• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.457-466
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• 2007

The effect of depth correction in the coastal sea has been investigated through a series of tide simulations in the area of $115{\sim}150^{\circ}E,\;20{\sim}52^{\circ}N$ of northwestern Pacific with $1/12^{\circ}$ resolution. Comparison of the solutions varying the minimum depth from 10m to 35 m with the 5m interval shows that the amplitude accuracies of $M_2,\;S_2,\;K_1$ tide using the minimum depth of 25 m have been improved up to 42%, 32%, 26%, respectively, comparing to those using the minimum depth of 10m. The discrepancy between model results using different minimum depth is found to be up to 20 cm for $M_2$ tidal amplitude around Cheju Islands and the positions of amphidromes are dramatically changed in the Bohai Sea. The calculated ARE(Averaged Relative Error) values have been minimized when the bottom frictional coefficient and the minimum depth is 0.0015 and 25 m, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.4
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• pp.217-224
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• 1979

The main purpose of the present study is to measure the sound spectra of the underwater noises generated by moving trawl net. An underwater recording system was designed to detect underwater noise generated by moving trawl net. The acoustic analysis was made by a heterodyne analyzer (B & K 2010) and level recorder (B & K 2307). The noises generated by the trawl net are appreciably higher (about 10dB) than the background noise in the presence of the fishing vessel. The frequency distribution of underwater noise was DC-6,300 Hz and predominant frequency range was 100-200 Hz, and maximum sound pressure level was $137\;db(re\;1{\mu}Pa)$. Sound pressure level recorded at the ground rope was higher than that recorded at the head rope. The sound pressure level meosured in the course of hawling was higher than that measured in the course of towing. When tile net is being casted tile sound pressure level showed the lowest value.

• Water for future
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• v.21 no.1
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• pp.87-94
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• 1988

Tidal asymmetry in the Keum River Estuary has been investigated from the observed tides. Despite strong frictional attenuation within the estuary, the $M_4$ tides reach significant amplitude, resulting in strong tidal distortion. The observed asymmetry over the area shows that generally more intense flood flows transport more sediment that do less intense ebb flows of longer duration. This causes filling of the estaury as evidenced by sand flats spreaded over the inner area. The spatial distribution of peak bottom stress associated with the dominant $M_2$ and $M_4$ tides calculated via two-dimensional numerical tidal model suggest that present tidal sedimentation regimemay be altered, sepecially in the approach channel to outer Kunsan Port and downstream part of the dike, due to the construction of barrier.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.89-89
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• 2015

항만 및 어항 구조물을 구성하는 다양한 해안구조물은 파랑의 천수효과, 굴절, 회절, 부분반사, 해저마찰, 쇄파의 영향 등을 고려해야하며 파고 및 파향 등의 해양특성의 검토가 반드시 이루어져야 한다. 실제의 해양파가 방향스펙트럼을 갖는 다방향 불규칙파라는 것은 잘 알려져 있으며, 기존의 해안구조물의 내파설계 또는 천해역의 파랑변형 검토에 있어서도 실제 해양파에 보다 가까운 다방향 불규칙파를 이용한 수리모형실험에 의해 파랑현상을 정도 높게 재현하는 것은 매우 중요하다. 본 연구에서는 실제 해양파를 정도 높게 재현할 수 있는 다방향 불규칙파 조파장치를 사용하여 구조물 전면해역에서의 파랑스펙트럼을 재현하고, 심해에서 발달된 파랑이 천해로 진행될 때 지형에 의해 발생되는 천수변형과 구조물 주위에서 나타나는 파랑변형의 현상을 고려하여 항내로 유입되는 파랑의 분포 특성을 검토하였다. 특히, 다방향 불규칙파로 인한 항내 파고분포 특성을 검토하기 위하여 동일 파랑에 대한 규칙파 및 불규칙파랑을 조파하여 그 결과를 상호 비교하였다. 아울러, 정온수역유지를 위한 월파현상을 수리적으로 재현할 수 있는 3차원 수리모형실험 수행하여 월파현상이 항내정온도에 미치는 영향을 고찰, 해석하여 항만 시설물 계획시 안정한 정박 및 이용에 대한 가능한 정온유지여부를 검토하였다.

• Journal of Korean Port Research
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• v.15 no.1
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• pp.57-74
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• 2001

In the past, the predictions of beach processes and harbor sedimentation were mainly relied on the hydraulic model tests and empirical methods. In recent years, however, as computers have come into wide use, more accurate models have gradually been developed and thus replaced those conventional methods. For prediction of topographical change near the coastal area, we need informations of wave and current conditions in the numerical model which should be calculated in advance. Numerical model introduced in this study combines wave refraction-diffraction, breaking, bottom friction, lateral mixing, and critical shear stress and three sub-models for simulating waves, currents, and bottom change were briefly discussed. Simulations of beach processes and harbor sedimentation were also described at the coast neighboring Bangpo Harbor, Anmyundo, Chungnam, where the area has suffered accumulation of drifting sand in a small fishing harbor with a wide tidal range. We also made model test for the new layout of the harbor and planned south breakwater for preventing intrusion of sand. Although the model study gave reasonable description of beach processes and harbor sedimentation mechanism, it is necessary to collect lots of field observation data, including waves, tides and bottom materials, etc. for better prediction.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.49-54
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• 1990

This study describes the application of a two dimensional depth integrated numerical model. The explict scheme of finite difference method had been applied to the model of circulation. The nonlinear terms showed a slight difference for the variations of water elevation when calculated grid was small. They were also found to be minor when calculated grid size was increased. For verification of the numerical model, numerical results were compared with predicted values and field data. In the model, the effect of nonlinear advective terms proved not to be significant.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.129-135
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• 1990

A two-dimensional nonlinear tidal model of the Asan Bay has been formulated to examine the tide and related hydraulic phenomena. The $M_2$ tidal regime was first computed using the model and the model also was to derive the maximum bed stress and transport potential in the region. Preliminary assessment of relation between sediment transport and the maximum bed stress distribution determined from the model are described.

• Water for future
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• v.17 no.4
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• pp.293-302
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• 1984

The tidal and meteorological condition associated with wintertime surges in the Ease China Sea are described. The vertically-integrated finite difference model of the East china Sea have been used to investigate the surges generated during a period of 5 days in November, 1983 dynamically. Computed residual elevations are compared with hourly records form selected tide gauges along the west coast of Korea. Preliminary results on circulation pattern derived from the numerical model are presented and discussed. Further refinement of the model using current meter observation is presently being performed to provide more accurate information on bottom stress distribution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.240-249
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• 1993

The suspended sediment mechanism was systematically investigated by analyzing existing data together with new data obtained under several wave folds. A simple empirical formula has been developed to predict the time-averaged suspended sediment concentration above movable bed by the effect of wave and current interaction. The present study shows linear dependency of the diffusion coefficient of suspended sediment on the eddy viscosity coefficient obtained by considering the ripple geometry. Furthermore, it is proved that reference sediment concentration is reduced by the effect of ripple asymmetry.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.1-11
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• 1995

A numerical shallow water wave deformation model to solve unsteady mild slope equation was develope(1. The energy equation of Izumiya and Horikawa(1984) for wave breaking and bottom friction was incorporated to estimate more realistically energy damping resulted from wave breaking and reflection. A numerical scheme for variable grid spacings was also introduced to complement the defect of unsteady mild slope equation limiting the grid spacings. This model was tested and compared with the existing analytic solutions and physical modelings, and applied to a practical situation.