU container vessel fatigue assessment. The measurement data of three years cross-Atlantic sailing demonstrates and validates the machine learning model. In this investigation, the motions of the ship are used as inputs to build machine learning model. The fatigue damage amounts predicted using machine learning model were compared with those obtained from full-scale measurements and direct fatigue calculation. The pros and cons of the methods are compared in terms of capability, robustness, and accuracy of the prediction.
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| 38. |
- Lang, Xiao, 1992, et al.
(författare)
-
Fatigue assessment comparison between a ship motion-based data-driven model and a direct fatigue calculation method
- 2023
-
Ingår i: Journal of Marine Science and Engineering. - 2077-1312. ; 11:12, s. 1-16
-
Tidskriftsartikel (refereegranskat)abstract
- Ocean-crossing ship structures continuously suffer from wave-induced loads when sailing at sea. The encountered wave loads cause significant variations in ship structural stresses, leading to accumulated fatigue damage. Where large inherent uncertainties still exist, it is now common to use spectral methods for direct fatigue calculation when evaluating ship fatigue. This paper investigates the use of a machine learning technique to establish a model for 2800TEU container vessel fatigue assessment. Measurement data from 3 years of cross-Atlantic sailing demonstrated and validated the machine learning model. In this investigation, the ship’s motions were used as inputs to build a machine learning model. The fatigue damage amounts predicted using a machine learning model were compared with those obtained from full-scale measurements and direct fatigue calculation. The pros and cons of the methods are compared in terms of their capability, robustness, and prediction accuracy.
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| 39. |
- Lang, Xiao, 1992, et al.
(författare)
-
Impact of ship operations aided by voyage optimization on a ship’s fatigue assessment
- 2021
-
Ingår i: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 26:3, s. 750-771
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, different operation factors affecting a ship’s wave statistics are studied, such as the slow steaming and voyage optimizations. Especially, the impact of various voyage optimization methods on the long-term wave statistics and corresponding fatigue damage during ship operations is investigated by comparing the encountered waves with the design wave scatter diagram. Three years of full-scale measurements from a container ship sailing in the North Atlantic are employed to study the impact, in addition to noon reports from two fleets of container ships and VLCCs. Furthermore, the benefits of using voyage optimizations for minimum fatigue damage accumulation during operation are discussed. The large difference of wave statistics is found when the ship follows routes generated by various optimization methods and the design diagram. For some westbound voyages, the voyage optimization methods can significantly decrease the ship’s fatigue damage accumulations, leading to longer fatigue life.
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| 40. |
- Lang, Xiao, 1992, et al.
(författare)
-
Physics-informed machine learning models for ship speed prediction
- 2024
-
Ingår i: Expert Systems with Applications. - 0957-4174. ; 238
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a novel physics-informed machine learning method to build grey-box model (GBM) predicting ship speed for ocean crossing ships. In this method, the expected ship speed in calm water is first modeled by the physics-informed neural networks (PINNs) based on speed-power model tests. Then the eXtreme Gradient Boosting (XGBoost) machine learning algorithm is integrated to estimate ship speed reduction under actual weather conditions. The proposed GBM has been compared against the traditional black-box model (BBM) using performance monitoring data from two ships. The results show that when the amount of data is sufficient for modeling, the GBM can increase the accuracy of speed prediction by about 30%. When data volume is limited, the GBM can also significantly improve the prediction results. Finally, the GBM is validated by checking its implementation for the ETA predictions of cross-Pacific or North Atlantic voyages. The highest cumulative error of sailing time estimated by the GBM is 5 h among all the study cases.
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| 41. |
- Larsson, Erik, 1988, et al.
(författare)
-
DIRECT Optimization Algorithm for Ship Routing Plan
- 2015
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. 25th International Offshore and Polar Engineering Conference, ISOPE-2015, Hawaii, 21-26 June 2015.. - 1098-6189.
-
Konferensbidrag (refereegranskat)abstract
- Weather routing represents one increasingly recognized method for reducing fuel consumption, hereby lowering emissions and costs. This paper provides a short outline of the general concept of weather routing of ships, while focus is on the implementation of the DIRECT (DIviding RECTangles) algorithm in the construction of a novel weather routing tool made in cooperation with Maersk Maritime Technology. The developed routing tool is demonstrated on several conceptual cases to determine capabilities of route profiles avoiding obstacles such as land, avoiding adverse storms by varying voyage speed and utilizing weather to schedule a route with minimized fuel consumption. Strengths and weaknesses of the utilization of the DIRECT algorithm are discussed.
