• 한국해안·해양공학회논문집
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• 제34권6호
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• pp.211-221
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• 2022

파의 처오름높이는 제방, 호안 및 방파제와 같은 해안 구조물의 설계에 영향을 미치는 가장 중요한 매개변수 중 하나이다. 본 연구에서는 비정수압 수치모형인 SWASH(Zijlema et al., 2011)를 이용해 고정된 수중 및 부유식 사각형 구조물에 의한 고립파의 처오름높이 저감 효과를 분석하였다. SWASH 수치모형이 고립파의 전파, 쇄파 및 처오름현상을 매우 잘 재현하는 것을 확인하였다. 또한 수중 및 부유식 사각형 구조물에 의한 고립파의 파랑변형을 잘 재현하는 것을 확인하였다. 마지막으로 수중 및 부유식 사각형 구조물의 처오름높이 저감 효과를 검토하였다. 부유식 구조물의 에너지 감쇠효과는 수중 구조물보다 크고, 처오름높이 저감에 더 효과적인 것으로 나타났다.

• 한국해안해양공학회지
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• 제19권6호
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• pp.557-564
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• 2007

타원형 수중천퇴가 있는 지형을 통과하며 변형하는 파랑을 실험한 Vincent and Briggs(1989)의 실험조건을 수치모의하여 규칙파 변형에 대한 파랑과 흐름의 상호작용 효과를 연구하였다. 수치모의를 위해 흐름모형 SHORECIRC와 파랑모형 REF/DIF 1 그리고 SHORECIRC와 파랑모형 SWAN을 결합한 모형과 파랑과 흐름을 동시에 계산하는 FUNWAVE를 이용하였다. 이 수치모의로 부터 수중천퇴상에서 발생된 쇄파류는 수중천퇴후면의 파집중현상을 방해하고, 파랑을 천퇴중심축의 바깥쪽으로 굴절시켜, 파고를 상대적으로 감소시키는 역할을 하는 것을 확인할 수 있었다. 두 결합모형의 수치모의 결과는 쇄파류의 영향을 고려하지 않는 파랑모형만의 결과보다 실험치와 일치하였으나, 중복파가 발생되는 경우 SWAN모형과 REF/DIF모형으로부터 계산되어지는 잉여응력(radiation stress)에 문제가 있다는 것을 알 수 있었다. 또한, FUNWAVE를 이용한 수치모의는 실험결과와 완벽히 일치하였다. 이는 파랑쇄파류의 파랑변형에 미치는 역할의 중요성을 확인시켜주는 것이다.

• 한국항해항만학회지
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• 제41권2호
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• pp.55-62
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• 2017

A nearshore current or a wave-induced current is an important phenomenon in a nearshore zone, which is composed of longshore, cross-shore, and rip currents. The nearshore current is closely related to the occurrence of coastal accidents by beachgoers. A considerable number of coastal accidents by beachgoers involving the rip current have been reported at Jungmun Beach. However, in studies and observations of the nearshore current of Jungmun Beach, understanding of the rip current pattern remains unclear. In this study, a scientific approach is taken to understand the nearshore current and the rip current patterns at Jungmun Beach by numerical computation for year of 2015. From results of numerical computation, the occurrence and spatial characteristics of the rip current, and the similarities between the rip current and incident wave conditions are analyzed. The primary results of this study reveal that the rip currents are frequently generated at Jungmun Beach, especially in the western parts of the beach, and that the rip currents often occur with a wave breaking height of around 0.5 ~ 0.7 m, a wave period of around 6 ~ 8 seconds, and a breaking angle of around 0 ~ 15 degrees.

• 한국해양공학회지
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• 제23권1호
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• pp.7-15
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• 2009

The aim of this study was to survey the effects of the beachface gradient on 3-D currents around the open inlets of submerged breakwaters. First, the numerical model was validated by a comparison with existing experimental data. This model is able to consider the flow through a porous medium with inertial, laminar, and turbulent resistance terms, i.e. simulate directly WAve?Structure?Seabed/Sandy beach interaction, and can determine the eddy viscosity with a LES turbulent model in a 3-Dimensional wave field (LES-WASS-3D). Using the numerical results of this model, the 3-D currents around the open inlets of submerged breakwaters were examined in relation to the beachface gradient. Moreover, the wave height distribution and mean flow around them are also discussed, as well as the distribution of the wave breaking points over the crest.

• 한국해양공학회지
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• 제33권1호
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• pp.68-75
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• 2019

A low-crested structure (LCS) is an excellent feature not only because it provides shore protection but also because it is fully submerged. However, in order to properly control waves, it is necessary to maintain a certain range of crest height and width in consideration of the wave dimensions at the installation area. According to previous studies, an LCS has some wave breaking effect when the crest width is more than a fourth of the incident wavelength and the crest depth is less than a third of the incident wave height. In other words, if the crest width of the LCS is small or the crest depth is large, it cannot control the wave. Therefore, when an LCS is installed in a large sea area with a great tidal range in consideration of the landscape, waves cannot be blocked at high tide. In this study, the hydraulic performances of a typical trapezoidal LCS with a constant crest height and a low-crested structure with an adjustable crest height, which was called a tide-adapting low-crested structure (TA-LCS) in this study, were compared and evaluated under various wave conditions through hydraulic experiments. It was found that the wave transmission coefficients of the TA-LCS at high tide were lower than the values for the typical LCS based on empirical formulas. In addition, the hydraulic performances of the TA-LCS for wave reflection control were 12.9?30.4% lower than that of the typical LCS. Therefore, the TA-LCS is expected to be highly effective in controlling the energy of incoming waves during high tide even in a macro-tidal area.

