• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.241-244
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• 2008

The decomposition of incident and reflected wave on the two-dimensional experimental flume is very important to elucidate the phenomena between waves and coastal structure such as submerged breakwater or rubble-mound breakwater. In generally, two or three point methods are widely used to decompose waves. Even though three point method gives more accurate result, it requires more wave gauge to install than two point method. Sometimes, this causes economic or measurement problems. In this study, therefore, the applicability of two point method was investigated by using Eigenfunction expansion method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.166-179
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• 2018

This study aims at numerically investigating the water-surface characteristics such as wave height distribution depending on the current direction around the three-dimensional permeable submerged breakwaters in wave-current coexisting field which has not been considered in detail so far. In addition, the characteristics of the velocity field including the average flow velocity, longshore current and turbulent kinetic energy, which act as the main external forces of formation of salient, are also examined. For numerical analysis, olaFlow which is open source code of CFD was used and the numerical tests included different types of target waves, both regular waves and irregular waves. Numerical results indicated that wave height variation with wave following or opposing a current behind the submerged breakwater is closely related to turbulent kinetic energy. Furthermore, it was found that weaker longshore currents are formed under wave-current coexisting field compared to the non-current conditions, and transport flow is attenuated. As a result, it was possible to understand the influence of current existence and direction (following and opposing) on the formation of the salient formed behind the submerged breakwaters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.345-354
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• 2008

In this present study, we made a first attempt to investigate physical transformations of incident waves in surf and swash zone and hydrodynamic phenomena of detached and submerged breakwaters. For an accurate simulation of the complicated wave deformation, Three-Dimensional numerical model with Large Eddy Simulation has been developed recently and expanded properly for the current applications, which is able to simulate an accurate and direct WAve Structure Sandy seabed interaction (hereafter, LES-WASS-3D). LES-WASS-3D has been validated through the comparison with experimental results for limited cases, and has been used for the simulation of wave run-up on sandy beach, mean fluid flows over and around submerged structures and swash zone (alongshore/rip current), and spatial distribution of wave height in wide fluid regions. In addition, a strategy of efficient deployment ($Y/L_i=1.50{\sim}1.75$, $W/L_r=0.50$) of the submerged breakwaters has been discussed.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2004.08a
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• pp.150-159
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• 2004

In the present paper, the hydrodynamics properties of a Rahmen type flexible porous breakwater with dual fixed-pontoon system interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged a the side edges of dual fixed pontoons, and a submerged horizontal membrane that both ends are hinged at the steel frames mounted pontoons. The dual vertical membranes are extended downward and hinged at bottom steal frame fixed into seabed. The wave blocking and dissipation mechanism and its effects of permeability, Rahmen type membrane and pontoon geometry, pre-tensions on membranes, relative dimensionless wave number, and incident wave headings are thoroughly examined.

• Journal of Navigation and Port Research
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• v.31 no.9
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• pp.785-791
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• 2007

In this paper we proposed a model that the deformation of the submerged rubble mound breakwaters composed with materials of various size, induced by wave action, can be computed. The water particle kinematics by waves in porous mound structure are computed by CADMAS-SURF, then the deformation of structure is computed using DEM module. To investigate the interaction of wave and sectional deformation of structures, analysis is accomplished by two steps. Analysis at the first step is executed with incipient mound. And analysis at the second step is executed with deformed mound by wave action. Furthermore, behaviors of materials are influenced by various properties such as the contact stiffness and the friction angle. Therefore, in order to present the behavior of the element caused by various properties, computations are accomplished with random coefficients by using the Monte Carlo simulation.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.245-248
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• 2003

Bragg반사는 입사된 주기파의 파장이 해저지형의 파장의 두 배가 될 때 공명현상(resonance)에 의해 반사율이 매우 커지는 물리 현상을 말한다. 즉, 외해에서 주기성을 띄는 파랑이 입사해 올 때, 특정형태의 해저지형을 이용하면 상당량의 에너지를 외해로 반사시킬 수 있다. 이와 같은 Bragg 반사개념을 수중방파제(submerged breakwater)에 응용하면 항만이나 방파제 등의 해안구조물을 경제적으로 설계 및 보호 할 수 있고, 해안선 보호 및 불필요한 퇴적 등을 고려한 연안개발계획의 효율적 수립이 가능하다. (중략)

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.42-48
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• 2002

잠제는 주로 입사하는 파를 천단에서 강제쇄파시키거나 마찰을 통한 에너지 감소로 파를 제어하므로 잠제의 천단수심과 천단의 길이는 잠제의 성능에 가장 중요한 요소라고 할 수 있다. 일반적으로 잠제의 천단수심이 깊은 경우 잠제에 의한 파랑제어를 충분히 기대할 수 없으므로 입사파의 제어를 위한 적정한 천단수심이 필요하게 되고 천단수심이 얕아짐에 따라 천단상에서 파의 대칭성이 무너지는 비선형성분이 탁월해진다. (중략)

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.283-289
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• 2003

잠제는 수면 아래에 건설되는 대표적인 친환경의 해안ㆍ항만구조물로 일본을 위시한 외국에서는 이안제 등과 같은 대체표사제어구조물로 잠제를 다수 시공해 왔으며, 국내에서는 처음으로 부산시의 송도해수욕장에 해안침식방지를 위해 잠제를 건설하고 있다. 잠제에 의한 파랑제어의 주요한 메커니즘은 천단상에서의 입사파랑과 구조물과의 마찰 및 입사파랑의 강제쇄파에 의한 에너지 소산이다. (중략)

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.88-91
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• 2012

본 연구에서는 다양한 형상의 수중방파제를 이용하여 고립파(지진해일)에 대한 파랑의 제어기능을 검토하였다. 먼저, 연구를 수행하기 위하여 Navier-Stokes 방정식에 기초한 RANS 모형을 사용하였다. RANS 모형에서는 VOF기법을 이용하여 자유수면을 해석하였고, 또한 조밀한 격자간격을 사용하여 수치실험을 실시하였다. 수중방파제의 형상에는 삼각형, 반타원형, 직사각형 및 사다리꼴형을 사용하여 각각의 수중방파제 위를 통과하는 고립파를 해석하였다. 고립파의 파고와 여러 가지 형태를 갖는 각각의 수중방파제의 높이를 조절하면서 수중방파제를 지나는 고립파의 투과율을 해석하였다.

• Journal of Ocean Engineering and Technology
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• v.36 no.6
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• pp.364-379
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• 2022

Coastal communities have been vulnerable to extreme coastal flooding induced by hurricanes and tsunamis. Many studies solely focused on the overland flow hydrodynamic and loading mechanisms on individual inland structures or buildings. Only a few studies have investigated the effects of flooding mitigation measures to protect the coastal communities represented through a complex series of building arrays. This study numerically examined the performance of flood-mitigation measures from tsunami-like wave-induced overland flows. A computational fluid dynamic model was utilized to investigate the performance of mitigation structures such as submerged breakwaters and seawalls in reducing resultant forces on a series of building arrays. This study considered the effects of incident wave heights and four geometrically structural factors: the freeboard, crest width of submerged breakwaters, and the height and location of seawalls. The results showed that prevention structures reduced inundation flow depths, velocities, and maximum forces in the inland environment. The results also indicated that increasing the seawall height or reducing the freeboard of a submerged breakwater significantly reduces the maximum horizontal forces, especially in the first row of buildings. However, installing a low-lying seawall closer to the building rows amplifies the maximum forces compared to the original seawall at the shoreline.