• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.246-252
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• 2018

In this paper, the friction drag force of 3D submerged body is investigated by considering the surface roughness, the first grid height, and the Reynolds number using open CFD source code, OpenFOAM 4.0. A procedure for estimating drag components by CFD code is set up and suggested in this study. In the 3D submerged body, because of the form factor in the 3D computations, the friction resistance with the small roughness of $12{\mu}m$ obtains different result with the smooth wall. As the Reynolds number increased, the boundary layer becomes thinner and the fiction resistance tends to decrease. In the computations for the effect of y+, the friction resistance and wall shear stress are excessively predicted when the y+ value deviates from the log layer. This is presumably because the boundary layer becomes thicker and the turbulence energy is excessively predicted in the nose due to the increase in y+ value. As the roughness increases, the boundary layer becomes thicker and the turbulence kinetic energy on the surface increases. From this study, the drag estimation method, considering the roughness by numerical analysis for ships or offshore structures, can be provided by using the suggested the y+ value and surface roughness with wall function.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.33-44
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• 2008

Most of the civil structure - bridges, offshore structures, plant, etc. - have been designed by the classical approaches which deal with all the design parameters as deterministic variables. However, some more advanced techniques are required to evaluate the inherent randomness and uncertainty of each design variable. In this research, a seismic safety assessment algorithm based on the structural reliability analysis has been formulated and computerized for more reasonable seismic design of turbine-generator foundations. The formulation takes the design parameters of the system and loading properties as random variables. Using the proposed method, various kinds of parametric studies have been performed and probabilistic characteristics of the resulted structural responses have been evaluated. Afterwards, the probabilistic safety of the system has been quantitatively evaluated and finally presented as the reliability indexes and failure probabilities. The proposed procedure is expected to be used as a fundamental tool to improve the existing design techniques of turbine-generator foundations.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.180-184
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• 2016

Legislative and regulatory actions regarding the exhaust gas from ships are being strengthened by both international organizations and national governments, to protect human health and the environment. Exhaust gas traps are excluded from exhaust gas regulation applications, but, recently, the United States, Britain, and other developed countries have examined a variety of ways to improve the system, including the introduction of electric propulsion systems to prevent air pollution generated by naval ships. This study investigates a large number of smoke problems of naval diesel engines to verify the effect of improving the nozzle characteristics. An exhaust gas emission measurement method to determine the quality of pollutant exhaust gas generated during low-load operation is proposed through the research methodology of the smoke problem. It was confirmed that the emissions value is improved by decreasing the nozzle hole diameter and increasing the injection pressure. At the same time, the flow rate decrease equation and setting up a test memo based on the nozzle diameter confirmed that the fuel consumption, to which the nozzle diameter in the flow path is related, is reduced.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.210-216
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• 2016

Malfunctioning of telecom systems can have serious implications on the safe navigation and operation of vessels and off-shore plants. Most safety-related accidents incur significant monetary damages and pollution due to complicated arrangements of the working environments and facilities. Therefore, an automated monitoring system that can collect data from configured telecom equipment connected to a network based on IP is required to ensure safe navigation and operation of such crucial institutions. This paper reports a list of such system requirements, system functions, and user-centered requirements based on the NORSOK T-100 (a standard of telecom management system). These findings were made through research with the newly designed and developed telecom management system (TMS). The TMS was tested by a testbed configured with CCTV, PA/GA, and other network equipment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.4
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• pp.437-448
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• 2015

In this paper, smartphone based measuring device was developed by integration of several sonsors such as moving, temperature, pulsation, respiration and hearing and sever/client programs was developed for the data acquisition and communication between smartphone and server computer. Then, the concept of CSI(combined safety index) was proposed for the comprehensive diagnositcs of workers status. For the validation of the proposed concept, the real data was acquired by boarding at training ship of korea maritime and ocean university. The acquired data was analyzed with the stochastical method of regressionn, then the meaningful result was driven that could explain the relation between the risky situation and the measured chronical data.

• Plant Journal
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• v.16 no.3
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• pp.47-52
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• 2020

This study investigated the methodologies to enhance the corrosion resistance and the ways to measure for subsea equipment made of aluminum. The methodologies for the anticorrosion were cathodic protection, conversion coating, anodizing and organic coating. The simply analyzed ways to measure the corrosion resistance were Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS), Glow discharge optical emission spectrum spectroscopy (GD-OES), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Scanning Vibrating Electrode Technique (SVET), contact angle and interfacial tension. The most widely used tools for increasing the corrosion resistance were the anodizing and the organic coating. Many ways were evenly used to measure corrosion. The methods more frequently utilized were SEM for the surface investigation and the contact angle to evaluate the corrosion resistance.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1423-1430
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• 2003

In this paper, we develop a real time monitoring system to detect third-party damage on natural gas pipeline. When the damage due to third-party incidents causes an immediate rupture, the developed on-line monitoring system can help reducing the sequences of event at once. Moreover, since many third-party incidents cause damage that does not lead to immediate rupture but can grow with time, the developed on-line monitoring system can execute a significant role in reducing many third-party damage incidents. Also, when the damage is given at a point on natural gas pipeline, the acoustic wave is propagated very fast about 421.3 m/s. Therefore, the data processing time should be very short in order to detect precisely the impact position. Generally, the pipeline is laid under ground or sea and the length is very long. So a wireless data communication method is recommendable and the sensing positions are limited by laid circumstance and setting cost of sensors. The calculation and monitoring software is developed by an algorithm using the propagation speed of acoustic wave and data base system based on wireless communication and DSP systems. The developed monitoring system is examined by field testing at Balan pilot plant, KOGAS being done in order to demonstrate its validity through reactive detection of third-party contact with pipelines. Furthermore, the development system was set at the practical pipelines such as an offshore pipeline between two islands Yul-Do and Youngjong-Do, and a land branch of Pyoungtaek, Korea and it has been operating in real time.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.66-71
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• 2011

Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.690-695
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• 2014

In this paper, we develop a explosion-proof LED lighting (Ex circuit) circuit of Explosion-proof LED Signal Lamp (Ex LSL) to utilize the core module of the explosion-proof Local Control System (Ex LCS) for offshore plant applications. And then analyzed its electrical, optical and thermal characteristics. Ex circuit was applied input voltage from AC/DC(12~254) V. In this experiments, stable light-on characteristics were confirmed by eyes for the every input voltages with min. 78,462 and max. $517,975cd/m^2$ of luminance. also Output current and output luminance was made proportional. Because the measured maximum surface temperature of Ex circuit was $54.23^{\circ}C$ at AC 48 V, Ex circuit was rated with T6 of temperature class. Finally, Ex circuit was shown stable light on characteristics under the $-50^{\circ}C$ and $60^{\circ}C$ during 12 hours of test period.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.199-206
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• 2015

In this study, a new diagnosis method which can predict the working states of a pipe or its element in realtime is proposed by using an artificial neural network. The displacement data of an inspection element of a piping system are obtained by the use of PIV (particle image velocimetry), and are used for teaching a neural network. The measurement system consists of a camera, a light source and a host computer in which the artificial neural network is installed. In order to validate the constructed monitoring system, performance test was attempted for two kinds of mobile phone of which vibration modes are known. Three values of acceleration (minimum, maximum, mean) were tested for teaching the neural network. It was verified that mean values were appropriate to be used for monitoring data. The constructed diagnosis system could monitor the operation condition of a gas pipe.