• Title/Summary/Keyword: 수치 적분

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Analytical Evaluation of the Surface Integral in the Singularity Methods (특이점분포법의 표면적분항의 해석적 계산)

  • Jung-Chun Suh
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.1
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    • pp.14-28
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    • 1992
  • For a planar curve-sided paned with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach(1986) show that the surface integral can be transformed into contour integral by using Stokes' formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration(suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer tiome.

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Numerical Analysis of Two-Dimensional Nonlinear Radiation Problem Using Higher-Order Boundary Element Method (고차경계요소법을 이용한 2차원 비선형 방사문제의 수치해석)

  • Hong-G. Sung;Hang-S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.37 no.1
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    • pp.67-81
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    • 2000
  • An accurate and efficient numerical method for two-dimensional nonlinear radiation problem has been developed. The wave motion due to a moving body is described by the assumption of ideal fluid flow, and the governing Laplace equation can be effectively solved by the higher-order boundary element method with the help of the GMRES (Generalized Minimal RESidual) algorithm. The intersection or corner problem is resolved by utilizing the so-called discontinuous elements. The implicit trapezoidal rule is used in updating solutions at new time steps by considering stability and accuracy. Traveling waves caused by the oscillating body are absorbed downstream by the damping zone technique. It is demonstrated that the present method for time marching and radiation condition works efficiently for nonlinear radiation problem. To avoid the numerical instability enhanced by the local gathering of grid points, the regriding technique is employed so that all the grids on the free surface may be distributed with an equal distance. This makes it possible to reduce time interval and improve numerical stability. Special attention is paid to the local flow around the body during time integration. The nonlinear radiation force is calculated by the "acceleration potential technique". Present results show good agreement with other numerical computations and experiments.

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Implicit Numerical Integration of Two-surface Plasticity Model for Coarse-grained Soils (Implicit 수치적분 방법을 이용한 조립토에 관한 구성방정식의 수행)

  • Choi, Chang-Ho
    • Journal of the Korean Geotechnical Society
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    • v.22 no.9
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    • pp.45-59
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    • 2006
  • The successful performance of any numerical geotechnical simulation depends on the accuracy and efficiency of the numerical implementation of constitutive model used to simulate the stress-strain (constitutive) response of the soil. The corner stone of the numerical implementation of constitutive models is the numerical integration of the incremental form of soil-plasticity constitutive equations over a discrete sequence of time steps. In this paper a well known two-surface soil plasticity model is implemented using a generalized implicit return mapping algorithm to arbitrary convex yield surfaces referred to as the Closest-Point-Projection method (CPPM). The two-surface model describes the nonlinear behavior of coarse-grained materials by incorporating a bounding surface concept together with isotropic and kinematic hardening as well as fabric formulation to account for the effect of fabric formation on the unloading response. In the course of investigating the performance of the CPPM integration method, it is proven that the algorithm is an accurate, robust, and efficient integration technique useful in finite element contexts. It is also shown that the algorithm produces a consistent tangent operator $\frac{d\sigma}{d\varepsilon}$ during the iterative process with quadratic convergence rate of the global iteration process.

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.

p-Version Finite Element Analysis of Elasto-Plastic Cracked Plates Including Strain Hardening Effects (변형률 경화효과를 고려한 탄소성 균열판의 p-Version 유한요소해석)

  • 우광성;홍종현;윤영필
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.4
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    • pp.537-549
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    • 1999
  • 선형탄성 파괴해석은 균열을 갖는 변형률 경화재료의 파괴거동을 예측하는데 불충분하기 때문에 최근에는 균열 선단 부에서 대규모 소성 역을 갖는 균열 체에 적용할 수 있는 많은 파괴역학개념이 제안되고 있다. 따라서, 본 연구에서는 대규모항복 조건하의 연성파괴를 보이는 평판을 정확하게 해석할 수 있는 새로운 유한요소모델을 제시하고자 한다. 균열 선단 부의 응력 장을 정의하는데 가장 지배적인 파괴매개변수인 J-적분 값과 소성 역의 크기 및 형상을 J-적분법과 등가영역적분법을 통해 파괴거동을 설명할 수 있도록 증분소성이론에 기초를 둔 p-version 유한요소해석이 채택되었다. 제안된 유한요소모델에 의한 수치해석결과는 이론 해와 h-version 유한요소해석과 비교되었다.

