• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.168-171
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• 2005

The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a polygon mirror, has six sharp comers, there are low and high pressure regions on each of six edges when it rotates. Therefore, the Pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings(FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.371-379
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• 2000

A noise prediction method of axial flow fan is developed by incorporating through-flow method and vortex shedding noise model. Fan noise is assumed to be generated due to the pressure fluctuation induced by wake vortices of fan blades and radiate as diploe distribution. The wake vortices are analyzed by combining Karman vortex street model and through-flow analysis results, and the vortex-induced fluctuating pressure on blade surface is calculated by thin airfoil theory. The predicted sound pressure levels and directivity patterns of fan noise by the present method are favorably compared with fan noise test data. Furthermore, the present method is shown to be very useful for predicting the aero-acoustic performance map of the fan operated at off-design point.

• 대한기계학회논문집B
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• 제35권2호
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• pp.205-213
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• 2011

진공청소기 브러쉬의 소음원인과 소음특성에 관하여 고찰하였다. 먼저, 소음원인을 분석하기위해서 수치해석 결과를 토대로 유동저항을 분석하였다. 그 결과 청소기 브러쉬 소음의 주요 원인은 팬회전에 의한 톤소음이 아니고, 브러쉬 내부의 유체역학적인 특성에 의한 유동저항 증가로 인해서 발생하는 유동소음임을 알 수 있었으며, 그 타당성을 무향실에서 음향파워 측정 실험을 통해서 확인하였다. 다음으로, 소음측정 실험을 통해서 브러쉬의 최적 설계를 통해 저감할 수 있는 최대 소음저감 한계가 4dBA 임을 확인하였다. 팬 블레이드 개수, 공기 흡입구 확장에 따른 소음 특성을 분석하였고, 이로부터 소음저감 한계가 너무 작아서 팬 블레이드 개수, 공기 흡입구 확장에 따른 소음 저감량이 2 dBA 이내로 작은 것을 알 수 있었다.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.71-74
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• 2005

The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a Polygon mirror, has six sharp corners, there are low and high pressure regions on each of six edges when it rotates. Therefore, the pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings (FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.

• 소음진동
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• 제9권4호
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• pp.693-702
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• 1999

We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1789-1794
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• 2004

The present study investigates flow characteristics in an optical disc drive. Detailed knowledge of the flow characteristics is essential to analyze flow-induced noise and vibration, forced convection and flow friction loss. The ODD used in the personal computer is used for the experiment and rotating velocity of disc is under the 4500 rpm. Time-resolved velocity components and velocity spectrum are obtained using the laser Doppler anemometry (LDA). The results show that the front holes reduce now-induced noise and the position of pickup body affects flow near the window. In addition, il is possible for cooling of heat sources in an optical disc drive through measuring the flow fields under the tray.

• 대한기계학회논문집B
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• 제29권2호
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• pp.224-231
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• 2005

The present study investigates flow characteristics in an optical disc drive (ODD). Detailed knowledge of the flow characteristics is essential to analyze flow-induced noise and vibration, forced convection and flow friction loss. The ODD used in a personal computer is used for the experiment and rotating velocity of disc is under the 4500 rpm. Time-resolved velocity component and velocity spectrum are obtained using the laser Doppler anemometry (LDA), and the flow patterns induced by rotating disc in the ODD are calculated by a commercial finite volume method at the same time. The results show that the front holes reduce flow-induced noise and the position of pickup body only affects flow near the window. Furthermore, it is possible for cooling of heat sources in the drive through measuring the flow fields under the tray. In addition, the numerical results are well matched up to the experimental results, therefore, the validation of the numerical results can be achieved. From the validation of numerical results, it is possible to predict the flow characteristics of the region where it is unable to conduct the experiment.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.39-48
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• 2016

The latest research has shown that the turbulence-induced noise is important in total characteristics of flow noise. Also, turbulence-induced noise have a significant influence for performance of sonar dome. In this paper, Flow analysis is performed on vicinity of the sonar dome model using Large Eddy Simulation method. Also, direct method that extracts perturbational sound pressure, FW-H method without turbulence-induced noise and permeable FW-H method that is able to calculate turbulence- induced noise were compared in order to show turbulence effect.

• 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.

• International Journal of Fluid Machinery and Systems
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• 제7권1호
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• pp.7-15
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• 2014

In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.