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| 42. |
- Larsson, Erik, 1988, et al.
(författare)
-
DIRECT optimization algorithm in weather routing of ships
- 2015
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. - 9781880653890 ; 2015-January, s. 1207-
-
Konferensbidrag (refereegranskat)abstract
- Weather routing represents one increasingly recognized method for reducing fuel consumption, hereby lowering emissions and costs. This paper provides a short outline of weather routing of ships, while focus is on the implementation of the DIRECT (Dividing RECTangles) algorithm in the construction of a novel weather routing tool made under supervision from Maersk Maritime Technology. It is evaluated on several conceptual cases to determine capabilities of route profiles avoiding obstacles such as adverse storms by varying voyage speed and utilizing weather to schedule a route with rmnimized fuel consumption. This paper discusses the application of the developed routing tool for shortest route, land avoidance, storm avoidance and combinations. Strengths and weaknesses of the utilization of the DIRECT algorithm are discussed.
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| 43. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
A comparative study of fatigue assessment of a container ship structure using various direct calculation approaches
- 2012
-
Ingår i: Proceedings of The International Conference on Maritime Technology (ICMT 2012). ; , s. 405-409
-
Konferensbidrag (refereegranskat)abstract
- Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction due to the different degrees of complexity as well as the large number of uncertainties in the computation of the ship’s response. In this investigation, a comparative study is carried out on a Panamax container ship in oblique waves using different typical direct calculation methods. The results of fatigue life prediction using these methods are compared with results obtained from full-scale measurements. It is found that the nonlinear time-domain method shows the best agreement with the full-scale measurements, and therefore, it is recommended to be used in fatigue predictions.
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| 44. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
A comparative study of fatigue assessments of container ship structures using various direct calculation approaches
- 2014
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 82:1, s. 65-74
-
Tidskriftsartikel (refereegranskat)abstract
- It is common practice today to carry out fatigue assessments of ship structures using direct calculation procedures to compute fatigue loads. Many numerical codes are available for use in such fatigue load analyses. In addition to the various degrees of computation complexity associated with fatigue estimation methods, such methods also have large inherent uncertainties. In this investigation, a comparative study was carried out for two container ships using various typical direct fatigue calculation methods. The fatigue damage amounts calculated using these methods were compared with those obtained from full-scale measurements. Most of the direct calculation approaches investigated yielded similar fatigue damage estimates. The approach that employs nonlinear time-domain hydrodynamic analysis and the finite element method yields reasonable and conservative fatigue damage results and is therefore recommended. In addition, the results of this study confirm that various measures of wave environments and of the variation in wave models are important sources of uncertainty in fatigue life prediction.
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| 45. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
A comparison of direct calculation approaches applied on the fatigue strength assessment of a Panamax container ship
- 2012
-
Ingår i: Proceedings of The ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2012). ; 2, s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. A direct calculation analysis of a ship’s fatigue strength involves hydrodynamic analysis, stress response evaluation followed by fatigue damage calculation. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction because of the different degrees of complexity in the computation of the ship’s response. For example, hydrodynamic loads can be calculated using the strip theory or the panel method. The stress response to these loads can be computed using a beam theory or more advanced analyses, such as global and/or local finite element analyses. In a direct fatigue analysis for ship design, spectral methods have been dominating but there is a growing interest in time-domain fatigue damage calculation procedures. The objective of the current investigation is to compare four commonly used direct calculation methods against measurement data. The comparison is carried out by making a case study on a Panamax container ship on which full-scale measurements have been performed. The computational efforts involved in the application of the current direct calculation methods are compared and their applicability in ship fatigue design is discussed.
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| 46. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
An efficient direct calculation approach for fatigue assessment of container ships concerning bending and warping stresses
- 2014
-
Ingår i: Proceedings of The 2014 ASME 33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2014). - 9780791845424 ; 4A, s. 1-9
-
Konferensbidrag (refereegranskat)abstract
- Container ships are particularly susceptible to torsional loads. The distribution of torsion-induced warping stress in a container ship hull is more complicated and difficult to be expressed by beam theory formulas. In practice, finite element (FE) analysis is typically used to calculate the stress response to wave-loading conditions. However, it is time consuming to compute hull girder stresses for all relevant sea conditions through FE analyses. In this paper, an efficient and robust approach is proposed by combining beam theory and FE analyses in the determination of hull girder stresses. The parameters required by beam theory can be regressed through matching stress records from a FE analysis with the corresponding sectional and pressure loads from the hydrodynamic simulation. Stress records obtained using the proposed method are utilized in fatigue assessment of a case study container vessel. The results show that the accuracy of the regression approach is satisfactory compared with the full FE analyses.
