• 오토저널
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• 제10권3호
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• pp.51-59
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• 1988

The wake structure behind a van type vehicle was studied experimentally with a 5-hole yawhead probe. Through an effective calibration method of the 5-hole yawhead probe, the flow properties such as velocity vector, total pressure and static pressure were obtained on two cross sections within the wake. These results combined with the surface flow visualization performed in the previous study, yielded some information about the wake structure. When the model was placed in a stream with zero yaw angle, two counter rotating vortices were observed behind the model which pull down the surface flow on each side of the model. With increasing the yaw angle, the surface flow on the windward side changed to divide the flow in two directions, one flows upward on the upper part and the other flows downward on the lower part of the windward side. Hence a new weak vortex was created on the upper windward side, which resulted 3 vortices within the wake. The size and the strength of the vortices increased with yaw angle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2371-2373
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• 1999

This paper deals with the development, reliability, specification and performances of the ACSR inner corrosion detector system. It is designed to run on ACSR automatically and to inspect the corrosion of the line with on-line continuously. And it comprises a sensor a constant current source, a signal processing unit, a RF transmitter and receiver unit. Also separable encircling coil sensor is proposed in order to detect inner corrosion of the overhead ground wires. In conclusion, this detector can realize the nondestructive detecting of an ACSR inner corrosion.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.465-472
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• 1999

Hydraulic model tests are performed to find economical and hdrqulically stable design of cooling water intake channel of steam power plant. The result of tests show that the standard distributiion of y-components in the chamber of CWP(circulating Water Pump) are recommended below 3.5 to maintain hydraulic stability, so that this value is considered as the design criteria. Common basin is necessary to improve the hydraulic stability of inflow, however the longer basin does not always improve the hydraulic stability , and the optimal length of basin can be found in some range. From the results the flow stability maintained the best condition when the length of basin is 7.2m. Beside the standard tests the auxiliary tests like edge , baffle, trapezoidal section and increase of pump capacity are carried out based on the optimal condition foudn in the standard tests. From the series of tests the economical and hydraulically stable design of intake channel was proposed.

• 대한기계학회논문집B
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• 제33권8호
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• pp.589-595
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• 2009

The instability wave formed near nozzle region grows to vortex with large scale in downstream region of spray. It plays an important role in the fuel-air mixing, combustion process and engine exhaust emissions in direct injection diesel engine. The objective of this study is to analyze effect of variant parameters (injection pressure, ambient gas density, etc.) and fuel properties on spray instability near nozzle region. Spray structure near nozzle region was investigated using a magnification photograph. A pulsed Nd-YAG laser was used as a light source, and image was taken by CCD camera. The following conclusions are drawn from this experimental analysis. In low ambient density, the effect of fuel properties on spray instability near nozzle region is dominant. In high ambient density, the effect of ambient gas on spray instability near nozzle region is dominant. High jet velocity has strong influence on spray instability.

• 한국군사과학기술학회지
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• 제18권4호
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• pp.415-422
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• 2015

The flow field structures of dual jet-in-cross-flow were examined experimentally for in-lined perforated damage holes configuration using particle image velocimetry. Ensemble averaged in-plane velocity and vorticity data in the jet were determined to study the mean jet structure. Jets are formed by pressure differences between upper and lower airfoil surface. The flow structure of vicinity of the thru holes consist of a vortical structure that wrap around the jets like a horseshoe and develop further downstream through a pair of stream-wise vortices. The shape, size and location of the horseshoe vortex were found to be dependent on the angle of attack. In spite of the existence of battle damage holes, the effect on the control force was insignificant when the damage size was not large enough.

• 상하수도학회지
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• 제25권1호
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• pp.31-39
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• 2011

In order to suggest the methodology for achieving anti-vortex device within multi pump intake well, CFD(Computational Fluid Dynamics) simulation were conducted for two alternative suggestions. Multi-intake sump model with anti-vortex device basins were designed and the characteristics of submerged vortex were investigated in the flow field by numerical simulation. From the results of simulations, to install the horizontal plate and vertical cross plates within basins were effective for preventing air-induction vortex.

