| 1. |
- Huang, Luofeng, et al.
(författare)
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An investigation on the speed dependence of ice resistance using an advanced CFD+DEM approach based on pre-sawn ice tests
- 2022
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 264
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Tidskriftsartikel (refereegranskat)abstract
- Over the past decades, the underlying mechanism of level ice resistance changing with ship speed has not been fully understood, particularly the resistance component due to ship interactions with broken ice pieces. Pre-sawn ice test can negate icebreaking component from the whole resistance of a ship in level ice, providing an effective approach to decompose ship-ice interactions and investigate the speed-dependent resistance from broken ice pieces. This work has built a computational model that can realistically simulate a ship advancing in a pre-sawn ice channel. The model applies Computational Fluid Dynamics (CFD) to solve the flow around an advancing ship, which is coupled with an enhanced Discrete Element Method (DEM) to model pre-sawn ice pieces. Model-scale experiments have also been conducted at the Aalto Ice Tank to validate the simulations, which shows the computational model can provide a reasonable estimation of the pre-sawn ice's resistance and movement around the ship. Upon validation, the dependence of ice resistance on ship speed was analysed. The simulations enable underwater monitoring of the ice motions, indicating that the speed dependence results from the mass of ice submerged underneath the ship and the displacement of broken ice induced by the ship. The identified relationships are more complex than the widely-used assumption that ice resistance linearly changes with ship speed in all cases, which provides a deeper understanding of ice resistance. As such, the findings from this study can potentially facilitate improvements in relevant empirical equations, useful for ship design, operational strategies and maritime management in polar regions.
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| 2. |
- Huang, Luofeng, et al.
(författare)
-
CFD analyses on the water entry process of a freefall lifeboat
- 2021
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- The launch of lifeboats is commonly completed through freefall dropping from a considerable height, where the lifeboat is released from an inclined skid so that it can obtain a forward speed after being launched. The drop is followed by a water entry process that can induce high impact forces on the hull, which gives a significant risk of structural damages. Ascertaining the water entry impact is therefore a key step of lifeboat design; however, conventional methods have linear assumptions and assess the water impact following a quasi-static manner, which causes these methods to be not fully accurate and ignore some important details. To address this gap, this work developed a model based on Computational Fluid Dynamics to holistically simulate and analyse the process. An overset mesh technique was incorporated to reproduce the entire series of drop, water entry and resurfacing, in which the pressure distribution on the whole hull was obtained and recorded with a sampling frequency of 1000 Hz to ensure the peak impacts can be captured. Full-scale measurements were used to confirm the accuracy of the present computational model. Subsequently, a systematic series of simulations were performed to investigate how the water entry process is influenced by the inclined angle and height at which the lifeboat is dropped. The results show that a higher dropping angle can reduce the pressure impacts, but the dropping angle also dictates the lifeboat's motion pattern during the water entry. It was demonstrated that the best dropping angle is around 70° for the investigated case, since an either too low or too high dropping angle would cause the lifeboat to appear in an undesirable after-launch status. This indicates the great importance to assess the optimal dropping angle for every potential freefall lifeboat launch, and the present work proved an effective approach to perform the task.
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| 3. |
- Huang, Luofeng, et al.
(författare)
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COVID-19 transmission inside a small passenger vessel: Risks and mitigation
- 2022
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 255
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Tidskriftsartikel (refereegranskat)abstract
- The global shipping industry has been severely influenced by the COVID-19 pandemic; in particular, a significant amount of passenger transportation has been suspended due to the concern of COVID-19 outbreak, as such voyages confine a dense crowd in a compact space. In order to accelerate the recovery of the maritime business and minimise passengers' risk of being infected, this work has developed a computational model to study the airborne transmission of COVID-19 viruses in the superstructure of a full-scale passenger vessel. Considering the vessel advancing in open water, simulations were conducted to study the particulate flow due to an infected person coughing and speaking, with the forward door open and closed. The results suggest that keeping the forward door closed will help prevent the external wind flow spreading the virus. When the forward door is closed, virus particles' coverage is shown to be limited to a radius of half a metre, less than a seat's width. Thus, an alternate seat arrangement is suggested. Furthermore, investigations were conducted on the influence of wall-mounted Air Conditioner (AC) on the virus transmission, and it was found that controlling the AC outlet direction at less than 15° downward can effectively limit the virus spread. Meanwhile, it was demonstrated that an AC's backflow tends to gather virus particles in a nearby area, thus sitting farther from an opening AC may reduce the risk of being infected. Overall, this work is expected to inform hygienic guidelines for operators to counter COVID-19 and potentially similar viruses in the future.
