| 1. |
- Ni, Bao Yu, et al.
(author)
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Numerical Simulation of an Air-Bubble System for Ice Resistance Reduction
- 2022
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 10:9
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Journal article (peer-reviewed)abstract
- Ships sailing through cold regions frequently encounter floe ice fields. An air-bubble system that reduces friction between the hull and ice floes is thus considered useful for the reduction of ice-induced resistance. In this study, a numerical analysis procedure based on coupled finite volume method (FVM) and discrete element method (DEM) is proposed to simulate complicated hull-water-gas-ice interactions for ice-going ships installed with air-bubble systems. The simulations reveal that after turning on the air-bubble system ice floes in contact with the hull side wall are pushed away from the hull by the gas-water mixture, resulting in an ice-free zone close to the side hull. It is found that the drag reduction rate increases with the increase of ventilation, while the bow ventilation plays a deciding role in the overall ice-resistance reduction. The proposed procedure is expected to facilitate design of new generations of ice-going ships.
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| 2. |
- Ni, Bao Yu, et al.
(author)
-
When Does a Light Sphere Break Ice Plate Most by Using Its Net Buoyance?
- 2023
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 11:2
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Journal article (peer-reviewed)abstract
- A free-rising buoyant sphere can break an ice plate floating above it. The problem is when the light sphere breaks the ice plate most, or the optimal relative density of the sphere which can break the ice plate the most severely. This experimental study was done to answer this problem. A set of experimental devices were designed, and a high-speed camera system was adopted to record the whole dynamic process, including the free-rising of the sphere, the collision between the sphere and the ice plate, the crack initiation and propagation, as well as the breakup of the ice plate. The failure mode of the ice plate under impact load was analyzed. It was found that conical cracks were formed under the reflected tensile wave at the top surface of the ice plate. On this basis, the influences of ice thickness, the initial submergence depth, and the relative density of the sphere on icebreaking were further investigated. An optimal relative density of the sphere was found when the sphere was released at a certain initial submergence depth, at which point the ice was damaged the most severely. For example, when the dimensionless initial submergence depth of the sphere was 2.31, the optimal relative density of the sphere was close to 0.4, with the probability of the ice plate breakup as high as 91.7%. It was also found from the experiments that the degree of damage to the ice plate correlated well with the kinetic energy of the sphere just before collision. Results showed that the optimal relative density can be estimated by theoretical analysis of the kinetic energy of the sphere, which will provide a reference for potential icebreaking applications in the future.
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| 3. |
- Wu, Qi Gang, et al.
(author)
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Ice-Water-Gas Interaction during Icebreaking by an Airgun Bubble
- 2022
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 10:9
-
Journal article (peer-reviewed)abstract
- When an airgun releases high-pressure gas underwater below an ice plate, it is observed that a bubble is formed rapidly while the ice plate is broken fiercely. In order to study the ice-water-gas interaction during this transient and violent phenomenon, a set of laboratory-scale devices was designed and a series of icebreaking experiments were carried out. High-speed photography was used to capture the evolution of the bubble and the ice plate. It was found that the airgun bubble had a unique ‘pear’ shape compared with the spherical bubble generated by electric sparking. The pressure induced by the pulsation of the airgun bubble near a rigid wall was measured by the pressure sensor. The initial shockwave, oscillatory pressure peaks caused by the directional fast air injection, secondary shockwave, and pressure peak caused by the bubble jet impact were clearly recorded. Three damage patterns of ice plates were observed and corresponding reasons were analyzed. The influence of dimensionless parameters, such as airgun-ice distance (Formula presented.) and ice thickness (Formula presented.), was also investigated. The physical mechanism of ice-water-gas interaction was summarized.
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| 4. |
- Xue, Yanzhuo, et al.
(author)
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A combined experimental and numerical approach to predict ship resistance and power demand in broken ice
- 2024
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In: Ocean Engineering. - 0029-8018. ; 292
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Journal article (peer-reviewed)abstract
- Despite its remoteness and hostile environmental conditions, the Arctic holds significant shipping lanes, such as the Northern Sea Route (NSR) and the Northwest Passage (NWP). Typically, merchant ships operate along these routes in summer only, when the dominating type of ice is broken ice. A challenge of operating in such ice conditions is that there is no cost- and time-efficient method for predicting the resulting ice resistance, which makes route planning difficult, among others. To address this challenge, we present and analyze two complementary approaches to predict ship resistance in broken ice, of which one is experimental and the other numerical. The experimental approach makes use of a type of non-refrigerated synthetic model ice made of polypropylene, which makes it possible to test how a ship behaves in broken ice using a conventional non-refrigerated towing tank rather than an ice tank. The numerical approach, in turn, is based on the CFD-DEM method and can be used to consider fluid effects, such as the changes in fluid velocity and ship waves, while the ship is moving ahead. Validation calculations against established empirical approaches indicate that both approaches are reasonably accurate.
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| 5. |
- Zhong, Kai, et al.
(author)
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Direct measurements and CFD simulations on ice-induced hull pressure of a ship in floe ice fields
- 2023
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In: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 272
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Journal article (peer-reviewed)abstract
- Floe ice fields are expected to replace level ice to be the most common environment for future polar sea transportation under the long-term trend of global warming. In this study, the authors aim to develop a viable analysis procedure to predict the ice-induced hull pressure characteristics for ships navigating in floe ice fields. A novel ice model test procedure is established, which is characterized by making use of non-refrigerated synthetic model ice and tactile pressure sensors to measure the hull pressure. The numerical tool is based on a state-of-the-art CFD-DEM numerical framework; a novel method to monitor the hull pressure during the interaction between the hull and ice floes during the CFD-DEM simulations. Statistical analysis indicates the probability distributions of the ice pressure from the experiment and the numerical results are comparable. Besides, the impacts of ship speed and ice floe concentration on the hull pressure distribution are also examined. Increasing speed and ice concentration will make the probability distribution of ice pressure shift towards the high-pressure going interval, resulting in an increased mean of ice pressure. It is also found that increased speed leads to a smaller variance, while increased ice concentration results in a larger variance.
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| 6. |
- Zhong, Kai, et al.
(author)
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Numerical study on the movement pattern of ice around the ship in the broken ice field
- 2023
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In: Proceedings of the International Conference on Port and Ocean Engineering under Arctic Conditions, POAC. - 0376-6756 .- 2077-7841. ; 2023-June
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Conference paper (peer-reviewed)abstract
- Broken ice field is among the common type of ice conditions when ships operate in Arctic navigation, where ships face a significant increase in resistance and local structural safety threats due to the interaction between the ship's hull, water, and broken ice. The hull needs to remove a large amount of broken ice from its path and disturb the surrounding broken ice, and the extent to which can reflect the intensity of the ship-water-ice interaction. In this study, a coupled CFD-DEM approach to simulate ship-water-ice interaction-related phenomena. In the calculation process, rigid particles are considered as non-rebreakable broken ice, while the effect of ship wave variations on the movement of broken ice is taken into account. The "ice boundary layer" (IBL) is found in the numerical results, and distribution of the thickness of "IBL" along the ship's bow is derived and in good agreement with the formula proposed by Aboulazm (1989). After that, the relationship between ship speed on the movement of ice is also studied.
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