• 한국방재학회:학술대회논문집
• /
• 한국방재학회 2008년도 정기총회 및 학술발표대회
• /
• pp.229-232
• /
• 2008

The Central East Sea Tsunami caused huge damage to the eastern coast of the Korean Peninsula, eapecially Imwon port was damaged relatively strongly beacause of water depth variation which makes the wave concentration on this port. there are many virtual tsunami in east sea which has a possibility of happening. So, it is very important to expect the region which may be damaged by vritual tsunmis. In this study, modified dispersion-correction terms are used. The modified scheme has the advantage of using the constant spatial grid size and time step size even in real topography. Dynamic linking technique and staggered grid system are used. Using this model some cases of virtual tsunami was simulated and check the region which is occured maximum wave heights on the eastern sea of the Korean peninsula.

• 한국항해학회지
• /
• 제19권1호
• /
• pp.1-8
• /
• 1995

The motion of a small boat in seas is affected in relatively higher degrees than the case of a larger ship by the specific characteristics of sea waves, i.e., the wave length and height. Ship's motion caused by sea waves is a matter of special importance to small fishing boats, because they carry out fishing job in rough seas frequently. This is an experimental study on the rolling and pitching motions of full scale ship. In the experiment, the ship's motions were measured for head, how, beam, quarter and following seas. The experiment were carried out on board the training ship Pusan 404(160 GT) in the adjacent waters off NAM HYENG JAE DO on Dec. 13th 1994. The sea condition during the measurements was that wave height 2.5m, no swell and the wind velocity of 12 m/sec. Some statistic considerations were given to the observed data by the series analysis methods and discussed in this paper.

• 수산해양기술연구
• /
• 제42권1호
• /
• pp.38-43
• /
• 2006

The 3-D modeling of ocean finite element method(OFEM) using $k-{\varepsilon}$ turbulent model and tetrahedron grids has been used to investigate the internal wave generation during the expansion of the deep water from the open sea to the shelf with a simple shape, which can be widely used in the fields of submarine development, ocean environment and meteorology, etc. In this paper, the detailed configuration of internal wave with its length and height and also the distribution of salinity and turbulent kinematic energy, etc. were derived. It is hoped that this OFEM method can be successfully applied to the numerical calculation of internal wave for and the oceanographic problems (tidal flows around underwater hill, plateau, Georges Bank, etc.) and ocean engineering problems(flow past artificial sea reefs) in future.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2006년도 학술발표회 논문집
• /
• pp.574-578
• /
• 2006

Tidal amplification by construction of the sea-dike and sea-walls had been detected not only near Mokpo Harbor but also at Chungkye Bay which is connected with Mokpo Harbor by a narrow channel. This brings about increase of tidal flat area and in particular increase of surge-wave combined runup during storms. The purpose of this study is to examine an efficient operational model that can be used by civil defense agencies for real-time prediction and fast warnings on wind waves and storm surges. Instead of using commercialized wave models such as WAM, SWAN, the wind waves are simulated by using a new concept of wavelength modulation to enhance broader application of the hyperbolic wave model of the mild-slope equation type. Furthermore, The predicting system is composed of easy and economical tools for inputting depth data of complex bathymetry and enormous tidal flats such as Mokpo coastal zone. The method is applied to Chungkye Bay, and possible inundation features at Mokpo Harbor are analyzed.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.191-192
• /
• 2003

A numerical method for a wave diffraction problem in three-dimensional channels is developed. The physical models are various shapes of channel connected to the open sea. When a ship or an offshore structure is moored in various configurations of channel connected to an open sea, the prediction of the hydrodynamic force exerting on the moored ship could be important for the prediction of its motion. It is assumed that the fluid is inviscid and incompressible and its motion is irrotational. From the continuity equation, the Laplace equation can be obtained as the governing equation. The surface tension at free surface is neglected, and wave amplitude is assumed to be small compared to the wave length. Then the free surface condition can be linearized. The numerical method used here is the localized finite element method based on a variational formulation

• 한국안전학회지
• /
• 제24권1호
• /
• pp.37-42
• /
• 2009

The present study is to estimate the effect of wave height affecting at the front face of breakwater systems, when a submarine trench is dredged in the distant offshore from outer breakwater. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine trench on the sea bed designated by single horizontal long-rectangular system. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height reduction at the front face of breakwater systems are approximately 20% by the effect of placing long trench on the sea bed. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field.

