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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Visualization
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Journal DOI :
The Korean Society of Visualization
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Volume & Issues
Volume 8, Issue 4 - Dec 2010
Volume 8, Issue 3 - Sep 2010
Volume 8, Issue 2 - Jun 2010
Volume 8, Issue 1 - Mar 2010
Volume 7, Issue 2 - Jan 2010
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Mixing in a Microchannel by using Induced-charge Electro-osmosis
Jeon, Young-Hun ; Heo, Young-Gun ; Jung, Won-Hyuk ; Alapati, Suresh ; Suh, Yong-Kweon ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 13~18
DOI : 10.5407/JKSV.2010.8.4.013
This paper presents an experimental study on the performance of a micro-mixer using AC electro-osmotic flow. The microchannel is made of PDMS for the side and top walls and glass patterned with ITO for the bottom wall. We first investigated the effect of the applied potential as well as the frequency on the slip velocity. We have found that the slip velocity is roughly proportional to the applied voltage in line with the Helmholtz-Smoluchowski equation and there is an optimum frequency at which the slip velocity becomes maximized. To find the optimum parameters for mixing device we tested our device for various design parameters. It turned out that the best mixing effect is obtained approximately when the electrode angle is
, electrode width
, and the frequency of power supply 700 Hz.
An Experimental Study of Flow Field in a Torque Converter
Yoo, S.C. ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 19~25
DOI : 10.5407/JKSV.2010.8.4.019
The flow field measurements were conducted on the planes between impeller blades, and the gap between the impeller and turbine blades under speed ratio of 0.4. The study showed that high velocity regions move from locations near the suction surface of the impeller to the pressure blade, shroud corner as flow progresses from the mid-chord of impeller passage to exit and out into the gap region. Planes 3 through 5 also showed flow reversal occurring in the area near the shell surface and progress far into the impeller passage from the impeller passage exit, near shell surface. This affected the converter efficiency negatively. This study would aid in the construction of higher accuracy CFD models of this complex turbomachinery device.
Precise Estimations on Vorticities using a Hybrid PTV-PIV Algorithm
Doh, Deog-Hee ; Cho, Gyong-Rae ; Lee, Jae-Min ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 26~30
DOI : 10.5407/JKSV.2010.8.4.026
A PTV algorithm was constructed using a linear transformation, in which the merits of the conventional PIV and PTV were adopted. In PIV calculations, the obtained velocity vectors are affected by the filtering effects by its calculation principle. PTV techniques are widely used for their excellences of measuring small scaled flows, such as nano and bio flows. However, PTVs produce vector errors due to interpolation process. To overcome these problems, a hybrid PTV algorithm was constructed by combining PTVs' and PIVs' benefits using a linear transformation. The Taylor-Green vortex flows were generated for the tests of vorticity calculations. The conventional gray-level cross-correlation PIV technique and 2-Frame PTV technique were tested for the same flows for comparisons with those obtained by the constructed hybrid algorithm. The excellence of the constructed hybrid algorithm was validated through an actual experiment on the cylinder wake.
Development of Hybrid Micro/Nano PIV system
Min, Young-Uk ; Lee, Dong-Yeop ; Kim, Kyung-Chun ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 31~37
DOI : 10.5407/JKSV.2010.8.4.031
In this study, a novel hybrid micro/nano PIV system combining defocusing and TIRFM technique has been developed for the multiscale flow measurement. With the developed system, both far and near field velocity fields have been measured simultaneously in a 2D straight microchannel and the particle trajectories were extracted by the nearest tracking algorithm. The shear rate values taken from experimental results have been estimated by comparing with the analytical solution of 2D Poiseuille flow and it is confirmed that the result shows good agreement with the theoretical value.
