• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.359-368
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• 2010

This paper describes the generation and propagation of internal solitary wave in a two-layer fluid system by numerical analysis. Characteristics of interfacial soliton such as wave type, wave height, wave celerity are investigated numerically with respect to an extent of initial disturbance, fluid thicknesses of the two fluids and etc. The difference between the internal wave propagation on sloping beach and flat bottom was also examined. Laboratory experiments were conducted in the wave flume and compared with the results of numerical computation for verification.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.46-53
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• 2002

In the study, the interaction characteristics among incident waves, run-up and internal waterlevel at core layer of breakwaters were investigated. The effect of core materials on the internal waterlevel characteristics are also discussed using the results with both regular and irregular wave tests. The main results obtained are as follows; The higher internal waterleve was observed under the permeable breakwater with core layer of the lower permeability than with the higher one. And, the internal waterlevl decreased as far as the distance from the toe. In the irregular wave test, the grouping characteristics of incident waves make large fluctuation of the waterlevel. Especially, breakwaters internal waterlevel appeared to affect the hydraulic characteristics on slope.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.37-43
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• 2009

Fluctuations in the ocean are closely related with the underwater acoustic propagation. Internal waves are generated by fluctuation of isopycnal layer in the upper part of the stratified ocean, which are propagated from offshore to coastal area. Physical characteristics of the internal waves existed in the East Sea were derived from the five field experimental data and the ocean monitoring buoy nearshore the mid-east coast of Korea. The dominant periods are appeared in the near-inertial period about $17{\sim}20hours$ and the short period about a few minutes. The wavelengths of them are $10{\sim}50km$ and $300{\sim}1000m$, and the phase speeds are $20{\sim}100cm/s$ and $30{\sim}70cm/s$, respectively The maximum amplitudes are about $20{\sim}25m$. Under the environment of short depression internal wave propagation, the variations of transmission loss field were investigated using an range-dependent acoustic transmission loss model(RAM). The result shows that the large irregular variations of transmission loss caused by progressing the internal wave from offshore toward coast.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.18-23
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• 2008

This study investigated interactions between the internal-external wave field of a permeable coastal structure consisting of rubble. The study examined the application criteria of an existing numerical model (CADMAS-SURF V.4.0) and proposed a modified method to provide reasonable results. In particular, the study focused on and emphasized the water surface profiles in front of a structure, wave run-up/run-down on a slope, and internal water level fluctuations due to the drag coefficient and porosity of a rubble mound structure. In conclusion, the result show that when the vertical fluctuations of the internal water levels in permeable coastal structures exhibited high-quality representation. Sane responses can be seen for wave run-up/run-down characteristics on its slopes.

• Bulletin of the Korean Mathematical Society
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• v.54 no.4
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• pp.1457-1470
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• 2017

In this paper, we consider the stabilization of the viscoelastic wave equation with variable coefficients in a bounded domain with smooth boundary, subject to linear dissipative internal feedback with a delay. Our stabilization result is mainly based on the use of the Riemannian geometry methods and Lyapunov functional techniques.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.361-366
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• 2013

An imaging technique to visualize the internal defects in a plate-type nuclear fuel specimen was developed by using an active optical interferometer for a nondestructive quality inspection. A periodic thermal wave having a sinusoidal intensity pattern induced a periodical strain variation for the specimen. The varying strain image was acquired using an optical laser interferometer. The strain distribution over the internal defects will be distorted in an acquired strain image because a part of the thermal wave will be reflected from these defects during propagation. In this paper, internal defects were efficiently visualized by sequentially accumulating the extracted defect components. The experimental results confirmed that the developed visualization system can be a valuable tool to detect the internal defects in plate-type nuclear fuel.

• Proceedings of the KSRS Conference
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• v.2
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• pp.943-945
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• 2006

The experiment on study of ambient nose generated by large-amplitude internal waves in Luzon Strait is analyzed. Simultaneous observations of internal waves and characteristics of ambient noise generated by them were carried out. Fast 50-m solitary internal wave propagated to the northwest direction with speed more than 3 m/s was observed. It was revealed an enhancing of ambient noise level (at frequency range 1-2 kHz) at a time of passing the face side of the solitary wave.

• Journal of Ocean Engineering and Technology
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• v.16 no.5
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• pp.34-40
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• 2002

A numerical model has been developed for the permeable coastal structures to simulate hydraulic characteristics on the permeable slopes, which interact with internal four field the structures. The model includes hydraulics in the porous medium. Numerical model was calibrated using hydraulic model experiments performed in 2-D wave flume in the Institute of Ocean Hydraulics in PKNU. Better aggrements were obtained with the model which employed inertia resistance term than with the conventional model, PBREAK.

• Journal of the Korean Wood Science and Technology
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• v.31 no.6
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• pp.45-54
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• 2003

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.36-44
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• 2021

Numerical analysis was performed on the shock wave-boundary layer interaction generated in the internal flow path of the curved interstage of the scramjet engine flight test vehicle. For numerical analysis, the turbulence model k-ω SST was used in the compressibility Raynolds Averaged Navier Stokes(RANS) equation. Representatively, the separation bubbles on the upper wall of the nozzle, the interaction between the concave shock wave and the boundary layer, and the shock wave-shock wave interaction at the edge were captured. The analysis result visualizes the shock wave-boundary layer interaction of the curved internal flow path to enhance understanding and suggest design considerations.