• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.7
• /
• pp.907-913
• /
• 2011

Swirling flows are related to the spiral motion in the tangential direction in addition to the axial and radial direction using several swirl generators. These type of flows are used in combustion chambers to improve flame stability, heat exchanger to enhance heat transfer coefficients, agricultural spraying machines and some vertical pipes to move slurries or transport of materials. However, only a few studies three dimensional velocity profiles in a vertical pipe have been reported. In this present paper, 3 dimension particle image velocimetry(PIV) technique was employed to measure the velocity profiles in water along a vertical circular pipe with Reynolds number from 6000 to 13,000. A tangential inlet condition was used as the swirl generator to produce the required flow. The velocities were measured with swirling flow in the water along the test section using the PIV technique.

• Journal of the Korean Society of Visualization
• /
• v.9 no.4
• /
• pp.63-68
• /
• 2011

The flow-field of a liquid-metal system is very important for the safety analysis and the design of the steam generator of liquid-metal fast breeder reactor. Dynamic neutron radiography (DNR) is suitable for a visualization and measurement of a liquid metal flow and a two-phase flow in a metallic duct. However, the three dimensional DNR techniques is not enough to obtain the velocity information in the wide channel up to now. In this research, a high speed DNR technique was applied to visualize the heavy liquid-metal flow field in the narrow channel with the HANARO-beam facility. The images were taken with a high frame-rate neutron radiography at 250 fps and analyzed with a Particle Image Velocimetry(PIV) method. The images were compared with the results of the commercial CFX code to study the feasibility of DNR technique for the measuring the heavy liquid-metal flow field. The PIV images could discern the turbulent vortex flow in the two-dimensional narrow channel.

• Journal of Power System Engineering
• /
• v.15 no.3
• /
• pp.5-11
• /
• 2011

디젤기관의 경우는 종래부터 직분식이 주류를 이루었고, 근래에는 분사압력의 고압화가 진행중이다. 분사압력의 고압화에 의해 연소효율의 향상 및 배출가스중의 입자상물질(PM:Particulate Matter)의 저감을 유도하고 있으나, 연소가스의 고온화로 인해 질소산화물(NOx:Nitrogen Oxides)은 증가한다. 따라서, 분사기간의 지연(Retard)이나 파일럿분사(Pilot injection)등의 혼합기제어에 의해 질소산화물의 저감을 꾀하고 있다. 이와 같이 디젤기관에 있어서도 혼합기 형성의 최적화에 의한 연소제어를 시도하는 수법이 중시되고 있고, 이를 위해서는 디젤분무 구조에 기초한 혼합기의 형성기구에 대한 규명이 매우 중요하다. 그러므로 본 연구에서는 보다 고도의 혼합기형성 제어를 위한 기초연구로서 고온 고압장에서의 증발디젤자유분무구조를 해석하였으며, 계측영역은 연료와 주위기체와의 혼합이 활발히 진행되는 분무의 하류영역으로 설정하고, 입자화상속도측정법(particle Image Velocimetry:PIV)을 이용한 분무의 유동해석을 기초로 증발 디젤분무의 구조 해석을 행하였다. 실험조건으로서 분사압력을 72MPa, 112MPa로 각각 변화시켰다.

• Journal of the Korean Society of Visualization
• /
• v.1 no.2
• /
• pp.38-46
• /
• 2003

An experimental investigation was performed to study the turbulent characteristics of swirling flow a 90$^{\circ}C$ circular tube for Re = 10,000, 15,000 and 20,000. 2D-PIV(Particle Image Velocimetry)technique was employed to measure the fluctuation velocity field. The results include spatial distributions of mean velocity vectors, turbulence intensity and turbulence kinetic energy. The axial and radial turbulence intensities, and kinetic energy profiles show double-peak structures in the inlet region of the 90 degree bend and the profiles are disappeared along the test tube with decaying the swirl intensity.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.515-516
• /
• 2006

Internal and inlet flows of a cross-flow fan have been visualized using a particle image velocimetry(PIV) to analyze a relationship with a performance of a room air conditioner(RAC). A test model which has a geometric similarity with the real RAC has been manufactured for the experiment and the flow characteristics have been analyzed with various flow rates and inlet grill angles for the cross-flow fan. The experimental results using the PIV technique have been compared with the existing numerical results. Also, a location and movement of an eccentric vortex which can affect the performance and noise of the RAC has been investigated by the PIV with various flow rates and inlet grill angles.

