• Title/Summary/Keyword: Wavenumber finite element method

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Application of Wavenumber-TD approach for time harmonic analysis of concrete arch dam-reservoir systems

  • Lotfi, Vahid;Zenz, Gerald
    • Coupled systems mechanics
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    • v.7 no.3
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    • pp.353-371
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    • 2018
  • The Wavenumber or more accurately Wavenumber-FD approach was initially introduced for two-dimensional dynamic analysis of concrete gravity dam-reservoir systems. The technique was formulated in the context of pure finite element programming in frequency domain. Later on, a variation of the method was proposed which was referred to as Wavenumber-TD approach suitable for time domain type of analysis. Recently, it is also shown that Wavenumber-FD approach may be applied for three-dimensional dynamic analysis of concrete arch dam-reservoir systems. In the present study, application of its variation (i.e., Wavenumber-TD approach) is investigated for three-dimensional problems. The method is initially described. Subsequently, the response of idealized Morrow Point arch dam-reservoir system is obtained by this method and its special cases (i.e., two other well-known absorbing conditions) for time harmonic excitation in stream direction. All results for various considered cases are compared against the exact response for models with different values of normalized reservoir length and reservoir base/sidewalls absorptive conditions.

Vibration of Pipes Coupled with Internal and External Fluids (내부 및 외부 유체와 연성된 파이프의 진동 해석)

  • Ryue, Jung-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.3
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    • pp.142-150
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    • 2012
  • The waveguide finite element (WFE) method is a useful numerical technique to investigate wave propagation along waveguide structures which have uniform cross-sections along the length direction ('x' direction). In the present paper, the vibration and radiated noise of the submerged pipe with fluid is investigated numerically by coupling waveguide finite elements and wavenumber boundary elements. The pipe and internal fluid are modelled with waveguide finite elements and the external fluid with wavenumber boundary elements which are fully coupled. In order to examine this model, the point mobility, dispersion curves and radiated power are calculated and compared for several different coupling conditions between the pipe and internal/external fluids.

The Characteristic of Radiation Efficiency from Harmonic-excited Cylindrical Radiator (조화 가진에 의한 원통형 음향 방사기의 방사 효율 특성)

  • 김관주;최승권
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.516-523
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    • 1998
  • Radiation efficiency of a cylindrical shell whose surface vibrates under harmonic distribution is investigated by theoretical solutions and Boundary Element Method. The vibration modes of a cylindrical shell is determined from experiment and is compared with the result of Finite Element Method. Harmonic vibration response of the cylindrical shell under the point excitation and the radiation phenomena from its response is analyzed by Finite Element Method and Boundary Element Method.

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Vibration Analysis for Infinite Length Waveguide Structures Connected with Finite Length Structures Using Impedance Coupling (유한 길이 구조물과 무한 길이 도파관 구조물의 임피던스 연성을 이용한 진동 해석)

  • Ryue, Jungsoo;Lee, Jaehong;Hong, Chinsuk;Shin, Ku-Kyun
    • The Journal of the Acoustical Society of Korea
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    • v.34 no.5
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    • pp.360-370
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    • 2015
  • In case that an infinite length waveguide structure is connected with a finite length structure, it is required to combine a wave approach for the waveguide structure and a modal approach for the finite length structure to investigate the dynamic response of the connected target structure. In this study, the wavenumber finite element (WFE) analysis is adopted for the infinite length waveguide substructure and a finite element (FE) method is applied for the finite length substructure and then their results are coupled in terms of the impedance or mobility at the connected points between the substructures. As a structural model, an infinite length cylindrical shell with a rectangular plate inside is regarded. These two substructures are connected at the four corner points of the plate, rigidly or resiliently. From this investigation, it was confirmed that the wave approach (WFE method) and modal approach (FE method) can be combined by the impedance coupling.

Dynamic analysis of concrete gravity dam-reservoir systems by wavenumber approach in the frequency domain

  • Lotfi, Vahid;Samii, Ali
    • Earthquakes and Structures
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    • v.3 no.3_4
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    • pp.533-548
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    • 2012
  • Dynamic analysis of concrete gravity dam-reservoir systems is an important topic in the study of fluid-structure interaction problems. It is well-known that the rigorous approach for solving this problem relies heavily on employing a two-dimensional semi-infinite fluid element. The hyper-element is formulated in frequency domain and its application in this field has led to many especial purpose programs which were demanding from programming point of view. In this study, a technique is proposed for dynamic analysis of dam-reservoir systems in the context of pure finite element programming which is referred to as the wavenumber approach. In this technique, the wavenumber condition is imposed on the truncation boundary or the upstream face of the near-field water domain. The method is initially described. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by this approach, and the results are compared against the exact response. Based on this investigation, it is concluded that this approach can be envisaged as a great substitute for the rigorous type of analysis.

