• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.177-184
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• 2002

Large amplitude sloshing can occur in contained fluid region due to the seismic ground motion. Also, The pressure by large amplitude sloshing damages the connections between the wall and roof of a fluid container and causes outflow of contained fluid. Therefore, to predict the dynamic behavior accurately, three dimensional analysis with the nonlinear boundary condition must be performed. In this study, the numerical solution procedure is developed using the boundary element method with the Lagrangian particle approach. In order to demonstrate the accuracy and validity of the developed method, the fluid motion for a free oscillation with small amplitude and a forced vibration are analyzed. And the numerical results are compared with the linear theory results and the previous studies with the nonlinear boundary condition.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.44-51
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• 1992

This paper is concerned with the propram of the automatic mesh generation for 2-dimensional domain which contains the curved boundaries and holes. This program treats a new vertical-line drawing method. This method starts with 4-subdivisions of problem domain and the classification of the cross points of grid lines and boundaries. The new node is generated by the vertical line to the line connecting the two intersections of a boundary and two grid lines in gereral. And the node very close to the boundary is moved to the boundary. The automatic mesh generation composed of only rectangular elements is achieved by this procedure. The boundaries are piecewise-curves composed of lines, circles, arcs, and free curves. The free curves are generated by B-Spline form. Although there were some bad elements for the complex boundary, it was possible to obtain the acceptible rectangular elements for the given boundaries.

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.555-561
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• 2001

A new approach to analyze the multi-domain acoustic system divided and enclosed by flexible structures is presented in this paper. The boundary element formulation of the Helmholtz integral equation is used for the internal fields and the finite element formulation for the structures surrounding the fields. We developed a numerical analysis program for the structural-acoustic coupling problems of the multi-domain system, in which boundary conditions such as the continuity of normal particle velocity and sound pressure in the structural interfaces between Field 1 and Field 2 are not needed. The validity of the numerical analysis program is verified by comparing the numerical results with the experimental ones. Example problems are included to investigate the characteristics of the coupled multi-domain system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.189-196
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• 1990

In the present study, a new method of generating boundary-fitted coordinates systems controlled by control function is introduced. Application of the method to a three-dimensional simply-connected region is the demonstrated. The numerical grid generation has following feat ures, (a) The generated boundary fitted coordinates is well concentrated in near wall region and satisfied orthogonality, (b) The grid control function is fully automatic and well controlled in sharp convex boundary.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.443-447
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• 2003

The BEM (Boundary Element Method) is a computational technique for the approximate solution of problems in continuum mechanics. In the BEM both volume and surface integrals transformed into boundary integral equations. So, we applied the ECM (Electrochemical Machining) process to boundary problem, because our focus is only deformed shape. The ECM process is modeled as a two-dimensional problem assuming constant properties of electrolyte, and an incremental formulation is used with automatic mesh regeneration. As a result the final shape is roughly agreed with experimental shape. But, it has an error of exact shape, because a chemically factor is not considered

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.11-21
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• 2004

In this paper, an active vibration control of a tensioned elastic axially moving string is investigated. The dynamics of the translating string ale described by a non-linear partial differential equation coupled with an ordinary differential equation. The time varying control in the form of the right boundary transverse motions is suggested to stabilize the transverse vibration of the translating continuum. A control law based on Lyapunov's second method is derived. Exponential stability of the translating string under boundary control is verified. The effectiveness of the proposed controller is shown through the simulations.

• Korean Journal of Mathematics
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• v.21 no.2
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• pp.117-124
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• 2013

We investigate the existence of weak solutions for the biharmonic boundary value problem with nonlinear term decaying at the origin. We get a theorem which shows the existence of nontrivial solutions for the biharmonic boundary value problem with nonlinear term decaying at the origin. We obtain this result by reducing the biharmonic problem with nonlinear term to the biharmonic problem with bounded nonlinear term and then approaching the variational method and using the mountain pass geometry for the reduced biharmonic problem with bounded nonlinear term.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1873-1880
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• 1994

Fully developed turbulent flow in a circular pipe and laminar boundary layer on a flat plate were measured to develop a measuring technique of the wall sheat stress using Preston tubes. New empirical formulas to extimate displacement factor of Preston tube obtained through the present study. The displacement factor for turbulent flow was considerably different from that for the laminar flow. Measured wall shear stress was not pretty dependent on the displacement factor for Preston tubes in the inertia sublayer of turbulent boundary layer, however was considerably affected in the laminar boundary layer. Measuring error of skin friction using the CPM technique was 3% for turbulent and 5% for thin laminar boundary layers.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1966-1971
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• 2003

Matching inviscid and boundary layer methods are developed for hypersonic flow with thick boundray layer. The new equations match all the boundary layer properties with a variation in the inviscid solution near the edge, except for the normal velocity. Computational comparison are performed for incompressible and compressible flows over a flat plate. Results from the present method are compared with Navier-Stokes solutions. The present results are in good agreement with Navier-Stokes solutions. They show that the new technique can provide improved heating rates and skin friction predictions for preliminary design of vehicles where shear layers and entropy layer swallowing are important.

• Computers and Concrete
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• v.2 no.2
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• pp.111-123
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• 2005

The ductility of reinforced concrete bearing walls subjected to high axial loading and moment can be enhanced by improving the deformability of the compression zone or by reducing the neutral axis depth. The current state-of-the-art procedure evaluating the confinement effect prompts a consideration of the spaces between the transverse and longitudinal reinforcing bars, and a provision of tie bars. At the same time, consideration must also be given to the thickness of the walls. However, such considerations indicate that the confinement effect cannot be expected with the current practice of detailing wall ends in Korea. As an alternative, a comprehensive method for dimensioning boundary elements is proposed so that the entire section of a boundary element can stay within the compression zone when the full flexural strength of the wall is developed. In this comprehensive method, the once predominant code approach for determining the compression zone has been advanced by considering the rectangular stress block parameters varying with the extreme compression fiber strain. Moreover, the size of boundary elements can also be determined in relation to the architectural requirement.