• Title/Summary/Keyword: 수치진동

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Numerical analysis of the vortex induced vibration of the 2-D cylinder using dynamic deforming mesh (동적격자변형기법을 이용한 2차원 실린더의 와류유발진동에 대한 수치해석)

  • Lee, Namhun;Baek, Jiyoung;Lee, Seungsoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.1
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    • pp.1-9
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    • 2013
  • In this paper, numerical simulations are performed on the lock-in phenomena of vortex induced vibration(VIV) of a two dimensional cylinder. A deforming grid as well as a rigidly moving grid are used to simulate the movement of the cylinder. The grid deformation is accomplished by the linear spring analogy. Converged solutions, which are obtained by controling the grid size and the non-dimensional time step, are used for comparison and validation of the analysis results. Moreover, the efficiency and the accuracy of the coupling methods for fluid-structure interaction are examined.

Prediction of Thermo-acoustic Oscillation Characteristics in a Ducted Combustor (관형 연소기의 열-음향 진동에 의한 소음 특성 예측)

  • 김재헌;이정한;이수갑;정인석
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.7
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    • pp.56-66
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    • 1999
  • Thermoacoustic oscillation is a significant problem in cylindrical-type combustors such as common internal combustion engines, industrial furnaces, gas turbine, etc. This kind of low frequency oscillation can lead to serious consequences such as destruction of the combustor and production of strong noise. The accurate numerical simulation of thermoacoustic phenomena is a complex and challenging problem, especially when considering the chemical reaction of mixtures. As with other simulations of aerodynamics and aeroacoustics, the direct computation of thermoacoustic phenomena requires that Navier-Stokes equations be solved using accurate numerical differentiation and time-marching schemes, with non-reflecting boundary conditions. The numerical approach used here aims at qualitative analysis and efficient prediction of those problems, not at the development of an accurate scheme. The numerical prediction developed in this work is shown to be reasonably matched with experimental result.

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Numerical Analysis of Free Vibration of Parabolic Arches with Hinged Ends (양단(兩端)힌지 포물선(抛物線)아치의 자유진동(自由振動)에 관한 연구(研究))

  • Hwang, Hak Joo;Lee, Byoung Koo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.4 no.1
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    • pp.69-77
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    • 1984
  • In this paper, the governing differential equations for the free vibration of uniform parabolic arches are derived on the basis of equilibrium equations of a small element of arch rib and the D'Alembert principle. A trial eigen value method is used for determining the natural frequencies and mode shapes. And the Runge-Kutta fourth order integration technique is also used in this method to perform the integration of the differential equations. A detailed study is made of the first mode for the symmetrical and anti-symmetrical vibrations of hinged arches with the Span length equal to 10 m. The effects of the rise of arch, the radius of gyration and the rotary inertia on free vibrations are presented in detail in curves and table.

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Control of the Pressure Oscillations in Supersonic Cavity Flows (초음속 공동유동에서 발생하는 압력변동의 제어)

  • Lee Young-Ki;Jung Sung-Jae;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.117-120
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    • 2005
  • The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

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A predictor-corrector algorithm of the generalized-$\alpha$ method for analysis of structural dynamics (동적해석을 위한 일반화된$\alpha$ 방범의 예측 수정자 알고리즘)

  • ;Hulbert, Gregory M.
    • Journal of KSNVE
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    • v.5 no.2
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    • pp.207-213
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    • 1995
  • A new predictor-corrector explicit time integration algorithm is presented for solving structural dynamics problems. The basis of the algorithm is the implicit generalized-.alpha. method recently developed by the authors. Like its implicit parent, the explicit generalized-$\alpha$ method is a one- parameter family of algorithms in which the parameter defines the high-frequency numerical dissipation. The algorithm can be utilized effectively for linear and nonlinear structural dynamics calculations is which numerical dissipation is needed to reduce spurious oscillations inherent in non-dissipative time integration methods used to solve wave propagation problems.

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A Note on the Proper Size of a Finite Element for Analysis of Harbor Resonance Problems (항만부진동 해석을 위한 적정 유한요소 크기에 대한 소고)

  • 정원무;박우선
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.1
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    • pp.86-93
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    • 2002
  • In this study, numerical experiments were performed to decide the proper size off finite element for the analysis of harbor resonance problems. Various sizes of finite elements were considered from 1/3 to 1/60 of wavelength to model a fully opened rectangular harbor. Through the numerical results, the proper number of finite elements per wavelength were revealed to be nine within two percents errors allowed in resonant period and amplification ratio, while twelve within one percent error. It was fecund that error rates of resonant periods decrease linearly, while those of amplification ratio decrease with oscillating form as the size of an element decreases. The error of amplification ratio increases more rapidly than that of resonant period in case of element numbers below nine.

