• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.4
• /
• pp.306-312
• /
• 2018

To navigate in ice-covered waters, the ice-breaking process is required. The ice-breaking mode depends on material properties of sea ice and ice conditions. The ice-breaking mode is classified into ramming and continuous ice-breaking. The ramming is effective on large ice features, such as thick ice ridge and icebergs, and the continuous ice-breaking is on level ice. In general, the impact time duration of crushing or bending on ice sheets is from 0.2 to 1.0 second. However, impact duration in ramming will be increased. The Korean ice-breaking research vessel ARAON conducted her research voyage in the Antarctic sea during the winter of 2012. The IBRV ARAON measured strain in ramming and continuous ice-breaking. Strain gauge signals were recorded during the planned ice-breaking performance and the unplanned ice transits in heavy ice conditions. The aim of this study is to investigate the ice load signals measured in ramming processes under the heavy ice condition. Based on the time history of the signals, a raising time, a half-decaying time and time duration were investigated and compared with the previous study which was suggested the five profiles of the ice load signals.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.667-679
• /
• 2020

As the LNG carrier operates in ice covered waters, it is key to ensure the overall safety, which is related to the coupling effect of ice-breaking process and internal liquid sloshing. This paper focuses on the sloshing simulation of the ice-breaking LNG carrier, and the numerical method is proposed using Circumferential Crack Method (CCM) and Volume of Vluid (VOF) with two main key factors (velocity νx and force Fx). The ship motion analysis is carried out by CCM when the ship navigates in the ice-covered waters with a constant propulsion power. The velocity νx is gained, which is the initial excitation condition for the calculation of internal sloshing force Fx. Then, the ship motion is modified based on iterative computations under the union action of ice-breaking force and liquid sloshing load. The sloshing simulation under the LNG tank is studied with the modified ship motion. Moreover, an ice-breaking LNG ship with three-leaf type tank is used for case study. The internal LNG sloshing is simulated with three different liquid heights, including free surface shape and sloshing pressure distribution at a given moment, pressure curves at monitoring points on the bulkhead. This present method is effective to solve the sloshing simulation during ice-breaking process, which could be a good reference for the design of the polar ice-breaking LNG carrier.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.6
• /
• pp.353-364
• /
• 2020

This paper presents the semi-analytical ice load calculation methods that are useful to simulate the ice-breaking process. Since the semi-analytical methods rely on the previously developed closed form equations or numerical analysis results, the user's exact understanding for the equations must be supported in order to use the methods properly. In this study, various failure modes of ice such as local crushing, in-plane splitting failure, out-of-plane bending failure and radial or circumferential cracking with rotation of the broken ice floe are considered. Based on the presented methods, the fracture modes were evaluated according to the size and thickness of ice. In addition, time series analysis for the ice-breaking process was performed on several ice conditions and the results were analyzed.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.2
• /
• pp.796-808
• /
• 2019

In this paper, a Smoothed Particle Hydrodynamics (SPH) method is extended to simulate the ice failure process and ice-ship interactions. The softening elastoplastic model integrating Drucker-Prager yield criterion is embedded into the SPH method to simulate the failure progress of ice. To verify the accuracy of the proposed SPH method, two benchmarks are presented, which include the elastic vibration of a cantilever beam and three-point bending failure of the ice beam. The good agreement between the obtained numerical results and experimental data indicates that the presented SPH method can give the reliable and accurate results for simulating the ice failure progress. On this basis, the extended SPH method is employed to simulate level ice interacting with sloping structure and three-dimensional ice-ship interaction in level ice, and the numerical data is validated through comparing with experimental results of a 1:20 scaled Araon icebreaker model. It is shown the proposed SPH model can satisfactorily predict the ice breaking process and ice breaking resistance on ships in ice-ship interaction.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.1
• /
• pp.23-34
• /
• 2020

This paper covers the development of prediction techniques for ice load on ice-breakers operating in continuous ice-breaking under level ice conditions using particle-based continuum mechanics. Ice is assumed to be a linear elastic material until the fracture occurs. The maximum normal stress theory is used for the criterion of fracture. The location of the crack can be expressed using a local scalar function consisting of the gradient of the first principal stress and the corresponding eigen-vector. This expression is used to determine the relative position of particle pair to the new crack. The Hertz contact model is introduced to consider the collisions between ice fragments and the collisions between hull and ice fragments. In order to verify the developed technique, the simulation results for the three-point bending problems of ice-specimen and the continuous ice-breaking problem around a wedge-type model ship with bow angle of 20° are compared with the experimental results carrying out at Korea Research Institute of Ships and Ocean Engineering (KRISO).

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.3
• /
• pp.228-234
• /
• 2016

Recent icebreaking ships need to be designed to enhance not only icebreaking capability but also turning ability. For the evaluation of ice resistance induced by an icebreaking hull form, HHI (Hyundai Heavy Industries) has developed the hybrid empirical formulas (Park et al., 2015) by considering the geometrical hull shape features, such as waterline and underwater sections. However, the empirical formulas have inherent limits to the precise estimation of the icebreaking and turning ability because the breaking process and the resulting pattern are ignored. For this reason, numerical calculation in time domain is performed to predict the icebreaking process and pattern. In the simulation, varying crushing stress according to velocity vectors and contact areas between hull and ice is newly introduced. Moreover, the simulation results were verified by comparing them with the model test results for three different bow-first icebreaking models.

