• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.286-304
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• 2017

In this study, we proposed a new-type of circular perforated caisson breakwater consisting of a bundle of latticed blocks that can be applied to a small port such as a fishing port, and numerically investigated the hydraulic characteristics of the breakwater. The numerical method used in this study is OLAFOAM which newly added wave generation module, porous media analysis module and reflected wave control module based on OpenFOAM that is open source CFD software published under the GPL license. To investigate the applicability of OLAFOAM, the variations of wave pressure acting on the three-dimensional slit caisson were compared to the previous experimental results under the regular wave conditions, and then the performance for irregular waves was examined from the reproducibility of the target irregular waves and frequency spectrum analysis. As a result, a series of numerical simulations for the new-type of circular perforated caisson breakwaters, which is similar to slit caisson breakwater, was carried out under the irregular wave actions. The hydraulic characteristics of the breakwater such as wave overtopping, reflection, and wave pressure distribution were carefully investigated respect to the significant wave height and period, the wave chamber width, and the interconnectivity between them. The numerical results revealed that the wave pressure acting on the new-type of circular perforated caisson breakwaters was considerably smaller than the result of the impermeable vertical wall computed by the Goda equation. Also, the reflection of the new-type caisson breakwater was similar to the variation range of the reflection coefficient of the existing slit caisson breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.482-488
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• 2011

Seadike is a coastal structure constructed in the rear region of the foreshore to maximize its usability by preventing direct effect of wave. The expected construction field is determined under the design wave and tidal condition where minor wave overtopping is anticipated. Thus, the location of seadike is generally fixed at the highest site of the surrounding area with seadike crest height controlling the permissible range of wave overtopping volume. But a lot of times, frontal sand beach of the seadike continuously deforms due to incident waves, resulting failure in maintaining its initial slope. The erosion and deposition of the seadike front cause changes in the crest height and volume of wave overtopping and decrease in the setting depth of the seadike, which endangers seadike region as a result. In this study, the relation of local scouring and setting depth of the seadike front in the run-up region is examined by using 2D hydraulic model tests and numerical simulations by modified SBEACH model. As a result, the study learned that if appropriate boundary condition is applied to the modified SBEACH model, it is possible to create practical estimations on the local scouring at the seadike foot when erosive waves flow into the region.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.35-41
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• 2007

In general, coastal damage is mostly occurred by the action of complex factors, like severe water waves. If the maximum storm surge height combines with high tide, severe water waves will overflow coastal structures. Consequently, it can be the cause of lost lives and severe property damage. In this study, using the numerical model, the storm surge was simulated to examine its fluctuation characteristics at the coast in front of Noksan industrial complex, Korea. Moreover, the shallow water wave is estimated by applying wind field, design water level considering storm surge height for typhoon Maemi to SWAN model. Under the condition of shallow water wave, obtained by the SWAN model, the wave overtopping rate for the dike in front of Noksan industrial complex is calculated a hydraulic model test. Finally, based on the calculated wave-overtopping rate, the inundation regime for Noksan industrial complex was predicted. And, numerically predicted inundation regimes and depths are compared with results in a field survey, and the results agree fairly well. Therefore, the inundation modelthis study is a useful tool for predicting inundation regime, due to the coastal flood of severe water wave.

• The Journal of the Korea Contents Association
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• v.7 no.9
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• pp.212-219
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• 2007

This study were developed with the preventive structures of shore erosion using the seawater circulation system in wave dissipation block of the natural affinity. The shore protection structures were established to excellent by the hydraulic model experiment on reflectivity and stability and wave overtopping in comparison with existing other structures. These structures, in order to analyzes also as the shore protection and the erosion preventive, were examined with the field applications of performance and the capacity of prevention, respectively, from field construction of the pending positions. As the result, the structures were ensured with the applications and the efficiency as the shore protection structure of erosion preventive by certifying accumulated sediment deposits in the field measurement and monitoring.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.403-408
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• 2019

