• 한국전산유체공학회:학술대회논문집
• /
• 2006.10a
• /
• pp.208-208
• /
• 2006

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2004.11a
• /
• pp.291-294
• /
• 2004

최근 들어 위성영상의 사용성 증대와 더불어 고정밀한 공간지리정보의 획득에 대한 관심이 증대되고 있으며, 모델링의 정확도 수준은 수치표고모형, 정사영상 등에 영향을 미치므로 고정밀 모델링 기법을 수행하여야함. 또한 비접근 지역의 경우 많은 기준점을 획득하기 어려우므로 최소 기준점 즉, 2점 의 GPS관측성과와 수치지도를 이용하여 궤도모델링을 수행한 후 모델링(Bundle Adj.)을 수행

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.6
• /
• pp.705-712
• /
• 2022

A sudden pressure drop caused by the pressure relief valve acts as a strong noise source and propagates the compressible pressure fluctuation along the pipe wall, which becomes a excitation source of Acoustic Induced Vibration (AIV). Therefore, in this study, the numerical methodology is developed to evaluate the reduction effect of compressible pressure fluctuation due to curved pipe in the pressure relief valve system. To describe the acoustic wave caused by density fluctuation, unsteady compressible Large Eddy Simulation (LES) technique, which is high accuracy numerical method, Smagorinsky-Lilly subgrid scale model is applied. Wavenumber-frequency analysis is performed to extract the compressible pressure fluctuation component, which is propagated along the pipe, from the flow field, and it is based on the wall pressure on the upstream and downstream pipe from the curved pipe. It is shown that the plane wave and the 1st mode component in radial direction are dominant along the downstream direction, and the overall acoustic power was reduced by 3 dB through the curved pipe. From these results, the noise reduction effect caused by curved pipe is confirmed.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.296-296
• /
• 2017

본 연구에서는 대규모 유역에서 발생하는 침수 현상을 모의하기 위한 강력하고 정확하며 연산효율이 뛰어난 수치해석 모형을 개발하는 데 있다. 개발된 모형은 확산파 모형을 기본으로 하였고 다수의 코어를 동시적으로 해석하는 병렬연산 기법을 부가하였다. 홍수로 인한 대규모 유역에서의 침수해석은 오랜 시간의 연산 비용을 필요로 한다. 특히 수치화된 지형정보의 이용이나 고정밀 사진 측량 등의 방법을 이용하여 정밀하고 넓은 유역의 디지털 지형자료를 이용한 2 차원 침수해석은 연산 연산의 문제를 더욱 어렵게 할 수 있다. 그러므로 본 연구에서는 제내지나 하류 유역에 발생하는 홍수로 발생된 빠른 침수모의를 위해 병렬화된 침수 해석 모형을 이용하여 병렬 해석 모형의 적용성을 검토하고자 하였다. 연구를 위해 MPI 및 OpenMP 기법을 이용하여 2 차원 침수해석 프로그램의 원시코드를 개선하고 실제 제내지 및 실제 댐 하류유역에 적용하였다. 개발된 모형은 실제 제내지에 적용한 결과를 MPI, OpenMP 병렬해석 기법과 기존의 순차적 모형의 결과를 비교하였다. 모형들의 결과를 제내지의 침수양상, 침수 속도벡터의 방향 및 크기 등의 계산 결과 순차적 모형, MPI 및 OpenMP 모형과의 비교하여 연산 시간은 병렬 해석 모형이 우월함을 보였다.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.33-36
• /
• 2006

As the computing environment is rapidly improved, the interests of CFD are gradually focused on large-scale computation over complex geometry. Keeping pace with the trend, essential computational tools to obtain solutions of complex aerospace flow analysis and design problems are examined. An accurate and efficient flow analysis and design codes for large-scale aerospace problem are presented in this work. With regard to original numerical schemes for flow analysis, high-fidelity flux schemes such as RoeM, AUSMPW+ and higher order interpolation schemes such as MLP (Multi-dimensional Limiting Process) are presented. Concerning the grid representation method, a general-purpose basis code which can handle multi-block system and overset grid system simultaneously is constructed. In respect to design optimization, the importance of turbulent sensitivity is investigated. And design tools to predict highly turbulent flows and its sensitivity accurately by fully differentiating turbulent transport equations are presented. Especially, a new sensitivity analysis treatment and geometric representation method to resolve the basic flow characteristics are presented. Exploiting these tools, the capability of the proposed approach to handle complex aerospace simulation and design problems is tested by computing several flow analysis and design problems.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.1
• /
• pp.112-121
• /
• 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).