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| 47. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
Fatigue damage assessment of container ships concerning wave-induced torsion
- 2010
-
Ingår i: Proceedings of the ASME 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) in Shanghai, China, June 6-11, 2010. - 9780791849101
-
Konferensbidrag (refereegranskat)abstract
- The traditional method to assess fatigue damage of ship structures assumes moderate wave amplitudes and linear responses. This method can be questioned when applied on container ships that are characterized by large deck openings, because the low torsion rigidity of this type of ship makes it sensitive to oblique waves. In this paper, the 3D hydrodynamic code WASIM is used to simulate a 4400 TEU container ship operating in the North Atlantic Ocean. Nonlinear wave loads are utilized for direct calculation of the stress histories under severe sea states. The warping stress from wave-induced torsion is separated from the stress components from vertical and horizontal bending. The contribution to fatigue damage accumulation from warping stresses is evaluated. For comparison, the results from the numerical simulations and fatigue calculations are verified with full-scale measurements made on a similar type of container vessel.
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| 48. |
- Liang, Zheng, et al.
(författare)
-
Use of Bayesian networks for emergency assistance assessment of ship capsizing
- 2017
-
Ingår i: The 4th International Conference on Transportation Information and Safety, Aug. 8-10 in Banff, Alberta, Canada. - 9781538604373 ; , s. 92-98
-
Konferensbidrag (refereegranskat)abstract
- Accident caused by a ship’s capsize is one of the hottest spots in the public security due to their sudden and severe consequences, such as Eastern Star and Sewol accidents happened in the past few years. To improve the ability of emergency handling, e.g. Search And Rescue (SAR) operations in inland waters to waterborne transport accidents, a SAR evaluation model for inland ships is proposed based on the Bayesian network technique and an expert survey. The model starts with the statistical analysis of historical ship capsize data from 1998 to 2010. The statistics and expert knowledge are synthesized in the Bayesian network model to obtain the probability distribution of the consequences. Then, several indicators that influence the consequences are identified based on case study and sensitivity analysis, e.g. navigation environment, self-rescue ability and emergency disposal etc. Finally, the proposed Bayesian network model is used as a tool for emergency assistance assessment aiming to mitigate the consequences due to ship capsizing.
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| 49. |
- Liu, Jia Rong, et al.
(författare)
-
Effects of second-order wave force on fatigue damage assessment of a tlp-type floating wind turbine
- 2020
-
Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; 2020-October, s. 415-422
-
Konferensbidrag (refereegranskat)abstract
- Resonant and transient responses of a tension leg platform (TLP)-type floating offshore wind turbine can be excited by high-frequency wave forces. This paper investigates the damaging effect of second-order wave forces on structural fatigue in the WindStar TLP system. Dynamic responses in the time domain are analyzed using the program FAST. To explore the mechanisms of different combinations of wind and wave loads inducing damage, five scenarios are considered: wind only, first-order wave only, second-order wave only, joint wind and first-order wave, and joint wind and second-order wave. The results show the dominant effect of second-order waves in tower structural fatigue damage. Additionally, wind and wave coupling becomes stronger under second-order wave loads.
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| 50. |
- Lu, Ruihua, 1988, et al.
(författare)
-
Wind-assisted propulsion for shipping: status and perspectives
- 2017
-
Ingår i: Proceedings of The 2nd International Conference on Ships and Offshore Structures (ICSOS 2017). ; , s. 561-571-571
-
Konferensbidrag (refereegranskat)abstract
- The major objective of this paper is to summarize the status of wind-assisted propulsion for shipping, especially focus on the relevant literature published during the last ten years. According to its research directions within wind-assisted technologies, the status summary is divided into four sections. Firstly, the drivers of utilizing wind propulsion technologies and the operating principles of four popular wind propulsion technologies are introduced. Next the deployment status and technical considerations of current wind-assisted propulsion for shipping are illustrated. Then the barriers to uptake and development of wind propulsion technologies are discussed. Finally, some perspectives regarding the future developments and use of wind-assisted propulsion technologies for shipping activities are presented. The possible actions that are helpful to overcome the barriers in developing and utilizing wind-assisted propulsion technologies are proposed and analyzed.
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