• Title, Summary, Keyword: Numerical methods

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Stability of Explicit Symplectic Partitioned Runge-Kutta Methods

  • Koto, Toshiyuki;Song, Eunjee
    • Journal of information and communication convergence engineering
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    • v.12 no.1
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    • pp.39-45
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    • 2014
  • A numerical method for solving Hamiltonian equations is said to be symplectic if it preserves the symplectic structure associated with the equations. Various symplectic methods are widely used in many fields of science and technology. A symplectic method preserves an approximate Hamiltonian perturbed from the original Hamiltonian. It theoretically supports the effectiveness of symplectic methods for long-term integration. Although it is also related to long-term integration, numerical stability of symplectic methods have received little attention. In this paper, we consider explicit symplectic methods defined for Hamiltonian equations with Hamiltonians of the special form, and study their numerical stability using the harmonic oscillator as a test equation. We propose a new stability criterion and clarify the stability of some existing methods that are visually based on the criterion. We also derive a new method that is better than the existing methods with respect to a Courant-Friedrichs-Lewy condition for hyperbolic equations; this new method is tested through a numerical experiment with a nonlinear wave equation.

Numerical Evaluation of Various Numerical Integration Methods in Free Vibration Analysis (자유진동 해석에서 수치적분기법의 수치적평가)

  • 송주한;안대순;오상진;박광규
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1249-1253
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    • 2001
  • Numerical analysis is sometimes used to solve the problems in the engineering and natural science fields. On this reason, the faster, more practical system in computing the numerical solution is required. This paper deals with the numerical evaluation of various numerical integration methods which is frequently used in the engineering fields. This paper choices four integration methods such as Euler method, Heun's method, Runge-Kutta method and Gill's method for evaluating the each integration method. In numerical examples, the free vibration problem on an elastic foundation is chosen. As the numerical results, the natural frequencies and the running time are obtained, and these results are compared to examine the practicality of integration methods.

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Numerical dissipation for explicit, unconditionally stable time integration methods

  • Chang, Shuenn-Yih
    • Earthquakes and Structures
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    • v.7 no.2
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    • pp.159-178
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    • 2014
  • Although the family methods with unconditional stability and numerical dissipation have been developed for structural dynamics they all are implicit methods and thus an iterative procedure is generally involved for each time step. In this work, a new family method is proposed. It involves no nonlinear iterations in addition to unconditional stability and favorable numerical dissipation, which can be continuously controlled. In particular, it can have a zero damping ratio. The most important improvement of this family method is that it involves no nonlinear iterations for each time step and thus it can save many computationally efforts when compared to the currently available dissipative implicit integration methods.

Methods of Reconstructing Numerical Analysis Program for Utilizing the Internet (인터넷을 활용하기 위한 수치해석 프로그램의 재구성 방법)

  • Song Heeyong;Koak Youngkyun;Ko Sungho
    • Proceedings of the KSME Conference
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    • pp.63-66
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    • 2002
  • The present study introduces some useful methods of implementing the Internet numerical analysis program with existing numerical codes for utilizing the Internet environment. The Internet gives developers good environment for development and release. Several methods were suggested, and some of them were implemented with an existing numerical code named SOLA-VOF, a computational fluid dynamics program to solve two-dimensional transient flow problems with free surface. This was reconstructed with Java technologies and compared with the original one. Java technologies have been applied to development of Internet applications for a long time. The objective of this work is to contrive methods of implementing Internet numerical analysis program with existing numerical codes and confirm the possibility of them. Methods using the applet-servlet communication were suggested and implemented. In addition, the Java web services with XML was introduced, which makes possible the cooperation of components. Although the concept has been suggested and developed for business applications, it can also be used for engineering softwares. Therefore, this study will be a preparation for numerical analysis to participate in engineering web services.

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Numerical heat transfer analysis methodology for multiple materials with different heat transfer coefficient in unstructured grid for development of heat transfer analysis program for 3 dimensional structure of building (건물의 3차원 구조체에 대한 전열해석 프로그램 개발 중 서로 다른 열전도율을 갖는 복합재질 3차원 구조의 비정렬 격자에 대한 전산해석 방법)

  • Lee, Juhee;Jang, Jinwoo;Lee, Hyeonkyun;Lee, Youngjun;Lee, Kyusung
    • KIEAE Journal
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    • v.16 no.1
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    • pp.81-87
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    • 2016
  • Purpose: Heat transfers phenomena are described by the second order partial differential equation and its boundary conditions. In a three-dimensional structure of a building, the heat transfer phenomena generally include more than one material, and thus, become complicate. The analytic solutions are useful to understand heat transfer phenomena, but they can hardly be applied in engineering or design problems. Engineers and designers have generally been forced to use numerical methods providing reliable results. Finite volume methods with the unstructured grid system is only the suitable means of the analysis for the complex and arbitrary domains. Method: To obtain an numerical solution, a discretization method, which approximates the differential equations, and the interpolation methods for temperature and heat flux between two or more materials are required. The discretization methods are applied to small domains in space and time, and these numerical solutions form the descretized equations provide approximated solutions in both space and time. The accuracy of numerical solutions is dependent on the quality of discretizations and size of cells used. The higher accuracy, the higher numerical resources are required. The balance between the accuracy and difficulty of the numerical methods is critical for the success of the numerical analysis. A simple and easy interpolation methods among multiple materials are developed. The linear equations are solved with the BiCGSTAB being a effective matrix solver. Result: This study provides an overview of discretization methods, boundary interface, and matrix solver for the 3-dimensional numerical heat transfer including two materials.

