• Title/Summary/Keyword: Boundary Integral Method

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On the Vibration Analysis of the Floating Elastic Body Using the Boundary Integral Method in Combination with Finite Element Method

  • K.T.,Chung
    • Bulletin of the Society of Naval Architects of Korea
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    • v.24 no.4
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    • pp.19-36
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    • 1987
  • In this research the coupling problem between the elastic structure and the fluid, specially the hydroelastic harmonic vibration problem, is studied. In order to couple the domains, i.e., the structural domain and the fluid domain, the boundary integral method(direct boundary integral formulation) is used in the fluid domain in combination with the finite element method for the structure. The boundary integral method has been widely developed to apply it to the hydroelastic vibration problem. The hybrid boundary integral method using eigenfunctions on the radiation boundaries and the boundary integral method using the series form image-functions to replace the even bottom and free surface boundaries in case of high frequencies have been developed and tested. According to the boundary conditions and the frequency ranges the different boundary integral methods with the different idealizations of the fluid boundaries have been studied. Using the same interpolation functions for the pressure distribution and the displacement the two domains have been coupled and using Hamilton principle the solution of the hydroelastic have been obtained through the direct minimizing process. It has become evident that the finite-boundary element method combining with the eigenfunction or the image-function method give good results in comparison with the experimental ones and the other numerical results by the finite element method.

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THE INDIRECT BOUNDARY INTEGRAL METHOD FOR CURVED CRACKS IN PLANE ELASTICITY

  • Yun, Beong-In
    • Journal of the Korean Mathematical Society
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    • v.39 no.6
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    • pp.913-930
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    • 2002
  • For curved crack problems in plane elasticity, subjected to the traction conditions on the crack faces, we present a system of boundary integral equations. The procedure is based on the indirect boundary integral method in terms of real variables. For efficient mathematical analysis, we decompose the singular kernel into the Cauchy singular part and the regular one. As a result, solvability of the presented system is proved and availability of the present approach is shown by the numerical example of a circular arc crack.

Numerical Simulation of Incipient Breaking Waves (초기 쇄파의 수치모사)

  • 김용직;김선기
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.4
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    • pp.1-10
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    • 2002
  • For the time-domain simulation of incipient breaking waves, usually the boundary integral method has been used so far, and it seems to be successful except a problem of too much computation time. The present paper shows a new computation technique for the simulation of breaking wave experiment. This technique uses the high-order spectral/boundary element method and the boundary integral method in sequence, and reduces the computation time remarkably. The wave generation and energy focusing process is efficiently simulated by the high-order spectral/boundary element method. Only the wave over-turning process is simulated by the boundary integral method. In the example calculation result, salient features of breaking waves such as high particle velocities and accelerations are shown.

Desingularized indirect boundary integral method를 이용한 2 차원 단면의 동유체력 계산

  • O, Seung-Hun;Yang, Jin-Ho;Kim, Da-Jeong
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2015.10a
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    • pp.100-103
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    • 2015
  • 본 연구에서는 선박의 내항 및 조종성능평가를 위해 사용되는 2차원부가질량계수와 파랑감쇠계쉬를 desingularized indirect boundary integral method를 이용하여 주파수영역에서 계산하였다. 본 방법을 Rankine source를 유체경계면 전체에 분포하는 방법으로 수학적으로 간단하고 경계조건의 변경 및 적용이 용이하다는 장점이 있다. 하지만 물체표면, 자유수면 그리고 방사경계면의 계산영역 및 요소의 배치에 따라 계산정확도에 차이가 발생한다. 따라서 본 연구에서는 수치시험을 통해, 자유수면과 방사계면의 적절한 계산영역과 요소의 개수를 결정하였다. 계산의 정도와 효율성을 확보하기 위하여, 자유수면과 방사경계면의 계산영역과 요소의 분포를 파의주파수에 따라 달리 적용하였다. 본 연구에서 제안된 수치방법을 활용하여 계산된 동유체력과 실험에서 계측된 동유체력을 비교하여 본 방법의 정도를 확인하였다.

