• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.5
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• pp.300-313
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• 2014

Most analytical solutions for wave-induced soil response have been mainly developed to investigate the influence of the progressive and standing waves on the seabed response in an infinite seabed. This paper presents a new analytical solution to the governing equations considering the wave-induced soil response for the partial standing wave fields with arbitrary reflectivity in a porous seabed of finite thickness, using the effective stress based on Biot's theory (Biot, 1941) and elastic foundation coupled with linear wave theory. The newly developed solution for wave-seabed interaction in seabed of finite depth has wide applicability as an analytical solutions because it can be easily extended to the previous analytical solutions by varying water depth and reflection ratio. For more realistic wave field, the partial standing waves caused by the breakwaters with arbitrary reflectivity are considered. The analytical solutions was verified by comparing with the previous results for a seabed of infinite thickness under the two-dimensional progressive and standing wave fields derived by Yamamoto et al.(1978) and Tsai & Lee(1994). Based on the analytical solutions derived in this study, the influence of water depth and wave period on the characteristics of the seabed response for the progressive, standing and partial standing wave fields in a seabed of finite thickness were carefully examined. The analytical solution shows that the soil response (including pore pressure, shear stress, horizontal and vertical effective stresses) for a seabed of finite thickness is quite different in an infinite seabed. In particular, this study also found that the wave-induced seabed response under the partial wave conditions was reduced compared with the standing wave fields, and depends on the reflection coefficient.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.27-44
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• 2015

An analytical solution of dynamic responses for seabed in finite and infinite thicknesses including shallow has been developed under flow and partial standing wave with arbitrary reflection ration coexisting field at a constant water depth condition. In the analytical solution, a field was simply transited to a coexisting field of progressive wave and flow when reflection ratio was 0 and to a coexisting field of fully standing wave and flow when reflection ratio was 1. Based on the Biot's consolidation theory, the seabed was assumed as a porous elastic media with the assumptions that pore fluid is compressible and Darcy law governs the flow. The developed analytical solution was compared with the existing results and was verified. Using the analytical solution the deformation, pore pressure, effective and shear stresses were examined under various given values of reflection ratio, flow velocity, incident wave's period and seabed thickness. From this study, it was confirmed that the dynamic response of seabed was quite different depending on consideration of flow, which causes changing period and length of incident and reflection waves. It was also confirmed that dynamic response significantly depends on the magnitude of reflection ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1083-1088
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• 2016

25.8kV GIS part generated by sensors to measure contact an inflow of noise depending on the extent of the measured discharge occurs often not easy. Partial discharge signal measurement sensor suitable for developing a more useful measurements at the scene to this, partial discharge waveform analysis developed a sensor, and to utilize forSensor on the development of the most important is VSWR decided to (voltage standing wave ratio) voltage standing-wave ratio less than 1.5 and decided less than at the full spectrum bands that are measured, this time Return loss, as measured value by absolute criteria 14.0 dB produced the sensor, designed to or more. UHF 1.5~0.5 GHz bandwidth spectrum to be measured in GIS. UHF bands were designed to be able to measure the best signal. Recently, 25.8kV GIS production company has been increasing variety of GIS were made open spacer in partial discharge in accordance with the not very easy to detect the signal. The sensor is designed height of four cm external spacer is attachment GIS in an influx of outside noise measurement, and be so manufactured as to facilitate the least we've done. Also, since partial discharge which occur can measure the frequency of the 170kV GIS external partial-discharge signals that occur at the scene of insulation applied to the spacer. Features, and also derived good results using global positioning. Also measured discharge point about sensors that are stable and the reliability of the development and local substation equipment failure occurring signal analysis through the discharge for the prevention of widely. There should be to believe that used.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.41-52
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• 1995

the necessity of development of the Nearshore zone greatly emphasis in recent years. In the wave deformation model, we can get the wave height and wave direction using the hyperbolic mild slope equation considered the reflection wave. Radiation Stress the driving force of flow was calculated by the Watanabe and Maruyama who proposed on the partial standing wave. In the surf zone, applying the Izumiya and Horikawa's turbulent model considered the bottom friction and energy dissipation, we compared and examined with the Numerical model and Hydraulic test result of Watanabe and Maruyama. This model results obtained for Jin-ha Beach agreed well with the Numerical results. This model is expected so helpful to solve the prediction of the wave deformation problems in the development of the Nearshore zone in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.73-80
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• 2006

