• 대한공업교육학회지
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• 제34권1호
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• pp.238-251
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• 2009

배열센서에 영향을 주는 자체소음은 그 시스템이 설치된 곳에서 발생하는 소음과 해양으로부터 들어오는 주변소음을 포함한 소음으로 정의된다. 수중에서의 탐지를 위한 배열 구조는 표면을 따라 발생되는 유체 유기소음에 많은 영향을 받는다. 본 논문에서는 곡면배열 음향 센서를 설계하기 위하여 유동유기 소음의 영향으로 인한 주파수 밀도 함수의 적분식의 주요 구성요소인 전달함수(transfer function)를 저파수 영역에서 수치해석 하였다. 난류 경계층에서 발생하는 유입 소음은 수정된 Corcos 모델을 이용하였다. 저파수 영역에서의 전달함수의 특성은 고정판의 두께와 밀도가 작아질수록 함수의 적분값은 적어지므로 소음의 영향은 줄어드는 것으로 나타났다. 또한 Corcos 벽면 압력과 전달함수의 곱에 따른 특성과 주파수 밀도 함수의 곱의 변화를 보였다. 향후 이러한 연구는 무인 잠수정에 탑재할 수 있는 곡면배열 센서의 설계에 응용이 가능하리라 판단된다.

• 소음진동
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• 제6권5호
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• pp.671-677
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• 1996

This paper presents the analytical method for predicting turbulence- induced noise in the multilayered cylinder composed of an outer hose, an inner fluid and an internal core. It is assumed that an infinite axisymmetric cylinder is located horizontally in water with free stream velocity and the turbulent boundary layer (TBL) surrounding the outer hose is fully developed and homogeneous. The transfer function at the core surface due to the propagation of the pressure fluctuation within the TBL is formulated using the linearized Navier-Stockes equation for solid and fluid. In the estimation of the energy spectrum of wall pressure fluctuation, the empirical formula proposed by Strawderman based on the Corcos model is used. A general algorithm for the calculation of the pressure level at the surface of a core, that is, turbulence- induced noise, is presented. Through the detailed numerical simulation, it is found that the major noise mechanism is the propagation of the bulge wave along hose.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.800-811
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• 2014

Recent developments in the prediction of the contribution of windnoise to the interior SPL have opened a realm of new possibilities in terms of i) how the convective and acoustic sources terms can be identified, ii) how the interaction between the source terms and the side glass can be described and finally iii) how the transfer path from the sources to the interior of the vehicle can be modelled. This work discusses in details these three aspects of wind noise simulation and recommends appropriate methods to deliver required results at the right time based on i) simulation and experimental data availability, ii) design stage at which a decision must be made and iii) time available to deliver these results. Several simulation methods are used to represent the physical phenomena involved such as CFD, FEM, BEM, FE/SEA Coupled and SEA. Furthermore, a 1D and 2D wavenumber transformation is used to extract key parameters such as the convective and the acoustic component of the turbulent flow from CFD and/or experimental data whenever available. This work focuses on the validation of the wind noise source characterization method and the vibro-acoustic models on which the wind noise sources are applied.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.563-564
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• 2014

Recent developments in the prediction of the contribution of windnoise to the interior SPL have opened a realm of new possibilities in terms of i) how the convective and acoustic sources terms can be identified, ii) how the interaction between the source terms and the side glass can be described and finally iii) how the transfer path from the sources to the interior of the vehicle can be modelled. This work discusses several simulation methods that can be used to represent the physical phenomena involved such as CFD, FEM, BEM, FE/SEA Coupled and SEA. This work focuses on the validation of the wind noise source characterization method and the vibro-acoustic models on which the wind noise sources are applied in the framework of a benchmark proposed by Hyundai Motors Corporation.

