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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Ocean Engineering and Technology
Journal Basic Information
Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 28, Issue 6 - Dec 2014
Volume 28, Issue 5 - Oct 2014
Volume 28, Issue 4 - Aug 2014
Volume 28, Issue 3 - Jun 2014
Volume 28, Issue 2 - Apr 2014
Volume 28, Issue 1 - Feb 2014
Selecting the target year
Study on Resistance Characteristics of 50-ft class CFRP Power Yacht
Jeong, Uh-Cheul ; Ryu, Cheol-Ho ; Oh, Dae-Kyun ; Hong, Ki-Sup ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 493~499
DOI : 10.5574/KSOE.2014.28.6.493
The resistance performances were studied for two 50-ft-class power yachts made of carbon fiber reinforced plastic (CFRP) with different hull form characteristics using model tests. The tests were carried out at a high-speed circulating water channel (CWC) for the 16–38 knot range. The total resistance, trim, and sinkage were measured, and the results were compared with wave patterns. The results showed that a chine position at the draft line had a strong effect on the planning performance and resistance performance in a certain velocity range.
Study on Flow Analysis of Three-Dimensional Screw Propeller With Respect to Rotational Speed Variable
Moon, Byung-Young ; Sun, Min-Young ; Lee, Ki-Yeol ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 500~507
DOI : 10.5574/KSOE.2014.28.6.500
This study aimed at conducting a flow analysis of the pressure distribution, discharge flow rate, and consequent thrust force according to the rotational speed of a three-dimensional screw propeller, and then investigating the effect of the rotational speed on the characteristics of the screw propeller by varying the relevant speed (3200, 2400, 1600, 800 rpm). In particular, the computational domain was considered by the analysis in the blades and outlet chamber, using boundary conditions. The difference between the minimum and maximum pressures was 5.5 MPa under the given conditions. The discharge flow rate at this pressure difference was on the level of 1956.67 kg/s, as a thrust force of 47083.7 T(N) was obtained. This study showed that the discharge flow rate linearly increased with the rotational speed, proportional to the RPM, while the thrust force was gradually and steadily increased with the relevant speed. In addition, it was proved that the occurrence of cavitation under the given conditions was closely related to the decrease in the durability of the screw propeller because the thrust force depends on the speed.
Numerical Study on Wave-Induced Motion Response of Tension Leg Platform in Waves
Cho, Yoon Sang ; Nam, Bo Woo ; Hong, Sa Young ; Kim, Jin Ha ; Kim, Hyun Jo ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 508~516
DOI : 10.5574/KSOE.2014.28.6.508
A numerical method to investigate the non-linear motion characteristics of a TLP is established. A time domain simulation that includes the memory effect using the convolution integral is used to consider the transient effect of TLP motion. The hydrodynamic coefficients and wave force are calculated using a potential flow model based on the HOBEM(higher order boundary element method). The viscous drag force acting on the platform and tendons is also considered by using Morison’s drag. The results of the present numerical method are compared with experimental data. The focus is the nonlinear effect due to the viscous drag force on the TLP motion. The ringing, springing, and drift motion are due to the drag force based on Morison's formula.
Numerical Model of Heat Diffusion and Evaporation by LNG Leakage at Membrane Insulation
Lee, Jang Hyun ; Kim, YoonJo ; Hwang, Se Yun ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 517~526
DOI : 10.5574/KSOE.2014.28.6.517
The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.
Relation Between Measured Sea Ice Thickness and Freeboard on Chukchi and Beaufort Seas
Jeong, Seong-Yeob ; Choi, Kyungsik ; Cho, Seong-Rak ; Kang, Kuk-Jin ; Lee, Chun-Ju ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 527~532
DOI : 10.5574/KSOE.2014.28.6.527
The thickness of Arctic sea ice is a particularly significant factor in Arctic shipping and other ice-related research areas such as scientific sea ice investigations and Arctic engineering. In this study, the relation between the measured sea ice thickness and freeboard on the Chukchi and Beaufort Seas during the 2010 and 2011 Arctic cruise of the icebreaking research vessel "Araon" were considered. An assumption of hydrostatic equilibrium was used to estimate the ice thickness as a function of the freeboard. Then, to examine the degree of error, a sensitivity analysis of the thickness estimation of the sea ice was conducted. The error in the density and depth of the snow and the error in the density of the seawater were subordinate parameters, but the density of the ice and the freeboard were the primary parameters in the error calculation. The presented relation formula showed fairly close agreement between the calculated and measured results at a freeboard of >0.24 m.
Case Study for Development of Maintenance System for Equipment of LNG-FPSO Topside
Lee, Soon-Sup ; Kim, Jong-Wang ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 533~539
DOI : 10.5574/KSOE.2014.28.6.533
A maintenance system for an offshore plant uses an optimal maintenance method, process, and period based on operation information data and economic evaluation techniques. Maintenance is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating. A maintenance system is based on the use of real-time data to prioritize and optimize the LNG-FPSO topside equipment resources.
