• 한국기계가공학회지
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• 제11권6호
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• pp.152-157
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• 2012

This study investigates compressive strength of ice pellet strip which is potential medium for Natural Gas Hydrate(NGH) extruded from die holes of Twin-roll Press for Continuous Pelletizing(TPCP). Recently, the prototype of TPCP is newly developed where ice powder is continuously fed and extruded into strip-type pellet between twin rolls. The system is specifically designed for future expansion towards mass-production of ice pellet strips or solid form of natural gas hydrate. It is shown that the compressive strength of pellet strip heavily depends on factors in extrusion process such as disk size, surface smoothness, ring size, taper shape, feeding mechanism, and rotational speed. Here, the mechanism of TPCP, along with compressive strength of pellets is discussed in terms of its feasibility for producing NGH pellets in the future.

• 대한조선학회논문집
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• 제51권3호
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• pp.254-258
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• 2014

Field trial in ice-covered sea is one of the most important tasks in the design of icebreaking ships. To correctly estimate ice load and ice resistance on ship's hull, It is essential to understand the material properties of sea ice during ice field trials and to perform the proper experimental procedure by gathering sea ice data. A measurement of sea ice properties was conducted during February and March of 2012 with the Korean Icebreaking research vessel "ARAON" in the Amundsen Sea, Antarctica. This paper describes a test procedure to obtain sea ice data which provide basic information to estimate ice loads and icebreaking performance of the ship. The data gathered from sea ice field trials during the 2012 Antarctic voyage of the ARAON includes ice temperature/salinity/density and the compressive/flexural strength of sea ice. This paper analyses the gathered Antarctic sea ice material properties comparing with the previous data obtained during ARAON's Arctic and Antarctic voyages in 2010.

• 대한조선학회논문집
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• 제59권6호
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• pp.355-361
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• 2022

In order to produce model ice sheets having targeted physical properties in accordance with the law of similitude, the ice model basin of Korea Research Institute of Ships and Ocean Engineering carries out a series of processes such as cooling, seeding, freezing, and tempering. Performance in ice field of ice going ships or marine structures is evaluated from model tests in ice conditions made out of a model ice sheet such as level ice, pack ice, brash ice, and ice rubble field, etc. In this study, we investigated effects of micro-bubble layers and seeding of ice nuclei included in the process generating a model ice sheet on change in physical properties of thickness, density, and flexural strength.

• 한국해양공학회지
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• 제11권2호
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• pp.1-10
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• 1997

The interaction of ground ice features with underlying seabed is one of the major considerations in the design of Arctic pipeline systems. Regarding the development of offshore gas field near Sakhalin Island, which is an ice-infested area, in this paper an ice scour model to determine the burial depth of Arctic offshore pipeline is studied. Using a simplified ice-seabed interaction process, ice scour depth is easily estimated. This nonlinear numerical model can simulate the scouring process for various enviromental parameters such as ice mass, incoming velocity, soil strength. This study also deals with interaction forces during the scouring process in sloping seabed conditions and discusses the ice loads that are transmitted through the seabed soil.

• 대한조선학회논문집
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• 제49권1호
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• pp.45-51
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• 2012

Sea ice properties have been considered a key indicator in the structural design criteria of icebreaking vessels and arctic offshore platforms to estimate design ice load and resistance for their safety management in Arctic Ocean. A measurement study of sea ice properties was conducted during July to August of 2011 with the Korean icebreaking research vessel "Araon" around Chukchi Borderland. The sea ice concentration appears to be rapidly decreasing during this cruise. Ice condition seems to be thick second-year ice and multi-year ice and then, a lot of melt ponds were observed in the surface of ice floe. Calculated flexural strength of sea ice was about 250~550kPa, ice thickness was roughly 1.3~3.0m. In this research we performed field experiment to measure ice temperature along the depth, thickness, density, salinity, brine volume ratio and crystal structure. Apparent conductivities derived with the electromagnetic induction instrument were compared to drill hole measurement results and accuracy of sea ice thickness estimation formula was discussed.