In order to examine the validity of an asymptotic solution for nonlinear interaction in asymmetric vibration modes of a perfect circular plate, we obtain the numerical solution. The motion of the plate is governed by nonlinear partial differential equation. The initial and boundary value problem is solved by using the finite difference method. The numerical solution is compared with the asymptotic solution. It is found that traveling waves relating clockwise and counterclockwise as well as standing wave are depicted by the numerical solution.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.34-40
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• 2010

Bragg reflection of nonlinear waves is simulated by a 2D fully nonlinear numerical wave tank (NWT). The developed NWT was based on the Boundary Element Method (BEM) with potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme with Runge-Kutta 4th-order time integration. A spatial variation of wave elevations and their Fourier amplitudes of each component are compared to investigate the effect of sea bottom ripples and their relative heights. The incident waves over an undulated sea bottom are partially reflected and changed to partial standing waves due to Bragg reflection. The present results are verified with linear calculations and experimental data. It is found that the 1st-order wave component is mainly affected by Bragg reflection and its spatial modulation is significant in front of the bottom ripples.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.505-519
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• 2016

If the seabed is exposed to high waves for a long period, the pore water pressure may be excessive, making the seabed subject to liquefaction. As the water pressure change due to wave action is transmitted to the pore water pressure of the seabed, a phase difference will occur because of the fluid resistance from water permeability. Thus, the effective stress of the seabed will be decreased. If a composite breakwater or other structure with large wave reflection is installed over the seabed, a partial standing wave field is formed, and thus larger wave loading is directly transmitted to the seabed, which considerably influences its stability. To analyze the 3-D dynamic response characteristics of the seabed around a composite breakwater, this study performed a numerical simulation by applying LES-WASS-3D to directly analyze the wave-structure-soil interaction. First, the waveform around the composite breakwater and the pore water pressure in the seabed and rubble mound were compared and verified using the results of existing experiments. In addition, the characteristics of the wave field were analyzed around the composite breakwater, where there was an opening under different incident wave conditions. To analyze the effect of the changed wave field on the 3-D dynamic response of the seabed, the correlation between the wave height distribution and pore water pressure distribution of the seabed was investigated. Finally, the numerical results for the perpendicular phase difference of the pore water pressure were aggregated to understand the characteristics of the 3-D dynamic response of the seabed around the composite breakwater in relation to the water-structure-soil interaction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.324-338
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• 2015

Analytical solutions for interaction between seabed and waves such as progressive wave or partial standing wave with arbitrary reflection ratio or standing wave have been developed by many researchers including Lee et al.(2014; 2015a; 2015b; 2015c; 2015d) and Yamamoto et al.(1978). They handled the pore-water pressure as oscillating pore-water pressure and residual pore-water pressure separately and discussed the seabed response on each pore-water pressure. However, based on field observations and laboratory experiments, the oscillating and residual pore-water pressures in the seabed do occur not separately but together at the same time. Therefore, the pore-water pressure should be investigated from a total pore-water pressure point of view. Thus, in this paper, the wave-induced seabed response including liquefaction depth was discussed among oscillating, residual, and total pore-water pressures' point of view according to the variation of wave, seabed, and flow conditions. From the results, in the field of flow with the same direction of progressive wave, the following seabed response has been identified; with increase of flow velocity, the dimensionless oscillating pore-water pressure increases, but the dimensionless residual pore-water pressure decreases, and consequently the dimensionless total pore-water pressure and the dimensionless liquefaction depth decrease.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.8
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• pp.384-389
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• 2005

The Resonance Scattering Theory(RST) provides the physical explanation of the scattered field that appears in the vicinity of the resonance frequency. The theory suggests that the amplitude of each Partial-wave mode can be divided into two components : resonance and non-resonant background. The long-standing difficulty in the application of RST is that it always requires background components. We have applied the RST to the electromagnetic scattering problems by a penetrable spherical scatterer and a cavity. In this paper, we show some numerical results, and validate background coefficients.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.484-497
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• 2016

In order to understand the characteristics of the topography change in front of an impermeable breakwater, a coupled model for a two-way analysis of the existing LES-WASS-2D and newly developed morphodynamic model was suggested. A comparison to existing experimental results revealed that the results computed using the 2-D hydro-morphodynamic model were in good agreement with the experimental results for the wave form, pore water pressure in the seabed, and topographical change in front of a submerged breakwater. It was shown that the two-way model suggested in this study is applicable to a morphological change in the seabed around a submerged breakwater. Then, using the numerical results, the topographical changes in front of an impermeable submerged breakwater were examined in relation to partial standing waves. Moreover, the characteristics of the local scour depths in front of them are also discussed in relation to incident wave conditions, sediment qualities, and submerged breakwater shapes.