• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.7-17
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• 2007

Based on the Boussinesq wave model, the wave distribution in the Chagui-Do sea area in Jeju was simulated by applying the directional irregular waves at an incident boundary. The time and spatial variations of monthly mean wave height and period were investigated, which aims to provide basic information on optimal sites for wave power generation. The grid size and time interval of the Boussinesq wave model were validated by examining wave distributions around a surface piercing wall, fixed at sea bottom with a constant slope. Except for the summer season, the significant wave height is dominated by wind waves and appears to be relatively high at the north sea of Chagui-Do, which is open to the ocean, while it is remarkably reduced at the rear sea of Chagui-Do because of its blocking effect on incident waves. In the summer, the significant wave height is higher at the south sea, and it is dominated by the swell waves, which is contributed by the strong south-west wind. The magnitude of significant wave height is the largest in the winter and the lowest in the spring. Annual average of the significant wave height is distinctively high at the west sea close to the Chagui-Do coast, due to a steep variation of water depth and corresponding wave focusing effect. The seasonal and spatial distribution of the wave period around Chagui-Do sea reveals very similar characteristics to the significant wave height. It is suggested that the west sea close to the Chagui-Do coast is the mast promising site for wave power generation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.555-560
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• 2014

In Korea, quantitative growth rate of artificial reef construction is supposed to reach the peak point therefore, new approach is needed to the point of artificial reefs business. Functional reefs like shellfish reefs, recreational reefs, seaweed reefs as well as fish reefs are beneficial alternatives. This study conducted hydraulic testing to assess the stability of new types of artificial reefs (ARs) constructed to promote the growth of shellfish and seaweed. The results of this study revealed that some dimensionless design parameters affected the stability of new types of artificial reef under various wave and water depth conditions in the fixed bed condition. The findings also highlight the importance of hydraulic experiments in solving problems that have emerged in the design and construction of artificial reefs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.153-165
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• 2018

In this study, the performance of irregular wave field generation of olaFlow is first verified by comparing the frequency spectrum of the generated waves by the wave-source using olaFlow and the target wave. Based on the wave performance of irregular waves of olaFlow, the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy around the three-dimensional permeable submerged breakwaters, which act as the main external forces of the salient formation, are numerically investigated. The numerical results show that as the gap width between breakwaters decreases, the wave height in the center of the gap increases and as the gap width between breakwaters increases, the longshore currents become stronger. As a result, it is possible to understand the formation of the salient formed behind the submerged breakwaters.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.82-82
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• 2015

해안 대수층은 해수와 담수가 공존하는 지역으로 상대적으로 밀도가 큰 해수가 대수층의 담수 아래에 쐐기형태로 존재하게 된다. 이러한 쐐기형태의 해수와 담수의 경계면은 압력경도의 평형에 의해 경계면이 유지되며, 해수면 또는 지하수위가 변동할 경우 해수-담수 경계면의 균형이 무너짐과 더불어 압력경도의 평행이 이루어질 때 까지 해수-담수 경계면의 이동이 계속 진행된다. 수위 변화의 주요 원인으로는 지구온난화 및 기후변화로 인한 지속적인 해수면 상승과 도서지역의 인구증가 및 산업화로 인한 무분별한 지하수의 사용 등에 의한 지하수위 저하 등을 꼽을 수 있다. 이와 같은 원인으로 해안 및 도서지역에서는 해안 대수층의 해수침투거리가 증가하여 지하수 이용에 큰 어려움을 겪고 있다. 이에 해안 대수층의 해수침투 범위 및 거리를 추정하기 위한 많은 연구들이 다양한 분야에서 지속해서 이루어지고 있지만, 서로 밀도가 다른 해수와 담수가 공존하는 해안 대수층 내의 수리특성을 명확히 파악하기에는 아직까지 미흡한 점들이 많다. 과거에는 Darcy의 법칙 및 Ghyben-Herzberg 식에 근거한 이론적인 연구들이 주로 이루어졌고, 근래에 현장관측이나 수리모형실험이 국내 외적으로 수행되고 있으나, 모든 영역의 지하수의 특성을 조사하는 것이 사실상 불가능하다. 이에 최근에는 컴퓨터 성능의 비약적인 발전과 더불어 다양한 수치해석방법에 의한 수치모델들이 개발되어 시뮬레이션에 적용되고 있다. 하지만 거의 대부분의 수치모델은 해안 대수층 수리특성을 투수계수에 의존하고 있을 뿐, 대수층 내부의 해수-담수에 의한 밀도류의 유동특성을 전혀 고려하지 못한 채 정수압에 근거한 해수-담수 경계면에 대해 모의하고 있는 정도이다. 따라서 본 연구에서는 해안 대수층 내부의 유동현상을 투수계수에 의존하는 방법에서 탈피하여 대수층 매체의 입경, 공극, 형상 등을 고려할 수 있을 뿐만 아니라, 염분 및 온도차에 의한 밀도류를 해석할 수 있는 강비선형 수치모델을 개발하여 해수침투 현상을 직접 모의한다. 나아가 대부분의 이전 연구들에서 간과하고 있는 해안지역의 대표적 물리력인 파랑과 조석의 영향이 해안 대수층의 해수침투에 미치는 영향, 해안 대수층의 지하수위 및 해수면의 수위차에 의한 해수침투 특성 그리고 이를 제어 할 수 있는 새로운 대응기술을 제안하는 것을 목적으로 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4B
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• pp.243-251
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• 2012