Visualization of Ion Transport and pH Change in Ion Concentration Polarization
Ko, Sung-Hee ; Kang, Kwan-Hyoung ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 38~42
DOI : 10.5407/JKSV.2010.8.4.038
Ion concentration polarization is an electrokinetic phenomenon which occurs in membrane systems, such as in an electrodialysis and fuel-cell system. But the phenomenon is not fully understood because hydrodynamics, electrokinetics and electrochemistry are coupled with each other. Here, we report that there occurs a change of pH value of buffer solution in concentration polarization phenomenon. To visualize the change of pH, the litmus solution which is one of the pH indicators was used. It is conjectured that the pH of solution changes because hydrogen ions were concentrated in cathodic side and hydroxide ions were concentrated in anodic side. We anticipate that this work may contribute to the fundamental understanding on the ion concentration polarization phenomenon.
Droplet Bistability in Microchannel and its Application to Flow Control
Lee, Beom-Joon ; Yoo, Jung-Yul ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 43~47
DOI : 10.5407/JKSV.2010.8.4.043
We demonstrate the droplet bistability in a microchannel which has two symmetric necks that operate as capillary valves. It is shown that there are certain flow conditions, determined by droplet velocity and droplet size, to achieve bistability. Droplet bistabililty allows simple but precise control of droplet at a bifurcation channel. Therefore, by an appropriate channel design to induce droplet bistability, we can distribute droplets at a junction passively in the manner of perfect alternation and perfect switching in the choice of the outlets.
Visualization of Water-uptake Process in Excised Roots of Arabidopsis using Synchrotron X-ray Imaging Technique
Hwang, Bae-Geun ; Kim, Hae-Koo ; Lee, Sang-Joon ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 48~53
DOI : 10.5407/JKSV.2010.8.4.048
Water-uptake through roots, is an essential process of the water flow in plants. Its visualization is very useful for understanding sap flow dynamics at whole plant level. In this study, the tips of Arabidopsis' root hairs were excised and exposed to repeated dehydration and rehydration processes. The water-refilling through individual xylem vessels was visualized using the synchrotron X-ray micro-imaging technique. The high temporal resolution (
) and beam intensity of the X-ray source allowed to acquisition of consecutive X-ray images of the water-refilling process up to 10 frames/sec. Various flow patterns were observed and the ascending speed of the water-air interfaces was analyzed. The relation between the water-rising height and ascending speed was also analyzed. The present results would provide better alternative for investigating sap flows in roots.
Visualization of Temperature Distribution Deep Inside the Agar Gel Tissue Phantom Heated Using Moxibustion and 1064 nm Infrared Laser
Cho, Ji-Yong ; Kim, Jung-Kyung ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 54~59
DOI : 10.5407/JKSV.2010.8.4.054
A laser moxibustion therapy device having effect similar to that of traditional moxibustion is being developed using 1064 nm infrared laser. The therapy device allows direct interaction of laser light with the tissue rendering temperature distribution both on the skin surface and deep under the skin. We made a device that could measure temperature of deep under the surface of agar gel tissue phantom using thermocouples. A thermal imaging camera was used to verify results from the temperature measurement device. We compared the characteristics of heat transfer inside the tissue phantom during moxibustion and laser irradiation. The temperature distribution measured by thermocouples was found to be similar to that of distribution given by thermal imaging camera.
A Visualization of the Spray from Small Liquid-rocket Engine Injector by Dual-mode Phase Doppler Anemometry
Jung, Hun ; Kim, Jeong-Soo ; Bae, Dae-Seok ; Kwon, Oh-Boong ;
Journal of the Korean Society of Visualization, volume 8, issue 4, 2010, Pages 60~65
DOI : 10.5407/JKSV.2010.8.4.060
A focus is given to the breakup behavior of spray droplets issuing from a nonimpinging-type injector. The analysis has been carried out experimentally by means of the dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters in terms of axial velocity, mean diameter, velocity fluctuation, and span (width of the size distribution) of droplets are measured down the geometric axis of a nozzle orifice and on the plane normal to the spray stream with the injection pressure variations. As the injection pressure increases, the velocity and its fluctuation become higher, whereas the droplet sizes get smaller. It is also shown that the magnitudes of those parameters are smoothed out by dispersion when the droplets move downstream as well as outwardly. The atomization process is significantly influenced by the injection pressure rather than the traveling distance in the experimental condition presented.