• 한국소음진동공학회논문집
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• 제17권3호
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• pp.213-219
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• 2007

Column mixer Is one of the facilities to mix fluids at petrochemical plants. The vibration of column mixer is usually caused by pumps for fluid inflow and mixing of inside fluids. This fluid induced nitration is mainly responsible for the reduction of column life. Measurements were performed for understanding the vibration characteristics of the column. First measurement results showed the need of stiffness reinforcement. After the reinforcement work, second measurement confirmed the difference between two results. Modal analysis was also performed to investigate the resonance of the column vibration and the damage of the rib plate. To confirm fluid induced vibration at the column mixer fluid structure interaction analysis using ADINA/FSI was performed, which showed the necessity of the modification of the rotary valve.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2010년도 춘계학술대회
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• pp.227-230
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• 2010

2010년 3월 26일 21시 45분경, 백령도 서남쪽 1.6km(1마일)해상에서 대한민국 해군의 초계함 천안함이 원인 미상의 사고로 침몰한 사건이 발생하였다. 이에 연안공학자의 입장에서는 수색 및 구조에 필요한 기초자료인 해상조건들을 제공하고 시뮬레이션을 통한 보다 자세한 예측 및 유추가능한 자료를 제공한다는 것은 뜻깊은 일임에 틀림없다. 이에 본 연구에서는 백령도-대청도 부근해역의 기상, 파랑, 조석 및 조류, 저질, 부유사 상태등을 조사 분석하고 이를 기초로 해역특성을 분석하였다. 사건당시의 유속상황은 소조기(neap tide)-중조기 (mean tide) 사이에 해당하며 3월 26일이 지나고 4월 3~4일까지는 유속이 가장 강한 대조기 (spring tide)가 진행되는 시점으로 수색 및 구조작업에 에로사항이 있는것으로 파악되었다. 또한, 21:00-22:00 경은 낙조가 진행 중에 있기 때문에 물질이동은 남동쪽이 우세할 것으로 보이며 특히, 불규칙한 해저지형으로 인하여 급격한 와류 등이 존재할 것으로 판단되어 입자추적실험을 수행하였다. 수행 결과, 입자는 유속상황에 따라서, 초기에는 남동쪽으로 이동하지만 장기 예측결과, 외해쪽으로 흘러가는 것으로 나타났다. 이를 통하여 추후, 수색작업의 범위를 외해쪽으로 확대시켜야 할 것으로 사료된다.

• 한국전산구조공학회논문집
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• 제22권2호
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• pp.145-152
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• 2009

본 논문에서는 풍하중을 받는 평면 막구조물의 동적불안정 판정을 규명하였다. 풍하중을 받는 막구조물의 지배방정식을 정식화할 경우 가장 중요한 것은 막 표면의 공기 압력을 합리적으로 산정하는 것이다. 베르누이 윈리에 의하여 유체 압력은 속도 퍼텐셜과 관계를 가지며 않은 날개 원리에 의해 막 표면 공기의 움직임을 일련의 와류로 간주하고 속도 퍼텐셜을 구할 수 있다. 이 논문에서는 가장 많이 쓰이는 3 절점 삼각형 막요소를 이용하여 가중 잔여치 갤러킨법을 적용한 안정 평가의 판별식을 유도하였다. 수치해석 모델로는 정사각형과 직사각형의 막구조물을 채택하였고 임계 풍속에 대한 초기인장력과 풍방향의 영향을 분석하였다.

• 한국항공우주학회지
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• 제46권7호
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• pp.567-574
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• 2018

스월은 연료의 후퇴율 증가뿐 아니라 연소 압력의 진동을 감소시키며, 하이브리드 로켓의 연소안정화에 기여하는 것으로 알려져 있다. 따라서 스월 산화제 분사에 의한 주연소실 내부의 유동 구조의 변화를 이해하고 연소안정화의 물리적 과정을 실험적으로 연구하였다. 결과에 의하면, 스월은 주연소실의 유동 구조를 변화시켜 후연소실의 500Hz 대역 p'과 q'의 발생을 억제할 뿐 아니라 두 진동의 위상차를 변화하여 상호결합(coupling)에 영향을 주고 있음을 확인했다. 또한 후연소실 화염 가시화를 통하여 스월에 의한 선회운동량의 증가로 와류발생과 흘림 등이 변화하여 연소안정화에 기여하는 것으로 분석됐다.