To investigate the characteristics of rip current occurring at Haeundae beach, observations obtained from a buoy and a CCTV were analyzed and numerical experiments were conducted. During observed rip-current events, the CCTV images showed that a couple of wave-trains, which are close to regular waves with slightly different directions, propagated to the beach, and wavelet analyses of data from the buoy showed very narrow-banded spectra with a peak frequency. From the evidences, it was inferred that a known mechanism of generating rip current due to the nodal line area of honeycomb-patterned wave crest was one of the significant factors of rip current occurrences of Haeundae beach. The mechanism has been explained by the following: When two wave-trains with slightly different directions propagate to a beach, wave crests of the incident wave-trains form honeycomb pattern due to nonlinear interaction. The nodal lines of honeycomb pattern are developed in the cross-shore direction. And longshore currents flow toward the nodal line area which has very low wave energy. Consequently their mass flux is expelled through the area toward the sea direction. To confirm the generation, numerical experiments were performed using a nonlinear Boussinesq equation model. In the cases with two incident wave-trains with slightly different directions and with a monochromatic wave propagating over a submerged shoal, it was seen that the honeycomb pattern of wave crests was well developed, and thus rip currents were evolved along the nodal lines.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.180-188
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• 2017

Recently, as the strength of winds and waves increases due to the climate change, abnormal waves such as swells have been also increased, which results in the increase of downtime events of loading/unloading in a harbour. To reduce the downtime events, breakwaters were constructed in a harbour to improve the tranquility. However, it is also important and useful for efficient port operation by predicting accurately and also quickly the downtime events when the harbour operation is in a limiting condition. In this study, numerical simulations were carried out to calculate the wave conditions based on the forecasted wind data in offshore area/outside harbour and also the long-term observation was carried out to obtain the wave data in a harbour. A forecasting method was designed using an auto-regressive (AR) and artificial neural networks (ANN) models in order to establish the relationship between the wave conditions calculated by wave model (SWAN) in offshore area and observed ones in a harbour. To evaluate the applicability of the proposed method, this method was applied to predict wave heights in a harbour and to forecast the downtime events in Pohang New Harbour with highly complex topography were compared. From the verification study, it was observed that the ANN model was more accurate than the AR model.

