• 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.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.3
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• pp.105-115
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• 2024

In coastal structure design incorporating revetments, the assessment of wave overtopping discharge relies on hydraulic model experiments. Numerous empirical formulas have been developed to predict overtopping discharge based on quantitative data from these experiments. Typically, for revetment structures aimed at mitigating wave overtopping, crest height is determined by considering the maximum amplitude of the design wave, resulting in a relatively high freeboard compared to wave heights. However, achieving complete prevention of all wave overtopping would require the crown wall to have substantial crest heights, rendering it economically impractical. Therefore, the concept of limiting discharge has been introduced in the design of revetment structures, aiming to restrict wave overtopping discharge to an acceptable level. Consequently, many coastal structures in real-world settings feature relatively lower freeboard heights than incident wave heights. This study investigated wave overtopping discharge on rubble-mound breakwaters with relatively low freeboard heights through hydraulic model experiments. Furthermore, it conducted a comparative analysis of the predictive capabilities of existing empirical formulas for estimating overtopping discharge using experimental data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.1-6
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• 2016

The effect of reducing wave overtopping by use of the wave return wall was quantitatively analyzed based on physical experiments. The overtopping discharge for the arc seawall and the inclined seawall was measured and compared with the predictive formula that estimates reduction of overtopping by the wave return wall. When the overtopping discharge was relatively large ($q/{\sqrt{gH^3_s}}>10^{-3}$), the agreement in terms of overtopping reduction rate was fairly good between the prediction and the measurement. For the condition of smaller overtopping than the above criterion, however, the discrepancy was large between the predicted and measured result. In this context, it is required to develop a better formula for estimating reduction of wave overtopping by the wave return wall.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.947-964
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• 2014

Rubble mound breakwaters protect the coastal line against severe erosion caused by wave action. This study examined the performance of different sizes and properties (i.e. height of vertical wall and tetrapod size) of rubble mound breakwaters on reducing the overtopping discharge. The physical model used in this study was derived based on an actual rubble mound in Busan Yacht Harbor. This research attempts to fill the gap in practical knowledge on the combined effect of the armor roughness and vertical wall on wave overtopping in rubble mound breakwaters. The main governing parameters used in this study were the vertical wall height, variation of the tetrapod weights, initial water level elevation, and the volume of overtopping under constant wave properties. The experimental results showed that the roughness factor differed according to the tetrapod size. Furthermore, the overtopping discharge with no vertical wall was similar to that with relatively short vertical walls (${\gamma}_v=1$). Therefore, the experimental results highlight the importance of the height of the vertical wall in reducing overtopping discharge. Moreover, a large tetrapod size may allow coastal engineers to choose a shorter vertical wall to save cost, while obtaining better performance.

• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.192-199
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• 2024

Wave overtopping is a significant natural hazard that occurs in coastal areas, primarily driven by high waves, particularly those generated during typhoons, which can cause coastal flooding. The development of residential and commercial areas along the coast, driven by increasing social and economic demands, has led to a concentration of people and assets in these vulnerable areas. This, coupled with long-term sea level rise and an increase in typhoon frequency, has heightened the risk of coastal hazards. Traditionally, the evaluation of wave overtopping volumes has relied on directly measuring the collected volume of water that exceeds the crest height of structures through hydraulic model experiments. These experiments are averaged over a specific measurement period. However, in this study, we propose a new method for estimating individual wave overtopping volumes. We utilize the temporal variation of wave overtopping heights to develop an observation system that can quantitatively assess wave overtopping volumes in actual coastal areas. To test our method, we conducted hydraulic model experiments on rubble mound breakwaters, which are commonly installed along the Korean coast. We introduce wave overtopping discharge coefficients, assuming that the inundation velocity from the structure's crest is the long-wave velocity. We then predict overtopping volumes based on wave overtopping heights and compare and review the results with experimental data. The findings of our study confirm the feasibility of estimating wave overtopping volumes by applying the overtopping discharge coefficients derived in this study to wave overtopping heights.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.4
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• pp.273-278
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• 2009

Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor for collecting the overtopping waves and converting the water pressure head into electric power through the hydro turbines installed in the vertical duct which is fixed in the sea bed. The numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. Several incident wave conditions and shape parameters of the overtopping device are calculated. The straight line type and parabolic type of the sloping arm are compared in the optimal designing investigation of the overtopping characteristics and discharge for OWEC device. The numerical results demonstrate that the parabolic sloping arm is available for wave running up and the overtopping discharge increasing.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.1-13
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• 2015

Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and landward-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. In this paper, combined wave overtopping and storm surge overflow of a levee embankment strengthened with high performance turf reinforcement mat (HPTRM) system was studied in a purely Lagrangian and meshless approach, two-dimensional smoothed particle hydrodynamics (SPH) model. After the SPH model is calibrated with full-scale overtopping test results, the overtopping discharge, flow thickness, flow velocity, average overtopping velocity, shear stress, and soil erosion rate are calculated. New equations are developed for average overtopping discharge. The shear stresses on landward-side slope are calculated and the characteristics of soil loss are given. Equations are also provided to estimate soil loss rate. The range of the application of these equations is discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.372-382
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• 2006

Most of the conventional breakwaters impermeable breakwaters which block seawater exchange between the outside and inside of the harbors. The blocking of seawater exchange may cause pollution of water in harbors. To solve the water pollution problem, various kinds of seawater exchange breakwaters have been proposed. Their types can be classified into the current type which uses tidal current, and the overtopping type which uses the wave energy. The overtopping type breakwaters require a discharge coefficient to calculate the rate of overtopping into the harbor. The present study is to compute the rate of overtopping with introduction of a correct discharge coefficient and to evaluate the effect of the overtopping type breakwater on the water qualify inside a harbor. The rate of overtopping was computed by using Forchheimer formula with time dependent mild-slope equation for various wave conditions. The formula has been generally used to calculate the overflow discharge in steady state river flows. The discharge coefficient, which is the key parameter of the calculation, was determined by a series of hydraulic model tests. The present scheme was applied to the seawater exchange section of the western breakwater of Jeju New Harbor's and the efficiency of that section was examined. The calculated results showed that the rate of overtopping into the harbor reached about $27.5m^3/s$ in the wave condition (wave height 3.7 m, wave period 8.5s, and wave direction NNW).

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.1-6
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• 2009

An Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor used for collecting overtopping waves and converting the water pressure head into electric power through hydro turbines installed in a vertical duct affixed to the sea bed. A numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. The Reynolds Averaged Navier-Stokes equation and two-phase VOF model are utilized to generate the 2D numerical linear propagating waves, which are validated by the overtopping experiment results. Calculations are made for several incident wave conditions and shape parameters for the overtopping device. Both the incident wave periods and heights have evident effects on the overtopping performance of the OWEC device. The computational analysis demonstrates that the present overtopping device is more compatible with longer incident wave periods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.3
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• pp.49-56
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• 2023

The allowable mean overtopping discharge is used as a design parameter for coastal structures. The crest elevation of coastal structures should ensure the wave overtopping discharge within acceptable limits for structural safety and the safety of pedestrians, vehicles, operations, and so on. In this study, two-dimensional physical model tests on typical rubble-mound structure geometries were performed and the the mean wave overtopping discharges under various water depth and wave conditions were measrued. The various test conditions were applied to the tests with the change of the wave steepness, relative freeboard and relative wave height. An empirical formula from the experimental data was proposed to predict the mean wave overtopping volumes.