• Title/Summary/Keyword: numerical methods

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Methods of Design Optimality Evaluation for Caisson Structural Systems (케이슨 구조계의 설계 최적성 평가)

  • Choi Min-Hee;Ryu Yeon-Sun;Cho Hyun-Man;Na Won-Bae
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.89-96
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    • 2005
  • Numerical procedure of design optimality evaluation is studied for caisson structural systems. Two kinds of evaluation methods can be considered; mathematical optimality criteria method (MOCM) and numerical optimization method (NOM). The choice of the method depends on the available information of the system MOCM can be used only when the information of all function values, gradients and Lagrange multipliers is available, which may not be realistic in practice. Therefore, in this study, NOMs are applied for the structural optimality evaluation, where only design variables are necessary. To this end, Metropolis genetic algorithm (MGA) is advantageously used and applied for a standard optimization model of caisson composite breakwater. In the numerical example, cost and constraint functions are assumed to be changed from the orignal design situation and their effects are evaluated for optimality. From the theoretical consideration and numerical experience, it is found that the proposed optimality evaluation procedure with MGA-based NOM is efficient and practically applicable.

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TWO-DIMENSIONAL CAVITATION PREDICTION BASED ON APPROXIMATE JACOBIAN MATRIX IN TWO-FLUID TWO-PHASE FLOW MODELS (2-유체 2상-유동 모델에서 근사 Jacobian 행렬을 이용한 2차원 캐비테이션의 예측)

  • Yeom Geum-Su;Chang Keun-Shik
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.183-186
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    • 2005
  • We developed an upwind numerical formulation based on the eigenvalues of the approximate Jacobian matrix in order to solve the hyperbolic conservation laws governing the two-fluid two-phase flow models. We obtained eight analytic eigenvalues in the two dimensions that can be used for estimate of the wave speeds essential in constructing an upwind numerical method. Two-dimensional underwater cavitation in a flow past structural shapes or by underwater explosion can be solved using this method. We present quantitative prediction of cavitation for the water tunnel wall and airfoils that has both experimental data as well as numerical results by other numerical methods and models.

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A Study on the Effective Algorithm by Fourier Transform for Numerical Conformal Mapping

  • Song, Eun-Jee
    • Journal of information and communication convergence engineering
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    • v.8 no.3
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    • pp.312-316
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    • 2010
  • Conformal mapping has been a familiar tool of science and engineering for generations. The methods of numerical mapping are usually classified into those which construct the map from standard domain such as the unit disk onto the 'problem domain', and those which construct the map in the reverse direction. We treat numerical conformal mapping from the unit disk onto the Jordan regions as the problem domain in this paper. The traditional standard methods of this type are based on Theodorsen integral equation. Wegmann's method is well known as a Newton-like efficient one for solving Theodorsen equation. An improved method for convergence by applying low frequency pass filter to the Wegmann's method was proposed. In this paper we propose an effective algorithm for numerical conformal mapping based on the improved method. This algorithm is able to determine the discrete numbers and initial values automatically in accordance with the given region and the required accuracy. This results come from analyzing the shape of given domain as seen in the Fourier Transform.

LARGE EDDY SIMULATION OF TURBULENT FLOWS AND DIRECT/DECOUPLED SIMULATIONS OF AEROACOUSTICS - PRESENT STATUS AND FUTURE PROSPECT -

  • Kato, Chisachi
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.2-4
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    • 2010
  • Due to rapid progress in the performance of high-end computers, numerical prediction of fluid flow and flow-induced sound is expected to become a vital tool for aero- and hydro- dynamic design of various flow-related products. This presentation focuses on the applications of large-scale numerical simulations to complex engineering problems with a particular emphasis placed on the low-speed flows. Flow field computations are based on a large eddy simulation that directly computes all active eddies in the flow and models only those eddies responsible for energy dissipations. The sound generated from low-speed turbulent flows are computed either by direct numerical simulation or by decoupled methods, according to whether or not the feedback effects of the generated sound onto the source flow field can be neglected. Several numerical examples are presented in order to elucidate the present status of such computational methods and discussion on the future prospects will also be given.

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The method of expressing the numerical value of small by using the density of the substances emitting smell (냄새 물질의 농도를 이용한 냄새 강도의 수치화)

  • 최은석;차성운
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.799-803
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    • 1997
  • Smell and sound are closely connected with our life. But there is no way to represent the exact numerical value of smell. On the contary, there is a method of represent the exact numerical value of sound. In this thesis, using and adapting this method about sound, a new method of expressing the numercal value of smell is going to be derived. These two methods are similar, but there are so many substances which emit smells and the methods of measuring the density of the substances are various according to kinds of the substances. So the new method about smell will be derived by a new idea.

