• Title/Summary/Keyword: boundary condition

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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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Application of Rigid Lid Boundary Condition for Three Dimensional Flow Analysis beneath Floating Structure (부유체하부의 3차원 흐름해석을 위한 Rigid lid 경계조건의 적용)

  • Hong, Nam-Seeg
    • Journal of Ocean Engineering and Technology
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    • v.26 no.5
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    • pp.55-62
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    • 2012
  • In this paper, the rigid lid boundary condition is applied to simulate the influence of floating structures such as ships or pontoons, and the pressure term in both the momentum equations and continuity equation are modified. The pressure of a floating structure under the free surface is dependent on the draft of the structure, generally called a ship. If the free surface is covered by a floating structure, the free surface cannot move freely. The water level should be fixed, using a rigid lid boundary condition. This boundary condition is implemented by reducing the storage area of the grid cell with a factor between zero and one. The numerical model developed by Hong (2009) is verified through a comparison with experimental results, and the influence of the reduction factor is investigated using the verified numerical model.

ACCURACY IMPROVEMENT OF THE BLEED BOUNDARY CONDITION WITH THE EFFECTS OF POROSITY VARIATIONS AND EXPANSION WAVES (다공도 및 팽창파의 영향을 고려한 BLEED 경계조건 수치 모델링의 정확도 향상 연구)

  • Kim, G.;Choe, Y.;Kim, C.
    • Journal of computational fluids engineering
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    • v.21 no.1
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    • pp.94-102
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    • 2016
  • The present paper deals with accuracy improvement of a bleed boundary condition model used to improve the performance of supersonic inlets. In order to accurately predict the amount of bleed mass flow rates, this study performs a scaling of sonic flow coefficient data for 90-degree bleed holes in consideration of Prandtl-Meyer expansion theory. Furthermore, it is assumed that porosity varies with stream-wise location of the porous bleed plate to accurately predict downstream boundary layer profiles. The bleed boundary condition model is demonstrated through Computational Fluid Dynamics(CFD) simulations of bleed flows on a flat plate with/without an oblique shock. As a result, the bleed model shows the improved accuracy of bleed mass rates and downstream boundary layer profiles.

The Analysis of Lossy Dielectric using Surface Impedance Boundary Condition (표면 임피던스 경계조건을 이용한 손실유전체 해석)

  • Kim, Byung-Chan;Kim, Che-Young
    • Proceedings of the KIEE Conference
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    • 1996.07c
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    • pp.1744-1746
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    • 1996
  • Surface impedance boundary condition(SIBC) concepts are introduced into the finite-difference time-domain(FDTD) method. Lossy conductors are replaced by surface impedance boundary computations reducing the soluton space and producing significant computational savings. Specifically, a surface impedance boundary condition is developed to reduce a lossy dielectric half-space. Since Maxwell's eqations are solved directly, the reflected and transmitted pulse amplitude demonstrate how the reflection and transmision coefficient determine reflected wave amplitude. In this paper, two implementations of reflection coefficient are presented. One implementation is a standard FDTD technique and the other is a FDTD using surface impedence boundary condition(FDTD-SIBC) that are applicabIe over a very large frequency bandwidth. Particulary, an efficient way to transform the time domain results to frequency domain is presented. Thus, frequency domain results are presented in one dimension and are compared with exact results.

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Segregated finite element method by introducing a improved open boundary condition (개선된 개방경계조건을 도입한 분리유한요소법)

  • Oh, Seung-Hun;Min, Tae-Gee;Yoo, Jung-Yul
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.698-703
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    • 2000
  • In a computational fluid dynamics, the imposition of open boundary condition has an important part of the accuracy but it is not easy to find the optimal boundary rendition. This difficult is introduced by making artificial boundary in unbounded domairs. Such open boundary requires us to ensure the continuity of all primitive variables because the nature is in continuum. Here we introduce a revised well-conditioned open boundary condition particularly in FEM and apply it to various problems-entrainment, body force, short domains.

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Analysis of Connecting Rod Bearings Using Mass-Conserving Boundary Condition (유량 보존 경계 조건을 적용한 커넥팅 로드 베어링의 성능 해석)

  • 김병직;김경웅
    • Tribology and Lubricants
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    • v.14 no.3
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    • pp.39-45
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    • 1998
  • Reynolds equation, which describes behavior of fluid film in journal bearings, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power disspation which are important parameters in thermal analysis. In this paper, mass-conserving boundary condition was applied in the finite element analysis of connecting rod bearings. Lubricant flow rate and power dissipation rate were calculated together with journal center locus, minimum film thickness and maxmium film pressure. These computation results were compared with those of the case of Reynolds boundary condition. Balance between inlet and outlet flow rate was well achieved in the case of mass-conserving boundary condition.

EHL Analysis of Connecting Rod Bearings Using Mass-Conserving Boundary Condition (유량 보존 경계 조건을 적용한 커넥팅 로드 베어링의 EHL 해석)

  • 김병직;김경웅
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.04a
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    • pp.212-217
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    • 1998
  • Reynolds equation, which describes behavior of fluid film in journal bearing, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power dissipation which are important parameters in thermal analysis. Another important factor in the analysis of connecting rod bearing is elastic deformation of bearing support structure which is relatively flexible. In this paper, EHL analysis of connecting rod beating is performed using mass-conserving boundary condition. Elastic deformation of bearing support structure and application of mass-conserving boundary condition have significant effects on the performances of connecting rod bearing.

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Noise control of a slab using the laminated composite damping system (평판 부착형 제진시스템을 이용한 구조기인 소음 저감에 관한 연구)

  • Hwang, Jae-Seung;Kim, Gwang-Young;Hong, Geon-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.403-407
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    • 2009
  • It is reported that the heavy weight floor impact noise of a slab system is very sensitive to the location of microphone and impact load. In addition, it is known that the aspect raio, thickness and boundary condition of a slab also have great effect on the noise induced by impact load. However, the effect has been mainly evaluated by experimental test and numerical analysis is nearly performed to verify the effect quantitatively. In this study, the effect of the aspect ratio, thickness and boundary condition on the heavy weight floor impact noise is examined through numerical analysis for simple rectangular slab system. The results show that the thickness and boundary condition have a strong correlation with the noise of the slab, on the contrary, the aspect ratio has little relation with the noise.

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