• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.10-15
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• 2002

The assessment of PIV to measure the mean velocity and turbulence was carried out over a train of fixed two-dimensional dunes. The agreement between the PIV and LDV is good enough even in regions of flow reversals and high shear. Though limited in the wall normal direction field-of-view, PIV provides instantaneous flow fields, which reveal the complex nature of flow over dunes, as well as more sophisticated analyses such as two-point space correlation and quadrant analysis with a reasonable accuracy The present study is expected to be directly applied to more complex flow such as sediment transport.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.158-158
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• 2020

국내외 기상이변으로 인한 하천허용유량의 초과가 많이 일어나고 있다. 이때 사람이 직접 도섭으로 하천의 정보 대한 정보를 취득하기 어렵기 때문에 간접적인 방법으로의 정보취득이 중요시 되어야 한다. 그에 따른 방법으로 주입식의 표면부자를 활용한 방법이나, PIV 기법을 활용한 표면영상유속계측법을 이용한 유속측정방법 등이 있다. 하지만 이런 표면영상유속계측법은 영상의 변위가 커지게 되어 시간간격 설정에 대한 어려움 등이 있고, 표면부자법의 경우 표면 유속을 대변 할 수 있을지에 대한 분석연구가 필요하다. 따라서 이러한 표면 영상 유속계측법과 표면부자의 수표면 유속 측정 능력 등을 분석하여 GPS 전자부자의 활용성을 확인해 보고자 하였다. Lab-Scale 수로에서 GPS전자부자를 입자로 활용하여 주입 후 흘러가는 부분을 영상촬영하고, LS-PIV 기법을 활용하여 분석한 후 검증이 된 전자유속계 (FlowTracker)의 데이터를 참값으로 비교 분석하였다. LS-PIV 기법을 통해서 GPS 전자부자의 표면 유속 측정 능력을 잘 검증해낸다면, 유속측정에 용이하고 접근성 및 안정성까지 확보할 수 있다. 더 나아가 홍수 시 사용뿐만 아니라, ADCP나 ADV로 측정이 불가능한 저수심·저유속의 중소하천에서도 적용할 수 있다. GPS전자부자의 지속적인 연구는 향후 하천 측정 시스템에 많은 도움을 줄 것으로 사료된다.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.259-267
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• 2005

In an attempt to elucidate combustion mechanism or premixed spray flame in detail, both the enlarged photographing, which was performed for spray cross-sectional images of premixed spray flame, and the cross-correlation PIV, which was performed for consecutive time-series images to obtain instantaneous two dimensional flow field, were applied. This study indicated that CW laser as well as pulse laser could be applied for PIV. Furthermore, the results of cross-correlation PIV, which was self-made PIV program, was shown in good agreement with those of PDA. Therefore, it was verified that cross-correlation PIV using CW laser in this study could be effectively used for observing structure of premixed spray flame.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.474-474
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• 2017

대하천 사업 이후 국내에서 경험하지 못한 대규모 다기능 보가 설치되었으며, 이로 인해 기존 하천에 서식하던 어류들의 군집, 이동 및 환경의 변화가 발생할 수 있으며, 산란을 위해 상류로 이동하거나 하류로 이동하려는 어류들에게는 상당히 큰 문제를 야기할 수 있다. 이러한 문제점들을 최소화하기 위해 다기능 보에는 대규모 어도가 설치되었으며, 다양한 흐름해석 모형을 이용하여 어도의 유인효율평가에 대한 연구가 이루어지고 있으나 이를 검증할 수 있는 실험적 연구는 부족한 실정이다. 어도의 유인효율평가에 있어 어도입구부 유속장 측정이 중요하다. 하지만 어도 입구부에 대한 접근성은 용이하지 못 할 뿐만 아니라, 기존에 사용하던 ADCP 장비로는 유속장 측정에 한계가 있다. 이를 극복하기 위해 드론영상을 활용한 LS-PIV기법과 GPS전자부자를 활용할 필요가 있다고 판단하였고, GPS전자부자를 어도 입구부에서 일정시간 유하시키는 동시에 드론영상촬영을 활용해 LS-PIV기법을 적용하여 유속을 측정하였다. 그 결과 LS-PIV기법을 적용한 실험이 주 흐름영역에서 안정적인 결과를 보였다. 본 실험 결과를 통해 새로운 유속 계측 방안을 보여줌으로써 접근성 및 안전성에 대한 효율적인 실험계측 방법을 제시하리라 사료된다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.43-57
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• 2002

