• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.145-146
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• 2006

Recently, the next-generation advanced flow visualization techniques such as holographic PIV, dynamic PIV, echo-PIV, micro/nano-PIV, and X-ray PIV have been introduced. These advanced measurement techniques have a big potential as the core technology for analyzing outmost thermo-fluid flows in future. These would be indispensable in solving complicated thermo-fluid flow problems not only in the industrial fields such as automotive, space, electronics, aero- and hydro-dynamics, steel, and information engineering, but also in the research fields of medical science, bio-medical engineering, environmental and energy engineering etc. Especially, NT (Nano Technology) and BT (Bio Technology) strongly demand these advanced measurement techniques, because it is impossible for conventional measurement methods to observe most complicated nano- and bio-fluidic phenomena. In this presentation, the basic principle of these high-tech flow visualization techniques and their practical applications which cannot be resolved by conventional methods, such as blood flows in a micro-tube, in vivo analysis of micro-circulation, and flow around a living body will be introduced as a blue ocean strategy.

• Journal of the Korean Society of Visualization
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• v.4 no.2
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• pp.3-5
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• 2006

Recently, the next-generation advanced flow visualization techniques such as holographic PIV, aynni.c PIV, echo-PIV, micro/nano-PIV, and X-ray PIV have been introduced. These advanced mea-surement techniques have a big potential as the core technology for analyzing outmost thermo-fluid flows in future. They would be indispensable in solving complicated thermo-fluid flow problems not only in industrial fields such as automotive, space, electronics, aero- and hydro-dynamics. steel, and information engineering, but also in the research fields of medical science, bio-medical engineering, environmental and energy technology etc. Especially, NT (Nano Technology) and BT (Bio Technology) strongly demand these advanced measurement techniques, because it is impossible for conventional measurement methods to observe the nano- and bio-fluidic flow phenomena. In this article, the basic principle of these high-tech flow visualization techniques and their practical applications which cannot be resolved by conventional methods, such as blood flows in a micro-tube, in vivo analysis of micro-circulation, and flow around a living body are introduced as a blue ocean strategy.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.301-304
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• 2006

This paper presents a review of the important recent literature available in the area of micro-channel flow analysis and mixing. The topics covered include the physics of flows in micro-channels and integrated simulation of micro-channel flows. Also the flow control models and electro-kinetically driven micro-channel flows are explained. A comparison of various mixing principles in micro-channels are provided in sufficient detail.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.90-93
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• 2004

Micro PIV was applied to measure velocity profiles of two-fluid flows in a microchannel. In this work, the two-fluid flow of two glycerol-water mixtures was measured for three cases $(\phi=0\;and\;\phi=0.2;\;\phi=0.1\;and\;\phi=0.5;\;\phi=0\;and\;\phi=0.6)$. The flow rates of two fluids were the same. The experimental velocity profiles agreed well with numerical simulations. However, a slight deviation was found in the fluid with low concentration. Rather than the effects of the varying refractive indices inside the channel, the high velocity gradient effect was thought as the main source of the deviation.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.689-690
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• 2008

In the present study, a micro holographic PTV (HPTV) system was used to experimentally investigate the structure of 3D flow within a curved micro-tube with varying Dean number. The employed HPTV system incorporated a high-speed digital camera to measure the temporal evolution of the 3D velocity fields of micro-scale fluid flows. With increasing Dean number, flow in the curved tube is transformed from a steady flow to a secondary flow with two counter-rotating vortices. In this study, to analyze the 3D flow characteristics in the curved section of tube at a high Dean number, the trajectories of fluid particles were obtained experimentally using the whole 3D velocity field data obtained by the micro HPTV technique. The mean velocity field distribution was then obtained by ensemble averaging the instantaneous velocity fields. These results would be helpful in the design of various passages within micro-scale devices or micro-chips and in understanding the mixing phenomena that occur in curved conduits along the trajectories of fluid particles.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.305-308
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• 2006

For controlling micro-flows inside a LOC (lab-on-a-chip) a syringe pump or an electronic device for EOF(electro-osmotic flow) have been used in general. However, these devices are so large and heavy that they are burdensome in the development of a portable micro-TAS (total analysis system). In this study, a new flow control system employing pressure chambers, digital switches and speed controllers was developed. This system could effectively control the micro-scale flows inside a LOC without any mechanical actuators or electronic devices We also checked the feasibility of this new control system by applying it to a LOC of micro-mixer type. Performance tests show that the developed control system has very good performance. Because the flow rate in LOC is controlled easily by throttling the speed controller, the flows in complicate microchannels network can be also controlled precisely.

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.10-16
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• 2019

Considering the role of viscosity in the hemorheology, the characteristics of non-Newtonian fluid are important in the pulsatile blood flows. Stenosis, with an abnormal narrowing of the vessel, contributes to block blood flows to downstream tissue and lead to plaque rupture. Therefore, systematic analysis of blood flow around stenosed vessels is crucial. In this study, non-Newtonian behaviors of blood analog fluids around the micro-stenosis with 60 % severity in diameter of $500{\mu}m$ was examined by using CFX under the pulsatile flow conditions with the period of 10 s. Viscosity information of two non-Newtonian fluids were obtained by fitting the value of normal blood and highly viscous blood. As the Newtonian fluid, the water at room temperature was used. During the pulsatile phase, wall shear stress (WSS) is highly oscillated. In addition, high viscous solution gives rise to increases the variation in the WSS around the micro-stenosis. Highly oscillating WSS enhance increasing tendency of plaque instability or rupture and damage of the tissue layer. These results, related to the influence on the damage to the endothelium or stenotic lesion, may help clinicians understand relevant mechanisms.

• The KSFM Journal of Fluid Machinery
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• v.10 no.5
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• pp.27-33
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• 2007

Rarefied gas flows through two-dimensional micro channels are studied numerically for the performance optimization of a nanomembrane-based Knudsen compressor. The effects of the wall temperature distributions on the thermal transpiration flow patterns are examined. The flow has a pumping effect, and the mass flow rates through the channel are calculated. The results show that a steady one-way flow is induced for a wide range of the Knudsen number. The DSMC(direct simulation Monte Carlo) method with VHS(variable hard sphere) model and NTC(no time counter) techniques has been applied in this work to obtain numerical solutions. A critical element that drives Knudsen compressor Is the thermal transpiration membrane. The membranes are based on aerosol or machined aerogel. The aerogel is modeled as a single micro flow channel.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.706-711
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• 2003

A numerical method is presented for computing unsteady incompressible two-phase flows with immersed solids. The method is based on a level set technique for capturing the phase interface, which is modified to satisfy a contact angle condition at the solid-fluid interface as well as to achieve mass conservation during the whole calculation procedure. The modified level set method is applied for numerical simulation of bubble deformation in a micro channel with a cylindrical solid block and liquid jet from a micro nozzle.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.86-91
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• 2006

In this parer, we present the bubble forming and motion in the micro channel by using the two-dimensional numerical computation and experiment. In the numerical computation, The Lattice Boltzmann method(LBM) and free-energy model is used to treat the interfacial force and deformation of binary fluid system, drawn in to a micro channel and a numerical simulation is carried out by using the parallel computation method. The urn in this investigation is to examine the applicability of LBM to numerical analysis and experimental method of binary fluid separation and motion in the micro channel.