• 한국해양학회지
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• v.22 no.1
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• pp.1-8
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• 1987

The Sinyangri Formation crops out in the vicinity of the Seongsan Peninsula, Cheju Island. Based on sedimentary structures, texture and composition, the lithologic sequence has been classified, in ascending stratigraphic order, into three lithofacies: parallel laminated sandstone facies (Facies I): conglomerate facies(Facies Il); and cross stratified sandstone facies (F acies Ill). Wedge-to-parallel, seaward-inclined in low angle less than 10$^{\circ}$lamina -sets with alternations of coarseand fine-grained sediments in the Facies I are the characteristic sedimentary structures in the foreshore depositional environment. Grains of this faciesare well sorted with good roundness compared with the other two facies, partly showing inverse graded bedding. Facies II,largely composed of claset-supported,very poorly-sorted conglomerates,does not pinch out but occurs continuously along the Sinyangri beach.Interstitial spaces between the clasts are mostly infilled with volcanic-ash and small amounts of well-rounded shell fragments.Maximum bed thickness as well as the size of imbedded basaltic clasts decreases to the south(toward Sinyangri). Large clasts with parallel lamination originated from the underlying Facies i,are generally elongated parallel to the bedding plane and display no systematic horizontal variations in size indicative of in-situ clasts.In view of the facts above it seems that large gravels from the basaltic rocks are transgressive lag conglomerates which are partly affected by the combination of longshore currents and propagating wave.Local occurrence of cross-strata dipping toward the south in the upper part of Facies IIreinforces the evidence of the action of longshore currents. Facies IIIis characterized by bidirectional trough cross-starifiction and wave ripples associated with the upper shoreface(surfzone) environments.In summary,the Sinyangri Formation represents the depositional environments of foreshore to upper shoreface truncated by disconformity between Facies Iand II.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1716-1720
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• 2007

연안 해역에서의 표사는 하천에서의 유사가 주요한 공급원이므로 산지-하천-해안을 통합한 유사 및 표사에 관한 관리가 필요하며, 해안수리 및 환경적인 측면에서 강성 연안구조물의 건설을 통하지 않고 연안에서의 침식을 억제해야하는 방지대책의 수립 요구가 증대하고 있는 실정이다. 즉 연안에서의 침식, 퇴적관계는 토사공급원의 장기적인 확보여부가 중요하며 하천에서 해안역으로 공급되는 유사량을 예측하고 또한 이들이 어떻게 효과적으로 연안 해역으로 이송되어 가는가를 파악하는 것은 연안표사문제를 이해하는데 매우 중요한 요소이다. 이를 위해서는 무엇보다도 하천에서 연안 해역으로의 유사량을 파악하는 것이 중요하며 그리고 하천 유사량이 하구에 사주를 형성하고 어떤 형태를 거쳐 연안표사로 이동하는가 하는 특성을 파악할 필요가 있다. 울산광역시 울주군 온산읍에 위치한 회야강의 하구폐색은 1990년대 중반부터 연구의 관심이 되어오고 있으며, 1986년 회야강 상류 회야댐 건설 이후 하구폐색이 가속화됨에 따라 매년 회야강 하구에서의 준설이 필요한 실정이다. 특히 회야강 하구부에서는 파랑류, 취송류와 하천류 뿐만 아니라 해류나 조류 등에 의한 흐름과 지형특성등 복합적으로 발생하는 하구현상에 의해 하구에서의 사주 발달이 상대적으로 강하여 하구폐색이 강하게 나타나고 있다. 이의 대책으로 최근 회야강 하구부에 도류제가 건설되었으며 이에 따른 장기적인 하구부 하상변동특성과 토사이동의 특성 파악이 요구되고 있는 실정이다. 본 연구에서는 이 같은 관점에서 회야강 하구부의 도류제 설치에 따른 하구에서의 지형변동과 유송토사량의 특성을 파악하기 위해 하천 상류부에서는 동적 평형상태의 유사량을 가정하고 하상재료 및 유사는 혼합입경으로 하여 하상고 및 하상교환층 중의 입도조성의 시간변화를 구하여 1차원적인 하상변동과 토사이동 특성을 해석하였다.했을 때, 대표입경을 통해 얻은 조도계수가 보정 조도계수보다 다소 작은 것으로 해석되었다.하고자 한다.해결책을 얻어내는 상호보완적인 결과를 추구한다. 그가 디자인하는 작품은 전형적인 이미지를 내포하지 않는다. 즉 그의 작품은 기존의 가치와 이념적인 것은 배제하고, 창의적인 개념을 도출하였다.형모서리는 건물 특화 성격이 강하므로 불가피할 경우 소형 액센트 광고 위치를 미리 벽면으로 할애하는 것이 경관 및 입면계획에 유리한 것으로 분석되었다. 불확실도 해석모형 등의 새로운 기능을 추가하여 제시하였다. 모든 입출력자료는 프로젝트 단위별로 운영되어 data의 관리가 손쉽도록 하였으며 결과를 DB에 저장하여 다른 모형에서도 적용할 수 있도록 하였다. 그리고 HyGIS-HMS 및 HyGIS-RAS 모형에서 강우-유출-하도 수리해석-범람해석 등이 일괄되게 하나의 시스템 내에서 구현될 수 있도록 하였다. 따라서 HyGIS와 통합된 수리, 수문모형은 국내 하천 및 유역에 적합한 시스템으로서 향후 HydroInformatics 구현을 염두에 둔 특화된 국내 수자원 분야 소프트웨어의 개발에 기본 토대를 제공할 것으로 판단된다.았다. 또한 저자들의 임상병리학적 연구결과가 다른 문헌에서 보고된 소아 신증후군의 연구결과와 큰 차이를 보이지 않음을 알 수 있었다. 자극에 차이가 있지 않나 추측되며 이에 관한 추후 연구가 요망된다. 총대장통과시간의 단축은 결장 분절 모두에서 줄어들어 나타났으나 좌측결장 통과시간의 감소 및 이로 인한 이 부위의 통과시간 비율의 저하가 가장 주요하였다. 이러한 결과는 차가운 생수 섭취가 주로 결장 근위부를 자극하는 효과를 발휘하는 것이 아닌가 해석된다. 이와 같은 연구결과를 통해 생다시마를 주원료로 개발된 생다시마차와 생다시마 음료가 만성 기능성 변비 증세를 개선하는 효능이 잠재적으로 있음을 확인하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.591-598
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• 2015

