• Title/Summary/Keyword: Submerged breakwater

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Numerical Analysis of Hydrodynamic Performance of a Movable Submerged Breakwater Using Energy Dissipation Model (에너지 소산 모델을 이용한 잠수된 가동식 방파제의 유체동역학적 성능 수치해석)

  • Kim, Do-Hyun;Koo, Weon-Cheol
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.4
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    • pp.287-295
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    • 2012
  • Hydrodynamic performance of a movable submerged breakwater was analyzed using energy dissipation model. Based on two-dimensional boundary element method the equation of motion including a viscous dissipation term proportional to velocity squared was solved by Newton-Raphson method. Energy dissipation coefficients as well as reflection and transmission coefficients of a submerged flat plate were calculated with various plate lengths and thickness. Both real and imaginary components of body displacement and forces were used to solve the motion of breakwater accurately. The effect of the magnitude of dissipation coefficient on the body displacement was evaluated. The results from the potential theory with no dissipation term were found to be an overestimate in resonance frequency.

Boundary Element Analysis on the Hydraulic Characteristics of Submerged Breakwater with Trapezoidal Type (사다리꼴형상 잠제의 수리특성에 관한 경계요소해석)

  • Kim Nam-Hyeong;Yang Soon-Bo
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.6 no.4
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    • pp.45-51
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    • 2003
  • The reflection and transmission of submerged breakwater with trapezoidal type are computed numerically using boundary element method. The analysis method is based on the wave pressure function with the contlnuit? in the analytical region including fluid and porous structures. Wane motion within the porous structures is simulated by introducing the linear dissipation coefficient and added mass coefficient. The results indicate that transmission and reflection coefficient are determined due to the change of slope of submerged breakwater with trapezoidal type.

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Wave Breaking and Breaking Wave-Induced High Frequency Pressure over Submerged Breakwater (잠제에 의한 쇄파 및 쇄파에 의해 발생하는 고주파수파동압)

  • Koichiro IWATA;Koji KAWASAKI;Hirokazu SUMI
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 2002.08a
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    • pp.14-23
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    • 2002
  • Wave breaking and breaking wave-induced hydrodynamics are very important subjects in the field of coastal and ocean hydrodynamics and engineering. In the coastal zone, a submerged breakwater has been increasingly popular, since it is one of nature-matching structures with multi- functions such as (1) wave energy dissipation by wave breaking and friction, (2) oxygen supply to sea by wave breaking and breaking wave, (3) water purification by entrained air bubbles, (4) keeping. good seascape. and (5) good habitat for sea livings. Recently, the breaking wave-induced high frequency pressure over a submerged breakwater is said to have a function of gathering sea livings around the structure, which has encouraged the construction of the submerged breakwater in coastal zone. (omitted)

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Wave Transformation of Submerged Breakwater with One Ray (단일 잠제에 의한 파랑변형에 관한 연구)

  • Kim, W.K.;Kang, I.S.;Kwak, K.S.;Kim, D.S.
    • Journal of Korean Port Research
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    • v.8 no.1
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    • pp.23-30
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    • 1994
  • This study discusses the wave transformation(wave reflection and transmission) by a impermeable submerged breakwater with one ray, and integrated horizontal wave pressure acting on the structure. Numerical method in this study is based on the simplified eigenfunction expansion method and linear wave theory. Although this method is very simple, the results give good agreement with the one of the strict eigenfunciton expansion method, especially, in case that the crown width of the submerged breakwater becomes longer and its crown water depth shallower. Therefore, it is concluded that this simplified method is one good method in planning coastal structures as like the submerged breakwater in this study, and computing their wave transformations.

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Optimum Inner Width of the Submerged Breakwater with Two Rows for the Controlling Long Period Waves (장주기파의 효율적인 제어를 위한 이열잠제의 최적간격)

  • Yun, D.Y.;Hur, D.S.;Kim, D.S.;Kang, J.B.
    • Journal of Korean Port Research
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    • v.9 no.2
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    • pp.51-64
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    • 1995
  • Generally, it is pointed out that the submerged breakwater with one row can not regulate the long period waves efficiently, because the crown width is very shorter than the wave length of the long period waves. Therefore, the wide crown is needed to raise the controlling efficiency for the long period waves. This study picks up the submerged breakwater with two rows which has smaller construction materials comparing to the one row and discusses the wave controlling function for the long period waves. Judging from the results obtained by using the strict dividing region method, the submerged breakwater with two rows can more regulate the long period waves than one row can, especially, in case that crown width and inner width of its construction come to be wider.

