• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.922-930
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• 2004

An experimental investigation was performed to study on the generation of air bubble and air core with swirling flow in a horizontal cicular tube. To determine some characteristics of the flow, 2D PIV technique is employed for velocity measurement in water. The experimental rig is manufactured from an acryl tube. The test tube diameter of 80mm, and a length of 3000mm. The used algorithm is the gray leve cross-correlation method(Kimura et al. 1986). An Ar-ion laser is used and the light from the laser(500mW) passes through a probe to make two-dimensional light sheet. In order to make coded images of the tracer particles on one frame, an AOM(Acoustic-Optical Modulator) is used. The maximum axial velocities showed near the test tube wall at y/D =0.1 and y/D =0.9 along the test tube. The higher Reynolds number increase, the lower axial velocities are showed in the center of the test tube. The air bubbles are generated from Re =10,000 and developed into air core from the recirculating water pump rpm equal 30Hz. The pressure and temperature are measured across the test tube at X/D=3.33.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1552-1557
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• 2004

Characteristics diffusion time of viscoelastic fluids are determined experimental results of terminal velocity by using the falling ball viscometer. The characteristics diffusion time of viscoelastic fluids are determined with help of the sphere device which is installed to return the dropped sphere from the bottom of the test cylinder without disturbing the working fluids. Terminal velocity of th sphere the reason why experimental of characteristics diffusion time that it is have an effect on the time interval of the measuring. Viscous of the fluid the temperature changed in order to have an effect on temperature and terminal velocity of the ball it becomes larger the possibility of knowing. A result of visualization for flow phenomena of around the sphere uses the PIV and the density of the polymer solution which it appears 2000wppm is to a case which is the right and left becomes symmetry to be it will be able to confirm and according to the time interval, to observed velocity vector of same at first drop the sphere.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.3
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• pp.207-217
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• 2008

Costal regions in Korea often suffer severe damages due to wave-induced disasters, storm surge disasters and so on. therefore, many engineers and researchers have devoted their energy to prevent these costal disasters. The development of artificial reefs including sunken vessels is one of their remarkable achievements and various kind of these artificial upwelling structures have been designed and applied. However, the flow characteristics around a Tetrapod under the water has not been investigated experimentally. So in this article, in uniform flow of circulating water channel and some different velocities, PIV measurement has been conducted on the flow characteristics behind a Tetrapod. The results were analyzed on the flow characteristics of both cases of a Tetrapod. Therefore, it can be concluded that the both cases have its own distinctive flow characteristics behind the bluff body; Case A has an steep upstream flow pattern. On the contrary, Case B has an developed downstream flow pattern in the near wake of the Tetrapod. The velocity gradient at position x=150mm of Case-A appears gently up and down But, the velocity gradient at the same position of Case-B appears better highly up and down.

• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.64-74
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• 2003

An experimental study was carried out to investigate the effect of periodic blowing and suction on a turbulent boundary layer. Particle image velocimetry (PIV) was used to probe the characteristics of the flow. The local forcing was introduced to the boundary layer via a sinusoidally-oscillating jet issuing from a thin spanwise slot. Three forcing frequencies (f$^{+}$=0.044, 0.066 and 0.088) with a fixed forcing amplitude (A$^{+}$=0.6) were employed at $Re_{=690. The effect of the forcing angles ($\alpha$=60$^{\circ}$ , 90$^{\circ}$ and 120$^{\circ}$ ) was investigated under the fixed forcing frequency (f$^{+}$=0.088). The PIV results showed that the wall region velocity decreases on imposition of the local forcing. Inspection of phase-averaged velocity profiles revealed that spanwise large-scale vortices were generated in the downstream of the slot and persist further downstream. The highest reduction in skin friction was achieved at highest forcing frequency (f$^{+}$=0.088) and a forcing angle of $\alpha$=120$^{\circ}$. The spatial fraction of the vortices was examined to analyze the skin friction reduction.