• Journal of the Korean Society of Visualization
• /
• v.7 no.1
• /
• pp.21-28
• /
• 2009

The study of swirling flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of streamline. The fluid flow for tubes and elbow of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirling flow have been insufficient. Using the particle image velocimetry(PTV) method, this study found the time averaged velocity distribution with swirl and without swirl along longitude sections and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compares with that of other. Furthermore, other experimental investigation was performed to study the characteristics of turbulent water flow in a horizontal circular tube by using liquid crystal. 2D PIV technique is employed for velocity measurement and liquid crystal is used for heat transfer experiments in water. Temperature visualization was made quantitatively by calibrating the colour of the liquid crystal versus temperature using various approaches.

• 한국가시화정보학회:학술대회논문집
• /
• 2004.12a
• /
• pp.111-118
• /
• 2004

A new micro-resolution PIV (Particle Image. Velocimetry) has been developed. To investigate transient phenomena in a microfluidic device, Dynamic micro-PIV system was realized by combining a high-speed camera and a CW(Continuous Wave) laser. The technique was applied to a micro-counter-current flow, consisting of water and butyl acetate. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 $\{mu}s$ and a spatial resolution of 2.2 x 2.2 $\{mu}m$. Using the Dynamic micro-PIV technique, the vortex-like motions of fluorescent particles at the water-butyl acetate interface were captured clearly

• International Journal of Automotive Technology
• /
• v.5 no.1
• /
• pp.17-22
• /
• 2004

An experimental investigation was conducted to study the characteristics of turbulent swirling flow in an axisymmetric annuli. The swirl angle measurements were performed using a flow visualization technique using smoke and dye liquid for Re=60,000-80,000. Using the two-dimensional Particle Image Velocimetry method, this study found the time-mean velocity distribution and turbulence intensity in water with swirl for Re=20,000, 30,000, and 40,000 along longitudinal sections. There were neutral points for equal axial velocity at y/(R-r)=0.7-0.75, and the highest axial velocity was recorded near y/(R-r)=0.9. Negative axial velocity was observed near the convex tube along X/(D-d)=3.0-18.0 for Re=20,000.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.3
• /
• pp.11-20
• /
• 2010

The purpose of this study is the investigation of the wave interaction with the rectangular floating breakwater. The flow profile obtained by PIV technique is represented to understand the vortical flow due to the wave interaction with a rectangular floating breakwater in the roll motion and the fixed condition. Also, the transmission coefficients are compared in both conditions over the extensive wave periods, which represent the performance of breakwater to attenuate the incoming waves. These results would be applied to design the floating breakwater having the mooring system to improve its performance for a certain wave period.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.1
• /
• pp.21-28
• /
• 2000

Although commercial PIV systems have been widely used for the non-intrusive velocity field measurement of fluid flows, they are still under development and have considerable room for improvement. In this study, a single-frame double-exposure PIV system using a high-resolution CCD camera was developed. A pulsed Nd:Yag laser and high-resolution CCD camera were synchronized by a home-made control circuit. In order to resolve the directional ambiguity problem encountered in the single-frame PIV technique, the second particle image was genuinely shifted in the CCD sensor array during the time interval dt. The velocity vector field was determined by calculating the displacement vector at each interrogation window using cross-correlation with 50% overlapping. In order to check the effect of spatial resolution of CCD camera on the accuracy of PIV velocity field measurement, the developed PIV system with three different resolution modes of the CCD camera (512 ${\times}$ 512, lK ${\times}$ IK, 2K ${\times}$ 2K) was applied to a turbulent flow which simulate the Zn plating process of a steel strip. The experimental model consists of a snout and a moving belt. Aluminum flakes about $1{\mu}m$ diameter were used as scattering particles for the liquid flow in the zinc pot and the gas flow above the zinc surface was seeded with atomized olive oil with an average diameter of 1-$3{\mu}m$. Velocity field measurements were carried out at the strip speed $V_s$=1.0 m/s. The 2K ${\times}$ 2K high-resolution PIV technique was significantly superior compared to the smaller pixel resolution PIV system. For the cases of 512 ${\times}$ 512 and 1K ${\times}$ 1K pixel resolution PIV system, it was difficult to get accurate flow structure of viscous flow near the wall and small vortex structure in the region of large velocity gradient.