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Advanced Finite Element Analysis for Linear Viscoelastic Problems of a Hereditary-Type Constitutive Law (유전적분형 선형 점탄성문제의 유한요소법에 의한 효율적 해석)

  • 심우진;이성희
    • Computational Structural Engineering
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    • v.6 no.2
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    • pp.103-114
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    • 1993
  • An advanced time-domain finite element formulation is presented for the displacement and stress analysis of isotropic, linear viscoelastic problems of a hereditary-type constitutive law. The semidiscrete finite element method with linear time-stepping scheme and an elastic-viscoelastic correspondence principle are used in the theoretical development. An efficient treatment of hereditary integral is introduced to improve the numerical accuracy, to reduce the computation time, and to avoid the use of large memory storage. Two-dimensional numerical examples of plane strain and plane stress are solved under the assumption on the material property of being elastic in dilatation and like three-element Voigt model in distorsion, and compared with the analytical solutions and the past numerical results to show the versatility and efficiency of the proposed method.

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Comparison of Experimental Data on the Fluctuation Integral Gij with the Calculated Results Based on the Activity Coefficient Model in Binary Mixtures Containing c-Hexane (c-hexane을 포함하는 이성분계 혼합물에서 활동도계수 모델을 이용한 변동적분 Gij의 계산 수치와 실험 수치의 비교)

  • Hur, Kwang-II;Kwon, Yong-Jung
    • Journal of Industrial Technology
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    • v.20 no.A
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    • pp.203-209
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    • 2000
  • The fluctuation integrals which give useful information in the structure of solution are associated with the mixed direct correlation integral ($C_{12}$) known. Using its weighted arithmetic mean of $C_{11}$ and $C_{22}$ and the activity coefficient model, the fluctuation integrals on solute-solute, solvent-solute, and solvent-solvent can be calculated in the function of mole fraction. In this work, several binary mixtures containing c-hexane were tested and the results on the fluctuation integrals were rather good.

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An Investigation of Self-Radiation Impedance of a Square Piston using an Integral Equation in the Rigid Infinite Baffle (적분식을 이용한 무한배플 사각형 진동체의 자기방사 임피던스 연구)

  • Lee, Jong-Kil;Seo, In-Chang
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.5
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    • pp.58-62
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    • 1995
  • Integral equations of self-radiation impedance of a rectangular piston in a rigid infinite baffle are derived using by polar coordinate. The self-radiation impedance is separated by two parts ; self-radiation resistance and self-radiation reactance. Derived integral equations are simulated by numerical method. Based on the numerical results, self-radiation impedance can be obtained in the low and high frequency ranges without any limited conditions.

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Free Oscillation Analysis in the Coastal Area using Integrated Finite Difference Method (적분차분법을 이용한 연안역에서의 해수고유진동해석)

  • LEE Byung-Gul
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.27 no.6
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    • pp.782-786
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    • 1994
  • Integrated finite difference method (IFDM) is used to solve one dimensional free oscillation problem in the coastal area. To evaluate the solution accuracy of IFDM in free oscillation analysis, two finite difference equations based on area discretization method and point discretization method are derived from the governing equations of free oscillation, respectively. The difference equations are transformed into a generalized eigenvalue problem, respectively. A numerical example is presented, for which the analytical solution is available, for comparing IFDM to conventional finite difference equation (CFDM), qualitatively. The eigenvalue matrices are solved by sub-space iteration method. The numerical results of the two methods are in good agreement with analytical ones, however, IFDM yields better solution than CFDM in lower modes because IFDM only includes first order differential operator in finite difference equation by Green's theorem. From these results, it is concluded that IFDM is useful for the free oscillation analysis in the coastal area.

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Singular Cell Integral of Green's tensor in Integral Equation EM Modeling (적분방정식 전자탐사 모델링에서 Green 텐서의 특이 적분)

  • Song Yoonho;Chung Seung-Hwan
    • Geophysics and Geophysical Exploration
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    • v.3 no.1
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    • pp.13-18
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    • 2000
  • We describe the concept of the singularity in the integral equation of electromagnetic (EM) modeling in comparison with that in the integral representation of electric fields in EM theory, which would clarify the singular integral problems of the Green's tensor. We have also derived and classified the singular integrals of the Green's tensors in 3-D, 2.5-D and 2-D as well as in the thin sheet integral equations of the EM scattering problem, which have the most important effect on the accuracy of the numerical solution of the problems.

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