• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.8-15
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• 2005

Wave energy has been considered to be one of the most promising energy resources for the future, as it is pollution-free and an abundant natural resource. However, since it has drawbacks of non-stationary energy density, it is necessary to change the wave energy into a simple concentrated energy. Progressive waves in a coastal area can be amplified, swashed, and overtopped by a wave overtopping control structure. By conserving the quantity of overflow in a reservoir, the kinetic energy of the waves can be converted to the potential energy with a hydraulic head above the mean sea level. The potential energy in the form of a hydraulic head can be utilized to produce electric power, similar to hydro-electric power generation. This study aims to find the most optimal shape of wave overtopping structure for maximum overtopping volume of sea water; for this purpose, we carried out the wave overtopping experiment in a wave tank, under both regular and irregular wave conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.663-673
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• 2021

Normally, allowable mean overtopping discharge is used as a design parameter for coastal structures. The crest elevation of a structure must ensure wave overtopping discharge within acceptable limits for structural safety and the safety of pedestrians, vehicles, operations, and so on. Some researchers have alternatively proposed using the maximum individual wave overtopping volumes as design criteria during a design storm, since these can provide a better design measure than the mean overtopping rate. This study contributes to the knowledge on maximum individual overtopping volumes in Rayleigh-distributed wave conditions. Two-dimensional physical model tests on typical rubble mound structure geometries were performed, and the new measurement method for individual overtopping was adopted. An empirical formula was proposed to predict the maximum individual overtopping volumes based on the mean overtopping rate, and the reduction effects by the armor crest width on the mean wave overtopping discharge were assessed.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.443-445
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• 2008

Determination of allowable overtopping rate for coastal structure is a key point to determine the application of background of coastal structure while considering safety and economic efficiency. Thus, the accurate estimation of overtopping rate against coastal structure is essential. In general, estimation of overtopping against the coastal structure is based on an empirical formula or hydraulic experiment. In this study, we investigate the behavior of overtopping for rubble mound coastal structure with rubble armor stone and wave dissipating block using hydraulics experiment, and domestic or foreign design standard.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.649-655
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• 2006

Waves progressing into the coastal area can be amplified, swashed and overtopped by a wave overtopping control structure, and it converts the kinetic energy of the waves to the potential energy with a hydraulic head above the mean sea level by conserving the overflow in a reservoir. Then the potential energy in the form of hydraulic head can be converted to electric power utilizing extremely low-head hydraulic turbine. This study aims to find the most optimal shape of wave overtopping structure which maximizes overtopping volume rate of sea water. Laboratory experiments for the performance evaluation of wave overtopping control structures were carried out in three dimensional wave tank, and the three dimensional structure models with planar wave concentration shapes(B/b) were manufactured into five classes, which were optimized by cross sectional parameters of the structure, ie, length of ramp(l), gradient of inclined ramp($cot{\phi}$) and freeboard height of the wave overtopping structure($h_e$) proposed by Shin and Hong(2005). The wave overtopping discharges were investigated with 20 incident wave conditions and wave directions of $0^{\circ},\;15^{\circ},\;30^{\circ}$.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.414-421
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• 2011

In determination of the crest height of a vertical structure against attacking of obliquely incident waves, most of existing studies have suggested to use the overtopping reduction factor due to incident angles. However, they have not considered the amplification of wave heights and the spatial distribution of wave overtopping. In this study, a spatial distribution of overtopping due to the amplification of wave heights along a vertical structure is investigated experimentally. It is recommended that the crest height can be determined by the same manner as that for normally incident waves up to 3 significant wave lengths from the one end of the structure. However, the rest part of the structure can be done by employing the overtopping reduction factor with considering the amplification of wave heights and the spatial distribution of wave overtopping.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.149-155
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• 2010

