• 동력기계공학회지
• /
• 제4권4호
• /
• pp.32-40
• /
• 2000

A study on the fluid flow with ultrasonic forcing was carried out to get the enhancement of turbulence by laying emphasis on the ultrasonic incidence angles and reflectors. A large water tank was made of the transparent acrylic plates and city water of $25^{\circ}C$ was used as working fluid. 7 angles ($30^{\circ},\;45^{\circ},\;60^{\circ},\;90^{\circ},\;120^{\circ},\;135^{\circ},\;150^{\circ}$) as the ultrasonic incidence angle and 4 materials (wood, acryl, glass, iron) as the reflector were selected arid experiments for the above were made. The velocity vector distribution, kinetic energy and turbulence intensity of the turbulence flow fields enhanced by ultrasonic forcing were measured, compared and discussed by using the PIV measurement which was possible to measure the velocities of simultaneous multipoints. In results, it was cleared that the incidence angle of ultrasonic and material of reflector influenced the enhancement of turbulence.

• 대한조선학회논문집
• /
• 제59권4호
• /
• pp.225-234
• /
• 2022

The flow field measurement above whole area of the flight deck on 'Landing Platform Helicopter (LPH)' was performed by using PIV system in wind tunnel. In various heading angle conditions (0deg, -30deg, -45deg, -60deg, -75deg and ±90deg), the velocity fields such as U velocity & V velocity were measured at three different height above flight deck. Due to the geometrical characteristics of several bodies like deck, crane and super-structure, various vortex were generated. When the heading angle is 0deg, the deck edge vortex by flight deck and massive separation by super-structure were clearly observed by visualization with smoke and PIV, respectively. In other heading angles, the acceleration of flow in space between crane and super-structure were detected. And area with flow separation by super-structure is directly related to the heading angle of vessel.

• Wind and Structures
• /
• 제4권5호
• /
• pp.441-454
• /
• 2001

Conical vortices on roof corners of a prismatic low-rise building have been investigated by using the PIV(Particle Image Velocimetry) technique. The Reynolds number based on the free stream velocity and model height was $5.3{\times}10^3$. Mean and instantaneous vector fields for velocity, vorticity, and turbulent kinetic energy were measured at two vertical planes and for two different flow angles of $30^{\circ}$ and $45^{\circ}$. The measurements provided a clear view of the complex flow structures on roof corners such as a pair of counter rotating conical vortices, secondary vortices, and tertiary vortices. They also enabled accurate and easy measurement of the size of vortices. Additionally, we could easily locate the centers of the vortices from the ensemble averaged velocity fields. It was observed that the flow angle of a $30^{\circ}$ produces a higher level of vorticity and turbulent kinetic energy in one of the pair of vortices than does the $45^{\circ}$ flow angle.

• 대한기계학회논문집B
• /
• 제30권11호
• /
• pp.1051-1056
• /
• 2006

The mean and RMS velocity field of the respiratory gas flow in the human airway was studied experimentally by particle image velocimetry (PIV). Some researchers investigated the airflow for the mouth breathing case both experimentally and numerically. But it is very rare to investigate the airflow of nose breathing in a whole airway due to its geometric complexity. We established the procedure to create a transparent rectangular box containing a model of the human airway for PIV measurement by combination of the RP and the curing of clear silicone. We extend this to make a whole airway including nasal cavities, larynx, trachea, and 2 generations of bronchi. The CBC algorithm with window offset (64 $\times$ 64 to 32 $\times$ 32) is used for vector searching in PIV analysis. The phase averaged mean and RMS velocity distributions in Sagittal and coronal planes are obtained for 7 phases in a respiratory period. Some physiologic conjectures are obtained. The main stream went through the backside of larynx and trachea in inspiration and the frontal side in expiration. There exist vortical motions in inspiration, but no prominent one in expiration.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
• /
• pp.420-425
• /
• 2006

Measurements results of flow-structure-interactions (FSI) of an air-lifted body are introduced. An adaptive stereoscopic-PIV system has been constructed for the measurements of the air-lifted body. The measurement system consists of two cameras and optical sensors. The flow characteristics around a lifted cylinder body(length=60mmm, diameter =10mm, polystyrene) in the swirling flow field in a vertical pipe (length=600mm, inner diameter=) are investigated by the use of the constructed adaptive stereoscopic-PIV system. The images of the two cameras were used for the analysis of the flow fields around the floated cylinder body. The images of the cylinder body captured by the two cameras were used for the analyses of its motions. Four optical sensors (LED) were used for the detection of the postures of the freely-lifted cylinder body. The FSI analyses have been carried out to find the physical conditions at which the floating body is stabilized with its upright postures.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.723-728
• /
• 2003

The Ejector is used to get low pressure, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in ejector are investigated by PIV and CFD. The experiment using PIV measurement for mixing pipe's flow characteristics acquired velocity distribution, kinetic energy distribution, and whirlpool . (Condition : when mixing pipe's diameter ratio is 1:1.9, and the flux is $Q_{1}=1.136{\imath}/s$, $Q_{2}=1.706{\imath}/s$, $Q_{3}=2.276{\imath}/s$. Based on the PIV and the CFD results, the flow characteristics in ejector are discussed, and it shows the validity of this study.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2017년도 학술발표회
• /
• pp.474-474
• /
• 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.

• 한국해양공학회지
• /
• 제12권1호
• /
• pp.113-119
• /
• 1998

An experimental study was carried out in a three-dimensional cubic cavity driven by 2-dimensional plane Poiseuille flow for three kinds of Reynolds number, $10^4$, 3 $\times$ $10^4$ and 5 $\times$ $10^4$ based on the cavity width and cavity inlet mean flow velcoity. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system. Laser based illumination and two-frame grey-level cross correlation algorithm are adopted. Severe unsteady flow fluctuation within the cavity are remarkable at above Re = 3 $\times$ $10^4$ Reynolds numbers and sheared mixing layer phenomena are also found at the region where inlet driving Poiseuille flow is collided with the clock-wise rotating main primary vortex at upper center area. Instant velocity profiles reveal that deformed forced vortex formation is observed throughout the separate two areas.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.708-713
• /
• 2001

The paper presented some results of a experimental study of natural convection in partitioned 2D square enclosure. The square enclosure consist of two adiabatic vertical walls and the upper cold and the lower hot walls. A partition is positioned perpendicularly at the center of left vertical insulated wall The PIV mesaurements were performed with the variations of the partition length and inclination of enclosure. The working fluid is water with a Prandtl number of 6.996 at $20^{\circ}C$ temperature. A captured images were calculated by using a Cross-Correlation(Multi-frame/Single-exposure) method.

• 한국공작기계학회논문집
• /
• 제15권1호
• /
• pp.56-62
• /
• 2006

An experimental investigation was performed to study the characteristics of ER(Electro-Rheological) fluid flow in a horizontal rectangular tube with or without D.C voltage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0kV/mm, 1.0kV/mm and 1.5kV/mm for Re = 0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the cluster of ERF are clearly strong along the test tube and the flow rate decreased. In this study, the rheology of ER fluid stagnating or flowing through a dispersion meter will be investigated by PIV method. And then the ER effect, which appears at the ER valves and their appliance will be visualized.