• Title/Summary/Keyword: green integral equation

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A Study on the Floating OWC Chamber Motion in Waves (부유기 OWC 챔버의 파중 운동해석)

  • 홍도천
    • Journal of Ocean Engineering and Technology
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    • v.16 no.3
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    • pp.19-27
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    • 2002
  • The motion of a floating OWC chamber in waves is studied taking account of fluctuating air pressure in the air chamber. An atmospheric pressure drop occurs across the upper opening of the chamber which causes not only hydrodynamic but also pneumatic added mass and damping forces to the floating chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. the potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function wile the outer problem with the Kelvin Green function. The two integral equations are solved simultaneously by making use of a matching boundary condition at the lower opening of the chamber to the outer water region. The chamber motion in the frequency domain is calculated for various values of parameters related to the atmospheric pressure drop. The present methods can also be sued for the analysis of air-cushion vehicle motion as well as for the design of a floating OWC wave energy absorber.

A Study on the Floating OWC Chamber Motion in Waves (부유식 OWC 챔버의 파중 운동해석)

  • Hong, Do-Chun;Hong, Sa-Young
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2002.05a
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    • pp.191-197
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    • 2002
  • The motion of a floating OWC chamber in waves is studied taking account of fluctuating.air pressure in the air chamber. An atmospheric pressure drop occurs across the upper opening of the chamber which causes not only hydrodynamic but also pneumatic added mass and damping forces to the floating chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The two integral equations are solved simultaneously by making use of a matching boundary condition at the lower opening of the chamber to the outer water region. The chamber motion in the frequency domain is calculated for various values of parameters related to the atmospheric pressure drop. The present methods can also be used for the analysis of air-cushion vehicle motion as well as for the design oj a floating owe wave energy absorber.

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Mean Drift Force Acting on a Floating OWC Wave Power Device (부유식 OWC 파력발전 챔버의 파 표류력해석)

  • HONG Do-Chun;HONG Sa-Young;HONG Seok-Won
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.373-376
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    • 2002
  • The drift force acting on a floating OWC chamber in waves is studied taking account of fluctuating air pressure in the air chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The drift forces as well as the chamber motions are calculated taking account of the air pressure in the chamber.

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신속한 3차원 전자탐사 모델링

  • Jo, In-Gi;Kim, Ha-Rim
    • Journal of the Korean Geophysical Society
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    • v.5 no.1
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    • pp.63-71
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    • 2002
  • The integral equation method is a powerful tool for electromagnetic numerical modeling. But the difficulty of this technique is the size of their linear equations, which demands excessive memory and calculation time to invert. This limitation of the integral equation method becomes critical in inverse problem. To overcome this limitation, a lot of approximation and series methods, such as conventional Born, modifed Born and extended Born, were developed. But all the methods need volume integration of Green tensor, which is very time consuming. In electromagnetic theory, Green tensor rapidly decreases as the distance between source and field cell increases. Therefore, the source cell which are far away from the field cell does not make an effect on the electric field of the field cell. Consequently, by ignoring the effect of Green tensor due to far away source cells, computing time for electromagnetic numerical modeling can be reduced dramatically. Comparisons of this new method against a full integral equation, extended Born approximation and series code show that the method is accurate enough much less time consuming.

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Development of an Elastic Analysis Technique Using the Mixed Volume and Boundary Integral Equation Method (혼합 체적-경계 적분방정식법을 이용한 탄성해석 방법 개발)

  • Lee, Jeong-Gi;Heo, Gang-Il;Jin, Won-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.4
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    • pp.775-786
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    • 2002
  • A Mixed Volume and Boundary Integral Equation Method is applied for the effective analysis of elastic wave scattering problems and plane elastostatic problems in unbounded solids containing general anisotropic inclusions and voids or isotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only Green's function for the unbounded isotropic matrix is involved in their formulation for the analysis. This new method can also be applied to general two-dimensional elastodynamic and elastostatic problems with arbitrary shapes and number of anisotropic inclusions and voids or isotropic inclusions. In the formulation of this method, the continuity condition at each interface is automatically satisfied, and in contrast to finite element methods, where the full domain needs to be discretized, this method requires discretization of the inclusions only. Finally, this method takes full advantage of the pre- and post-processing capabilities developed in FEM and BIEM. Through the analysis of plane elastostatic problems in unbounded isotropic matrix with orthotropic inclusions and voids or isotropic inclusions, and the analysis of plane wave scattering problems in unbounded isotropic matrix with isotropic inclusions and voids, it will be established that this new method is very accurate and effective for solving plane wave scattering problems and plane elastic problems in unbounded solids containing general anisotropic inclusions and voids/cracks or isotropic inclusions.

