Go to the main menu
Skip to content
Go to bottom
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
Editor in Chief :
Volume & Issues
Volume 24, Issue 6 - Dec 2010
Volume 24, Issue 5 - Oct 2010
Volume 24, Issue 4 - Aug 2010
Volume 24, Issue 3 - Jun 2010
Volume 24, Issue 2 - Apr 2010
Volume 24, Issue 1 - Feb 2010
Selecting the target year
A Far Field Solution of the Slowly Varying Drift Force on the Offshore Structure in Bichromatic Waves-Three Dimensional Problems
Lee, Sang-Moo ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 1~6
A far field approximate solution of the slowly varying force on a 3 dimensional offshore structure in gravity ocean waves is presented. The first order potential, or at least the far field form of the Kochin function, of each frequency wave is assumed to be known. The momentum flux of the fluid domain is formulated to find the time variant force acting on the floating body in bichromatic waves. The second order difference frequency force is identified and extracted from the time variant force. The final solution is expressed as the circular integration of the product of Kochin functions. The limiting form of the slowly varying force is identical to the mean drift force. It shows that the slowly varying force components caused by the body disturbance potential can be evaluated at the far field.
Research on Wind Waves Characteristics by Comparison of Regional Wind Wave Prediction System and Ocean Buoy Data
You, Sung-Hyup ; Park, Jong-Suk ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 7~15
Analyses of wind wave characteristics near the Korean marginal seas were performed in 2008 and 2009 by comparisons of an operational wind wave forecast model and ocean buoy data. In order to evaluate the model performance, its results were compared with the observed data from an ocean buoy. The model used in this study was very good at predicting the characteristics of wind waves near the Korean Peninsula, with correlation coefficients between the model and observations of over 0.8. The averaged Root Mean Square Error (RMSE) for 48 hrs of forecasting between the modeled and observed waves and storm surges/tide were 0.540 m and 0.609 m in 2008 and 2009, respectively. In the spatial and seasonal analysis of wind waves, long waves were found in July and September at the southern coast of Korea in 2008, while in 2009 long waves were found in the winter season at the eastern coast of Korea. Simulated significant wave heights showed evident variations caused by Typhoons in the summer season. When Typhoons Kalmaegi and Morakot in 2008 and 2009 approached to Korean Peninsula, the accuracy of the model predictions was good compared to the annual mean value.
Numerical Simulation of Wave Forces acting on Fixed Offshore Structures Using Hybrid Scheme
Nam, Bo-Woo ; Hong, Sa-Young ; Kim, Yong-Hwan ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 16~22
In this paper, the diffraction problems for fixed offshore structures are solved using a hybrid scheme. In this hybrid scheme, potential-based solutions and the Navier-Stokes-based finite volume method (FVM) with a volume-of-fluid (VOF) method are combined. We introduce a buffer zone for efficient wave-making and damping. In this buffer zone, the near field solution from FVM-VOF is gradually changed to Stokes' 2nd order wave solutions. Three different models, including the truncated cylinder, sphere, and wigleyIII model, are numerically investigated in regular waves with a wave steepness of 1/30. The efficiency and accuracy of the hybrid scheme are numerically validated from results using different domain sizes and buffer zones. The wave exciting forces from the FVM-VOF simulations are compared with experiments and potential-based solutions from the higher-order boundary element method (HOBEM). This comparison shows good agreement between the hybrid scheme and potential-based solutions.
Study on Tidal Current Simulation and its Application to Speed Trial around Straits of Korea
Lee, Hee-Su ; Choi, Dai-Hyun ; Park, Jong-Chun ; Jeong, Se-Min ; Kim, Young-Hun ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 23~29
Korean shipbuilding companies have sometimes carried out sea trials to measure a vessel's speed performance around the western channel of the Straits of Korea, where the flow fields are very complicated because of the effect of various flows such as sea, tidal, geostrophic, and wind-driven currents. Because these flows seem to present significant interference to a ship, the numerical reproduction of the flow-fields in the vicinity of the target sites could provide a better understanding of the sea environments while performing sea trials. In this study, we used the MEC ocean model to simulate the tidal currents around Tsushima Island and compared the simulated tidal amplitudes and currents with the measurements of Teague et al. (2001). The tidal amplitudes of the present simulation results agreed well with the observations. Based on the numerical simulation, the optimal direction and proper sites for a speed trial are described.
