• Nuclear Engineering and Technology
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• 제26권3호
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• pp.345-354
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• 1994

수치 해석을 통하여 이차유동을 포함한 핵연료봉 주위의 난류 유동장을 예측하였다. 등방성 난류와 점성계수 모델과 이차 유동을 모사하기 위해 단순화된 대수응력모델을 사용하여 난류 운동 에너지 (k)와 난류 에너지 소멸률($\varepsilon$)의 이 방정식 모델과 운동량 방정식을 유한 차분법으로 풀어 유동장내의 평균속도, 이차유동, 난류 운동 에너지, 난류 응력 분포 등을 구하였다. 수치해석 예측치를 실험데이타와 비교하여 만족할만한 결과를 얻었고 유동장내에서 이차유동의 영향을 확인하였다. 즉 이차유동이 절대 크기는 작더라도 대류 효과에 의해 큰 영향을 미치는 것을 본 연구를 통해 알 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.139-145
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• 2001

The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry) to high_speed flow characteristics within ginseng cleaner model. Three different kinds of flow rate(15. 20, 27l/min) are selected as experimental condition. Optimized cross correlation identification to obtain velocity distribution, time-mean velocity distribution, velocity, profile, kinetic energy and turbulence intensity are represented quantitatively for the deeped understanding of the flow characteristics in a ginseng cleaner model.

• 한국정밀공학회지
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• 제6권4호
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• pp.43-51
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• 1989

Free jet was investigated experimentally and numerically in range of Reynolds number from 9900 to 21000. The working fluid was air; the mean velocity components and turbulent quantities were measured by a hot-wire anemometer. In numerical computations, the governing partial differential equations of elliptic type were solved with conventional k- ${\epsilon}$ turbulence model. The measurements show that the jet increased linearly in flow direction, and that similarity for each turbulent quantity such as Reynolds shear stress, or turbulent kinetic energy was revealed in the fully developed region. The computational results show good agreements with experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.823-826
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• 2002

Experiments were conducted to show the characteristics of the flow on unventilated parallel plane jets. Measurements of mean velocity components and turbulent intensities were carried out with a particle image velocimetry. The measurements range of these experiments was Reynolds number of 5300 based on the nozzle width and the cases of nozzle-to-nozzle distance were 4, 6, 8, and 10 times the width of the nozzle. Results show that a recirculation zone with a sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plate. The positions, where maximum value of mean turbulent intensities and mean turbulent kinetic energy show, were at the same position with the merging point. The spread of jets in the merging region increases more rapidly than that of jets in the converging and the combined region. As nozzle-to-nozzle distances were increased, it was shown that merging and combined lengths were shorter.

• 한국분무공학회지
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• 제1권1호
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• pp.76-84
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• 1996

The nozzle geometry and up-stream inject ion condition affect the characteristics of flow inside the nozzle. such as turbulence and cavitation bubbles. Flow details in fuel nozzle orifice with sudden contraction of cross sectional area have been investigated both experimentally and numerically. The measurements of velocities of internal flow in a scaled-up nozzle with different length to diameter rat io(L/d) were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds numbers. The turbulent intensity and turbulence kinetic energy in a sharp inlet nozzle were higher than that in a round inlet nozzle. Calculations were also performed for the same nozzles as scaled-up experimental nozzles using the SIMPLE algorithm. External spray behavior under different nozzle geometry and up-stream flow conditions using Doppler technique and visualization technique were also observed.

• 한국가시화정보학회지
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• 제1권2호
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• pp.29-37
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• 2003

During the past five decades or so, the characteristics of turbulent swirling flow have been studied extensively because of its great technological and scientific importance. It is well known that the swirling flow improves heat transfer in duct flow. The reason for this is due to the effect of streamline curvature associated with the tangential velocity component. Although many studies have been carried out to investigate the characteristics of the swirling flow in a circular tube. The experimental methods for measuring the velocity components are by hot-wire or LDV (Laser-Doppler-Velocimetry) measuring single point velocity so far. The present study was aimed to analyse the flow characteristics of swirling flow such as time-mean velocity vector, local velocity turbulence intensity and turbulence kinetic energy by using PIV(Particle-Image Velocimetry). The experiment was carried out for four Reynold numbers $1.0\times10^{4}$, $1.5\times10^{4}$, $2.0\times10^{4}$ and $2.5\times10^{4}$ of the measuring area.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.306-311
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• 2001

Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer$(\delta=270mm)$ was the natural turbulent boundary layer at the test section with fully long developing length(18m). The thin boundary layer with 36.5mm thickness was generated by on a smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity and the height of the model was $7.9{\times}10^3$. The mean velocity vector fields and turbulent kinetic energy distribution were measured and compared. The effect of boundary layer thickness is clearly observed not only in the length of separation bubble but also in the reattachment points. The thinner boundary layer thickness, the higher turbulent kinetic energy peak around the model roof. It is strongly recommended that the height ratio between model and approaching boundary layer thickness should be a major parameter.

• 대한조선학회논문집
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• 제47권4호
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• pp.517-524
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• 2010

This paper covers the numerical studies performed to investigate the characteristics of turbulent wake generated by a submarine, SUBOFF model. A SUBOFF model assumed as an axial-symmetric body was used to generate wake. The numerical simulation was performed by using a commercial S/W, FLUENT, with the same condition as the experiments by Shin et al.(2009). Mainly the cross-sectional distribution of the time-averaged mean wake and turbulent kinetic energy was compared with the experiments. Both results are agreed well with each other in the propeller wake section, but the agreement between both is not so satisfied in the far wake field. It means that more numerous number of grid points and their concentration should be required in that field.

• 대한기계학회논문집
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• 제14권3호
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• pp.716-724
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• 1990

본 연구에서는 2차원 경사충돌분류에 대한 실험을 수행하였고, 이 결과를 수] 치해석에 의한 계산치와 비교하였다. 실험에서는 난류특성을 구명하기 위하여 열선 풍속계를 사용해 충돌각의 변화에 따른 평균속도, 각 난류응력성분, 압력등을 측정하 였다.수치해석을 위한 난류모델로는 표준 K-.epsilon.모델을 사용하였다.

• 대한기계학회논문집
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• 제9권6호
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• pp.714-724
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• 1985

본 논문에서는 입자가 부상된 2상유동의 해석에서 여러유동조건의 유동을 공 통적으로 해석할 수 있고 또 유동의 난류구조를 규명할 수 있도록 하기 위해서 2-방정 식 난류모델을 적용하였고 또 지배방정식들 속에 나타나는 1유체와 2유체의 2차 상관 관계들을 모형화 할 때 Taweel and Landau의 스펙트럼 이론을 확장발전시켜 적용하였 다.