• Journal of the Korean Society of Visualization
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• v.12 no.1
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• pp.18-24
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• 2014

The Korea Atomic Energy Research Institute (KAERI) has a scaled-down moderator test program to simulate the CANDU6 moderator circulation phenomena during steady state operation and accident conditions. In the present work a preliminary experiment using a 1/8 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a velocity field is measured with a Particle Image Velocimetry (PIV) technique under an isothermal state. The flow patterns from the inlet nozzles to the top region of the tank are investigated using PIV for a 1/8 scale moderator tank.

• Journal of the Korean Society of Visualization
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• v.14 no.3
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• pp.46-50
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• 2016

The objective of the present study is to perform experiments for water filled cavity heated and cooled from the side at $Ra=8.5{\times}108$. This experiment can provide validation database of the standard k-${\varepsilon}$ turbulence model for single-phase turbulent natural convection which has been regarded as one of the important phenomena in nuclear safety. For the natural convection inside a cavity, temperature and velocity were obtained by thermometry and PIV (Particle Image Velocimetry) methods. These results would be used for validation of standard k-${\varepsilon}$ turbulence model.

• Journal of the Korean Society of Visualization
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• v.4 no.1
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• pp.56-61
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• 2006

A change of three-dimensional vortical structures on the wake behind a road vehicle has been investigated according to the existence of an air spoiler. To reconstruct the three-dimensional velocity fields, two-dimensional PIV(particle image velocimetry) measurements were performed for lots of the x-y, y-z and z-x planes. Since the isovorticity surface does not represent exactly the vortical structures within the recirculation region due to strong shear flows, the velocity component normal to the x-y plane is obtained by interpolating those velocities in the z-x plane. Then, the ${\lambda}_2-definition$ is applied to visualize the vortices in the recirculation region. As a result, it is found that the air spoiler weakens C-pillar vortices and produces strong wing-tip vortices. Inside the recirculation region, the height and volume of coherent vortices are increased relatively when an air spoiler is equipped. On the other hand, two small coherent vortices are observed in case that an air spoiler is absent.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.255-260
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• 2015

Flash evaporation phenomenon is affected by temperature, pressure and water level in the open chamber and Baffle etc. In this study, PIV experiments were conducted to ensured the flow Characteristics in the open chamber, and optimum baffle location and baffle height. Baffle had a considerable effect on the recirculation flow, hydraulic jump and the flow characteristics in the Open chamber, and influence of Reynolds number was insignificant. The optimum baffle height was about h/H=1.5. and optimum baffle location was x/H=1.5 from the inlet of open chamber.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.468-474
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• 2011

The flow field around baffle located sudden expansion and contraction channel was measured by PIV method and the effect according to height change of baffle built in the flow field was evaluated. The inlet flow velocity and the baffle height influence mutually to the size and flow pattern of the recycle flow of the back of the baffle and the size of the area of the water power jump passing the upper part of the baffle. In case of Reynolds number $Re=4{\times}10^3$, the critical value of baffle height is estimated around h/H=1.6 and there was a decreasing tendency as the inlet flow velocity was increased.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.677-684
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• 2013

A lot study of convection heat transfer on internal flow has been extensively conducted in the past decades using of high specific surface area, increasing heat transfer coefficient, swirling flow and improving the transport properties. This study concerned with the application of a tangential slot swirl generator for improving heat transfer in a horizontal circular copper tube. The Al particles(about $100{\sim}130{\mu}m$) was employed for this experimental work. 3D PIV(particle image velocimetry) technique has employed to measure velocity profiles of Al particles with and without swirl flow. The copper tube is heated uniformly by winding of a heating coil for heat transfer work, having a resistance of 9 ohm per meter. Experiments are performed in the Reynolds number range of 6,800~12,100 with swirl and without swirl using Al particles. Experimental data for comparison of Nusselt number is presented that of with swirl and without swirl along the test tube for the Reynolds numbers. The Nusselt number is improved with increasing of Reynolds numbers or swirl intensities along the test tube. The Nusselt number with swirl flow is about 60.0% to 119.0% higher than that obtained by the Dittus-Boelter equation.