• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.359-362
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• 2009

Damping characteristics of pressure oscillation induced by an orifice in fluid feeding line for are investigated numerically and experimentally. Assuming small pressure oscillation, acoustic damping effect of orifice is confirmed experimentally, and with the mean flow, damping characteristics of an orifice are investigated numerically. When an orifice is installed at the node of pressure oscillation corresponding to the anti-node of velocity oscillation, suppression of pressure oscillation is maximized and with the mean flow, the resonant frequency is decreased. And, it is found that the optimal position of an orifice for damping shouled be changed.

• Journal of Korean Association for Spatial Structures
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• v.6 no.1 s.19
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• pp.65-73
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• 2006

In these days the floor vibration is beginning to make its appearance of the environmental dispute in dwelling building. Standard floor system are suggested for the settlement of this issue by government. The sound of floor impact sound is needed to secure comfortable quality in housing. Also, it is required an accurate analysis and a proper evaluation for floor vibration. Refine model is necessary for the floor system of housing to analyze accurately the floor vibration. But this refine model is not efficient because it is required so much running time for vibration analysis and it is difficult of modeling of standard floor slab. In this paper, new modeling methods of standard floor slab are proposed for the accurate rigidity evaluation. By using the new modeling method, the accurate vibration response can be obtained and can accurately evaluate the rigidity of standard floor system with resilient materials. Therefore the proposed modeling method is of practical use for vibration analysis of floor system of housing.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.629-638
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• 2002

This paper deals with the free vibration analysis of compressive tapered members resting on elastic foundation using the Differential Quadrature Method. Based on the differential equation subjected to the boundary conditions, adopted from the open literature, which governs the free vibrations of such member, this equation is applied to the Differential Quadrature Method. For computing natural frequencies, the numerical procedures are developed by QR Algorithm, in which the Chebyshev-Gauss-Lobatto method is used for choosing the grid points. The numerical methods developed herein for computing natural frequencies are programmed in FORTRAN code, and all solutions obtained in this study are quite agreed with those in the open literature.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.39-48
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• 2011

The paper describes four practical cases of railway structure concerning a three-dimensional numerical approach to analyse dynamic soil-structure interaction(SSI)of railway tracks on layered soil under transient load in the time domain. The SSI-Model has been implemented in TDAPIII accounting for nonlinear properties of the track and soil. The approach can be also be used to calculate vibration propagation in the soil and its effect on nearby buildings and structure. The Method is applied to analyse the dynamic response of railway tracks due to a moving wheel set. Finally some sample are given in order to reduce the vibration at the point of emission, at the transmission path and the structure itself.

• Journal of Energy Engineering
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• v.13 no.4
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• pp.275-280
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• 2004

Augmentation of heat transfer by ultrasonic vibration in pipes are investigated. Measurements of convective heat transfer coefficients on circular pipe walls are made with and without ultrasonic vibration applied to water. These data are compared with each other to quantify the effects of ultrasonic vibration on heat transfer enhancement. Numerical analysis has been also performed in order to extend the ranges of examined temperature and flow rate. FLUENT Ver.6.1 is used to simulate velocity and temperature fields and evaluate heat transfer coefficient with and without ultrasonic vibration. The results show that the ultra- sonic vibration enhances the Nusselt number of forced convection flow and the increase rate strongly depends on flow rate.

• Journal of the Korean Geosynthetics Society
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• v.18 no.3
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• pp.69-77
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• 2019

This paper presents a new analytical model for estimating the free vibration of tapered friction piles. The governing differential equation for the free vibration of statically axially-loaded piles embedded in non-homogeneous soil is derived. The equation is numerically integrated by the Runge-Kutta method, and then the eigenvalue of natural frequency is determined by the Regula-Falsi scheme. For a cylindrical non-tapered pile, the computed natural frequencies compare well with the available data from literature. Numerical examples are presented to investigate the effects of the tapering, the skin friction resistance, the end condition of the pile, the vertical compressive loading, and the soil non-homogeneity on the natural frequency and mode shape of tapered friction piles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.247-252
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• 1997

축어긋남이 있는 회전체-볼베어링계의 진동을 묘사할 수 있는 모델을 개발하였다. 이 모델은 축어긋남의 효과로서 커플링과 베어링에 작용하는 힘과 모멘트, 그리고 이에 의한 변형을 고려하였으며, 실험과 수치해석 결과로부터 모델의 타당성을 검증하였다. 그 결과는 각축어긋남이 심해짐에 따라 타원 형태의 선회궤적을 보여주며, 어긋남방향의 회전체 고유진동수와 베어링 강성계수가 크게 증가하는 것으로 나타났다. 그리고 이러한 현상은 어긋남 방향의 베어링 모멘트 강성증가에 의한 것으로 밝혀졌다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.46-54
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• 2003

The purpose of this study is to analyze the phenomena of the thermally-induced vibration for the flexible space structure due to abrupt change of radiation heating circumstance using the numerical analyze and experiment test. In order to verify this structure, numerical approaches on the simplified flexible tube were compared with experimental test results at the ground experimental facility. In this analyze, it was found that the thermal deformation occurs firstly due to fast radiation heating of flexible structure and then the thermally-induced vibration would be induced due to small periodic change of temperature. According to comparison of numerical and experimental results, in case of no tip mass, the first mode vibration by the numerical analyze was a.78Hz same as that of the experimental result. However in case of increase tip-masses of 8g, 16g, 50g and 100g, the first modes vibration theoretical analyze were 1.75Hz, I.3Hz, a.87Hz and 0.73Hz, in decrease trend respectively and those by experimental test were 2.34Hz, 1.5Hz, 0.78Hz and 0.78Hz in decrease trend respectively. Although using the simpled equation for the estimation, the estimation results were similar to experimental results.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.69-78
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• 2009

Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

• Journal of Korea Water Resources Association
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• v.34 no.2
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• pp.177-186
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• 2001

By using he total variation diminishing (TVD) condition, accurate and upwind based schemes are firstly introduced to develop numerical models free from nonphysical oscillations in the vicinity of large gradients. These models are then applied to both abruptly and smoothly varying initial conditions. By comparing computed predictions to analytical solutions, it is clearly shown that the first-order upwind scheme produces the numerical viscosity and the second-order Lax-Wendroff scheme produces the spurious oscillations. However, the TVD scheme gives the most reasonable results.