• 한국해양학회지
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• v.17 no.1
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• pp.12-18
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• 1982

Tidal exchanges of sea water are studied by using drogue experiments and tidal current measurement data in Gamag Bay which has two channels. At the spring tide, the volume of tidal transport in the bay was estimated to be 46∼52% of the total volume of sea water in Gamag Bay, 7.1 10$\^$8/㎥. The tidal transport through the wide channel occupies 87% of the total tide transport of the bay. Residual current was deduced to flow north-northeastward at the rate of 3.254 10$\^$5/㎥ per tidal cycle. the tidal exchange of the sea water during the flood flow was estimated to be approximately 26% of the tidal transport, while that during the ebb flow was 41%. The tidal exchange through the wide channel during the flood flow occupies 77% of total tidal exchange of the bay through both channels, whereas that during the ebb flow does 88%. The diffusion coefficient of 2.08∼ 2.30 10$\^$7/$\textrm{cm}^2$/sec at the narrow channel was greater than that at the wide channel which was 1.2∼2.8 10$\^$6/$\textrm{cm}^2$/sec.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.35-42
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• 2001

The characteristics of tidal circulation with the flow-control structures using the three-dimensional numerical model (POM, Princeton Ocean Model) of Chinhae Bay, Korea were investigated. To confirm th efficiencies of flow-control structures, the training wall and submerged training wall were constructed at the mouth and narrow channel in Chinhae Bay. On the basis of the present investigation, the tidal circulation induced by the construction of flow-control structures could enhance the water exchange improvement appropriately. And, th training wall at the central is more dominated than the other structures for the efficient of water exchange. The sites and types of structure and flow patterns seem to be very sensitive in tidal simulation and changes in flow fields.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.435-446
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• 2014

Tidal turbulence was examined using three-dimensional tidal velocity data observed at a trench offshore of Tongyoung, Korea. The kinetic energy and intensity, including the variation period of the flow velocity and direction, were used to investigate the relationships between tidal turbulence and fishing gear dynamics, including the effects of swimming fish during fishing operations. As the resultant velocity increased from 0.2 to 0.9 m/s, the kinetic energy also significantly increased, while the turbulence intensity decreased from 50 to 10%. Tidal flow in strong flow fields displayed shorter periods of between 4 and 10 s, as determined by fast Fourier transform, the global wavelet method, and peak event analysis, and the periods were compared with the period of response to swimming fish and to oscillation of fishing gear. As mean velocity increased, velocity amplitude also increased from 0.1 to 0.6 m/s, and its directional amplitude changed markedly from 20 and $90^{\circ}$. Our study suggests that tidal turbulence can influence fish behavior or fishing gear geometry during fishing operations, although our analysis considered only a limited area. In future work, observations should be carried out over a more extensive depth and area.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.159-174
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• 2022

Flow prediction was carried out through observational survey and three dimensional multi-layered numerical diagnostic model experiment to clarify the time and spatial structure of tidal current and residual flow dominant in the sea exchange and material circulation of the waters around Geumo Islands in the southern waters of Korea. The horizontal variation of tidal current is so large that it causes asymmetric tidal mixing due to horizontal eddies and the topographical effect creating convergence and dispersion of flow direction and velocity. Due to strong tidal currents flowing northwest-southeast, counterclockwise and clockwise eddies are formed on the left and right sides of the south of Sori Island. These topographical eddies are created by horizontal turbulence and bottom friction causing nonlinear effects. Baroclinic density flows are less than 5 cm/s at coastal area in summer and the entire sea area in winter. The wind driven currents assuming summer and winter seasonal winds are also less than 5 cm/s and the current flow rate is high in winter. Density current in summer and wind driven current in winter have a relatively greater effect on the net residual flows (tidal residual current + density current + density driven current) around Geumo Islands Sea area.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.4
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• pp.73-83
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• 1991

A numerical simulation of a 2-dimensional tidal flow in a shallow sea was performed using the frequency domain finite element method. In this study, to overcome the inherent problems of a time domain model which requires high eddy viscosity and small time steps to insure numerical stability, the harmonic function incorporated with the linearized function of governing equations was applied. Calculations were carried out using the developed tidal model(TIDE) in a rectangular channel of lOm(depth) X 4km (width) X 25km(length) under the condition of tidal waves entering the channel closed at one end for both with and without bottom friction damping. The predicted velocities and water levels at different points of the channel were in close agreement with less than 1 % error between the numerical and analytical solutions. The results showed that the characteristics of the tidal flow were greatly affected by the magnitude of tidal elevation forcing, and not by on surface friction, wind, or the linear bottom friction when the value was less than 0.01. For the optimum size of grid to obtain a consistent solution, the ratio between the length of the maximum grid and the tidal wave length should be less than 0.0018. It was concluded that the finite element tidal model(TIDE) developed in this study could handle the numerical simulation of tidal flows for more complex geometrical conditions.