This paper introduces an analysis method to predicting the flow characteristic of flow field around otter board In order to develope a high performance model. In this experiment, it is used a numerical analysis of flow field through CFD(Computational Fluid Dynamic), PIV method in which quantitative, qualitative evaluation is possible. In this experiment, it is used PIV method with flow filed image around otter board in order to analysis of flow characteristic. The result compared flow pattern with analysis result through CFD and also measurement result of lift and drag force coefficient carried out in CWC(Circulating Water Channel). The numerical analysis result is matched well with experiment result of PIV in the research and it is able to verify In the physical aspect. The result is as follows ; (1) It was carried out visibility experiment using laser light sheet, and picture analysis through PIV method in order to analysis fluid field of otter-board. As a result, the tendency of qualitative fluid movement only through the fluid particle's flow could be known. (2) Since PIV analysis result is quantitative, this can be seen in velocity vector distributions, instantaneous streamline contour, and average vorticity distributions through various post processing method. As a result, the change of flow field could be confirmed. (3) At angle of attack 24$^{\circ}$ where It Is shown maximum spreading force coefficient, the analysis result of CFD and PIV had very similar flow pattern. In both case, at the otter-board post edge a little boundary layer separation was seen, but, generally they had a good flow (4) As the result of post processing with velocity vector distributions, instantaneous streamline contour and average vorticity distributions by PIV, boundary layer separation phenomenon started to happen from angle of attack 24$^{\circ}$, and from over angle of attack 28$^{\circ}$, it happen at leading edge side with the width enlarged.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.45-46
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• 2001

PIV(Particle Image Velocimetry : 입자영상유속계)는 유동장에 분포된 추종입자의 위치를 영상처리에 의해 자동추적 함으로써 속도벡터를 전유동영역에 걸쳐 동시에 구할 수 있는 계측기법이다. 따라서, CFD와 같이 정량적 및 정성적으로 수치해석된 결과와 바로 비교 검토가 가능한 유일한 실험기법으로 인식되고 있다. 본 실험에서는 CFD에 의한 모형의 유체유동 특성을 분석하고 이를 회류수조에서 PIV를 이용해 모형 전개판 주위의 유체흐름을 분석하여 각 전개판 모형의 유체유동 특성을 파악하였다. (중략)

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.37-44
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• 2000

An experimental study has been carried out at circulating water channel to investigate the viscous flow around breaking waves generated by a submerged hydrofoil(NACA0012). Detailed flow measurements were made at several critical points including an incipient wave-breaking point and a fully-developed wave breaker. Particle Image Velocimetry(PIV) was employed to visualize the flow field very close to the breaker as well as at the near- and far-wake of the breaker. Generation, development and decay of the wave breaker have been investigated. It is found that PIV technique could be well applied to the complex flow field, including the vortical structures near the free surface as well as the wake of the hydrofoil.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.509-513
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• 2005

Ship maneuverability is mainly determined according to hull-propeller-rudder system of a ship and directly related to the ship safety during the operation in the ocean. Among hull-propeller-rudder system the rudder system had direct concern with the ship maneuverability and a special rudder has been recommended to improve the ship maneuverability. In this paper the study of flapped rudder's 2-dimensional section was accomplished Model tests had been carried out with different angles of attack of a main foil and flap's deflection angles to predict the performance of the flapped rudder and the 2 frame particle tracking method had been used to obtain the velocity distribution in the flow field during model tests. $Re=1.027{\times}10^4$ had been used during the whole experiments and measured results had been compared with each other.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.71-76
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• 2017

The roll damping problem in the design of ships and offshore structures remains a challenge to many researchers due to the fluid viscosity and nonlinearity of the phenomenon itself. In this paper, the study on viscous roll damping of a circular cylinder was carried out using forced oscillations. The roll moment generated by forced oscillation using a torque sensor was measured for each forced oscillation period and compared with the empirical formula. Although the magnitude of the measured torque from the shear force was relatively small, the results were qualitatively similar to those obtained from the empirical formula, and showed good agreement with the quantitative results in some oscillation periods. In addition, the flow around the circular cylinder wall was observed closely through the PIV measurements. Owing to the fluid viscosity, a boundary layer was formed near the wall of the circular cylinder, and a minute wave was generated by periodical forced oscillations at the free surface through the PIV measurement. In this study, the suitability of the empirical formula for the roll moment caused by viscous roll damping was verified by model tests. The wave making phenomenon due to the fluid viscosity around the wall of a circular cylinder was testified by PIV measurements.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.200-207
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• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.