A Study on the Effect of Filling Ratio on Sloshing Impact Pressure
Choi, Hu-In ; Kwon, Sun-Hong ; Park, Jung-Ho ; Choi, Young-Myung ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 30~33
This study presents the effect of filling ratio on sloshing impact pressure. The experiment was done with three filling ratios of 20%, 70%, and 95% of the tank height. The input of the motion was regular excitation. The total number of sensors in use were 53. They were installed on tank top and tank wall. The maximum pressures and the average of one third highest impact pressures for the whole pressure sensors were investigated. The result shows clearly the location of sensors which are exposed to the high impact pressures for different filling ratios. The characteristics of the impact patterns for three filling ratios were also examined.
Spatial Modulation of Nonlinear Waves due to Bragg Reflection
Choi, Ka-Ram ; Koo, Weon-Cheol ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 34~40
Bragg reflection of nonlinear waves is simulated by a 2D fully nonlinear numerical wave tank (NWT). The developed NWT was based on the Boundary Element Method (BEM) with potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme with Runge-Kutta 4th-order time integration. A spatial variation of wave elevations and their Fourier amplitudes of each component are compared to investigate the effect of sea bottom ripples and their relative heights. The incident waves over an undulated sea bottom are partially reflected and changed to partial standing waves due to Bragg reflection. The present results are verified with linear calculations and experimental data. It is found that the 1st-order wave component is mainly affected by Bragg reflection and its spatial modulation is significant in front of the bottom ripples.
Study of Formation and Development of Oxygen Deficient Water Mass, Using Ecosystem Model in Jinhae, Masan Bay
Kim, Yeon-Joong ; Kim, Myoung-Kyu ; Yoon, Jung-Sung ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 41~50
This study established a 3D ecosystem model composed of stratification considering the topographic heat accumulation effect and river outflow, and then applied this model to Jinhae, Masan Bay. Specifically, it reenacted the formation and developmental process of ODW according to the stratification by calculating the kinematic eddy viscosity and eddy diffusion coefficient of the stratification model. The results were used as input data for the ecosystem model and compared with DO, COD, I-N, and I-P, which is the standard index of ocean water quality. As a result, it was determined that COD and T-N are third grade and T-P is second grade standards for a natural environment.
Effectiveness of Wave Resonator for Secondary Undulation under Real Sea Conditions
Jeong, Jin-Woo ; Kim, Do-Sam ; Park, Jong-Bae ; An, Sung-Wook ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 51~60
In this study, the performance evaluation of a conventional wave resonator at the entrance of a port or a pier against secondary undulation has been performed using 2D hydrodynamic modeling within port. A wave resonator has been designed for the attenuation of the secondary undulation induced by the long-periodic waves. The controlled performance of the wave resonator has been numerically investigated for CGWAVE MODULE of finite-element model of SMS (Surface water Modeling System) based on the elliptic mild-slope wave equation. SMS was verified though the comparisons with analytical solution performed by Ippen and Goda (1963). Also, It was confirmed that a wave resonator of a rectangular model harbor is effective enough to control the secondary undulation when it compares variation of water level with the case of no resonance system. From the above results, amplification phenomenon induced by long-period waves transferred from 1900 sec to 2100 sec when it applied a wave resonator in Busan Gamcheon Port which is a deep-sea. And it was confirmed that a wave resonator of Pohang New Port attenuates largely long-period waves which are within the range of 300 sec induced by long-period motion of the moored ship.
Free Vibration Analysis of Perforated Steel Plates with Various Cutout Curvatures and Rotations
Woo, Jin-Ho ; Na, Won-Bae ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 61~70
This study presents free vibration analyses of perforates steel plates with various cutouts. Four different parameters (shape, size, curvature radius ratio, and rotation of cutouts) were considered to investigate the effects of those parameters on the free vibration characteristics, such as natural frequencies of the perforated steel plates. Three different shapes of cutouts are circle, square, and triangle, and the considered sizes are 5, 10, 15, 20, and 25 mm. For the triangular and square cutouts, the characteristic radii of the inscribed circles of those cutouts were defined. In addition, the curvature radius ratio was defined as the ratio of curvature radius of bluntness and the characteristic radius. Then, total seven different curvature radius ratios (0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) were considered. To investigate the rotation effect of the cutouts, it was considered four rotations (
) for the square cutouts and three rotations (0, 15, and 30) for the triangular cutouts. All the free vibration analyses were conducted using a general purpose finite element program. From the analyses we found that the most influential parameter for the free vibration response of the perforated plates is the size of cutout. The other factors such as the shape, curvature radius ratio, and rotation are minors; they mainly change the natural frequency as long as the size effect is accompanied.