A hydraulic characteristics in the surf zone such as wave breaking points, wave set-down, wave set-up, wave-induced currents and run-up heights are studied using the SWASH model during Typhoon NAKRI(1412) in Haeundae Beach. Incident wave conditions is obtained from one-hourly observed wave data by KHOA and irregular wave by JONSWAP spectrum is given as an open boundary condition in the model. A Wave-induced current patterns by the SWASH model is compared with the observed currents and sediment flux patterns in that areas, the calculated maximum wave run-up heights in the model is compared with the video monitoring data, the empirical formula by Stockdon et al. and Mase. A dominant longshore currents toward the east of the beach appears due to the effect of incident wave direction and the geographical features and some rip currents occurs at the central part of the beach. The maximum wave run-up height(1.15 m) by the SWASH model shows a similar pattern with the video monitoring data(1.26 m) and the magnitude shows a similar result(1.33m) by Stockdon et al.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.247-258
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• 2014

To evaluate the influence of the external force components on the littoral currents in the Gusipo beach, Jeonbuk, West Coast of Korea where a wide tidal sand flat developed, a coupled hydrodynamic model considered real time tidal currents and wave-induced currents was constructed in which the EFDC for tides and tidal currents, the SWAN for waves and the SHORECIRC for wave-induced currents were used as the hindcasting models. A series of field observations for tides, tidal currents and incident waves were carried out and especially to observe the littoral currents in the tidal sand flat, the GPS mounted and light weight drogues were used. Also wind data were collected from the adjacent weather station. To analyze the littoral current components, the numerical drogue tracking results considered real time winds, tides and waves were compared with the field drogue data. The drift speed of numerical drogues was reproduced as the range of 68.0~105.2% compared with the field data and the velocity error of main direction component showed a good result as -16.7~10.0%. As a result, in the mild slope tidal flat including wide surf zone, the tides and winds were the major affection component of the littoral currents, on the other hand, the wave-induced currents seemed the minor component when the incident wave heights were relatively small.