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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Society of Coastal and Ocean Engineers
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Korean Society of Coastal and Ocean Engineers
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Volume & Issues
Volume 23, Issue 6 - Dec 2011
Volume 23, Issue 5 - Oct 2011
Volume 23, Issue 4 - Aug 2011
Volume 23, Issue 3 - Jun 2011
Volume 23, Issue 2 - Apr 2011
Volume 23, Issue 1 - Feb 2011
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Wave Impact Pressures Acting on the Underwater Tunnel Bulkhead under Construction - Numerical Analysis and Hydraulic Model Experiment -
Kim, Sun-Sin ; An, Dong-Hyuk ; Chun, In-Sik ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 139~146
DOI : 10.9765/KSCOE.2011.23.2.139
The breaking wave pressure occurs when a plunging breaker instantaneously impinges on structural surface, and appears differently depending on whether or not to form air pockets at the instant of contact. The Wagner type normally forms a single pressure peak at the contact spot due to the direct collision of water volume to the structure whereas in the Bagnold type the time lagged oscillation of the air pocket causes pressure peaks even at areas away from the spot. In the present study, the Bagnold's impact pressure is numerically and experimentally investigated for the bulkhead of an underwater tunnel under construction which is subjected to nearby breaking waves. A numerical solver of Navier-Stokes equations was applied to reproduce the breaking waves near a bulkhead, and the results showed the Bagnold's impact pressure occurring on the back (land side) face of the bulkhead. The existence of the impact pressure was also verified by a hydraulic model testing, and it was found that the experimental results well conformed to their numerical counterparts.
An Experimental Study on the Effect of Erosion Control by Multi-Cylinder Piles
Lee, Sang-Hwa ; Jang, Eun-Cheul ; Lee, Han-Seung ; Jeong, Seok-Jae ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 147~153
DOI : 10.9765/KSCOE.2011.23.2.147
Environmental and safety problems are one of the most important factors in designing coastal wave control structures and maintaining facilities in coastal zone. This study suggests the multi-cylinder piles as a profitable structure for preserving coastal zone as well as controlling the wave effectively. The hydraulic model experiment was performed to investigate the effect of erosion control of the structure. The experimental study was carried out to research the effect of erosion control in the coastal zone for existing a concrete wave breaker and the structure with multi-cylinder piles placing at the same location. As a result multi-cylinder piles reduced erosion at each sides of structure and occured sedimetation at front of structure.
Reliability Analysis of Maximum Overtopping Volume for Evaluating Freeboard of Vertical Breakwaters
Lee, Cheol-Eung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 154~162
DOI : 10.9765/KSCOE.2011.23.2.154
A reliability analysis model is developed for evaluating the crest freeboard of vertical breakwaters based on the concepts of maximum overtopping volume of individual wave. A reliability function is formulated by defining the margin of admissible overtopping volume and maximum overtopping volume that is depend on the number of overtopping waves, dimensionless crest freeboard, and mean overtopping discharge. In addition, Level III MCS technique is straightforwardly suggested by which the related empirical parameters to reliability function can be considered to be random variables with the wide range of different uncertainties. It can be possible to calculate the probabilities of failure according to the relative crest freeboard with the variations of the incident wave directions, the structural types of vertical breakwaters, and admissible overtopping volumes in conditions of the long and short crested-waves.
Optimal Layout Design of Offshore Wind Turbines by Response Surface Analysis
Kim, Ji-Young ; Kim, Kyoung-Yul ; Lee, Jun-Shin ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 163~170
DOI : 10.9765/KSCOE.2011.23.2.163
An optimal layout condition of the offshore wind turbines is studied by using the response surface analysis which is a kind of the design of experiments. Based on the assumption that total 36 turbines would be installed in the offshore wind farm, the number and distance of the rows and columns are used as the design variables and the efficiency decrease of power generation due to the wake decay by the interactions of turbines and the installation cost of the internal electric grid are considered as the objective functions of the response surface analysis for the layout design of turbines. Useful design information can be derived by analyzing the relationship between the design variables and target functions. It is found that the row number and the distance between rows should be minimized, and the optimal distance between columns should be estimated and adopted to the layout design within the specified design range in order to ensure the economics for the offshore wind farm.
Numerical Analysis of Pressurized Air Flow and Acting Wave Pressure in the Wave Power Generation System Using the Low-Reflection Structure with Wall-Typed Curtain
Lee, Kwang-Ho ; Choi, Hyun-Seok ; Kim, Chang-Hoon ; Kim, Do-Sam ; Cho, Sung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 171~181
DOI : 10.9765/KSCOE.2011.23.2.171
Recently, many studies have been attempted to save the cost of production and to build the ocean energy power generating system. The low-reflection structure with the wall-typed curtain which has a wave power generation system of OWC is known as the most effective energy conversion system. A three-dimensional numerical model was used to understand the characteristics of velocity of flows about compressed air and to estimate the pressure acting on the low-reflection structure due to the short-period waves. The three-dimensional numerical wave flume which is the model for the immiscible two-phase flow was applied in interpretation for this. The numerical simulation showed well about the changes in velocity of compressed air and the characteristics of pressure according to the change in the wave height and depth of the curtain wall. Additionally, the results found that there was the point of the maximum velocity of the compressed air when the reflection coefficient is at its lowest point.
Application of Dynamically Coupled POM-WAM to Undertow Simulation
Chun, Je-Ho ; Ahn, Kyung-Mo ; Suh, Kyung-Duck ; Yoon, Jong-Tae ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 23, issue 2, 2011, Pages 182~191
DOI : 10.9765/KSCOE.2011.23.2.182
In the present study, the dynamically coupled POM-WAM of Chun et al.(2009) was applied to the numerical simulation of undertow, one of the nearshore currents. To improve the accuracy of the numerical model results in surf zone, the transport equation of the surface roller was solved, and its effects were incorporated into the present numerical model. The numerical model has been applied to two hydraulic experiments of Okayasu and Katayama(1992) and Cox and Kobayashi(1997). The numerical results were compared with the hydraulic experimental results to give a good concurrence. It is concluded that the present numerical model can be applied to the shallow water region including surf zone.