• 대한공업교육학회지
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• 제33권2호
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• pp.273-286
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• 2008

수중에서 UUV(Unmanned Underwater Vehicle)에 장착되는 수중 음향 센서 배열은 UUV의 측면이나 전면에 부착하여 외부 신호를 탐지하게 된다. 이러한 센서 배열은 UUV의 특성상 곡면배열(Conformal array) 형태이며 유체 유기 소음의 영향을 받는다. 따라서 본 논문에서는 탄성층에 삽입된 하이드로폰이 외부 유입 소음의 영향을 받는 정도를 해석하였다. 유입 소음은 난류 경계층에서 발생하는 Corcos 모델을 이용하였고 주파수 밀도 함수를 이용하여 수치해석 하였다. x-방향의 파수인 kx에 다른 전달함수의 특성은 탄성층의 두께가 커질수록 전달함수의 적분값은 적어지므로 소음의 영향은 줄어드는 것으로 나타났다. 또한 탄성층 및 고정판의 탄성계수, 밀도 등의 변화가 전달함수 값의 변화를 일으키는지를 조사하였다. 향후 이러한 연구는 UUV에 장착되는 곡면 배열 센서의 설계에 활용할 수 있을 것으로 판단된다.

• 소음진동
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• 제11권2호
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• pp.226-233
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• 2001

It is essential to analyze structural vibrations due to turbulent wall pressure fluctuations over a body surface which moves through a fluid, because the vibrations can be a severe source of noise affecting to passengers in airplanes and SONAR performance. Generally, this kind of problems have been solved for very simplified models, e.g. plates, which can be applied to the wavenumber domain analysis. In this paper, a finite element modeling of the walt pressure fluctuations is investigated, which can be applied to those over arbitrary smooth surfaces. It is found that the modeled wall pressure fluctuation at nodes becomes uncorrelated at higher frequencies and at lower flow speeds, and the response is over-estimated due to the aliased power. Then the frequency range available for uncorrelated loading model and two power correction schemes are presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.817-824
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• 2000

It is essential to analyze structural vibrations due to turbulent wall pressure fluctuations over a body surface which moves through a fluid, because the vibrations can be a severe source of noise affecting to passengers in airplanes and SONAR performance. Generally, this kind of problems have been solved for very simplified models, e.g. plates, which can be applied to the wavenumber domain analysis. In this paper, a finite element modeling of the wall pressure fluctuations over arbitrary smooth surfaces is investigated. It is found that the modeled wall pressure fluctuation at nodes becomes uncorrelated at higher frequencies and at lower flow speeds, and the response is over-estimated due to the aliased power. Finally, the frequency range available for uncorrelated loading model and two power correction schemes are presented.

• 한국소음진동공학회논문집
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• 제23권8호
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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.

• 대한조선학회 특별논문집
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• 대한조선학회 2008년도 특별논문집
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• pp.96-105
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• 2008

Turbulent flow-induced vibrations generate the structural fatigue and noise problems. In this paper, using Corcos, Smol' yakov-Tkachenko, Ffowcs Williams and Chase models, the input power generated by distributed fluid force is predicted for power flow analysis (PFA) of turbulent flow-induced vibration. Additionally, the Fast Fourier Transform (FFT) is used to raise the calculation efficiency PFA results obtained are compared with the classical modal solutions for verifications. Analytic results using the fluid models show good agreements with those of modal analysis, respectively.

• 한국가시화정보학회지
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• 제19권3호
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• pp.92-98
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• 2021

Large Eddy Simulation (LES) has been popularly applied and used in the last several decades to simulate turbulent boundary layer in the numerical domain. A fully developed turbulent boundary layer has also been applied to predict the complicated wake flow behind bluff bodies. In this study we aimed to generate an artificial turbulent boundary layer, which is based on an exponential correlation function, and generates a series of realistic three-dimensional velocity data in two-dimensional inlet section which are correlated both in space and in time. The results suggest its excellent capability for high Reynolds number flows. To make an effective generation, a hexahedral mesh has been used and Cholesky decomposition was applied to possess suitable turbulent statistics such as the randomness and correlation of turbulent flow. As a result, the flow characteristics in the domain and fluctuating pressure near the wall are very close to those of fully developed turbulent boundary layers.