Study on Wear Properties of GCV Materials with DLC Coating
Lee, Soo-Chul ; Kim, Nam-Seok ; Nam, Ki-Woo ; Ahn, Seok-Hwan ; Kim, Hyun-Soo ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 71~75
Although Graphite Compacted Vermicular (GCV) was first observed in 1948, the narrow range for stable foundry production precluded the high volume application of GCV to complex components such as cylinder blocks and heads until advanced process control technologies became available. This, in turn, had to await the advent of modern measurement electronics and computer processors. Following the development of foundry techniques and manufacturing solutions, primarily initiated in Europe during the 1990s, the first series production of GCV cylinder blocks began during 1999. Today, more than 40,000 GCV cylinder blocks are produced each month for OEMs, including Audi, DAF, Ford, Hundai, MAN, Mercedes, PSA, Volkswagen, and Volvo. Given that new engine programs are typically intended to support three to four vehicle generations, the chosen engine materials must satisfy current design criteria and also provide the potential for future performance upgrades without changing the overall block architecture. With at least a 75% increase in the ultimate tensile strength, a 40% increase in the elastic modulus, and approximately double the fatigue strength of either iron or aluminum, GCV is ideally suited to meet current and future of engine design and performance requirements.
Wear Property of SACM645 Material with DLC Coating
Kim, Nam-Soek ; Nam, Ki-Woo ; Park, Jong-Nam ; Ahn, Seok-Hwan ; Kim, Hyun-Soo ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 76~80
Oil hydraulic piston pumps are being extensively used around the world, because of their simple design, light weight, effective cost, etc. An oil hydraulic pump is likely to have the serious problems of high leakage, friction, and low energy efficiency after a long period of use. In an oil hydraulic piston pump, the clearance between the valve block and piston plays an important role for volumetric and overall efficiency. In this study, the wear property of the SACM645 material with DLC coating used for a hydraulic piston pump was determined by experimentation with variable heat treatment. To investigate the effect according to the piston surface condition, five different types of specimens were prepared. The maximum tensile strengths of the QT and QT Nitration specimens had similar values of about 800 MPa, but the strains indicated a big difference. In a wear test, the wear characteristic of the DLC coating specimen was shown to be excellent. The QT, QT + IH, QT + Nitration, and matirx specimen showed similar wear characteristics. In the case of a dry condition without oil, the DLC coating specimen had good wear resistance, with no wear shown.
Effects of Softener and Hardener Co-doping on Properties of PZT Piezoelectric Ceramics
Lee, Eon-Jong ; Kim, Yun-Hae ; Lee, Byeong-Woo ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 81~85
The effects of co-doping with complex dopants of softeners,
, and a hardener,
, on the microstructural and piezoelectric properties of PZT ceramics with a composition of a rhombohedral-tetragonal morphotropic phase boundary,
, were investigated. Unlike single-element doping, the complex doping of both the softener and hardener ions led to various compensation effects for the piezoelectric properties of the PZT ceramics. For 0.5 wt.%
softener and/or 0.5 wt.%
doped compositions, there were apparent hardener doping (compensation) effects for an addition of over 1.0 wt.%
. For the
doped composition, the co-dopant
addition led to lower kp and
r, and increased
values. The prepared PZT ceramics modified with complex soft dopants,
, as well as a hard dopant,
, showed that the piezoelectric properties were stable with the compositional variations, which made it possible to establish piezoelectric performances with higher reliability and reproducibility. The most improved piezoelectric properties of enhanced
, were obtained in the PZT composition complexly doped with
. From the results obtained in this study, the properties of compositionally modified PZT ceramics can also be tailored over a wider range by changing the dopant compositions to meet the specific requirements for underwater or other applications.
