• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.72-80
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• 1991

This study presents the behavior of unsteady saline wedge in which it is examined velocity profile variations at the lower layer (inner wedge) and wedge tip responses to a tidal action in a rectangular open channel. Unsteady saline wedge has just tidal excursions corresponding to tidal amplitudes at the river mouth, although two wedge tips in flood and ebb tide remarkably have different shapes. Maximum velocities at the lower layer appear immediately from high water to low water level (or low to high water). Numerical computation results obtained by only just interfacial friction factor at the steady state show satisfactory agreements with experimental data. However, the numerical model on one-demensional two-layer flor still has some problems to date.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.4
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• pp.231-244
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• 1990

The objectives of this multiyear research are directed toward the investigation of mesoscale circulation dynamics in the Yellow Sea and the East China Sea. With the advent of Supercomputers and increasing necessity of resolving the flow with enough details, a hydrodynamic numerical model of the East China Sea has been developed with resolution of 1/15$^{\circ}$latitude by 1/12$^{\circ}$longitude covering the entire continental shelf. As a first step M$_2$tidal regime representing the domanant tidal conditions of the shelf was computed. Preliminary results are presented and discussions for further developments are presented.

• 한국해양학회지
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• v.28 no.2
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• pp.121-131
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• 1993

The tidal front forming in the Mid-Yellow Sea off Korea, near Tae-An peninsular, is calculated using a 3-D general circulation model(Semtner, 1974) and the concept of mixing rate, an extension of the concept of mixing efficiency proposed by simpson & Hunter(1974). Along the north and south open boundaries, simple radiation conditions are applied. The model is run with the initial state which represents the winter condition. With imposed uniform heating by solar radiation and spatially-different vertical mixing, the model then generated the tidal front comparable to the observed one.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.397-403
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• 1994

Circulations in Deukryang Bay are investigated using a numerical shallow water model. In the flow fields observed at four stations, north-south velocity components are dominant. In the model, the circulation forced by $M_2$-tide basically corresponded well to the observations. The model shows the strong currents in the mouth and the eastern part in the bay with about 60 cm/s and 50 cm/s, respectively. The model also shows the eddies in the tidal residual currents. To investigate the mechanism of eddy formation some numerical experiments are carried out. The results show that inertial and topographic effects play an important role in the eddy formation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.13-26
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• 2016

Sea water level variations are generally influenced by a variety of factors such as tides, meteorological forces, water temperature, salinity, wave, and topography, etc. Among non-tidal conditions, atmospheric pressure is one of the major factors causing water level changes. In the East Sea, due to small tidal range which is opposite to large tidal range of the Yellow Sea, it is difficult to predict water level changes using a numerical model, which consider tidal forcing only. This study focuses on the effects of atmospheric pressure variations on sea level predictions along the eastern coast of Korea. Telemac-2D model is simulated with the Inverted Barometer Effect(IBE), and then its results are analyzed. In comparison between observed data and predictions, the correlation of prediction with IBE and tide is better than that of tide-only case. Therefore, IBE is strongly suggested to be considered for the numerical simulations of sea level changes in the East Sea.

• Journal of Korean Port Research
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• v.12 no.1
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• pp.95-104
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• 1998

Water pollution in a semi-enclosed sea area such as a bay due to stagnancy of water has been a serious water environmental problem. Recently, some kinds of new methods to activate the tidal exchange between an inner bay and an outer sea area by control of a tidal residual current have been proposed. However, these methods have several problems, that is, I). deterioration in a natural view due to building of huge structures, II). increase of risk of navigation in case of a submerged structure, III). limition of sea area where a tidal current can be controlled and IV). difficulty in removing those structures in case of occurrence of an unexpected impact on water environment. In this paper, a new method is proposed, which can solve all the above problems, to purify water quality in a semi-enclosed bay by creation and control of a pattern of a tidal residual current. The tidal residual current is controlled by unsymmetric structures, which change the properties of resistance according to the direction of flow, arranged on the sea bottom. In this study, several numerical and hydraulic experiments of tidal current and particle-tracking for various arrangements of bottom roughness in a semi-enclosed model bay were carried out. As a result of experiments, it becomes clear that it is possible to generate a new tidal residual current and to activate a tidal exchange by only operation of bottom roughness arrangement.

• Ocean Systems Engineering
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• v.6 no.1
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• pp.23-60
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• 2016

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model - combining the flow module of Delft3D with the WAVE solver of XBeach - of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.6
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• pp.1842-1853
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• 2015

The behavior characteristics of the saltwater intrusion in the Seomjin River Estuary by the inflow of fresh water were analysed by the field observation using CTD in the neap tide in January, June, and August 2013 as well as a numerical model, EFDC (Environmental Fluid Dynamics Code). As a result, Seomjin River Estuary is found that the saltwater intrusion is sensitive to the tide and tidal and freshwater flow. The results of field observation and numerical model were similar in the range of salt, but the results of salt wedge distribution were quite different. The observation of tide and tidal current as well as hydrographic surveying the Seomjin River Estuary will be jointly conducted for the accurate analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.13-23
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• 1984

The purpose of this paper is to develop a numerical model which can be used to compute the suspended load concentration of which the two-dimensional unsteady diffusion equation is able to be solved by the finite difference method using the implicit scheme. The pick-up rate formula from the bottom used in the open channel as a sink source term and the Coleman's empirical formula for the diffusion coefficient were taken, and especially the hindered settling velocity and the vertical velocity of flow due to the periodical tidal motion were taken into account, while the effects of the variables, such as the horizontal and vertical velocities of flow, tidal range, the settling velocity and hindered settling, on the suspened load concentrations have been discussed, comparing the results obtained from the different cases in the simulation conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.4
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• pp.243-258
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• 2005

A fully-nonlinear two-dimensional dynamically interfaced nested tidal model has been developed with improved efficiency, usability, relocatability and also adopting different time steps for economizing computational times, which is based on two-dimensional tidal model of Choi(1990) with resolution of $1/15^{\circ}$ inlatitude by $1/12^{\circ}$ in longitude covering the whole Yellow and East China Seas continental shelf. To illustrate the validity and applicability of the present model, numerical model experiment was carried out for tidal distribution in the Yellow Sea and the East China Sea emphasizing the Saemangeum area with enhanced grid system. The results from comparison with observed value showed that the present model gives reasonable agreement. The present modeling system is a relocatable tide forecasting system designed to predict tides at any location within the Yellow Sea and the East China Sea continental shelf sea.