Low Heat Input Welding to Improve Impact Toughness of Multipass FCAW-S Weld Metal
Bang, Kook-soo ; Park, Chan ; Jeong, Ho-shin ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 540~545
DOI : 10.5574/KSOE.2014.28.6.540
Multipass self-shielded flux cored arc welding with different heat inputs (1.3–2.0 kJ/mm) was conducted to determine the effects of the heat input on the proportion of the reheated region, impact toughness, and diffusible hydrogen content in the weld metal. The reheated region showed twice the impact toughness of the as-deposited region because of its fine grained ferritic-pearlitic microstructure. With decreasing heat input, the proportion of the reheated region in the weld metal became higher, even if the depth of the region became shallower. Accordingly, the greatest impact toughness, 69 J at −40℃, was obtained for the lowest heat input welding, 1.3 kJ/mm. Irrespective of the heat input, little difference was observed in the hardness and diffusible hydrogen content in the weld metal. This result implies that low heat input welding with 1.3 kJ/mm can be performed to obtain a higher proportion of reheated region and thus greater impact toughness for the weld metal without the concern of hydrogen cracking.
Stabilization of Underwater Glider by Buoyancy and Moment Control: Feedback Linearization Approach
Jee, Sung Chul ; Lee, Ho Jae ; Kim, Moon Hwan ; Moon, Ji Hyun ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 546~551
DOI : 10.5574/KSOE.2014.28.6.546
This paper addresses a feedback linearization control problem for the nonlinear dynamics of an underwater glider system. We consider the buoyancy and moment as control inputs, which come from the mass variation and elevator control, respectively. Moment-to-force coupling increases the nonlinearities, which make the controller design difficult. By using a feedback linearization technique, we convert the nonlinear underwater glider to an equivalent linear model and design a linear controller. The controller for the equivalent converted linear system is designed using sufficient conditions in terms of linear matrix inequalities. Then, the control input of the nonlinear model of an underwater glider is formulated from the linear control input. An experimental examination is implemented to verify the effectiveness of the proposed technique.
Feature Extraction Algorithm for Underwater Transient Signal Using Cepstral Coefficients Based on Wavelet Packet
Kim, Juho ; Paeng, Dong-Guk ; Lee, Chong Hyun ; Lee, Seung Woo ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 552~559
DOI : 10.5574/KSOE.2014.28.6.552
In general, the number of underwater transient signals is very limited for research on automatic recognition. Data-dependent feature extraction is one of the most effective methods in this case. Therefore, we suggest WPCC (Wavelet packet ceptsral coefficient) as a feature extraction method. A wavelet packet best tree for each data set is formed using an entropy-based cost function. Then, every terminal node of the best trees is counted to build a common wavelet best tree. It corresponds to flexible and non-uniform filter bank reflecting characteristics for the data set. A GMM (Gaussian mixture model) is used to classify five classes of underwater transient data sets. The error rate of the WPCC is compared using MFCC (Mel-frequency ceptsral coefficients). The error rates of WPCC-db20, db40, and MFCC are 0.4%, 0%, and 0.4%, respectively, when the training data consist of six out of the nine pieces of data in each class. However, WPCC-db20 and db40 show rates of 2.98% and 1.20%, respectively, while MFCC shows a rate of 7.14% when the training data consists of only three pieces. This shows that WPCC is less sensitive to the number of training data pieces than MFCC. Thus, it could be a more appropriate method for underwater transient recognition. These results may be helpful to develop an automatic recognition system for an underwater transient signal.
Trajectory Optimization for Underwater Gliders Considering Depth Constraints
Yoon, Sukmin ; Kim, Jinwhan ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 560~565
DOI : 10.5574/KSOE.2014.28.6.560
In this study, the problem of trajectory optimization for underwater gliders considering depth constraints is discussed. Typically, underwater gliders are controlled to dive and climb in a saw-tooth pattern at constant gliding angles. This approach is effective and close to optimal for deep water applications. However, the optimal path deviates from the saw-tooth path in shallow water conditions. This study focuses on finding more efficient gliding paths that can minimize the traverse time in the horizontal plane when the water depth is limited. The trajectory optimization problem is formulated into a minimum time control problem with inequality path constraints and hydrodynamic drag effects. A numerical approach based on the pseudo-spectral method is adopted as a solution approach, and the simulation results are presented.
Analysis of Integrated Navigation Performance for Sensor Selection of Unmanned Underwater Vehicle (UUV)
Yoo, Tae-Suk ; Kim, Moon Hwan ;
Journal of Ocean Engineering and Technology, volume 28, issue 6, 2014, Pages 566~573
DOI : 10.5574/KSOE.2014.28.6.566
This paper presents the results of an integrated navigation performance analysis for selecting the sensor of an unmanned underwater vehicle (UUV) using Monte Carlo numerical simulation. An inertial measurement unit (IMU) and Doppler velocity log (DVL) are considered to build the integrated navigation system. The position error and price of the sensor are selected as performance indices to evaluate the volunteer integrated navigation systems. Monte-Carlo simulation is introduced to analyze the circular error probability (CEP) and its variance. Simulation results provide the proper sensor combination for integrated navigation in relation to the performance and price.