Non-stationary mixed problem of elasticity for a semi-strip

  • Reut, Viktor;Vaysfeld, Natalya;Zhuravlova, Zinaida
    • Coupled systems mechanics
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    • v.9 no.1
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    • pp.77-89
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    • 2020
  • This study is dedicated to the dynamic elasticity problem for a semi-strip. The semi-strip is loaded by the dynamic load at the center of its short edge. The conditions of fixing are given on the lateral sides of the semi-strip. The initial problem is reduced to one-dimensional problem with the help of Laplace's and Fourier's integral transforms. The one-dimensional boundary problem is formulated as the vector boundary problem in the transform's domain. Its solution is constructed as the superposition of the general solution for the homogeneous vector equation and the partial solution for the inhomogeneous vector equation. The matrix differential calculation is used for the deriving of the general solution. The partial solution is constructed with the help of Green's matrix-function, which is searched as the bilinear expansion. The case of steady-state oscillations is considered. The problem is reduced to the solving of the singular integral equation. The orthogonalization method is applied for the calculations. The stress state of the semi-strip is investigated for the different values of the frequency.

On the Improved Green Integral Equation applied to the Water-wave Radiation-Diffraction Problem

  • Do-Chun,Hong
    • Bulletin of the Society of Naval Architects of Korea
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    • v.24 no.1
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    • pp.1-8
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    • 1987
  • It is shown that irregular frequencies in the source and doublet distribution method, can be eliminated if the Green function associated with Kelvin's source of pulsating strength, is modified only in the region inside the body at the level of the undisturbed free surface. The system of the resulting Green integral equation is augmented without loss of the square-integrable property of its kernel so hat the discretisation yield N linearly independent equations for N unknown variables. From the solution, the potential and velocity at any point on the wetted surface of a surface-piercing body can be found using the properties of the double layer composed of the source and normal doublet distribution.

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Analysis of a Dipole Antenna Attached on a Dielectric Slab Using a Spectral-Domain Green's Function and the Method of Moments (주파수 영역 Green 함수와 모멘트법을 이용한 유전체 평판 부착 다이폴 안테나의 특성해석)

  • 오이석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.10
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    • pp.2703-2709
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    • 1996
  • This paper proposes an exact numerical method for analyzing a dipole antenna attached on a dielectric slab. A Green's function for an infinitesimal current filament on a dielectric slab is derived and a field integral equation is formulated using a boundary condition. The moment Method is used to solve the field integral equation to otain current distribution on the antenna. Since an asymptotic function is used to compute the impedance matrix elements, the computataion time is significantly reduced. Using the computed current distributions, the input impedances, the resonance lengths and the resonant resistances of the antennas for various values of the thichnessandthe dielectric constant of the slab are obtained. It was found that the resonant length and the resonant resistance are decrease monotonically as the dielectric constant increases, however, those are changed up-and-down as the substrate thickness increases.

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Elastic Analysis of a Half-Plane Containing an Inclusion and a Void Using Mixed Volume and Boundary Integral Equation Method (혼합 체적-경계 적분방정식법을 이용한, 함유체와 공동을 포함한 반무한 고체에서의 탄성해석)

  • Lee, Jung-Ki;Yoon, Koo-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.12
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    • pp.1072-1087
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    • 2008
  • A mixed volume and boundary integral equation method (Mixed VIEM-BIEM) is used to calculate the plane elastostatic field in an isotropic elastic half-plane containing an isotropic or anisotropic inclusion and a void subject to remote loading parallel to the traction-free boundary. A detailed analysis of stress field at the interface between the isotropic matrix and the isotropic or orthotropic inclusion is carried out for different values of the distance between the center of the inclusion and the traction-free surface boundary in an isotropic elastic half-plane containing three different geometries of an isotropic or orthotropic inclusion and a void. The method is shown to be very accurate and effective for investigating the local stresses in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions and multiple voids.

Inverse Design Method of Supersonic wings Using Intergral Equations (적분방정식을 이용한 초음속 날개의 역설계법)

  • Jeong, Sin Gyu;Kim, Gyeong Hun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.4
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    • pp.8-15
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    • 2003
  • A practical design method for supersonic wings has been developed. The method is based on Takanashi's method that uses integral equations and iterative "residual-correction" concept. The geometry correction is calculated by solving linearized small perturbation equation (LSP) with the difference between garget and objective surface pressure distributions as a boundary condition. In the present method, LSP equation is analytically transformed to integral equations by using the Green's theorem. Design results of an isolated wing and wing-nacelle configurations are presented here.