• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1069-1074
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• 2004

This study investigated the effect of pressure variations on augmentation of heat transfer when the ultrasonic waves were applied. The augmentation ratio of heat transfer was experimentally investigated and was compared with the profiles of pressure distributions calculated applying a coupled finite element-boundary element method (coupled FE-BEM). As the ultrasonic intensities increase from 70W to 340W, the velocity of the liquid paraffin is found to increase as well as kinetic energy, This physical behavior known as quasi-Eckart streaming results from acoustic pressure variations in the liquid. Especially, the higher acoustic pressure distribution near two ultrasonic transducers develops more intensive flow (quasi-Eckart streaming), destroying the flow instability. Also, the profile of acoustic pressure variation is consistent with that of augmentation of heat transfer. This mechanism is believed to increase the ratio of hear transfer coefficient.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1389-1394
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• 2004

Experiments were done for the unsteady flow in a counter rotating axial flow fan near peak efficiency and stall point. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional passage flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Comparison of flow characteristics between two different operating conditions such as tip vortex, secondary flow and turbulence intensity were performed through the analyses of axial, radial and tangential velocity distributions. As a result, tip vortex and secondary flows are enforced and measured obviously at stall point.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.34-44
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• 1996

N-machine produces more than input energy at above 3000 rpm. any space energy is absorbed when the N-machine is rotating at a very high velocity. Laws of electromagnetics verify that normal conduction is due to that electrons moves from one three-dimensional crystallizing ${\pi}-bonding$ orbital to next. The ${\pi}-far$ infrared rays are generated from the resonance and rotation of the electrons on the orbitals of three-dimensional crystallizing ${\pi}-bonding$ atoms. Material in universe is composed of ${\pi}-rays$, which have alternative outward electric field. If the alternative outward electric fields of the ${\pi}-rays$ are resonant each other they make attraction force, which is the gravity. The collection of space energy is due to a attraction force between the radially alternating electric field and the ${\pi}-far$ infrared rays in the space. Electrons flow by absorbed density difference of ${\pi}-far$ infrared rays along a conduction wire, which also verifies that normal electron conduction is due to a flow from one three-dimensional crystallizing ${\pi}-bonding$ orbital to next.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.749-756
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• 2000

Chemical application, one of the most important crop management processes happened to cause spray drift, that would threaten farmers in field as well as dwellers in rural region. Spray drift was affected by micro-meteorological parameters. In Korea, a boom sprayer was introduced but good effects of a boom sprayer was not evaluated. A study to evaluate short distance drift characteristics of a boom sprayer in paddy fields has been undergoing and determining wind characteristics in paddy field was the main purpose of this paper. Micro-meteorological information has been pre-requisite information for evaluating drift in both long and short distances or in both theoretical and experimental ways. Wind velocity, Reynolds stresses, turbulence intensity, skewness, kurtosis etc. were evaluated with height from the ground using a 2-dimensional probe and a hot wire anemometer system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1104-1108
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• 2007

Automobile sunroof buffeting is the tonal noise of low frequency around 20Hz. It occurs due to the acoustic feedback process between the shear layer detached from the leading edge of sunroof opening and the Helmholtz resonator-like property of a car cabin. In this paper, PIV visualization technique is applied to the unsteady flow field around sunroof opening of an SUV in the full-scale automotive wind tunnel in order to find out buffeting mechanism. A phase-marking PIV measurement method, in which image and sound pressure are recorded simultaneously, and a phase-rearrangement post-processing program were developed for capturing noise-related velocity fields without expensive synchronization systems. Through this study, some characteristics of the real-car sunroof shear layers under various deflector conditions were identified and these results can provide insights into the noise reduction mechanism of the tube-type deflector.

• Journal of Power System Engineering
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• v.4 no.2
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• pp.11-16
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• 2000

Simultaneous quantitative measurements are made of the velocity fields for two-dimensional natural convection in a rectangular enclosure using PIV(Particle Image Velocimetry). The experiments are performed at a Prandtl number of 6.62, an aspect ratio of 1.0, Rayleigh numbers from $1.294{\times}10^6\;to\;3.8841{\times}10^6$, and angles of inclination of $0^{\circ},\;30^{\circ}\;and\;60^{\circ}$ inside a $30mm{\times}30mm{\times}8mm$ cavity made of an acrylic glass 10mm, with two isothermal copper walls kept at a prescribed temperature. The experimental results agreed very well with the numerical results. It was found that the flow consisted of a large double convection cell at angle of inclination of $60^{\circ}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.67-67
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• 2003

자동차, 항공기, 산업기계, 운반기계, 철도차량, 공작기계 등 거의 모든 산업부문에서 사용되는 베벨기어의 냉간단조 공정 및 금형 설계를 위한 해석을 수행하였다. 소성가공에 의해 생산된 베벨기어는 기계적 성질이 우수하여 동력 전달장치의 수명연장 및 신뢰성, 소형화 등을 달성할 수 있으며 생산 원가 절감의 효과가 크기 때문에 냉간 단조의 공정설계는 매우 중요하다. 베벨기어의 단조에 대한 상계해석 결과는 금형 설계 시 프레스에 필요한 단조하중을 예측할 수 있으므로 프레스의 최적성형과 안전한 금형 설계를 도모할 수 있다. 따라서 본 연구에서는 베벨기어의 냉간 단조시의 내부 동적 가용속도 장을 제시하였고 단조하중, 금속유동 등을 계산하였다. 또한 강소성 유한요소해석을 동시에 수행하여 제시한 동적 가용속도장의 적절성을 비교 검토하였다. 본 연구의 결과는 베벨기어의 적절한 냉간 단조 성형공정 및 공정설계를 위한 기초자료로 활용될 수 있을 것이다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.124-127
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• 2002

Ceil embolisation technique has been used to treat the intracranial aneurysms. Microcoils inserted into the aneurysm sac induce the blood flow stagnation inside the aneurysm sac, which causes the thrombus formation and embolisation of aneurysm. Since the intraaneurysmal flow patterns affect the embolisation process, we want to measure the flow field for different locations of coil inside the aneurysm sac . Lateral aneurysm models are manufactured using rapid prototyping, and the velocity fields are measured using particle image velocitimeter. Distally blocked models showed less flow into the aneurysm sac comparing to proximally blocked models. Also blocking the neck of aneurysm showed better inflow blocking comparing to blocking the dome of aneurysm. These results suggest that distal neck should be the preferred locations of coil for aneurysm embolisation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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• pp.349-355
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• 2011

In this study, numerical simulation has been conducted to investigate dispersion of a pollutant released from a new furniture, a kind of Sick Building Syndrome (SBS). A sofa which generates formaldehyde is implemented by using an immersed boundary method. Large Eddy Simulation (LES) is employed to obtain time-dependent velocity and concentration fields. It is shown that the ventilation efficiency in this room can be improved by changing inlet angle of diffuser, even though other conditions still remain unchanged. Both active diffusion near a sofa and air flow pattern are important parameters to enhance the ventilation efficiency.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.1-7
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• 2003

A common feature in the three-dimensional numerical model experiments of coastal discharge with simplifed model and idealized external forcings is investigated. The velocity fields due to the buoyancy and flow flux, are spreaded radiately and the surface velocites are much greater than homegeneous discharges. The coastal dischargd due to the Coriolis force and flow flux are shaped a anticyclical gyre (clockwise) and determined the scale of the gyre in the coastal zone, respectively. The bottom topography restricts a outward extention of the coastal fronts and it accelerates a southward flow.