• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.484-491
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• 2007

Numerical experiments using a numerical wave tank have been performed to verier the nonlinear interaction between monochromatic waves and a submerged horizontal plate. As a model for numerical wave tank, we used a higher-order Boundary Element Method(BEM) based on fully nonlinear potential flow theory and CADMAS-SURF for solving Navier Stokes equations and exact free surface conditions. Both nonlinear models are able to predict the higher harmonic generation in the shallow water region over a submerged horizontal plate. CADMAS-SURF, which involves the viscous effect, can evaluate the higher harmonic generation by flow separation and vortices at the each ends of plate. The comparison of reflection and transmission coefficients with experimental results(Patarapanich and Cheong, 1989) at different lengths and submergence depths of a horizontal plate are presented with a good agreement. It is found that the transfer of energy from the incident fundamental waves to higher harmonics becomes larger as the submergence depth ratio decreases and the length ratio increases.

• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.199-205
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• 2004

We have developed a composite grid method for the solution of the radiation problem We divide the domain into two different grids; one is a moving grid system and the other is a fixed grid system. This numerical method is applied to calculation of the radiation forces generated by the submerged plate oscillating near a free surface. The experimental data are compared with the numerical ones obtained by the present method and a linear potential theory. As a result, we can confirm the accuracy of the present method. Finally, Lie have evaluated the effect of nonlinear and viscous damping on the hydrodynamic forces acting on the submerged plate.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.3
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• pp.149-154
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• 2018

We consider the system is subject to the linearly polarized oscillatory external field. We study the optical quantum transition Line shapes(QTLS) which show the absorption power and the quantum transition line widths(QTLW) of electron-piezoelectric phonon interacting system. We analyze the magnetic field dependence of the QTLS and the QTLW in various cases. In order to analysis the quantum transition, we compare the magnetic field dependence of the QTLW and the QTLS of two transition process, the intra-Landau level transition process and the inter-Landau level transition process.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.3
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• pp.351-360
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• 2000

A simple numerical modelling technique is proposed for estimating the shear lag effects of framed-tube system with multiple internal tubes. The tube(s)-in-tube structure is analysed by using an analogy approach in which each tube is individually modelled by a beam that can accounts for the flexural and shear deformations, as well as the shear lag effects. The numerical analysis is based on the minimum potential energy principle in conjunction with the variational approach. The shear lag phenomenon of such structures is studied with additional bending stresses. Structural parameters governing the shear lag behaviour in tube(s)-in-tube structures are also investigated through thirty-three numerical examples.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.3
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• pp.129-134
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• 2017

We investigated theoretically the quantum optical transition properties of Si, in quasi 2-Dimensinal Landau splitting system, based on quantum transport theory. We apply the quantum transport theory (QTR) to the system in the confinement of electrons by square well confinement potential under linearly polarized oscillating field. We use the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS). In order to analyze the quantum transition, we compare the temperature and the magnetic field dependencies of the QTLW and the QTLS on four transition processes, namely, the intra-leval transition process, the inter-leval transition process, the phonon emission transition process and the phonon absorption transition process.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.368-374
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• 2011

Recently, the ship vibration analysis technique has been well set up by using FEM. The methods considering the hydrodynamic added mass and damping of the fluid surrounding a floating ship have been well developed, so that they can be calculated by using the commercial package FEM programs such as MSC/NASTRAN, ADINA and ANSYS. Especially, MSC/NASTRAN has the functions to consider the fluid in tanks(MFLUID) and to solve the Fluid-Structure Interaction(FSI) problem(DMAP). In this study, the global ship vibration with considering the added mass distributed at the grid points on the wetted shell surface is introduced to. In the new method, the velocity potentials of the fluid surrounding a floating ship are calculated by solving the Lapalce equation using the Boundary Element Method(BEM), and the point mass is obtained by integrating the potentials at the points. Then, the global vibration analyses of the ship structure with distributed added mass on the wetted surface are carried out for an oil/chemical tanker. During the future sea trial, the results will be confirmed by measurement.

• Computational Structural Engineering
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• v.4 no.4
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• pp.135-144
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• 1991

The finite element technique incorporatating infinite elements is applied to analyzing the general three dimensional wave-structure interaction problems within the limits of linear wave theory. The hydrodynamic forces are assumed to be inertially dominated, and viscous effects are neglected. In order to analyze the corresponding boundary value problems efficiently, two types of elements are developed. One is the infinite element for modeling the radiation condition at infinity, and the other is the fictitious bottom boundary element for the case of deep water. To validate those elements, numerical analyses are performed for several floating structures. Comparisons with the results by using other available solution methods show that the present method incorporating the infinite and the fictitious bottom boundary elements gives good results.

• Elastomers and Composites
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• v.35 no.1
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• pp.29-37
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• 2000

In this study as a basic research of the elastomer, we show the results of the behavior of the two different chain length polymers in the melt confined between two impenetrable planes. The cubic lattice simulations are conducted in the canonical ensemble with a method that is a combination of reptation and crackshaft bond flip motions. A total of 680 chains which are 544 short chains comprising 10 beads and 136 long chains comprising 160 beads were placed in 20 lattice layers. It was assumed that there is no energetic interactions between covalently connected beads. while all other neighbors will interact with a truncated 6-12 Lennard-Jones potential. From the analysis of the simulation results, it was shown that purely entropic effects caused the shorter chains to partition preferentially to the surface. We also showed that the center of mass density of the shorter chains shows maximum near the surface. This is the opposite phenomena when compared to that of the longer chains. However, the segments of the shorter and the longer chains did not display any significant changes in bond order.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.327-334
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• 2013

The interaction of oblique incident waves with a surface-mounted horizontal porous plate is investigated using matched eigenfunction expansion method under the assumption of linear potential theory. The new boundary condition on the porous plate suggested by Zhao et al.(2010) when it is situated at the still water surface is used. The imaginary part of the first propagating-mode eigenvalue in the fluid region under a horizontal porous plate, is closely related to the energy dissipation across the porous plate. By changing the porosity, plate width, wave frequencies, and incidence angles, the reflection and transmission coefficients as well as the wave loads on the porous plate are obtained. It is found that the transmission coefficients can be significantly reduced by selecting optimal porous parameter b = 5.0, also increasing the plate width and incidence angle.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.27-32
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• 2003

Under the assumption of potential flow, free-surface flow around a hydrofoil is calculated by the high-order spectra1!boundary-integral method, This method is one of the most efficient numerical methods by which the nonlinear interactions between hydrofoil and free-surface can be simulated in time-domain. In this method. the wave potential which represents the nonlinear evolution of free-surface is solved by the high-order spectral method and the body potential which provides the effects of hydrofoil and shed vortex is solved by the boundary-integral method. The calculated free-surface profiles which are generated by a uniformly translating hydrofoil are compared with other experimental results. And they show relatively good agreements each other. As another example, free-surface flow generated by a heaving and translating hydrofoil is calculated and discussed.