• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.363-368
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• 2017

The tsunami flood the coastal cities and damage the land structures. The study on wave pressure and force on land structures is one of the important factors in designing the stability of inland structures. In this study, two - dimensional wave flume tests on the horizontal wave force and pressure of tsunamis on a simplified box-type structure was conducted. Vertical distribution and wave power of horizontal wave pressure over time were measured by pressure sensors and force transducer. Also, those were measured from the different wave breaking types. The vertical distribution of horizontal wave pressure was uniform at the moment when the horizontal wave force to the structure was maximum under the breaking wave condition. A surf similarity parameter was employed in order to figure out the relationship between the maximum horizontal wave force on the structure as a function of various incident wave conditions. As a result, the non - dimensionalized horizontal wave force tends to decrease exponentially as the surf similarity parameter increases.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.179-188
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• 2012

Performance analyses of vertical breakwaters were conducted for fictitiously designed breakwaters for various water depths to analyze the influence of climate change on the structures. The performance-based design method considering sea level rise and wave height increase due to climate change was used for the performance analysis. One of the problems of the performance-based design method is the large calculation time of wave transformation. To overcome this problem, the SWAN model combined with artificial neural network was used. The significant wave height and principal wave direction at the breakwater site are quickly calculated by using a trained neural network with inputs of deepwater significant wave height and principal wave direction, and tidal level. In general, structural stability becomes low due to climate change impacts, but the trend of stability is different depending on water depth. Outside surf zone, the influence of wave height increase becomes more significant, while that of sea level rise becomes negligible, as water depth increases. Inside surf zone, the influence of both wave height increase and sea level rise diminishes as water depth decreases, but the influence of wave height increase is greater than that of sea level rise. Reinforcement and maintenance policies for vertical breakwaters should be established with consideration of these results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.95-105
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• 2020

In this study, using the CADMAS-SURF model, the characteristics of the wave pressures and the wave forces were analyzed according to the installation position of the parapet on top of the caisson, and the stability evaluation was carried out using estimated wave forces for the design wave condition. Numerical results show that adopting the rear-parapet reduces the front maximum wave pressures and wave forces, and the maximum wave pressure acting on the rear-parapet increases slightly compared to the front parapet, but the wave force acting on the rear-parapet has little effect on the stability of the breakwater due to the phase difference with the wave force acting on the front of the breakwater. In addition, impulsive wave pressures did not occur, as Yamamoto et al. (2013) pointed out the problem of the rear-parapet breakwater. As a result of the stability against sliding and overturning, it was estimated that the target safety factor of 1.2 could be secured by the self-weight of 13% less than the case of the front parapet. At this time, the maximum ground pressure was also reduced by 30%, and the applicability of the rear-parapet structure to the actual site was evaluated as high.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.373-376
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• 2006

In general, a method for generating irregular wave by combination of component waves obtained from linear wave theory is widely used. In these method, however, mean water surface elevation is rising from time to time because of nonlinear effect of wave. In this study, for the rising problem of mean water surface elevation and stabilization of calculation from time to time, mass transport velocity for horizontal velocity at wave source position is considered. The rising problem of mean water surface elevation is checked by comparing calculated wave profile from numerical technique proposed in this study with target wave profile at wave source position in numerical wave tank by using CADMAS-SURF code. And, by generating irregular wave, the validity of wave overtopping rate estimated from this numerical analysis is discussed by comparing computed results with measured results in hydraulic model experiments for vertical seawall located on a sloping sea bottom. As a results, the computations are validated against the previously experimental results by hydraulic model test and numerical results of this study and a good agreement is observed. Therefore, numerical technique of this study is a powerful tool for estimating wave overtopping rate over the crest of coastal structure.

• Water for future
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• v.27 no.2
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• pp.73-83
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• 1994

The unproper development of the nearshore zone can enhance the diffusion of pollutant in the nearshore zone resulting in unbalanced sediment budget of beach which causes alteration of beach topography. Therefore, it is required to predict the effects of the envirnmental change quantitatively. In this paper, the depth-averaged and time-averaged energy balance equation is selected to acount for the wave transformation such as refraction, shoaling effect, the surf zone energy disipation, wave breaking index and bore, due to wave breaking in the shore region.(Numerical solutions are obtained by a finite difference method, ADI and Upwind. For the calculation of the wave-induced current, the unsteady nonlinear depth-averaged and time-averaged governing equation is derived based on the continuity and momentum equation for imcompressible fluid.) Numerical solutions are obtained by finite difference method considering influences of factors such as lateral mixing coefficient, bed shear stress, wave direction angle, wave steepness, wave period and bottom slope. The model is applied to the computation of wave transformation, wave-induced current and variation of mean water leel on a uniformly sloping beach.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.421-428
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• The Journal of Korean Association of Computer Education
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• v.8 no.2
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• pp.41-51
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• 2005

Although distance education system based on WBI theory has already been generalized in domestic universities and some private academical institutes, the use of the system in the real fields of schools is in the early stage now. In this paper, we develop a model of English learning system for middle school students and improve students' learning methods through the system. The system also makes students study all the learning topics which they choose in the system freely and repeatedly. It was applied to the middle school students. The analysis of the application showed the following results. First, it was very effective for students to achieve the learning objectives of the course of English. Second, the system made students improve their abilities to study English and also increase their abilities to surf the Internet and glean useful information. Third, the system made it possible for students to accomplish individual learning.

• 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 Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.179-186
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Pohang Old Harbor and Pohang New Port, etc. due to construction of New Port in Youngil Bay. This type of trial might be a milestone for port development in macroscale, where the induced impact analysis in the existing port due to the developemnt could be easily neglected.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.159-166
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• 2004

The beach, a margin between the sea and the land, is an extremely dynamic zone, for it is here that the motion of the sea interacts with the sediment, rock of the land or the artificial barriers. In order to prohibit or retard erosions due to the extreme Typhoon or storm induced waves, man has constructed these of temporary or more permanent nature, but they caused problems of other erosions from the secondary effect of them and a bad influence on the seascape. In considering the energy available to accelerate sediment transport and erosion in the surf zone, where the waves are broken, and offshore beyond the breaker line, the wave height and the wave period should be taken account. Hence, we tried to present an applicability of the submerged artificial Bio-reefs analyzing waves by a numerical model such that they could reduce the wave power without the secondary effect and restoration of marine ecologies. A new technique of beach preservation is by artificial reefs with artificial and/or natural kelps or sea plants. By engineering the geometry of the nearshore reef, the wave attenuation ability of the feature can be optimized Higher, wider and longer reefs provide the greatest barrier against wave energy but material volumes, navigation hazards, placement methods and other factors require engineering considerations for the overall design of the nearshore reefs.