• 한국안전학회지
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• 제31권2호
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• pp.70-75
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• 2016

Recently, coastal erosion has been widely in progress and the erosion level becomes also serious in the world wide, espeically in East Sea in Korea. Since it would threaten the life, economics and security risk, it is necessary to much comprehend the reason why coastal erosion has occurred according to the geographical characteristics. Meanwhile, analysis about hydrodynamics of the solitary wave such as tunami in swash zone is needed for the best management practice of coastal erosion. Solitary wave is nonlinear wave and can be reproduced in the laboratoy scale by openning suddenly a sluice gate with water head difference, of which methodology was found in the literature, since it could be simply determined by a significant wave height. Thus, in this sutdy the generation of solitary wave was experimentalized using the sluice gate. Experimental conditions were classified by angles of a beach slope, a water level in a beach slope and a difference of water level between in a headtank and a channel bed. Two kinds of dimensionless analyses based from experimental results in this study were presented; the first analysis indicates nondimensionalization between the wave height and the water level in a beach slope in order to investigate characteristics of solitary wave approaching the beach. The second shows the other nondimensionalization between dynamic pressure and static pressure on a beach slope to investigate the relationship between wave breaking and wave pressure. Under the same conditions as laboratory experiments, the numerical results computed with a SWAN model embedded in FLOW 3D were compared in terms of wave height, and pressure on the beach slope, which shows good agreement with each other. Overall results from this study could provide fundamental hydraulic data for the reliabile verification of numerical simulation results about coastal erosion in swash zone caused by solitary waves.

• 한국해양환경ㆍ에너지학회지
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• 제9권3호
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• pp.141-147
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• 2006

해양의 활용범위를 확대시키기 위해서 방파제는 필수적인 요소이며 특히 친환경적인 부소파제의 활용은 증대될 것으로 기대된다. 본 연구에서는 친환경 소재인 폴리에틸렌 파이프와 시트를 활용하여 새로운 개념의 부소파제용 부체를 개발하며, 이에 대한 소파 성능평가를 위하여 기초적 실험연구를 수행한다. 입사되는 파랑은 연결된 파이프와 시트를 통과하면서 일부는 반사되고 일부는 투과되는데, 투과되는 파랑은 파이프를 지나면서 와류유기가 발생하여 파랑 에너지가 소멸된다. 따라서 입사파랑 에너지를 감소시킬 수 있다. 개발된 부체의 성능평가를 위하여 규칙파 및 붙규칙파에 대한 수리모형 실험을 수행한다. 입사파랑 주기가 6초 이하 조건에서는 소파 성능이 양호하였으나, 장주기의 입사파랑에 대해서는 부체 전체가 해수면과 같이 거동하면서 소파성능을 거의 나타내지 못하였다. 향후 소파성능 개선을 위한 추가적인 연구가 요구되어진다.

• 한국해양공학회지
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• 제33권3호
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• pp.280-288
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• 2019

A submerged breakwater is one of the coastal structures used to reduce wave energy and coastal erosion. However, a submerged breakwater has a negative aspect in that a strong rip current occurring around an open inlet due to a difference in mean water levels at the front and rear sides of the structure leads to scouring. Such scouring has a bad effect on its stability. In order to eliminate this kind of demerit, this study investigated an artificial reef of the overflow type with openings. We also developed a program where the flows around the artificial reef of the overflow type could be analyzed numerically. An unstructured grid system was used to cover the various geometries, and the level set method was applied to treat the movement of the free surface. To verify these numerical schemes, hydraulic physical tests were performed on the submerged breakwater and double breaking type artificial reef. Then, the wave height and velocity distribution around the reef were examined using the experimental results. Comparisons between the results of hydraulic and numerical tests showed reasonable agreement.

• 한국해안해양공학회지
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• 제3권2호
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• pp.65-71
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• 1991

쇄파변형에 대한 종래의 연구는 흐름을 고려하지 않은 경우가 대부분 이였다. 즉 파랑의 변화가 흐름의 변화에 미치는 영양에 대해서는 어느 정도 연구가 수행되어 왔으나, 파랑에 의해 발생한 흐름이 다시, 쇄파후 파고감사, 평균수위 상승 및 파향각 등 쇄파대내와 제반 수리양의 변화에 대해 어떻게 기여하는가에 대해서는 거의 보고되어 있지 않은 실정이다. 본 연구에서는 쇄파에 의해 발생하는 에너지 손실과 밀접한 관계가 있다고 알려진 연안류를 고찰하고, 이 연안류가 쇄파후 파고감사 및 평균수위 변동, 그리고 파향각에 어떻게 영향을 미치는가에 대해서 검토하고, 연안류가 존재하지 않은 경우와 비교 고찰한다.

• 한국기계가공학회지
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• 제12권1호
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• pp.15-21
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• 2013

The safety and stability of 5MW class offshore wind turbine Jack-up platform was investigated through ocean basin experiment. For simulating the environmental condition of yellow sea in the South Korea, diverse waves, winds and currents were performed based on Froude's number. Regular wave and irregular wave based on Froude's number were applied to the wind turbine structure. In experiments, the height and period of regular wave type were scaled down as the 1:50 ratio of real wave condition. Irregular wave type was simulated with TMA(Texel Storm, Marsen and Arsloe)spectrum. The vertical reaction force, resonance period and wave pressure applied to multi-supporters of wind offshore structure were measured experimentally. Finally, the results showed that the capsizing situation of the offshore structure was generated by the severe environmental condition.