Synthesis and Characterization of Bi
Powders by Ultrasonic Spray Pyrolysis Method
Bae, Bung-Su ; Jung, Sang-Jin ; Lee, Bong ; Moon, Chang-Kwun ; Choi, Hee-Lack ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 86~91
(Bi-2223) powders were synthesized by ultrasonic spray pyrolysis method. It is clear that Bi-2223 phase more than Bi-2212 phase was acquired at sufficient synthesized time. Best condition for Bi-2223 phase was synthesizing temperature at
. We also investigated the effects for concentrations and viscosities of starting liquid precursor as well as temperature distribution of reacting furnace. The size of synthesized powder was decreased by decreasing the concentration of starting liquid precursor. Modified reacting furnace with four different temperature heating zones gave us successful results for desirable nano-powder including
phase. Citric acid addition to starting liquid precursor showed increasing of the size for synthesized powder. Bi-2223 single phase was acquired from Bi2223 and Bi-2212 mixed phases through heat treatment in box furnace at 24 hours.
Study on Weldability of A5052-H32 Sheet using Nd : YAG Laser-MIG Hybrid Welding
Kim, Jun-Hyung ; Bang, Han-Sur ; Bijoy, M.S. ; Jeon, Geun-Hong ; You, Jea-Sun ; Bang, Hee-Seon ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 92~96
Recently, the application of aluminum alloys has been increasing for lightweight and high quality transport vehicles. Therefore, the proposal has been made to apply high speed hybrid welding methods to the marine grade aluminum alloy (A5052) used for shipbuilding by combining a 3-KW CW Nd : YAG laser and the MIG welding process. In this study, the characteristics of the welding parameters were investigated for a hybrid butt joint. This paper also describes the determination of the heat distribution in a weldment and the welding residual stress using a finite element method. Mechanical experimentation was also used to ascertain the reliability of the weldment.
Variability of Short Term Creep Rupture Time and Life Prediction in Stainless Steels
Jung, Won-Taek ; Kong, Yu-Sik ; Kim, Seon-Jin ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 97~102
This paper deals with the variability of short term creep rupture time based on previous creep rupture tests and the statistical methodology of the creep life prediction. The results of creep tests performed using constant uniaxial stresses at 600, 650, and
elevated temperatures were used for a statistical analysis of the inter-specimen variability of the short term creep rupture time. Even under carefully controlled identical testing conditions, the observed short-term creep rupture time showed obvious inter-specimen variability. The statistical aspect of the short term creep rupture time was analyzed using a Weibull statistical analysis. The effect of creep stress on the variability of the creep rupture time was decreased with an increase in the stress level. The effect of the temperature on the variability also decreased with increasing temperature. A long term creep life prediction method that considers this statistical variability is presented. The presented method is in good agreement with the Lason-Miller Parameter (LMP) life prediction method.
The Functional Safety Assessment of WIG Craft in Design Stage
Lee, Soon-Sup ; Park, Beom-Jin ; Lee, Jong-Kap ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 103~108
WIG crafts are high speed vessels with the features of a dynamic supported craft. These crafts, which are predominantly lightweight and operate at substantially greater speeds than conventional craft, could not be accommodated under traditional maritime safety instruments. WIG crafts inherently possess more hazard factors than conventional ships because of their relatively high speed, lightweight, and navigational characteristics, and an accident is likely to cause damage to the ship and a high loss of life. Because WIG crafts are composed of many systems and subsystems, the safety assessment of a WIG must use a commercial software system in the design stage. This paper reviews a safety assessment process and methodology proposed by the IMO interim guideline, which were developed in view of the configuration of WIG crafts. This safety assessment system was developed to fit the WIG's safety assessment process using a reliability analysis system widely used in commercial systems. The FHA was performed on the functional hazards of systems in the conceptual design stage.
Optimization of Frame Structures with Natural Frequency Constraints
Kim, Bong-Ik ; Lee, Seong-Dae ;
Journal of Ocean Engineering and Technology, volume 24, issue 6, 2010, Pages 109~113
We present the minimum weight optimum design of cross sectional for frame structures subject to natural frequency. The optimum design in this paper employ discrete and continuous design variables and Genetic Algorithms. In this paper, Genetic Algorithms is used in optimization process, and be used the method of Elitism and penalty parameters in order to improved fitness in the reproduction process. For 1-Bay 2-Story frame structure, in examples, continuous and discrete design variables are used, and W-section (No.1~No.64), from AISC, discrete data are used in discrete optimization. In this case, Exhaustive search are used for finding global optimum. Continuous variables are used for 1-Bay 7-Story frame structure. Two typical frame structure optimization examples are employed to demonstrate the availability of Genetic Algorithms for solving minimum weight optimum of frame structures with fundamental and multi frequency.