In general, the caisson having the perforated wall is used to for the purpose of reducing the wave reflection and wave overtopping. In this study, the hydraulic characteristics (reflection coefficient) of the perforated wall caisson chamber filled with aggregates (rocks) were investigated with hydraulic model tests. When the perforated wall chambers were filled with aggregates, the reflection coefficients would increase. However, it was confirmed that the rock filling method into the perforated wall chamber could secure the stability of the structures and satisfy the hydraulic characteristics at a certain level.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.34-39
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• 2005

All of the design criterion are not only formulated by an internal study, concerning the design of maritime structures, but also by the guarantee that internal design technology is essential, at least according to theoretical and experimental studies. Furthermore, the basic data, which is necessary for the development of a more stable design of breakwater structures, should be ensured, according to current research and analysis of damage created by water waves. According to the necessity to solve the problems that occur in the design and construction of ocean structures, until now, it is recognized that the hydraulic experiments are important. This paper provides the design of structures to decrease the energy created by waves. Suggestions to make contributions to the development of ocean/fisheries technology are also discussed. It is better to use S-type coastal structures/breakwaters than to use uniform type breakwaters, concerning stability, reflection, and overtopping.

• 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.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.7-12
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• 2008

The present study numerically investigates the effect of the shape of absorbing revetment on wave overtopping rate under regular and irregular incident waves. At first, the numerical model developed by Hur and Choi(2008), which considers the flow through a porous medium with inertial, laminar and turbulent resistance terms, directly simulates Wave-Structure-Sandy seabed interaction and can determine the eddy viscosity with LES turbulent model in 2-Dimensional wave field (LES-WASS-2D), is validated when compared to experimental data. Numerical simulations are then performed to examine the effect of the shape of absorbing revetment and incident wave conditions on wave overtopping rate. The numerical result shows that the wave overtopping rate decreases with the slope gradient of absorbing revetment under both regular and irregular waves. In addition, the effects of mean grain size and porosity of absorbing revetment, incident wave period and crest height on wave overtopping rate are discussed.

• Journal of Ocean Engineering and Technology
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• v.18 no.4 s.59
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• pp.23-32
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• 2004

Specially shaped concrete blocks are used for the armor layer of rubble structure for breakers, seawalls, or other shore protection work. In this study, the hydraulic characteristics of the Modified-Tribar(MTB), which addresses the shortcomings of the Arch-Tribar, and the most widely used Tetrapod(TTP) in Korea are examined through hydraulic model tests. The MTB are much more stable than the TTP, as shown through the stability model tests under non-breaking and non-overtopping condition. The value of the stability coefficient(KD) was obtained at around 30. The model tests show that the TTP random two layers and MTB uniform 1.5 layers have similar effects, but the MTB one layer shows slightly low effects in dissipating wave energy. The TTP random two layer model is the most effective in reducing wave overtopping rate, under overtopping condition, while the MTB uniform one layer and the MTB uniform 1.5 layer models follow respectively.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.643-654
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• 2018

In order to generate the stable tsunami in a numerical wave tank, a two-dimensional numerical model, LES-WASS-2D has been introduced the non-reflected wave generation system for various tsunami waveforms. And then, comparing to existing experimental results it is revealed that computed results of the LES-WASS-2D are in good agreement with the experimental results on spatial and temporal tsunami waveforms in the vicinity of a seawall. It is shown that the applied model in this study is applicable to the numerical simulations on tsunami overtopping and inundation. Using the numerical results, the characteristics of overtopping and inundation on a seawall are also discussed with volume ratio of tsunami and relative tsunami height. The wider the tsunami waveform, tsunami overtopping quantity and inundation distances are linearly increased. Therefore, the hydraulic characteristics is highly likely to be underestimated against the real tsunami if the solitary wave of approximation theory is applied for the overtopping/inundation simulations due to a tsunami.