• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.36-39
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• 2005

Information on temporal evolution of whole velocity fields is essential for physical understanding of a complicated turbulent flow and was obtainable using dynamic PIV because of advances of high-speed imaging technique, laser and electronics. A dynamic PIV systme consists of a high-speed CMOS camera having $1K\times1K$ pixels resolution at 1 KHz and a high-repetition Nd:Yag pulse laser. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet whose Reynolds number is about 3000. The particle images of $1024\times512$ pixels were captured at a sampling rate of 4 KHz. The dynamic PIV system measured successfully the temporal evolution of instantaneous velocity fields of the turbulent jet, from which spectral analysis of turbulent structure was also feasible.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.32-37
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• 2006

In this paper, we present the flow and heat transfer characteristics with the array of impinging jet nozzles by using the numerical computation and experiment. Numerical solutions were obtained for dimensionless gap H=6, dimensionless outlet length L=10 and Reynolds number Re=1500 by using the commercial CFD code, CFX-5. Experimental and numerical results were agreed well with each other. It was found that the impinging jet with circular array nozzles generated the uniform heat transfer area and the maximum heat transfer is higher than rectangular array nozzles for certain parameter sets. It is one of the most important utilities providing steam to turbine in order to supply mechanical energy in thermal power plant. It is composed of thousands of tubes for high efficient heat transfer.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.86-92
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• 2000

Two-phase flow in a combustion chamber is experimentally analyzed according to the five different conditions in the Reynolds number of $1.02{\times} 10^4$ As the height difference between the primary and secondary jets increases the secondary has a little effect on the primary. In the case of the same height difference the primary jet is affected as the velocity of secondary increases. The primary-jet flow field causes the particle concentration since the particle stagnation phenomena appear in the recirculation zone. The particle concentration is controlled by the velocity of secondary jet the height difference and the angle of primary jet in the test section.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.141-149
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• 2002

A numerical simulation is performed for the cooling heat transfer of a heated cylindrical pedestal by an axisymmetric jet impingement. Based on the k- $\varepsilon$- f$\sub$${\mu}$/ model of Park et at., the linear and nonlinear stress-strain relations are extended. The Reynolds number based on the jet diameter(D) is fixed at Re$\sub$D/ = 23000. The local heat transfer coefficients are compared with available experimental data. The predictions by k- $\varepsilon$-f$\sub$${\mu}$/ model are in good agreement with the experiments, whereas the standard 7- f model does not properly resolve the flow structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.979-987
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• 1996

A theoretical study for the laminar round jet diffusion flame impinging on the wall was carried out to predict the characteristics and structure of impinging jet flame and heat transfer to the wall. Finite chemistry via Arrhenius equation was adopted as the combustion model. All the transport properties were considered as the variable depending on the temperature and composition. For the parametric study, the distance from nozzle to perpendicular wall and Reynolds number at nozzle exit were chosen as the major parameters. As the results of the present study, the characteristics of flow field and the distributions of temperature, density and each chemical species were obtained. The heat transfer rate from flame to the wall and the effective heating area were calculated to investigate the influence of the major parameters on the heat transfer characteristics.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1767-1771
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• 2004

A 4D-PTV system was constructed. The measurement system consists of three high-speed high-definition cameras, Nd-Yag laser(10mJ, 2000fps) and a host computer. The GA-3D-PTV algorithm was used to extract three-dimensional velocity vectors in the measurement volume. A horizontal impinged jet flow was measured with the constructed system. The Reynolds number is about 40,000. Spatial temporal evolution of the jet flow was examined in detail and physical properties such as spatial distributions of vorticity and turbulent kinetic energy were obtained with the constructed system.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2804-2809
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• 2008

Experimental results and numerical computations were conducted to investigate the effect of the confined wall on the flow and heat transfer characteristics for a two-dimensional impinging jet. Experimental results and Numerical solutions were obtained by using the particle image velocimetry and the commercial CFD code (CFX 11), respectively. The parameters studied were jet Reynolds number (Re=5,000), conditions of confined wall (unventilate), nozzle to plate spacings ($H/W=1{\sim}16$), and nozzle to nozzle spacing (S/W=6). Experimental and numerical results were agreed well with each other. The maximum heat transfer point was found variation of nozzle to plate spacings.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.8
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• pp.714-719
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• 2007

In this paper, we report experimental investigations on measurement of adiabatic wall temperature on a flat 2-D plate of high-speed impinging jet made by circular-shape nozzle at steady state condition using infra-red camera. Experiments have been conducted for the Reynolds number of 187,000 according to the change of nozzle-to-plate distance. Dimensionless number, recovery factor, has been used to represent the measured adiabatic wall temperature. And we compared the result obtained by using infra-red camera with that obtained by using thermocouple.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.689-696
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• 1989

In this experimental study, relative particle size distribution was measureed at the inlet and outlet of the slit impactor using the particle sizer. The imployed measuring method of the size distribution was different from the conventional method. This measurement system has the advantage of obtaining the particle collection efficiency for various particle size easily and at once compared with other methods. The effects of jet to plate distance and Reynolds number on the characteristic impactor efficiency curves have been studied. In the results of this experiment, the increment of collection efficiency was observed as Reynolds number increases in the case of S/W = 1/2 but was very slight. The influence of S/W is more remarkable than that of Reynolds number on the particle collection efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.927-936
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• 1998

In the fully developed pipe flow, when jet is injected in cross to the flow there are complex transition flows caused by interaction of the cross flow and jet. These interactions are studied by means of the flow visualization methods and frequency analysis using a hot-wire anemometer. The velocity range of cross flow of the pipe is 0.3 m/s ~ 1.2 m/s and the corresponding Reynolds number, R$\sub$p/, based on the pipe diameter is 2.25 * 10$\^$3/ ~ 9.02 * 10$\^$3/. The velocity ratio (R), jet velocity/cross flow velocity, is chosen from 2 to 10. A circular cylinder is placed in the pipe instead of jet to observe the vortex shedding from the solid body. To compare the jet and circular cylinder flow, the vortical structure is analyzed in both cases and the structure of vortices and the origin of its formation are investigated, especially. The vortex shedding of the dominant coherent structure is compared between the jet flow and the circular cylinder flow. In the case of the jet flow, the Strouhal numbers are different depending on the existence of the upright vortex as well as the velocity ratio (R).