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Study for Permanent Mold Design Technology and Porosity Defect Prediction Method by Multi-Phase Flow Numerical Simulations (다상유체해석을 통한 기포결함 예측과 금형설계기술)

  • Choi Y. S.;Cho I. S.;Hwang H. Y.;Choi J. K.;Hong J. H.
    • Transactions of Materials Processing
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    • v.14 no.3 s.75
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    • pp.224-232
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    • 2005
  • The high-pressure die-casting is one of the most effective methods to produce a large amount of products in short cycle time. This process, however, has a problem that the gas porosity defect appears easily. The generation of gas porosity is known mainly due to the air entrapment during the injection stage. Most of numerical simulations for the molten metal flow pattern observations have done in the treating of one phase fluid flow but the gas-liquid interface is essentially multi- phase phenomenon. In this paper, the two-phase fluid flow numerical simulation methods have been adapted to predict the gas porosity generations in the molten metal. The accuracy and the usefulness of the new simulation module have been emphasized and verified through some comparison experiments.

The Beam-Column Strength of Concrete Filled Tubes (콘크리트 충전 각형강관 기둥재의 최대내력)

  • Lee, Myung Jae
    • Journal of Korean Society of Steel Construction
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    • v.9 no.3 s.32
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    • pp.391-400
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    • 1997
  • The objective of this paper is to suggest formula of Concrete Filled Tube Beam-Column members maximum strength by using of numerical analysis and tests. The numerical analysis results are compared with test results for evaluating numerical analysis method. The formula of Limit State Design of Architectural Institute of KOREA is used for basic form of suggestion formula. In order to suggest formula, two methods are used. One is to use the coefficient, and the other is to use the amplified factor of material strength. The formula by two methods are compared with numerical analysis results.

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Experimental/Numerical Study on a Secondary Flow within a Rectangular Container Subjected to a Horizontal Oscillation (수평가진을 받는 직사각형 용기 내 2차 유동의 실험적/수치해석적 연구)

  • Byun, Min-Soo;Suh, Yong-Kweon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.7
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    • pp.1014-1021
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    • 2002
  • Analysis of two-dimensional secondary flows given by an oscillatory motion of a liquid with a free surface in a rectangular container subject to a linear reciprocating force is performed by numerical and experimental methods. FVM is used for the numerical computation of the two-dimensional flows. We considered the effects of the free-surface properties such as the surface tension and the dilatational viscosity. The boundary-layer analysis as well as an experiment is used in establishing the free surface properties. The secondary flow patterns are visualized by a laser sheet. It is shown that the secondary flow patterns predicted by the numerical methods are in good agreement with the experimental results.

Free Vibrations of Horizontally Curved Beams with General Boundary Condition (일반경계 조건을 갖는 수평 곡선보의 자유진동)

  • Lee, Tae-Eun;Ahn, Dae-Soon;Kang, Hee-Jong;Lee, Byoung-Koo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.870-875
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    • 2003
  • This paper deals with the free vibrations of horizontally curved beams with the general boundary condition, which consists of translational and rotational springs. The equations of general boundary condition of such beams are derived, while the ordinary differential equations governing free vibrations are adopted from the literature. The parabola as the curved beam's curvilinear shape is considered in numerical examples. For calculating the natural frequencies, the governing equations are solved by numerical methods. The Runge-Kutta and Determinant Search Methods are used for integrating the differential equations and for calculating the natural frequencies, respectively. for validation purpose, the numerical results obtained herein are compared to those obtained from the SAP 2000. With regard to numerical results, the relationships between frequency parameters and various beam parameters are presented in the forms of Table and figures.

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A family of dissipative structure-dependent integration methods

  • Chang, Shuenn-Yih;Wu, Tsui-Huang;Tran, Ngoc-Cuong
    • Structural Engineering and Mechanics
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    • v.55 no.4
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    • pp.815-837
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    • 2015
  • A new family of structure-dependent integration methods is developed to enhance with desired numerical damping. This family method preserves the most important advantage of the structure-dependent integration method, which can integrate unconditional stability and explicit formulation together, and thus it is very computationally efficient. In addition, its numerical damping can be continuously controlled with a parameter. Consequently, it is best suited to solving an inertia-type problem, where the unimportant high frequency responses can be suppressed or even eliminated by the favorable numerical damping while the low frequency modes can be very accurately integrated.