• The Journal of Engineering Geology
• /
• v.32 no.1
• /
• pp.113-126
• /
• 2022

The tectonic history of the Chukchi Abyssal Plain in the Amerasia Basin, Arctic Ocean, has not been fully explored due to the harsh conditions of sea ice preventing detailed observation. Existing models of the tectonic history of the region provide contrasting interpretation of the timing of formation of the crust (Mesozoic to Cenozoic), crust type (from hyper-extended continental crust to oceanic crust), and formation process (from parallel/fan-shaped rifting to transformation faulting). To help determine the age of the oceanic crust, the geothermal gradient was measured at three stations in the south of abyssal plain at depth of 2,160-2,250 m below sea level. Heat flow measurement stations were located perpendicular to the spreading axis over a 40 km-long transect. In-situ thermal conductivity measurement, corrected by the laboratory test, gave observed marine heat flows of 55 to 61 mW/m². All measurements were taken during Arctic expeditions in 2018 (ARA09C expedition) and 2021 (ARA12C expedition) by the Korean ice-breaking research vessel (IBRV) Araon. Given the assumption of oceanic crust, the results correspond to formation in the Late Cretaceous (Mesozoic). The inferred age supports the hypothesis of formation activated by the opening of the Makarov Basin during the Late Mesozoic-Cenozoic. This would make it contemporaneous with rifting of the Chukchi Border Land immediately east of the abyssal plain. The heat flow data indicate the base of the gas hydrate stability zone is located 332-367 m below the seafloor, this will help to identify the gas hydrate-related bottom simulating reflector in the future seismic survey, as already identified on the Chukchi Plateau. Further geophysical surveys, including heat flow measurements, are required to increase our understanding of the formation process and thermal mantle structure of the abyssal plain.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.11 no.1
• /
• pp.137-158
• /
• 2009

This study is to find the causes of the current situations of conflict between generations in regards to succession of their family farm, for the target group of graduates Korea National Agricultural College of the year 2008 and their parents. This study aims at finding a way of controlling and solving the conflicts, and of developing a course of education and training, so that through this process they can come to a rational conclusion to the conflicts that arise regarding succession of the farm, in a climate of harmony and peace. It is found that communication between parents and graduates has normally gone on well, but specific problems related to management of the farm are often present. Furthermore, there is often lack of trust and promise between the parties which often causes difficulties in preparation for the succession of the farm. On the basis of these observation, we have designed and implemented an education workshop and training, as a program in which parents and their successors participated. As a result, we found it to be very effective, but it was also found to be in need of some changes. The workshop is to be implemented in two separate stages. The first stage should focus on communication and trust between family members. Firstly, they are given the opportunity to share the list of concerns withone another, as an ice breaking activity. Secondly, they can present their own hopes or wishes. And lastly, they can communicate with one another in an effort to find resolutions that will be keep both parties satisfied. The second stage should be aimed at establishing agreements concerning succession of the farm in a harmonious and peaceful manor; the second stage is also an opportunity to discuss 'Farm management and succession'. The Korea National Agricultural College (KNAC) is in the pursuit of fostering agricultural CEO's for the future of Korea. KNAC is currently implementing a very unique system of interviews in which parents participate together with students, in order to help them make a plan for rational management of their farm and smooth succession of the farm. Although KNAC now has students present a blueprint of their own unique business plans as a graduation thesis, it is necessary for KNAC to complement this system with education and training regarding the succession of family farms. Furthermore, KNAC should also develop an education and training program that is separate for this purpose, and make it a regular course of study of KNAC in the future.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.10 no.1
• /
• pp.3-27
• /
• 2008

This study is to find the causes of the current situations of conflict between generations in regards to succession of their family farm, for the target group of graduates of the year 2008 and their parents. This study also aims at finding a way of controlling and solving the conflicts, and of developing a course of education and training, so that through this process they can come to a rational conclusion to the conflicts that arise regarding succession of the farm, in a climate of harmony and peace. It is found that communication between parents and graduates has normally gone on well, but specific problems related to management of the farm are often present. Furthermore, there is often lack of trust and promise between the parties which often causes difficulties in preparation for the succession of the farm. On the basis of these observation, we have designed and implemented an education workshop and training, as a program in which parents and their successors participated. As a result, we found it to be very effective, but it was also found to be in need of some changes. The workshop is to be implemented in two separate stages. The first stage should focus on communication and trust between family members. Firstly, they are given the opportunity to share the list of concerns withone another, as an ice breaking activity. Secondly, they can present their own hopes or wishes. And lastly, they can communicate with one another in an effort to find resolutions that will be keep both parties satisfied. The second stage should be aimed at establishing agreements concerning succession of the farm in a harmonious and peaceful manor; the second stage is also an opportunity to discuss 'Farm management and succession'. The Korea National Agricultural College (KNAC), as a state college, is in the pursuit of fostering agricultural CEO's for the future of Korea. KNAC is currently implementing a very unique system of interviews in which parents participate together with students, in order to help them make a plan for rational management of their farm and smooth succession of the farm. Although KNAC now has students present a blueprint of their own unique business plans as a graduation thesis, it is necessary for KNAC to complement this system with education and training regarding the succession of family farms. Furthermore, KNAC should also develop an education and training program that is separate for this purpose, and make it a regular course of study of KNAC in the future.