• Journal of Environmental Impact Assessment
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• v.5 no.1
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• pp.31-45
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• 1996

This paper presents the results from a hydrodynamic model study to predict the impacts of coastal reclamation in Pusan harbor system using RMA2 which is a tidal flow model of the US Army Corps of Engineers' TABS-2 system. A finite element mesh was constructed and refined to cover the complicated geometry of Pusan harbor system and the proposed reclamation area. The model was calibrated to tidal elevations and currents measured during spring fall syzygys. Under the three different tidal conditions including summer winter syzygys, spring fall quarters, and summer winter quarters, the model predictions were compared with the field measurements both in tidal elevation and current. In all cases, there were excellent agreements between the model predictions and the field measurements. The validated model was then used to predict the changes in tidal current and elevation that might occur due to the coastal reclamation. It was predicted that there would be no change in tidal elevation of this system after the reclamation. In tidal current, however, discernible changes were predicted near the proposed reclamation area both in magnitude and direction.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.173-173
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• 2015

The flood water level in tidal river is determined by the joint effects of flood discharge and tidal water levels at downstream boundary. Due to the variable tidal boundary conditions, the evaluated design water levels associated with a certain flood event can be significantly different. To avoid determining of design water levels just by a certain tidal boundary condition and remove the influence of variability in boundary condition from the evaluation of design water levels, a probabilistic approach is considered in this study. This study focuses on the development of a method to evaluate the realistic design water levels in tidal river with taking into account the combined effects of river discharge and tidal level. The flood water levels are described by the joint probability of two driving forces, river discharge and tidal water levels. The developed method is applied to determine design water levels for the tidal reach of the Han River. An unsteady flow model is used to simulate the flow in the reach. To determine design water levels associated with a certain flood event, first, possible boundary conditions are obtained by sampling starting times of tidal level time series; then for each tidal boundary condition, corresponding peak water levels along the channel are computed; and finally, design water levels are determined by computing the expectations of the peak water levels. Two types of tides which are composed by different constituents are assumed (one is composed by $M_2$, and the other one is composed by $M_2$ and $M_2$) at downstream boundary, and two flood events with different maximum flood discharges are considered in this study. It is found that (a) the computed design water levels with two assumed tides have no significant difference for a certain flood event, though variability of peak water levels due to the tidal effect is considerably different; (b) tidal effect can reach to the Jamsil submerged weir and the effect is obvious in the downstream reach of the Singok submerged weir; (c) in the tidally affected reach, the variability of peak water levels due to the tidal effect is greater if the maximum flood discharge is smaller.

• Ocean Science Journal
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• v.43 no.2
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• pp.81-90
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• 2008

A study of estuarine flows during a neap tide was performed using 13-hour roving acoustic Doppler current profiles (ADCP) and conductivity-temperature-depth (CTD) profiles in the Altamaha River estuary, Georgia, U.S.A. The least-squared harmonic analysis method was used to fit the tidal ($M_2$) component and separate the flow into two components: the tidal and residual ($M_2$-removed) flows. We applied this method to depth-averaged data. Results show that the $M_2$ component demonstrates over 95% of the variability of observation data. As the flow was dominated by the $M_2$ tidal component in a narrow channel, the tidal ellipse distribution was essentially a back-and-forth motion. The amplitude of $M_2$ velocity component increased slightly from the river mouth (0.45 m/sec) to land (0.6 m/sec) and the phase showed fairly constant values in the center of the channel and rapidly decreasing values near the northern and southern shoaling areas. The residual flow and transport calculated from depth-averaged flow shows temporal variability over the tidal time scale. Strong landward flows appeared during slack waters which may be attributed to increased baroclinic forcing when turbulent mixing decreases.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.353-360
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• 2010

The Kyunggi Bay in mid-west of Korea is a relatively large estuarine system that connects the Han River system with Yellow Sea. Due to macro-tidal range of more than 8 m, the urban estuary shows deep tidal channels and wide tidal flats. Since last 30 years, the coastal development is undergoing, yielding noticeable change in environment. Particularly the tidal flat dynamics are generally accepted as being related with tidal residual flows in this area (Kim et al., 2009). We have estimated the annual variation and vertical structure of residual currents with one-year long observed flows in two major tidal channels of Kyunggi Bay. The moving average method and tidal current harmonic analysis yield nearly the same results on residual flow. The residual flow in Jangbong channel ranges from 20 cm/s in summer to 30 cm/s in winter. It is noticeable that the residual flow in Jangbong channel is flood dominant throughout the year, while the flow in Seokmo channel is ebb-dominant residual flow with current speed range of 20-40 cm/s. Due to the baroclinic response of relatively shallow estuary, significant reduction of energy in bottom layers have been observed, indicating the importance of residual circulation to the tidal flat behavior.