Analysis of Vibration Velocity Behavior of Rock Slope in Rock Blasting by Three-Dimensional Numerical Analysis (3차원 수치해석을 통한 암반 발파 시 암반 사면의 진동속도 거동 분석)

  • Chang-Young Park;Jae-Young Heo;Yong-Jin Kim;Seung-Joo Lee;Young-Seok Kim;Ji-Hoon Kim;Yong-Seong Kim
    • Journal of the Korean Geosynthetics Society
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    • v.22 no.3
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    • pp.71-86
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    • 2023
  • Rock blasting tests using underground penetration-type displacement sensors were conducted, and three-dimensional finite element numerical analyses were performed to assess their applicability and mitigate slope hazards during rock blasting. Additionally, parameters influencing vibration velocity were investigated during the tests. The results confirmed that underground penetration-type displacement sensors are suitable for monitoring rock slope behavior, and the numerical analyses revealed that the most influential parameter on vibration velocity during rock blasting is the unit weight. Furthermore, it was observed that vibration velocity decreases significantly with distance from the blast source, and proximity to the source leads to substantial variations in vibration velocity due to differences in elastic modulus and unit weight. Changes in internal friction angle and adhesive strength had minimal impact.

Multilphase Flow in Heterogeneous Groundwater Systems (이질적 지하수계에서 다상흐름)

  • 최우희;선우중호
    • Proceedings of the Korea Water Resources Association Conference
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    • 1992.07a
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    • pp.504-505
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    • 1992
  • 이질적 지하수계에서 물과 DNAPL(dense nenaqueous phase liquids)의 동시적 움직임을 연구하기 위한 수직단면 2차원 유한요소모형이 개발되었다. 물과 DNAPL의 흐름방정식은 비포화 영역 뿐만 아니라 연속적으로 모사하기 위하여 유체 압력항으로 형식화하였다. 이들 지배방정식의 비선형성을 다루기 위하여 mass lumping과 수정 Picard 기법이 이용되었고, 수치진동과 분산을 줄이기 위하여 전방가중이 사용되었다. 본 수치모형의 검증은 중력과 모세관 효과를 모두 고려한 McWhoter와 Sudana(1990)의 해석해와 비교함으로써 행하였다. 또한 수치모형의 타당성 검토의 연구는 진행되고 있다.

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Numerical study on impact noise control of PC slab coupled with viscoelastic material (점탄성재료가 결합된 PC슬래브의 바닥충격음 제어에 관한 수치해석 연구)

  • Hwang, Jae-Seung;Hong, Gun-Ho;Park, Hong-Geun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1160-1166
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    • 2007
  • In this study, a new slab system that adjoint precast slabs are connected each other by viscoelastic material is proposed and numerical analysis is performed to evaluate the effect of the slab system on the vibration and noise control. Substructuring is introduced to develope the equation of motion of the slab system and the optimal properties of viscoelastic material are calculated. For the performance evaluation of the new slab system, the sound power and acceleration of the slab are compared with those of two way slab and the slab which the viscoelastic material is not connected. Numerical results show that the sound power of the new slab system can be reduced an amount of 6dB.

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Semi-Active Control of Wind-Induced Vibration of Tall Building Using Magneto-Rheological Dampers (자기유변유체댐퍼를 이용한 대형 구조물의 풍하중에 대한 반능동 제어)

  • 윤정방;구자인;김상범;전준보
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.72-77
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    • 2001
  • 고층 빌딩의 풍하중에 의한 진동을 제어하기 위하여 MR 유체감쇠기를 이용한 반능동 제어 시스템의 설계에 대하여 연구하였다. 제안된 설계기법의 효율성을 검증하기 위하여 ASCE benchmark 구조물을 대상으로 수치 모의 해석을 수행하였다. 유전자 알고리즘을 사용하여 MR 감쇠기의 76층 빌딩 내에서의 최적위치와 용량을 결정하였으며, clipped optimal control 제어기법을 사용하여 가속도 되먹임 구조를 갖는 MR 감쇠기의 제어 알고리즘을 구성하였다, 수치 모의 해석 결과로부터 MR 감쇠기는 ATMD와 유상한 제어 성능을 가지고 있으며 매우 작은 규모의 파워 시스템만으로 운영이 가능한 효율적이고 안정적인 제어 시스템임을 확인할 수 있었다.

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