• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.2
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• pp.31-39
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• 1990

Deck wetness phonomena has long been considered as one of the factors that degrade the performance of a ship in waves. In rough weather, the frequent shipping of water may give rise to the capsizing of the ship. Therefore an appropriate above water bow design is an improtant assert to a ship of which successful performance in rough weather is a prerequisite such as a warship. In this paper the experimental technique for estimation of deck wetness frequency is presented. The results of the model tests are compared with those of calculation using Ochi's formula. Finally the applicability of Ochi's formula is discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.619-633
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• 1994

A wave deformation model for general purpose combined refraction, diffraction, and breaking is developed in the shallow water. A parabolic approximation equation considered a higher order diffraction term is derived from the previous mild slope equation. A wave energy dissipation term due to bottom friction and breaking is introduced from the turbulence model. The Crank-Nicoloson implicit scheme is used in the numerical calculation, then the solutions are compared with the various hydraulic experiment data in the circular, the elliptic shoal, and the surf zone. The wave height decay in the surf zone is sensitively affected by the incident wave steepness, and the wave height variation around the elliptic shoal is well explained by the non-linear dispersion relation and the wave energy dissipation term. The model is also applied to a field coastal area and reasonable results are obtained.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.5
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• pp.510-521
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• 2008

In the study, experiments are performed in the interaction region combined with wave and current to investigate the characteristics of local scour around submarine pipelines. Wave generator and current generator are used for the experiments and two current directions were used; co-direction and counter direction to the wave. The local scour depths around the pipeline are obtained according to the various pipe diameters(D), wave periods(T), wave heights(H), and current velocities(V). The experiments show that the maximum equilibrium local scour depth increases with pipe diameter, wave period, wave height, and current velocity. Using the experimental results, the correlations of scour depth and parameters such as Shields parameter($\theta$), Froude number(Fr), period parameter, Keulegan-Carpenter number(KC), Ursell number($U_R$), modified Ursell number($U_{RP}$) and ratio of velocities($U_{c}/(U_{c}+U_{m})$) are analyzed. In the interaction region combined with waves and currents, Froude number and Shields parameter are found the main parameters to cause the local scour around the submarine pipelines and this means that current governs the scour within any limits of the currents.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.819-830
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• 2016

Hydrodynamic characteristics of wave propagation through density stratification have not been identified in details. So this study conducted a numerical simulation using LES-WASS-3D ver. 2.0 for analysis of density current due to water temperature and salinity in order to analyze hydraulic characteristics under wave action in a two-layer density stratified fluid. For the validity and effectiveness of numerical wave tank used, it was compared and analyzed with the experiment to show waveform based on $3^{rd}$-order Stoke wave theory at the internal of a density stratification. Using the results obtained from numerical simulation, the surface and internal wave heights are reduced as the wave propagates in a two-layer density stratified water. And the surface or internal wave attenuation became more serious as the vorticities were increased by the velocity difference of wave propagation due to the upper-lower density difference around the interface of a density stratification. As well, the surface and internal wave attenuations became more serious with higher density difference and depth ratio between upper and lower layers when the wave propagates through a density stratification.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3074-3080
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• 2013

Amplification of wave height at concave corner was investigated by three dimensional hydraulic tests. A typical rubble mound structure was tested with two-layer Tetrapod and the slope of 1:1.5. The irregular waves with Bretschneider-Mitsuyasu spectrum were applied to the tests. The center angles of concave corner were 120 degree, 140 degree and 160 degree. According to the test results, the maximum wave height amplification ratio at concave corner was about 1.5 times of incident wave height among the all test conditions, and the W-shaped wave height distribution was shown.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.116-122
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• 2015

A simulation is applied to evaluate sea surface observations such as wave heights and surface currents by using a microwave Doppler radar. It is reported that the microwave irradiation width on the sea surface and Fourier transform time taken to sample data for frequency analysis affect Doppler spectra. To investigate the influences by these parameters, Doppler spectra are simulated with various numerical sea surface waves with currents. From the results, in the case of the microwave irradiation width is five times smaller than the wavelength of the sea surface wave, and the Fourier transform time is also five times shorter than the period of the sea surface wave, there is a possibility to measure wave heights accurately with a Doppler radar. In addition, relative surface currents can be estimated by analysis of long Fourier transform time. The simulation results showed the appropriate observing conditions with a microwave Doppler radar.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.1-8
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• 2013

This review article summarizes metal-assisted chemical etching (MAC etch or MACE), an anisotropic etching method for Si, and describes principles, main factors, and recent achievements in literature. In 1990, it was discovered that, with metal catalyst on surface and $H_2O_2$/HF as etchant, Si substrate can be etched anisotropically, in even in solution. In contrast to high-cost vacuum-based dry etching methods, MAC etch enables to fabricate a variety of high aspect ratio nanostructures through wet etching process.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.2
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• pp.98-105
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• 2005

A new type breakwater is developed for small scale harbors and fishing ports with low design wave and soft ground. The structure of the developed breakwater is similar to the soldier pile used in soil excavation. Structural performance of the new type breakwater can not be accurately evaluated by numerical analysis due to nonlinearity of joints between piles and honelasticity of soil support. Therefore, this paper investigates the structural performance of the breakwater with experimental method and compares the results with numerical analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.169-179
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• 2017

In this study, we applied the wave generation method by relaxation method to the SWASH model, which is a non - hydrostatic numerical model, for stable and accurate wave generation of linear and nonlinear waves. To validate the relaxation wave generation method, we were simulated various wave, including the linear wave and nonliner wave and compared with analytical solution. As a result, the incident wave was successfully generated and propagated in all cases from Stokes waves to cnoidal wave. Also, we were confirmed that the wave height and the waveform were in good agreement with the analytical solution.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.2
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• pp.157-163
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• 1994

An experimental study of deep-water breaking waves is performed by nonlinear wave evolution as well as superposition of different wave frequencies. Two-dimensional and three-dimensional wave instabilities and breakings are observed in nonlinear wave evolution. The wave energy evolves with almost the same initial wave energy before breaking but decreases significantly after breaking process. Large spilling and plunging waves are generated near e expected breaking location by means of faster waves overtaking slow waves at a certain point. More energy loss in vigorous plunging breakers is observed through breaking process.