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.724-725
• /
• 2015

본 논문에서는 모터의 방사계 소음 진동에 영향을 미치는 표면전자기력의 발생 매커니즘을 확인하고자 한다. 고정자 표면에서 발생하는 전자기력 가운데 토크에 기여하지 않는 성분을 구분하기 위해 전자리겨 성분을 Radial과 Tangential방향으로 나눈다. 이 중 토크에 기여하지 않는 Radial방향의 힘을 발생시키는 Tangential Flux Density성분의 분포를 확인하고, 자속 포화도 분포와 어떠한 관계가 있는지 확인한다. 모터의 자속밀도 및 전자기력에 대한 계산은 유한요소해석을 기반으로 한 수치 해석기법을 통해 수행하였다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.12 no.2
• /
• pp.120-126
• /
• 2019

Recently, there is an increasing need for highly precise processing with the rapid development of precision machinery, electrical and electronics, and semiconductor industries. Cutting machine control relies on the operator's sense and experience in tradition, but it has been greatly enhanced by the adoption of CNC(Computerized Numeric Controller). In addition, cutting dynamics technology has been paid attention to reflect the operating state of machine in real time. This paper presents a method to detect and stabilize tool vibration by attaching an acoustic sensor to a CNC machine. The sensed acoustic data is synchronized with the tool position and the abnormal vibration frequency is separated from the collected acoustic frequency, then analyzed to detect the tool vibration. Also the reliability the tool vibration detection and stabilization is improved by applying the cutting dynamic method. The proposed method is analyzed and evaluated in terms of the surface roughness.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.6
• /
• pp.371-377
• /
• 2017

The performance of an air conditioner is closely related to the cooling performance of a split-type outdoor unit so that, in most of the relevant preceding studies, the independent performance of an axial fan in an outdoor unit has been studied. However, there is a lack of research on the effects of other components in an outdoor units was rarely investigated. Therefore, in this paper, the effects of the fan orifice among other parts on the flow performance of the outdoor unit was numerically investigated. A virtual fan tester consisting of 18 million grids was developed for highly resolved flow simulation. The unsteady RANS (Reynolds-averaged Navier-Stokes) equations are numerically solved by using finite-volume CFD (Computational Fluid Dynamics) techniques. In order to verify the validity of the numerical methods, the predicted P-Q curve of the cooling fan in a full outdoor unit is compared with the measured one. Optimization of orifice shape was carried out for maximum flow performance of the outdoor unit using the validated numerical method.

• Tunnel and Underground Space
• /
• v.26 no.1
• /
• pp.24-31
• /
• 2016

Recently, many studies have been conducted to use fixed-wing and rotary-wing unmanned aerial vehicles (UAVs, Drones) for topographic surveying in open-pit mines. Because the fixed-wing and rotary-wing UAVs have different characteristics such as flight height, speed, time and performance of mounted cameras, their results of topographic surveying at a same site need to be compared. This study selected a construction site in Yangsan-si, Gyeongsangnam-do, Korea as a study area and compared the topographic surveying results from a fixed-wing UAV (SenseFly eBee) and a popular rotary-wing UAV (DJI Phantom2 Vision+). As results of data processing for aerial photos taken from eBee and Phantom2 Vision+, orthomosaic images and digital surface models with about 4 cm grid spacing could be generated. Comparisons of the X, Y, Z-coordinates of 7 ground control points measured by differential global positioning system and those determined by eBee and Phantom2 Vision+ revealed that the root mean squared errors of X, Y, Z-coordinates were around 10 cm, respectively.