• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1992년도 추계학술대회
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• pp.43-46
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• 1992

$\underline{In\;vitro}$ velocity measurements were made using both the pulsed Doppler ultrasound (PDU) machine and laser Doppler anemometer (LDA) system in order to investigate the flow characteristics near the aortic bifurcation. Velocities measured from the PDU machine was in good agreement with those from the LDA. The flow in the daughter branches was three-dimensional with a secondary flow. The oscillating wall shear stress with this secondary fluid motion is well correlated with the localization of the atherosclerosis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 12th Asian Congress of Fluid Mechanics
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• pp.72.3-72.3
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• 2008

• 동력기계공학회지
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• 제12권5호
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• pp.40-47
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• 2008

The turbulent flow characteristics around a small-size axial fan(SSAF) for a refrigerator are strongly dependent upon the operating points. Four operating points such as $\phi$ =0.1, 0.18, 0.25 and 0.32 were adopted in this study to investigate three-dimensional turbulent flow characteristics around the SSAF by using a fiber-optic type Laser Doppler Anemometer(LDA) system. Downstream mean velocity profiles of the SSAF along the radial distance show that axial and tangential velocity components exist predominantly, except $\phi$ = 0.1, and have a maximum value at $r/R{\fallingdotseq}0.8$, but radial velocity component having a relatively small value only turns flow direction to the outside or the central part of the SSAF. The turbulent intensity shows that the radial component exists most greatly after $r/R{\fallingdotseq}0.5$. Downstream turbulent kinetic energy at $\phi$ = 0.25 and 0.32 together has the largest peak value at $r/R{\fallingdotseq}0.9$.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.59-72
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• 1998

This experimental study was carried out to investigate the characteristics of the in-cylinder eccentricity swirl flow generated by a 4 valve cylinder head with a tangential and a helical intake port. the measurements of the in-cylinder velocity field have been made by a two-channel LDA system. The mean flow coefficient(Cf(meam)), swirl ratio(Rs) and mass flowrate with valve eccentricity ratios and an intake port partition between the two intake ports were measured in the steady flow test fig using the ISM(impulse swirl meter). The experimental results indicated that the mass flowrate through the tangential intake port was 19% and 7.7% more than that of the helical intake port in case of with and without intake port partition respectively. There was a tendency to be a single rotation flow in swirl flow fields formed by a 4 valve cylinder head because of the interaction between the two intake ports. As the intake port partition was not set between flow coefficient(Cf(mean)) was 7.35%.

• 대한기계학회논문집B
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• 제20권11호
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• pp.3607-3619
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• 1996

Experimental and numerical studies for three-dimensional pulsatile flows are conducted to investigate the flow characteristics in the bifurcated tubes. Velocity measurements in experimental study were made by both Pulsed Doppler Ultrasound(PDU) machine and Laser Doppler Anemometer(LDA) system. Glycerin is used for experimental study. Experimental results are used to verify the results of the numerical simulation. Flow characteristics of Newtonian fluid and blood in the bifurcated tubes under the steady and pulsatlie flows are numerically investigated. Finite volume method is employed for three-dimensional numerical simulations. Blood is considered as a non-Newtonian fluid and the constitutive equation of blood is used for the numerical analysis. Numerical analyses are focused on the flow patterns for various branch angles ranging from 30.deg. to 90.deg. and diameter ratios such as 1.0, 0.8, and 0.6. Pulsatile flow characteristics of blood are compared with those of Newtonian fluid. Parameter effects on axial velocity, pressure and wall shear stress distribution along the bifurcated tubes are discussed in terms of the branch angle, diameter ratio, and Reynolds number.

• 대한기계학회논문집B
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• 제24권4호
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• pp.570-577
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• 2000

Local heat transfer characteristics inside a hard disk driver(HDD) are investigated in this study. The investigation is considered between disks co-rotating in a cylindrical enclosure. The gap spacing, rotating speed and head-arm positions are mainly considered to understand the flow and heat transfer in the co-rotating disks. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients on the rotating disk. Flow patterns inside the co-rotating disks are investigated using a Laser Doppler Anemometer (LDA) and also analyzed numerically. The results show that the heat transfer coefficients on the disk changed little with the gap spacing between disks. Heat transfer rates in the outer region increases with increasing rotating Renolds number, but the values normalized by that on a free rotating disk give a similar pattern for the tested cases. The head-arm inserted between the rotating disks destroys the inner region resulting in enhancement of heat transfer in that region.