The existing formula for estimating the wave overtopping are mainly about the perpendicularly incident wave to the structure and wave overtopping formula for the obliquely incident wave are rare. Moreover, these formula present only the overtopping reduction factor(${\gamma}_{\beta}$) with respect to the incident wave angle rather than the spatial distribution of overtopping along the structures because the length of model is relatively too short for the wave to propagate along the structure. In this study, the wave overtopping reduction factor considering the spatial variation of wave overtopping along the vertical wall is investigated using the hydraulic model tests and the results are compared with the those of EurOtop(2007). The wave overtopping reduction factor is modified for ${\beta}$ > $45^{\circ}$ condition.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.122-130
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• 1997

Coastal diaster induced by waves and countermeasures were investigated in the viewpoint of reduction of overtopping rate with enviroment in fishing port. The reduction method of wave overtopping rate using ecosystem control structures was proposed and studied on the efficiency by hydraulic and numerical experiments. The estimation models on wave overtopping rate was proposed after comparing previous models with dimensional analysis and experimental results. Control function o fwave overtopping by use of ecosystem controlstructures was simulated and discussed with combining wave shoaling-dissipation-breaking deformation model around ecosystem control structures and newly proposed calculation model for wave overtopping rate. Feasiblilty of ecosystem control structures could be confirmed for reduction of wave overtopping and fisheries-based multipurpose development of coastal zone.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.4
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• pp.75-83
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• 2023

Apart from implementing hardware solutions like raising the crest freeboard of coastal structures to efficiently counter wave-overtopping, there is a simultaneous requirement for software-driven disaster mitigation strategies. These tactics involve the swift and accurate dissemination of wave-overtopping information to the inland regions of coastal zones, enabling the regulation of evacuation procedures and movement. In this study, a method was proposed to estimate wave-overtopping by utilizing the temporal variation of wave heights exceeding the structure's crown level, with the aim of developing an on-site wave measurement system for providing wave-overtopping information in the field. Laboratory model experiments were conducted on vertical seawall structures to measure wave-overtopping volumes and wave runup heights under different wave conditions and structural freeboard variations. By assuming that the velocity of water inundation on the top of the structure during wave-overtopping events is equivalent to the long-wave velocity, an overtopping discharge coefficient was introduced. This coefficient was utilized to estimate the rate of wave-overtopping based on the temporal changes in wave runup heights measured at the top of the structure. Upon reasonably calculating the overtopping discharge coefficient, it was verified that the estimation of wave-overtopping could be achieved solely based on the wave runup heights.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.1-5
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• 2002

In the past, ports have been mainly developed in natural harbors but nowadays ports are built wherever they can be economically justified. Therefore, construction of breakwater in area that establishment of structure is disadvantageous is risen according to the change of conditions to the location for ports. In case of building gravity breakwater in such point, need that plane shapes of more reasonable section permitting wave overtopping is necessary. One of the earliest methods for solving unsteady incompressible flow including free surfaces is the MAC(Marker And Cell) method by Harlow and Welch (1965). Recently. VOF(Volume Of Fluid) method to improve several drawbacks of MAC method is suggested by Hirt and Nichols(1981) and utilized extensively in fields of hydrodynamics. Wave overtopping phenomenon is simulated including wave breaking for permeable breakwater by numerical analysis and investigated features of wave overtopping behind structure using VOF method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.228-234
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• 2012

Two-dimensional hydraulic experiments for wave overtopping under non-breaking wave condition are conducted. The wave overtopping formula for vertical structure is suggested and the results are compared with EurOtop (2007). The relative water depth coefficient (${\gamma}_{kh}$) shows that almost the same coefficient is obtained for certain range (kh > 1.55) regardless of relative water depth, that is, although the relative water depth becomes larger, the relative water depth coefficient is almost same. When the wave steepness becomes larger the wave steepness coefficient decreases. The overtopping formula are expressed by relative freeboard(R) and non-dimensional wave overtopping rate(Q) and this formula has the form of exponential function. In this formula, the effects of wave period on wave overtopping are quantitatively investigated and suggested through the relative water depth coefficient(${\gamma}_{kh}$) and wave steepness coefficient(${\gamma}_s$).