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| 4. |
- Huang, Luofeng, et al.
(författare)
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Offshore COVID-19 risk assessment based on a fishing vessel
- 2023
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Ingår i: Ocean Engineering. - 0029-8018. ; 285
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Tidskriftsartikel (refereegranskat)abstract
- Offshore crews often work near each other due to limited space, signifying a complex environment for the airborne transmission of the coronavirus (COVID-19). During offshore operations, a fishing vessel can be subjected to miscellaneous airflow conditions and will respond dynamically to ocean waves. To understand the risk of COVID-19 contagion, this research establishes a new computational model to analyse the airborne transmission of COVID-19 and develops effective mitigation strategies where possible. The concentration and coverage of coronavirus are scrutinised, considering typical airflows and wave-induced vessel motions. Furthermore, the COVID-19 infection risk is quantified using a probability index. The results show that the overall infection risk of a ship in tailwind is lower than in head or beam wind. Structural motions are for the first time coupled with the virus transmission, and it was found that the vessel's oscillating movement in waves can reinforce the virus concentration in close proximity to the infected person and may help diffuse the virus outside the proximal region. The presented findings can inform the airborne contagion risks and corresponding hygienic measures for maritime and offshore operations, facilitating long-term human health in seas.i
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| 5. |
- Huang, Luofeng, 1993, et al.
(författare)
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Ship resistance when operating in floating ice floes: a derivation of empirical equations
- 2020
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. - 9780791884393 ; 7
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Konferensbidrag (refereegranskat)abstract
- With the effects of global warming, the Arctic is presenting a new environment where numerous ice floes are floating on the open sea surface. Whilst this has unprecedentedly improved Arctic shipping navigability and brought about significant opportunities, the interaction of such floes with ships has yet to be understood, thus hindering appropriate assessment of corresponding ship performance. This paper presents work on developing empirical equations to estimate the effects of such floes on ship resistance. Based on extensive data from validated computational simulations, the ice-floe resistance has been shown to correlate with ship beam, ship speed, ice concentration, ice thickness and floe diameter, and the regression powers of each the parameter on resistance are ascertained for a container ship. This leads to an empirical equation that can immediately predict ice-floe resistance in a given condition. The proposed approach has the potential to facilitate propulsion power estimates for Arctic shipping, as well as providing valuable insights into ship design for these environmental conditions.
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| 6. |
- Huang, Luofeng, 1993, et al.
(författare)
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Ship resistance when operating in floating ice floes: derivation, validation, and application of an empirical equation
- 2021
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Ingår i: Marine Structures. - : Elsevier BV. - 0951-8339. ; 79:1, s. 1-20
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Tidskriftsartikel (refereegranskat)abstract
- With the effects of global warming, the Arctic is presenting a new environment where numerous ice floes are floating on the open sea surface. Whilst this has improved Arctic shipping navigability in an unprecedented way, the interaction of such floes with ships is yet to be understood to aid the designing of ships and route planning for this region. To further explore this topic, the present work develops a procedure to derive an empirical equation that can predict the effects of such floes on ship resistance. Based on a validated computational approach, extensive data are extracted from simulations of three different ships with varying operational and environmental conditions. The ice-floe resistance is shown to strongly correlate with ship beam, ship buttock angle, ship waterline angle, ship speed, ice concentration, ice thickness and floe diameter, and the regression powers of each of the parameters on resistance are ascertained. This leads to a generic empirical equation that can swiftly predict ice-floe resistance for a given ship in a given condition. Subsequently, demonstrations are given on the incorporation of the derived equation into a set of real-time Arctic ship performance model and voyage planning tool, which can predict a ship’s fuel consumption in ice-infested seas and dynamically suggest a route with the least safety concern and fuel consumption. Moreover, the equation is validated by providing ice resistance prediction for experimental and full-scale conditions from multiple sources, showing high accuracy. In conclusion, the empirical equation is shown to give valid and rapid estimates for ice-floe resistance, providing valuable insights into ship designs for the region, as well as facilitating practical applications for polar navigation.
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| 7. |
- Huang, Luofeng, et al.
