• 한국전산유체공학회지
• /
• 제2권1호
• /
• pp.8-12
• /
• 1997

The three-dimensional Euler equations are solved numerically for the analysis of contraction flows in wind or water tunnels. A second-order finite difference method is used for the spatial discretization on the nonstaggered grid system and the 4-stage Runge-Kutta scheme for the numerical integration in time. In order to speed up the convergence, the local time stepping and the implicit residual-averaging schemes are introduced. The pressure field is obtained by solving the pressure-Poisson equation with the Neumann boundary condition. For the evaluation of the present Euler solver, numerical computations are carried out for three contraction geometries, one of which was adopted in the Large Cavitation Channel for the U.S. Navy. The comparison of the computational results with the available experimental data shows good agreement.

• Journal of Mechanical Science and Technology
• /
• 제14권2호
• /
• pp.159-167
• /
• 2000

A computational method for the dynamic analysis of a constrained mechanical system is presented in this paper. The partial velocity matrix, which is the null space of the Jacobian of the constraint equations, is used as the key ingredient for the derivation of reduced equations of motion. The acceleration constraint equations are solved simultaneously with the equations of motion. Thus, the total number of equations to be integrated is equivalent to that of the pseudo generalized coordinates, which denote all the variables employed to describe the configuration of the system of concern. Two well-known conventional methods are briefly introduced and compared with the present method. Three numerical examples are solved to demonstrate the solution accuracy, the computational efficiency, and the numerical stability of the present method.

• Journal of Ship and Ocean Technology
• /
• 제11권4호
• /
• pp.29-54
• /
• 2007

Systematic sensitivity analysis of smoothed particle hydrodynamics method (SPH), a gridless Lagrangian particle method, was carried out in this study. Unlike traditional grid-based numerical schemes, systematic sensitivity study for computational parameters is very limited for SPH. In this study, the effect of computational parameters in SPH simulation is explored through two-dimensional dam-breaking and sloshing problem. The parameters to be considered are the speed of sound, the type of kernel function, the frequency of density re-initialization, particle number, smoothing length and pressure extraction method. Through a series of numerical test, detailed information was obtained about how SPH solution can be more stabilized and improved by adjusting computational parameters.

• 한국안전학회지
• /
• 제28권1호
• /
• pp.57-62
• /
• 2013

Aerodynamic characteristics of cross section shape is an important parameter for the wind response and structural stability of long span bridges. Numerical simulation methods have been introduced to estimate the aerodynamic characteristics for more detailed flow analysis and cost saving in place of existing wind tunnel experiment. In this study, the computational fluid dynamics(CFD) simulation and large eddy simulation( LES) technique were used to estimate lift, drag and moment coefficients of four cross sections. The Strouhal numbers were also determined by the fast Fourier transform of time series of the lift coefficient. The values from simulations and references were in a good agreement with average difference of 16.7% in coefficients and 8.5% in the Strouhal numbers. The success of the simulations is expected to attribute to the practical use of numerical estimation in construction engineering and wind load analysis.

• Journal of applied mathematics & informatics
• /
• 제32권1_2호
• /
• pp.267-284
• /
• 2014

The multiresolution analysis for Legendre multiwavelets are given, anti-derivatives of Legendre multiwavelets are used for the numerical solution of differential equations, a special form of multilevel augmentation method algorithm is proposed to solve the disrete linear system efficiently, convergence rate of the Galerkin methods is given and numerical examples are presented.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1993년도 가을 학술발표회논문집
• /
• pp.207-215
• /
• 1993

With the aid of finite element method, this paper deals with the problem of structural response variability of transmission tower subjected to the spatial variability of material properties, Young's modulus herein. The spatial variability of material property are modeled as two-dimensional stochastic field which has an isotropic auto-correlation function. Response variability has been computed based on two numerical techniques, such as the Neumann expansion method in conjunction with the Monte Carlo simulation method. The results by these numerical methods are compared with those by the deterministic approach.

• Korean Journal of Mathematics
• /
• 제13권2호
• /
• pp.127-137
• /
• 2005

The objective of numerical analysis is to devise and analyze efficient algorithms or numerical methods for equations arising in mathematical modeling for science and engineering. In this article, we present some recent topics in computational mathematics, specially in the finite element method and overview the development of the mixed finite element method in the context of second order elliptic and parabolic problems. Multiscale methods such as MsFEM, HMM, and VMsM are included.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
• /
• pp.250-257
• /
• 1995

The properties of Tuned Liquid Damper are investigated theoretically. In this study, numerical model is a nonlinear model for a rectangular TLD under horizontal motion on the basis of the shallow water wave theory, where the damping of the liquid motion is included semianalytically. For TLD subjected to harmonic external force, the liquid motion of TLD is simulated. Analysis result is showed that liquid motion in TLD is strongli nonlinear even under small excitation.

• 한국전산유체공학회지
• /
• 제8권4호
• /
• pp.41-49
• /
• 2003

This study presents a numerical model to analyze dynamic thermal behavior of a hot chuck designed for flip-chip bonders. The hot chuck of concern is a heater which has been specifically developed for accomplishing high-speed and ultra-precision soldering. The characteristic features are radiative heat source and the heating tool made of a material of high thermal diffusivity. A physical modeling has been conducted for the network of heat transport. A simplified finite volume model is deviced to simulate time-dependent thermal behavior of the heating tool on which soldering is achieved. The reliability of the proposed numerical model is verified experimentally. A series of numerical tests illustrate the usefulness of the numerical model in design analysis.

• 한국정밀공학회지
• /
• 제12권3호
• /
• pp.32-41
• /
• 1995

In the analysis of metal forming processes by the finite element method, there are many numerical instabilities such as element locking, hourglass mode and shear locking. These instabilities may have a bad effect upon accuracy and convergence. The present work is concerned with improvement of stability and efficiency in two-dimensional rigid-plastic finite element method using various type of elemenmts and numerical intergration schemes. As metal forming examples, upsetting and backward extrusion are taken for comparison among the methods: various element types and numerical integration schemes. Comparison is made in terms of stability and efficiency in element behavior and computational efficiency and a new scheme of adaptive directional reduced integration is introduced. As a result, the finite element computation has been stabilized from the viewpoint of computational time, convergency, and numerical instability.