• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.345-354
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• 1994

Numerical Predictions including secondary flows have been Performed for fully developed turbulent single-phase rod bundle flows. The k-$\varepsilon$ turbulence model(two equation model) for the isotropic eddy viscosity, together with an algebraic stress model for generating secondary velocities, enabled the prediction of mean axial velocities, secondary velocities, and turbulent kinetic energy and turbulent stresses. Comparisons with experiment hate shown that the influence of secondary motion on mean flow and turbulence is dearly evident. The convective transport effects of secondary flow on the velocity field have been identified.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.1
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• pp.81-91
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• 1994

Combustion noise involved with chemical heat release and turbulent process in turbopropulsion systems, gasturbine, industrial furnaces and internal engines is indeed noisy. The experimental study reported in this paper is made to identify a dominant combustion noise in jet flames. Gaseous propane and kerosene fuel have been used with air as the oxidizer in a different jet combustion systems. Combustion and aerodynamic noise are studied through far field sound pressure measurements in an anechoic chamber. And also mean temperature and velocities and turbulent intensities of both isothermal and reacting flow fields were measured. It is shown that axial mean velocity of reacting flow fields is higher about 1 to 3m/sec than that of cold flow in a gaseous combustor. As the gaseous fuel flow rate increases, the acoustic power increases. But the sound pressure level for the spray flame decreases with increasing equivalence ratio. The influence of temperature in the combustion fields due to chemical heat release has been observed to be a dominant noise source in the spray flame. The spectra of combustion noise in gaseous propane and kerosene jet flame show a predominantly low frequency and a broadband nature as compared with the noise characteristics in an isothermal air jet.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.405-409
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• 2001

An experimental analysis of the flow inside the refrigeration compartment of a home refrigerator was conducted in order to achieve better performances in terms of uniform temperature distribution and cooling speed. 2D PIV and stereoscopic PIV were used for the experiments on an actual-size refrigerator at operating conditions. Two CCD cameras were employed for a wider field of view in the measurement of the shelf, and stereoscopic PIV was used to measure the three velocity components at the various cooling duct outlets and the mean velocity fields were area-integrated to calculate the flow-rates. 50 to 100 instantaneous velocity fields were time averaged for the mean velocity fields. With the result of this analysis, a new cooling duct system was developed, with the refrigerator's cooling performance increasing 11% in terms of cooling speed, and 25% in temperature uniformity.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.200-204
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• 2005

The sirocco fan is used to get low noise, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in sirocco fan are investigated by PIV. The experiment using PIV measurement for Test section's flow characteristics acquired velocity distribution, .Condition : when sirocco fan in automobile air controller maximum 1450RPM, and a revolution is a variation (1)950RPM, (2)1100RPM, (3)1250RPM. The agreement a experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating, ventilation and air conditioning.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.723-728
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• 2003

The Ejector is used to get low pressure, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in ejector are investigated by PIV and CFD. The experiment using PIV measurement for mixing pipe's flow characteristics acquired velocity distribution, kinetic energy distribution, and whirlpool . (Condition : when mixing pipe's diameter ratio is 1:1.9, and the flux is $Q_{1}=1.136{\imath}/s$, $Q_{2}=1.706{\imath}/s$, $Q_{3}=2.276{\imath}/s$. Based on the PIV and the CFD results, the flow characteristics in ejector are discussed, and it shows the validity of this study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.690-700
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• 1994

The effects of thermal stratification on the flow of a stratified fluid past a circular cylinder were examined in a wind tunnel. In order to produce strong thermal stratifications, a compact heat exchanger type variable electric heater is employed. Linear temperature gradient of up to $250^{\circ}C/m$ can be well sustained. The velocity and temperature profiles in the cylinder wake with a strong thermal gradient of $200^{\circ}C/m$ were measured and the smoke wire flow visualization method was used to investigate the wake characteristics. It is found that the temperature field effects as an active contaminant, so that the mean velocity and temperature profiles can not sustain their symmetricity about the wake centerline when such a strong thermal gradient is superimposed. It is evident that the turbulent mixing in the upper half section is stronger than that of the lower half of the wake in a stably stratified flow.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.12 no.3
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• pp.25-39
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• 2004

An experimental study was quantitatively carried out in order to investigate the influence of flow conditions on a boundary layer in the near-wake of a flat plate. Tripping wires attached at various positions were selected to change flow conditions of a boundary layer in the vicinity of trailing edge. The flows such as laminar, transitional, and turbulent boundary layer at 0.98C from the leading edge are imposed to investigate the evolution of symmetric and asymmetric wake. Measurements were made at freestream velocity of 6.0m/s, and the corresponding Reynolds number is $2.8{\times}10^5$. An x-type hot-wire probe(55P61) was employed to measure at 8 stations in the near-wake region. Test results show that the near-wake of the flat plate for the case of a laminar and transitional boundary layer is sensitive to mean flow shear generated after separation but for the case of turbulent boundary layer is insensitive.

• Journal of the Korean Society of Visualization
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• v.1 no.2
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• pp.47-51
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• 2003

Microfluidic chips such as lab-on-a-chip (LOC) include micro-channels for sample delivery, mixing, reaction, and separation. Pressure driven flow or electro-osmotic flow (EOF) has been usually employed to deliver bio-samples. Having some advantages of easy control, the flow characteristics of EOF in microchannels should be fully understood to effectively control the electro-osmotic pump for bio-sam-pie delivery. In this study, a micro PIV system with an epifluorescence inverted microscope and a cooled CCD was used to measure velocity fields of EOF in a glass microchannel and a PDMS microchannel. The EOF velocity fields were changed with respect to electric charge of seeding particles and microchannel materials used. The EOF has nearly uniform velocity distribution inside the microchannel when pressure gradient effect is negligible. The mean streamwise velocity is nearly proportional to the applied electric field. Glass microchannels give better repeatability in PIV results, compared with PDMS microchannels which are easy to fabricate and more suitable for PIV experiments.

• Journal of computational fluids engineering
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• v.2 no.2
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• pp.9-17
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• 1997

The performance of several turbulence models in computing an axisymmetric supersonic base flow is investigated. A compressible Navier-Stokes code, which incorporates k-ε, k-ω model and Reynolds stress closure with three kinds of pressure-strain correlation model, has been developed using implicit LU-SGS algorithm with second-order upwind TVD scheme. Numerical computations have been carried out for Herrin and Dutton's base flow. It is observed that the two-equation models give large backward axial velocity approaching to the base and somewhat larger variation of base pressure distribution than the Reynolds stress model. It is also found that the Reynolds stress model with third order pressure-strain model in the anisotropy tensor predicts most accurate mean flow field.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.185-193
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• 2003

Basic flow fields of two dimensional V flames were examined as a preliminary work to study the instability of premixed flame with vorticity generation. Laminar premixed propane and methane flame were anchored by electrically heated wire to make two dimensional V flames. Flow fields were measured mainly by PIV(Particle Image Velocimetray) and the results were compared with those obtained by LDV(Laser Doppler Velocimetry) to confirm their reliability. Because the curvatures of V flames are so small, V flames were locally assumed to be inclined planar flames in gravitational field. The measured flow fields were locally compared with those of analytical solutions, which showed the qualitatively similar results. In downstream region, the vorticity fields were nearly constant except region near the center line, which support the assumption of locally one dimensional flame. Besides it was tried to find experimentally the similarity of flow fields in downstream region. Finally, stability diagram of propane and methane flames were drawn for the equivalence ratio less than one and the wide range of mean velocity.