• Proceedings of the Membrane Society of Korea Conference
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• 1991.04a
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• pp.13-14
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• 1991

본 연구에서는 Tobler[1]가 십자흐름여과 (crossflow filtration)의 개선책으로 제안한 동역학적 여과기를 제작하여 그 특성을 실험적으로 고찰하였다. 이 여과기는 두 개의 동심원통 사이를 유체가 흐를 때 내부원통의 회전속도가 외부원통의 회전속도보다 매우 빠를 경우 발생하는 Taylor 와류를 응용한 것이다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1633-1639
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• 1993

In spark ignition engine, EGR of lean mixture operation has advantage in emission, but disadvantages in power output and combustion flame propagation. Fast burn system is known to be a useful method to solve these disadvantages. This paper presents the characteristics of in-cylinder flow for different combustion chamber geometries, and the correlation between the in-cylinder flow and the combustion flame speed using an ion current method.

• Journal of Industrial Technology
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• v.20 no.B
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• pp.77-86
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• 2000

In order to observe the pattern forming of copper plate and chemical corrosion reaction, a study on the effect of the process parameters on the formation of micro-pattern by a photochemical etching of copper plate was carried out. The results are as follows : 1) Etching rate increases as the concentration of etchant increases under the regular condition of the temperature by the increasing of diffusion rate to surface. 2) Etching rate increases as the temperature of etchant increases by the fast acting of the material delivery of diffusion to surface under the regular condition of concentration. 3) It was found that etching speed increases as the material delivery of convection rising increased when the aeration speed of etchant increases. This result was from the fact acted by the material delivery of convection rising rather than material delivery of diffusion to the surface.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.21-26
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• 2007

This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometic effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.49-55
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• 2009

This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometric effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that the flow mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.395-398
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• 2010

감압비등에 의한 미립화는 더 미세한 직경의 액적을 얻을 수 있고, 분무각이 증가하며, 더 좋은 혼합특성을 갖는 다는 점에서 단순 압력식 미립화와 차이가 난다. 감압비등이란 과열된 액체를 포화 압력 이하의 대기 중으로 분사하여 급격한 비등에 의해 이루어지는 미립화이다. 본 연구는 금속 연료를 이용한 추진기관의 산화제인 물 공급기술에 감압비등과정을 이용한 와류분무를 적용시키기 위해 수행됐다. 분열길이와 같은 거시적 특성은 Charge-Couple Device(CCD) 카메라를 이용해 측정하였고, Sauter Mean Diameter(SMD)와 SMD분포와 같은 미시적 특성은 Global Sizing Velocimetry(GSV) 시스템을 이용해 측정했다. 실험은 압력과 온도, 대류 속도를 변화시키며 진행했다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.10
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• pp.843-852
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• 2016

The autorotative flight of maple seeds(Acer palmatum) is numerically simulated based on the 3D geometry and the motion parameters of real seeds. The nominal values of the motion parameters are 1.26 m/s for descent velocity, 133.6 rad/s (1,276 rpm) for spinning rate, $19.4^{\circ}$ for coning angle, and $-1.5^{\circ}$ for pitch angle. A compact leading-edge vortex (LEV) positioned at the inner span of the seed blade causes a large suction pressure on its leeward surface. The suction pressure peaks occur near the leading region of inner span sections. The flow pattern characterized by the prominent LEV and the values of aerodynamic force coefficients obtained in the present study are in good agreement with experimental data measured for a dynamically-scaled robot maple seeds. A spiraling vortex developed in the leeward region advances toward the seed tip and merges with the tip-passing flow, which is considered to be a mechanism of maintaining stable and attached LEV for the autorotating maple seeds.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.177-180
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• 2006

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.467-473
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• 2007

Flow visualization study to qualitatively define the flow field over a stealth UCAV(Uninhabited Combat Air Vehicle) configuration in a water tunnel has been conducted to clarify the basic aerodynamic performance. The test was performed at freestream velocity of 12.7 cm/sec which was corresponding to a Reynolds number of $1.4{\times}10^4$ based on mean aerodynamic chord. The development and breakdown of vortices illuminated by using dye were compared to the previous force and moment data. It was shown that the effect of the vortices generated by the main-body and junction are dominant in the low angle-of-attack region. However, in the high angle-of-attack region, the vortex generated by the fore-body mainly influenced the aerodynamic performance of the model.

• Journal of Aerospace System Engineering
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• v.14 no.3
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• pp.1-9
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• 2020

In this paper, the effects of the delta winglet vortex generator, the airfoil vortex generator and the guide vanes on the friction factor and the Colburn factor in the fin-tube flow were studied. The vortex generator and guide vane were non-dimensionalized based on the channel height and tube diameter, and locations were selected according to the authors' suggestions. The Reynolds number based on the inlet velocity and the tube diameter was selected in the range of 1400-8000. As a result, the friction factor resulted in a 4.7% decrease in guide vanes at the Reynolds number 8000 over the conventional fin-tube, and the Colburn factor resulted in a 33% increase in the delta winglet vortex generator at the Reynolds number 3800 over the conventional fin-tube.