• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.236-239
• /
• 2005

본 연구에서는 정밀 측정/검사장비의 운영상 발생하는 에러의 원인을 규명하기 위함이다. C/R에 사용되어지는 정밀측정/검사장비는 장비 기초에 대하여 진동허용규제치를 장비 제작업체 제공한다. 이에 C/R 구조 및 장비 기초에 대하여 진동원 차단 방안등을 수행하게된다. 이러한 진동허용규제치를 만족시키기 위한 방안을 수행함에도 공조 소음등과 같은 요인에 의한 장비의 운영상 발생하는 진동과 관련된 에러를 규명하고 이를 제어하기 위한 연구를 수행하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1476-1481
• /
• 2007

Numerical investigation on radiation characteristics of discrete frequency noise from asymmetry aero-intakes was carried out. The near-field predictions were obtained by solving the linearized Euler equations with computational aeroacoustic techniques consisting of high order finite difference scheme, non-reflecting boundary conditions, oversetgrid techniques. For the prediction of far-field directivity pattern, the Kirchhoff integral method was applied. By comparing the directivities of noise radiating from the scarf and the scoop aero-intakes with that from an axisymmetric aero-intake, it is shown that noise reduction at downward peak radiation angle can be achieved. The scattering of the radiating acoustic wave by background mean flow shifts the peak lobe radiation angle toward ground and increases the amplitude of the acoustic pressure compared with the cases without mean flow effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.342-343
• /
• 2010

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.839-842
• /
• 2002

Some open jet wind tunnels have been operating under limitations due to large pressure fluctuations at some wind tunnel speeds. The Hyundai Aero-acoustic full scale Wind Tunnel (HAWT), which was completed in 1999, shows that most of the specifications were fulfilled but wind tunnel pulsations at some wind speeds were observed. Hyundai Motor Company started the wind tunnel modification in order to solve this problem in 2001. After the modification work the amplitude of pressure fluctuation was reduced and below required level over full wind speed range. Aero-acoustic performance, e.g. background noise, as well as aerodynamic performance were improved after this work.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.622-625
• /
• 2008

While the research for flow over a circular cylinder has been actively carried out up to the present, it has been known that the flow has not been clarified even now. Various complex flow and aero-acoustic characteristics exist around a circular cylinder such as flow separation, wake and pressure wave propagation. In this paper, research was carried out for wake flow and aeroacoustics over a circular cylinders by using high order, high resolution techniques that are used in two dimensional aero- acoustic analysis. OpenMP parallel processing method was used. For the numerical result, the periodic characteristic of Strouhal Number due to vortex shedding was comparatively analyzed with other experiment values and two dimensional numerical results.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.48.1-48.1
• /
• 2005

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.76-80
• /
• 2001

Unsteady compressible Euler equation is solved and the high-order, high-resolution numerical solver, physical boundary condition, adaptive nonlinear artificial dissipation model and conformal mapping are applied to computation of steady transonic flow and unsteady acoustics. The acoustic characteristics of axi-symmetric duct and two dimensional straight/S channel are studied and the computation results shows good agreements with linear analysis. In transonic case, local time stepping and canceling-the-residual techniques are used for convergence acceleration. The aspect of flow and acoustics in S-channel and the Pattern of noise radiation is changed by inflow Mach no. and static pressure at fan-face.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.5
• /
• pp.48-53
• /
• 2012

This paper presents a systematic procedure for three-dimensional noise analysis of an axial-flow fan by using computational aero-acoustics based on Ffowcs Williams-Hawkings equation. Flow-fields of a basic fan model are simulated by solving three-dimensional, unsteady, Reynolds-averaged Navier-Stokes equations using the commercial code ANSYS CFX 11.0. Starting with steady flow results, unsteady flow analysis is performed to extract the fluctuating pressures in the time domain at specified local points on the blade surface of the axial flow fan. The perturbed density wave by rotating blades reaches at the observer position, which is simulated by an in-house noise prediction software based on Ffowcs Williams-Hawkings equation. The detailed far-field noise signatures from the axial-flow fan are analyzed in terms of source types, field characteristics, and interpolation schemes.

• Journal of Mechanical Science and Technology
• /
• v.17 no.4
• /
• pp.590-598
• /
• 2003

A computational aero-acoustic (CAA) method is used to predict the tonal noise generated from a cavity of automobile door seals or gaps at low flow Mach numbers (A$\_$$\infty$/=0.077 and 0.147) In the present method, the acoustically perturbed Euler equations are solved with the acoustic source term obtained from the unsteady incompressible Navier-Stokes calculations of the cavity flow in self-sustained oscillations. The aerodynamic and acoustic fields are computed for the Reynolds numbers based on the displacement thickness, Re$\_$$\delta$*/=850 and 1620 and their fundamental mode characteristics are investigated. The present method is also verified with the experimentally measured sound pressure level (SPL) spectra.

• Journal of Mechanical Science and Technology
• /
• v.17 no.2
• /
• pp.280-287
• /
• 2003

The unsteady flow characteristics and the related noise of separated incompressible laminar boundary layer flows (Re$\sub$$\delta$/* = 614, 868, and 1,063) are numerically investigated. The characteristic lines of the wall pressure are examined to identify the primary noise source, related with the unsteady motion of the vortex at the reattachment point of the separation bubble. The generation and propagation of the vortex-induced noise in the separated laminar boundary layer are computed by the method of Computational Aero-Acoustics (CAA), and the effects of Reynolds number, Mach number and adverse pressure gradient strength are examined.