• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.115-120
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• 2011

The dynamic responses of a 5 MW wind turbine lifted by a floating crane with two elastic booms are analyzed. Dynamic equations of motions of a multibody system that consists of a floating crane, two elastic booms, and a wind turbine are derived. The six-degree-of-freedom (DOF) motions for the floating crane and the wind turbine are considered in the equations of motions. The hydrostatic force, the hydrodynamic force due to a regular wave, the mooring force, the wire rope force, and the gravitational force are considered as external forces. By solving the equations numerically, the dynamic responses of cargo are simulated. The simulation results are compared with those in the case of one elastic boom. Finally, the dynamic responses of the wind turbine lifted by the floating crane are analyzed under regular wave condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.2
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• pp.83-91
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• 2004

The performance of wave control by a surface-mounted horizontal membrane is analyzed in the frame of linear potential theory. To employ the eigenfunction expansion method, the fluid domain is divided into two regions i.e. region without membrane and membrane-covered region. By matching the each solutions at boundaries of adjacent regions, the complete solution is obtained. The present analytical method solving the scattering problem directly gives the same results as Cho and Kim(1998)'s method solving the diffraction and the radiation problem separately. To verify the developed model, the model test with a surface-mounted horizontal membrane is conducted at the wave tank(36m${\times}$0.91m${\times}$l.22m). The analytic results are in good agreement with the experimental results. The reflection and transmission coefficients are investigated according to the change of membrane tension, length and incident frequencies.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.111-117
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• 2012

Oscillating water column is the most widely used ocean energy converting systems all over the world. The operating performance is influenced by the efficiencies of the two converting stages in the OWC chamber-turbine integrated system. In order to consider the effects of the turbine, the orifice model are carried out. The VOF based Numerical Wave Tank (NWT) is utilized to simulate the water column oscillation inside the chamber and the results are compared with corresponding experimental data. This paper reviews the state of the art in interaction among wave elevation inside the chamber and air flow rate in the duct, which are considered the turbine effects. Effects of incident wave conditions and several shape parameters on the operating performance of OWC chamber are investigated numerically. The effects of the impulse turbine on the integrated system and interaction among the wave elevation, pressure and air flow velocities variations are investigated.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.90-97
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• 2013

Oil booms are one of the most widely used types of equipment for the protection of coastal areas against oil spills. In some situations, however, there are several types of oil leaks from the oil boom. Important factors regarding these phenomena include the surrounding ocean environment, such as waves, the density and viscosity of oil, the length of the oil boom skirt, etc. To estimate the performance of the oil boom, it is necessary to predict the behavior of the spilled oil and oil boom. In the present study, the prediction of oil boom performance in waves was carried out using the Pusan-National-University-modified Moving Particle Semi-implicit (PNU-MPS) method, which is an improved version of the original MPS proposed by Koshizuka and Oka (1996). The governing equations, which consist of continuity and Navier-Stokes equations, are solved by Lagrangian moving particles, and all terms expressed by differential operators in the governing equations are replaced by the particle interaction models based on a kernel function. The simulation results were validated through a comparison with the results of Violeau et al. (2007)..

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.295-303
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• 2015

The eigenfunction expansion method is appled for the wave scattering by a vertical slotted, where both the inertial and quadratic drag terms are involved. Quadratic drag term representing the energy loss is linearized by the application of socalled equivalent linearization. The drag coefficient, which was empirically determined by Yoon et al.(2006) and Huang(2007) is used. Analytical results are verified by comparison to the experimental results conducted by Kwon et al.(2014) and Zhu and Chwang(2001). Using the developed design tool, the effect of energy loss by a vertical slotted wall is estimated with various design parameters, such as porosity, submergence depth, shape of slits and wave characteristics. It is found that the maximum value of energy loss across the slotted wall is generated at porosity value less than P = 0.1. The present solutions can provide a good predictive tools to estimate the wave absorbing efficiency by a slotted-wall breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.217-227
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• 2012

On 31 March 2007, the abnormal wave occurred along western coast of Korean including Yeonggwang. In this paper, this event is studied using available field measurement data for the event analysis and numerical model for reproducing the unknown waves. We found several 1-min interval tidal elevation and mean sea level pressure (MSLP) data along the western coast of Korea and analyzed it using wavelet technique. We computed the arrival time and the propagation direction of abnormal wave using wavelet results and performed the numerical simulation using 2 dimensional shallow water wave model. The sea level under the forcing of air pressure jump was obviously amplified by the Proudman resonant effect. The computed sea levels compared with observations are underestimated, but the order of arrival time at the tidal station showed good agreement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.547-556
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• 2007

The sediment transport by waves, wave-induced current and tidal current was calculated using the TRANSPOR2004, then the seasonal sediment budget was analyzed. Also, annual sediment budget was calculated, and sediment circulation patterns was deduced in the broad area including Haeundae beach. A sediment mainly inflows from the east coast of the beach and then moves to the eastward to the Dongback Is, where the 80% of inflow sediment transported to the eastward as a longshore sediment while 20% of them going out to the offshore at the center of the beach. Above results shows a good agreement with the sediment transport trend analysis results by the Gao model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.3
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• pp.114-122
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• 2018

This paper introduces a non-hydrostatic wave model SWASH for simulating wave interactions with porous structures. This model calculates the flow in porous media based on volume-averaged Reynolds-averaged Navier-Stokes equations (VARANS) in ${\sigma}$-coordinate. The empirical coefficients of resistance used to account for the flow in a porous media often need to be measured or calibrated. In this study, the empirical resistance coefficients used in the model are calibrated and validated using laboratory experiments, involving dam-break flow through porous media, and solitary wave interactions with a porous structure. It is shown that the agreement between experimental and numerical results is generally satisfactory. It is also confirmed that non-hydrodynamic model, SWASH, is computationally much more efficient than the three-dimensional porous flow models based on VOF approach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.115-123
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• 2008

In the present study, a three dimensional hydrodynamic characteristics around the fully submerged dual breakwaters with a sand beach has been investigated numerically using a 3-D numerical scheme, which can determine the eddy viscosity with LES turbulence model and is able to consider wave-structure-seabed interaction in 3-dimensional wave field (LES-WASS-3D), recently developed by Hur and Lee (2007). Based on the numerical experiments, strong vortices can be generated fore and aft edges of the structures, and propagate lee sides. Thus relatively large circulation flows are occurred around submerged breakwaters. The 3-D flow hydrodynamic characteristics have been examined by mean flows and mean vortices for various x-y, x-z sections and y-z layers. Wave height distribution and wave set-up around and over submerged breakwaters, and breaking point migration toward shore side is discussed in detail.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.463-472
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• 2009

The aim of this study is to examine the effect of beach curvature on wave fields in coastal area with Submerged Breakwaters using the 3D numerical model that is able to simulate directly interaction of WAve Structure Sandy beach (LES-WASS-3D). At first, the adopted model was validated through the comparison with an existing experimental data and showed fairly nice agreement. And then, the numerical simulations have been performed to investigate the effect of according to the variation of beach curvature. Based on the numerical results, the wave height, mean surface elevation, mean flow around submerged breakwaters and longshore distributions of run-up height have been discussed in relation to the variation of beach curvature.