Numerical Analysis of Rail Noise Regarding Surface Impedance of Ground by Using Wavenumber Domain Finite and Boundary Elements (지면 임피던스를 고려한 레일 방사 소음의 파수영역 유한요소/경계요소 해석)

  • Ryue, Jungsoo;Jang, Seungho
    • Journal of the Korean Society for Railway
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    • v.18 no.4
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    • pp.289-300
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    • 2015
  • An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In conventional approaches to predicting rail noise, the rail is regarded as placed in a free space so that the reflection from the ground is not included. However, in order to predict rail noise close to the rail, the effect of the ground should be contained in the analysis. In this study the rail noise reflected from the ground is investigated using the wavenumber domain finite element and boundary element methods. First, two rail models, one using rail attached to the rigid ground and one using rail located above rigid ground, are considered and examined to determine the rigid ground effect in terms of the radiation efficiency. From this analysis, it was found that the two models give considerably different results, so that the distance between the rail and the ground is an important factor. Second, an impedance condition was set for the ground and the effect of the ground impedance on the rail noise was evaluated for the two rail models.

Vibration of Beams Induced by Wall Pressure Fluctuation in Turbulent Boundary Layer Using Numerical Approaches (수치 해석을 이용한 난류 경계층 내 벽면 변동 압력을 받는 보의 진동 해석)

  • Ryue, Jungsoo;Kim, Eunbi
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.8
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    • pp.698-706
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    • 2013
  • Structural vibration induced by excitation forces under turbulent boundary layer is investigated in terms of the numerical analysis in this paper. Since the responses of structures excited by the wall pressure fluctuation(WPF) are described by the power spectral density functions, they are calculated and reviewed theoretically for finite and infinite length beams. For the use of numerical approaches, the WPF needs to be discretized but conventional finite element method is not much effective for that purpose because the WPF lose the spatial correlation characteristics. As an alternative numerical technique for WPF modelling, a wavenumber domain finite element approach, called waveguide finite element method, is examined here for infinite length beams. From the comparison between the numerical and theoretical results, it was confirmed that the WFE method can effectively and easily cope with the excitation from WPF and hence the suitable approach.

Prediction of acoustic radiation efficiency for trapezoidal corrugated plates (사다리꼴 주름평판의 음향방사효율 해석)

  • Jungsoo Ryue;Seungho Jang
    • The Journal of the Acoustical Society of Korea
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    • v.42 no.2
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    • pp.83-93
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    • 2023
  • Trapezoidal corrugated plates are often treated as orthotropic plates to simplify the modelling of the corrugation. However, this simplification is not valid at high frequencies in which the localized vibration within the parts of corrugation takes place. In this study, the vibrational and acoustical characteristics of corrugated plates are investigated up to high frequencies by means of the wavenumber domain numerical approach. Based on the findings from this numerical analysis, an approximate method to predict vibro-acoustic characteristics of corrugated plates is proposed. This approximate model consists of four equivalent plates which can represent global and local behaviours of corrugated plates. The radiation efficiency of corrugated plates is predicted from the approximate model and validated through the comparison with those of the numerical method.

Three Dimensional Dynamic Interaction of Foundations on Layered Half-Space (3차원 다층 반무한상 구조물의 동적 간섭에 관한 해석적 연구)

  • 조우연;이강원;임윤묵;김문겸
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.09a
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    • pp.75-82
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    • 2001
  • A dynamic interaction analysis of an adjacent surface fecundation on a layered half-space is performed in the frequency domain. A semi-analytical approach is employed to reduce the integration range of the wavenumber in the surface fundamental solution for a layered half-space in boundary element (BE) formulations. The present study then adopts a combined boundary and finite element method to analyze the dynamic behavior of a system of flexible surface foundations on an elastic homogeneous and layered half-space. Numerical examples are presented to demonstrate the accuracy of the developed method. The examples show the feasibility of an extended application fur the complicated dynamic interaction of foundations on layered media.

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Development of numerical method to predict broadband radiation noise resulting in fluid-induced vibration and acoustic-induced vibration of pipe (배관의 유동 유발 진동 및 음향 유발 진동 기인 광대역 방사 소음 예측을 위한 수치 해석 기법 개발)

  • Sangheon Lee;Cheolung Cheong;Songjune Lee
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.1
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    • pp.112-121
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    • 2024
  • The pipping system is widely used in many industries as equipment for transporting fluids over long distances. In high-pressure pipe, as the speed of the fluid increases, a loud noise is generated. Therefore, various studies have been conducted to reduce pipe noise. In this paper, a pipe noise analysis was developed to predict and quantitatively assess the flow-induced vibration and acoustic-induced vibration due to valve flow in high-temperature and high-pressure. To do this, a high-fidelity fluid analysis technique was developed for predicting internal flow in the pipe with valve. In additional, the contribution of compressible/incompressible pressure by frequency band was evaluated using the wavenumber-frequency analysis. To predict a low/middle frequency pipe noise, the vibroacoustic analysis method was developed based on Finite Element Method (FEM). And the pipe noise prediction method for the middle/high frequency was developed based on Statistical Energy Analysis (SEA).