| 1. |
- Figuero, Andres, et al.
(author)
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Dynamical study of a moored vessel using computer vision
- 2018
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In: Journal of Marine Science and Technology. - : NATL TAIWAN OCEAN UNIV. - 0948-4280 .- 1437-8213. ; 26:2, s. 240-250
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Journal article (peer-reviewed)abstract
- Wind and wave effects have a major impact on the design of mooring and anchoring systems, whose purpose is to prevent the movement of the cargo and the moored ship while optimizing the operations which have to take place in port. The dynamic behavior of a ship moored in waves has been mathematically described and interactions between ships and environmental loads have been commonly tested for different docks and mooring systems in scale models. However, the behavior of real ships in true mooring conditions has not been properly addressed in scientific literature. This paper proposes a novel computer vision technique to monitor moored ships. This approach uses the correlation of visual features in the images of the ship to estimate its movements along time. The proposed technique has been validated in laboratory conditions and applied in a real scenario to study the behavior of the ship Urania Mella in the Outer Port of A Coruna (Spain), in Punta Langosteira, obtaining very promising results.
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| 2. |
- Jia, Junbo, 1979
(author)
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Investigations of vehicle securing without lashings for Ro-Ro ships
- 2007
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In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 12:1, s. 43-57
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Journal article (peer-reviewed)abstract
- o reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing based on this "lashing-free" concept, computational code was developed to calculate the vehicle-deck interactions for various ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will still need to be lashed. The limitations of the current investigations are also presented.
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| 3. |
- Lang, Xiao, 1992, et al.
(author)
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Impact of ship operations aided by voyage optimization on a ship’s fatigue assessment
- 2021
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In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 26:3, s. 750-771
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Journal article (peer-reviewed)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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| 4. |
- Leer-Andersen, M, et al.
(author)
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An experimental/numerical approach for evaluating skin friction on full-scale ships with surface roughness
- 2003
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In: Journal of Marine Science and Technology. - : Springer Japan. - 0948-4280 .- 1437-8213. ; 8:1, s. 26-36
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Journal article (peer-reviewed)abstract
- For an accurate evaluation of the increase in skin friction due to various surface topographies on ships, i.e. plate roughness, coatings, or bio fouling, both experimental measurements and a numerical evaluation of those measurements are necessary. The measurements are necessary as no other practical method exists to evaluate the skin friction coefficient on most surface topographies, and numerical evaluation is required to compute the roughness effects of varying ship types and speeds. Therefore, a method for measuring the skin friction coefficient for bio-fouled and structured surfaces at full-scale friction velocity is presented, and a validation of the design and measuring procedures is given. For the ship frictional resistance calculations, the Computational Fluid Dynamics (CFD) code SHIPFLOW has been modified to take the added friction into account.
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| 5. |
- Lu, Nai Xian, 1983, et al.
(author)
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Large Eddy Simulation of Cavitation Development on Highly Skewed Propellers
- 2014
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In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 19:12, s. 197-214
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Journal article (peer-reviewed)abstract
- This paper deals with numerical simulations of the cavitating flow around two highly skewed propellers operating in open water and mounted on an inclined shaft. The aim of the study is to check the ability of our numerical method in distinguishing the variation in flow features resulting from different blade designs. Moreover, a secondary aim is also to improve the knowledge about the physics that control the growth and collapse of cavitation, and hence also the generation of cavitation noise and erosion on this type of propellers. The investigation is based on incompressible large eddy simulation (LES) in combination with a volume-of-fluid implementation to represent the two phases of liquid and vapour, and a transport equation-based method for the mass transfer between the phases. High-speed video recordings from experiments were made available for comparison. The simulations demonstrate that the current method makes it possible to analyse the main difference in flow features caused by modest design alternation. Furthermore, with suitable grid resolution, LES is demonstrated to be capable of capturing the mechanisms that are important in the cavitation development, and that numerical simulation is a reliable supplement to experiments in advanced propeller design.
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| 6. |
- Ning, Dezhi, et al.
(author)
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Hydrodynamic performance of an oscillating wave surge converter in regular and irregular waves : an experimental study
- 2017
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In: Journal of Marine Science and Technology. - 0948-4280 .- 1437-8213. ; 25:5, s. 520-530
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Journal article (peer-reviewed)abstract
- A series of physical experiments are carried out to investigate the hydrodynamic performance of a bottom-hinged flap-type oscillating wave surge converter (OWSC). The power take-off (PTO) system in the OWSC is achieved with the magnetic powder brake. Both regular and irregular wave conditions are considered. It is observed that the capture width ratio (CWR) of the proposed OWSC is strongly affected by the PTO damping torque, incident wave amplitude, inertia of the structure and wave spectrum etc.