Performances of non-dissipative structure-dependent integration methods

  • Chang, Shuenn-Yih
    • Structural Engineering and Mechanics
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    • v.65 no.1
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    • pp.91-98
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    • 2018
  • Three structure-dependent integration methods with no numerical dissipation have been successfully developed for time integration. Although these three integration methods generally have the same numerical properties, such as unconditional stability, second-order accuracy, explicit formulation, no overshoot and no numerical damping, there still exist some different numerical properties. It is found that TLM can only have unconditional stability for linear elastic and stiffness softening systems for zero viscous damping while for nonzero viscous damping it only has unconditional stability for linear elastic systems. Whereas, both CEM and CRM can have unconditional stability for linear elastic and stiffness softening systems for both zero and nonzero viscous damping. However, the most significantly different property among the three integration methods is a weak instability. In fact, both CRM and TLM have a weak instability, which will lead to an adverse overshoot or even a numerical instability in the high frequency responses to nonzero initial conditions. Whereas, CEM possesses no such an adverse weak instability. As a result, the performance of CEM is much better than for CRM and TLM. Notice that a weak instability property of CRM and TLM might severely limit its practical applications.

The Comparison of Numerical Integration Methods for the KASIOPEA, Part II

  • Jo, Jung-Hyun
    • Bulletin of the Korean Space Science Society
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    • pp.26.4-27
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    • 2008
  • The completion ('initiation' de facto) of the KASI Orbit Propagator and Estimator (KASIOPEA) has been delayed for several reasons unfortunately. Due to the lack of working staffs and the Division priority rearrangement, the initial plan was dismantled and ignored for many years. However, fundamental researches regarding the essential parts of KASIOPEA has been done by author. The numerical integration module of the KASIOPEA is the most sensitive part in the precision of the final output in general. There is no silver bullet in the numerical integration in an orbit propagation as a non-stiff ODE case. Many numerical integration method like single-step methods, multi-step method, and extrapolation methods have been used in overly populated orbit propagator or estimator. In this study, several popular methods from single-step, multi-step, and extrapolation methods have been tested in numerical accuracy and stability.

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Numerical Analysis Methods for Heat Flow in Fire Compartment (화재실의 열유동 해석을 위한 수치 해석 방법)

  • Kim, Gwang-Seon;Son, Bong-Se
    • Fire Protection Technology
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    • pp.20-23
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    • 1994
  • This article investigates the different numerical methods, which are widely used for purpose of simulating a fire compartment the particular numerical methods such as finite difference, finite element, control Volume, and finite analysis are discribed in order to understand basic concepts and their applications. The fire simulations using fferent methods for the different physical geometrics have been reported in many recent literatures The convergence rate, the accuracy, and the stability are no simply dependent upon the specific method, The study of popular nu-merical methods by being compared among those is therefore significant to understand the nu-merical simulation of fire compartment.

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NUMERICAL ANALYSIS OF LEGENDRE-GAUSS-RADAU AND LEGENDRE-GAUSS COLLOCATION METHODS

  • CHEN, DAOYONG;TIAN, HONGJIONG
    • Journal of applied mathematics & informatics
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    • v.33 no.5_6
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    • pp.657-670
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    • 2015
  • In this paper, we provide numerical analysis of so-called Legendre Gauss-Radau and Legendre-Gauss collocation methods for ordinary differential equations. After recasting these collocation methods as Runge-Kutta methods, we prove that the Legendre-Gauss collocation method is equivalent to the well-known Gauss method, while the Legendre-Gauss-Radau collocation method does not belong to the classes of Radau IA or Radau IIA methods in the Runge-Kutta literature. Making use of the well-established theory of Runge-Kutta methods, we study stability and accuracy of the Legendre-Gauss-Radau collocation method. Numerical experiments are conducted to confirm our theoretical results on the accuracy and numerical stability of the Legendre-Gauss-Radau collocation method, and compare Legendre-Gauss collocation method with the Gauss method.

Assessments of dissipative structure-dependent integration methods

  • Chang, Shuenn-Yih
    • Structural Engineering and Mechanics
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    • v.62 no.2
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    • pp.151-162
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    • 2017
  • Two $Chang-{\alpha}$ dissipative family methods and two $KR-{\alpha}$ family methods were developed for time integration recently. Although the four family methods are in the category of the dissipative structure-dependent integration methods, their performances may be drastically different due to the detrimental property of weak instability or overshoot for the two $KR-{\alpha}$ family methods. This weak instability or overshoot will result in an adverse overshooting behavior or even numerical instability. In general, the four family methods can possess very similar numerical properties, such as unconditional stability, second-order accuracy, explicit formulation and controllable numerical damping. However, the two $KR-{\alpha}$ family methods are found to possess a weak instability property or overshoot in the high frequency responses to any nonzero initial conditions and thus this property will hinder them from practical applications. Whereas, the two $Chang-{\alpha}$ dissipative family methods have no such an adverse property. As a result, the performances of the two $Chang-{\alpha}$ dissipative family methods are much better than for the two $KR-{\alpha}$ family methods. Analytical assessments of all the four family methods are conducted in this work and numerical examples are used to confirm the analytical predictions.