• 한국지구과학회지
• /
• 제43권4호
• /
• pp.520-531
• /
• 2022

The Yellow Sea experienced glacio-eustasy sea-level fluctuations during the Quaternary period. In the middle part of the Yellow Sea, the Quaternary successions were accumulated by alternating terrestrial, paralic, and shallow marine deposits that reflected the fluctuating sea levels. A long core of 69.2 m was acquired at the YMGR-102 site (33°50.1782'N and 123°48.3019'E) at a depth of 72.5 m in the middle of the Yellow Sea. A four-layered geoacoustic model was reconstructed for the sedimentary succession. It was based on seismic characteristics from 3.5 kHz SBP and air-gun seismic profiles and 96 grain-size properties in the core sample from YMGR-102. For the underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method. The geoacoustic model of YMGR-102 can contribute to the reconstruction of geoacoustic models, reflecting the vertical and lateral variability of the acoustic properties in the continental shelf of the middle Yellow Sea.

• 대한조선학회논문집
• /
• 제43권3호
• /
• pp.384-391
• /
• 2006

RCS effects of long-crested wave surfaces to marine targets are numerically analyzed using a 4-path model and a direct analysis method, developed based on physical optics and a combined method of physical optics/geometric optics, respectively. Reflectivity of long-crested wave surfaces is described with 'Fresnel reflection coefficients' The MPM(modified Pierson-Moskowitz) ocean spectrum is adopted to simulate long-crested waves in the direct analysis method. A numerical analysis of a benchmark model assures the validity of both methods. The direct analysis method is applied to the RCS calculation of electromagnetically large marine targets, which are vertically oriented or slanted to the long crested wave surfaces randomly generated with various significant wave heights. The long-crested wave surface much highly increases the RCS of the marine target, but those effects are decreased as the significant wave height grows up. At low elevation angle, the vertical model has entirely high RCS comparing slanted model, and the RCS of vertical flat plate is the highest on the calm sea surface, while those of slanted flat plates are the lowest on the calm sea surface. The RCS of marine targets on continuously-varying sea surface is more coherent at lower elevation angles, as well.

• 한국해양학회지:바다
• /
• 제8권3호
• /
• pp.274-284
• /
• 2003

본 연구에서는 제 3세대 파랑 모형인 WAVEWATCH-III모델 (Tolman, 1999)과 기상청 해양기상 관측부이(4기) 자료를 이용하여 파랑인자 특성에 관한 분석이 이루어졌다. 풍속이 증가한 후 약 2-3시간 후에 유의파고가 커지고, 풍속과 유의파고의 상관성은 비교적 외해에 위치한 동해 부이에서 크게 나타났다. 육풍 발생 시 두 인자 사이의 상관계수 값이 급격히 떨어졌으며, 풍속과 파고 편차 시계열 자료에서는 동채부이를 제외하고 지배적인 조석주기가 발견되었다 부이 자료와의 비교를 통하여 WAVEWATCH-III모델의 파랑 모의 성능을 진단한 후에, 쿠로시오 해역과 동해 해역의 수치 실험을 통해서 파랑의 진행 방향에 대해 반대 방향으로 해류가 흐를 때는 파고는 높아지고, 파장은 짧아진다는 사실을 재확인했다. 또한 이러한 효과는 풍속이 약하거나 해류가 강할 때 더 커지는 양상을 나타냈으며 이에 대한 정량적인 결과를 제시하였다.

• Structural Engineering and Mechanics
• /
• 제57권5호
• /
• pp.951-968
• /
• 2016

Long-span cross-strait bridges extending into deep-sea waters are exposed to complex marine environments. During the construction stage, the flexible freestanding bridge towers are more vulnerable to environmental loads imposed by wind and wave loads. This paper presents an experimental investigation on the dynamic responses of a 389-m-high freestanding bridge tower model in a test facility with a wind tunnel and a wave flume. An elastic bridge model with a geometric scale of 1:150 was designed based on Froude similarity and was tested under wind-only, wave-only and wind-wave combined conditions. The dynamic responses obtained from the tests indicate that large deformation under resonant sea states could be a structural challenge. The dominant role of the wind loads and the wave loads change according to the sea states. The joint wind and wave loads have complex effects on the dynamic responses of the structure, depending on the approaching direction angle and the fluid-induced vibration mechanisms of the waves and wind.