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Laboratory Observations of Nearshore Flow Patterns Behind a Single Shore-Parallel Submerged Breakwater (해안선에 평행한 단일 잠제 후면 연안 흐름패턴 관측 수리실험)

  • Choi, Junwoo;Roh, Min
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.29 no.3
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    • pp.139-146
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    • 2017
  • In order to understand the efficacy of submerged breakwater constructed for the beach protection, laboratory experiments were carried out by observing the characteristics of flow around a single shore-parallel submerged breakwater. The velocity field near the shoreline was measured by utilizing the LSPIV (Large-Scale Particle Image Velocimetry) technique, and mean surface and wave height distributions were observed around the submerged breakwater, according to various combinations of incident waves and submerged breakwaters. In this experiment, it was found that the mean flow pattern behind the submerged breakwater was determined by the balance among the gradients of mean water surface and excess wave-momentum flux (i.e., radiation stress tensors) which interact with the wave-induced current developed by the gradients on the rear and the side of the submerged breakwater. The divergent and convergent flow patterns behind the submerged breakwater (i.e., accretion and erosion response) of the numerical study of Ranasinghe et al.(2010) were observed in the measured velocity distributions, and their empirical formula mostly agreed with the experimental results. However, for some cases in this experiment, it was difficult to say that the flow pattern was one of them and was agreed with the empirical formula.

The Characteristics of Wave Energy Variations by Impermeable Submerged Breakwater Using VOF Method in Irregular Wave Fields (VOF 법에 의한 불규칙파동장에 있어서 불투과잠제에 의한 파랑에너지 변형특성)

  • 허동수;김도삼
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.15 no.4
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    • pp.207-213
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    • 2003
  • This study is to numerically investigate the characteristics of wave energy variations propagating over impermeable submerged breakwaters with irregular waves. Two-dimensional numerical wave flume based on the VOF method was used. VOF method is the most efficient capable of simulating free surfaces including wave breaking. From the computed frequency spectrum results, wave breaking play important role in ability of the submerged breakwaters to dissipate incident wave energy. In case of occurring wave breaking, our analysis shows that wave energy moves to short wave period on one-row impermeable submerged breakwater's lee side and is widely distributed not having peak period on two- row impermeable submerged breakwater's lee side.

On Comparison between 2-D and 3-D Numerical Models used to Analyze the Wave Field around a Permeable Submerged Breakwater (투과성잠제 주변의 파동장 해석을 위한 2-D 및 3-D 수치계산의 비교)

  • Hur, Dong-Soo;Choi, Dong-Seok;Lee, Woo-Dong;Yeom, Gyeong-Seon
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.20 no.4
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    • pp.363-371
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    • 2008
  • The aim of this study is to compare the numerical results obtained by 2-D and 3-D models which are used to examine the wave field around a permeable submerged breakwater. At first, the numerical model, which is able to consider the flow through a porous medium with inertial, laminar and turbulent resistance terms and determine the eddy viscosity with LES turbulent model, is used and validated by comparing with existing experimental data. And then, the numerical test on the wave field around a permeable submerged breakwater is performed. It is revealed from the numerical results that, at the onshore side of the submerged breakwater, the wave height by 2-D analysis is higher than that by 3-D analysis. Also, the time-averaged mean flow around a submerged breakwater is discussed in detail.

Effect of the Slope Gradient of a Permeable Submerged Breakwater on Wave Field around It (투과성잠제의 비탈면경사가 주변 파동장에 미치는 영향)

  • Hur, Dong Soo;Choi, Dong Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.2B
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    • pp.249-259
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    • 2008
  • The present paper studies the effect of the slope gradient of a fully permeable submerged breakwater using a newly developed numerical model that is able to consider the flow through a porous midium with inertial, laminar and turbulent resistance terms, i.e. simulate directly WAve-Structure (submerged breakwater)-Sand seabed interaction and can determine the eddy viscosity with LES turbulence model in 2-Dimensional wave field (LES-WASS-2D). The developed model was validated through the comparison with an existing experimental data, and further used for various numerical experiments in oder to investigate the complicated hydrodynamics on the varying slope gradient of permeable submerged breakwater. We found an acceptable phenomenon, as we expect intuitively, that reflection and transmission coefficients decrease simultaneously as slope gradient decrease. In addition, the breaking point, the circulation flow and mean vorticity around a submerged breakwater are throughly discussed.

Study on the Basic Design Method of Submerged Breakwater Composed of Double-Layer Permeable Blocks (투수성 블록 2층적으로 구성된 잠제의 기본설계법 연구)

  • Lee, Dal Soo;Oh, Sang-Ho;Park, Yi-Dong;Jeong, Weon-Mu
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.3
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    • pp.172-180
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    • 2013
  • The focus of this study is to provide a method for determining the dimension of a submerged breakwater satisfying the target transmission performance or predicting the transmission coefficient of a given structure. This method was developed based on data analysis of the physical experiment that was carried out by using the submerged breakwater composed of double-layer permeable blocks. Two different armor blocks of Tetrapod and Triangular Pyramid Block were used in the experiment. The parameter $K_Th_b/h$ was introduced in the analysis of the measurement data. By using the linear regression line deduced from the analysis of the experimental data, it was possible to readily predict the wave transmission coefficient irrespective different water depths at the crest of the submerged breakwater, under the condition of significant decrease in transmitted wave height due to the submerged breakwater. This method can be effectively utilized for estimating the necessary number of blocks used for the submerged breakwater as well as comparing the transmission characteristics of the submerged breakwater according to use of different armor blocks.