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| 7. |
- Skoglund, Lukas, et al.
(author)
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A comparative study of deterministic and ensemble weather forecasts for weather routing
- 2015
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In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 20:3, s. 429-441
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Journal article (peer-reviewed)abstract
- This paper presents and discusses the results of a comparison between using deterministic and ensemble weather forecasts for weather routing. The study is based on comparisons between predicted and realised performance of routes suggested by a route optimization method and focuses on two important performance factors, namely, fuel consumption and late arrival. The study is purely qualitative since the simulations do not include re-routing of the vessel as new forecasts become available. To perform the study a multi-objective dynamic programming method is tailored to the problem and implemented to perform the route optimization and a ship performance model is used to calculate the additional fuel consumption due to wind and waves acting on the ship. The results show that route optimization using ensemble weather forecasts has the potential to reduce the risk of late arrival for voyages during periods of harsh weather.
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| 8. |
- Strasser, G., et al.
(author)
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A verification of the ITTC/ISO speed/power trials analysis
- 2015
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In: Journal of Marine Science and Technology. - : Springer Japan. - 0948-4280 .- 1437-8213. ; 20:1, s. 2-13
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Journal article (peer-reviewed)abstract
- Speed and power (S/P) trials are most important to guarantee the ship’s propulsive performance. However, it was pointed out that the existing procedures often give a good guideline, but are not specific and can introduce inconsistent results. Recently, ITTC and ISO have improved their S/P trials procedures and harmonized the two procedures. During the harmonization process, we have verified the ‘Mean of Means’ (MoM) method and the ‘Iterative’ method which are used as the current correction methods and the ‘Direct Power Method’ and the ‘Extended Power Method’ which are applied for the evaluation of the acquired data. The results of verification are presented in this paper. The results show that using the ‘MoM’ method for each power setting, two double runs should be made to keep the accuracy of S/P trials, and the ‘Iterative’ method leads to less errors in average of the tested cases when 1 + 2 + 2 double runs are used in the ‘MoM’ method, although the methods are equally adequate if the time periods between the runs are short enough. In specific cases, e.g. in case of large speed range and/or humps and hollows within the speed–power curve, the ‘MoM’ method has advantages over the ‘Iterative’ method. In case of current time history deviating from the assumed parabolic/sinusoidal trend and the change of the current within the time span of two double runs is very high, neither of the methods are applicable. Summarizing the results, the ‘Iterative’ method is fully compatible with the simple ‘Direct Power Method’
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| 9. |
- Söder, Carl-Johan, 1982-, et al.
(author)
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Ikeda Revisited
- 2019
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In: Journal of Marine Science and Technology. - : Springer. - 0948-4280 .- 1437-8213. ; 24:1, s. 306-316
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Research review (peer-reviewed)abstract
- In this paper Ikeda’s method for roll damping prediction is revisited and the applicability of the method to modern volume carriers is considered. For volume carriers the hull lift and bilge keel components are the dominating components and the estimation of these components in the original method are benchmarked and scrutinized. It is concluded that the speed dependence of the bilge keels damping is underestimated by the original method. This is partially explained by that Ikeda seems to have underestimated the lift force of the bilge keels in his analytical expressions. Correcting for this and taking account of the lift force generated pressure on the hull surface gives overall better agreement with model tests. It is also concluded that the hull lift damping component is significantly overestimated with the original method. Non-viscid CFD is used to propose a new generic expression for estimating the lift coefficients for volume carriers which greatly improve the accuracy in comparison to model test results. With these improvements Ikeda’s method is revitalized and the applicability is extended to unconventional volume carriers.
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| 10. |
- Söder, Carl-Johan, et al.
(author)
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Parametric roll mitigation using rudder control
- 2013
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In: Journal of Marine Science and Technology. - : Springer Science and Business Media LLC. - 0948-4280 .- 1437-8213. ; 18:3, s. 395-403
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Journal article (peer-reviewed)abstract
- Severe roll angles can be developed by parametric excitation in relatively moderate weather without any apparent pre-warning for the crew onboard. In this study the prospect of using rudder control to mitigate parametric roll was investigated using multi-degree of freedom simulations. A typical modern Pure Car and Truck Carrier was considered and modelled by coupling a roll model with a planar motion manoeuvring model. The combined model was calibrated using in-service, full-scale trials and model tests. Irregular variations of the metacentric height were applied to simulate recorded, full-scale events of parametric roll that have occurred with the considered design. These simulations with rudder roll control showed promising results and demonstrate that the approach could be very efficient for mitigation of parametric roll.
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