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High-Order Spectral/Boundary-Integral Method for the Calculation of Nonlinear Interactions between Hydrofoil and Free-Surface (수중익과 자유표면의 비선형 상호작용 계산을 위한 고차 스펙트럴/경계적분법)

  • Kim Yong Jig;Ha Young Rok;Kwon Sun Hong;Kim Dong Joon
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.369-372
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    • 2002
  • Under the assumption of potential flow, free-surface flows around a 2-dimensional hydrofoil are calculated by high-order spoctral/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. Comparisons of the calculated free-surface profiles with other experimental results show relatively good agreements. As another example, free-surface flow generated by the heaving and translating hydrofoil is calculated and discussed.

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Calculation of Nonlinear Interactions between Hydrofoil and Free-Surface by the High-Order Spectral/Boundary-Integral Method (고차 스펙트럴 / 경계적분법에 의한 수중익과 자유표면의 비선형 상호작용 계산)

  • 김용직;하영록
    • 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.

Nonlinear Uplift Wave Pressure Distribution Acting on the Caisson of Composite Breakwater (혼성방파제의 케이슨에 작용하는 비선형양압력분포에 관한 연구)

  • 김도삼;배기성
    • Journal of Ocean Engineering and Technology
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    • v.15 no.4
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    • pp.20-27
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    • 2001
  • Recently numerical approaches for wave loads acting on the vertical caisson of breakwater, and resulting wave reflection and transmission coefficients have been performed. Although the numerical studies by Sulisz's(1997) and Kim et al.(2000) are suggested representatively, theoretical formulation for nonlinear wave pressure is not developed yet. And experimental results of Sulisz(1997) revealed that nonlinear uplift pressure on the caisson may be produced largely on the case of caisson founded on the high rubble mound. From the results of this study, the nonlinear theory for the uplift wave pressure acting on the caisson by applying boundary integral method of Green theorem is formulated, and also the characteristics of nonlinear uplift pressure and run-up height on the caisson are evaluated numerically, according to the variations of hydraulic properties of the rubble mound.

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Nonlinear Motion for an Elliptic Cylinder under Free Surface (자유표면 아래의 타원형 실린더에 대한 비선형 운동)

  • 이호영;임춘규
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.4
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    • pp.38-44
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    • 2004
  • The motion response analysis of a submerged elliptic cylinder in waves is presented and the elliptic cylinder is a simplification of the section of submarine in this paper. The method is based on boundary integral method and two-dimensional 3 degree motions are calculated in regular harmonic waves. The fully nonlinear free surface boundary condition is assumed in an numerical domain and this solution is matched along an assumed boundary as a linear solution composed of transient Green function, The large amplitude motions of an elliptic cylinder are directly simulated and effects of wave frequency, wave amplitude and the distance from buoyancy center to gravity center are discussed.

Numerical Modeling of Short-Time Scale Nonlinear Water Waves Generated by Large Vertical Motions of Non-Wallsided Bodies (Non-Wallsided 물체의 연직운동에 의해 발생된 파의 비선형 해석을 위한 수치해석 모형의 연구)

  • Park, Jong-Hwan;;Troesch, Armin W.
    • Journal of Ocean Engineering and Technology
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    • v.7 no.1
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    • pp.33-55
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    • 1993
  • 선수충격파의 문제를 푸는데 있어서 Boundary Integral Method(BIM)의 여러가지 수치 해석방법이 검토되었으며, 특히 여러가지 Time stepping scheme, Green function, far-field 조건등에 따른 수치해석안정성과 정확성의 상관관계가 연구되었다. von Neumann 안정성해석과 matrix 안정성해석 등을 이용한 선형 안정성해석을 기초로하여, 수치해석방법의 안정성 여부를 체계적으로 조사할 수 있는 parameter(Free Surface Stability number)를 설정하고, 이 parameter의 변화에 따른 비선형 운동해석을 연구하였다. 그 결과 비선형성이 심하지 않은 기진파의 경우에서는 비선형 운동해석의 수치해석 안정성의 선형 수치해석 안정성과 큰 차이가 없음을 알 수 있게 된다.

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