• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.421-426
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• 2019

The directivity of an underwater sound source should be measured in an acoustically open field such as a calm sea or lake, or an anechoic water tank facility. However, technical difficulties arise when practically implementing this in open fields. Signal processing-based techniques such as a sound intensity method and near-field acoustic holography have been adopted to overcome the problem, but these are inefficient in terms of acquisition and maintenance costs. This study established a simple directivity estimation technique with data acquisition, filtering, and analysis tools. A numerical simulation based on an acoustic radiosity method showed that the technique is practicable for sound source directivity estimation in a diffused reverberant acoustic field like a reverberant water tank.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.421-431
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• 2017

A process-centric simulation modeling method has been proposed to define a shipbuilding simulation model. Existing modeling methods have limitations for expressing various production information for a shipyard. The advanced process-centric modeling method proposed in this paper offers an improvement, effectively representing production information and constraints for a shipyard. To achieve this, a method and diagram components to define a process-centric simulation model in detail have been suggested. The modeling method can assign priorities when multiple products and facilities are assigned to the process. And layer concept was applied to express simulation model with hierarchical structure. To verify the effectiveness of the modeling method, comparative analysis has been performed and the actual shipbuilding process has been modeled using the proposed method. When a single facility was used for various purposes, we found that the proposed method was more advantageous than existing methods. As a result, it was possible to express constraints and flows that were difficult to identify with existing process-centric simulation modeling methods, and the methods were improved for use in shipyard production planning verification simulations.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.367-371
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• 2018

Plywood is one of the important materials in LNG cargo containment systems, and, due to the characteristics of the wood, its properties vary greatly depending on the humidity conditions in the storage facility. Due to the distribution environment of plywood, there is a high probability of long-term exposure to the domestic seasonal environment. Considering an environment in which the humidity changes greatly according to the seasons in Korea and the characteristics of the wood, it is necessary to acquire data on changes in the characteristics of the plywood for accurate quality control. In this study, the moisture content of plywood was determined experimentally to reflect the seasonal environmental conditions of shipyards in Korea. A noticeable change in the thermal conductivity was confirmed experimentally.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.1
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• pp.134-137
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• 2020

Recently, there are emphasized to support the maintenance and management system of vessels using acquired data from engine part equipment. But, there are limitations for data exchange and management. To solve the problem, the ISO published ISO 19847 and 19848. In this paper, we analyze the ISO 19848 requirements related to identify data channel ID for ship equipment, and propose the examples for applying encoding techniques. In addition, we suggest the proposed technique for applying of managing the failure and maintenance type of the ship's engine part facilities by examples. If this method is applied, the vessel's equipment can exchange data through the sharing of the code table, and express what response is needed or acted, including where the failure occurred.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.64-70
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• 2008

A full-scale field experiment is an important part in the design of ships and offshore structures. Full-scale tests in the ice-covered sea, however, are usually very expensive and difficult tasks. Model tests in a refrigerated ice tank may substitute this difficulty of full-scale field tests. One of the major tasks to perform proper model tests in an ice towing tank is to select a realistic material for model ice which shows correct similitude with natural sea ice. This study focuses on the testing material properties and the selection of model ice material which will be used in an ice model basin. The first Korean ice model basin will be constructed at the Maritime & Ocean Engineering Research Institute (MOERI) in 2009. With an application to the MOERI ice model basin, in this study the material properties of EG/AD/S model ice of IOT (Institute for Ocean Technology) Canada, were tested. Through comprehensive bending tests, the elastic modulus and the flexural strength of EG/AD/S model ice were evaluated and the results were compared with published test results from Canada. Instead of using an ice model basin, a cold room facility was used for making a model ice specimen. Since the cold room adopts a different freezing procedure to make model ice, the strength of the model ice specimen differs from the published test results. The reason for this difference is discussed and the future development for a making model ice is recommended.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.1
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• pp.14-24
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• 2013

The marine leisure industry in Korea has been the focus of the power of economic growth and the creation of jobs in recent years. In this regard, many studies concerning marine leisure are on-going in various fields. In this paper, developed a layout system and algorithm can resolve the factory and facility layout problem. For a layout design of leisure-boat factories, the leisure-boat production process is analyzed in order to derive standard production space elements for the layout of the factory. Based on the results, a draft design of the factory layout is carried out based on the manpower planning data, as well as the characteristics and relationships of each process data. A layout design of this paper can be verified through a factory simulation solution and we suggest the verification method using a SBD(simulation based design) methodology. The layout system takes into account the user's accessibility and extendibility, so it is web-oriented and uses RIA (rich Internet Application) technology. Furthermore, the system and layout algorithm of this paper are verified with samples data that show the efficient factory arrangement and practical application method.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.5 s.149
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• pp.550-559
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• 2006

A design procedure for a ship with minimum total resistance was developed using a numerical optimization method called SQP(Sequential Quadratic Programming) and a CFD technique based on the Rankine source panel method with the nonlinear free surface boundary conditions. During the whole optimization process the geometry of the hull shape was represented based on the NURBS(Non-uniform rational B-spline) technique and the modification of the hull shape was controlled using the Bell-shaped distribution function to keep the fairness of the hull shape before and after the hull modification. The numerical analysis was carried out using 4000TEU container ship in the towing tank facility installed in the Pusan national university to know the validity of the developed algorithm for this study. As the results of the numerical analysis it proved that the resistance of the optimized hull is conspicuously reduced in comparison with the original hull in a wave-making resistance point of view.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.3 s.153
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• pp.296-304
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• 2007

The objective of this paper is to investigate the dynamic strength characteristics of LNG carriers cargo containment system under impact loads experimentally. The material properties were experimentally obtained for individual components of MARK III insulation system. A series of impact tests was performed using a custom-built drop experiment facility as varying heights and weights of the drop object. Crack initiation and propagation were measured during the cyclic dry drop experiment. The quantitative relationship between impact load and crack initiation as well as the cycle number and crack propagation were reported.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.244-258
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• 2015

The horizontal stability of a Single-Point Moored (SPM) Floating Liquefied Natural Gas (FLNG) facility is investigated. Both numerical and experimental studies have been conducted for this SPM FLNG. The numerical simulations feature well the experimental data. The effects of the turret locations are studied based on the validated numerical model. Statistic results of the vessel's motions with different turret locations are conducted and compared. The results show that the longitudinal location of the turret has a significant influence on the horizontal stability, which has a strong relationship with the yaw and roll motions. The calculated top tensions on the hawsers also develop a regular change as changing the turret's location. The investigation will provide a brief of principles with more details for the design of the ongoing project.