• 대한조선학회논문집
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• 제46권6호
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• pp.603-610
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• 2009

Ice load is one of the important design parameters for the construction of icebreaking vessels. In this paper, the design ice load prediction for the icebreaking vessels under normal operating condition in ice-covered sea is discussed. The ice loads under normal operating condition are expected from sea trials in moderate ice conditions. In this sense the extreme ice loads during heavy ramming or accidental collision are not considered. Current study describes the global ice load on the hull of the icebreaking vessels. Available ice load data from full-scale sea trials are collected and analyzed according to various ship-ice interaction parameters including displacement, stem angle, speed of a ship and flexural strength and thickness of sea ice. The ice load prediction formula is compared with the collected full-scale sea trials data and it shows a good agreement.

• 한국지반신소재학회논문집
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• 제12권3호
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• pp.23-29
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• 2013

동결토는 물과 얼음의 상변화에 따라 일반적인 흙과는 다른 거동을 보이며, 동결토의 강도는 온도, 함수비, 시간, 토질 특성 등 다양한 인자에 의해 영향을 받는다. 특히 지반이 동결되는 경우, 얼음과 흙 입자의 결합력에 의해 높은 강도 특성을 보이며, 이때의 전단강도는 흙의 구조적 결합에 영향을 미치는 얼음과 세립분의 함량에 따라 달라지며, 이로 인해 점착력이 동결토의 전단강도에 미치는 영향은 증가한다. 본 논문에서는 동결조건에서 직접전단시험과 일축압축강도시험을 실시하여 온도에 따른 흙의 강도 특성을 확인하였으며, 점착력과 일축압축강도와의 상관관계를 확인하였다.

• 대한조선학회논문집
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• 제58권3호
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• pp.175-181
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• 2021

This study describes the model tests in ice according to the frictional coefficient of an ice-breaking ship and the change in ice resistance by the analysis method for each component of ice resistances. The target vessel is a 90K DWT ice-breaking tanker capable of operating in ARC7 ice conditions in the Arctic Ocean, and twin POD propellers are fitted. The hull was specially painted with four different frictional coefficients on the same ship model. The total ice resistance can be separated by ice breaking, ice buoyancy, ice clearing resistances through the tests in level ice, pre-sawn ice and creep test in pre-sawn ice under sea ice thickness of 1.2 m and 1.7 m. Ice resistance was analyzed by correcting the thickness and bending strength of model ice by the ITTC correction method. As the frictional coefficient between the hull and ice increases, ice buoyancy and clearing resistances increase significantly. When the surface of the hull is rough, it is considered that the broken ice pieces do not slip easily to the side, resulting in an increase in ice buoyancy resistance. Also, the frictional coefficient was found to have a great influence on the ice clearing resistance as the ice thickness became thicker.

• 수산해양기술연구
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• 제58권4호
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• pp.352-358
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• 2022

We explored the frequency response of krill target strength (TS) to understand the Antarctic krill (Euphausia superba) and ice krill (Euphausia crystallorophias) using the stochastic distorted-wave Born approximation (SDWBA) model. The results showed that the distribution of orientation and the fatness factor could significantly impact on the frequency response of TS. Krill TS is clearly depended on acoustic properties, which could affect to estimate the biomass of two krill species. The results provide insight into the importance of understanding TS variation to estimate the Antarctic krill and ice krill biomass, and their ecology related to the environmental features in the Southern Ocean.

• 대한조선학회논문집
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• 제52권2호
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• pp.104-109
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• 2015

The Korea Research Institute of Ships & Ocean Engineering (KRISO) has an ice tank to make a test environment similar to the real ice in the polar sea in order to carry out model tests. One of the most important task of the ice tank is to generate the model ice to have similar material properties as sea ice. The primary properties of sea ice which influence the ice performance of ice breakers and ice-strengthened vessels traveling in the polar sea are ice thickness, flexural strength, density, modulus of elasticity and crystal structure etc. Among them, since the density of model ice influences the buoyance resistance of ice for the ship model, the accurate measurement of ice density should be used to obtain the accurate analysis results from the model test. In this paper, some existing methods to measure the density of model ice are reviewed and a new one is proposed to measure it accurately and easily as possible. In this study, the measuring system including an UTM and several measuring devices was established to obtain the model ice density. Polyethylene and ice specimens are used for a series of repeatable measurement tests. From the results, it was recognized that both of the displacement method and the weight/weight methods gave the stable and favorable tendency.