• Journal of Ocean Engineering and Technology
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• v.34 no.1
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• pp.1-12
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• 2020

Although there are many kinds of advanced ballast water management systems, pioneering studies for ballast-water free ship and minimal ballast water ship concepts are in progress. In this study, the existing alternatives of ballast water are reviewed and a new design concept is studied on the basis of the existing bulk carrier hull form. To develop a new design alternative which has minimal ballast for ballast water discharge free operation, the new concept should have technical feasibilities that are related to the role of the ballast water, berth access, loading constraints, etc. For this purpose, a simplified systems engineering basis design approach is adopted using a business model as the system analysis and control tool. To check the performance feasibility of the new concept, ship resistance performance is reviewed based on a model scale ship resistance performance analysis.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.314-322
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• 2009

Nowadays, maritime communication systems need high data rate, reliability, and consistency in order to equivalently provide navigating ships with diverse multimedia services as in terrestrial communication systems. For this purpose, we conceptualize and design the maritime network for ships equipped with a multiband communication system which cost-effectively supports multimedia services according to several radiofrequency bands, such as HF, VHF, and satellite frequencies. We also introduce two service scenarios targeted for the maritime network; ship multimedia service (SMS) and real-time maritime logistics location tracking (RML2T). In addition, we specify related works according to three lower network layers (i.e., physical, data-link, and network layers) upon designing the network.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.355-364
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• 2010

A session transfer method, referred to as a Recipient Serving-call session control function (S-CSCF) Assured (RSA), is proposed in order to support both session mobility and consistency in IP multimedia subsystem (IMS) based next generation network (NGN). RSA session transfer simplifies a basic session transfer operation specified in [1] by using the user agent client (UAC) like characteristics of an S-CSCF. To show its efficiency, the session transfer delay and the traffic cost of RSA session transfer are investigated and compared with those of existing session transfer applications, including Assured and Consultative session transfers, by practically considering multiple session transfer failures. It is shown that RSA session transfer can further improve user experience by reducing session transfer delay as well as traffic cost than Assured and Consultative session transfers.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.51-56
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• 2006

부유식 해상공항과 같은 초대형 부체 구조물(VLFS)의 연안역 설치 후 발생할 수 있는 배후의 해빈변형을 예측하기 위한 토대를 마련하기 위한 기초 연구를 수행하였다. 이를 위해 일정 사면을 가진 천해역에서의 실험 결과를 통하여 비교적 수심이 깊은 곳에 설치된 매립식 구조물 배후에서의 파랑 및 해빈류를 개관하였으며, 매립식 및 부유식 해상 구조물 설치 시 주변 해역의 파랑 및 해빈류장을 계산하였다. 파랑장에 있어서 라프라스 방정식 토대로 유한요소법을 도입한 3차원 파랑 변형 계산을 수행함으로써 매립식 및 부유식 구조물 모두에 대해 적용 가능하였으며, 해상 구조물의 설치 형식이 매립식 및 부유식 경우에 대해 파랑, 해빈류 분포의 변화를 관찰할 수 있었다.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.92-97
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• 2019

The sea is stratified with water that has different densities because of pressure, temperature, and salinity. When conducting studies of internal waves in the ocean, the fluid is assumed to have layers that have discrete densities. This assumption is made because it is difficult to achieve layers that exhibit gradual changes in the density of the water. In this study, we used previous studies on ocean waves and their radiation issues in the density layer fluid to investigate the characteristics of internal waves in the ocean and their radiation patterns induced by a moving body in a stratified fluid. We also studied the difference in wave radiation between the density gradient layer and the discrete density layer. We found that the wave radiation patterns depended on the velocity of the moving body and the change in the density of the water. The crest apex shift phenomenon was observed in the density gradient in the layer of fluid.

• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.247-256
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• 2021

In order to minimize carbon emissions and greenhouse gas, the Energy Efficiency Design Index (EEDI) has become a major factor to be considered in recent years in a ship's design and operation phases. Energy-Saving Devices (ESDs) improve the EEDI of a vessel and make them environmentally friendly. In this research, the performance of an equalizing duct-type ESD installed upstream of a Korea Research Institute of Ships & Ocean Engineering (KRISO) Container Ship (KCS) model's propeller was investigated by computational fluid dynamics (CFD). Open-source CFD libraries, OpenFOAM, were used for computational analysis of the KCS with and without the ESD to verify the performance improvement. The flow field near the stern region and propulsive coefficients were considered for comparison. The results showed a considerable improvement when an ESD was used on the model. Using different sizes of the duct, the performance of the ESD was also compared. It was observed that with an increased duct size, the propulsive performance was improved.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.97-102
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• 2001

This paper describes an investigation how to carry out model tests of deepwater moorings exceeding the basin depth range. A hybrid mooring model, a combination of mooring lines scaled model and a couple of linear springs, is taken into account as an equivalent substitute of a full depth mooring system. Such an idea is applied to the model test of an OTEC mooring system to be installed in 1000m deep ocean. A 1/25 scaled model test of surface vessel and the upper part of mooring system is performed at ocean engineering basin. Possibility and limitation of the hybrid mooring modeling is discussed.

• Journal of Ocean Engineering and Technology
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• v.33 no.4
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• pp.350-357
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• 2019

The development of marine technology is expected to increase the demand for marine plants because of increasing oil prices. Therefore, there is also expected to be an increase in the demand for cylindrical structures such as URF (umbilical, riser, flowline) structures and spars, which are used operating in various seas. However, a cylindrical structure experiences vortex induced motion (VIM) in a current. In particular, for risers and umbilicals, it is important to identify the characteristics of the VIM because interference between structures can occur. In addition, various studies have been conducted to reduce VIM because it is the cause of fatigue damage to structures. The helical strake, which was developed for VIM reduction, has an excellent VIM reduction performance, but is difficult to install on structures and has a negative effect on heave motion. Therefore, the purpose of this study was to supplement the shortcomings of the helical strake and develop a high-performance reduction device. In the reduction device developed in this study, a string is placed around the structure inside the flow, causing vibration. The vibration of this string causes a small turbulence in the flow field, reducing the VIM effect on the structure. Finally, in this study, the 2-DOF motion characteristics of models without a suppression device, models with a helical strake, and models with a string were investigated, and their reduction performances were compared through model tests.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.81-90
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• 2017

The 1MW OTEC (Ocean Thermal Energy Conversion) platform was designed for application in equatorial seas. In this study, the OTEC platform was investigated using numerical and experimental methods. An octagon-shaped OTEC platform was investigated using the Ocean Engineering Basin of KRISO. These experiments included various tests of regular waves, irregular waves and irregular waves with current (wave+current). The responses of the platform in regular waves showed good agreement between the numerical and experimental results, including the motion RAO, wave run up, and mean drift force. The peak period of heave and pitch motions were observed around 0.5 rad/s, and the effect of the total reflection was found under short wave conditions. The standard deviation (STD) of the platform motion was checked in irregular waves of equatorial and Hawaiian seas. The STD of the pitch was less than $4^{\circ}$ different from the operability requirement under equatorial conditions and the surge STD of the wave frequency showed good agreement between the numerical and experimental results. The STD values of the surge and pitch were increased 66.6% and 92.8% by the current effects in irregular waves, but the pitch STD was less than $4^{\circ}$ under equatorial conditions. This study showed that the STD of the surge was affected by spring effects. Thus, the watch circle of the platform and tension of the mooring lines must be evaluated for a specific design in the future.

• International Journal of Ocean System Engineering
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• v.3 no.4
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• pp.169-174
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• 2013

The computational fluid dynamics software FLUENT is used to calculate and compare the hydrodynamic performance of the propeller-rudder system of a 42-m trawler, which is installed with a ducted propeller. The effects of rudder on the hydrodynamic performance of the ducted propeller and the wake flow behind the propeller are firstly investigated. In addition, the different rudder angles are also considered to further study the performance of this system.