• 소음진동
• /
• 제11권1호
• /
• pp.5-14
• /
• 2001

송풍기나 홴과 같은 유체기계의 소음은 최근 들어 사람들의 관심을 끌면서 많은 사회적 문제가 되고 있다. 이러한 문제는 유체기계가 제품의 구매요구를 결정할 뿐만 아니라 환경소음의 규제와도 관계가 깊다. 이런 홴이나 송풍기 소음은 축 편심에 의한 진동 소음과, 유동에 의한 유동소음이 있는데 대형 송풍기는 진동 소음과 유동 소음이 동시에 존재하지만 중소형 송풍기는 유동 소음이 우세하다. 유동 소음은 공력음향학이라는 학문의 한 분야로 유동에 대한 정보가 있어야 정확한 소음원을 파악하고, 특성도 예측이 가능하다. 유동과의 강한 연관성 때문에 지금까지 송풍기의 유동 소음에 대한 연구가 미약하였다.(중략)

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 학술대회
• /
• pp.302-307
• /
• 2008

The development technology for the helicopter is improved by the increasing of computing power and advanced test facilities. The increasing efficiency of fuel consuming by the developing of improved lift-to-drag rotor system is the major issue, the noise reduction for ecology(civil area) and increase of survivability to reduce noise detection(battlefield) also are important. This investigation shows the classification of helicopter external noise and requirements, the noise flight test methods, the numerical modeling method for aero-acoustic of rotor blade and the result of CAA(Computational Aero-Acoustic) for main rotor blade.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년 추계학술대회논문집
• /
• pp.302-307
• /
• 2008

The development technology for the helicopter is improved by the increasing of computing power and advanced test facilities. The increasing efficiency of fuel consuming by the developing of improved lift-to-drag rotor system is the major issue, the noise reduction for ecology(civil area) and increase of survivability to reduce noise detection(battlefield) also are important. This investigation shows the classification of helicopter external noise and requirements, the noise flight test methods, the numerical modeling method for aero-acoustic of rotor blade and the result of CAA(Computational Aero-Acoustic) for main rotor blade.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.78-83
• /
• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curls extension of Lighthills. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.562-562
• /
• 2014

Assessment of aerodynamic noise is becoming increasingly important for automotive manufacturers. Flow passing a vehicle may indeed lead to high interior noise level and affect cabin comfort. Interior noise results from various mechanisms including aerodynamic fluctuations of the disturbed flow around the side mirror or pillar, hydrodynamic and acoustic loading of the car panels and windows, vibration of these panels and acoustic radiation inside the vehicle. Objective of the present study is to capture these important mechanisms in a simulation model and demonstrate the ability of the combined simulation tools Fluent / Virtual.Lab to provide accurate aerodynamic and interior noise prediction results. Previous study focused on the noise generated by the turbulence around the A-pillar structure of the HSM (Hyundai simplified model). The present study also includes the effect of the side-mirror and rain-gutter structures. Complete modeling process is presented including details on the unsteady CFD simulation and the vibro-acoustic model with absorption materials. Guidelines and best practices for building the simulation model are also discussed.

• 항공우주시스템공학회지
• /
• 제13권1호
• /
• pp.47-53
• /
• 2019

한국항공우주연구원(KARI)은 전기추진 수직이착륙(eVOTL) 항공기 공력성능 향상 방안 연구의 일환으로 교차회전 방식에 대한 기술개발 타탕성에 관한 연구를 진행하였다. 프로펠러 반지름을 증가시켜 전산해석을 수행하고 기존 상용 멀티콥터를 구매하여 0.11 m와 0.21 m 프로펠러를 적용하여 교차회전 구동방식에 관한 기술개발 가능성을 확인한 후, 총 중량 3 kg급의 멀티콥터를 설계 제작하여 추력 및 소음을 측정하기 위한 지상시험을 수행하였다. 교차회전 방식의 효율성을 검증하기 위해 지상시험은 15 in.와 22 in. 프로펠러를 적용하여 동일한 깃끝 속도(Tip speed) 조건에서 추력 및 소음을 측정하여 결과를 비교 분석 하였다. 지상시험결과 요구동력은 22 in. 프로펠러를 적용한 교차회전 방식이 15 in. 프로펠러와 비교하여 약 30%정도 절감 되며 공력소음의 경우 3~5 dB의 소음감소 효과가 측정 되었다.

• 한국전산유체공학회지
• /
• 제18권1호
• /
• pp.22-27
• /
• 2013

Researches in the area of aeroacoustics have been conducted by two methods. In the first method theoretical formula or experimentation are utilized, and in the second method flow field analysis and acoustic analogy are utilized. In contrast to the first method, the second method does not need new experiments for every individual change of flow configurations and conditions, and it can predict their effects by the flow field analysis, which makes the second method preferred than the first one. In this paper numerical analysis to predict noise generated by a turbulent flow about a two dimensional circular cylinder by use of CAA (Computational Aeroacoustics) method is conducted and the results are compared to the available experimental data.

• 한국음향학회지
• /
• 제41권6호
• /
• pp.698-704
• /
• 2022

본 논문에서는 노즐 내부 유동의 소음원으로부터 발생되어 방사되는 공력 소음을 정량적으로 분석하였으며, 이를 외부 방사소음 결과와 비교하였다. 세가지 종류의 노즐 형상에 대해 내부 및 외부 유동을 정확히 예측하기 위해 고해상도 수치해석 기법인 비정상 압축성 대와류모사(Large Eddy Simulation, LES) 기법을 사용하였다. 와류소음원(Vortex Sound Source)을 통해 유동소음원을 확인하였으며, 이를 통해 노즐 내부 형상에서 주요 유동소음원의 분포를 확인하였다. 노즐 내부 유동의 와류소음원 레벨과 외부 방사 소음의 예측결과 및 측정결과와 비교하였으며, 이를 통해 정량적 분석을 검증하였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문초록집
• /
• pp.334.1-334
• /
• 2002

In this study, a cross-flow fan system used in indoor unit of the split-type air conditioner is analyzed by computational simulation. A commercial CFD code - Fluent - is used to calculate the performance and its unsteady flow characteristics. The unsteady incompressible Wavier-Stokes equations are solved using a sliding mesh technique on the interface between rotating fan region and the outside. The acoustic pressure is calculated by using Ffowcs-Williams and Hawkings equation. (omitted)

• 한국소음진동공학회논문집
• /
• 제14권9호
• /
• pp.785-791
• /
• 2004

The objective of this research is to suggest anoise prediction method for a centrifugal compressor. It is focused on the Blade Passing Frequency component which is regarded as the main part of the rotating impeller noise. Navier-Stokes solver is used to simulate the flow-field of the centrifugal compressor, and the time-dependent pressure data are calculated to perform the near-field noise prediction by using Ffowcs Williams - Hawkings formulation. Indirect Boundary Element Method is applied to consider the noise propagation effect. Pressure fluctuations of the inlet and the outlet in the centrifugal compressor impeller are presented and the sound pressure level prediction results are compared with the experimental data.