(författare)
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SIMULATION of A SHIP ADVANCING in PRE-SAWN ICE
- 2022
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. ; 6
-
Konferensbidrag (refereegranskat)abstract
- Pre-sawn ice test is the standard testing method to negate ice-breaking resistance from the whole resistance of a ship breaking level ice, which is of great importance for understanding ship-ice interactions and predicting various sea-ice loads on ships. This work has developed a computational model that can realistically simulate a ship advancing in a pre-sawn ice channel. The model applies Computational Fluid Dynamics to solve ship hydrodynamics, which is coupled with a novel particle-bonded Discrete Element Method to model pre-sawn ice pieces. Experiments were also conducted to validate the simulations. Upon validation, analyses were performed to investigate the ship-ice interaction. It was demonstrated that the pre-sawn ice resistance?s speed dependence has three regimes: for low ship speeds, the ice resistance slightly increases with decreased speed due to ice piling up; for middle ship speeds, the ship-ice interaction could remain similar and there is no distinctive change in the ice resistance; for high ship speeds, ice resistance evidently increases with increasing ship speed, which results from strong ship-ice collisions that cause ice pieces to move dramatically.
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| 8. |
- Li, Zhiyuan, 1974, et al.
(författare)
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A comparison of two ship performance models against full-scale measurements on a cargo ship on the Northern Sea Route
- 2021
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Ingår i: Ships and Offshore Structures. - : Informa UK Limited. - 1754-212X .- 1744-5302. ; 16:sup 1, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- The present paper introduces the development and verification of two ship performance models which have been implemented in a voyage planning tool designed for summer Arctic operations of commercial vessels. A novel ice resistance estimation algorithm for ice-floe conditions is implemented in the ship performance models. The fuel consumption predicted using both of the models are compared against full-scale measurements collected on a cargo ship of lower ice-class on the Northern Sea Route. This work found that both models meet the purpose of estimating ship fuel consumption for such a voyage planning tool and identified directions for future efforts. In addition, the typical transit scenarios in summer Arctic conditions presented in this study prove that a voyage planning tool with viable ship performance models facilitates Arctic shipping in a safe and sustainable way.
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| 9. |
- Li, Zhiyuan, 1974, et al.
(författare)
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A comparison of two ship performance models against full-scale measurements on a cargo ship on the Northern Sea Route
- 2020
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Ingår i: Proceedings of The 5th International Conference on Ships and Offshore Structures (ICSOS 2020). ; , s. 279-201
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Konferensbidrag (refereegranskat)abstract
- The present paper introduces the development and verification of two ship performance models which have been implemented in a voyage planning tool designed for Arctic operations of commercial vessels. An ice resistance estimation algorithm for ice-floe conditions is proposed and implemented in the ship performance models. The fuel consumption predicted using both of the models are compared against full-scale measurements collected on a cargo ship on the Northern Sea Route. Two further case studies representing different Arctic transit periods are also investigated. This work found that both models predict ship fuel consumption with good and satisfactory accuracy and identified directions for future efforts. Overall, the demonstrations prove that an Arctic voyage planning tool, combined with ship performance estimates taking into account the effect of ice and other environmental parameters, can facilitate safe and sustainable Arctic shipping.
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| 10. |
- Li, Zhiyuan, 1974, et al.
(författare)
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Cost–benefit analysis of a trans-arctic alternative route to the Suez canal: a method based on high-fidelity ship performance, weather, and ice forecast models
- 2023
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Climate change in recent years has produced viable shipping routes in the Arctic. However, critical uncertainties related to maritime operations in the Arctic make it difficult to predict ship speeds in ice and, thus, the voyage time and fuel costs. Cost–benefit analysis of alternative Arctic routes based on accurate environmental condition modeling is required. In this context, this paper presents a holistic approach that considers the major voyage-related costs of a trans-Arctic route as an alternative to the conventional routes via the Suez Canal Route (SCR) for existing merchant ships. This tool is based on high-fidelity models of ship performance, metocean forecasting, and a voyage optimization algorithm. Case studies are performed based on a general cargo vessel in operation to quantify realistic expenses inclusive of all the major operational, fuel, and voyage costs of the specific voyages. A comparison is made between the total costs of the trans-Arctic route and SCR for different seasons, which proves the economic feasibility of the trans-Arctic route. Overall, this work can provide valuable insights to help policymakers as well as shipbuilders, owners, and operators to assess the potential cost-effectiveness and sustainability of future Arctic shipping, thereby better developing future strategies.
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